The Optimization of CsI(Tl)-PIN Photodiode for High-Energy Gamma-Ray Detection

Abstract

A Monte Carlo simulation was performed to induce optimized parameters for CsI(Tl) crystals and large area PIN phohtodiode detectors for applications in high energy gamma ray spectroscopy. In order to derive the optimum parameters we used a Trade-Off procedure between the deposition energy and light transmission efficiency, while varying the detector thickness. Moreover, it was found that the surface treatment of the crystal in the photodiode is also an important factor for good light transmission. The tests were performed using a low noise charge-sensitive preamplifier and a pulse shape amplifier. Concerning the operating condition of the system, it is necessary to shape the time and reverse the bias voltage in order to provide another minimization of noise for the system. In order to maximize the light output from the crystal, the crystal geometry, crystal wrapping, optical bonding and matching to the PIN photodiode were all optimized. With a fixed crystal height of 5 cm, it was best to grind the sides and the top surface of the crystal on the front facing sides of the external reflectors, resulting in about a 14.5% enhancement compared with polishing all the sides and top.

Approaching the Theoretical Light Yield Limit in CsI (Tl) Scintillator Single Crystals by a Low-Temperature Solution Method

“…For 146.7 ppm Tl doped CsI crystal, the absorption edge at 320 nm is observed. The transmittance is very high and can approach to 81.8% at 800 nm (Figure a) for a 2.5 mm sample, which is similar to the value reported by other groups. , The theoretical limit value of transmittance can be calculated to be around 85% according to equations discussed by Zhu et al by using the refraction index of CsI­(Tl) (1.78–1.8). − The measured transmittance approaches this theoretical limit, indicating very good optical quality, and thus can lead to a high light output. For 5.1 ppm of Tl doped CsI crystal, the absorption edge is at 240 nm, which is very close to the theoretical value .…”

A ΔE-E semiconductor detector combined with CsI(Tl) crystal for monitoring the relative electrons flux generated in interaction of accelerated nuclei beam on thin targets

“…It is worth noting the fact that the front faces and the lateral faces of the CsI(Tl) crystal surface are polished. In this way the efficiency of light collection on PIN photodiode will be better [6]. Between Si PIN photodiode and the inorganic scintillator an optical interface is used (plasmol from Bicron Corporation) to enssure a good optical contact.…”