共查询到20条相似文献,搜索用时 15 毫秒
1.
H. M. Hoang U. Garuska D. Kielan A. Marcinkowski B. Zwieglinski 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(3):283-290
Cross sections for70,72,73,74Ge(n, p)70,72,73,74Ga,70Ge(n, 2n)69Ge,72Ge (n,)69Zn
m
and74Ge(n, )71Zn
m
reactions are measured in the energy range from 13.0 to 16.6 MeV by the activation method using Ge(Li) detector-ray spectroscopy and compared with predictions of the reaction model incorporating preequilibrium and equilibrium emission mechanisms to interpret the energy dependence of the isotopic effect occuring in the (n, p) reaction. The fitted single-particle state-density parametersg, determined here for the germaniums are discussed together with theg-values found previously for the Se, Zr and Pd isotopic chains. A validity of the consistency condition between the precompound and compound models, which relatesg to the experimental level-density parametera viaa=
2
g/6 is demonstrated. 相似文献
2.
D. Lambrecht T. Blaich T. W. Elze H. Emling H. Freiesleben K. Grimm W. Henning R. Holzmann J. G. Keller H. Klingler J. V. Kratz R. Kulessa S. Lange Y. Leifels E. Lubkiewicz E. F. Moore W. Prokopowicz R. Schmidt C. Schütter H. Spies K. Stelzer J. Stroth E. Wajda W. Waluś M. Zinser E. Zude 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(2):115-120
We investigate the beam energy dependence of neutron and proton squeeze-out in collisions of197Au+197Au atE/A=400—800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve — independent of beam energy — if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile.
The members of the FOPI-collaboration: J.P. Alard, Z. Basrak, N. Bastid, I.M. Belayev, M. Bini, R. Bock, A. Buta, R. aplar, C. Cerruti, N. Cindro, J.P. Coffin, M. Crouau, P. Dupieux, J. Erö, Z.G. Fan, P. Fintz, Z. Fodor, R. Freifelder, L. Fraysse, S. Frolov, A. Gobbi, Y. Grigorian, G. Guillaume, N. Herrmann, K.D. Hildenbrand, S. Hölbling, O. Houari, S.C. Jeong, M. Jorio, F. Jundt, J. Kecskemeti, P. Koncz, Y. Korchagin, R. Kotte, M. Krämer, C. Kuhn, I. Legrand, A. Lebedev, C. Maguire, V. Manko, T. Matulewicz, G. Mgebrishvili, J. Mösner, D. Moisa, G. Montarou, P. Morel, W. Neubert, A. Olmi, G. Pasquali, D. Pelte, M. Petrovici, G. Poggi, F. Rami, W. Reisdorf, A. Sadchikov, D. Schüll, Z. Seres, B. Sikora, V. Simion, S. Smolyankin, U. Sodan, N. Taccetti, K. Teh, R. Tezkratt, M. Trzaska, M.A. Vasiliev, P. Wagner, J.P. Wessels, T. Wienold, Z. Wilhelmi, D. Wohlfarth, A.V. Zhilin. 相似文献
3.
G. A. Lalazissis S. E. Massen C. P. Panos 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):257-261
The inlfuence of state dependent short range correlations on the occupation numbers of the single particle shell model orbits of the doubly closed shell nuclei16O and40Ca is examined. The study shows that the effect of the state dependence of the short range correlations is rather small. The total depletion of the nuclear Fermi sea changes slightly compared with the one calculated by considering state independent short range correlations. 相似文献
4.
A. B. Quint W. Reisdorf K. -H. Schmidt P. Armbruster F. P. Heßberger S. Hofmann J. Keller G. Münzenberg H. Stelzer H. -G. Clerc W. Morawek C. -C. Sahm 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(2):119-131
Excitation functions in the vicinity of the Coulomb barrier have been measured for the formation of evaporation residues in100Mo-induced fusion reactions with90, 92, 96Zr,92, 96, 98, 100Mo,104Ru and110Pd as well as for the system96Zr+96Zr. From these data the fusion probability in central collisions was extracted covering a range of 4 orders of magnitude. At the fusion barriers expected from systematics we find that the fusion probability is suppressed by one to three orders of magnitude. It is rising very gradually at higher energies and reaches for the heaviest systems saturation only at energies as high as 30 MeV above the barrier. The observed hindrance of the fusion process increases roughly with the growing Coulomb repulsion between the collision partners, but there is also a distinct influence of their individual nuclear structure. The data are compared to the extra-push model, the surface-friction model and the diabatic fusion model. A parameterisation of the extra-push energy and its fluctuation in terms of a macroscopic quantity like the Coulomb repulsion combined with a microscopic quantity characterizing the nuclear structure is proposed. As a byproduct of this work a new alpha emitter,191Po, could be identified. Its half-life is (15.5
–2.5
+6
) ms, the alpha energy is (7314±20) keV. 相似文献
5.
