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1.
Gamma-ray pulses are calculated from 2D numerical simulations of upward atmospheric discharge in a self-consistent electric
field using the multigroup approach to the kinetics of relativistic runaway electrons. Thecalculated numbers and spectra of
γ-rays are consistent with the data on terrestrial γ-ray flashes observed aboard spacecraft. The calculated runaway electron
flux is concentrated mainly within the domain of the blue jet fluorescence. This proves that exactly this domain is a source
of the γ-ray flashes. One γ-ray flash generates ∼1014-1015 photonuclear neutrons.
The text was submitted by the authors in English 相似文献
2.
G. V. Valsky A. M. Gagarski I. S. Guseva D. O. Krinitsin G. A. Petrov Yu. S. Pleva V. E. Sokolov V. I. Petrova T. A. Zavarukhina T. E. Kuzmina 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):767-771
The angular dependence of the γ-ray asymmetry relative to the plane formed by the directions of fission-fragment separation
and longitudinal polarization of the thermal neutrons inducing 235U(n, f) fission was investigated. The results obtained confirm the existence of γ-ray emission asymmetry and the dependence of its
coefficient on the angle between the axes of the fission-fragment and γ-ray detectors, revealed for the first time by the
ITEP group at the FRM-II reactor in Munich. The observed T-odd effect of around ∼2 × 10−4 can be explained by the angular anisotropy of the γ-ray emission from fission fragments with large angular momenta oriented
relative to the fission axis. 相似文献
3.
D.C. Biswas B.K. Nayak M. Cinausero B. Fornal G. Viesti D. Bazzacco M. DePoli D. Fabris E. Fioretto M. Lunardon D.R. Napoli G. Nebbia G. Prete C.A. Ur G. Vedovato 《The European Physical Journal A - Hadrons and Nuclei》1999,4(4):343-348
The high energy γ-ray emission accompanying the spontaneous fission of 252Cf has been measured in coincidence with individual fission fragments selected by discrete γ-ray transitions. The enhancement
of the γ-ray emission probability in the energy range Eγ= 3–8 MeV has been observed for the fission fragments in the region of nearly symmetric mass splitting, confirming results
reported in previous investigations. The γ-γ coincidence technique employed in the present work clearly demonstrate that the
major contribution to this enhancement is caused by the fission channels where one fragment is near to the N= 82 or Z= 50 shell closures. The high energy γ-ray emission probability does not show any significant dependence on the number of
neutrons emitted in the fission process, supporting the hypothesis that high energy γ-rays are mainly emitted from the fragments
after the neutron evaporation.
Received: 22 December 1998 相似文献
4.
D.C. Biswas R.K. Choudhury M. Cinausero B. Fornal D.V. Shetty G. Viesti D. Fabris E. Fioretto M. Lunardon G. Nebbia G. Prete D. Bazzacco M. DePoli D.R. Napoli C.A. Ur G. Vedovato 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):189-195
Measurements of fission fragment yields and neutron multiplicities have been carried out for the Mo-Ba fragment pairs in
the spontaneous fission of 252Cf, using the γ-ray spectroscopy technique to analyze γ-γ-γ coincidence data. Prompt γ -ray multiplicities were also measured
as a function of the number of neutrons emitted in the fission process leading to the Mo-Ba partition. We do not observe the
enhancement in the yields of events with high neutron emission multiplicity (νn > 7) that has been associated to a second fission mode leading to the production of hyperdeformed Ba fragments, as reported
in some earlier studies. The average γ-ray multiplicity is found to be rather weakly dependent on the number of neutrons emitted
in the fission process.
Received: 21 July 1999 / Revised version: 19 November 1999 相似文献
5.
Y K Agarwal C V K Baba D R Chakrabarty V M Datar D A Gothe H C Jain A Roy M K Sharan 《Pramana》1990,35(1):49-65
An array of seven hexagonal NaI(Tl) detectors has been set up for measuringγ-ray spectra in the energy region 5 MeV ≤E
γ ≤ 40 MeV with good accuracy. This is in contrast to earlier set ups which mostly used one large sized (about 10 inchesφ × 15 inches long)NaI(Tl) detector. This set up has been made for the study ofγ decay of GDR based on high spin states and ultra-dipole radiations.
