Tag Archives: radiation

Materials that may protect astronauts from radiation in space

Sparing astronauts from harmful radiation  is one of the goals for this project according to a July 3, 2017 news item on Nanowerk (Note: A link has been removed),

Scientists at The Australian National University (ANU) have designed a new nano material that can reflect or transmit light on demand with temperature control, opening the door to technology that protects astronauts in space from harmful radiation (Advanced Functional Materials, “Reversible Thermal Tuning of All-Dielectric Metasurfaces”).

Lead researcher Dr Mohsen Rahmani from ANU said the material was so thin that hundreds of layers could fit on the tip of a needle and could be applied to any surface, including spacesuits.

The first speaker’s enthusiasm leaps off the screen,

For whose who prefer to read their news, a July 4, 2017 ANU press release, which originated the news item, provides more detail,

“Our invention has a lot of potential applications, such as protecting astronauts or satellites with an ultra-thin film that can be adjusted to reflect various dangerous ultraviolet or infrared radiation in different environments,” said Dr Rahmani, an Australian Research Council (ARC) Discovery Early Career Research Fellow at the Nonlinear Physics Centre within the ANU Research School of Physics and Engineering.

“Our technology significantly increases the resistance threshold against harmful radiation compared to today’s technologies, which rely on absorbing radiation with thick filters.”

Co-researcher Associate Professor Andrey Miroshnichenko said the invention could be tailored for other light spectrums including visible light, which opened up a whole array of innovations, including architectural and energy saving applications.

“For instance, you could have a window that can turn into a mirror in a bathroom on demand, or control the amount of light passing through your house windows in different seasons,” said Dr Miroshnichenko from the Nonlinear Physics Centre within the ANU Research School of Physics and Engineering.

“What I love about this invention is that the design involved different research disciplines including physics, materials science and engineering.”

Co-lead researcher Dr Lei Xu said achieving cost-efficient and confined temperature control such as local heating was feasible.

“Much like your car has a series of parallel resistive wires on the back windscreen to defog the rear view, a similar arrangement could be used with our invention to confine the temperature control to a precise location,” said Dr Xu from the Nonlinear Physics Centre within the ANU Research School of Physics and Engineering.

The innovation builds on more than 15 years of research supported by the ARC through CUDOS, a Centre of Excellence, and the Australian National Fabrication Facility.

Here’s a link to and a citation for the paper,

Reversible Thermal Tuning of All-Dielectric Metasurfaces by Mohsen Rahmani, Lei Xu, Andrey E. Miroshnichenko, Andrei Komar, Rocio Camacho-Morales, Haitao Chen, Yair Zárate, Sergey Kruk, Guoquan Zhang, Dragomir N. Neshev, and Yuri S. Kivshar. Advanced Functional Materials DOI: 10.1002/adfm.201700580 Version of Record online: 3 JUL 2017

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Figuring out how stars are born by watching neutrons ‘quantum tunnelling’ on graphene

A Feb. 3, 2017 news item on Nanowerk announces research that could help us better understand how stars are ‘born’,

Graphene is known as the world’s thinnest material due to its 2D structure, where each sheet is only one carbon atom thick, allowing each atom to engage in a chemical reaction from two sides. Graphene flakes can have a very large proportion of edge atoms, all of which have a particular chemical reactivity.

In addition, chemically active voids created by missing atoms are a surface defect of graphene sheets. These structural defects and edges play a vital role in carbon chemistry and physics, as they alter the chemical reactivity of graphene. In fact, chemical reactions have repeatedly been shown to be favoured at these defect sites.

Interstellar molecular clouds are predominantly composed of hydrogen in molecular form (H2), but also contain a small percentage of dust particles mostly in the form of carbon nanostructures, called polyaromatic hydrocarbons (PAH). These clouds are often referred to as ‘star nurseries’ as their low temperature and high density allows gravity to locally condense matter in such a way that it initiates H fusion, the nuclear reaction at the heart of each star.

