Conceptual design of the vacuum system of the Spanish synchrotron light source (ALBA) storage ring

ALBA will be a third generation synchrotron light facility to be built near Barcelona (Spain). The design phase of ALBA is almost completed and the first components are ready to be ordered. Commissioning of the storage ring is foreseen to start at the end of 2008. The circumference of the storage ring of ALBA is 268.8 m and it will be divided into 16 vacuum sections by ultra high vacuum (UHV) gate valves. The vacuum chamber will be made of stainless steel with vertical aperture of 28 mm and 72 mm width. The vacuum chamber will be connected to an antechamber with a slot of 10 mm height. The antechamber will have the crotch absorbers which will absorb the unwanted synchrotron radiation. The pumping will be by sputter ion pumps (SIP), NEG pumps and titanium sublimation pumps (TSP), with an overall pumping speed from SIP of 57,400 l/s. This will maintain an average dynamic pressure of around 1 × 10⁻⁹ mbar to achieve a beam lifetime >15 h at the designed current.     

A diffusive light collection system for hard X-ray astronomical scintillation detectors

A novel design of a detector system for hard X-ray astronomy is described which permits large sensitive areas to be constructed on a modular basis. The system also incorporates high quality active shielding without the use of the phoswich system. The development and performance of the diffusive light collection optics are discussed.     

The background counting rates in a balloon borne hard X-ray telescope

A detailed Monte Carlo model of a hard (20–300 keV) X-ray astronomical telescope has been developed in order to calculate the energy loss distribution of the unwanted background noise events in the prime detection elements. The spectral distributions of the background rates measured at balloon altitudes over Palestine, Texas are compared to the predictions of the theoretical model. Good agreement has been found in terms of both the overall intensity level as well as the spectral distribution.     

上海光源储存环真空系统

上海光源储存环真空系统已于2007年底建成并开始运行.这个真空系统采用了双室结构的薄壁不锈钢真空室,其尺寸公差都小于1mm,真空室安装位置公差都小于2mm;分散的吸收器有序排列在抽气室内,把同步辐射光准直并引入光束线,同时吸收废弃的同步辐射光,把热量转移到真空室外;波纹管内的高频屏蔽机构为单指型,避免了指间接触力和磨擦;(SIP+NEG)复合泵、SIP和TSP共用,采用合理的激活NEG泵和升华钛丝的工艺程序,提供了强大的抽速和容量.真空预调试时各段真空室内的极限真空都达到5×10 -9Pa.全环真空室安装并连通后,大部分真空室不烘烤,只烘烤全环真空泵的情况下,极限真空达到2×10 -8Pa.储存环运行在束流剂量260Ah、能量3.5GeV、流强220mA时,动态压强为0.8×10 -7Pa,束流寿命21h,达到了真空系统的设计指标1.33×10 -7Pa.     

800MeV储存环超高真空系统数据计算机监测系统

介绍了国家同步辐射实验室800MeV储存环真空数据计算机监测系统，并对其硬件结构和软件部分作了简述。该系统自开始使用至今已5年多，运行情况良好。记录了真空系统的大量真空数据，为电子储存环机器的运行、束流寿命研究和故障的分析、处理提供了可靠的依据，很好地满足了设备使用的要求。     

Targets emitting transition radiation for performing X-ray lithography by the tabletop synchrotron MIRRORCLE-20SX

The tabletop storage ring synchrotron (SRS) MIRRORCLE-20SX is a powerful source of soft X-rays emitted from transition radiation (TR) targets. SRS can be used as a source for performing X-ray lithography (XRL) when it emits TR power P_XRL50–100 mW of photons having energy in the range 490–1860 eV. One-foil targets in SRS can emit a high TR power, and the electron beam geometry of MIRRORCLE-20SX requires using TR strip targets with a width 3 mm. P_XRL emitted by one-foil strip TR targets is estimated for several foil materials, and varying foil thickness d. These results show that a target containing one C foil with d260 nm can be used for performing XRL. Target made of one collodion foil with d290 nm, and target of one Al foil with d200 nm emit less, but could also be used for XRL. We manufactured such targets by depositing layers of these materials on slide glass, using Teepol as a releasing agent, and subsequently floating them on a water surface. The C layer is prepared by a horizontal resistance thermal evaporation, and supported by a 270–300 nm thick collodion layer, formed onto the Teepol film. The Al layer is thermally evaporated.     

