J. L. Ullmann

A detector for (n,γ) cross-section measurements at a spallation neutron source

Abstract The quest for improved neutron capture cross-sections for advanced reactor concepts, transmutation of radioactive wastes as well as for astrophysical scenarios of neutron capture nucleosynthesis has motivated new experimental efforts based on modern techniques. Recent measurements in the keV region have shown that a 4 π BaF 2 detector represents an accurate and versatile instrument for such studies. The present work deals with the potential of such a 4 π BaF 2 detector in combination with spallation neutron sources, which offer large neutron fluxes over a wide energy range. Detailed Monte Carlo simulations with the GEANT package have been performed to investigate the critical backgrounds at a spallation facility, to optimize the detector design, and to discuss alternative solutions.

Background identification and suppression for the measurement of (n,γ) reactions with the DANCE array at LANSCE

Abstract In the commissioning phase of the DANCE project (Detector for Advanced Neutron Capture Experiments) measurements have been performed with special emphasis on the identification and suppression of possible backgrounds for the planned (n,γ) experiments. This report describes several background sources, observed in the experiment or anticipated from simulations, which will need to be suppressed in this and in similar detectors that are planned at other facilities. First successes are documented in the suppression of background from scattered neutrons captured in the detector as well as from the internal radiation. Experimental results and simulations using the GEANT code are compared.

Proton-induced cross sections relevant to production of 225Ac and 223Ra in natural thorium targets below 200 MeV

Cross sections for (223,)(225)Ra, (225)Ac and (227)Th production by the proton bombardment of natural thorium targets were measured at proton energies below 200 MeV. Our measurements are in good agreement with previously published data and offer a complete excitation function for (223,)(225)Ra in the energy range above 90 MeV. Comparison of theoretical predictions with the experimental data shows reasonable-to-good agreement. Results indicate that accelerator-based production of (225)Ac and (223)Ra below 200 MeV is a viable production method.

225Ac and 223Ra production via 800 MeV proton irradiation of natural thorium targets

Cross sections for the formation of (225,227)Ac, (223,225)Ra, and (227)Th via the proton bombardment of natural thorium targets were measured at a nominal proton energy of 800 MeV. No earlier experimental cross section data for the production of (223,225)Ra, (227)Ac and (227)Th by this method were found in the literature. A comparison of theoretical predictions with the experimental data shows agreement within a factor of two. Results indicate that accelerator-based production of (225)Ac and (223)Ra is a viable production method.

Total cross sections for production of7Be,22Na, and24Na inp+7Li andp+27Al reactions at 495 and 795 MeV

Activation techniques have been used to measure the total cross section for the production of {sup 7}Be, {sup 22}Na, and {sup 24}Na in proton induced reactions on {sup 7}Li and {sup 27}Al targets at bombarding energies of 495 MeV and 795 MeV. The cross section for the {sup 7}Li(p,n){sup 7}Be(g.s.+0.43-MeV) reaction at 795 MeV is about 11{endash}15{percent} larger than extrapolations based on previous data below 480 MeV. {copyright} {ital 1997} {ital The American Physical Society}

Spin measurements for

We have determined the spins

^{147}

J

Sm

of resonances in the

+n

^{147}\mathrm{Sm}

resonances: Further evidence for non-statistical effects

(