P. D. Harty

The 150-MeV photon tagging system at Sendai

Abstract A description is given of the 32-channel photon tagging system recently constructed at the Laboratory of Nuclear Science. Tohoku University. Some results of photonuclear experiments performed using this system in conjunction with the high duty factor electron beam from the pulsed beam stretcher are presented.

Measurement of theHe4(γ,n)reaction from23<Eγ<70MeV

A comprehensive set of {sup 4}He({gamma},n) absolute cross-section measurements was performed at MAX-lab in Lund, Sweden. Tagged photons from 23<E{sub {gamma}}<70 MeV were directed toward a liquid {sup 4}He target, and neutrons were identified using pulse-shape discrimination and the time-of-flight technique in two liquid-scintillator detector arrays. Seven-point angular distributions have been measured for 14 photon energies. The results have been subjected to complementary transition-coefficient and Legendre-coefficient analyses. The results are also compared to experimental data measured at comparable photon energies as well as recoil-corrected continuum shell-model, resonating group method, and effective interaction hyperspherical-harmonic expansion calculations. For photon energies below 29 MeV, the angle-integrated data are significantly larger than the values recommended by Calarco, Berman, and Donnelly in 1983.

Measurement of the {sup 4}He({gamma},n) reaction from 23<E{sub {gamma}}<70 MeV

A comprehensive set of 4He(,n) absolute cross-section measurements was performed at MAX-lab in Lund, Sweden. Tagged photons from 23<E<70 MeV were directed toward a liquid 4He target, and neutrons were identified using pulse-shape discrimination and the time-of-flight technique in two liquid-scintillator detector arrays. Seven-point angular distributions have been measured for 14 photon energies. The results have been subjected to complementary transition-coefficient and Legendre-coefficient analyses. The results are also compared to experimental data measured at comparable photon energies as well as recoil-corrected continuum shell-model, resonating group method, and effective interaction hyperspherical-harmonic expansion calculations. For photon energies below 29 MeV, the angle-integrated data are significantly larger than the values recommended by Calarco, Berman, and Donnelly in 1983. (Less)

(γ,2N) reaction in 12 C

The {sup 12}{ital C}({gamma},{ital pn}) and {sup 12}{ital C}({gamma},{ital pp}) reactions have been measured for photon energies between 80 and 157 MeV using a photon tagging spectrometer and plastic scintillator detectors. The overall energy resolution was {similar_to}7 MeV, sufficient to determine the initial shells of the emitted nucleons. Corrections were made for solid angle and threshold effects by means of Monte Carlo simulations. For the ({gamma},{ital pn}) reaction both the missing energy and recoil momentum distributions are largely consistent with a two-nucleon absorption process on {ital p}-shell an {ital sp} nucleon pairs. For the much smaller {sup 12}{ital C}({gamma},{ital pp}) cross section the reaction mechanism is not yet understood but the recoil momentum distributions suggest that final state interactions are not dominant.

({gamma},2{ital N}) reaction in {sup 12}C

The {sup 12}{ital C}({gamma},{ital pn}) and {sup 12}{ital C}({gamma},{ital pp}) reactions have been measured for photon energies between 80 and 157 MeV using a photon tagging spectrometer and plastic scintillator detectors. The overall energy resolution was {similar_to}7 MeV, sufficient to determine the initial shells of the emitted nucleons. Corrections were made for solid angle and threshold effects by means of Monte Carlo simulations. For the ({gamma},{ital pn}) reaction both the missing energy and recoil momentum distributions are largely consistent with a two-nucleon absorption process on {ital p}-shell an {ital sp} nucleon pairs. For the much smaller {sup 12}{ital C}({gamma},{ital pp}) cross section the reaction mechanism is not yet understood but the recoil momentum distributions suggest that final state interactions are not dominant.