N. Koori

MEASUREMENTS OF THE CROSS SECTIONS FOR n--d ELASTIC AND INELASTIC SCATTERING AT 14.1 MeV.

Abstract The differential cross sections for the elastic and inelastic scattering of 14.1 MeV neutrons by deuterons have been measured over the angular range 0°–50° in the lab system by detecting recoiling deuterons and break-up protons. The results for the elastic scattering are in good agreement with those of Seagrave, while the results for the inelastic scattering disagree with his work at forward angles. The integrated cross section for inelastic scattering agrees with the result of Catron et al. and the total cross section with the result of Poss et al . The agreement with the theoretical results of Aaron, Amado and Yam is fair. Except for a small discrepancy between the theoretical and experimental values of the cross sections, the energy spectrum of break-up protons observed at the mean angle of 3.9° satisfactorily fits the result of Aaron and Amado for the singlet n-n scattering length a nn = −23.78 fm.

Observation of Self-Quenching Streamers in Quenching Gases of Hydrocarbons and Carbon Dioxide

Basic properties of the self-quenching streamer transition have been studied for quenching gases of CH/sub 4/, C/sub 2/H/sub 6/, C/sub 3/H/sub 8/, isoC/sub 4/H/sub 10/ and CO/sub 2/ without argon. It is found that X-rays do not induce clearly the transition, but ..cap alpha..-rays, which are incident in normal to the counter anode, induce it evidently in all the quenching gases. This suggests that argon is important but is not essential to obtain the transition. Instead of energetic photons from excited argon molecular states for the transition, possible origins of energetic photons in the quenching gases are discussed.

Line broadening and Coulomb displacement energies of the hole-state analogs in the A = 111−123 odd-mass Sn isotopes

Abstract Line broadening and orbit dependence of the Coulomb displacement energy have been observed for the 1g 9/2 , 2p 1/2 and 2p 3/2 hole-state analogs in a series of odd- A Sn isotopes. The observed widths are discussed in terms of spreading width with main contributions from mixing with the isovector monopole state as well as the escape width.

Alpha spectroscopic factors for 6Li, 7Li, 9Be and 12C from the (p, pα) reaction at 296 MeV

Abstract Three-body breakup cross sections and analyzing powers for the 6Li, 7Li, 9Be and 12 C ( p ,pα) reactions were measured at an incident energy of 296 MeV. Data were analyzed using the plane wave impulse approximation (PWIA) and the distorted wave impulse approximation (DWIA) and compared with previous studies. DWIA calculations reproduce shapes of projected spectra and analyzing power distributions fairly well with the exception of the 12 C ( p ,pα) 8 Be reactions. Extracted spectroscopic factors for 6Li, 9Be and 12C are larger than those found in the previous studies. In contrast, extracted spectroscopic factors for 7Li agree with the previous work. This work suggests that the spectroscopic factor for 6Li is ∼ 0.8, independent of incident energies and reaction types.

Charge-division type position sensing with a single-wire position sensitive counter in the self-quenching streamer mode☆

Abstract Using single-wire position sensitive counters with a stainless-steel anode wire of 25 μm diameter, position sensing has been performed in the self-quenching streamer (SQS) mode. Overall position resolutions of 0.26 mm and 0.69 mm fwhm for 4.5 keV X-rays were obtained for 100 mm long and 1.82 m long counters, respectively, by means of standard NIM electronic circuits and a new ratio-to-digital converter (RDC). Problems in the application of SQS mode to position sensing are discussed.

The (3He, 3He), (3He, 3He') and (3He, α) Reactions on 12C at 82.1 MeV

The nucleus 12 C was bombarded by 82.1–MeV 3 He particles to study elastic and inelastic scattering and the ( 3 He, α) reaction. Angular distributions were measured for the elastic scattering, for the inelastic scattering to levels at 4.4, 7.6 and 9.6 MeV in 12 C, and for the ( 3 He, α) reaction to levels at 0.0, 2.0, 4.3(4.7) and 6.4 MeV in 11 C. The optical potential parameters were searched for to fit the 3 He elastic scattering angular distribution. The deformation parameters β 2 and β 3 for 12 C were determined from DWBA analysis. The angular distributions of a particles were compared with DWBA calculations and calculations including the two-step process via inelastic channel.

Single-particle strengths measured with 48Ca(d, p)49Ca reaction at 56 MeV

Single-particle states in 49Ca have been investigated through the 48Ca(d, p)49Ca reaction initiated by vector-polarized deuterons of Ed = 56 MeV. Thirty-six levels were observed up to 8 MeV excitations. Transferred l, j values were deduced for these levels by measured angular distributions of cross section and analyzing power. We observed many additional states and corrected some previous jπ assignments. The total values of spectroscopic factors C2S obtained with zero-range distorted-wave-Born-approximation (DWBA) calculations are almost unity for the shells 2p32, 2p12 and 1f52, and no 1f72 states are observed. It is confirmed that 48Ca has a good closed-shell structure, the feature of which is consistent with occupation probabilities predicted from an extended second RPA theory.

Semi-microscopic formula for gas gain of proportional counters

Abstract A semi-microscopic formula of Townsends first ionization coefficient α is proposed for the gas gain of a proportional counter. The electron movement in a counter is expressed in terms of cross sections of inelastic and ionization collisions with gas molecules by introducing a simple model which has four fixed parameters for a gas. The model parameters have been determined for typical counter gases. The results of gas gain calculated by the obtained formula indicate good agreement with experimental results for several filling gas mixtures at a variety of mixing ratios and for various counter geometries.

Inelastic proton scattering on doubly even selenium isotopes

Abstract Measurements of elastic and inelastic proton scattering by isotopically enriched targets of 76 Se, 78 Se, 80 Se and 82 Se have been carried out using a 51.9 MeV proton beam. Inelastic proton scattering to one-phonon 2 + and 3 − states is analyzed by DWBA and coupled channel theories. The deformation parameters obtained are compared with those extracted from electromagnetic excitation, and the prescription of Madsen, Brown and Anderson for the difference of deformation parameters for different transitions has been tested. Additional information on one-phonon cotupole (3 − ) states in 76 Se, 78 Se, 80 Se and 82 Se is presented.

A counter-telescope consisting of tandem proportional counters and a lithium-drifted silicon detector for charged particles produced with fast neutrons

Abstract A detailed description and characteristics are given of a counter-telescope for measuring precisely the energy and angular distributions of charged particles emitted in fast neutron-induced reactions. The counter-telescope consists of three identical gas proportional counters followed by a lithium-drifted silicon detector, in application of the Igo and Eisberg method. The counter-telescope has been successfully used for the measurement of recoil deutrons and breakup protons from deutrons bombarded with 14.1 MeV neutrons. The preliminary data on the D(n,p)2n reaction are also presented.