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TECHNI Informe resumido

Project ID: HPRI-CT-1999-50005
Financiado con arreglo a: FP5-HUMAN POTENTIAL
País: France

Development of the multi-PSPC, a very fast 2D neutron detector for small angle scattering applications

The Multi-PSPC is made of 128 Neutron Position Sensitive Proportional Counters (PSPC), mounted side by side in a detection plan which has a 1 m{2} sensitive area. It has been designed to overcome the count rate limitation of Multi Wire Proportional Chambers (MWPC) without compromising other detection parameters (efficiency, position resolution, and gamma suppression).

An intrinsic drawback of the Multi-PSPC is that the uniformity in the direction perpendicular to the tubes varies due to the variation of the gas thickness. This is not a limitation for applications, like Small Angle Neutron Scattering, where the neutron signals are generally spread over several tubes. A new PSPC had to be developed in collaboration with an industrial company. It has a length of 1m, an external diameter of 8 mm, and contains a gas mixture at a pressure of 15 bars. A fast electronics has been developed at the ILL to measure the position along the tube by charge division. It is based on the conversion into an address of the charge signals measured on both ends of the tubes.

The resolution obtained, 6 mm FWHM, is within the specifications (8mm), and the maximum count rate, above 3 MHz, is at least a factor 20 better than the maximum count rate sustainable with a MWPC. The detector has been installed on the D22 ILL instrument and is now used for routine experiments. This technique can ideally replace MWPCs traditionally used on SANS instruments, as it is cheaper and much faster. It could also be used on neutron reflectometers. The charge division electronics can be used on any type of particle detectors (neutron, X-Ray, MIP).

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Institut Laue-Langevin (ILL)
6 rue J. Horowitz
38000 Grenoble
France
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