Abstract
Silicon neutron detectors can operate at low voltage and come with ease of fabrication and the possibility of integration of readout electronics and thus are attractive from an application point of view. In this paper, we have studied thermal neutron capture by silicon diodes coated with boron carbide (B4C). One of the surfaces of the diodes was covered with either natural B4C (natB4C) or with enriched B4C (enB4C). We have investigated: (a) the effect of increase in the sensitive area of the surface of the diode covered with B4C on the neutron detection efficiency and (b) the effect of enrichment of 10B in B4C. The difference in 10B in natB4C (16 at.% in the deposited film) and enB4C ( 79 at.% in the deposited film) leads to about three times increase in detection efficiency of the same detector. For the given experimental conditions, we do not observe a direct relationship between increase in the surface area and the detection efficiency. Energy spectra obtained by Geant4 simulations support the experimental observation of finding no direct relation between increase in the surface area and the detection efficiency.
Highlights
In past decades, semiconductor detectors have been regarded as an interesting alternative to be used for thermal neutron detection
The energy spectrum obtained from the planar detector Test Pad coated with enriched B4C without exposure to the neutron beam gives an idea of the background radiation in absence of the neutron beam
Pad coated with enriched B4C, simulations are done at thickness of N doped layer = 1.1 μm. (b) patterned detector Test 100 coated with enriched B4C, simulations are done at thickness of N doped layer = 1.5 μm. (c) patterned detector Test T35 coated with enriched B4C, simulations are done at thickness of N doped layer = 1.5 μm
Summary
Semiconductor detectors have been regarded as an interesting alternative to be used for thermal neutron detection. In order to capture a thermal neutron in a solid state detector e.g., a diode, a neutron converter material needs to be in close contact with the detector This is achieved by either fabricating the detector from a neutron converter semiconductor like BN, LiSe, LiInSe2 [1,2,3] or depositing a separate layer of neutron converter material on the surface of the diode [4,5,6]. In the former case, the reaction products are created within the sensitive volume of the diode and generate the signal. A key part of our study is to simulate the neutron interaction with the same detectors with Geant4 [19,20,21], compare it with the experimental results and understand the dependence of properties of the detectors, such as the thickness of the neutron converter layer and N doped region (explained in Section 2.1) on the detector response and detection efficiency
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