Graphene-based materials, prepared from the exfoliation of graphite oxide, are used as a model of interstellar carbon dust as they contain a relatively large amount of atomic defects, either at their edges or on their surface. These defects are thought to sustain the Eley-Rideal chemical reaction, which recombines two H atoms into one H2 molecule. The observation of interstellar clouds in inhospitable regions of space, including in the direct proximity of giant stars, poses the question of the origin of the stability of hydrogen in the molecular form (H2).

This question stands because the clouds are constantly being washed out by intense radiation, hence cracking the hydrogen molecules into atoms. Astrochemists suggest that the chemical mechanism responsible for the recombination of atomic H into molecular H2 is catalysed by carbon flakes in interstellar clouds.

A Feb. 2, 2017 Institut Laue-Langevin press release, which originated the news item, provides more insight into the research,

Their [astrochemists’s] theories are challenged by the need for a very efficient surface chemistry scenario to explain the observed equilibrium between dissociation and recombination. They had to introduce highly reactive sites into their models so that the capture of an atomic H nearby occurs without fail. These sites, in the form of atomic defects at the surface or edge of the carbon flakes, should be such that the C-H bond formed thereafter allows the H atom to be released easily to recombine with another H atom flying nearby.

A collaboration between the Institut Laue-Langevin (ILL), France, the University of Parma, Italy, and the ISIS Neutron and Muon Source, UK, combined neutron spectroscopy with density functional theory (DFT) molecular dynamics simulations in order to characterise the local environment and vibrations of hydrogen atoms chemically bonded at the surface of substantially defected graphene flakes. Additional analyses were carried out using muon spectroscopy (muSR) and nuclear magnetic resonance (NMR). As availability of the samples is very low, these highly specific techniques were necessary to study the samples; neutron spectroscopy is highly sensitive to hydrogen and allowed accurate data to be gathered at small concentrations.

For the first time ever, this study showed ‘quantum tunnelling’ in these systems, allowing the H atoms bound to C atoms to explore relatively long distances at temperatures as low as those in interstitial clouds. The process involves hydrogen ‘quantum hopping’ from one carbon atom to another in its direct vicinity, tunnelling through energy barriers which could not be overcome given the lack of heat in the interstellar cloud environment. This movement is sustained by the fluctuations of the graphene structure, which bring the H atom into unstable regions and catalyse the recombination process by allowing the release of the chemically bonded H atom. Therefore, it is believed that quantum tunnelling facilitates the reaction for the formation of molecular H2.

ILL scientist and carbon nanostructure specialist, Stéphane Rols says: “The question of how molecular hydrogen forms at the low temperatures in interstellar clouds has always been a driver in astrochemistry research. We’re proud to have combined spectroscopy expertise with the sensitivity of neutrons to identify the intriguing quantum tunnelling phenomenon as a possible mechanism behind the formation of H2; these observations are significant in furthering our understanding of the universe.”

Here’s a link to and a citation for the paper (which dates from Aug. 2016),

Hydrogen motions in defective graphene: the role of surface defects by Chiara Cavallari, Daniele Pontiroli, Mónica Jiménez-Ruiz, Mark Johnson, Matteo Aramini, Mattia Gaboardi, Stewart F. Parker, Mauro Riccó, and Stéphane Rols. Phys. Chem. Chem. Phys., 2016, Issue 36, 18, 24820-24824 DOI: 10.1039/C6CP04727K First published online 22 Aug 2016

This paper is behind a paywall.

Aliens wreak havoc on our personal electronics

The aliens in question are subatomic particles and the havoc they wreak is low-grade according to the scientist who was presenting on the topic at the AAAS (American Association for the Advancement of Science) 2017 Annual Meeting (Feb. 16 – 20, 2017) in Boston, Massachusetts. From a Feb. 17, 2017 news item on ScienceDaily,

You may not realize it but alien subatomic particles raining down from outer space are wreaking low-grade havoc on your smartphones, computers and other personal electronic devices.

When your computer crashes and you get the dreaded blue screen or your smartphone freezes and you have to go through the time-consuming process of a reset, most likely you blame the manufacturer: Microsoft or Apple or Samsung. In many instances, however, these operational failures may be caused by the impact of electrically charged particles generated by cosmic rays that originate outside the solar system.

