Thermal and fast neutron detection in chemical vapor deposition single-crystal diamond detectors

Abstract

Recently, a compact solid-state neutron detector capable of simultaneously detecting thermal and fast neutrons was proposed [M. Marinelli et al., Appl. Phys. Lett. 89, 143509 (2006)]. Its design is based on a p-type/intrinsic/metal layered structure obtained by Microwave Plasma Chemical Vapor Deposition (CVD) of homoepitaxial diamond followed by thermal evaporation of an Al contact and a ⁶LiF converting layer. Fast neutrons are directly detected in the CVD diamond bulk, since they have enough energy to produce the ¹²C(n, α)⁹Be reaction in diamond. Thermal neutrons are instead converted into charged particles in the ⁶LiF layer through the ⁶Li(n, α)T nuclear reaction. These charged particles are then detected in the diamond layer. The thickness of the ⁶LiF converting layer and the CVD diamond sensing layer affect the counting efficiency and energy resolution of the detector both for low- (thermal) and high-energy neutrons. An analysis is carried out on the dynamics of the ⁶Li(n, α)T and the ¹²C(n, α)⁹Be reactions products, and the distribution of the energy released inside the sensitive layer is calculated. The detector counting efficiency and energy resolution were accordingly derived as a function of the thickness of the ⁶LiF and CVD diamond layers, both for thermal and fast neutrons, thus allowing us to choose the optimum detector design for any particular application. Comparison with experimental results is also reported

Using LiF crystals for high-performance neutron imaging with micron-scale resolution

“…This high quantity of neutrons with energy in the range of 1 eV-100 keV gives hope for successful thermal neutron imaging using LiF detectors due to the higher efficiency of their absorption compared with MeV neutrons. It is also necessary to mention that, recently, LiF films embedded with Li 6 have been successfully used as converters of neutrons in tokomak experiments with thermonuclear neutrons [41,42] . The subsequent results give confidence that LiF detectors could be successfully used for high-resolution imaging of plasma neutron sources.…”

Development of On-Line Tritium Monitor Based Upon Artificial Diamond for Fusion Applications

“…1 shows a sketch of the tritium monitor with the indication of main particle reactions. A more accurate description of such Li-Diamond devices in term of characteristic and performances can be found in [3].…”

Superconducting Strips: A Concept in Thermal Neutron Detection

“…It must be noted that "partial" transitions not involving the entire width of the strip may also take place, i.e., the so called self-recovering pulses. Since the voltage drop occurs only across the normal zone, it follows that the maximum value of the voltage amplitude is given by V = 2r c ρJ c (3) with ρ the normal state residual resistivity of the material and where J c is the local transport critical current density. Using reasonable estimates for typical material parameters of elemental superconductors, one obtains minimum values for r c and V in the order of 1 µm and 10 mV, respectively.…”

“…In either case, neutron detection is achieved by means of the ionization energy loss suffered by the secondary charged products of the reaction which, in the simplest cases, takes place in a gas chamber with an appropriate electrode configuration. Typical examples of gas chambers are 3 He and BF 3 tubes for thermal neutrons and fission counters for both thermal and fast neutrons.…”