Small pixel CZT detector for hard X-ray spectroscopy

A new small pixel cadmium zinc telluride (CZT) detector has been developed for hard X-ray spectroscopy. The X-ray performance of four detectors is presented and the detectors are analysed in terms of the energy resolution of each pixel. The detectors were made from CZT crystals grown by the travelling heater method (THM) bonded to a 20×20 application specific integrated circuit (ASIC) and data acquisition (DAQ) system. The detectors had an array of 20×20 pixels on a 250 μm pitch, with each pixel gold-stud bonded to an energy resolving circuit in the ASIC. The DAQ system digitised the ASIC output with 14 bit resolution, performing offset corrections and data storage to disc in real time at up to 40,000 frames per second. The detector geometry and ASIC design was optimised for X-ray spectroscopy up to 150 keV and made use of the small pixel effect to preferentially measure the electron signal. A ²⁴¹Am source was used to measure the spectroscopic performance and uniformity of the detectors. The average energy resolution (FWHM at 59.54 keV) of each pixel ranged from 1.09±0.46 to 1.50±0.57 keV across the four detectors. The detectors showed good spectral performance and uniform response over almost all pixels in the 20×20 array. A large area 80×80 pixel detector will be built that will utilise the scalable design of the ASIC and the large areas of monolithic spectroscopic grade THM grown CZT that are now available. The large area detector will have the same performance as that demonstrated here.     

EAST水平硬X射线诊断单元研究

设计制作了用于EAST托卡马克装置水平窗口的基于CdTe探头的硬X射线诊断单元.经与EAST联机试验运行,结果表明,该诊断单元设计原理正确,空间分辨率精度及辐射屏蔽达到设计目标,能够满足测量20keV～200keY能量范围等离子体的硬X射线韧致辐射的要求.     

Development of SPring-8 vacuum system

SPring-8 storage ring has been available for user operation with low emittance and extreme stability for over 10 years. However there occurred some problems in the components of the storage ring due to high-brightness synchrotron radiation (SR) and low-emittance operation. On the vacuum system of the storage ring, an accurate pressure could not be measured near the photon absorber due to scattered high-energy SR to the gauge head. High-energy SR activated dissolved oxygen in cooling water, and the activated dissolved oxygen corroded the inside of the photon absorbers in SR irradiation part. Air leakage occurred at an injection chamber due to impact by a small-size electron beam produced by low-emittance operation.We investigated the cause of the aforementioned difficulties with the vacuum system and prescribed the treatments described in this paper. In addition, we are making continual efforts at further system upgrades such as developing an RF shield that suppresses temperature increase in the shield in possible high-current operation.     

Laser driven X-ray parametric amplification in neutral gases—a new brilliant light source in the XUV

In this paper we present the experimental setup and results showing a new type of strong-field parametric amplification of high-order harmonic radiation. With a simple semi-classical model, we can identify the most important experimental parameters, the spectral range and the small signal gain in gases. Using a single stage amplifier, a small signal gain of 8000 has been obtained in argon for the spectral range of 40-50 eV, using 350 fs, 7 mJ pulses at 1.05 μm. An outlook for an experiment employing a double stage gas system will be given.     

Bright diode laser light source

A simplified multiwavelength prototype of an axially symmetric diode laser device based on stacks made of single emitters has been made, and the performance of the device has been demonstrated experimentally. The results verify that kilowatt-level light power can be focused into a circular spot with a 1/e2 diameter of 360 microm, a focal length of 100 mm, and a numerical aperture of 0.24, thus producing an average power density in excess of 10 kW/mm2 and a brightness of 6x10(10) W m-2 sr-1. The experiments also predict that it will be possible to increase these values to more than 60 kW/mm2 and 3x10(11) W m-2 sr-1.     

SNS stripper foil development program

When the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL) becomes fully operational it will be the world's highest intensity neutron spallation source. The charge-exchange injection section in the accumulator ring, which strips the injected H⁻ beam to H⁺, requires a stripper foil 260 μg/cm² thick, 12 mm wide, a height of at least 20 mm, and support from just the top edge. The foil will get very hot due to the 1.4 MW, 1 GeV, 60 Hz H⁻ beam that passes through the foil, in addition to the 7–10 foil traversals each circulating proton makes through the foil. The planned upgrade to 3 MW beam power presents an even greater challenge. To meet this challenge a diamond foil development program has been underway at ORNL since 2001. Both microcrystalline and nanocrystalline foils have been developed and tested. In this paper we will discuss the SNS injection process, stripper foil requirements, and results from the diamond foil development and testing program.