Ultra-low background alpha particle counter using pulse shape analysis

被引:0
作者
Warburton, WK [1 ]
Dwyer-McNally, B [1 ]
Momayezi, M [1 ]
Wahl, JE [1 ]
机构
[1] Xray Instrumentat Associates, Newark, CA 94560 USA
来源
2004 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOLS 1-7 | 2004年
关键词
D O I
暂无
中图分类号
TL [原子能技术]; O571 [原子核物理学];
学科分类号
0827 ; 082701 ;
摘要
The need to measure alpha particle emissivities at levels below 0.005 alpha/cm(2)-hr is becoming increasingly important in fundamental physics experiments (e.g. neutrino and rare decay measurements), environmental monitoring, nuclear activities monitoring and semiconductor packaging materials,. Present counters can barely reach this level, being limited both by cosmic ray events and by their own alpha emissions. Here we report a detector capable of measurements at 0.00005 alpha/cm(2)-hr using a large electrode ionization chamber with digital pulse shape analysis to locate the point of emission of each alpha particle. Filled with 1 atm N-2, the counter is essentially blind to both environmental gamma-rays and cosmic ray ration showers, so its background becomes limited by the ability of the pulse shape analysis to distinguish different points of alpha particle origin. The counter's geometry intentionally exaggerates differences between signals originating from its different surfaces, with an inter-electrode separation D over 3 times the alpha particle range L. Since signal risetimes equal charge drift times, anode events have 8-10 mu s risetimes, while sample event risetimes are 30-35 is and readily distinguished. Integrated charge also increases with drift length, producing a 2 to 1 difference between sample and anode events. Applying both risetime and amplitude cuts distinguishes between sample and anode emitted alpha particles at about 1 part in 1000. A guard electrode surrounding the anode allows alpha particles from the counter's sidewalls to be rejected at a similar ratio, so that essentially only alpha particles emanating from the sample are finally counted.
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页码:577 / 581
页数:5
相关论文
共 7 条
  • [1] [Anonymous], 1987, IEEE T J MAGN JAPAN, DOI DOI 10.1109/TJMJ.1987.4549593
  • [2] BAUMANN R, 2001, 01054118AXFR
  • [3] Knoll G. F., 2000, Radiation Detection and Measurement, V3rd, P789
  • [4] *ORTEC, EG G ORTEC CAT MOD P
  • [5] *SPECTR SCI INC, BEST COMM AV INSTR M
  • [6] Warburton W K, 2004, US Patent, Patent No. [US6732059 B2, 6732059]
  • [7] Young M., 1989, TECHINCAL WRITERS HD