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1.
A nonbubble chamber (NBC) setup, especially designed to perform a series of experiments, is described. The setup consists of a neutron missing-mass spectrometer coupled with a system of large electromagnetic shower detectors. In spite of its large dimensions (the sensitive surface and volume are 2.16 × 104 cm2 and 7.8 × 105 cm3, respectively), the neutron spectrometer has a time resolution of ±0.70 nsec FWHM, with ∼25% detection efficiency in the range (70–390 MeV) neutron kinetic energy. The time equalization between the various components of the neutron spectrometer has been established to within ±0.1 nsec. At present this is the most powerful and the most accurate high-energy neutron detector. The electromagnetic shower detector is based on the principle of simultaneous measurements of the spatial development of the electromagnetic cascade and of its energy release. This is obtained with nine elements of lead foil — spark chamber — plastic scintillator, all sandwiched together. The sensitive surface and volume of the electromagnetic shower detector are 1.45 × 104 cm2 and 7.2 × 105 cm3, respectively. 相似文献
2.
V. Bednyakov E. Khramov N. Russakovich A. Tonoyan 《Physics of Particles and Nuclei Letters》2007,4(6):491-496
We have investigated the possibility of reconstructing the top quark charge through measurement of its decay product charges
at the ATLAS detector. Verification of the hypothesis about alternative interpretation of top-quark experimental data has
been considered as well. The method of “semileptonic B-meson decay” was applied for reconstructing the b-jet charge. A statistical significance of more than 5σ can be achieved using this method after analyzing 1 fb−1 of the t̄t-pairs data. The analysis was carried out with HERWIG and PYTHIA generators and using the GEANT4 detector simulation software
package.
The text was submitted by the authors in English. 相似文献
3.
The Resistive Plate Chamber (RPC) has been developed in many application areas ever since its introduction, from high energy physics experiments to positron emission tomography. Such detectors can be coated with a Gd layer that enables them to detect thermal neutrons. Consequently these RPCs can be utilized for industrial and medical purposes. Here, we present the configuration of a resistive plate chamber which is utilized to detect thermal neutrons by employing GEANT4 Monte Carlo code. The response of the RPC was evaluated as a function of neutron energy in the GEANT4 Monte Carlo code. The simulation results are taken for incident neutron energy in the energy range from 25 meV to 100 meV. The detection efficiency was found to be between 10% and 20%, depending on the detector configuration, for incident thermal neutrons of 25 meV energy. 相似文献
4.
I. I. Belotelov A. O. Golunov I. A. Golutvin N. V. Gorbunov V. Yu. Karjavin Yu. T. Kiryushin A. Yu. Kamenev S. V. Khabarov V. V. Khabarov G. V. Mescheryakov K. P. Moissenz P. V. Moissenz S. A. Movchan V. V. Palichik V. V. Perelygin S. V. Shmatov D. A. Smolin A. V. Zarubin 《Physics of Particles and Nuclei Letters》2007,4(4):343-349
The aim of this work is to estimate the shower leakage from the CMS Endcap Hadron calorimeter (HE) due to electromagnetic
secondaries and punch-through in the region of the ME1/1 Forward Muon Station. Two configurations are considered: with and
without the CMS Endcap Electromagnetic calorimeter (EE). The experimental data have been taken during the combined beam test
of CMS subdetectors (HE, ME, RPC, DT) at the CERN H2 beam facility in 2004. Serial CSC chambers (ready for installation in
CMS) fully equipped with readout electronics have been exposed. Simulation of a beam test setup has been performed using the
GEANT4-based simulation software package OSCAR.
The text was submitted by the authors in English. 相似文献
5.
J. N. Abdurashitov V. N. Gavrin V. L. Matushko J. S. Nico A. A. Shikhin A. K. Thompson I. E. Veretenkin V. E. Yants 《Physics of Atomic Nuclei》2007,70(1):133-139
We discuss the development of a spectrometer based on full energy absorption using liquid scintillator doped with enriched
6Li. Of specific interest, the spectrometer is expected to have good pulse height resolution, estimated to lie in the range
10–15% for 14-MeV neutrons. It should be sensitive to flux rates from 10−6 cm−2 s−1 to 106 cm−2 s−1 above a threshold of 500 keV in an uncorrelated γ background of up to 104 s−1. We have constructed a pilot version of the detector using undoped liquid scintillator, and we report its present status.
