College Park, Maryland      June 6 - 10 , 2004

TP24: Optimization of a Gd-CsI neutron converter for a GEM based neutron detector

R. Berliner (Instrumentation Associates Inc.; University of Michigan Department of Nuclear and Radiological Sciences)

In a prototype SNS neutron detector, a CsI screen, covering a layer of metallic Gd, produces low energy secondary electrons (SE) that are then amplified and localized by a Gaseous Electron Multiplier1 (GEM) followed by a dual charge-division X-Y pickup anode. The efficiency of the detector is critically dependent on the thickness of the Gd and CsI layers that make up the active portion of the neutron converter. The geometry of the neutron converter for the neutron GEM has been optimized by Monte-Carlo calculations of primary electron production in the Gd and SE production in the CsI layers. Benchmark calculations with a modified version of Penelope,2 a standard Monte-Carlo electron transport code, were used to reproduce the results of earlier detailed model analysis of SE production.3 These calculations were then extended to analyze realistic GEM neutron detector geometries. The results of these calculations and comparison to experimental results with the GEM neutron detector will be presented.

Supported by the DOE SBIR program under grant DE-FG02-03ER83685.

1. F. Sauli, GEM, a new concept in electron amplification in gas detectors, Nuc. Inst. And Meth. A386 (1997) 531-534.
2. J. Sempau, J.M. Fernandez-Varea, E. Acosta and F. Salvat: Experimental benchmarks of the Monte Carlo code PENELOPE. Nuclear Instruments and Methods B 207 (2003) 107-123.
3. A. Akkerman, A. Gibrekhterman, A. Breskin and R. Chechik, J. Appl. Phys. 72 (11) (1992) 5429-5436.

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