The array has been provided with the following features: a) TOF discrimination against neutrons, b) pile up detection and
elimination, c) active and passive shielding to cut down background and d) an array of trigger counters for multiplicity dependence
measurements. The well known program EGS4 has been used to determine the response of the array forγ-rays in the energy region 5–40 MeV and several test measurements have been carried out to confirm the validity of the calculated
response functions. Some typicalγ-ray spectra fromα and16O induced reactions measured at VECC, Calcutta and Pelletron accelerator at TIFR are also shown. 相似文献
6.
E. I. Bochkov L. P. Babich I. M. Kutsyk 《Journal of Experimental and Theoretical Physics》2013,117(1):177-184
Using the concept of avalanche relativistic runaway electrons (REs), we perform numerical simulations of compact intracloud discharge (CID) as a generator of powerful natural electromagnetic pulses (EMPs) in the HF-VHF range, called narrow bipolar pulses (NBPs). For several values of the field overvoltage and altitude at which the discharge develops, the numbers of seed electrons initiating the avalanche are evaluated, with which the calculated EMP characteristics are consistent with the measured NBP parameters. We note shortcomings in the hypothesis assuming participation of cosmic ray air showers in avalanche initiation. The discharge capable of generating NBPs produces REs in numbers close to those in the source of terrestrial γ-ray flashes (TGFs), which can be an argument in favor of a unified NBP and TGF source. 相似文献
7.
Shen Shuifa Fang Keming Gu Jiahui Liu Qingcheng Xu Furong 《The European Physical Journal A - Hadrons and Nuclei》2007,32(2):149-158
The decay of 95Ru has been investigated by means of γ-ray spectroscopy. The 95Ru nuclei were produced by the reaction 92Mo( α, n) 95Ru at a beam energy of 17MeV. High-purity Ge detectors have been used singly and in coincidence to study γ-rays in the decay of 95Ru to 95Tc. 132 γ-rays are reported, among them, energies and intensities for 127 transitions have been determined. A decay scheme of 95Ru with 31 levels is proposed which accommodates 127 of these transitions. Spins and parities for three new levels are proposed
from calculated log ft values, measured γ-ray branching ratios, and in-beam experiment results of the daughter nucleus 95Tc. Combining with the high-spin states observed by in-beam γ-ray spectroscopy of previous decay works, the structure of the excited states of 95Tc is discussed in the framework of the projected shell model. 相似文献
8.
X.H. Zhou Y. Zheng Y.H. Zhang Z. Liu Q.Y. Pan Z.G. Gan T. Hayakawa M. Oshima T. Toh T. Shizuma J. Katakura Y. Hatsukawa M. Matsuda H. Kusakari M. Sugawara K. Furuno T. Komatsubara 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):253-255
The high-spin states of 145Tb have been studied in the 118Sn(32S, 1p4n) reaction at 32S energies from 161 to 175 MeV using techniques of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation functions
and γ-γ-t coincidences were performed with 12 BGO(AC)HPGe detectors. Based on the measured results of γ-γ coincidences, γ-ray anisotropies
and DCO ratios, a level scheme for 145Tb was established for the first time. The observed excited states show typical irregular pattern in a spherical nucleus,
and the low-lying levels have been interpreted qualitatively with a particle-core coupling.
Received: 21 September 2001 / Accepted: 9 November 2001 相似文献
9.
The reliability of communications reporting observations of neutron flux enhancements in thunderstorm atmosphere is analyzed. The analysis is motivated by the fact that the employed gas-discharge counters on the basis of reactions 3He(n, p)3H and 10B(n; 4He, γ)7Li detect not only neutrons but any penetrating radiations. Photonuclear reactions are capable of accounting for the possible amplifications of neutron flux in thunder-storm atmosphere since in correlation with thunderstorms γ-ray flashes were repeatedly observed with spectra extending high above the threshold of photonuclear reactions in air. By numerical simulations, it was demonstrated that γ-ray pulses detected in thunderstorm atmosphere are capable of generating photonuclear neutrons in numbers sufficient to be detected even at sea level. 相似文献
10.
H. Tiesler H. Klein A. Fitzler I. Wiedenhöver P. von Brentano 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):157-160
High-spin states in 143Pm have been investigated via the 128Te(19F,4nγ)143Pm reaction using techniques of in-beam γ-spectroscopy. γ-ray singles, γ-γ coincidences, γ-ray anisotropies and DCO ratios
have been measured. Based on these measurements, the level scheme of 143Pm has been extended up to an excitation energy of 10535.4 keV, including 48 new γ-rays deexciting 28 new levels. The yrast
levels in 143Pm can be understood qualitatively in the framework of a weak-coupling model.
