Zoltan Seres

Neutron-induced production of protons, deuterons and tritons on copper and bismuth

Abstract Inclusive cross sections for production of protons, deuterons and tritons by neutrons in the energy range of 300–580 MeV on copper and bismuth have been measured at five angles between 54° and 164°. The systematic dependence of the invariant cross sections on incident energy and emission angle are evaluated. For the study of the mass-number dependence earlier data on carbon are included. The results are discussed on the basis of different models, like quasi-two-body sealing or moving-source model.

Decay time measurements on "pure" CsI scintillators prepared by different methods

Abstract The discovery of the fast decay time of pure CsI and the various results of the measured samples led us to investigate the decay time of CsI crystals prepared by different methods. Carefully grown or prepared pure CsI behaves as fast (ns range) scintillators with a strongly or totally suppressed slow (μs range) decay component. The presence or the absence of the slow component is related to the preparation method, and to the remaining built-in contamination of the samples. Pure CsI crystals prepared by the zone melting technique show a fast luminescence at 310 nm with an intensity of 5% relative to NaI(Tl) for electrons. The slow luminescence is strongy suppressed, practically absent. This fast luminescence consists f two components: an ultrafast component and a fast one with decay times of 1.8 ns and 12.9 ns respectively; the intensity of of the two components is 0.32 for gamma radiation. It means that the relative intensity of the ultrafast component is 1.2%, that of the fast one is 3.8% relative to NaI(Tl) for electrons. Pure CsI prepared by the cold press technique has an ultrafast component of 1.0 ns and a fast one of 9.6 ns with an intensity ratio of 0.65 for electrons; the slow component is totally absent. The relative light output of this luminescence is 4%; i.e., the relative intensity of the ultrafast component is 1.6%, that of the fast one is 2.4% relative to NaI(Tl) for electrons. The relative intensity of the ultrafast component of BaF 2 (220 nm) is 4%, that of the slow (310 nm) one is 16% relative to NaI(Tl) for electrons. Pure CsI crystals prepared by the conventional growing method have a slow luminescence (decay time: 3 μs) with a relative intensity of 26% to NaI(tl) for electrons. They have a fast luminescence of 8% relative to CsI(Tl) for alphas if the surface was polished by ethanol, but a strong slow luminescence of 58% relative to the CsI(Tl) if it was polished by water or ethylene glycol.

Neutron yields from 155 MeV/nucleon carbon and helium stopping in aluminum

Neutron fluences have been measured from 155 MeV/nucleon 4He and 12C ions stopping in an Al target at laboratory angles between 10 and 160 deg. The resultant spectra were integrated over angle and energy above 10 MeV to produce total neutron yields. Comparison of the two systems shows that approximately two times as many neutrons are produced from 155 MeV/nucleon 4He stopping in Al and 155 MeV/nucleon 12C stopping in Al. Using an energy-dependent geometric cross-section formula to calculate the expected number of primary nuclear interactions shows that the 12C + Al system has, within uncertainties, the same number of neutrons per interaction (0.99 +/- 0.03) as does the 4He + Al system (1.02 +/- 0.04), despite the fact that 12C has three times as many neutrons as does 4He. Energy and angular distributions for both systems are also reported. No major differences can be seen between the two systems in those distributions, except for the overall magnitude. Where possible, the 4He + Al spectra are compared with previously measured spectra from 160 and 177.5 MeV/nucleon 4He interactions in a variety of stopping targets. The reported spectra are consistent with previously measured spectra. The data were acquired to provide data applicable to problems dealing with the determination of the radiation risk to humans engaged in long-term missions in space; however, the data are also of interest for issues related to the determination of the radiation environment in high-altitude flight, with shielding at high-energy heavy-ion accelerators and with doses delivered outside tumor sites treated with high-energy hadronic beams.

Production of protons, deuterons and tritons on carbon by intermediate energy neutrons

Abstract Inclusive cross sections for production of protons, deuterons and tritons on carbon by neutrons in the energy range of 300–580 MeV were determined at nine angles between 51° and 165°. The invariant cross sections are well represented by an exponential fit, E d σ d 3 p ∝ exp (−Bp 2 ) . The slope parameters exhibit a systematic dependence on incident energy and emission angle. The results are discussed on the basis of the model of quasi-two-body scaling.

Neutron emission from 14N + 165Ho collisions at 35 MeV/u

Abstract Neutron emission from 14 N + 165 Ho collisions has been studied at 25 MeV/u incident energy. Energy and angular distributions of the neutrons were measured in coincidence with projectile-like fragments (Li, Be, B, and C) emitted at angles of 10° and 30°. The spectra of neutrons at angles far from the angle of a coincident fragment have been satisfactorily parameterized in terms of a slowly moving, target-like source of temperature 2–3 MeV and a half-beam-velocity source of temperature about 7 MeV. The latter source accounts for about 20% of the detected neutrons for in-plane measurements. The out-of-plane cross sections are smaller. The relevant parameters of the moving-sources parametrization suggest a simple model which qualitatively explains the data in terms of the development of a hot participant zone and its subsequent mass exchange interactions with spectators in the projectile and target nuclei.

Neutron/γ-ray pulse-shape discriminator

We present a neutron/γ-ray pulse-shape discriminator that is inexpensive and highly stable. Both of these favorable attributes come from the fact that the basic element of the device is a length of co-axial cable. The quality of discrimination is similar to that obtained with other modern devices.

Neutron-induced pion production on carbon, copper and bismuth at intermediate energies

Abstract Inclusive production cross sections of charged pions on carbon, copper and bismuth by neutrons in the energy range of 300–580 MeV have been measured from 54° to 164°. The invariant cross sections can be expressed by E d σ d 3 p =A exp (−Bp 2 ) for the high-energy part of the pion spectra. The slope parameter exhibits a systematic variation with neutron energy and emission angle for the three targets. The dependence of the pion production on the target mass number varies strongly with pion energy and emission angle. The production cross sections are compared with the model of quasi-two-body scaling, the moving-source model and with intranuclear cascade calculations.

Charged particle production on 12C by intermediate energy neutrons

Abstract Energy spectra of protons, deuterons and tritons produced on 12 C by 545 MeV neutrons have been measured at 7 angles between 73° and 165°. The slopes of the invariant cross sections and absolute yields are compared to corresponding proton induced reactions at similar energies and angles.

Optical transmission of Mylar and Teflon films

In an application involving light transmission via total internal reflection, the light is attenuated at each reflection by passage through a thin film. To choose a film that would minimize the attenuation we had to measure the optical properties of Mylar and Teflon. Our results showed that type-D Mylar was preferable.

Study of the proton-deuteron break-up reaction in complete kinematics at 1 GeV

Abstract The coincidence cross section and polarization have been measured for the proton-deuteron break-up reaction pD→ppn at 1 GeV in a kinematically complete experiment. Two final protons from the reaction were detected in coincidence by means of a two-arm spectrometer at non-symmetric scattering angles θ 1 =19°–27°, θ 2 =61° in the momentum range of the neutron-spectator up to 0.3 GeV/ c . At kinematic conditions of the experiment the coincidence cross section is well described in the framework of the single scattering impulse approximation with the Paris wave function of the deuteron. The polarization is also in good agreement with IA predictions.