Category Archives: Physics

Riding the Phantom Zephyr

1.  Background

When charged molecules in the air are subjected to an electric field, they are accelerated. When these charged molecules collide with neutral ones, they transfer part of their momentum, leading to air movement known as an “ionic wind.”  This basic process is shown in the following diagram, which depicts a strong electric field between a discharge electrode (left) and a ground electrode (right), and the motion of negative ions toward the ground electrode where they are collected.  The neutral molecules pass through the ground electrode and generate the thrust called the ionic wind.

This post summarizes work that has been done to develop ionic wind propulsion systems for aircraft.  The particular projects summarized are the following:

  • Major Alexander de Seversky’s Ionocraft vertical lifter (1964)
  • The Festo b-IONIC Airfish airship (2005)
  • NASA ionic wind study (2009)
  • The MIT electroaerodynamic (EAD) heaver-than-air, fixed wing aircraft (2018)

2.  Scale model of ion-propelled Ionocraft vertical takeoff lifter flew in 1964

Major Alexander de Seversky developed the design concept for a novel aircraft concept called the “Ionocraft,” which was capable of hovering or moving in any direction at high altitudes by means of ionic discharge. His design for the Ionocraft is described in US Patent 3,130,945, “Ionocraft,” dated 28 April 1964.  You can read this patent here: https://patents.google.com/patent/US3130945A/en

The operating principle of de Seversky’s Ionocraft propulsion system is depicted in the following graphic.

Ion propulsion scheme implemented in the de Seversky Ionocraft. 
Source: Popular Mechanics, August 1964

In 1964, de Seversky built a two-ounce (57 gram) Ionocraft scale model and demonstrated its ability to fly while powered from an external 90 watt power conversion system (30,000 volts at 3 mA), significantly higher that conventional aircraft and helicopters.  This translated into a power-to-weight ratio of about 0.96 hp/pound.  You can watch a short 1964 video of a scale model Ionocraft test flight here: 

Screenshot showing Ionocraft scale model in flight
Screenshot showing ionic wind downdraft under an Ionocraft scale model in flight

De Seversky’s Ionocraft and its test program are described in an article in the August 1964 Popular Mechanics magazine, which is available at the following link:  https://books.google.com/books?id=ROMDAAAAMBAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

Alexander de Seversky’s one-man Ionocraft concept.
Source: Popular Mechanics Archive, August 1964
Alexander de Seversky’s Ionocraft commuter concept.
Source: Popular Mechanics Archive, August 1964
1960s Soviet concept for a passenger carrying Ionocraft.
The Museum of Unnatural Mystery, http://www.unmuseum.org/

In the 1960s, engineers found that Ionocraft technology did not scale up well and they were unable to build a vehicle that could generate enough lift to carry the equipment needed to produce the electricity needed to drive it.

3.  The first free-flying ion-propelled aircraft flew in 2005: the Festo b-IONIC Airfish

The Festo b-IONIC Airfish airship was developed at the Technical University of Berlinwith guidance of the firm Festo AG & Co. KG.  This small, non-rigid airship is notable because, in 2005, it became the first aircraft to fly with a solid state propulsion system.  The neutrally-buoyant Airfish only flew indoors, in a controlled environment, at a very slow speed, but it flew.

Airfish. Source:  Festo AG & Co. KG

Some of the technical characteristics of the Airfish are listed below:

  • Length:  7.5 meters (24.6 ft)
  • Span: 3.0 meters (9.8 ft)
  • Shell diameter: 1.83 meters (6 ft)
  • Helium volume:  9.0 m3(318 ft3)
  • Total weight:  9.04 kg (19.9 lb)
  • Power source in tail: 12 x 1,500 mAh lithium-ion polymer cells (18 Ah total)
  • Power source per wing (two wings): 9 x 3,200 mAh lithium-ion polymer cells (28.8 Ah total)
  • High voltage: 20,000 to 30,000 volts
  • Buoyancy:  9.0 – 9.3 kg (19.8 – 20.5 lb)
  • Total thrust:  8 – 10 grams (0.018 – 0.022 pounds) 
  • Maximum velocity: 0.7 meters/sec (2.5 kph; 1.6 mph)

The b-IONIC Airfish employed two solid state propulsion systems, an electrostatic ionic jet and a plasma ray, which Festo describes as follows:

  • Electrostatic ionic jet:  “At the tail end Airfish uses the classic principle of an electrostatic ionic jet propulsion engine. High-voltage DC-fields (20-30 kV) along thin copper wires tear electrons away from air molecules. The positive ions thus created are then accelerated towards the negatively charged counter electrodes (ring-shaped aluminum foils) at high speeds (300-400 m/s), pulling along additional neutral air molecules. This creates an effective ion stream with speeds of up to 10 m/s.”
  • Plasma-ray:  “The side wings of Airfish are equipped with a new bionic plasma-ray propulsion system, which mimics the wing based stroke principle used by birds, such as penguins, without actually applying movable mechanical parts. As is the case with the natural role model, the plasma-ray system accelerates air in a wavelike pattern while it is moving across the wings.”
Airfish.  Source: Festo AG & Co. KG
Airfish.  Source: Festo AG & Co

The Festo b-IONIC Airfish demonstrated that a solid state propulsion system was possible.  The tests also demonstrated that the solid state propulsion systems also reduced drag, raising the intriguing possibility that it may be possible to significantly reduce drag if an entire vessel could be enclosed in a ionized plasma bubble.You’ll find more information on the Festo b-IONIC Airfish, its solid state propulsion system and implications for drag reduction in the the Festo brochure here: https://www.festo.com/net/SupportPortal/Files/344798/b_IONIC_Airfish_en.pdf

You can watch a 2005 short video on the Festo b-IONIC Airfish flight here:

4.  NASA ionic wind study – 2009

A corona discharge device generates an ionic wind, and thrust, when a high voltage corona discharge is struck between sharply pointed electrodes and larger radius ground electrodes.

In 2009, National Aeronautics & Space Administration (NASA) researchers Jack Wilson, Hugh Perkins and William Thompson conducted a study to examine whether the thrust of corona discharge systems could be scaled to values of interest for aircraft propulsion.  Their results are reported in report NASA/TM-2009-215822, which you’ll find at the following link: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100000021.pdf

Key points of the study included:

  • Different types of high voltage electrodes were tried, including wires, knife-edges, and arrays of pins. A pin array was found to be optimum. 
  • Parametric experiments, and theory, showed that the thrust per unit power could be raised from early values of 5 N/kW to values approaching 50 N/kW, but only by lowering the thrust produced, and raising the voltage applied. 
  • In addition to using DC voltage, pulsed excitation, with and without a DC bias, was examined. The results were inconclusive as to whether this was advantageous. 
  • It was concluded that the use of a corona discharge for aircraft propulsion did not seem very practical.”

5.  The first heavier-than-air, fixed-wing, ion-propelled aircraft flew in 2018

On 21 November 2018, MIT researchers reported successfully flying the world’s first heavier-than-air, fixed-wing, ion-propelled (electroaerodynamic, EAD) aircraft.  You can read the paper by Haofeng Xu, et al., “Flight of an aeroplane with solid-state propulsion,” on the Nature website here: https://www.nature.com/articles/s41586-018-0707-9

The design of the MIT EAD aircraft is shown below:

a, Computer-generated rendering of the EAD airplane. 
b, Photograph of actual EAD airplane (after multiple flight trials).

Some of the technical characteristics of this MIT aircraft are listed below:

  • Wingspan: 4.9 meters (16 ft)
  • Total weight: 2.45 kg (5.4 lb)
  • Power source: powered by 54 x 3.7 volt 150 mAh lithium-ion polymer cells (8.1 Ah total)
  • High voltage: 40,000 volts (+ 20,000 volts / – 20,000 volts)
  • Total thrust: 3.2 N, 326 grams (0.718 pounds) 
  • Maximum velocity: 4.8 meters/sec (17.3 kph; 10.7 mph)

In their paper, the MIT researchers reported:

  • “We performed ten flights with the full-scale experimental aircraft at the MIT Johnson Indoor Track…. Owing to the limited length of the indoor space (60 m), we used a bungeed launch system to accelerate the aircraft from stationary to a steady flight velocity of 5 meters/sec within 5 meters, and performed free flight in the remaining 55 meters of flight space. We also performed ten unpowered glides with the thrusters turned off, in which the airplane flew for less than 10 meters. We used cameras and a computer vision algorithm to track the aircraft position and determine the flight trajectory.”
  • “All flights gained height over the 8–9 second segment of steady flight, which covered a distance of 40–45 meters…. The average physical height gain of all flights was 0.47 meters…. However, for some of the flights, the aircraft velocity decreased during the flight. An adjustment for this loss of kinetic energy…. results in an energy equivalent height gain, which is the height gain that would have been achieved had the velocity remained constant. This was positive for seven of the ten flights, showing that better than steady-level flight had been achieved in those cases.”
  • “In this proof of concept for this method of propulsion, the realized thrust-to-power ratio was 5 N/kW1, which is of the order of conventional airplane propulsion methods such as the jet engine.”  Overall efficiency was estimated to be 2.56%.

