B. Zeitnitz

Elastic neutron-deuteron scattering in the energy range from 2.5 MeV to 30 MeV

Abstract The differential cross section of the elastic neutron-deuteron scattering has been measured in the energy range from 2.5 MeV to 30 MeV using a continuous energy neutron beam and a deuterated scintillating scattering sample. Angular distributions were determined including also backward angles near 180°. The comparison with the total cross section for the neutron-deuteron interaction, which was also measured between 2 MeV and 40 MeV with high accuracy, has been used for the extraction of the inelastic cross section. The overall uncertainties of most data points are below 6%. This is an increase in accuracy by a factor of 2 to 10 compared to earlier measurements. The high quality of our results allows conclusive comparison with pd data and with the predictions of exact three-nucleon calculations. In addition, Coulomb correction procedures to Faddeev calculations can be tested.

Neutron-neutron effective range parameters from kinematically complete experiments on the reaction 2H(n, 2n)1H

Abstract In simultaneous complete experiments on the reaction 2 H(n, 2n) 1 H neutron-neutron and neutron-proton final-state interactions were observed. The experiments were analysed with three-body calculations using different form factors for the nucleon-nucleon interactions. The analysis with a complete charge dependent calculation using exponential form factors gave a nn = −16.3 ± 1.0 fm for the 1 S 0 neutron-neutron scattering length and r nn = 2.13 ± 0.4 fm for the effective range.

Neutron scattering from 15N: (I). R-matrix and phase-shift analyses

Abstract The total neutron cross section of 15 N was measured in the neutron energy range between 0.9 and 32 MeV. Between 0.8 and 3.1 MeV angular distribution and polarization measurements were performed. Assignments for levels in 16 N up to E x = 6.7 MeV could, be determined using R -matrix and phase-shift analyses. The positions of the d 3 2 single-particle resonances were established. Above E x = 6.7 MeV estimates of the angular momenta were obtained from the total cross section by the 2 J + 1 rule.

Investigation of the reaction 2H(n, np) at θn = 0°

Abstract The differential cross section of the 2 H(n, np) reaction was measured at θ n = 0°. Because of the applied special geometry the experimental data extend over a large fraction of the phase space, including several final state interaction regions as well as regions far from the dominance of quasi-two-body processes. The experiment was analysed with an exact three-body calculation using s-wave separable potentials (CEE). The analysis of the n-n and n-p final state interaction peaks gave a nn = −16.3 ± 1.6 fm for the n-n 1 S 0 scattering length and r nn = 3.15 ± 0.7 fm for the effective range. Remarkable deviations from the calculated cross sections-were found in regions where no strong final state interaction was present.

Determination of the neutron-neutron scattering length from a kinematically complete experiment on the reaction 2H(n, 2n)H

Abstract The coincident neutron spectra from the reaction 2 H(n, 2n)H at E n = 18.5 MeV ( θ 1 = 24.2°, θ 2 = 31.2°) have been measured with a double time-of-flight spectrometer. The data were analysed in the Watson-Migdal approximation, using a Monte Carlo technique. The results give a nn = −16.4 −2.9 +2.6 fm for the 1 S 0 neutron-neutron scattering length.

Neutron-neutron scattering length from a complete experiment on the reaction D (n, 2n) H

Abstract The coincident neutron spectra from the reaction D(n,2n)H at E n = 18.5 MeV ( θ 1 = 24.2°, θ 2 = 31.2°) have been measured with a double time-of-flight spectrometer. With Watsons final-state interaction theory the results give a nn = − 16.4 ± 2.9 fm for the 1 S O n-n scattering lenght.

Lifetime of the 3.46 MeV state of 41Sc by proximity scattering measurements

Abstract Neutron-proton scattering following the sequential decay 40Ca(d, n)41Sc∗ (p)40Ca has been measured to determine the lifetime of the intermediate state at 3.46 MeV excitation energy in 41Sc. A value of (4−1.5+2) × 10−21s has been obtained from the evaluation of the n-p rescattering intensity.

Analysing power in neutron-proton and neutron-deuteron scattering at 14 MeV

Abstract Analysing power data in n-p and n-d elastic scattering at 14 MeV were deduced from asymmetry measurements using a polarized neutron beam arrangement consisting of a gas target cell, a neutron collimator and a spin processing solenoid. The incident neutron beam was produced by the reaction 2 H ( d) , n ) 3 He at θ lab = 30° . The neutron polarization was P = (42.9 ±0.9)%. Liquid scintillators of C 6 H 6 and C 6 D 6 were used as scattering targets. Eight neutron detectors allowed the simultaneous measurement of the asymmetry at different angles. The n-p analysing power data were used to perform new phase-shift analyses, including all available n-p scattering data in this energy region. The results for the n-p analysing power at 14.5 MeV were found to be slightly different from the predictions of the Livermore (LRL X) as well as from those of the Yale (Y IV) phase-shift sets. The results for the n-d analysing power at 14.3 MeV show no significant difference to the p-d data at this energy. Three-particle calculations from Dolescball and from Benayoun et al. give reasonable agreement with the experimental data although there are still some minor deviations.

Analyzing power of the n-3He elastic scattering from 3.7 to 22.0 MeV

Abstract Measurements of the analyzing power A y of elastic n- 3 He scattering in the energy range from 3.7 to 22 MeV are reported. These data improve considerably the precision of the data around 3 MeV. Recent results in the range 8 to 17 MeV are supplemented. The data at 22 MeV are not in agreement with a previous experiment which caused problems in phase-shift analyses. A comparison of the new data with n- 3 H, p- 3 H and p- 3 He analyzing powers shows only small Coulomb effects but strong dependence on the isospin structure of the intermediate A = 4 system.

Neutron polarization from the reaction 14C(d,n)15N

Abstract The polarization of the neutrons from the reaction 14 C(d, n 0 , n 1+2 , n 3 ) 15 N was measured for deuteron energies between 2.0 and 3.3 MeV. At 2.68 and 3.00 MeV complete angular distributions up to 155° lab were determined. This was done by a neutron polarimeter with a liquid-helium scintillator.