Quality Checking Of The Silicon Detectors For The Charged Particles Spectrometry

Full text: In the spectrometry of charged particles in nuclear experiments the semi-conductor silicon detectors are widely used. Before use of a detector in the experiment at the accelerator's beam it is necessary to know its resolution and thickness of the sensitive area. As a rule, the energy resolution of a detector is defined on the shape of α - spectra obtained from the reference α-source (for example, 226Ra). The thickness can be estimated on the electrical capacity of a detector or on the share of spectrum of the Compton electrons and β - spectrum from the radiative source 137Cs. [1]. However, as the practice has shown, these two characteristics are not enough for evaluation of the detector's quality. If a detector is used for spectrometry of the high-energy charged particles with large ranges in the material of a detector, it often appears that the resolution does not correspond to that in the spectra of α - particles from the α - source. Probably, this fact is connected with presence of dislocations and local structural infringements in the depth of the sensitive area of detector. Thus, it is very important to estimate previously the quality of detectors because as a rule the beam time of an accelerator is very expensive. Here we propose to test the detectors reaction before their utilization in experiments using the quasi-monochromatic neutron fluxes which are generated by the neutron generator via the reaction T(d,n)4He. These neutrons have rather large energy ( ∼ 14 MeV), which exceeds the thresholds of the (n,α)- and (n,p)- reactions on the silicon isotopes. As these reactions occur with the same probability in any point of the sensitive area of a detector, the whole volume of the detector will be tested, but not only the superficial part (as it occurs at use of the α- source). The procedure of testing is rather simple. Detector is connected with the spectrometric line: preamplifier, spectrometric amplifier and pulse multi-channel analyzer. The detector is placed at such distance from the source of fast neutrons, where the intensity of the aroused products of reactions is optimal. The method does not require a vacuum chamber for the detector. The typical time of the testing exposition makes some tens minutes at the neutron flux ∼ 1010 n/s in 4π and at the distance 'neutron source - detector' about 500 mm. The spectrum of the charged particles from the reaction (n,α) etc. is analyzed, and the shape of the peaks in the spectra allows one to estimate the true 'volumetric' energy resolution of the tested detector. References: 1. S. V. Artemov, G. A. Radyuk, A.A. Karakhodzhaev, Ya.S. Abdullaeva, and V. P. Yakushev. Method for Determining the Depleted Zone Thickness in Silicon Charged Particle Detectors, ISSN 1062-8738, Bulletin of the Russian Academy of Sciences: Physics, 2009, Vol. 73, No.4, pp. 502-505. (authors)