The propulsion principles of the MIT EAD aircraft are explained in relation to the following diagram in the November 2018 article by Franck Plouraboué, “Flying With Ionic Wind,” which you can read on the Nature website at the following link:  https://www.nature.com/articles/d41586-018-07411-z

The following diagram and explanatory text are reproduced from that article.

  • In Figure a, above: …an electric field (not shown) is applied to the region surrounding a fine wire called the emitter (shown in cross-section). The field induces electron cascades, whereby free electrons collide with air molecules (not shown in the cascades) and consequently free up more electrons. This process produces charged air molecules in the vicinity of the emitter — a corona discharge. Depending on the electric field, negatively or positively charged molecules drift away (red arrows) from the emitter. These molecules collide with neutral air molecules, generating an ionic wind (black arrows). 
  • In Figure b, above: The aircraft uses a series of emitters and devices called collectors, the longitudinal directions of which are perpendicular to the ionic wind. The flow of charged air molecules occurs mainly along the directions (red arrows) joining emitters and collectors. Consequently, the ionic wind is accelerated (black arrows) predominantly in these regions. 

You can view a short video of the MIT EAD aircraft test flights here:  

6.  The future of ionic propulsion for aerospace applications.

If it can be successfully developed to much larger scales, ionic propulsion offers the potential for aircraft to fly in the atmosphere on a variety of practical missions using only ionized air for propulsion.  Using other ionized fluid media, ionic propulsion could develop into a means to fly directly from the surface of the earth into the vacuum of space and then operate in that environment.In 2006, the Technical University of Berlin’s Airfish project manager, Berkant Göksel, founded the firm Electrofluidsystems Ltd., which in 2012 was rebranded as IB Göksel Electrofluidsystems.  This firm presently is developing a new third generation of plasma-driven airships with highly reduced ozone and nitrogen oxide (NOx) emissions, magneto-plasma actuators for plasma flow control, and the company’s own blended wing type flying wing products.  You’ll find their website here:  https://www.electrofluidsystems.com

Source: Electrofluidsystems TU Berlin
Advanced plasma-driven aircraft concept. Source:  Electrofluidsystems TU Berlin

MIT researchers are developing designs for high-performance aircraft using ionic propulsion.  Theoretically, efficiency improves with speed, with an efficiency of 50% possible at a speed of about 1,000 kph (621 mph).  You can watch a short video on MIT work to develop a Star Trek-like ion drive aircraft here:  

7.  More reading on electrodynamic propulsion for aircraft

General

MIT electroaerodynamic aircraft

Ionocraft lifters

JASON and NRAC Contracts Cancelled by the Pentagon

JASON is an independent advisory panel of elite scientists that was created in 1960 to address a wide range of scientific and technical issues, primarily for the U.S. military. Originally, the JASON panel had about 20 members, known informally as Jasons, increasing to about 40 members by the 1970s.  JASON maintains its independence by requiring that new members be selected by its existing members rather than by external sponsors.  

JASON is a very controversial organization with a very low public profile.  For a good introduction to JASON, I recommend Ann Finkbeiner’s 2006 book, “The Jasons: The Secret History of Science’s Postwar Elite,”  which is available from Amazon and other booksellers. You can watch an hour-long video created by Microsoft Research with Ann Finkbeiner providing an excellent narrative overview (no Powerpoint slides) on JASON here:

https://www.youtube.com/watch?v=FV1TBiwdZeg

Ann Finkbeiner notes: “Working in secrecy to solve highly classified problems for the Department of Defense, CIA, and NSA is an elite group of scientific advisors who provide the government with analyses on defense and arms control and they call themselves JASON.  Named for the hero in Jason and the Argonauts, the group grew out of the Manhattan Project and counts as its members scientists such as Freeman Dyson and Murray Gell-Mann.  Of the roughly one hundred Jasons over time, 43 have been elected to the National Academy of Sciences, eight have won MacArthur awards, one a Field’s Medal, and 11 have won Nobel Prizes.  Its members have gathered every summer since 1960, working in absolute secrecy and with unparalleled freedom.  The Jasons’ work poses vital questions: what role should the government play in scientific research? At what point is the inventor accountable for the hazards of the invention?”

You’ll find a list of JASON research topics compiled on Wikipedia here:

https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/JASON_(advisory_group).html

Most of the resulting JASON reports are classified.  You’ll find a list of unclassified JASON reports (and links) on the Federation of American Scientists (FAS) website at the following link:

https://fas.org/irp/agency/dod/jason/

Since the late 1970s, the JASONs have been assigned tasks and been funded via Indefinite Delivery / Indefinite Quantity (IDIQ) contracts managed by MITRE Corporation.  The Office of the Secretary of Defense (OSD) issued MITRE’s most recent five-year IDIQ contract for managing JASON tasking and funding.   Task Orders are issued under the main IDIQ contract and the actual work is performed according to the individual task orders. The IDIQ contract structure broadly allows government agencies to commission a JASON study and fund it via a new task order.  MITRE’s IDIQ contract expired on 31 March 2019.  A follow-on IDIQ contract was in the works, but OSD cancelled that solicitation on short notice on 28 March 2019. 

On 10 April 2019, the article, “Pentagon Cancels Contract for JASON Advisory Panel,” written by Steven Aftergood, was posted on the FAS website at the following link:

https://fas.org/blogs/secrecy/2019/04/pentagon-jason/?utm_source=FAS+General&utm_campaign=495e653a5b-EMAIL_CAMPAIGN_2017_02_21_COPY_01&utm_medium=email&utm_term=0_56a7496199-495e653a5b-222204421

FAS speculated that, “The Pentagon move to cancel the JASON contract appears to be part of a larger trend by federal agencies to limit independent scientific and technical advice.”  This trend appears to include the Naval Research Advisory Committee (NRAC), which is the Navy counterpart to the Army Science Board and the Air Force Scientific Advisory Board. 

On 5 April 2019, Steve Aftergood reported that, “This week the U.S. Navy abruptly terminated its own scientific advisory group, depriving the service of a source of internal critique and evaluation. The Naval Research Advisory Committee (NRAC) was established by legislation in 1946 and provided science and technology advice to the Navy for the past 73 years. Now it’s gone.  The decision to disestablish the Committee was announced in a March 29 Federal Register notice.”  You can read this report on the FAS website here:

https://fas.org/blogs/secrecy/2019/04/nrac-terminated/?utm_source=FAS+General&utm_campaign=495e653a5b-EMAIL_CAMPAIGN_2017_02_21_COPY_01&utm_medium=email&utm_term=0_56a7496199-495e653a5b-222204421

You can get an understanding of NRAC’s advisory role by visiting their website, which is still online at the following link:

https://www.nrac.navy.mil

NRAC published reports from 1988 are available online here:

https://www.nrac.navy.mil/reports.asp

Efforts are underway on several fronts to attempt to restore funding for JASON and NRAC.  Hopefully funding can be restored and these independent advisory groups can continue providing important scientific and technical advice to the U.S. government.

Additional resources related to JASON:

  • Joel Shurkin, “True Genius: The Life and Work of Richard Garwin, the Most Influential Scientist You’ve Never Heard of,” Prometheus Books, 21 February 2017      

Lyncean link

At meeting #65 of the Lyncean Group in August 2011, the subject of our presentation was “Experience with the JASONs.”  See more at the following link: https://lynceans.org/talk-65-82411/

Update 28 June 2019:

In April 2019, the Department of Energy’s National Nuclear Security Administration (NNSA) agreed to issue a contract to provide funding for JASON through at least January 2020. An early report of this new NNSA sponsorship was in the article, “After Pentagon Ends Contract, Top-Secret Scientists Group Vows To Carry On,” on the NPR website at the following link:

https://www.npr.org/2019/04/25/717225118/after-pentagon-ends-contract-top-secret-scientists-group-vows-to-carry-on

On 28 June 2019, Ann Finkbeiner posted an article entitled, “Jason—a secretive group of Cold War science advisers—is fighting to survive in the 21st century,” on the Science website at the following link:

https://www.sciencemag.org/news/2019/06/jason-secretive-group-cold-war-science-advisers-fighting-survive-21st-century

“What happens when Jason’s contract with NNSA expires in 2020 is unclear. One possibility is yet another home within DOD: This month, the U.S. House of Representatives added a line to DOD’s preliminary budget directing the Office of the Under Secretary of Defense for Acquisition and Sustainment to pick up Jason’s contract.”

