[en] A method for calculating the beam current and emittance of a negative ion beam from a sputter-type source is described. Calculations are compared to measured emittance. The dependence of the emittance on ion source parameters such as cathode shape, exit aperture diameter, and cathode voltage is discussed

[en] A coupled-cavity drift-tube linac (CCDTL) combines features of the Alvarez drift-tube linac (DTL) and the π-mode coupled-cavity linac (CCL). In one embodiment, each accelerating cavity is a two-cell, 0-mode DTL. The center-to-center distance between accelerating gaps is βλ, where λ is the free-space wavelength of the resonant mode. Adjacent accelerating cavities have oppositely directed electric fields, alternating in phase by 180 degrees. The chain of cavities operates in a π/2 structure mode so the coupling cavities are nominally unexcited. The CCDTL configuration provides an rf structure with high shunt impedance for intermediate velocity charged particles, i.e., particles with energies in the 20-200 MeV range. 5 figs

[en] Over the last several years the RFQ has proved to be a very flexible low-energy accelerator for bunching and accelerating both low- and high-current beams. It uses low-voltage dc injectors, has excellent bunching properties and high transmission efficiency. Applications include injectors for higher energy machines, such as drift-tube linacs, cyclotrons, or synchrotrons. The RFQ can also be used alone for applications that require a fixed-energy beam. 41 references, 4 figures, 2 tables

[en] Calculations of the electric potential and of Cs⁺-ion trajectories explain the axially enhanced erosion of the sputter cathode in the Wisconsin Source of Negative Ions by Cesium Sputtering (SNICS) and similar sources. The effect arises from purely electrostatic focusing of fast Cs⁺ ions that are produced on a hot refractory-metal surface. Calculations which include the effects of a 1-mA Cs⁺ beam suggest that space charge is of only minor importance in this type of ion source. Possible improvements in the efficiency of the ionizer that arise from modifications to the source geometry are also discussed

[en] Reports of operations are presented for twenty-seven facilities, along with reports on accelerators in progress, ion sources, insulating gases, charging systems, stripping foils, accelerating tubes, and upgraded accelerator systems

[en] This paper reports low-power tuning and stabilization measurements on the Los Alamos Ramped-Gradient Drift-Tube Linac (RGDTL). The RGDTL is a 425-MHz, 1.87-m-long structure containing 29 drift tubes, 14 post couplers, 2 tuners, and 2 drive loops. The design calls for an axial electric field gradient that increases from 2.0 MV/m to 4.4 MV/m over 1.5 m for accelerating H/sup /minus// from 2.07 to 6.67 MeV. Asymmetric post couplers adjacent to every other drift tube both stabilize and ramp the field. The two tuners provide 1.4 MHz of dynamic frequency adjustment around the frequency selected by a one-time trimming of two tuning bars that are bolted inside the tank alongside the drift-tube stems. Field measurements obtained by the bead-perturbation method determine how to adjust the post couplers for the desired ramp. Comparison of two field distributions for different deliberate frequency perturbations quantifies the structure's tilt sensitivity and indicates whether to tune the post coupler frequencies lower or higher with respect to the TM₀₁₀ accelerating mode frequency. 3 refs., 6 figs., 1 tab

[en] Data are reported on the elastic scattering of alphas by ¹⁶O and on the inelastic scattering to the first five excited states of ¹⁶O in 10 keV steps for 14.6 < E/sub α/ < 20.4 MeV. Surface barrier detectors at sixteen to eighteen angles in a differentially pumped gas chamber measured simultaneously the differential cross section. Several computer programs were developed for online data acquisition and monitoring, for rapidly reducing data to cross sections, for updating and editing data tapes, and for plotting the cross sections as either angular distributions or as excitation functions. For each particle spectrum in the bombarding energy range 18.0 < E/sub α/ < 20.4 MeV by peak fitting techniques the α₁ and α₂ peaks (which correspond to ¹⁶O final states at excitation energies 6.0494 and 6.1304 MeV were separated. The 246 angular distributions for each of the five inelastic scattering reactions in this energy range were expanded in Legendre polynomials. The simple spin system for the α₁ reaction (0⁺ + 0⁺ → 0⁺ + 0⁺) permitted the assignment of spin-parities to eleven resonances in the compound nucleus ²⁰Ne at excitation energies from 19.1 to 21.0 MeV. To extract resonant energies and widths from both the α₁ and the α₀ data the scattering amplitude is written as a linearly energy dependent nonresonant term plus a sum over only resonant partial waves. The analysis of the elastic scattering data confirmed spin-parity assignments for three levels in ²⁰Ne at (J/sup pi/ in parentheses) E/sub x/ = 16.844 (5^-), 18.119 (7^-) and 20.685 MeV (9^-) and permitted unambiguous J/sup pi/ assignments for five levels at E/sub x/ = 16.501 (6⁺), 16.666 (4⁺), 17.150 (5^-), 17.273 (4⁺) and 18.023 MeV (5^-). Also identified were three previously unreported ²⁰Ne levels at E/sub x/ = 16.576 MeV (7^-), GAMMA/sub c.m./ = 86 keV; 16.633 MeV (3^-), 51 keV; and 27.204 (4⁺), 142 keV

[en] The EN tandem Van de Graaff facility is described. Pelletron charging chains were replaced after 52,804 hours of operation. A polarimeter was installed to monitor either proton as deuteron polarization at the exit of the analyzing magnet. Work on a Cs gun for the colliding-beam polarized ion source is described. Computer codes have been developed to model the operation of the sputter ion source. A RF buncher for deuterons with energies between 10 and 60 keV has been installed to improve time-of-flight measurements

[en] The National Spallation Neutron Source (NSNS) requires a linac that accelerates a H^- beam to 1.0 GeV. The linac starts with a radio-frequency quadrupole (RFQ) accelerator, which is followed by a drift-tube linac (DTL), a coupled-cavity drift-tube linac (CCDTL), and a conventional coupled-cavity linac (CCL). In this paper, the authors focus on the DTL, CCDTL, and CCL parts of the accelerator. They discuss the linac design parameters and beam dynamics issues. The design rationale of no separate matching sections between different accelerating sections maintains the current independence of beam behavior

[en] We examine ion linac designs that start with a high energy radio- frequency quadrupole (RFQ) followed by either a drift-tube linac (DTL) or a coupled-cavity drift-tube linac (CCDTL). For high energies a conventional CCL follows the CCDTL. High RFQ output energy allows tailoring the transverse and longitudinal focusing strengths to match into the following structure. When the RFQ beam enters a higher frequency structure, the DTL or CCDTL starts with a low accelerating gradient and large negative synchronous phase. The gradient and phase both ramp up gradually to higher values. Other changes later in the machine are also gradual. Beam dynamics simulations show that these linacs require no separate matching sections. Applications include a cw 100 mA H⁺ beam from a 350-MHz, 6.7 MeV RFQ injecting a 700 MHz CCDTL and CCL; a 7% duty 28 mA H^- beam from a 402.5 MHz RFQ and DTL injecting 805 MHz structures; a cw 135 mA D⁺ beam produced by a 175 MHz, 8 MeV RFQ and DTL; and a 2.4% duty, 80 mA H⁺ beam using a 433 MHz 10 MeV RFQ and a 1300 MHz CCDTL. The machines take advantage of the considerable flexibility of the CCDTL. Designs can use a variety of different transverse focusing lattices. Use of two coupling cavity orientations permits a constant period even when the number of drift tubes per cavity changes along the linac