143 research outputs found
Fast barrier-free switching in synthetic antiferromagnets
We analytically solve the Landau-Lifshitz equations for the collective
magnetization dynamics in a synthetic antiferromagnet (SAF) nanoparticle and
uncover a regime of barrier-free switching under a short small-amplitude
magnetic field pulse applied perpendicular to the SAF plane. We give examples
of specific implementations for forming such low-power and ultra-fast switching
pulses. For fully optical, resonant, barrier-free SAF switching we estimate the
power per write operation to be pJ, 10-100 times smaller than for
conventional quasi-static rotation, which should be attractive for memory
applications.Comment: 12 pages, 4 figure
Laserwire at the Accelerator Test Facility 2 with Sub-Micrometre Resolution
A laserwire transverse electron beam size measurement system has been
developed and operated at the Accelerator Test Facility 2 (ATF2) at KEK.
Special electron beam optics were developed to create an approximately 1 x 100
{\mu}m (vertical x horizontal) electron beam at the laserwire location, which
was profiled using a 150 mJ, 71 ps laser pulse with a wavelength of 532 nm. The
precise characterisation of the laser propagation allows the non-Gaussian
transverse profiles of the electron beam caused by the laser divergence to be
deconvolved. A minimum vertical electron beam size of 1.07 0.06 (stat.)
0.05 (sys.) {\mu}m was measured. A vertically focussing quadrupole just
before the laserwire was varied whilst making laserwire measurements and the
projected vertical emittance was measured to be 82.56 3.04 pm rad.Comment: 17 pages, 26 figures, submitted to Phys. Rev. ST Accel. Beam
Optical diffraction radiation for position monitoring of charged particle beams
In the framework of the future linear collider collaboration (CLIC, ILC), non-intercepting beam monitoring instruments are under development for very low emittance and high charge density beams. Optical diffraction radiation (ODR) was studied and developed during the last years focussing on beam size measurements. We propose in the paper to consider the use of diffraction radiation for ultra relativistic beams as position monitors with applications for the centering of scrapers, collimators and targets with high resolution. We present the experimental results obtained using small aperture slits on the ATF2 extraction beam line at KEK and on the Cornell Electron Storage Ring with 1.2 GeV and 2.1 GeV electrons respectively
Coherent Cherenkov radiation as an intense THz source
Diffraction and Cherenkov radiation of relativistic electrons from a dielectric target has been proposed as mechanism for production of intense terahertz (THz) radiation. The use of an extremely short high-energy electron beam of a 4th generation light source (X-ray free electron laser) appears to be very promising. A moderate power from the electron beam can be extracted and converted into THz radiation with nearly zero absorption losses. The initial experiment on THz observation will be performed at CLARA/VELA FEL test facility in the UK to demonstrate the principle to a wider community and to develop the radiator prototype. In this paper, we present our theoretical predictions (based on the approach of polarization currents), which provides the basis for interpreting the future experimental measurements. We will also present our hardware design and discuss a plan of the future experiment
DEVELOPMENT OF A E-LEARNING TRAINER WITH FEEDBACK BASED ON MOODLE'S PLUGIN STACK
This thesis describes the current status of online learning systems in the world, why they are needed and what are their drawbacks. Then it's described, why you can create the best systems by using STACK, and a little about such a simulator, which is created by us
Eupraxia, a step toward a plasma-wakefield based accelerator with high beam quality
The EuPRAXIA project aims at designing the world's first accelerator based on advanced plasma-wakefield techniques to deliver 5 GeV electron beams that simultaneously have high charge, low emittance and low energy spread, which are required for applications by future user communities. Meeting this challenging objective will only be possible through dedicated effort. Many injection/acceleration schemes and techniques have been explored by means of thorough simulations in more than ten European research institutes. This enables selection of the most appropriate methods for solving each particular problem. The specific challenge of generating, extracting and transporting high charge beams, while maintaining the high quality needed for user applications, are being tackled using innovative approaches. This article highlights preliminary results obtained by the EuPRAXIA collaboration, which also exhibit the required laser and plasma parameters
Demonstration of a laserwire emittance scanner for hydrogen ion beams at CERN
A non-invasive, compact laserwire system has been developed to measure the
transverse emittance of an H- beam and has been demonstrated at the new LINAC4
injector for the LHC at CERN. Light from a low power, pulsed laser source is
conveyed via fibre to collide with the H- beam, a fraction of which is
neutralized and then intercepted by a downstream diamond detector. Scanning the
focused laser across the H- beam and measuring the distribution of the
photo-neutralized particles enables the transverse emittance to be
reconstructed. The vertical phase-space distribution of a 3 MeV beam during
LINAC4 commissioning has been measured by the laserwire and verified with a
conventional slit and grid method.Comment: 10 pages, 13 figures, to be published in Physical Review Special
Topics - Accelerators and Beam
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