In situ radiation test of silicon and diamond detectors operating in superfluid helium and developed for beam loss monitoring

Abstract

a b s t r a c tAs a result of the foreseen increase in the luminosity of the Large Hadron Collider, the discrimination between the collision products and possible magnet quench-provoking beam losses of the primary proton beams is becoming more critical for safe accelerator operation. We report the results of ongoing research efforts targeting the upgrading of the monitoring system by exploiting Beam Loss Monitor detectors based on semiconductors located as close as possible to the superconducting coils of the triplet magnets. In practice, this means that the detectors will have to be immersed in superfluid helium inside the cold mass and operate at 1.9 K. Additionally, the monitoring system is expected to survive 20 years of LHC operation, resulting in an estimated radiation fluence of 1 Â 10 16 proton/cm 2 , which corresponds to a dose of about 2 MGy. In this study, we monitored the signal degradation during the in situ irradiation when silicon and single-crystal diamond detectors were situated in the liquid/superfluid helium and the dependences of the collected charge on fluence and bias voltage were obtained. It is shown that diamond and silicon detectors can operate at 1.9 K after 1 Â 10 16 p/cm 2 irradiation required for application as BLMs, while the rate of the signal degradation was larger in silicon detectors than in the diamond ones. For Si detectors this rate was controlled mainly by the operational mode, being larger at forward bias voltage.

Signal amplification in multistage charge collection process in Si detectors in situ irradiated at superfluid helium temperature

“…This work extends the analysis of the experimental data received at CERN [4,5] and is focused on the effect of signal amplification in irradiated Si detectors operating at 1.9 K. The study is based on the previously proposed model of a two-stage charge collection process [6]:…”

“…The details of the in situ irradiation test were described in [4,5]. Among the p + -n-n + detectors studied in the test, the sample with a sensitive area of 1 mm 2 processed on 300 μm thick wafer with a resistivity of 10 kΩcm was chosen for the study of charge collection via an analysis of the current pulse response using the tools and approaches of TCT.…”

Properties of Diamonds and Their Application in Photodetectors

“…This type of passivation is reversible after exposure to visible light Fig. 16 Current-voltage characteristics of an irradiated diamond detector sample at 1.9 K for a fluence of 1Â10 16 p/cm 2 , and at room temperature for a fluence of 1.2Â10 16 p/cm 2 [66].…”

“…Kurfürst et al [66] measured the current-voltage characteristics of a diamond photodetector after irradiation at 1.9 K and at room temperature. In the former, there is no significant change in the current, which remained in the range of tens of pA for a fluence of 1Â10 16 p/cm 2 .…”

Excitons and fundamental transport properties of diamond under photo‐injection

“…This mechanism is utilized in diamond detectors that measure charge carriers collected at electrodes after transport over macroscopic distances in the intrinsic layer (). Despite their use under cryogenic conditions (), the role of exciton formation in such diamond detectors seems to be unexplored. Furthermore, impurity‐vacancy centers in diamond have attracted rapidly increasing attention for use as single‐photon emitters or spin qubits ().…”