The detector’s efficiency is determined by the volume of the scintillator (∼1.21) and is estimated to be 0.2–0.5% for 3-MeV
neutrons. The good pulse height resolution is achieved by compensation of the nonlinear light yield of the scintillator due
to the use of optically separated segments, which collect scintillations from each recoil proton separately. We demonstrate
here the response of the detector to neutrons from a Pu-α-Be source, whose energies range up to 10 MeV. Initial testing indicates a low threshold (≈600 keV) and good spectral response
after requiring a multiplicity of three segments. Such a spectrometer has applications for low-background experiments in fundamental
physics research, characterizations of neutron flux in space, and the health physics community.
The text was submitted by the authors in English. 相似文献
6.
A large stack of lead-emulsion sandwich detector assembly was flown over Hyderabad, India. High energy gamma rays at the float
altitude were unambiguously identified from the cascades they induced, and their energies reliably determined by improved
methods. From an analysis of 163 gamma rays of energy ≳ 30 GeV, it is found that the differential energy spectrum is represented
by the power lawJ
r
(E)= 129·4E
−2·62±0·12 photons m−2 sr−1sec−1 GeV−1 at an effective atmospheric depth of 14·3 g cm−2; this is the first reliable balloon measurement of atmospheric gamma rays in the energy range 40–1000 GeV. After correcting
for the gamma rays radiated by the primary cosmic ray electrons, the production spectrum of gamma rays, resulting from the
collisions of cosmic ray nuclei with air nuclei, at the top of the atmosphere isP
r
(E, 0)=8·2 × 10−4 E2.60±0.09 photons g−1sr−1sec−1 GeV−1. The atmospheric propagation of the electromagnetic component due to the cascade process is also derived from the gamma ray
production spectrum. 相似文献
7.
Resonance (frequency 1.4 cm(−1) changes induced in the four-photon optical spectrum of water by a millimeter-wave electromagnetic field are observed experimentally.
Comparison with the spectrum of ice in the range 0‒2 cm(1 shows that the action of such a field is of a structure-forming character.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 4, 266–268 (25 August 1998) 相似文献
8.
Different amounts of Li3PO4 were mixed to a fixed ratio of LiI:Li2WO4, ground and pelletised before subjected to sintering at 70°C for 7 days. XRD shows that the product formed after sintering
process is most likely Li6P4W8O32 due to peaks present at 10.6°, 22.4°, 24.0°, 24.4, 26.2°, 32.4° and 34.0°. Conductivity studies show that the sample with
25 wt.% Li3PO4 exhibits the highest room temperature conductivity of 3.42×10−3 Scm−1. Conductivity is expected to occur through channel-like structures which could have formed due to corner or edge sharing
of polyhedra. FTIR studies have shown the existence of WO4 tetrahedra and WO6 octahedral at 850 cm−1 and 952 cm−1, and phosphate tetrahedral at 564 cm−1, 700 cm−1, 890 cm−1 and 1030 cm−1. 相似文献
9.
S. A. Starodubtsev V. I. Kozlov A. A. Toropov V. A. Mullayarov V. G. Grigor’ev A. V. Moiseev 《JETP Letters》2012,96(3):188-191
The connection of short-term neutron bursts near sea level with the electric and geomagnetic atmospheric fields during thunderstorms in 2009–2011 has been experimentally studied. The data from the cosmic-ray spectrograph named after Kuzmin, an electrostatic fluxmeter, and a three-component fluxgate magnetometer in Yakutsk have been analyzed. It has been shown that short-term (no longer than 4 min) neutron bursts are due to negative lightning discharges. The bursts are detected at the ground level 1–3 km below thunderstorm clouds. In this case, the neutron flux is about 4 × 10−3 cm−2 s−1. The minimum energy of the neutrons that are efficiently detected by the monitor is about 10 MeV. It has been found that short-term neutron bursts are detected when the electric field strength reaches a threshold value of −16 kV/m. 相似文献
10.
The magnetoelectric (ME) effect is studied in composite two- and three-layer disk structures containing magnetostriction layers
of an amorphous FeNiSiC ferromagnet and a lead zirconate titanate piezoelectric layer. Due to a high magnetostriction (∼33
× 10−6) and a low saturation field (∼200 Oe), an FeNiSiC layer has a high piezomagentic coefficient, which results in an effective
ME coupling in low fields (∼25 Oe). The ME effect is ∼0.2 V cm−1 Oe−1 at a low frequency and increases to 11.9 and 13.2 V cm−1 Oe−1 when bending and in-plane mechanical vibrations are excited in a resonance manner in the structures at frequencies of ∼8.2
and ∼170.0 kHz, respectively. Structures containing amorphous FeNiSiC layers are promising for magnetic field transducers
and electric energy generators and converters. 相似文献
11.
