[en] An 80-MHz radio-frequency quadrupole (RFQ) linac has been designed, fabricated and operated at 100% duty factor (cw) for the Fusion Materials Irradiation Test (FMIT) project at Los Alamos. This paper describes the design features, fabrication techniques, and operational problems of the device. The RFQ is an assembly of heavy steel, copper-plated weldments. It measures about 15 ft (4.5 m) long by 5 ft (1.5 m) in diameter and weighs over 12 t. Major components are two pair of diametrically orthogonal vanes mounted in a core cylinder. The core is assembled into a manifold cylinder that couples rf power into the vane quadrants. The design features discussed include assembly of hollow wall, flood-cooled components; high-conductivity rf seals; removable and adjustable vanes; and tuning devices. Fabrication challenges such as close-tolerance weldments, vane-tip-contour machining and large-component plating requirements are covered

[en] Branching ratios for the decays of the 8.78 MeV 0₂^-; T = 1 and 8.91 MeV 3₂^-; T = 1 states in ¹⁴ N were determined following their population by proton capture on an enriched ¹³ C target. This is the first detailed study of the decay of the 0^- state; five transitions were observed. Branching ratios for the 3^- decay are in good agreement with previous results. (Author) 13 refs., 2 tabs

[en] Charge fractions for charge exchange of 6-MeV ⁷Li^- ions in H₂, N₂, O₂, and He have been measured. Cross sections for Li^- and Li⁰ destruction are derived from the target thickness dependence of the charge fractions. 12 figures, 3 tables

[en] An 80-MHz radio-frequency quadrupole (RFQ) linac has been designed, fabricated and operated at 100% duty factor (cw) for the Fusion Materials Irradiation Test (FMIT) project at Los Alamos. This paper describes the design features, fabrication techniques, and operational problems of the device. The RFQ is an assembly of heavy steel, copper-plated weldments. It measures about 15 ft (4.5 m) long by 5 ft (1.5 m) in diameter and weighs over 12 t. Major components are two pair of diametrically orthogonal vanes mounted in a core cylinder. The core is assembled into a manifold cylinder that couples RF power into the vane quadrants. The design features discussed include assembly of hollow wall, flood-cooled components; high-conductivity RF seals; removable and adjustable vanes; and tuning devices. Fabrication challenges such as close-tolerance weldments, vane-tip-contour machining and large-component plating requirements are covered

[en] The amount of ²⁶Al produced during carbon burning is determined predominantly by the rates for the ²⁵Mg(p,γ)²⁶Al and ²⁶Al(n,p)²⁶Mg reactions. Analysis of the reactions, however, must take into account the existence of ²⁶Al in two separate states which do not communicate with each other. Previously published rates for these reactions have not separated the ²⁶Al into its two components: ²⁶Al (half-life of 7.3 x 10⁵ yr); and /sup 26m/Al (half-life of 6.35 s). We have calculated stellar reaction rates for the ²⁵Mg(p,γ)²⁶Al and ²⁵Mg(p,γ)/sup 26m/Al reactions from the recent experimental data of Neijs et al. for temperatures from T₉ = 1 to T₉ = 2. We have also calculated stellar reaction rates for (p,n) and (n,p) reactions involving ²⁶Mg and both /sup 26g/Al and /sup 26m/Al using cross-section values calculated from a statistical model of nuclear reactions. Rates for the ²⁶Mg(p, n)/sup 26m/Al reaction have been compared with rates derived from experimental cross-section values in order to assess the validity of the calculations. The use of undifferentiated rates for the ²⁵Mg(p,γ)²⁶Al reaction, derived from earlier experimental data, has been found to overestimate the rate of production of /sup 26g/Al by about a factor 2 at T₉ = 2, while use of the undifferentiated ²⁶Al(n,p)²⁶Mg rate from theory overestimates the rate of destruction of ²⁶Al by at least a factor 2 and perhaps much more

