MeV Synchrotron Radiation Research Articles

Design and performance of a new VIS–VUV photoluminescence beamline at UVSOR-III

A new bending-magnet beamline with a 2.5 m normal-incidence monochromator has been constructed to serve with a light source in the visible-vacuum-ultraviolet region for photoluminescence, transmission and reflection spectroscopies of solids at the UVSOR-III 750 MeV synchrotron radiation light source. The aim is to pave the way to establishing a beamline with high photon flux, high brilliance, high energy-resolution, high linear-polarization and low higher-order light. To obtain high photon flux and brilliance, the acceptance angle of the bending-magnet radiation was designed to be 40 mrad (H) × 14 mrad (V) and the post-mirror system employed Kirkpatrick-Baez optics. The incidence angle of the incoming light to the optical elements, except to the gratings, was set to a grazing angle in order to keep a degree of linear polarization. For achieving high energy-resolution, an off-plane Eagle-type monochromator was adopted. Higher-order unwanted light in the energy range below ∼11 eV was suppressed to be less than 0.1%.

SIMULATIONS OF PARTICLE ACCELERATION BEYOND THE CLASSICAL SYNCHROTRON BURNOFF LIMIT IN MAGNETIC RECONNECTION: AN EXPLANATION OF THE CRAB FLARES

It is generally accepted that astrophysical sources cannot emit synchrotron radiation above 160 MeV in their rest frame. This limit is given by the balance between the accelerating electric force and the radiation reaction force acting on the electrons. The discovery of synchrotron gamma-ray flares in the Crab Nebula, well above this limit, challenges this classical picture of particle acceleration. To overcome this limit, particles must accelerate in a region of high electric field and low magnetic field. This is possible only with a non-ideal magnetohydrodynamic process, like magnetic reconnection. We present the first numerical evidence of particle acceleration beyond the synchrotron burnoff limit, using a set of 2D particle-in-cell simulations of ultra-relativistic pair plasma reconnection. We use a new code, Zeltron, that includes self-consistently the radiation reaction force in the equation of motion of the particles. We demonstrate that the most energetic particles move back and forth across the reconnection layer, following relativistic Speiser orbits. These particles then radiate >160 MeV synchrotron radiation rapidly, within a fraction of a full gyration, after they exit the layer. Our analysis shows that the high-energy synchrotron flux is highly variable in time because of the strong anisotropy and inhomogeneity of the energetic particles. We discover a robust positive correlation between the flux and the cut-off energy of the emitted radiation, mimicking the effect of relativistic Doppler amplification. A strong guide field quenches the emission of >160 MeV synchrotron radiation. Our results are consistent with the observed properties of the Crab flares, supporting the reconnection scenario.

Effect of wavelength shifter on Indus-1

The Indus-1 is a 450 MeV synchrotron radiation source for the production of VUV radiation ( λ c=61 Å). In order to produce the radiation of shorter wavelength ( λ c=31 Å), a superconducting wavelength shifter (WLS) with a peak field of 3 T is being considered for Indus-1. In the Indus-1 beam lifetime is short; therefore, WLS will be kept on during beam injection. To predict WLS effect, Smith's Hamiltonian for Halbach's magnetic field model has been re-derived to estimate linear and nonlinear component under the compensated electron beam trajectory transformation. To minimize the linear effects of WLS, various linear compensation schemes and its effects on Indus-1 operation are presented.

A monitor of the focusing strength of plasma lenses using MeV synchrotron radiation

The focusing strength of plasma lenses used with high energy electron or positron beams can give rise to synchrotron radiation with critical energies in the MeV range. A method is described for measuring the characteristic energy of this radiation as a way of monitoring the strength of the focus. The principle has been implemented in a plasma lens experiment with a 28.5 GeV positron beam.

Compact synchrotron light source of the HSRC.

A 700 MeV synchrotron radiation source optimized in order to be incorporated in the university laboratory is under commissioning at Hiroshima University. The storage ring is of a racetrack type with two long straight sections for installing undulators. The bending field is as strong as 2.7 T, produced by normal-conducting magnet technology, and delivers synchrotron radiation with a critical wavelength of 1.42 nm. The strong magnetic field also enables a low-energy injection scheme to be employed owing to the fast radiation damping. A 150 MeV microtron has been adopted as the injector.

Mirror boxes and mirror mounts for photophysics beamline

A medium resolution beamline, viz. photophysics beamline is being built at INDUS-I, a 450 Mev synchrotron radiation source (SRS) at the Centre for Advanced Technology (CAT), Indore. To house the pre- and post-focusing toroidal mirrors and permit precision movements for steering the SRS beam up to the sample, two ultra-high vacuum (UHV) compatible mirror boxes and mirrors have been designed, fabricated and tested. Details of the setup, including UHV (P < 10−9 mbar) testing and performance evaluation of the mirror mounts under UHV conditions, are discussed in this paper.

Investigation on the characteristics of synchrotron radiation emitted by the Hefei 800 MeV synchrotron radiation facility

Based on Schwinger's theory, the spectral distribution, the angular distribution and the polarization of the Hefei 800 MeV synchrotron radiation facility were calculated. The measurement of the spectral distribution was carried out in the 300–800 nm range by using a tungsten halogen spectral irradiance standard source. The polarization and the angular distribution were investigated at 405 nm. A good agreement was found between experimental results and values predicted by the theory of synchrotron radiation derived by Schwinger. The difference of the relative spectral distribution between experimental and theoretical data is less than 1.5% in the 300–800 nm region and the difference between the angular distribution and the polarization is less than 5%.

Control system capable of gracefully degraded operation for the 750 MeV synchrotron radiation source

A control system which is capable of gracefullydegraded operation for the 750 MeV electron storage ring as a dedicated VUV (vacuum-ultra-violet) synchrotron radiation source at the UVSOR has been developed to provide a synchrotron radiation beam for a long time without any fatal shutdown. Based on a client-server model with a hierarchy of three layers, the control system was designed to be reconfigurable. Under normal operation, the distributed control system is configured so that two process computers control the storage ring cooperatively with full throughput. If a failure occurs in one computer, the control system is reconfigured so that the remaining functional computer can provide gracefully degraded operation to resume control of the storage ring for synchrotron radiation experiments. The control system automatically operates the storage ring with a single action on a menu initiated by an operator. Operational experience has shown that the control system can successfully operate the storage ring.

Beam Diagnostics for HESYRL, the 800-MeV Synchrotron Radiation Facility in Hefei

The beam diagnostic system for the 800 MeV synchrotron radiation facility is described here. A new type of monitor, a stripline and gap combined monitor, for both position and current is presented.