Standby for a New Round of Gravitational Wave Detection

Since late August 2017, the US LIGO 0bservatories in Washington and Louisiana and the European Gravitational Observatory (EGO), Virgo, in Italy, have been off-line for updating and testing.  These gravitational wave observatories were set to start Observing Run 3 (O3) on 1 April 2019 and conduct continuous observations for one year.  All three of these gravitational wave observatories have improved sensitivities and are capable of “seeing” a larger volume of the universe than in Observing Run 2 (O2).

Later in 2019, the Japanese gravitational wave observatory, KAGRA, is expected to come online for the first time and join O3.  By 2024, a new gravitational wave observatory in India is expected to join the worldwide network.

On the advent of this next gravitational wave detection cycle, here’s is a brief summary of the status of worldwide gravitational wave observatories.

Advanced LIGO 

The following upgrades were implemented at the two LIGO observatories since Observing Run 2 (O2) concluded in 2017:

  • Laser power has been doubled, increasing the detectors’ sensitivity to gravitational waves.
  • Upgrades were made to LIGO’s mirrors at both locations, with five of eight mirrors being swapped out for better-performing versions.
  • Upgrades have been implemented to reduce levels of quantum noise. Quantum noise occurs due to random fluctuations of photons, which can lead to uncertainty in the measurements and can mask faint gravitational wave signals. By employing a technique called quantum “squeezing” (vacuum squeezing), researchers can shift the uncertainty in the laser light photons around, making their amplitudes less certain and their phases, or timing, more certain. The timing of photons is what is crucial for LIGO’s ability to detect gravitational waves.  This technique initially was developed for gravitational wave detectors at the Australian National University, and matured and routinely used since 2010 at the GEO600 gravitational wave detector in Hannover, Germany,

In comparison to its capabilities in 2017 during O2, the twin LIGO detectors have a combined increase in sensitivity of about 40%, more than doubling the volume of the observable universe.

You’ll find more news and information on the LIGO website at the following link:

https://www.ligo.caltech.edu/news

GEO600 

GEO600 is a modest-size laser interferometric gravitational wave detector (600 meter / 1,969 foot arms) located near Hannover, Germany. It was designed and is operated by the Max Planck Institute for Gravitational Physics, along with partners in the United Kingdom.

In mid-2010, GEO600 became the first gravitational wave detector to employ quantum “squeezing” (vacuum squeezing) and has since been testing it under operating conditions using two lasers: its standard laser, and a “squeezed-light” laser that just adds a few entangled photons per second but significantly improves the sensitivity of GEO600.  In a May 2013 paper entitled, “First Long-Term Application of Squeezed States of Light in a Gravitational Wave Observatory,” researchers reported the following results of operational tests in 2011 and 2012.

“During this time, squeezed vacuum was applied for 90.2% (205.2 days total) of the time that science-quality data were acquired with GEO600. A sensitivity increase from squeezed vacuum application was observed broadband above 400 Hz. The time average of gain in sensitivity was 26% (2.0 dB), determined in the frequency band from 3.7 to 4.0 kHz. This corresponds to a factor of 2 increase in the observed volume of the Universe for sources in the kHz region (e.g., supernovae, magnetars).”

The installed GEO600 squeezer (in the foreground) inside the GEO600 clean room together with the vacuum tanks (in the background).  
Source: http://www.geo600.org/15581/1-High-Tech

While GEO600 has conducted observations in coordination with LIGO and Virgo, GEO600 has not reported detecting gravitational waves. At high frequencies GEO600 sensitivity is limited by the available laser power. At the low frequency end, the sensitivity is limited by seismic ground motion.

You’ll find more information on GEO600 at the following link:

http://www.geo600.org/3020/About-GEO600

Advanced Virgo, the European Gravitational Observatory (EGO)

At Virgo, the following upgrades were implemented since Observing Run 2 (O2) concluded in 2017:

  • The steel wires used during O2 observation campaign to suspend the four main mirrors of the interferometer have been replaced.  The 42 kg (92.6 pound) mirrors now are suspended with thin fused-silica (glass) fibers, which are expected to increase the sensitivity in the low-medium frequency region.  The mirrors in Advanced LIGO have been suspended by similar fused-silica fibers since those two observatories went online in 2015.
  • A more powerful laser source has been installed, which should improve sensitivity at high frequencies. 
  • Quantum “squeezing” has been implemented in collaboration with the Albert Einstein Institute in Hannover, Germany.  This should improve the sensitivity at high frequencies.
Virgo mirror suspension with fused-silica fibers.  
Source: EGO/Virgo Collaboration/Perciballi

In comparison to its capabilities in 2017 during O2, Virgo sensitivity has been improved by a factor of about 2, increasing the volume of the observable universe by a factor of about 8.

You’ll find more information on Virgo at the following link:

http://www.virgo-gw.eu

Japan’s KAGRA 

KAGRA is a cryogenically-cooled laser interferometer gravitational wave detector that is sited in a deep underground cavern in Kamioka, Japan.  This gravitational wave observatory is being developed by the Institute for Cosmic Ray Research (ICRR) of the University of Tokyo.  The project website is at the following link:

https://gwcenter.icrr.u-tokyo.ac.jp/en/

One leg of the KAGRA interferometer.  
Source: ICRR, University of Tokyo

The cryogenic mirror cooling system is intended to cool the mirror surfaces to about 20° Kelvin (–253° Celsius) to minimize the motion of molecules (jitter) on the mirror surface and improve measurement sensitivity.   KAGRA’s deep underground site is expected to be “quieter” than the LIGO and VIRGO sites, which are on the surface and have experienced effects from nearby vehicles, weather and some animals.

The focus of work in 2018 was on pre-operational testing and commissioning of various systems and equipment at the KAGRA observatory. In December 2018, the KAGRA Scientific Congress reported that, “If our schedule is kept, we expect to join (LIGO and VIRGO in) the latter half of O3…”   You can follow the latest news from the KAGRA team here:

https://gwcenter.icrr.u-tokyo.ac.jp/en/category/latestnews

LIGO-India

IndIGO, the Indian Initiative in Gravitational-wave Observations, describes itself as an initiative to set up advanced experimental facilities, with appropriate theoretical and computational support, for a multi-institutional Indian national project in gravitational wave astronomy.  The IndIGO website provides a good overview of the status of efforts to deploy a gravitational wave detector in India.  Here’s the link:

http://www.gw-indigo.org/tiki-index.php?page=Welcome

On 22 January 2019, T. V. Padma reported on the Naturewebsite that India’s government had given “in-principle” approval for a LIGO gravitational wave observatory to be built in the western India state of Maharashtra. 

“India’s Department of Atomic Energy and its Department of Science and Technology signed a memorandum of understanding with the US National Science Foundation for the LIGO project in March 2016. Under the agreement, the LIGO Laboratory — which is operated by the California Institute of Technology (Caltech) in Pasadena and the Massachusetts Institute of Technology (MIT) in Cambridge — will provide the hardware for a complete LIGO interferometer in India, technical data on its design, as well as training and assistance with installation and commissioning for the supporting infrastructure. India will provide the site, the vacuum system and other infrastructure required to house and operate the interferometer — as well as all labor, materials and supplies for installation.”

India’s LIGO observatory is expected to cost about US$177 million.  Full funding is expected in 2020 and the observatory currently is planned for completion in 2024.  India’s Inter-University Centre for Astronomy and Astrophysics (IUCAA), also in Maharashtra  state, will lead the project’s gravitational-wave science and the new detector’s data analysis.

For T. V. Padma’s complete article, refer to: 

https://www.nature.com/articles/d41586-019-00184-z.

Spatial resolution of gravitational wave events

Using only the two US LIGO detectors, it is not possible to localize the source of gravitational waves beyond a broad sweep through the sky.  On 1 August 2017, Virgo joined LIGO during the second Observation Run, O2. While the LIGO-Virgo three-detector network was operational for only three-and-a-half weeks, five gravitational wave events were observed.  As shown in the following figure, the spatial resolution of the source was greatly improved when a triple detection was made by the two LIGO observatories and Virgo. These events are labeled with the suffix “HLV”.  

Source:  http://www.virgo-gw.eu, 3 December 2018

The greatly reduced areas of the triple event localizations demonstrate the capabilities of the current global gravitational wave observatory network to resolve the source of a gravitational-wave detection.  The LIGO and Virgo Collaboration reports that it can send Open Public Alerts within five minutes of a gravitational wave detection.

With timely notification and more precise source location information, other land-based and space observatories can collaborate more rapidly and develop a comprehensive, multi-spectral (“multi-messenger”) view of the source of the gravitational waves.

When KAGRA and LIGO-India join the worldwide gravitational wave detection network, it is expected that source localizations will become 5 to 10 times more accurate than can be accomplished with just the LIGO and Virgo detectors.