Received: 10 July 2000 / Accepted: 12 October 2000 相似文献
11.
J. W. Cronin 《Il Nuovo Cimento C》1996,19(6):847-863
Summary The techniques for γ-ray astronomy at energies ≥10 TeV using air shower detectors are discussed. The results, based on a number
of large arrays, are negative, with no point sources being identified. While the contributions to γ-ray astronomy so far have
been only upper limits, these arrays in the future will make significant progress in the understanding of cosmic rays in the
energy range 1013 eV to 1016 eV. Also, contributions to solar physics are being made by observations of shape and time dependence of the shadow of the
Sun as observed in cosmic rays. For the advancement of γ-ray astronomy a greater sensitivity is required in the energy region
of 10 TeV. A number of promising techniques to accomplish a greater sensitivity are discussed. They include the enlargement
of the Tibet array at 4300 meters altitude, the array of open photomultipliers at La Palma (AIROBICC), which views the shower
by the Cherenkov photons produced in the atmosphere, and the instrumentation of a pond at Los Alamos with photomultipliers
(Milagro).
Invited talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995. 相似文献
12.
N. V. Eremin S. S. Markochev A. A. Paskhalov E. A. Tsvetkov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(4):544-546
The probability of high-energy γ-ray emission accompanying the spontaneous fission of 252Cf nuclei in the energy range of 5–60 MeV was measured experimentally. The γ rays were detected by a BGO detector with a size
of ∅7.6 × 7.6 cm in coincidence with neutrons detected by an organic polystyrene-based scintillator with a size of ∅6.0 ×
2.0 cm. To reject events associated with the cosmic background, we propose an original method that combines rapid digitizing
of the pulse shape and the time-of-flight method. 相似文献
13.
C. Castagnoli C. Morello G. Navarra L. Periale P. Vallania J. A. Chinellato M. De Castro Souza A. Turtelli P. Miranda A. Velarde 《Il Nuovo Cimento C》1990,13(2):345-352
Summary We present the results of a search for very high energy γ-rays (E
γ≈100 TeV) from SN 1987A between August 1987 and May 1988. No counting rate excess from the source is observed. The larger
enhancement is seen in January 1988, but is statistically not significant (1.4 s.d.). The derived upper limits to the γ-ray
and proton luminosities of the SN areL
γ≤1.9·1040 erg/s andL
p≤1.2·1042 erg/s.
To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee. 相似文献
14.
Y. Ma S. Ajimura K. Aoki M. Dairaku Y. Y. Fu H. Fujioka T. Fukuda K. Futatsukawa K. Hosomi W. Imoto M. Kawai Y. Kakiguchi S. Kinoshita T. Koike N. Maruyama M. Mimori S. Minami Y. Miura K. Miwa Y. Miyagi T. Nagae D. Nakajima H. Noumi K. Shirotori T. Suzuki T. Takahashi T. N. Takahashi H. Tamura K. Tanida N. Terada A. Toyoda K. Tsukada M. Ukai S. H. Zhou 《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):243-246
In this paper, a preliminary result from the latest hypernuclear γ -ray spectroscopy experiment (KEK-E566) is presented together
with a short discussion. The experiment was performed at the KEK-PS K6 beam line in 2005. In this experiment, the 12C(π+, K
+)12
ΛC reaction was employed to populate 12
ΛC/11
ΛB hypernuclei. A germanium detector array, Hyperball2, was constructed to detect γ -rays emitted from the hypernuclei produced.
Three hypernuclear γ -ray peaks were observed and assigned. 相似文献
15.
T. Weber J. de Boer K. Freitag J. Gröger C. Günther P. Herzog V.G. Soloviev A.V. Sushkov N.Yu. Shirikova 《The European Physical Journal A - Hadrons and Nuclei》1998,3(1):25-48
The electron-capture decay of 228Pa to levels in 228Th was studied using mass-separated sources and a γ-ray detection system consisting of five Compton-suppressed Ge detectors.
A total of 87 levels were observed up to an excitation energy of 2 MeV which are connected by approximately 500 γ-ray transitions.
The complete octupole quadruplet, three excited K
π=0+ bands and two K
π=2+ bands were identified below 1.4 MeV. The observed level structure is compared to calculations within the quasiparticle-phonon
nuclear model. The surprisingly good agreement indicates that 228Th has less transitional character than hitherto assumed.