“This is a really big problem, but it is mostly invisible to the public,” said Bharat Bhuva, professor of electrical engineering at Vanderbilt University, in a presentation on Friday, Feb. 17 at a session titled “Cloudy with a Chance of Solar Flares: Quantifying the Risk of Space Weather” at the annual meeting of the American Association for the Advancement of Science in Boston.

A Feb. 17, 2017 Vanderbilt University news release (also on EurekAlert), which originated the news item, expands on  the theme,

When cosmic rays traveling at fractions of the speed of light strike the Earth’s atmosphere they create cascades of secondary particles including energetic neutrons, muons, pions and alpha particles. Millions of these particles strike your body each second. Despite their numbers, this subatomic torrent is imperceptible and has no known harmful effects on living organisms. However, a fraction of these particles carry enough energy to interfere with the operation of microelectronic circuitry. When they interact with integrated circuits, they may alter individual bits of data stored in memory. This is called a single-event upset or SEU.

Since it is difficult to know when and where these particles will strike and they do not do any physical damage, the malfunctions they cause are very difficult to characterize. As a result, determining the prevalence of SEUs is not easy or straightforward. “When you have a single bit flip, it could have any number of causes. It could be a software bug or a hardware flaw, for example. The only way you can determine that it is a single-event upset is by eliminating all the other possible causes,” Bhuva explained.

There have been a number of incidents that illustrate how serious the problem can be, Bhuva reported. For example, in 2003 in the town of Schaerbeek, Belgium a bit flip in an electronic voting machine added 4,096 extra votes to one candidate. The error was only detected because it gave the candidate more votes than were possible and it was traced to a single bit flip in the machine’s register. In 2008, the avionics system of a Qantus passenger jet flying from Singapore to Perth appeared to suffer from a single-event upset that caused the autopilot to disengage. As a result, the aircraft dove 690 feet in only 23 seconds, injuring about a third of the passengers seriously enough to cause the aircraft to divert to the nearest airstrip. In addition, there have been a number of unexplained glitches in airline computers – some of which experts feel must have been caused by SEUs – that have resulted in cancellation of hundreds of flights resulting in significant economic losses.

An analysis of SEU failure rates for consumer electronic devices performed by Ritesh Mastipuram and Edwin Wee at Cypress Semiconductor on a previous generation of technology shows how prevalent the problem may be. Their results were published in 2004 in Electronic Design News and provided the following estimates:

  • A simple cell phone with 500 kilobytes of memory should only have one potential error every 28 years.
  • A router farm like those used by Internet providers with only 25 gigabytes of memory may experience one potential networking error that interrupts their operation every 17 hours.
  • A person flying in an airplane at 35,000 feet (where radiation levels are considerably higher than they are at sea level) who is working on a laptop with 500 kilobytes of memory may experience one potential error every five hours.

Bhuva is a member of Vanderbilt’s Radiation Effects Research Group, which was established in 1987 and is the largest academic program in the United States that studies the effects of radiation on electronic systems. The group’s primary focus was on military and space applications. Since 2001, the group has also been analyzing radiation effects on consumer electronics in the terrestrial environment. They have studied this phenomenon in the last eight generations of computer chip technology, including the current generation that uses 3D transistors (known as FinFET) that are only 16 nanometers in size. The 16-nanometer study was funded by a group of top microelectronics companies, including Altera, ARM, AMD, Broadcom, Cisco Systems, Marvell, MediaTek, Renesas, Qualcomm, Synopsys, and TSMC

“The semiconductor manufacturers are very concerned about this problem because it is getting more serious as the size of the transistors in computer chips shrink and the power and capacity of our digital systems increase,” Bhuva said. “In addition, microelectronic circuits are everywhere and our society is becoming increasingly dependent on them.”