For more background information on gravitational-wave detection, see the following Lyncean posts:

The Next Phase in the Hunt for New Superheavy Elements is About to Start

Background

On 24 January 2016, I posted the article, “Where in the Periodic Table Will We Put Element 119?”, which reviews the development of the modern periodic table of chemical elements since it was first formulated in 1869 by Russian chemist Dimitri Mendeleev, through the completion of Period 7 with the naming element 118 in 2016.  You can read this post here:

https://lynceans.org/all-posts/where-in-the-periodic-table-will-we-put-element-119/

2019 is the 150thanniversary of Dimitri Mendeleev’s periodic table of elements.  To commemorate this anniversary, the United Nations General Assembly and the United Nations Educational, Scientific and Cultural organization (UNESCO) have proclaimed 2019 as the International Year of the Periodic Table of Chemical Elements (IYPT). You’ll find more information on the IYPT here:

https://www.iypt2019.org

A brief animated “visualization” entitled “Setting the Table,”created by J. Yeston, N. Desai and E. Wang, provides a good overview of the history and configuration of the periodic table.  Check it out here:

http://vis.sciencemag.org/periodic-table/

The prospects for extending the periodic table beyond element 118 (into a new Period 8) is discussed in a short 2018 video from Science Magazine entitled “Where does the periodic table end?,”which you can view here:

https://www.sciencemag.org/news/2019/02/where-does-periodic-table-end?utm_campaign=news_weekly_2019-02-01&et_rid=215579562&et_cid=2632608

The next phase in the hunt for new superheavy elements is about to start in Russia 

Flerov Laboratory of Nuclear Reactions (FLNR) Joint Institute for Nuclear Research (JINR) in Dubna is the leading laboratory in Russia, and perhaps the world, in the search for superheavy elements.  The FLNR website is here:

http://flerovlab.jinr.ru/flnr/she_factory_no.html

FLNR is the home of several accelerators and other experimental setups for nuclear research, including the U400 accelerator, which has been the laboratory’s basic tool for the synthesis of new elements since being placed in operation in 1979.  You can take a virtual tour of U400 on the FLNR website.  

On 30 May 2012 the International Union of Pure and Applied Chemistry (IUPAC) honored the work done by FLNR when it approved the name Flerovium (Fl) for superheavy element 114.

Yuri Oganessian, the Scientific Leader of FLNR, has contributed greatly to extending the periodic table through the synthesis of new superheavy elements.  On 30 November 2016, IUPAC recognized his personal contributions by naming superheavy element 118 after him:  Oganesson (Og). 

Yuri Oganessian.  Source:  MAX AGUILERA HELLWEG / WWW.SCIENCEMAG.ORG
2017 Armenian postage stamp honoring Yuri Oganessian.  Source: FLNR JINR

FLNR has built a new $60 million accelerator facility, dubbed the Superheavy Element Factory (SHEF), which is expected to be capable of synthesizing elements beyond 118.  The SHEF building and the DC-280 cyclotron that will be used to synthesize superheavy elements are shown in the photos below.

The SHEF building, 14 Nov 2016. Source:  FLNR JINR
The completed DC-280 cyclotron, 26 December 2018.  Source:  FLNR JINR

The 2016 paper, “Status and perspectives of the Dubna superheavy element factory,”by S. Dmitriev, M. Itkis and Y. Oganessian, presents an overview of the DC-280 cyclotron design, including the following diagram showing the general arrangement of the major components.

Arrangement of the major components of the DC-280 cyclotron.  

You can read this 2016 paper here:

http://inspirehep.net/record/1502737/files/epjconf-NS160-08001.pdf

For insights into the processes for synthesizing superheavy elements, I recommend that you view the following March 2018 video in which FLNR Director Sergey Dmitriev describes the design of SHEF and the planned process of synthesizing superheavy elements 119 and 120.  This is a rather long (23 min) video, but I think it will be worth your time.

On 26 December 2018, the DC-280 cyclotron produced its first beam of accelerated heavy ions.  The hunt for new superheavy elements using DC-280 is scheduled to begin in the spring of 2019.

A good overview of FLNR, as it prepares to put its Superheavy Element Factory into operation, is available in the article by Sam Kean, entitled “A storied Russian lab is trying to push the periodic table past its limits—and uncover exotic new elements,” which was posted on 30 January 2019 on the Science Magazine website. You’ll find this article at the following link:

https://www.sciencemag.org/news/2019/01/storied-russian-lab-trying-push-periodic-table-past-its-limits-and-uncover-exotic-new?utm_campaign=news_weekly_2019-02-01&et_rid=215579562&et_cid=2632608

The next few years may yield exciting new discoveries of the first members of Period 8 of the periodic table.  I think Dimitri Mendeleev would be impressed.

Additional reading:

75th Anniversary of the Kurchatov Institute

The I. V. Kurchatov Institute of Atomic Energy in Moscow was founded 75 years ago, in 1943, and is named for its founder, Soviet nuclear physicist Igor Vasilyevich Kurchatov.  Until 1955, the Institute was a secret organization known only as “Laboratory No. 2 of the USSR Academy of Sciences.”  The initial focus of the Institute was the development of nuclear weapons.

Kurchatov Institute 75thanniversary on Russian commemorative postage stamp. https://en.wikipedia.org/

I. V. Kurchatov and the team of scientists and engineers at the Institute led or supported many important historical Soviet nuclear milestones, including: 

  • 25 December 1946: USSR’s F-1 (Physics-1) reactor achieved initial criticality at Kurchatov Institute.  This was the 1st reactor built and operated outside the US.
  • 10 June 1948: USSR’s 1st plutonium production reactor achieved initial criticality (Unit A at Chelyabinak-65). The reactor was designed under the leadership of N. A. Dollezhal.
  • 29 August 1949: USSR’s 1st nuclear device, First Lightning [aka RDS-1, Izdeliye 501 (device 501) and Joe 1], was detonated at the Semipalatinsk test site in what is now Kazakhstan.  This was the 1st nuclear test other than by the US.
  • 27 June 1954: World’s 1st nuclear power plant, AM-1 (aka APS-1), was commissioned and connected to the electrical grid, delivering power in Obninsk.  AM-1 was designed under the leadership of N. A. Dollezhal.
  • 22 November 1955: USSR’s 1st thermonuclear device (RDS-37, a two-stage device) was detonated at the Semipalatinsk test site.  This also was the world’s 1stair-dropped thermonuclear device.
  • 5 December 1957: USSR’s 1st nuclear-powered icebreaker, Lenin, was launched.  This also was the world’s 1st nuclear-powered surface ship.
  • 4 July 1958: USSR’s 1st  nuclear-powered submarine, Project 627 SSN K-3, Leninskiy Komsomol, made its 1st underway on nuclear power.
  • 1958: World’s 1st Tokamak, T-1, initial operation at Kurchatov Institute.
I. V. Kurchatov and F-1 reactor on Russian commemorative postage stamp. Source:  Wikimedia Commons

I. V. Kurchatov served as the Institute’s director until his death in 1960 and was awarded Hero of Socialist Labor three times and Order of Lenin five times during his lifetime.

After I. V. Kurchatov’s death in 1960, the noted academician Anatoly P. Aleksandrov was appointed as the director of the Institute and continued in that role until 1989.  Aleksandrov already had a key role at the Institute, having been appointed by Stalin in September 1952 as the scientific supervisor for developing the USSR’s first nuclear-powered submarine and its nuclear power unit.

A. P. Aleksandrov and OK-150 reactor on Russian commemorative postage stamp. Source:  Wikimedia Commons

Until 1991, the Soviet Ministry of Atomic Energy oversaw the administration of Kurchatov Institute.  After the formation of the Russian Federation at the end of 1991, the Institute became a State Scientific Center reporting directly to the Russian Government.  Today, the President of Kurchatov Institute is appointed by the Russian Prime Minister, based on recommendations from Rosatom (the Russian State Energy Corporation), which was formed in 2007.

You’ll find a comprehensive history of Kurchatov Institute in a 2013 (70thanniversary) special issue of the Russian version of Scientific American magazine, which you can download here:

 https://sciam.ru/download_issues/7/47.pdf

The evolution of Kurchatov Institute capabilities from its initial roles on the Soviet nuclear weapons program is shown in the following diagram.

Source: Special issue 2013, www.scientificrussia.ru

Modern roles for Kurchatov Institute are shown in the following graphic.

Source: Special issue 2013, www.scientificrussia.ru

In the past 75 years, the Kurchatov Institute has performed many major roles in the Soviet / Russian nuclear industry and, with a national security focus, continues to be a driving force in that industry sector.