We have recorded and investigated the ESR spectrum of vanadium-doped α-RbTiOPO4 single crystals in the temperature interval 77–300 K. Two types of structurally distinct centers, V1 and V2, with a 4:1 ratio
of the peak intensities were observed. The angular dependences of the resonance magnetic fields are described by a spin Hamiltonian
corresponding to axial symmetry with the parameters g
∥1=1.9305, g
⊥1=1.9565, A
∥1=−168.2×10−4cm−1, and A
⊥1=−54.3×10−4cm−1 for V1 centers and g
∥2=1.9340, g
⊥2=1.9523, A
∥2=−169.0×10−4cm−1, and A
⊥2=−55.2×10−4cm−1 for V2 centers. A model of a paramagnetic center is proposed: The vanadium ions replace titanium ions in two structurally
distinct positions Ti1 and Ti2 (V1 and V2 centers, respectively). The possibility that a VO2+ ion forms when α-RbTiOPO4 crystals and crystals of the KTP group (KTiOPO4, NaTiOPO4, α-and β-LiTiOPO4), studied earlier, are doped with vanadium is discussed.
Fiz. Tverd. Tela (St. Petersburg) 40, 534–536 (March 1998) 相似文献
12.
A. F. Bunkin V. G. Mikhalevich S. M. Pershin V. N. Streltsov 《Journal of Experimental and Theoretical Physics》2011,113(2):207-212
Mandelstam-Brillouin (MB) steady-state scattering in an elastic medium with a dense local zone inhomogeneity is considered
in the 1D approximation. It is shown that for a certain size of inhomogeneity, the scattered radiation spectrum contains individual
resonances whose frequencies depend on the elastic properties of microscopic inclusions. Experiments were performed using
coherent four-photon scattering spectroscopy in the range 0–1 cm−1 with a resolution of 0.06 cm−1 in specially processed distilled water and in an aqueous solution of α-chymotrypsin albumin. In both media, the presence
of MB resonances displaced is detected relative to the water resonance (≈0.25 cm−1) in different directions and corresponding to different types of microinclusions. 相似文献
13.
V. N. Dobrovolsky F. F. Sizov Y. E. Kamenev A. B. Smirnov 《Opto-Electronics Review》2008,16(2):172-178
A model of semiconductor hot electron bolometer (SHEB), in which electromagnetic radiation heats only electrons in narrow-gap
semiconductor without its lattice slow-response heating, is considered. Free carrier heating changes the generation-recombination
processes that are the reason of semiconductor resistance rise. It is estimated, that Hg0.8Cd0.2Te detector noise equivalent power (NEP) for mm and sub-mm radiation wavelength range can reach NEP ∼10−11 W at Δf = 1 Hz signal gain frequency bandwidth. Measurements performed at electromagnetic wave frequencies v = 36, 39, 55,
75 GHz, and at 0.89 and 1.58 THz too, with non-optimized Hg0.8Cd0.2Te antenna-coupled bolometer prototype confirmed the basic concept of SHEB. The experimental sensitivity Sv ∼2 V/W at T = 300 K and the calculated both Johnson-Nyquist and generation-recombination noise values gave estimation of
SHEB NEP ∼3.5 × 10−10 W at the band-width Δf = 1 Hz and v = 36 GHz. 相似文献
14.
Md. Salimullah R. R. Sharma V. K. Tripathi 《Applied Physics A: Materials Science & Processing》1981,25(3):361-365
Using the fluid model for the nonlinear response of ions, we have studied the nonlinear scattering of an electromagnetic ion
cyclotron wave off the ion acoustic wave in a plasma. The low frequency nonlinearity arises through the parallel ponderomotive
force on ions and the high frequency nonlinearity arises through the nonlinear current density of ions. For a typical nonisothermal
plasma (T
e/T
i∼10) the threshold for this instability in a uniform plasma is ∼1mW/cm2. At power densities ≳102 W/cm2, the growth rate for backscatter turns out to be ∼104s−1. 相似文献
15.
E. Mezzetti B. Minetti F. Abbattista M. Vallino D. Andreone V. Lacquaniti R. Cherubini 《Il Nuovo Cimento D》1990,12(7):1017-1020
Summary Pellets of sintered YBa2Cu3O7−δ with three different oxygen contents have been irradiated with fast neutron beams of energies 6.5, 3.3 and 4.4 MeV at fluences
of 7.7·104, 1.3·105 and 1.4·109 n/cm2, respectively. The radiation damage has been investigated by comparing the critical temperature (T
c
mid
), the zero resistivity and the onset temperature before and after neutron irradiation. The critical current has been measured
for a few samples in the same experimental conditions. In all transport measurements two different responses to the neutron
radiation are observed and discussed. 相似文献
16.
