C.M. Jones

Neutrons from the proton bombardment of Li6, Li7, Be9, B11 and O18

Abstract The total neutron yield from proton bombardment has been measured for Li 6 from threshold to 14 MeV; for Li 7 , Be 9 and B 11 from 4 to 14 MeV; and for O 18 from 3.5 to 10 MeV. The Li 6 (p, n)Be 6 reaction Q value measured in this experiment is −5.05±0.05 MeV, giving a Be 6 mass excess of 18.36±0.05 MeV. The neutron yield from Li 7 at higher energies cannot be explained on the basis of the (p, n) reaction alone and is ascribed in part to multi-particle breakup. An anomaly in the Be 9 +p neutron yield curve is ascribed to a threshold for production of neutrons by a state in B 9 at 4.04 MeV. The B 11 (p, n)C 11 reaction results confirm previous level structure in C 12 and a new “level” at E p = 11.85 MeV (energy of excitation in C 12 of 26.81 MeV.) The O 18 +p neutron yield shows 21 “resonant” peaks (energy of excitation 11.4 to 16.8 MeV).

Evaluation of carbon stripper foils for heavy-ion accelerators

Abstract Carbon foils of thickness 2–10 μg/cm 2 were produced by vapor deposition and by dc glow discharge cracking of hydrocarbon gas. Their lifetimes to mechanical failure, under bombardment with 10 MeV 35 Cl ions, were determined. Foils produced by the glow discharge technique have lifetimes ranging from 5 to over 20 times longer than those produced by vapor deposition. The glow discharge foils are also found to exhibit a strong correlation between lifetime and thickness. Changes in foil thickness with increasing fluence are examined and evidence for sputtering is obtained from beam-scanning.

Phase space acceptance and emittance in beam transport with application to tandem accelerators

Abstract Phase space acceptance and emittance ellipse areas for a region bounded by beam-limiting apertures of half widths r 1 and r 2 are shown to be πr 1 r 2 /| a 12 | and πr 1 r 2 D /| a 12 |, respectively, for linear beam transport in which D is the determinant of the basic 2×2 portion of the standard beam transport matrix and a 12 is the matrix element which transforms initial divergence into final displacement. A technique of analysis using these and related results is demonstrated for typical beam transport components. Examples are given for analyzing and optimizing beam transport through tandem electrostatic accelerators.

The 90Zr(d, n)91Nb and 96Zr(d, n)97Nb reactions

Abstract The (d, n) reaction on 90 Zr and 96 Zr has been studied at 12 MeV deuteron bombarding energy using the neutron time-of-flight technique with an overall neutron time resolution of 1.9 ns. Angular distributions of neutron groups leading to states in 91 Nb and 97 Nb were measured in the angular range between 15° and 60°. The measured cross sections were analyzed in the framework of the distorted-wave theory of stripping reactions to deduce l -values and proton spectroscopic factors of states in the residual nuclei. The results are compared with the corresponding data available from ( 3 He, d) studies. The fractionation of the single-particle proton states and their centroid energies are determined.

The 25 MV tandem accelerator at oak ridge

A new heavy-ion accelerator facility is under construction at the Oak Ridge National Laboratory. A brief description of the scope and status of this project is presented with emphasis on the first operational experience with the 25 MV tandem accelerator.

A scattering chamber for gaseous targets

Abstract A recently constructed charged particle gaseous target scattering chamber is described and some of its operating properties are discussed.

The 18O(α, p) reaction and the beta decay of 21F

Abstract The 18O(α, p)21F reaction has been studied in the bombarding energy range 7.78 to 9.95 MeV by observing, with approximately 2π geometry, the beta particles following the 21F decay. Prominent peaks in the yield curve occur at incident particle laboratory energies of about 7.86, 8.36, 8.61, 8.71, 8.83, 8.94, 9.16, 9.28, 9.43 and 9.82 MeV. The observed width of the peaks exceeds the experimental resolution of about 20 KeV. A half-life of 4.35±0.04 sec was determined for the 21F beta decay.

Absolute charge state yields of 20 MeV 127I Ions emerging from a gas stripper

Abstract Absolute charge state yields of 20 MeV 127 I ions emerging within cone half angles of 4, 6, and 8 mrad from a differentially pumped gas cell of length 9.4 cm have been measured using N 2 , Ar, Kr, and Xe stripper gases. Measurements were made over a pressure range of 0.01–0.2 torr. Data are presented which illustrate the influence of cell pressure and included solid angle on the total charge state yield from each of the gases. In this study, particular emphasis was placed on measurements which will be useful in the design and operation of tandem accelerator gas strippers.

Some experimental techniques used in a precision charged particle absolute cross section measurement

Abstract In the course of a recent precision cross-section measurement utilizing solid-state detectors in a gaseous target scattering chamber, many effects which determine the shape and character of observed spectra were investigated experimentally. Data are presented on (1) slit edge scattering, (2) gas target scattering compensation processes, (3) detector efficiency, (4) gas scattering spectrum shape, (5) solid state detector response, and (6) incoming beam energy degradation.

A simple trap for high pressure gas targets

Abstract A combined pump and trap is described which is capable of removing condensable impurities from high pressure gas targets.