Scientists create compact particle accelerators that drive electron beams nearer speed of light

 Ben Robinson, University of Manchester

https://phys.org/news/2020-08-scientists-compact-particle-electron-nearer.html

Scientists have successfully developed a pocket-sized particle accelerator capable of projecting ultra-short electron beams with laser light at more than 99.99% of the speed of light.

"We overcame this problem by developing a unique THz source which produced longer pulses containing only a narrow range of frequencies, significantly enhancing the interaction. Our next milestone is to demonstrate even higher energy gains while maintaining beam quality. We anticipate this will be realized through refinements to increase our THz source energy, which are already underway."

Professor Steven Jamison of Lancaster University who jointly leads the program, explained: "The controlled acceleration of relativistic beams with terahertz frequency laser-like pulses is a milestone in development of a new approach to particle accelerators. In using electromagnetic frequencies over one hundred times higher than in conventional particle accelerators, a revolutionary advance in the control of the particle beams at femtosecond time scales becomes possible."

"With our demonstration of terahertz acceleration of particles traveling at 99.99% of the speed of light, we have confirmed a route to scaling terahertz acceleration to highly relativistic energies."

While the researchers have an eye to a long term role of their concepts in replacing multi-kilometer scale research accelerators (such as Europe's 3 km long X-ray-source in Hamburg) with devices mere meters in length, they expect the immediate impacts will be in the fields of radio-therapy and in materials characterisation.

Dr. Darren Graham, Senior Lecturer in Physics at The University of Manchester said: "Achieving this milestone would not have been possible without the unique collaborative environment provided by the Cockcroft Institute, which has helped bring together scientists and engineers from University of Lancaster, The University of Manchester and the staff from STFC at Daresbury Laboratory."

To achieve this result, the researchers have had to slow down light to match the speed of the electrons using a specially designed metallic structure lined with quartz layers thinner than a human hair.

This huge leap forward simultaneously offers the ability to both measure and manipulate particle bunches on time scales of less than 10 femtoseconds (0.000 000 000 000 01 seconds, or the time is takes light to travel 1/100th of a millimeter). This will enable them to create strobe photographs of atomic motion.

This successful demonstration paves the way to the development of high-energy, high-charge, high-quality Terahertz (THz) driven accelerators, which promise to be cheaper and more compact. Reducing the size and cost of accelerator technology, will open up these incredible machines to a much wider range of applications.

Particle accelerators are widespread with applications in basic research in particle physics, materials characterisation, radiotherapy in hospitals, where they are used to treat cancer patients, radioisotope production for medical imaging, and security screening of cargo. The basic technology (radio-frequency oscillators) underpinning these machines however, was developed for radar during the Second World War.

In new research published today in Nature Photonics, a collaborative team of academics show that their unique solution is to use lasers to generate terahertz frequency pulses of light. Terahertz is a region of the electromagnetic spectrum between infrared (used in TV remotes) and microwave (used in microwave ovens). Laser-generated THz radiation exists in the ideal millimeter-scale wavelength regime, making structure fabrication simpler but most importantly providing the half-cycle lengths that are well suited for acceleration of whole electron bunches with high levels of charge.

Lead author on the paper Dr. Morgan Hibberd from The University of Manchester said: "The main challenge was matching the velocity of the accelerating THz field to the almost speed-of-light electron beam velocity, while also preventing the inherently lower velocity of the THz pulse envelope propagating through our accelerating structure from significantly degrading the length over which the driving field and electrons interact."

Presentation-Terahertz techniques for proton exchange membrane fuel cell applications by Decio Alves De Lima

Wednesday 13 November 2019, 12:00pm to 12:20pm

Venue

C Floor, Engineering Building, Lancaster

Open to

Alumni, Applicants, External Organisations, Postgraduates, Prospective Students, Public, Staff, Undergraduates

Registration

Registration not required - just turn up

https://www.lancaster.ac.uk/events/terahertz-techniques-for-proton-exchange-membrane-fuel-cell-applications

Proton exchange membrane fuel cells (PEMFC) are electrochemical devices at the forefront of clean energy production for portable, transportation and, to a lesser extent, stationary applications.