Yu. S. Lutostansky V. I. Lyashuk I. V. Panov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(4):533-537
A model for the production of transuranium isotopes under the conditions of pulse nucleosynthesis in a powerful neutron flux
(∼1024−1025 neutron cm−2) is considered. The explosive nature of the process allows us to separate it into two parts: the process of multiple neutron
captures (t < 10−6 s) and the process of the subsequent β-decays for neutron-rich nuclei. The model of multiple captures neutron includes a
variation of the cross section of the (n, γ) reaction as a result of the adiabatic expansion of the explosive nucleosynthesis
area. A binary mixture of 238U and 239Pu is used as the initial isotope composition. 相似文献
17.
Fast particles from laser-induced processes in ultra-dense deuterium D(−1) are studied. The time of flight shows very fast
particles, with energy above MeV. Such particles can be delayed or prevented from reaching the detector by inserting thin
or thick metal foils in the beam to the detector. This distinguishes them from energetic photons which pass through the foils
without delays. Due to the ultra-high density in D(−1) of 1029cm−3, the range for 3 MeV protons in this material is only 700 pm. The fast particles ejected and detected are thus mainly deuterons
and protons from the surface of the material. MeV particles are expected to signify fusion processes D+D in the material.
The number of fast particles released is determined using the known gain of the photomultiplier. The total number of fast
particles formed, assuming isotropic emission, is less than 109 per laser pulse at < 200 mJ pulse energy and intensity 1012W cm−2. A fast shockwave with 30keV u−1 kinetic energy is observed. 相似文献
18.
ESR investigations on exchange coupled pairs of Cu ions in single crystals of Cu(dtc)2, isomorphously diluted with the corresponding diamagnetic zinc salt, are reported. The spin Hamiltonian parameters for the
coupled species (S=1) are:g
‖=2.1025,g
+=2.031,A=75.1×10−4 cm−1,B=14.8×10−4,D=276.0×10−4 cm−1 andE=46.7×10−4 cm−1. While theg andA tensors show tetragonal symmetry, the zeor-field splitting tensor is rhombic and has principal axes different from those
of theg andA tensors. Intensity measurements made down to 4.2 K indicate that the exchange is ferromagnetic with |FFF| ∼ 10 cm−1. Direct dipole-dipole interaction appears to be the major contribution to the zero-field splitting. A calculation on the
distributed point dipole model shows that dipolar interaction is considerably modified by the high covalency of the Cu-S bond
and accounts for the rhombic nature of the tensor. The possible exchange mechanisms in Cu(dtc)2—direct exchange and superexchange through the bridging sulphurs—are discussed. 相似文献
19.
I. G. Gogidze P. B. Kuminov A. V. Sergeev A. I. Elant’ev E. M. Men’shchikov E. M. Gershenzon 《Technical Physics》1998,43(10):1193-1198
A new type of fast detector is proposed. The operation of the detector is based on the change induced in the kinetic inductance
of NbN and YBa2Cu3O7−δ
superconducting films by nonequilibrium quasiparticles produced by electromagnetic radiation. The speed of a NbN detector
is essentially temperature-independent and is less than 1 ps. A model based on the Omen-Scalapino scheme describes well the
experimental dependence of the voltage-power sensitivity of a NbN detector on the modulation frequency of the radiation. A
low equilibrium quasiparticle density and a high quantum yield give detecting power D*=1012W−1 · cm · Hz1/2 at temperature T=4.2 K and D*=1016 W−1 · cm · Hz1/2 at temperature T=1.6 K. The time constant of the low-temperature YBaCuO induction detector is determined only by the electron-phonon interaction
time τ
e-ph
d
in the nodal regions.
Zh. Tekh. Fiz. 68, 63–69 (October 1998) 相似文献
20.
R. Yu. Abdulsabirov I. I. Antonova S. L. Korableva N. M. Nizamutdinov V. G. Stepanov N. M. Khasanova 《Physics of the Solid State》1997,39(3):423-425
The orientational dependences of the EPR spectra of Fe3+-doped LiCaAlF6 single crystals (space group P31c, Z=2), grown at the Laboratory of Magnetic Radio Spectroscopy at Kazan’ State University, have been investigated in detail.
The spectrum is described by a trigonal spin Hamiltonian with the following parameters: B
20=40.072×10−4 cm−1, B
40=−5.799×10−4 cm−1, B
43=−4.281×10−4 cm−1, A
s=24.33±1, A
p=6.13±1, g
∥=g
⊥=2.00217±0.0003. A theoretical calculation of the hyperfine structure parameters shows that they are described quite well
when allowance is made for the overlapping of the wave functions of the paramagnetic center and the ligands (F−).
Fiz. Tverd. Tela (St. Petersburg) 39, 488–490 (March 1997) 相似文献