Now, lets take a look at a few of the pioneering nuclear projects led or supported by Kurchatov Institute:

  • F-1 (Physics-1) reactor
  • Plutonium production reactors
  • Obninsk nuclear power plant AM-1
  • T-1 Tokamak

F-1 (Physics-1) reactor

The F-1 reactor designed by the Kurchatov Institute was a graphite-moderated, air-cooled, natural uranium fueled reactor with a spherical core about 19 feet (5.8 meters) in diameter. F-1 was the first reactor to be built and operated outside of the US.  It was a bit more compact than the first US reactor, the Chicago Pile, CP-1, which had an ellipsoidal core with a maximum diameter of about 24.2 feet (7.4 meters) and a height of 19 feet (5.8 meters).

The F-1 achieved initial criticality on 25 December 1946 and initially was operated at a power level of 10 watts.  Later, F-1 was able to operate at a maximum power level of 24 kW to support a wide range of research activities. In a 2006 report on the reactor’s 60thanniversary by RT News (www.rt.com), Oleg Vorontsov, Deputy Chief of the Nuclear Security Department reported, “Layers of lead as they are heated by uranium literally make F1 a self-controlling nuclear reactor. And the process inside is called – the safe-developing chain reaction of uranium depletion. If the temperature rises to 70 degrees Celsius (158° Fahrenheit), it slows down by its own! So it simply won’t let itself get out of control.” 

F-1 was never refueled prior to its permanent shutdown in November 2016, after 70 years of operation.

Top of the F-1 reactor core. Source: http://nuclearweaponarchive.org/
F-1 reactor facility cross-section diagram.  The F-1 reactor is the igloo-shaped structure located in the open pit.  Source: http://nuclearweaponarchive.org/
Graphite stacks of the F-1 reactor.  Source: Kurchatov Institute

Plutonium production reactors

The first generation of Soviet plutonium production reactors were graphite-moderated, natural uranium fueled reactors designed under the leadership of N.A. Dollezhal while he was at the Institute of Chemical Machinery in Moscow.  The Kurchatov Institute had a support role in the development of these reactors.The five early production reactors at Chelyabinsk-65 (later known as the Mayak Production Association) operated with a once-through primary cooling water system that discharged into open water ponds.

Simplified cross-section of a Russian graphite-moderated, water-cooled plutonium production reactor.  Source: PNL-9982

Four of the five later graphite-moderated production reactors at Tomsk had closed primary cooling systems that enabled them to also generate electric power and provide district heating (hot water) for the surrounding region.  You’ll find a good synopsis of the Soviet plutonium production reactors in the 2011 paper by Anatoli Diakov, “The History of Plutonium Production in Russia,” here:  

http://scienceandglobalsecurity.org/archive/sgs19diakov.pdf

Additional details on the design of the production reactors is contained in the 1994 Pacific Northwest Laboratory report PNL-9982, “Summary of Near-term Options for Russian Plutonium Production Reactors,” by Newman, Gesh, Love and Harms.  This report is available on the OSTI website here:   

https://www.osti.gov/servlets/purl/10173950

Obninsk nuclear power plant AM-1 (Atom Mirny or “Peaceful Atom”)

AM-1 nuclear power plant exterior view.  Source:  tass.ru
Panoramic view of the AM-1 power plant control room.  Source: www.chistoprudov.ru via https://reactor.space/news_en/

Obninsk was the site of the world’s first nuclear power plant (NPP).  This NPP had a single graphite-moderated, water-cooled reactor fueled with low-enriched uranium fuel. The reactor had a maximum power rating of 30 MWt.  AM-1 was designed by N.A. Dollezhal and the Research and Development Institute of Power Engineering (RDIPE / NIKIET) in Moscow, as an evolution of an earlier Dollezhal design of a small graphite-moderated reactor for ship propulsion.  The Kurchatov Institute had a support role in the development of AM-1.

The basic AM-1 reactor layout is shown in the following diagram.

Source: Directory of Nuclear Reactors, Vol. IV, Power Reactors, International Atomic Energy Agency, 1962

The closed-loop primary cooling system delivered heat via steam generators to the secondary-side steam system, which drove a steam turbine generator that delivered 5 MWe (net) to the external power grid.   Following is a basic process flow diagram for the reactor cooling loops.

Source: Directory of Nuclear Reactors, Vol. IV, Power Reactors, International Atomic Energy Agency, 1962

Construction on AM-1 broke ground on 31 December 1950 at the Physics and Power Engineering Institute (PEI) in Obninsk, about 110 km southwest of Moscow.  Other early milestone dates were:

  • Initial criticality:  5 May 1954
  • Commissioning and first grid connection:  26 June 1954
  • Commercial operation:  30 November 1954

In addition to its power generation role, AM-1 had 17 test loops installed in the reactor to support a variety of experimental studies. After 48 years of operation, AM-1 was permanently shutdown on 28 April 2002.

You can read more details on AM-1 in the following two articles: “Obninsk: Number One,” by Lev Kotchetkov on the Nuclear Engineering International website here:

 https://www.neimagazine.com/features/featureobninsk-number-one

“Anniversary at Obninsk: The First Commercial Nuclear Power Plant,” by Will Davis on the ANS Nuclear Café website here:

 http://ansnuclearcafe.org/2015/06/24/anniversary-at-obninsk-the-first-commercial-nuclear-power-plant/#sthash.4wTrQueH.vhtfLcPK.dpbs

The AM-1 nuclear power plant design was developed further by NIKIET into the much larger scale RBMK (Reaktor Bolshoy Moshchnosti Kanalnyy, “High Power Channel-type Reactor”) NPPs.  The four reactors at the Chernobyl NPP were RBMK-1000 reactors.

The T-1 Tokamak

Research on plasma confinement is a toroidal magnetic field began in Russia in 1951, leading to the construction of the first experimental toroidal magnetic confinement system, known as a tokamak, at Kurchatov Institute. T-1 began operation in 1958.  

T-1 Tokamak.  Source: https://www.iter.org/sci/BeyondITER

Early operation of T-1 and successive models revealed many problems that limited the plasma confinement capabilities of tokamaks.  Solving these problems led to a better understanding of plasma physics and significant improvements in the design of tokamak machines.  You’ll find a historical overview of early Soviet / Russian work on Tokamaks in a 2010 IAEA paper by V. P. Smirnov, ”Tokamak Foundation in USSR/Russia 1950–1990,” which you can read here:

 https://fire.pppl.gov/nf_50th_5_Smirnov.pdf

The basic tokamak design for magnetic plasma confinement has been widely implemented in many international fusion research machines, winning out over other magnetic confinement concepts, including the Stellarator machine championed in the US by Dr. Lyman Spitzer (see my 30 August 2017 post on Stellarators).  Major international tokamak projects include the Joint European Torus (JET) at the Culham Center for Fusion Energy in Oxfordshire, UK, the Tokamak Fusion Test Reactor (TFTR) at Princeton Plasma Physics Laboratory in the US, the JT-60 at the Japan Atomic Energy Agency’s Naka Fusion Institute, and most recently the International Thermonuclear Experimental Reactor (ITER) being built now at the Saclay Nuclear Center in southern France.


2018 Nobel Prize in Physics

On 2 October 2018, the Royal Swedish Academy of Sciences announced the winners of the 2018 Nobel Prize in Physics. Arthur Ashkin (US) shares this Nobel Prize with Gérard Mourou (France) and Donna Strickland (Canada) for their “groundbreaking inventions in the field of laser physics.”

Arthur Ashkin’s award was “for the optical tweezers and their application to biological systems.” This is a technique developed by Ashkin in the late 1960s (first published in 1970) using laser beam(s) to create a force trap that can be used to physically hold and move microscopic objects (from atoms and molecules to living cells).  The technique now is widely used in studying a variety of biological systems, with applications such as cell sorting and bio-molecular assay.

You’ll find a detailed briefing entitled, “Optical Tweezers – Working Principles and Applications,” here:

http://www.phys.sinica.edu.tw/TIGP-NANO/Course/2008_Fall/classnote/NBP_Optical%20Tweezers_Wen-Tau%20Juan.pdf

Arthur Ashkin. Source: laserfest.org

Arthur Ashkin is a researcher at Bell Laboratories in New Jersey.  At 96, he the oldest person to be awarded a Nobel Prize.

The award to Mourou and Strickland was “for their method of generating high-intensity, ultra-short optical pulses.” They developed a technique in the mid-1980s called “chirped pulse amplification” (CPA) that is used to produce very short duration laser pulses of very high intensity.  CPA is applied today in laser micromachining, surgery, medicine, and in fundamental science studies.

You’ll find a brief tutorial entitled, “Chirped-Pulse Amplification Ultrahigh peak power production from compact short-pulse laser systems,” here:

https://pdfs.semanticscholar.org/1c96/a800faaa341d9719a6ca3fbb7ccff9ff9419.pdf

  Gérard Mourou. Source: American Physical Society (APS).  Donna Strickland. Source: University of Waterloo

Gérard Mourou is the director of the Laboratoire d’Optique Appliquee at the ENSTA ParisTech (École nationale supérieure de techniques avancées).  He was Donna Strickland’s PhD advisor.