[en] We have studied the Β-delayed protondecay of ¹⁷Ne to excited states of ¹⁶O by measuring proton-Β and proton-γ coincidences. A ¹⁷Ne beam of the order of 10⁵ ions/s was produced at the TRIUMF TISOL facility by bombarding a MgO target with 500 MeV protons and extracting a mass 17 beam from an on-line ECR source. The ¹⁷Ne beam passed through the center of an annular 300 μm Si detector to a collection tape. A thin plastic scintillator followed by a 45% efficient HPGe detector situated just behind the tape allowed for the detection of proton-γ and proton-γ coincidences in close geometry. The decay of the IAS in ¹⁷F to the 8.872 MeV state in ¹⁶O has been seen for the first time. Proton branching ratios for several excited states in ¹⁷F above 8 MeV will be presented

[en] The yield from the ⁵⁸Ni(p,γ)⁵⁹Cu reaction has been measured by detection of annihilation radiation in coincidence from the decay of 82 s ⁵⁹Cu. Both thin (600μg cm^-2) and thick (117 mg cm^-2) targets have been used, the latter being thick enough to stop the proton beam at all incident energies. The cross section calculated from the thin target yield contains much structure and is in reasonably good agreement with previous studies. Thermonuclear reaction rates have been calculated from both thin and thick target yields for tempertures of interest in explosive nucleosynthesis. Both thin and thick target rates are in very good agreement with previous determinations but the thin rates are, on the average, 35% higher than thick target rates. The reaction rate for T₉<=2 is shown to be strongly dependent on a resonance at 931 MeV (center of mass) whose strength is not well known. A set of rates for T₉>=2 for both ground state and stellar reactions based on thin target measurements is recommended and analytic fits to the recommended rates are given. (auth)

[en] An 80-MHz radio-frequency quadrupole (RFQ) linac has been designed, fabricated and operated at 100% duty factor (cw) for the Fusion Materials Irradiation Test (FMIT) project at Los Alamos. This paper describes the design features, fabrication techniques, and operational problems of the device. The RFQ is an assembly of heavy steel, copper-plated weldments. It measures about 15 ft (4.5 m) long by 5 ft (1.5 m) in diameter and weighs over 12 t. Major components are two pair of diametrically orthogonal vanes mounted in a core cylinder. The core is assembled into a manifold cylinder that couples rf power into the vane quadrants. The design features discussed include assembly of hollow wall, flood-cooled components; highconductivity rf seals; removable and adjustable vanes; and tuning devices. Fabrication challenges such as close-tolerance weldments, vane-tip-contour machining and large-component plating requirements are covered

[en] Ground-state reaction rates have been deduced from recent cross section measurements for the ⁴²CA(α, n)⁴⁵Ti, ⁴²Ca(p, γ)⁴³Sc, and ⁴⁴Ca(p, n)⁴⁴Sc reactions. Comparison of these rates with those calculated from a statistical model of nuclear reactions. (Woosley et al) shows good agreement for the first two, but the ⁴⁴Ca(p, n) rate is more than a factor of 2 less than the theoretical prediction. Stellar reaction rates have been derived from the ground-state rates by multiplying the ground-state rates by the ratio of stellar to ground-state rates given by the statistical model. Both ground-state and stellar rates have been represented by analytic functions of the temperature. The role of these reactions in the approach to quasi-equilibrium during explosive silicon burning is discussed

[en] The cross section for the ⁴²Ca(p,γ)⁴³Sc reaction has been measured over the lab energy range from 0.7 to 5.5 MeV using a positron spectrometer to measure the annihilation radiation from the decay of 3.9 h ⁴³Sc. Stellar reaction rates Nsub(A) have been calculated from the experimental cross section curve for a series of three temperatures of interest for explosive oxygen and silicon burning in stars. The calculated rates are compared with the theoretical predictions of Woosley et al. and found to be in agreement within the experimental errors and the quoted validity of the theoretical calculation. (Auth.)