We demonstrate that for a given pump source, there is an optimum pump threshold to achieve the maximum single-frequency output
power in singly resonant optical parametric oscillators. Therefore, cavity losses and parametric amplification have to be
adjusted. In particular, continuous-wave output powers of 1.5 W were achieved with a 2.5 cm lithium niobate crystal in comparison
with 0.5 W by a 5 cm long crystal within the same cavity design. This counter-intuitive result of weaker amplification leading
to larger powers can be explained using a model from L.B. Kreuzer (Proc. Joint Conf. Lasers and Opt.-Elect., p. 52, 1969). Kreuzer also states that single-mode operation is possible only up to pump powers which are 4.6 times the threshold value.
Additionally, implementing an outcoupling mirror to increase losses, single-frequency waves with powers of 3 W at 3.2 μm and 7 W at 1.5 μm could be generated simultaneously. 相似文献
6.
A refined interpretation of Christiansen filter experiments is described, which allows for the effects of inhomogeneities in the powder column of the filter. Using this procedure the evaluation of experiments on enriched samples of lead isotopes provided the neutron coherent scattering lengths (in fm) for the separated isotopes:b (204) =10.6 ± 2.0;b (206)=9.23 ± 0.05;b (207)=9.28 ± 0.04 andb (208)=9.50 ± 0.06. The corresponding potential scattering radius R was obtained by taking account of resonance contributions as earlier used in the determination of the neutron's electric polarizability. The found R=9.74 ± 0.07 fm is in good argreement with the literature. This confirms the correctness of the used resonance contributions.Work partially supported by the Bundesministerium für Forschung und Technologie 相似文献
7.
W. Schott H. Daniel F. J. Hartmann W. Neumann 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(1):81-84
The spectral flux densityn(T) of – emerging from a Au or MgF2 moderator has been measured at low energiesT using time-of-flight. Fromn(T) the stopping powerS(T) of Au was determined for 2 keVT22 keV, and of MgF2 for 2 keVT12 keV. For Au,S(T) is smaller than calculated values obtained from proton atomic data practically in the wholeT range (Barkas effect); at lowT
S(T) approaches the calculated values. For MgF2,S(T) agrees fairly with the calculated values above 5 keV and then drops below these values. We ascribe this dropping to the large energy gap of the MgF2 insulator.We wish to thank H. Angerer, H. Plendl, G. Schmidt, and C.A. Schug for help with the data taking, J. Homolka for computational help, H. Hagn, and H. Weiss for technical assistance and P. Maier-Komor and R. Scherrer for manufacturing the windows and targets. The hospitality of PSI and financial support by the German Bundesministerium für Forschung und Technologie are acknowledged. 相似文献
8.
V. de la Mota F. Sébille B. Rémaud P. Schuck 《Zeitschrift für Physik A Hadrons and Nuclei》1992,343(4):417-427
Theoretical analyses of heavy-ion reactions are performed in the framework of the semi-classical Landau-Vlasov approach. The incident energies are investigated in the range from intermediate to low energy regimes, where transverse collective motion has been experimentally evidenced. The influence of the equation of state (E.O.S.) parameters on various collective observables is studied in relation with the action of the residual interactions. From the sensitivity to both aspects, and taking into account the experimental biases limitations, our investigation indicates that E.O.S. signatures should be more expected at energies below 100 MeV per nucleon. 相似文献
9.
P. Cluzeau F. Bougrioua G. Joly L. Lejček H. T. Nguyen 《Czechoslovak Journal of Physics》2004,54(3):365-376
A simplified model of an inclusion represented by (+1)-wedge disclination and an accompanying hyperbolic defect ((−1)-wedge
disclination) in smectic C* free standing films is used to describe the early stage of the ordering process of inclusions
into chains. The elastic interaction between inclusions and their associated hyperbolic defects is used to discuss the dynamics
observed experimentally during the inclusion chaining when inclusions are at distances much larger than their radii.
This work was also supported by Grant No. 202/02/0840 of the Grant Agency of the Czech Republic and by the research project
AV0Z1-010-914. 相似文献
10.
C. Hecht H. Kronemayer T. Dreier H. Wiggers C. Schulz 《Applied physics. B, Lasers and optics》2009,96(1):119-125
The iron-atom concentration distribution as well as the gas-phase temperature was measured via laser-induced fluorescence
(LIF) during iron-oxide nanoparticle synthesis in a low-pressure hydrogen/oxygen/argon flame reactor using ironpentacarbonyl
(Fe(CO)5) as precursor. Temperature measurements based on multi-line NO-LIF imaging are used to correct for temperature-dependent
ground-state populations. The concentration measurement is calibrated based on line-of-sight absorption measurements. The
influence of the precursor on the flame is observed at precursor concentrations larger than 70 ppm as the flame front moves
closer to the burner surface with increasing Fe(CO)5 concentration. 相似文献
11.