Donna Strickland is an associate professor in the Physics and Astronomy Department of the University of Waterloo, Canada (about 90 km west of Toronto).  She is the first female Physics laureate in 55 years. The preceding female Physics laureates were:

  • In 1963, Maria Goeppert-Mayer was recognized for her work on the structure of atomic nuclei (shared with J. Hans D. Jensen and Eugene Wigner).
  • In 1903, Marie Curie was recognized for her pioneering work on nuclear radiation phemomena (shared with Pierre Curie and Henri Becquerel).

You can read the press release from the Royal Swedish Academy of Sciences for the 2018 Nobel Prize in Physics here:

https://www.nobelprize.org/uploads/2018/10/press-physics2018.pdf

Congratulations to the 2018 Nobel Physics laureates!

Return of the Stellarator

Background

Dr. Lyman Spitzer invented the stellarator in 1951 and built several versions of this magnetic plasma confinement machine at Princeton University during the 1950s and 1960s, establishing the world famous Princeton Plasma Physics Laboratory (PPPL) in the process. Dr. Spitzer’s earliest Stellarators were figure-eight devices as shown in the following photo.

Example of an early stellarator at the 1958 Atoms for Peace Conference, Geneva

In these first-generation stellarators, field coils wrapped around the figure-eight vacuum vessel provided the basic plasma confinement field. The physical twist in the stellarator’s structure twisted the internal magnetic confinement field and cancelled the effects of plasma ion drift during each full circuit around the device. You can download Dr. Spitzer’s historic 1958 IAEA conference paper, “The Stellarator Concept,” at the following link:

http://www-naweb.iaea.org/napc/physics/2ndgenconf/data/Proceedings%201958/papers%20Vol32/Paper23_Vol32.pdf

The next generation of stellarators adopted a simpler torus shape and created the twist in the magnetic confinement field with helical field coils outside the vacuum vessel.

While stellarators achieved many important milestones in magnetic confinement, by the late 1960s, the attention of the fusion community was shifting toward a different type of magnetic confinement machine: the tokamak. Since then, this basic design concept has been employed in many of the world’s major fusion devices, including the Alcator-C Mod (MIT, USA), Doublet III-D (DIII-D at General Atomics, USA), Tokamak Fusion Test Reactor (TFTR at PPPL, USA), Joint European Torus (JET, UK), National Spherical Torus Experiment Upgrade (NSTX-U at PPPL, USA) and the International Thermonuclear Experimental Reactor (ITER, France).

Now, almost 50 years later, there is significant renewed interest in stellarators. The newest device, the Wendelstein 7-X stellarator, became operational in 2016. It may help determine if modern technology has succeeded in making the stellarator a more promising path to fusion power than the tokamak.

Comparison of Tokamaks and Stellarators

Modern tokamaks and stellarators both implement plasma confinement within a (more or less) toroidal vacuum vessel that operates at very high vacuum conditions, on the order of 10-7 torr. Both types of machines use the combined effects of two or more magnetic fields to create and control helical field lines (HFL) that enable plasma confinement and reduce particle drift in the circulating plasma.

In the following description, the simple “classical” tokamak configuration shown below will be the point of reference.

Source: Hans-Jürgen Hartfuß, Thomas Geist, “Fusion Plasma Diagnostics With mm-Waves: An Introduction”

The main features of a tokamak are summarized below.

  • The vacuum vessel in a modern tokamak typically is an azimuthally-symmetric torus of revolution (donut-shaped), typically with a vertically elongated, D-shaped cross section. Modern “spherical” tokomaks maintain the D-shaped cross section, but minimize the diameter of the hole in the center of the torus.
  • Plasma confinement within the vacuum vessel is accomplished by the combined effects of a toroidal magnetic field and an induced poloidal magnetic field. Together, these fields create the helical field lines for plasma confinement. In the following diagram, the toroidal field is represented by the blue arrow and the poloidal field is represented by the red arrow.

By Dave Burke – Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=1169843

  • The toroidal field (blue) is generated by a set of external toroidal field coils (TFCs) that surround the vacuum vessel.
  • The poloidal field (red) is generated by a strong induced plasma current (Iplasma), on the order of 106 amperes, flowing within the plasma inside the vacuum vessel. An external coil in the center of the tokamak serves as the primary coil of a transformer and the circulating plasma serves as the secondary coil of the transformer. To create the poloidal field, the transformer primary coil is charged at a controlled rate (i.e. to yield the desired rate of flux increase), thereby inducing a current in the plasma and heating the plasma by ohmic heating. When the primary coil reaches maximum flux, current is no longer induced in the plasma and the tokamak “pulse” is over.
  • A pair of vertical field coils (VFC), one above and one below the plane of the torus, provide the ability to radially position the plasma within the vacuum vessel.
  • Divertors inside the vacuum vessel define the maximum extent of the magnetically confined plasma, remove impurities from the edge of the plasma, and help minimize plasma-wall interactions.
  • The high current in the plasma can falter unexpectedly, resulting in a “disruption”, which is a sudden losses of plasma confinement that can unleash magnetic forces powerful enough to damage the machine.
  • A tokamak is mechanically simpler than a stellarator.
  • The physics characteristics of a tokamak typically yield better confinement capabilities than a stellarator.
  • While the “pulse” in a modern tokamak can last several tens of minutes, a pulsed mode of operation may not be suitable for a commercial fusion reactor.
  • Pulsed magnetic and thermal loads create mechanical fatigue issues that must be accommodated in the design of tokamak structures.

The simple “classical” stellarator configuration shown below will be the point of reference for the following discussion.

Source: Hans-Jürgen Hartfuß, Thomas Geist, “Fusion Plasma Diagnostics With mm-Waves: An Introduction”

The main features of a stellarator are summarized below.

  • There are many variants of devices called stellarators, with names such as Torsatron, Heliotron, Heliac, and Helias. All create the plasma confinement field with external magnet systems in various configurations and none depend on the existence of a toroidal plasma current.
  • In the classical stellarator in the above diagram, the plasma confinement field is created by a set of planar (flat) TFCs and external pairs (1, 2 or 3) of twisting helical field coils (HFC) with opposite currents in each conductor in the pair.
  • A stellarator is mechanically more complex and more difficult to manufacture than a tokamak.
  • Stellarators may use a divertor or a simpler “limiter” to define the outer extent of the plasma.
  • While a stellarator has no induced plasma current, other small currents, known as “pressure-driven” or “bootstrap” currents, exist. These small currents do not cause plasma disruptions as may occur in a tokamak, but complicate plasma confinement.
  • A stellarator is intrinsically capable of steady-state operation.
  • For a variety of reasons, a classical stellarator tends to lose energy at a higher rate than a tokamak. Advanced, modular stellarators are making progress in improving confinement performance.

You’ll find more comparative information in the July 2016 paper by Y. XU, “A general comparison between tokamak and stellarator plasmas,” which is available at the following link:

http://ac.els-cdn.com/S2468080X16300322/1-s2.0-S2468080X16300322-main.pdf?_tid=7d9ff748-c680-11e6-9909-00000aacb35d&acdnat=1482216764_912e05c8d6b4957207a2e7ae31c30f03

Modern stellarators

In the last two decades, dramatic improvements in computer power and 3-dimensional modeling capabilities have enabled researchers and designers to accurately model a stellarator’s complex magnetic fields, plasma behavior, and mechanical components (i.e., vacuum vessel, magnet systems and other structures). This has enabled implementation of a “plasma first” design process in which the initial design focus is on optimizing plasma equilibrium based on selected physics conditions. Key goals of this optimization process are to define plasma equilibrium conditions that reduce heat transport and particle loss from the plasma. As you might suspect, there are different technical bases for approaching the plasma optimization process. The stellarator’s magnet systems are designed to produce the confinement field needed for the specified, optimized plasma design.

This class of modern, optimized stellarators is characterized by complex, twisting plasma shapes and non-planar, modular toroidal coils that are individually designed, built and assembled. The net result is a stellarator with significantly better confinement performance that earlier stellarator designs. In this post, we’ll look in more detail at the following three advanced stellarators:

  • Wendelstein 7-AS [Max Planck Institute for Plasma Physics (IPP), Garching, Germany]
  • Helically Symmetric eXperiment (HSX, University of Wisconsin – Madison, USA)
  • Wendelstein 7-X [Max Planck Institute for Plasma Physics (IPP), Griefswald, Germany]

 Wendelstein 7-AS Stellarator (1988 – 2002)

The Wendelstein 7-AS was the first modular, advanced stellarator and was the first stellarator equipped with a divertor. It was used to test and validate basic elements of stellarator optimization.  Basic physical parameters of 7-AS are:

  • Major radius 2 m
  • Minor radius 0.2 m
  • Magnetic field 2.5 – 3 T

The physical layout and scale of the 7-AS machine is shown in the first diagram, below, with more details on the magnet system in the following diagram.

