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Kurfurst C.,CERN | Dehning B.,CERN | Sapinski M.,CERN | Bartosik M.R.,CERN | And 14 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

As 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 1×1016 proton/cm2, 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 1×1016 p/cm2 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. © 2015 Elsevier B.V. All rights reserved. Source


Eremin V.,RAS Ioffe Physical - Technical Institute | Kiselev O.,Helmholtz Center for Heavy Ion Research | Egorov N.,Research Institute of Material Science and Technology | Eremin I.,RAS Ioffe Physical - Technical Institute | And 3 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

Construction of new accelerating facilities to investigate reactions with heavy ions requires upgrading of the Time-of-Flight (TOF) systems for on-line ion identification. The requested time resolution of the TOF system developed for Super FRagment Separator in the frame of the FAIR program at GSI, Germany, is in the range of tens of picoseconds, which can be realized by using planar silicon detectors. Such resolution will allow characterization of relativistic ions from Lithium to Uranium. However, fast timing of heavy ions with semiconductor detectors is expected to be limited by the so-called plasma effect due to a high concentration of electron-hole pairs in tracks. Here the results of the experiment with relativistic 197Au ions (the energy of 920 MeV per nucleon) obtained with Si detectors are described, which showed the TOF time resolution around 14 ps rms. The physical mechanism of charge collection from high-density penetrating tracks of relativistic heavy ions is considered and the analysis of timing characteristics is performed taking into account track polarization. Polarization is shown to have a strong influence on the formation of the leading edge of the detector current response generated by relativistic heavy ions, which allows us to explain the observed high time resolution. © 2015 Elsevier B.V. Source


Eremin V.,RAS Ioffe Physical - Technical Institute | Egorov N.,Research Institute of Material Science and Technology | Eremin I.,RAS Ioffe Physical - Technical Institute | Fadeeva N.,RAS Ioffe Physical - Technical Institute | Verbitskaya E.,RAS Ioffe Physical - Technical Institute
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

In the 1990s a suggestion was put forward that the space charge limited current mechanism is responsible for stabilization of the I-V characteristics in irradiated Si p-on-n detectors. This mechanism is switched on in the case of high concentration of radiation induced deep traps which via holes accumulation will reduce the electric field in the regions of breakdown. The present study shows that voltage terminating structure (VTS) consisting of the floating p + rings as a main element for stabilization of I-V characteristics in nonirradiated detectors is still active being irradiated to the fluence beyond space charge sign inversion. This characteristic of VTS can be accounted for by the double peak electric field distribution in heavily irradiated detectors and the punch-through mechanism of current flow between the floating p+ rings in the silicon bulk with high concentration of deep traps. It is shown that VTS operates as a potential divider up to the fluence of 1×10 15 neq/cm2 and it is at higher fluences that the detector stability is maintained only by the space charge limited current mechanism. © 2013 Elsevier B.V. Source


Verbitskaya E.,RAS Ioffe Physical - Technical Institute | Eremin V.,RAS Ioffe Physical - Technical Institute | Zabrodskii A.,RAS Ioffe Physical - Technical Institute | Dehning B.,CERN | And 5 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2015

Silicon and diamond detectors operated in a superfluid helium bath are currently being considered for the upgrade of the LHC beam loss monitoring system. The detectors would be installed in immediate proximity of the superconducting coils of the triplet magnets. We present here the results of the in situ irradiation test for silicon detectors using 23 GeV protons while keeping the detectors at a temperature of 1.9 K. Red laser (630 nm) Transient Current Technique and DC current measurements were used to study the pulse response and collected charge for silicon detectors irradiated to a maximum radiation fluence of 1×1016 p/cm2. The dependence between collected charge and irradiation fluence was parameterized using the Hecht equation and assumption of a uniform electric field distribution. The collected charge was found to degrade with particle fluence for both bias polarities. We observed that the main factor responsible for this degradation was related to trapping of holes on the donor-type radiation-induced defects. In contrast to expectations, along with formation of donors, acceptor-type defects (electron traps) are introduced into the silicon bulk. This suggests that the current models describing charge collection in irradiated silicon detectors require an extension for taking into account trapping at low temperatures with a contribution of shallow levels. New in situ irradiation tests are needed and planned now to extend statistics of the results and gain a deeper insight into the physics of low temperature detector operation in harsh radiation environment. © 2015 Elsevier B.V. Source


Eremin V.,RAS Ioffe Physical - Technical Institute | Verbitskaya E.,RAS Ioffe Physical - Technical Institute | Eremin I.,RAS Ioffe Physical - Technical Institute | Tuboltsev Yu.,RAS Ioffe Physical - Technical Institute | And 5 more authors.
Journal of Instrumentation | Year: 2012

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 238Pu 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 SiO2 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. © 2012 IOP Publishing Ltd and Sissa Medialab srl. Source

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