E. Hanelt A. Grewe K. -H. Schmidt T. Brohm H. -G. Clerc M. Dornik M. Fauerbach H. Geissel A. Magel G. Münzenberg F. Nickel M. Pfützner C. Scheidenberger M. Steiner K. Sümmerer B. Voss M. Weber J. Weckenmann C. Ziegler 《Zeitschrift für Physik A Hadrons and Nuclei》1993,346(1):43-46
The longitudinal-momentum distributions of projectile fragments from 0.8 A GeV136Xe and 1 A GeV197Au projectiles impinging on targets of beryllium and aluminium, respectively, have been measured using the projectile-fragment separator FRS at GSI. Different momentum distributions have been found for two different classes of fragmentation processes: the abundant hot fragmentation with several nucleons evaporated from the prefragments, and the rare cold fragmentation with only protons removed from the projectile, but no nucleons evaporated. The data are compared to model calculations.This article comprises part of the Ph.D. thesis of B. Voss 相似文献
12.
N. Koyumdjieva A. A. Lukyanov N. Janeva 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(1):31-34
The characteristic functions of the statistical Wigner'sR-matrix for the case of one-channel scattering in competition with multichannel radiative capture have been drown. Different approximations and their relevance in neutron physics applications are discussed.Communicated by: X. Campi 相似文献
13.
14.
B. V. Krippa 《Zeitschrift für Physik A Hadrons and Nuclei》1995,351(4):411-415
We investigate the possibility of producing hypernuclei with proton beams via (p, K
+) reaction. We present differential cross sections calculations utilizing the distorted wave impulse approximation in momentum space. We consider the reactions12C(p,K
+)
13
and16O(p,K
+)
17
within the energy region 0.8 GeV1.2 GeV. We study both the case of formation of in S-state (12C) and P-state (16O). We take into account the contribution of both one-step and two-step processes when K pair is produced directly by incoming proton and intermediate pion, respectively. It is found that practically in all cases the two-step processes give significant contribution.Work supported by KFA Julich 相似文献
15.
16.
A 500 GeV center-of-mass International Linear Collider (ILC), currently under R&D development, is foreseen as the next-generation
high-energy physics (HEP) instrument [1]. The achievement of a 31.5 MV/m average operational accelerating gradient in a single
cryomodule is a proof of principle for the ILC project. However, individual cavity performance may have a large spread in
operating gradients, up to 20% of the nominal value [2, 3]. In case of cavities performing below the average, the design parameters
could be achieved by tweaking the RF distribution accordingly. We present a simple theoretical analysis of the ILC cryomodule
operation with a gradient spread. The difference in the gradients breaks the synchronism of a transient processes in each
cavity and causes nonuniform acceleration along the bunch train. A proper solution was found to maintain flattop operation
of the accelerating module. Finally, we perform numerical efficiency estimations for the proposed RF distribution scheme based
on real data of the gradient spread of actual cavities.
The text was submitted by the authors in English. 相似文献
17.
N. T. Khai T. D. Thiep T. T. An P. V. Cuong N. T. Vinh A. G. Belov O. D. Maslov 《Physics of Particles and Nuclei Letters》2008,5(5):437-440
Bremsstrahlung emission, or radiation loss, is the dominant mechanism of energy dissipation of electrons at relativistic energies
greater than a few MeV when it is subjected to acceleration in the field of the nucleus or of the electrons. In this study,
the Monte Carlo calculations for bremsstrahlung spectra have been described for the case of a thick tungsten target with incident
electron beams from 10 to 50 MeV, where secondary interactions induced by the electrons and photons in the target, such as
energy loss, absorption, scattering, and (e
+, e
−)-pair production effects, were taken into account.
The text was submitted by the authors in English. 相似文献
18.
19.
O. I. Meshkov S. A. Glukhov V. F. Gurko A. D. Khilchenko V. A. Kiselev E. B. Levichev N. Yu. Muchnoi P. A. Piminov V. V. Smaluk A. N. Zhuravlev 《Physics of Particles and Nuclei Letters》2008,5(7):601-604
The experiments in measuring the dynamic aperture and beam energy spread of the VEPP-4M collider [1] are described. The optical
diagnostics of the accelerator were applied for these purposes.
The text was submitted by the authors in English. 相似文献
20.
We discuss a restriction of the induced radiation concept in classical beam systems due to accompanying spontaneous radiation
(radiation friction). For short wave FELs, spontaneous radiation renders a noticeable influence on the phasing of particles,
which is the base mechanism of induced radiation in classical systems. It leads to an essential restriction on the radiating
system length and gain which cannot be compensated by an increase in the beam current.
The text was submitted by the authors in English. 相似文献