Above & below: Wendelstein 7-AS. Source: Max Planck IPP, I. Weber

The 7-AS operated from 1988 to 2002.   The IPP reported the following results:

  • Demonstrated that the innovative modular magnet coil system can be manufactured to exacting specifications.
  • Demonstrated improved plasma equilibrium and transport behavior because of the improved magnetic field structure.
  • Confirmed the effectiveness of the optimization criteria.
  • Demonstrated the effectiveness of a divertor on a stellarator (a common feature in tokamaks).

You’ll find more details on the 7-AS on the IPP website at the following link:

http://www.ipp.mpg.de/2665443/w7as?page=1

Its successor is the Wendelstein 7-X.

Helically Symmetric eXperiment (HSX)

HSX is a small modular coil advanced stellarator that began operation in 1999 at the Electrical and Computer Engineering Department at the University of Wisconsin-Madison. HSX basic design parameters are:

  • Major radius 1.2 m
  • Minor radius 0.15 m
  • Magnetic field 1T

The physical arrangement of HSX is shown in the following diagram.

HSX physical configuration. Source: University of Wisconsin – Madison

The HSX was the first stellarator to be optimized to deliver a “quasi-symmetric” magnetic field. While the magnetic field strength is usually a two-dimensional function on the magnetic surfaces traced out by the field lines, quasi-symmetry is achieved by making it one-dimensional in so-called “magnetic coordinates” (Boozer coordinates).

Author Masayuki Yokoyama’s paper, “Quasi-symmetry Concepts in Helical Systems,” provides a description of quasi-symmetry.

“A key point of quasi-symmetry is that the drift trajectories of charged particles depend on the absolute value of the magnetic field (B) expressed in terms of magnetic field coordinates (Boozer coordinates). The plasma can be optimized in terms of the Boozer coordinates instead of the vector components of the field.”

You can read Yokoyama’s complete paper at the following link:

https://www.jstage.jst.go.jp/article/jspf/78/3/78_3_205/_pdf

The HSX main magnetic field is generated by a set of 48 non-planar, modular coils, arranged in four field periods, yielding the twisting flux shape shown below.


HSX plasma configuration. Source: University of Wisconsin – Madison

The HSX team reported that “this is the first demonstration that quasi-symmetry works, and you can actually measure the reduction in transport that you get.”

The home page for this project is at the following link:

http://www.hsx.wisc.edu

You can download a description of the HSX here:

http://www.hsx.wisc.edu/wp-uploads/2016/04/A-helically-symmetric-stellarator-HSX_Almagri_Anderson-DT_Anderson-FSB_Probert_Shohet_Talmadge_1999.pdf

 Wendelstein 7-X Stellarator

The Wendelstein 7-X is a Helias (helical advanced stellarator) and is the first large-scale optimized stellarator; significantly larger than Wendelstein 7-S and HSX. The complete 7-X machine weighs about 750 tons, with about 425 tons operating under cryogenic conditions. The superconducting magnet system is designed for steady-state, high-power operation; nominally 30 minutes of plasma operation at 10 MW power. 7-X basic design parameters are:

  • Major radius 5.5m
  • Minor radius 0.52m
  • Magnetic field 2.5 T (up to 3T)

The IPP home page for this project is here:

http://www.ipp.mpg.de/w7x

The 7-X is drift optimized for improved thermal and fast ion confinement by: (a) implementing quasi-symmetry to reduce transport losses, (b) minimizing plasma currents (Pfirsch-Schluter & bootstrap currents) to improve equilibrium, and (c) designing a large magnetic well in the plasma cross-section to avoid plasma pressure instabilities.

The primary purpose of the Wendelstein 7-X is to investigate the new stellarator’s suitability for extrapolation to a fusion power plant design. The IPP website provides the following clarification:

“It is expected that plasma equilibrium and confinement will be of a quality comparable to that of a tokamak of the same size. But it will avoid the disadvantages of a large current flowing in a tokamak plasma: With plasma discharges lasting up to 30 minutes, Wendelstein 7-X is to demonstrate the essential stellarator property, viz. continuous operation.”

The main assembly of Wendelstein 7-X was completed in 2014. An IPP presentation on the manufacturing and assembly of 7-X is at the following link:

https://www.iter.org/doc/www/content/com/Lists/Stories/Attachments/680/ITER_W7X.pdf

You’ll also find a good video, “Wendelstein 7-X — from concept to reality,” which provides an overview of the design and construction of the 7-X stellarator and the associated research facility, at the following link:

https://www.youtube.com/watch?v=lyqt6u5_sHA

After engineering tests, the first plasma was produced at 7-X on 10 December 2015. A November 2016 article in Nature summarized on the results of initial operation of 7-X.  The article, entitled, “Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000,” confirmed that the 7-X is producing the intended confinement field. This article includes the following 3-D rendering and description of the complex magnetic coil sets that establish the twisting plasma confinement fields in the 7-X.

“Some representative nested magnetic surfaces are shown in different colors in this computer-aided design (CAD) rendering, together with a magnetic field line that lies on the green surface. The coil sets that create the magnetic surfaces are also shown, planar coils in brown, non-planar coils in grey. Some coils are left out of the rendering, allowing for a view of the nested surfaces (left) and a Poincaré section of the shown surfaces (right). Four out of the five external trim coils are shown in yellow. The fifth coil, which is not shown, would appear at the front of the rendering.”

You can read the complete article at the following link:

http://www.nature.com/articles/ncomms13493

A more detailed mechanical view of the 7-X, with a scale (gold) human figure is shown in the following diagram:

Source: IPP presentation, “Stellarators difficult to build? The construction of Wendelstein 7-X”

The large scale of the 7-X vacuum vessel is even more apparent in the following photo.

Source: adapted from IPP by C. Bickel and A. Cuadra/Science

Current status is outlined in a February 2017 presentation by the 7-X team to the Fusion Energy Science Advisory Committee (FESAC), entitled “Recent results and near-term plans for Wendelstein 7-X,” which is available at the following link:

http://www.firefusionpower.org/FESAC_W7-X_Pedersen_02.2017.pdf

Conclusion

So the jury is still out on the ability of advanced stellarators to take the lead over tokamaks in the long, hard journey toward the goal of delivering usable power from a fusion machine. Hopefully, the advanced stellarators will move the fusion community closer to that goal.  No doubt, we still have a very long way to go before fusion power becomes a reality.

For more background information on stellarators:

A summary of Dr. Spitzer’s pioneering work at PPPL is documented in a presentation entitled, “Spitzer’s Pioneering Fusion Work and the Search for Improved Confinement,” which you can download at the following link:

http://w3.pppl.gov/~hammett/refs/2013/Spitzer_100th_Hammett_2013.pdf

There is a good briefing on the basics of stellarator design and operation in the following two documents:

Dudson, B., “Stellarators,” University of York, UK, 6 February 2014 at the following link:

http://www-users.york.ac.uk/~bd512/teaching/media/mcf_lecture_06.pdf

Beidler, C.D., et al., “Stellarator Fusion Reactors – an Overview”, Max-Planck Institute for Plasma Physics, 2001, at the following link:

http://fire.pppl.gov/itc12_wobig_paper.pdf

 

 

 

Preliminary Design of an Experimental World-Circling Spaceship

The title of this post also is the title of the first RAND report, SM-11827, which was issued on 5 May 1946 when Project RAND still was part of the Douglas Aircraft Company. The basic concept for an oxygen-alcohol fueled multi-stage world-circling spaceship is shown below.

Source: RAND

Source: RAND

Now, more than 70 years later, it’s very interesting to read this report to gain an appreciation of the state of the art of rocketry in the U.S. in 1946, which already was benefiting from German experience with the V-2 and other rocket programs during WW II.

RAND offers the following abstract for SM-11827:

“More than eleven years before the orbiting of Sputnik, history’s first artificial space satellite, Project RAND — then active within Douglas Aircraft Company’s Engineering Division — released its first report: Preliminary Design of an Experimental World-Circling Spaceship (SM-11827), May 2, 1946. Interest in the feasibility of space satellites had surfaced somewhat earlier in a Navy proposal for an interservice space program (March 1946). Major General Curtis E. LeMay, then Deputy Chief of the Air Staff for Research and Development, considered space operations to be an extension of air operations. He tasked Project RAND to undertake a feasibility study of its own with a three-week deadline. The resulting report arrived two days before a critical review of the subject with the Navy. The central argument turns on the feasibility of such a space vehicle from an engineering standpoint, but alongside the curves and tabulations are visionary statements, such as that by Louis Ridenour on the significance of satellites to man’s store of knowledge, and that of Francis Clauser on the possibility of man in space. But the most riveting observation, one that deserves an honored place in the Central Premonitions Registry, was made by one of the contributors, Jimmy Lipp (head of Project RAND’s Missile Division), in a follow-on paper nine months later: ‘Since mastery of the elements is a reliable index of material progress, the nation which first makes significant achievements in space travel will be acknowledged as the world leader in both military and scientific techniques. To visualize the impact on the world, one can imagine the consternation and admiration that would be felt here if the United States were to discover suddenly that some other nation had already put up a successful satellite.’”

