F. Gabbard

A neutron detector for measurement of total neutron production cross sections

Abstract A neutron detector has been constructed and calibrated for the accurate measurement of total neutron production cross sections. The detector consists of a polythylene sphere of 60 cm diameter in which eight 10 BF 3 counters have been installed radially. The relative efficiency of this detector has been determined for average neutron energies from 30 keV to 1.5 MeV by counting neutrons from 7 Li(p,n) 7 Be. By adjusting the radial positions of the BF 3 counters in the polythylene sphere the efficiency for neutron detection was made nearly constant for this energy range. Measurement of absolute efficiency for the same neutron energy range has been done by counting the neutrons from 51 V(p,n) 51 Cr and 57 Fe(p,n) 57 Co reactions and determining the absolute number of residual nuclei produced during the measurement of neutron yield. Details of absolute efficiency measurements and the use of the detector for determination of neutron production cross sections are given.

Cross sections and reaction rates forNa23(p, n)Mg23,Al27(p, n)Si27,Al27(α, n)P30,Si29(α, n)S32, andSi30(α, n)S33

The total neutron production cross sections for the /sup 23/Na(p,n)/sup 23/Mg, /sup 27/Al(p,n)/sup 27/Si, /sup 27/Al(..cap alpha..,n)/sup 30/P, /sup 29/Si(..cap alpha..,n)/sup 32/S, and /sup 30/Si(..cap alpha..,n)/sup 33/S reactions have been measured for bombarding energies from threshold to 6.3 MeV. The neutron detector was a 60-cm diameter sphere of polyethylene with eight /sup 10/BF/sub 3/ counters and was insensitive to the angle and energy of the emitted neutrons. Cross sections for inverse reactions have been obtained using the principle of detailed balance. The data have been used to determine parameters for statistical model calculations to facilitate extrapolation of cross sections to higher bombarding energies. These reactions are relevant to problems of nucleosynthesis and stellar evolution and to studies of radiation damage. Nucleosynthesis reaction rates, N/sub A/(sigmav), were determined for the reactions studied and are tabulated for temperatures ranging from 0.4 x 10/sup 9/ to 10.0 x 10/sup 9/ K.

2.335-MeV ISOBARIC ANALOG RESONANCE IN

The 2.335-MeV isobaric analog resonance in

sup 51

^{51}\mathrm{V}(p,n)^{51}\mathrm{Cr}

V + p AND THE EXCITED STATES OF

and

sup 51

^{51}\mathrm{V}(p,p)^{51}\mathrm{V}

Cr STUDIED VIA THE (p,n) AND (p,n

was studied experimentally. Detailed analysis was not possible because of the complexity of the excitation function in this energy region.

gamma

^{51}\mathrm{V}(p,n)^{51}\mathrm{Cr}

) REACTIONS.

angular distributions at 4.013- and 5.016-MeV bombarding energies were analyzed via statistical-model formalism. 12 states in

Energy levels ofTc96via theMo96(p, nγ)Tc96reaction

^{51}\mathrm{Cr}