Future Synchrotron Radiation Sources Research Articles

Uncertainty in the isosceles multipactor threshold of triangularly grooved surfaces based on polynomial chaos

The success of future synchrotron radiation sources will be closely linked with the development of high-brightness continuous-wave capable electron injectors. Superconducting radiofrequency (SRF) photo injectors, as operated at the Helmholtz-Zentrum Dresden-Rossendorf among others, are a promising approach for this purpose. Yet, the reliability of electron sources can be significantly limited by electron multipacting (MP), a very common phenomenon in radio frequency (RF) vacuum devices. In a previous study it was shown that the choice of grooved surfaces for the cathode stem promises to be a good measure to suppress MP. The accuracy of the MP threshold is mainly determined by the uncertainty of secondary emission properties of the material. In the past, to determine the MP thresholds in various RF devices, numerous experiments and numerical simulation studies have been conducted worldwide. Nevertheless, there is no particular study to be found on the observed uncertainty in MP thresholds. In this paper, the influence of uncertainty in secondary electron yield (SEY) parameters on the MP threshold of surfaces with isosceles triangular grooves is investigated using the generalized polynomial chaos (gPC) method that allows an efficient representation of random field solutions to partial differential equations with random data.

X선의 초고속 결정구조 측정법

무기단결정을 광 펄스로 여기 한 격자에서 광학이나 음향포논을 이용하여 광 여기 반도체가 서브피코초로 관측하고 있다. 다수의 회절 점으로 결정구조를 파악하는 것으로써 광 여기에 의한 분자결정 구조변화를 관측하는 것이 보고되고 있고 또한 반응이 진행되고 있는 중에 분자구조를 하나하나 영상으로 관측하는 것이 연구되고 있다. 단백질 분자구조의 시간에 따른 변화와 용액 중 분자의 광반응에 따른 구조변화를 파악하고 있는데 이것은 시스템에 따라 펨토 초에서 초 단위까지 다양하고 광범위하게 고도의 시간분해능으로 계측할 수 있는 X선 측정기술이다. We have surveyed on significant progress in recent developments of accelerator-based pulsed X-ray sources has offered the opportunity for time-resolved studies on fast structure dynamics on the nanometer scale. The required and currently available techniques for time resolved X-ray diffraction measurements using the third-generation synchrotron radiation sources are summarized. Ultrafast X-ray experimental techniques are discussed for femtosecond studies at future synchrotron radiation sources.

Development of Ultrafast Time-Resolved Techniques in the X-Ray Regime

Significant progress in recent developments of accelerator-based pulsed X-ray sources has offered the opportunity for time-resolved studies on fast structural dynamics on the atomic scale. The required and currently available techniques for time-resolved X-ray diffraction measurements using the third-generation synchrotron radiation sources are summarized. Ultrafast X-ray experimental techniques are discussed for femtosecond studies at future synchrotron radiation sources.

Beam commissioning and achieved performance of SPring-8 storage ring phase-2 lattice with four magnet-free long straight sections

We had installed four magnet-free long straight sections (LSSs) of 27 m in the SPring-8 storage ring in the summer 2000 in spite that a lattice modification breaks high symmetry of the ring optics. This is because by the potentiality of the LSSs we can not only increase the brilliance of photon beams but also develop innovative light sources. The most serious problem for introducing the LSSs was that the lattice modification markedly deteriorates the stability of electron beams at a large amplitude or a large momentum deviation. To overcome this, a concept of “Quasi-Transparent Matching of sextupole fields” was proposed. This concept simultaneously manages both the symmetry restoration of sextupole fields and the local compensation of chromaticities. Owing to the reasonable lattice design and to the preparation with the precise ring model, the beam commissioning was successfully accomplished for about 3 weeks, achieving the beam performance which almost equals to that in the phase-1 lattice without the LSSs. A long undulator was also installed and it has been used in routine user operation. This success is the first step to challenge the new ideas growing up into future synchrotron radiation sources in the SPring-8 storage ring.

NSLS X1B - an undulator beamline for high resolution soft X-ray spectroscopy

The X1 undulator on the X-ray ring of the NSLS at Brookhaven is an extremely bright source of soft X-ray photons. On the recently completed spectroscopy beamline X1B we have attempted to utilise the intrinsically narrow beam size and divergence to maximise the intensity throughput in a spherical grating monochromator (SGM). The high power density of the undulator radiation requires the use of water cooled mirrors, entrance slit and grating. Calculations predict that simple side cooled copper pads attached to optical elements will be sufficiently effective that resolution degradation due to thermal deformation of figure error will be negligible in the SGM design. This is confirmed by attainment of resolution superior to other SGMs and the BESSY SX700-II monochromator over the energy range 300–540 eV (C1s−1, N1s−1 and Ols−1). At a resolution comparable to the best so far obtained for the nitrogen N 1s π∗ excitation (401 eV) on other monochromators we have demonstrated an intensity increase, at the sample, of more than three orders of magnitude. The design consideration upon which beamline X1B is based are highly relevant to the construction of soft X-ray monochromators at future synchrotron radiation sources such as the ALS (Berkeley). Elettra (Trieste) and BESSYII (Berlin).

Evaluation of the X-ray Response of a Position-Sensitive Microstrip Detector with an Integrated Readout Chip

Many of the scientific programs proposed for implementation at existing and future synchrotron radiation sources involve measurement of the spatial distribution of transmitted or diffracted x-ray beams. The design of a general purpose position-sensitive detector for use in such experiments must address several conflicting requirements. Ideally, such a detector would meet the following criteria: high detection efficiency over a wide energy range, large dynamic range in measured photon intensities and response to a wide range of measurement intervals. Existing detector systems only partially meet these requirements, although much work has gone into improving the current technology.

Area detectors capable of recording X-ray diffraction patterns at high count-rates

The Princeton SIT X-ray detector is an electro-optical system designed for recording X-ray diffraction patterns from biological structures. The detector, based on a silicon intensified-target vidicon (SIT), can measure X-ray intensities over an 80 mm diameter area without the count-rate limit characteristic of a photon counting system. Over a wide range of intensities, the accuracy of measurement approaches the quantum limit. Several versions of the device have been constructed, tested and applied to important biophysical problems. The SIT detector has proved particularly useful for the study of dynamic systems with the aid of the intense synchrotron radiation X-ray beams available at EMBL/DESY and SSRL/SLAC. The detectors used in such experiments at future synchrotron radiation sources are likely to be similar to the SIT detector, but based instead on a newer electro-optical device, the solid state imager (e.g. CCD).

Properties and characteristics of present and future synchrotron radiation sources

Synchrotron radiation from accelerators and storage rings is being increasingly used in many fields of basic and applied science. Its unique characteristics makes it a new ideal source for many applications, especially in the far UV and X-ray spectral regions. The porperties of synchrotron radiation are described and a discussion is given of presently available and planned sources as well as some likely future developments.