You can buy the book from several on-line sellers or directly from RAND. However you also can download the complete report for free in three pdf files that you’ll find on the RAND website at the following link:

https://www.rand.org/pubs/special_memoranda/SM11827.html

 

 

First Ever Antimatter Spectroscopy in ALPHA-2

ALPHA-2 is a device at the European particle physics laboratory at CERN, in Meyrin, Switzerland used for collecting and analyzing antimatter, or more specifically, antihydrogen.  A common hydrogen atom is composed of an electron and proton.  In contrast, an  antihydrogen atom is made up of a positron bound to an antiproton.

Screen Shot 2016-12-22 at 4.19.01 PMSource: CERN

The ALPHA-2 project homepage is at the following link:

http://alpha.web.cern.ch

On 16 December 2016, the ALPHA-2 team reported the first ever optical spectroscopic observation of the 1S-2S (ground state – 1st excited state) transition of antihydrogen that had been trapped and excited by a laser.

“This is the first time a spectral line has been observed in antimatter. ……..This first result implies that the 1S-2S transition in hydrogen and antihydrogen are not too different, and the next steps are to measure the transition’s lineshape and increase the precision of the measurement.”

In the ALPHA-2 online news article, “Observation of the 1S-2S Transition in Trapped Antihydrogen Published in Nature,” you will find two short videos explaining how this experiment was conducted:

  • Antihydrogen formation and 1S-2S excitation in ALPHA
  • ALPHA first ever optical spectroscopy of a pure anti atom

These videos describe the process for creating antihydrogen within a magnetic trap (octupole & mirror coils) containing positrons and antiprotons. Selected screenshots from the first video are reproduced below to illustrate the process of creating and exciting antihydrogen and measuring the results.

Alpha2 mirror trap

The potentials along the trap are manipulated to allow the initially separated positron and antiproton populations to combine, interact and form antihydrogen.

Combining positron & antiproton 1Combining positron & antiproton 2Combining positron & antiproton 3

If the magnetic trap is turned off, the antihydrogen atoms will drift into the inner wall of the device and immediately be annihilated, releasing pions that are detected by the “annihilation detectors” surrounding the magnetic trap. This 3-layer detector provides a means for counting antihydrogen atoms.

Detecting antihydrogen

A tuned laser is used to excite the antihydrogen atoms in the magnetic trap from the 1S (ground) state to the 2S (first excited) state. The interaction of the laser with the antihydrogen atoms is determined by counting the number of free antiprotons annihilating after photo ionization (an excited antihydrogen atom loses its positron) and counting all remaining antihydrogen atoms. Two cases were investigated: (1) laser tuned for resonance of the 1S-2S transition, and (2) laser detuned, not at resonance frequency. The observed differences between these two cases confirmed that, “the on-resonance laser light is interacting with the antihydrogen atoms via their 1S-2S transition.”

Exciting antihydrogen

The ALPHA-2 team reported that the accuracy of the current antihydrogen measurement of the 1S-2S transition is about “a few parts in 10 billion” (1010). In comparison, this transition in common hydrogen has been measured to an accuracy of “a few parts in a thousand trillion” (1015).

For more information, see the 19 December 2016 article by Adrian Cho, “Deep probe of antimatter puts Einstein’s special relativity to the test,” which is posted on the Sciencemag.org website at the following link:

http://www.sciencemag.org/news/2016/12/deep-probe-antimatter-puts-einstein-s-special-relativity-test?utm_campaign=news_daily_2016-12-19&et_rid=215579562&et_cid=1062570

 

 

Emergent Gravity Theory Passes its First Test

In 2010, Prof. Erik Verlinde, University of Amsterdam, Delta Institute for Theoretical Physics, published the paper, “The Origin of Gravity and the Laws of Newton.” In this paper, the author concluded:

 “The results of this paper suggest gravity arises as an entropic force, once space and time themselves have emerged. If the gravity and space time can indeed be explained as emergent phenomena, this should have important implications for many areas in which gravity plays a central role. It would be especially interesting to investigate the consequences for cosmology. For instance, the way redshifts arise from entropy gradients could lead to many new insights.

The derivation of the Einstein equations presented in this paper is analogous to previous works, in particular [the 1995 paper by T. Jacobson, ‘Thermodynamics of space-time: The Einstein equation of state.’]. Also other authors have proposed that gravity has an entropic or thermodynamic origin, see for instance [the paper by T. Padmanabhan, ‘Thermodynamical Aspects of Gravity: New insights.’]. But we have added an important element that is new. Instead of only focusing on the equations that govern the gravitational field, we uncovered what is the origin of force and inertia in a context in which space is emerging. We identified a cause, a mechanism, for gravity. It is driven by differences in entropy, in whatever way defined, and a consequence of the statistical averaged random dynamics at the microscopic level. The reason why gravity has to keep track of energies as well as entropy differences is now clear. It has to, because this is what causes motion!”

You can download Prof. Verlinde’s 2010 paper at the following link:

https://arxiv.org/pdf/1001.0785.pdf

On 8 November 2016, Delta Institute announced that Prof. Verlinde had published a new research paper, “Emergent Gravity and the Dark Universe,” expanding on his previous work. You can read this announcement and see a short video by Prof. Verlinde on the Delta Institute website at the following link:

http://www.d-itp.nl/news/list/list/content/folder/press-releases/2016/11/new-theory-of-gravity-might-explain-dark-matter.html

You can download this new paper at the following link:

https://arxiv.org/abs/1611.02269

I found it helpful to start with Section 8, Discussion and Outlook, which is the closest you will find to a layman’s description of the theory.

On the Physics.org website, a short 8 November 2016 article, “New Theory of Gravity Might Explain Dark Matter,” provides a good synopsis of Verlinde’s emergent gravity theory:

“According to Verlinde, gravity is not a fundamental force of nature, but an emergent phenomenon. In the same way that temperature arises from the movement of microscopic particles, gravity emerges from the changes of fundamental bits of information, stored in the very structure of spacetime……

According to Erik Verlinde, there is no need to add a mysterious dark matter particle to the theory……Verlinde shows how his theory of gravity accurately predicts the velocities by which the stars rotate around the center of the Milky Way, as well as the motion of stars inside other galaxies.

One of the ingredients in Verlinde’s theory is an adaptation of the holographic principle, introduced by his tutor Gerard ‘t Hooft (Nobel Prize 1999, Utrecht University) and Leonard Susskind (Stanford University). According to the holographic principle, all the information in the entire universe can be described on a giant imaginary sphere around it. Verlinde now shows that this idea is not quite correct—part of the information in our universe is contained in space itself.

This extra information is required to describe that other dark component of the universe: Dark energy, which is believed to be responsible for the accelerated expansion of the universe. Investigating the effects of this additional information on ordinary matter, Verlinde comes to a stunning conclusion. Whereas ordinary gravity can be encoded using the information on the imaginary sphere around the universe, as he showed in his 2010 work, the result of the additional information in the bulk of space is a force that nicely matches that attributed to dark matter.”

Read the full Physics.org article at the following link:

http://phys.org/news/2016-11-theory-gravity-dark.html#jCp

On 12 December 2016, a team from Leiden Observatory in The Netherlands reported favorable results of the first test of the emergent gravity theory. Their paper, “First Test of Verlinde’s Theory of Emergent Gravity Using Weak Gravitational Lensing Measurements,” was published in the Monthly Notices of the Royal Astronomical Society. The complete paper is available at the following link:

http://mnras.oxfordjournals.org/content/early/2016/12/09/mnras.stw3192

An example of a gravitational lens is shown in the following diagram.

Gravitational-lensing-galaxyApril12_2010-1024x768-e1481555047928 Source: NASA, ESA & L. Calça

As seen from the Earth, the light from the galaxy at the left is bent by the gravitational forces of the galactic cluster in the center, much like light passing though an optical lens.

The Leiden Observatory authors reported:

“We find that the prediction from EG, despite requiring no free parameters, is in good agreement with the observed galaxy-galaxy lensing profiles in four different stellar mass bins. Although this performance is remarkable, this study is only a first step. Further advancements on both the theoretical framework and observational tests of EG are needed before it can be considered a fully developed and solidly tested theory.”

These are exciting times! As noted in the Physics.org article, “We might be standing on the brink of a new scientific revolution that will radically change our views on the very nature of space, time and gravity.”