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Search Results: 1 - 10 of 208475 matches for " L. Shekhtman "
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Zero-bias Anomaly of Tunneling into the Edge of a 2D Electron System
L. Shekhtman,L. I. Glazman
Physics , 1995, DOI: 10.1103/PhysRevB.52.R2297
Abstract: We investigate the electron tunneling into the edge of a clean weakly interacting two-dimensional electron gas. It is shown that the corresponding differential conductance $G(V)$ has a cusp at zero bias, and is characterized by a universal slope $|dG/dV|$ at $V=0$. This singularity originates from the electron scattering on the Friedel oscillation caused by the boundary of the system.
Spectral properties of operators that characterize ¢ “ ¢ (n)
B. L. Chalmers,B. Shekhtman
Abstract and Applied Analysis , 1998, DOI: 10.1155/s1085337598000542
Abstract: It is well known that the identity is an operator with the following property: if the operator, initially defined on an n-dimensional Banach space V, can be extended to any Banach space with norm 1, then V is isometric to ¢ “ ¢ (n). We show that the set of all such operators consists precisely of those with spectrum lying in the unit circle. This result answers a question raised in [5] for complex spaces.
High pressure operation of the triple-GEM detector in pure Ne, Ar and Xe
A. Bondar,A. Buzulutskov,L. Shekhtman
Physics , 2001, DOI: 10.1016/S0168-9002(01)01369-9
Abstract: We study the performance of the triple-GEM (Gas Electron Multiplier) detector in pure noble gases Ne, Ar and Xe, at different pressures varying from 1 to 10 atm. In Ar and Xe, the maximum attainable gain of the detector abruptly drops down for pressures exceeding 3 atm. In contrast, the maximum gain in Ne was found to increase with pressure, reaching a value of 100,000 at 7 atm. The results obtained are of particular interest for developing noble gas-based cryogenic particle detectors for solar neutrino and dark matter search.
A conception of the photon collider beam dump
L. I. Shekhtman,V. I. Telnov
Physics , 2004,
Abstract: Photon beams at photon colliders are very narrow, powerful and can not be deflected. For the beam dump at the TESLA-like collider we suggest to use a long gas (Ar) spoiler in front of the water absorber, this solves the overheating and mechanical stress problems. The neutron background at the interaction point is estimated.
A concept of the photon collider beam dump
L. I. Shekhtman,V. I. Telnov
Physics , 2014, DOI: 10.1088/1748-0221/9/09/C09031
Abstract: Photon beams at photon colliders are very narrow, powerful (10--15 MW) and cannot be spread by fast magnets (because photons are neutral). No material can withstand such energy density. For the ILC-based photon collider, we suggest using a 150 m long, pressurized (P ~ 4 atm) argon gas target in front of a water absorber which solves the overheating and mechanical stress problems. The neutron background at the interaction point is estimated and additionally suppressed using a 20 m long hydrogen gas target in front of the argon.
First results from cryogenic avalanche detectors based on gas electron multipliers
A. Buzulutskov,A. Bondar,L. Shekhtman,R. Snopkov,Y. Tikhonov
Physics , 2003, DOI: 10.1109/TNS.2003.820633
Abstract: We study the performance of gaseous and two-phase (liquid-gas) cryogenic detectors of ionizing radiation, based on gas electron multipliers (GEMs). For the first time, high gas gains, exceeding 10^4, were obtained in pure He, Ar and Kr at low temperatures and the stable avalanche mode of operation was observed in the two-phase cryogenic detector in Kr. The electron avalanching at low temperatures, in the range of 120-300 K, is systematically studied.
Cryogenic avalanche detectors based on gas electron multipliers
A. Bondar,A. Buzulutskov,L. Shekhtman,R. Snopkov,Y. Tikhonov
Physics , 2004, DOI: 10.1016/j.nima.2004.01.060
Abstract: We study the performances of gaseous and two-phase (liquid-gas) cryogenic detectors of ionizing radiation based on gas electron multipliers (GEMs) and operated in an avalanche mode in pure noble gases. The gas amplification in He, Ar and Kr is systematically studied at low temperatures, using triple-GEM multipliers. High gains, exceeding 10^4, were obtained in these gases in the range of 120-300 K. Stable electron avalanching was demonstrated in a saturated Kr vapor in the two-phase mode. These results are relevant for understanding basic mechanisms of electron avalanching at low temperatures and for applications in cryogenic particle detectors, in particular in dark matter and solar neutrino detectors.
Study of ion feedback in multi-GEM structures
A. Bondar,A. Buzulutskov,L. Shekhtman,A. Vasiljev
Physics , 2002, DOI: 10.1016/S0168-9002(02)01763-1
Abstract: We study the feedback of positive ions in triple and quadruple Gas Electron Multiplier (GEM) detectors. The effects of GEM hole diameter, detector gain, applied voltages, number of GEMs and other parameters on ion feedback are investigated in detail. In particular, it was found that the ion feedback is independent of the gas mixture and the pressure. In the optimized multi-GEM structure, the ion feedback current can be suppressed down to 0.5% of the anode current, at a drift field of 0.1 kV/cm and gain of 10^4. A simple model of ion feedback in multi-GEM structures is suggested. The results obtained are relevant to the performance of time projection chambers and gas photomultipliers.
Triple GEM operation in compressed He and Kr
A. Bondar,A. Buzulutskov,L. Shekhtman,V. Snopkov,A. Vasiljev
Physics , 2002, DOI: 10.1016/S0168-9002(02)01414-6
Abstract: We study the performance of the triple GEM (Gas Electron Multiplier) detector in pure noble gases He and Kr at high pressures, varying from 1 to 15 atm. The operation in these gases is compared to that recently studied in Ne, Ar and Xe. It turned out that light noble gases, He and Ne, have superior performance: the highest gain, approaching 10^5, and an unusual gain dependence on pressure. In particular, the maximum gain in He and Ne does not decrease with pressure, in contrast to Ar, Kr and Xe. These results are of high relevance for understanding basic mechanisms of electron avalanching in noble gases and for applications in cryogenic particle detectors, X-ray imaging and neutron detectors.
Performance of the triple-GEM detector with optimized 2-D readout in high intensity hadron beam
A. Bondar,A. Buzulutskov,L. Shekhtman,A. Sokolov,A. Vasiljev
Physics , 2001,
Abstract: Multiple-GEM detectors are considered to be good candidates for tracking devices in experiments with high hadronic background. We present the results of the triple-GEM detectors beam test in a high intensity pion beam. The detectors had an optimized two-dimensional readout with minimized strip capacitance. Such optimization permitted the starting point of the efficiency plateau down to a gain of 5000. The probability of GEM discharges induced by heavily ionizing particles has been measured as a function of gain: at a gain of 20000 it amounts to 10^(-11) per incident particle. Such a value will ensure safe operation of the detector in the conditions of forward region of the LHC experiments.
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