The REX-ISOLDE project

The Radioactive Beam Experiment REX-ISOLDE [1–3] is a pilot experiment at ISOLDE (CERN) testing the new concept of post acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In order to prepare the ions for the experiments singly charged radioactive ions from the on-line mass separator ISOLDE will be cooled and bunched in a Penning trap, charge bred in an electron beam ion source (EBIS) and finally accelerated in the LINAC. The LINAC consists of a radiofrequency quadrupole (RFQ) accelerator, which accelerates the ions up to 0.3 MeV/u, an interdigital H-type (IH) structure with a final energy between 1.1 and 1.2 MeV/u and three seven gap resonators, which allow the variation of the final energy. With an energy of the radioactive beams between 0.8 MeV/u and 2.2 MeV/u a wide range of experiments in the field of nuclear spectroscopy, astrophysics and solid state physics will be addressed by REX-ISOLDE. This revised version was published online in July 2006 with corrections to the Cover Date.     

室温CH腔体的单元腔近似优化

 CH（cross-bar H-type structure）结构是近几年提出的一种适用于低β的新型DTL(drift tube linac)加速结构,同IH（interdigital H-type structure）结构相比,CH结构可以工作在更高的频率（150~700 MHz）下,从而可以得到更高的输出能量（150 MeV）。由于DTL腔体为准周期结构,通过对单元腔的MWS(microwave studio)模拟及优化,得到了工作频率为350 MHz,单核能从6 MeV到66 MeV时的腔体并联阻抗及其它腔体参数,并对腔体单元数对腔体特性参数及谐振频率的影响做了定性分析。分析表明：对于CH结构,其有效并联阻抗远大于传统的DTL结构,对于350 MHz的工作频率,在6 MeV时将近100 MΩ/m,即使在能量高达66 MeV时,其有效并联阻抗也大于40 MΩ/m;单元腔近似是一种非常有效的分析DTL加速结构的方法,单元腔计算结果和整腔计算结果相比,谐振频率的相对偏差小于1%; 对于有效并联阻抗的计算,误差也在10%之内。     

束团压缩用踢波器的模型腔

 为了提高中子产额,法兰克福强中子源采用Mobley型束团压缩器来增强打靶时质子流的密度,其入口处由射频踢波器实现微脉冲的偏转,踢波器由一对电偏转板和串联电感线圈组成谐振腔体。考虑到高频下寄生电容效应、导体腔壁对线圈电感的影响以及涡流效应对线圈交流电阻的影响,对一台模型腔的射频特性进行了理论预测。对腔体内电磁场分布进行了数值模拟,并利用电容微扰法进行了冷模测量。针对谐振频率、品质因数和并联分路阻抗等参数,分析比较了理论计算、数值模拟及冷模测量的结果,总结得出射频踢波器的有效设计方法。     

Application of headspace solid phase microextraction to qualitative and quantitative analysis of tobacco additives in cigarettes

Cigarettes may contain up to 10% by weight additives which are intended to make them more attractive. A fast and rugged method for a cigarette-screening for additives with medium volatility was developed using automatic headspace solid phase microextraction (HS-SPME) with a 65 microm carbowax-divinylbenzene fiber and gas chromatography-mass spectrometry (GC-MS) with standard electron impact ionisation. In three runs, each cigarette sample was extracted in closed headspace vials using basic, acidic and neutral medium containing 0.5 g NaCl or Na2SO4. Furthermore, the method was optimized for quantitative determination of 17 frequently occurring additives. The practical applicability of the method was demonstrated for cigarettes from 32 brands.     

Light-Ion Linear Accelerator for the NICA Project

Physics of Particles and Nuclei Letters - A joint team from the Joint Institute for Nuclear Research (JINR) (Dubna, Russia) and Bevatech GmbH (Frankfurt-am-Main, Germany) has been developing a new...