To determine the rate of SEUs in 16-nanometer chips, the Vanderbilt researchers took samples of the integrated circuits to the Irradiation of Chips and Electronics (ICE) House at Los Alamos National Laboratory. There they exposed them to a neutron beam and analyzed how many SEUs the chips experienced. Experts measure the failure rate of microelectronic circuits in a unit called a FIT, which stands for failure in time. One FIT is one failure per transistor in one billion hours of operation. That may seem infinitesimal but it adds up extremely quickly with billions of transistors in many of our devices and billions of electronic systems in use today (the number of smartphones alone is in the billions). Most electronic components have failure rates measured in 100’s and 1,000’s of FITs.

chart

Trends in single event upset failure rates at the individual transistor, integrated circuit and system or device level for the three most recent manufacturing technologies. (Bharat Bhuva, Radiation Effects Research Group, Vanderbilt University)

“Our study confirms that this is a serious and growing problem,” said Bhuva.“This did not come as a surprise. Through our research on radiation effects on electronic circuits developed for military and space applications, we have been anticipating such effects on electronic systems operating in the terrestrial environment.”

Although the details of the Vanderbilt studies are proprietary, Bhuva described the general trend that they have found in the last three generations of integrated circuit technology: 28-nanometer, 20-nanometer and 16-nanometer.

As transistor sizes have shrunk, they have required less and less electrical charge to represent a logical bit. So the likelihood that one bit will “flip” from 0 to 1 (or 1 to 0) when struck by an energetic particle has been increasing. This has been partially offset by the fact that as the transistors have gotten smaller they have become smaller targets so the rate at which they are struck has decreased.

More significantly, the current generation of 16-nanometer circuits have a 3D architecture that replaced the previous 2D architecture and has proven to be significantly less susceptible to SEUs. Although this improvement has been offset by the increase in the number of transistors in each chip, the failure rate at the chip level has also dropped slightly. However, the increase in the total number of transistors being used in new electronic systems has meant that the SEU failure rate at the device level has continued to rise.

Unfortunately, it is not practical to simply shield microelectronics from these energetic particles. For example, it would take more than 10 feet of concrete to keep a circuit from being zapped by energetic neutrons. However, there are ways to design computer chips to dramatically reduce their vulnerability.

For cases where reliability is absolutely critical, you can simply design the processors in triplicate and have them vote. Bhuva pointed out: “The probability that SEUs will occur in two of the circuits at the same time is vanishingly small. So if two circuits produce the same result it should be correct.” This is the approach that NASA used to maximize the reliability of spacecraft computer systems.

The good news, Bhuva said, is that the aviation, medical equipment, IT, transportation, communications, financial and power industries are all aware of the problem and are taking steps to address it. “It is only the consumer electronics sector that has been lagging behind in addressing this problem.”

The engineer’s bottom line: “This is a major problem for industry and engineers, but it isn’t something that members of the general public need to worry much about.”

That’s fascinating and I hope the consumer electronics industry catches up with this ‘alien invasion’ issue. Finally, the ‘bit flips’ made me think of the 1956 movie ‘Invasion of the Body Snatchers‘.

Did the Fantastic Four (comic book heroes) get their powers from radiation?

The American Chemical Society (ACS) has gone old school regarding how the Fantastic Four comic book characters got their powers, radiation. (The latest movie version offers an alternate explanation.)

Here’s more about radiation and the possibility of developing super powers as a consequence of exposure from the ACS video podcast series, Reactions,

From the Aug. 4, 2015 ACS news release on EurekAlert,

The Thing, Human Torch, Invisible Woman and Mister Fantastic are back this summer! In the new movie reboot, the team gets its powers while in an alternate dimension. Here at Reactions, though, we stick to comic-book canon. In this week’s video, we explain the original way the Fantastic Four got their power – radiation – with help from SciPop Talks. Check it out here: https://youtu.be/GbmSmgTIQ8s.

That’s all, folks!

Nanotwinned copper materials with nanovoids are damage-tolerant with regard to radiation

The research comes out of the Texas A&M University, from a May 29, 2015 news item on Azonano,

Material performance in extreme radiation environments is central to the design of future nuclear reactors. Radiation in metallic materials typically induces significant damage in the form of dislocation loops and continuous void growth, manifested as void swelling. In certain metallic materials with low-to-intermediate stacking fault energy, such as Cu [copper] and austenitic stainless steels, void swelling can be significant and lead to substantial degradation of mechanical properties.

By using in situ heavy ion irradiation in a transmission electron microscope (in collaboration with M.A. Kirk at IVEM facility at Argonne National Lab), Zhang’s [Xinghang Zhang] student, Dr. Youxing Chen, reported a surprising phenomena: during radiation of nanotwinned Cu, preexisting nanovoids disappeared.

