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181.
R. E. Tribble F. Abegglen G. Chubarian H. L. Clark G. Derrig G. Kim D. May G. A. Souliotis G. Tabacaru 《The European physical journal. Special topics》2007,150(1):255-258
The Cyclotron Institute at Texas A&M University is carrying out an upgrade project
which will lead to accelerated radioactive ion beams at intermediate energies. The project
involves recommissioning a K150 cyclotron for acceleration of stable beams which will be used
to produce radioactive ions. Both light-ion and heavy-ion guides will be used
to stop and transport the radioactive ions to a charge breeding electron cyclotron resonance ion
source. Following charge breeding, highly-charged ions will be injected into the K500 cyclotron,
accelerated and then transported to existing equipment to carry out experiments. 相似文献
182.
G. A. Souliotis A. L. Keksis B. C. Stein M. Veselsky M. Jandel D. V. Shetty S. N. Soisson S. Wuenschel S. J. Yennello 《The European physical journal. Special topics》2007,150(1):325-327
Recent efforts to produce and separate neutron-rich rare
isotopes in peripheral collisions below the Fermi energy are
presented. The experiments have been performed at the Cyclotron
Institute of Texas A&M University employing beams from the K500
Superconducting Cyclotron. Two magnetic separators were used: the
MARS recoil separator and the Superconducting Solenoid Line (BigSol
Line). An enhanced production of neutron-rich nuclides in comparison
with high-energy fragmentation mechanisms has been observed and
attributed to the role of the N/Z and the nuclear periphery of the
target. From a practical viewpoint, these reactions below or around
the Fermi energy offer a novel way to access very neutron-rich rare
isotopes. The experience obtained in the production of rare isotope
beams (RIB) below the Fermi energy will be exploited in the ongoing
RIB upgrade of the Cyclotron Institute that will involve production,
stopping and reacceleration of rare isotopes. 相似文献
183.
A. Andrighetto C. M. Antonucci S. Cevolani C. Petrovich M. Santana Leitner 《The European Physical Journal A - Hadrons and Nuclei》2006,30(3):591-601
The target system is one of the key issues for the facilities aimed at the production of neutron-rich radioactive ion beams.
In the framework of the SPES project (Study for the Production of Exotic Species), the possibility of using a target configuration
with a proton beam (40MeV, 0.2mA) directly impinging on multiple uranium carbide disks is investigated. The 238U fission fragments constitute the source for the exotic beams and for this purpose the disks are placed inside a graphite
box at 2000 °C. The target is split into several thin disks in order to allow the cooling of the system by thermal radiation. In this way
about ∼ 1013 fissions s
-1 are obtained with a relative simple system and with relative low costs. Further steps have been performed compared to previous
publications and now all the main parameters of the system have been analysed by means of calculation codes: the fission rates
and the fission fragment distribution; the power deposition and the thermal analysis; the thermo-mechanical behaviours of
the disks; the effusive and diffusive extraction release properties of the target. 相似文献
184.
J.A. Nolen 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):255-261
There are several nuclear physics laboratories in North America that have on-going research using energetic and stopped radioactive
beams. These include the large ISOL-type programs ISAC at TRIUMF and HRIBF at Oak Ridge and the in-flight fragmentation program
at the NSCL of Michigan State University. There are also smaller, more specialized, programs using a variety of techniques
at the 88-inch cyclotron of Berkeley, ATLAS at Argonne, the Cyclotron Institute of Texas A&M University, the Nuclear Structure
Laboratory at Notre Dame University, and the Nuclear Structure Laboratory at SUNY/Stony Brook. There are also three projects
on the horizon in North America for new capabilities in both the near term and more distant future. The intensities of the
in-flight fragment beams at the NSCL will be increased dramatically very soon as the Coupled Cyclotron Project will be completed
and commissioned for research by mid-2001. A new project, ISAC-II, has been approved in Canada. For the longer term, the United
States is considering construction of a major new facility, the Rare Isotope Accelerator (RIA), which would have a very high-intensity
heavy-ion driver linac. The RIA facility is proposed to utilize both ISOL and in-flight production mechanisms.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
185.
Ch. E. Düllmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):75-80
In recent years, the concept of physical preseparation of single atoms was
introduced into the field of transactinide chemistry. In this approach, the
transactinide element of interest is isolated in a physical recoil separator
and then extracted from this machine. The beam as well as the unwanted
reaction products are strongly suppressed, allowing for the investigation of
new chemical systems that were not accessible before.
The most important aspects of the technique are discussed and the advantages
for chemistry experiments with transactinides are presented, using some of
the chemical studies that were performed with preseparated isotopes as
examples. 相似文献
186.
The distribution of radioactive pollutants, such as ~(222)Rn, U, Th and ~(226)Ra in the air, sur-face waters, soils and crops around the Lincang uranium mine, Yunnan Province, China, is studiedThe mechanical, geochemical and biogeochemical processes responsible for the transport andfate of the radioactive elements are discussed based on the monitoring data. The pollutants con-centrations of effluents from the mine tunnels were dependent on pH and SO_4~(2-) which were con-trolled by biochemical oxidation of sulfide in the ore/host rocks. Radon anomalies in air reached 4km from the tailings pile depending on radon release from the site, topography and climate. ~(238)Uand ~(226)Ra abnormities in stream sediments and soil were 40-90 cm deep and 790-800 m awaydownstream. Anomalies of radioactive contaminants of surface watercourses extended 7.5-13km from the discharge of effluents of the site mainly depending on mechanical and chemical proc-esses. There were about 2.86 ha rice fields and 1.59 km stream sediments contaminated. Erosionof tailings and mining debris with little or no containment or control accelerated the contaminationprocesses. 相似文献
187.
产生放射性核束的在线同位素分离装置的靶系统设计是整个装置产生效率的关键环节.在ORNL的窄高斯分布的离子注入模型的基础上,研究了不同的靶的几何形状和尺寸、不同的温度条件、半衰期不同的放射性核素等对释放时间特性的影响,这对设计具有快速释放过程的靶系统,具有直接的实用价值.基于德国ZFK关于表面物理的实验测量数据,用MonteCarlo统计的方法来模拟放射性核素从靶材料表面到在线离子源的电离室的传输过程,对大量的放射性核素–传输管材料组合,和不同尺寸的传输管进行了统计计算,从这些统计计算中得到了可用于传输管工程设计的图表和经验公式. 相似文献
188.
189.
放射性核素浓度的确定是放射性事故应急救援和辐射防护等工作的基础和前提,是放射性事故应急救援的重要组成部分.在一维扩散模型的基础上,建立了放射性核素瞬时污染点源三维扩散模型、连续污染点源三维扩散模型、连续污染点源三维扩散稳态模型,并编写程序,实现了对放射性核素污染扩散的快速仿真分析,较好模拟了水体中放射性核素的扩散趋势.研究结果在核事故应急救援过程中,可为相关部门制定救援方案及应急决策提供科学依据. 相似文献
190.