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.
The NUSTAR experiments to be carried out as the part of the FAIR program (Facility for Antiproton and Ion Research) now under development in GSI, Germany, require unique spectrometers for heavy ions, for an energy range between a hundred keV up to hundreds of MeV. These spectrometers are constructed on the basis of silicon double sided detectors capable of providing simultaneously the energy spectrum of the particles and the position of hit points. The double sided Si strip detectors for high resolution ion spectroscopy and tracking were developed by the PTI-RIMST consortium. Reduced sized detectors were studied with alpha-particles from a 238 Pu source to define the spectral response of their p + side. The energy resolution was measured and found to be the highest, 9.6 keV, in the p + strips area. The energy spectrum for the particles hit at the interstrip gap was shown to be much broader and have a maximum at the low energy edges. In this study the alpha-particle spectra were measured on the p + side of strip detector and their shape was found to depend on the p + strip structure and potential distribution under the strip and in the interstrip gap, where the surface is passivated by SiO 2 layer. Therefore, the 2D potential distribution in the interstrip gap was simulated and interpreted through the effective entrance window for alpha-particles. The calculated spectrum of a detector from alpha-particle source has a shape specific to the experimental detector spectral response, i.e., the peak at low energies. These findings are to be taken into account in the analysis of short range particle spectra and may well contribute to further development of spectroscopic single sided and double sided Si strip detectors to be used in investigations in nuclear physics.
This study focuses on evaluating the properties of voltage termination structure (VTS) with multiple guard rings in n+-p-p+ silicon detectors with Al2O3 field isolation films processed by Atomic Layer Deposition (ALD) method. The dependences of the ring potential over the guard rings with respect to bias voltage were studied experimentally and compared with the results of simulations using negative charge Qf in Al2O3 films as a parameter. The agreement of the experimental and calculated punch-through voltages switching the ring operation verified that the punch-through model built for the p+-n-n+ detectors passivated with positively charged SiO2 layers is also applicable for the n+-p-p+ detectors with Al2O3 field isolator with negative charge polarity. The results indicated an efficient potential distribution over the VTS rings. The amount of the oxide charge was shown to be an essential parameter for the detector performance. From the comparison of the experimental data and simulations for Si detector with the used design and processing technology, Qf of -(4–7)×1011 cm−2 was found to be the value explaining the properties of VTS in the detector under study. The simulations showed that Qf of -7×1011 cm−2 is an upper limit critical for the appearance of high electric field regions in the VTS. The increase in the silicon resistivity to 20 kωcm was found to be an efficient way to reduce the electric field below the value initiating the carrier avalanche multiplication.
The presented paper is focused around radiation damage of silicon material under the different ions irradiation. The ion total energy range is 0.7 GeV for 7Li to 208 GeV for 208Pb. The results of TRIM modeling for the set of six ions are presented. The extracted information about vacancy production allows making first assumptions of the Si degradation dependence on mass and energy of the incident ion.
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