SR Beam Research Articles

First results of experiments with a medical one-coordinate X-ray detector on synchrotron radiation of VEPP-4

The first results of studying the performance of a fast X-ray one-coordinate detector on the SR beam from VEPP-4 are presented. The detector consists of 128 independent channels, each being a scintillation counter on the basis of NaI(Tl) crystals. The spatial resolution of the detector constitutes 1.5 mm and its speed of response is 128 × 1 MHz. The main purpose of the detector is to examine the human circulatory system by the method of difference angiography at an energy of quanta corresponding to the K-absorption edge of iodine (33.2 keV). The first results on radiation exposure of the blood vessels of a live dog with a spatial resolution of 0.75 mm are given.

Fast response amplitude scintillation detector for X-ray synchrotron radiation

The present paper describes a scintillation detector for X-ray synchrotron radiation. This detector has been created on the basis of a scintillator and a photoelectron multiplier (FEU-130) and its construction allows one to use the specific features of the time characteristics of synchrotron radiation from the electron storage ring. In a given range of amplitudes, the detector electronics makes a 64-channel amplitude analysis of the FEU-130 signal strobed by the revolution frequency of an electron bunch in the storage ring ( f 0 = 818 kHz). There is the possibility of operating the detector at high intensities of the monochromatic radiation incident on the scintillator. Such a possibility is directly provided by the time structure of SR and is not realizable with the use of other X-ray sources. The detector will find wide application in studies on X-ray structural analysis, transmission and fluorescent EXAFS- and XANES-spectroscopy, transmission scanning microscopy and microtomography, calibration of X-ray detectors and as a monitor on SR beams from the storage ring VEPP-4.

An attempt at coronary angiography with a large size monochromatic SR beam

The number of patients due to ischemic heart disease seems to be growing rapidly in Japan. Coronary angiography by Judkins' or Soncs' method is very invasive as is well known and thus imposes a burden on patients and physicians. The K-edge subtraction technique is considered to be applicable to intravenous angiography of coronary arteries. A feasibility study of K-edge subtraction with monochromatized SR has been initiated at Photon Factory since 1984. In 1985, a real time observation of intravenous angiography of a cat, utilizing a monochromatic beam with a size of 64 mm by 55 mm, was performed. This paper describes some results of our preliminary experiments and our future systems of clinical application.

Synchrotron radiation damage observations in normal incidence copper mirrors

Water-cooled copper mirrors used at near-normal incidence on two beamlines at the NSLS are observed to undergo severe degradation upon exposure to the direct SR beam. These mirrors are used on beam lines designed to utilize radiation in the wavelength regions longer than 100 nm and are coated with a UV reflection-enhancing coating, consisting of one or more bilayers of aluminum with a MgF 2 overcoat. Beamline performance degrades very rapidly following installation of a new set of mirrors. Analysis of the mirror surfaces by various non-destructive techniques indicates severe degradation of the coating and surface along the central strip where most of the X-ray power is absorbed from the beam. In one case where the mirror had three bilayer coatings, the outer coating layer has disappeared along the central strip. Rutherford backscatter measurements indicate compositional changes between layers and confirm the existence of a carbon deposit on the surface. Thermal modeling suggests that most of the damage is caused by direct photon interaction, since the temperature rise in the energy deposition region is small.

Experiments on X-ray lithography using synchrotron radiation from the VEPP-2M storage ring

During the last few years the electron-positron storage ring VEPP-2M of the Institute of Nuclear Physics in Novosibirsk has been used as an efficient source for X-ray lithography in the intermediate wavelength range (λ ∼ 10 A ̊ ) . Selection of the required part of the SR spectrum is done by means of a mask substrate fabricated from silicon of 2 μm thickness; Al windows can be installed before the X-ray mask. Exposures can be made in vacuum or in helium. The lithographic system can be used to fabricate one-layer devices on 100 mm diameter wafers with a production rate of 10–12 wafers per hour. The influence of the geometric conditions and of various temperature modes of exposure on the precision of replication from the mask onto the resist film have been investigated. Parameters of several X-ray and electron resists are studied. A lithographic system for fabricating multilayer devices is being developed. At present near to the storage ring a special room with clean-room environment is being built. Two SR beam lines come into it. The first beam line brings SR from the bending magnet. In the future the second beam line will bring SR from the special “lithographic wiggler”. In this room all operations on wafer preparation, subsequent processing steps of resist and masked surfaces after X-ray lithography and control of the patterns obtained will be carried out.

Double photoionisation in Ca and Sr in the region of the subshell 3p (or 4p) ionisation (25-36 eV)

A time-of-flight mass spectrometer has been crossed with atomic beams of Ca and Sr and a source of monochromated synchrotron radiation in order to obtain the ratio of double-to-single photoionisation cross sections in the region of the 3p (or 4p) ionisation thresholds, between 25 and 35 eV. Attempts are made to correlate the structure observed in both elements with recently published photoabsorption, photoelectron and ejected-electron spectra.

Comparison of reagent translation and vibration on the dynamics of the endothermic reaction Sr+HF

The endothermic reaction Sr+HF(v=0)→SrF+H has been studied as a function of collision energy (4–14 kcal/mole) using a crossed beam geometry in which a seeded HF beam intersects a thermal Sr beam. At the same total energy this reaction is compared to the Sr+HF(v=1, J=1) reaction carried out under beam-gas conditions with a pulsed HF laser as the excitation source. In both cases the SrF products are detected by laser induced fluorescence. Using the Ba+HF→BaF+H reaction as an internal reference, the cross section of the Sr+HF(v=1) reaction is found to be 1–10 times greater than for the Sr+HF(v=0) reaction when the same total energy is supplied as reagent translation. Product internal energy distribution and total relative cross sections as a function of collision energy are also measured. Phase space calculations are able to reproduce most of these results. This agreement and other arguments suggest that the Sr+HF reaction often proceeds via multiple encounters which scramble the reagent energy modes during the course of a reactive collision.

A simple system of the short-wave synchrotron radiation prevention in the 30 Å to 180 Å wavelength range

A simple preventer of the short-wave SR light is described. This block, based on two rotatable plane-parallel mirrors, with constant direction of the exit beam is operated in the SR beam line on VEPP-2M storage ring. The prevention efficiency of this system is not worse than 0.6%, the transmission efficiency being not less than 85%.

A proposal to install a superconducting wiggler magnet on the storage ring VEPP-3 for generation of the synchrotron radiation

A proposal is discussed to install a superconducting wiggler magnet on the storage ring VEPP-3 in order to shift the spectrum of the synchrotron radiation generated to a shortr wavelength range and to enhance the SR intensity. The basic considerations are presented for optioned wiggler [arameters aimed at the maximum brightness of the source in the range of λ ≈ 1 A ̊ . The characteristics of the SR beam generated by the wiggler have been calculated (i.e. total power radiated, spectral and angular distribution). A 20-pole wiggler design is presented with the length of 1 m, maximum magnetic field strength of 40 kGs, poles spaced by 16 mm and vertical aperture accessible for the electron beam of about 8 mm. The intended wiggler installation scheme in a storage ring straight section envisages the storage of electrons apart from the wiggler aperture using the complete admittance of the storage ring with the subsequent shift of the stored beam into the wiggler by means of the localized closed orbit distortion. The influence of the wiggler field on particles motion in the storage ring has been considered (e.g. closed orbit distortion, betatron oscillations frequency shift, contribution to the cubic nonlinearity etc.).