Adequate water management is critical for satisfactory PEMFC operation: Nafion electrolyte membranes require hydration to achieve good proton conduction and avoid material damage and, at the same time, water is a by-product of the cathode half-reaction and thus must be removed promptly to prevent cell flooding and fuel starvation at catalytic active sites. Current water visualisation techniques e.g. NMR, neutron, x-ray, optics, fluorescence, infrared are expensive and not readily available. Terahertz (THz) radiation are electromagnetic waves in the spectral region between 100 GHz and 10 THz. The high sensitivity of THz radiation to liquid water compared to polymeric structures enables contrast to be observed for inspecting water build-up in Nafion electrolyte membranes. In this project, we investigate the feasibility of a simple and compact THz transmission imaging system for qualitative inspection of flooding in a specially designed THz transparent PEMFC as well as qualitative and quantitative investigation of the hydration level in several industry-relevant Nafion membranes.

Energy-free superfast computing invented by scientists using light pulses

Using ultrashort pulses of light enables extremely economical switching of a magnet from one stable orientation (red arrow) to another (white arrow). This concept enables ultrafast information storage with unprecedented energy efficiency. Credit: © Brad Baxley (parttowhole.com)

https://phys.org/news/2019-05-energy-free-superfast-scientists-pulses.html

Superfast data processing using light pulses instead of electricity has been created by scientists.

The invention uses magnets to record computer data which consume virtually zero energy, solving the dilemma of how to create faster data processing speeds without the accompanying high energy costs.

Today's data centre servers consume between 2 to 5% of global electricity consumption, producing heat which in turn equires more power to cool the servers.

The problem is so acute that Microsoft has even submerged hundreds of its data centre services in the ocean in an effort to keep them cool and cut costs.

Most data are encoded as binary information (0 or 1 respectively) through the orientation of tiny magnets, called spins, in magnetic hard-drives. The magnetic read/write head is used to set or retrieve information using electrical currents which dissipate huge amounts of energy.

Now an international team publishing in Nature has solved the problem by replacing electricity with extremely short pulses of light—the duration of one trillionth of a second—concentrated by special antennas on top of a magnet.

This new method is superfast but so energy efficient that the temperature of the magnet does not increase at all.

The team includes Dr. Rostislav Mikhaylovskiy, formerly at Radboud University and now Lancaster University, Stefan Schlauderer, Dr. Christoph Lange and Professor Rupert Huber from Regensburg University, Professor Alexey Kimel from Radboud University and Professor Anatoly Zvezdin from the Russian Academy of Sciences.

They demonstrated this new method by pulsing a magnet with ultrashort light bursts (the duration of a millionth of a millionth of a second) at frequencies in the far infrared, the so called terahertz spectral range.

However, even the strongest existing sources of the terahertz light did not provide strong enough pulses to switch the orientation of a magnet to date.

The breakthrough was achieved by utilizing the efficient interaction mechanism of coupling between spins and terahertz electric field, which was discovered by the same team.

The scientists then developed and fabricated a very small antenna on top of the magnet to concentrate and thereby enhance the electric field of light. This strongest local electric field was sufficient to navigate the magnetization of the magnet to its new orientation in just one trillionth of a second.

The temperature of the magnet did not increase at all as this process requires energy of only one quantum of the terahertz light—a photon—per spin.

Dr. Mikhaylovskiy said: "The record-low energy loss makes this approach scalable.

Future storage devices would also exploit the excellent spatial definition of antenna structures enabling practical magnetic memories with simultaneously maximal energy efficiency and speed."

He plans to carry out further research using the new ultrafast laser at Lancaster University together with accelerators at the Cockroft Institute which are able to generate intense pulses of light to allow switching magnets and to determine the practical and fundamental speed and energy limits of magnetic recording.

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New Terahertz Plasma Diagnostic System for Nuclear Fusion Reactors

By Will Soutter

http://www.azom.com/news.aspx?newsID=42606

Engineers at Lancaster University are reinventing the vacuum tube to produce Terahertz signals to monitor plasma turbulence in nuclear fusion reactors.

The Engineering and Physical Sciences Research Council (EPSRC) has provided £450,000 for the study, which is being done by a collaborative group including researchers from the University of Leeds, the Beijing Vacuum Electronics Research Institute and the University of California Davis.

 “The device developed by this project will result in a novel plasma diagnostic system which is fundamental for the future development of nuclear fusion reactors, potentially leading to a breakthrough in nuclear fusion techniques."

