Multiple Charge State Beam Acceleration at Atlas

A test of the acceleration of multiple charge-state uranium beams was performed at the ATLAS accelerator. A 238U+26 beam was accelerated in the ATLAS PII linac to 286 MeV (~1.2 MeV/u) and stripped in a carbon foil located 0.5 m from the entrance of the ATLAS Booster section. A 58Ni9+ 'guide' beam from the tandem injector was used to tune the Booster for 238U+38. All charge states from the stripping were injected into the booster and accelerated. Up to 94% of the beam was accelerated through the Booster linac, with losses mostly in the lower charge states. The measured beam properties of each charge state and a comparison to numerical simulations are reported in this paper.Comment: LINAC2000, MOD0

Microstructure damage of titanium films by irradiation with fission fragments

Radiation damage caused by fission fragments to metal surfaces is an important research topic. Thin titanium foils were irradiated with a continuous wave beam of 132 MeV ¹³²Xe+²⁹ at the current intensity of 2 pnA. Pre- and post-irradiated surface topologies were investigated using atomic force microscopy and the observed defects were quantified by root mean square roughness, depth profile of the disordered zones, size and areal density of the voids, and discussed as a function of the applied fluencies (1– 9) 10¹³ Xe/cm². The first ellipsoidal dislocation loops appeared at the fluence of 3.0 10¹³ Xe/cm² with the areal density of 1.56 10⁶/cm² that increased to 2.0 10⁷ cm ⁻² when the dose rose to 9.0 10¹³ Xe/ cm2. At this point also the first dislocation lines with the density of 1.3 10⁷ cm ⁻² were seen. Our results suggest that the fission fragments might maximize large voids and dislocations and increase the degradation in depth resolution.Keywords: Voids, Dislocation lines, Dislocation loop, Titanium, Radiation damag

Bunch shape measurement of CW heavy-ion beam.

An accurate bunch shape measurement is one of the most important tasks during the fine tuning of multicavity accelerators. A device for the measurement of bunch time structure of cw heavy-ion beams with time resolution {approx}20 picoseconds was developed, constructed and commissioned at ATLAS which is a 50 MV superconducting heavy-ion linac. The Bunch Shape Monitor (BSM) is based on the analysis of secondary electrons produced by a primary beam hitting a tungsten wire to which a potential of -10 kV is applied. In a BSM the longitudinal distribution of charge of the primary beam is coherently transformed into a spatial distribution of low energy secondary electrons through transverse rf modulation. The distribution of secondary electrons is detected by a chevron MCP coupled to a phosphor screen. The signal image on the screen is measured by use of a CCD camera connected to a PC. This BSM analyzes cw beams rather than pulsed beams studied by a previous device [1]. Design features of the BSM and the beam measurement results are reported

Status of the uranium upgrade of ATLAS

The ATLAS Positive Ion Injector (PII) is designed to replace the tandem injector for the ATLAS heavy-ion facility. When the PII project is complete, ATLAS will be able to accelerate all ions through uranium to energies above the Coulomb barrier. PII consists of an ECR ion source on a 350 KV platform and a very low-velocity superconducting linac. The linac is composed of an independently-phased array of superconducting four-gap interdigital resonators which accelerate over a velocity range of .007c to .05c. the PII project is approximately 75% complete. Beam tests and experiments using the partially completed PII have demonstrated that the technical design goals are being met. The design, construction status, and results of recent operational experience using the PII will be discussed. 10 refs., 2 figs., 1 tab

COMMISSIONING OF THE 72 MHz QUARTER- WAVE CAVITY CRYOMODULE AT ATLAS*

Abstract A cryomodule of seven 72 MHz superconducting (SC) quarter-wave cavities optimized for ions with v/c=0.077 has been commissioned in the ATLAS heavy-ion accelerator at Argonne. The new module, with the new CW RFQ injecto

Studying X-ray burst nucleosynthesis in the laboratory

Type I X-ray bursts are the most common explosions in the Galaxy; however, the nucleosynthesis that occurs during the thermonuclear runaway and explosion is poorly understood. In this proceedings we discuss current experimental efforts and techniques that are being used to study X-ray burst nucleosynthesis in the laboratory. Specifically, radioactive ion beam techniques that have recently been developed have allowed the study of some of the most important (α, p) reactions in X-ray bursts for the first time. © Published under licence by IOP Publishing Ltd

Operating experience and construction status of ATLAS

The present Argonne Tandem-Linac accelerator has operated in a reliable manner during the past year. The accelerator system provided 4402 hours of experimental beam time with a wide variety of heavy-ions. Figure 1 shows the beams which have been provided during the past year. New beams accelerated by the linac include 300 MeV /sup 82/Se and 390 MeV /sup 109/Ag. In tests, the tandem accelerated 102 MeV /sup 127/I. This is the heaviest beam ever accelerated by the Argonne tandem. The long-term performance of the niobium resonators appears to be good. No significant degradation of performance has been observed for most resonators over many years of use with the exceptions of problems caused by catastrophic vacuum accidents. Resonators whose performance has deteriorated after vacuum accidents have recently been restored to their original performance state by a simple technique. The technique used is to rinse the interior of the resonator with a sequence of baths of solvents and water