A May 28, 2015 Texas A & M University news release, which originated the news item, expands on the theme,

The self-healing capability of Cu arises from the existence of three-dimensional coherent and incoherent twin boundary networks. Such a network enables capture and rapid transportation of radiation induced point defects and their clusters to nanovoids (as evidenced by in situ radiation experiments and molecular dynamics simulations performed in collaboration with Jian Wang at Los Alamos National Laboratory), and thus lead to the mutual elimination of defect clusters and nanovoids.

This study also introduces the concept that deliberate introduction of nanovoids in conjunction with nanotwins may enable unprecedented radiation tolerance in metallic materials. [emphasis mine] The mobile twin boundaries are swift carriers that load and transfer “customers” (defect clusters), and nanovoids are also necessary to accommodate these “customers.” The in situ radiation study also shows that after annihilation of nanovoids, the self-healing capability of nanotwinned Cu is degraded, highlighting the significance of nanovoids. The concept developed from this study, the combination of nanovoids with nanotwin networks, may also stimulate the design of damage tolerant materials in general that are subjected other extreme environments, such as high stress and high pressure impact.

Here’s a link to and a citation for the paper,

Damage-tolerant nanotwinned metals with nanovoids under radiation environments by Y. Chen, K Y. Yu, Y. Liu, S. Shao, H. Wang, M. A. Kirk, J. Wang, & X. Zhang. Nature Communications 6, Article number: 7036 doi:10.1038/ncomms8036 Published 24 April 2015

This paper is open access.

Portable x-ray machine

It’s all about the adhesive tape according to the researchers at Tribogenics. Yes, they can create x-rays by unrolling scotch tape in a vacuum. Neal Ungerleider’s Dec. 8, 2011 article for Fast Company,

Tribogenics’ products rely on a counterintuitive discovery: X-rays are generated when unrolling Scotch tape in a vacuum. In a Nature article, UCLA researchers Carlos Camara, Juan Escobar, Jonathan Hird, and Seth Putterman detailed how Scotch tape can generate surprisingly large amounts of X-rays thanks to visible radiation generated by static electricity between two contacting surfaces. The research encountered challenges thanks to the fact that Scotch tape and generic brand adhesive tapes generated slightly different energy signatures; the composition of Scotch tape adhesive is a closely guarded 3M trade secret. …

Fox [Dale Fox, Tribogenics’ Chief Scientist] told Fast Company that “every other X-ray source in the world uses a high-voltage transformer connected to a vacuum tube. In contrast, we’ve harnessed the power of the immense voltages in static electricity to create tiny, low-cost, battery-operated X-ray sources for the first time in history. It’s like the jump the electronics industry took when it moved from vacuum tubes to transistors.” According to Fox, Tribogenics has already developed X-ray energy sources the size of a USB memory stick. While Tribogenics representatives declined to discuss pricing for upcoming products, the firm “very comfortably” promised that the cost would be less than 10% than that of any existing X-ray technology.

This technology can be traced back to DARPA (Defense Advanced Research Projects Agency) in 2007 when the agency funded the company’s first research, according to the company website. There have been other military funds as well, the US Army Telemedicine and Advanced Research Center in 2010.

The company describes itself this way (from the home page),

Tribogenics patented technology enables portable, compact x-ray solutions for applications in precious metal, mining, military, medical imaging, security and other industries. By miniaturizing X-ray sources and eliminating the need for high voltage, we can create products and solutions unattainable using existing X-ray technology. Tribogenics revolutionary X-ray solution emerged from DARPA and TATRC-funded initiatives at UCLA and was developed by prominent scientists.

Ungerleider notes that the company has not launched any commercial products yet but this one sure looks interesting,

… ultra-portable X-ray machines show the greatest potential for becoming a disruptive medical technology. Tribogenics’ methods have revolutionary ramifications for catheterized radiation therapy, which currently poses significant radiation risks for patients, doctors, and nurses. According to Fox, the company’s products eliminate the need for radioactive isotopes.

If you are interested in this technology, I would suggest reading Ungerleider’s article for additional details.