Received: 30 March 1998 相似文献
16.
N. Gelli F. Lucarelli M. Cinausero E. Fioretto G. Prete D. Fabris M. Lunardon G. Nebbia G. Viesti D. Bazzacco C.A. Ur D.R. Napoli P. Pavan C. Rossi Alvarez P.F. Bortignon E.M. Fiore L. Fiore V. Paticchio B. Fornal 《The European Physical Journal A - Hadrons and Nuclei》2000,7(3):361-365
The high energy γ-rays from the fusion-evaporation reaction 101 MeV 19F +181Ta have been measured in coincidence with different γ-ray fold windows or discrete γ-rays in final residual nuclei. The line-shape
analysis of the high energy γ-ray spectra confirms the large deformation of the 200Pb nuclei at high angular momenta. Coincidences with discrete γ-transitions evidence a strong correlation between γ-rays in
the Giant Dipole Resonance region (Eγ≥ 8 MeV) and final evaporation residues.
Received: 14 September 1999 / Revised version: 17 December 1999 相似文献
17.
V. A. Zheltonozhskii A. N. Savrasov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):829-832
Isomeric yield ratios of 115m,g
Cd and 120m,g
Sb were measured in the (γ, n) reaction in the near-threshold region at γ-ray energies of 9.6, 9.8, 10.0, and 10.5 MeV. Experimental
values of the isomeric yield ratios were compared with theoretical values calculated using the TALYS-1.0 program package.
The (γ, n) reaction is shown to have a statistical character in the excitation region of residual nuclei 0.3–1.5 MeV. 相似文献
18.
D. Bucurescu Gh. Căta-Danil I. Căta-Danil M. Ivaşcu N. Mărginean C. Rusu L. Stroe C.A. Ur A. Gizon J. Gizon B. Nyakó J. Timár L. Zolnai A.J. Boston D.T. Joss E.S. Paul A.T. Semple C.M. Parry 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):255-258
High-spin states in the 96Tc nucleus have been studied with the reactions 82Se(19F,5nγ) at 68 MeV and Zn(36S,αpxn) at 130 MeV. Two γ-ray cascades (irregular bandlike structures) have been observed up to an excitation energy of about 10
MeV and spin 21-22?.
Received: 19 January 2001 / Accepted: 30 March 2001 相似文献
19.
V.G. Alpatov Yu.D. Bayukov A.V. Davydov Yu.N. Isaev G.R. Kartashov M.M. Korotkov V.E. Rad'ko A.A. Sadovsky V.M. Samoylov 《Hyperfine Interactions》1997,107(1-4):231-246
The temperature dependence of the 109Ag γ-ray self-absorption was investigated for the horizontal and vertical directions of emission. The source was a single-crystal
silver plate containing atoms of parent radionuclide 109Cd. Gamma-radiation of this γ-source and that of the monitoring γ-source, 57Co, were registered by a pair of Ge(Li)-detectors. As a result of cooling the source from 77 K to ~12 K a relative decrease
was observed of the intensity of the horizontally emitted γ-rays equal to 0.00064±0.00044. For the vertical direction the
corresponding intensity change turned out to be -0.00047±0.00051. Although these data, as one would see, give some evidence
for the possible effect of the gravitation on the resonant γ-ray absorption, future measurements must show if these results
aren’t a consequence of any apparatus effect. The ways for developments in this study are discussed and some hindrances are
considered.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
G. Meierhofer P. Grabmayr L. Canella P. Kudejova J. Jolie N. Warr 《The European Physical Journal A - Hadrons and Nuclei》2012,48(2):20
The reactions 74Ge(n, γ) and 76Ge(n, γ) have been measured with cold neutrons generated by the research reactor FRM II near Munich, Germany. The γ rays have been detected by two Compton-suppressed HPGe systems in single and coincidence mode. The number of identified prompt
transitions and levels in 77Ge was increased significantly and the decay scheme could be reconstructed for the first time. The decay scheme was also reconstructed
for 68 prompt transitions in 75Ge. Previously reported inconsistencies of the γ-ray intensities in the 77Ge β decay could be resolved. In particular, the region around 2039 keV was investigated carefully, since the background to the
neutrinoless double-beta decay of 76Ge must be understood well for the upcoming Gerda and Majorana experiments. 相似文献