Professor Claudio Paoloni   

Nuclear fusion is one of the cleanest forms of energy possible, and it could provide an almost inexhaustible supply of energy. However, getting practical fusion reactor running is extremely difficult to achieve. It requires temperatures exceeding 100 million °C for the fusion reaction to take place, and a strong magnetic field to contain the fusion plasma.

During the fusion reaction, unwanted turbulence may take place, which could disrupt the plasma enough to slow the reaction or prevent it taking place altogether - leading to a loss of energy, or even hazardous containment issues.

Terahertz vision

Terahertz waves possess specific properties which enable them to non-destructively penetrate different types of materials. They hold promise for use in practical nuclear fusion reactions, as terahertz radiation can help understand plasma behavior without greatly disturbing the delicate fusion material.

Previously, research into the applications of terahertz radiation has covered detection of explosives, analysis and restoration of artistic masterpieces, and diagnosis of cancer. The technology has been limited to laboratories, however, as the techniques used require powerful terahertz sources, which are typically very large in size.

The old and the new

The team of researchers intends to develop a powerful, compact and cost-effective powerful Terahertz vacuum electron device by using the latest microfabrication processes to allow traditional vacuum tubes to reach terahertz frequencies.

The device being built would be installed at the nuclear fusion test facility in Princeton (the National Spherical Torus Experiment) and would become the main part of the plasma diagnostic system. The new device would enable commercialization of the technology by taking it from the laboratory to the market.

T-rays' electronics to shed light on nuclear fusion

http://www.nanowerk.com/news2/green/newsid=37667.php

(Nanowerk News) In the race to secure clean energy in the future, Lancaster University Engineers are reinventing a piece of technology which has so far only been used in labs to diagnose cancer, detect explosives, and even analyse grand artistic masterpieces.

Working with world-leaders in their field, researchers will employ modern microfabrication processes to bring vacuum tubes - born at the beginning of the electronics era - up to Terahertz frequencies (hundreds of GHz), which they hope will bring about a breakthrough in the understanding of the mechanisms of nuclear fusion.

Nuclear fusion, considered to be a potential future option for a clean and inexhaustible energy supply, requires extremely high temperatures (more than 100 million°C) for the fuel, a hot plasma that has to be confined by a proper magnetic field. Unfortunately, this plasma can suffer from undesired turbulence that, if too intense, can block the fusion reaction, resulting in energy loss or, in a worst case scenario, melt the metal wall of the reactor. Only Terahertz radiation can provide an accurate insight into plasma behaviour without perturbing this extremely delicate material.

Terahertz waves (or T-rays) have unique properties as they can penetrate many materials without damaging them. In recent years, Terahertz radiation has been put to use in fields as diverse as cancer early diagnosis, airport security and fine art restoration. But until now, Terahertz technology has been largely confined to the laboratory because of the lack of compact and powerful sources.

Funded by the Engineering and Physical Sciences Research Council, the £450,000 research project brings together an international team of researchers including the University of Leeds, the University of California Davis, US, and the Beijing Vacuum Electronics Research Institute, China.

Once built, the device will be the core of the plasma diagnostic, led by Professor Neville C. Luhmann, University of California Davis, US, to be installed at the National Spherical Torus Experiment (NSTX), a nuclear fusion test facility at Princeton US.

Lancaster University’s Professor Claudio Paoloni said: "Considering that 60kg of fuel for nuclear fusion can produce an energy equivalent to 250,000 tons of oil, it is a very important technology for the future provision of clean, reliable energy. However, to do this efficiently and safely, a reliable new way of monitoring plasma turbulence is needed.

"The device developed by this project will result in a novel plasma diagnostic system which is fundamental for the future development of nuclear fusion reactors, potentially leading to a breakthrough in nuclear fusion techniques.

"Ultimately, by developing a compact, affordable and powerful Terahertz vacuum electron device we will demonstrate that it can have a formidable impact at a commercial level. By taking Terahertz technology out of the laboratory and into the real world, we will finally enable many other fundamental applications to take a step forward in fields from healthcare and security to food analysis and even art."

He added: "I am very excited to face this challenging project with scientists of the highest calibre including Professor Neville C. Luhmann, Jr., University of California Davis, US, a pioneer in the field of Terahertz vacuum electron devices and leader of the plasma diagnostic development for the NSTX experiment at Princeton University, Professor Jinjun Feng, Vice Director of the most important Chinese research institute on vacuum electronics, and Dr Paul Steenson of the University of Leeds."

Source: Lancaster University