F.H. Munson

The positive-ion injector of ATLAS: Design and operating experience

Abstract The recently completed positive-ion injector for the heavy-ion accelerator ATLAS is a replacement for the tandem injector of the present tandem-linac system. Unlike the tandem, the new injector provides ions from the full range of the periodic table. The concept for the new injector, which consists of an ECR ion source on a voltage platform coupled to a very-low-velocity superconducting linac, introduces technical problems and uncertainties that are well beyond those encountered previously for superconducting linacs. The solution to these problems and their relationship to performance are outlined, and experience in the operation of ATLAS with its new injector is discussed.

Current status of ATLAS and proposed expansion to an exotic beam facility

The Argonne Tandem Linear Accelerator System (ATLAS) has been operating on a twenty-four hour, seven days a week schedule since the beginning of Fiscal Year 1994. Twenty-six different ion species ran during this period in 71 separate experiments. During the past year, there have been many projects undertaken to improve operation efficiency and upgrade various accelerator systems. There is also a new ECR ion source construction project underway. This paper covers, linac operation and new tuning techniques, the second generation ECR source construction project, the refrigerator system upgrade, an upgrade to the control system. Also described is a future expansion of ATLAS as an Exotic Beam Facility. ATLAS is a world class heavy ion accelerator with an estimated value of approximately

Status of the positive ion injector for atlas

80 million. A concept that would utilize ATLAS as the foundation for a facility to generate and accelerate radioactive beams is briefly discussed.

First operational experience with the positive-ion injector of ATLAS

The positive ion injector project will replace a High Voltage Engineering Corp. model FN 9 MV tandem electrostatic accelerator as the injector into the ATLAS superconducting heavy ion linear accelerator. It consists of an electron cyclotron resonance (ECR) ion source on a 350-kV platform injecting into a linac of individually phased superconducting resonators which have been optimized for ions with velocities as low as ..beta.. = 0.009. The resulting combination will extend the useful mass range of ATLAS to projectiles as heavy as uranium, while increasing the beam currents available by a factor of 100. (2 refs., 2 figs., 1 tab.)

Operational status of the uranium beam upgrade of the ATLAS accelerator

Abstract A Positive-Ion Injector (PII) designed to enable ATLAS to accelerate all stable nuclei has been completed and successfully tested. This new injector system consists of an ECR source on a 350-kV platform coupled to a 12-MV superconducting injector linac formed with four different types of independently-phased 4-gap accelerating structures. The injector linac is configured to be optimum for the acceleration of uranium ions from 0.029 to ≈ 1.1 MeV/u. When ions with q/A > 0.1 are accelerated by PII and injected into the main ATLAS linac, CW beams with energies over 6 MeV/u can be delivered to the experimental areas. Since its completion in March 1992, PII has been tested by accelerating 30 Si 7+ , 40 Ar 11+ , 132 Xe 13+ , and 208 Pb 24+ . For all of these, transmission through the injector linac was ∼100% of the pre-bunched beam, which corresponds to ∼60% of the DC beam from the source. The accelerating fields of the superconducting resonators were somewhat greater than the design goals, and the whole system ran stably for long periods of time.

Operational experience of the atlas accelerator

The Positive-Ion Injector (PII) for ATLAS is complete. First beams from the new injector have been accelerated and used for experiments at ATLAS. The POI consists of an ECR ion source on a 350-kV platform and a low-velocity superconducting linac. The first acceleration of uranium for the experimental program has demonstrated that the design goals of the project have been met, Since the summer of 1992, the new injector has been used for the research program approximately 50% of the time. Longitudinal beam quality from the new injector has been measured to be significantly better than comparable beams from the tandem injector. Changes to the mix of resonators in the main ATLAS accelerator to match better the velocity profile for heavy beams such as uranium are nearly complete and uranium energies up to 6.45 MeV per nucleon have been achieved. The operating experience of the new ATLAS facility will be discussed with emphasis on the measured beam quality as well as achieved beam energies and currents.<<ETX>>

First operational tests of the positive-ion injector for ATLAS

Abstract The ATLAS accelerator consists of a HVEC model FN tandem accelerator injecting into a linac of independently-phased niobium superconducting resonators. The accelerator provides beams with masses 6⩽A⩽127 and with energies ranging up to 20 MeV/A for the lightest ions and 4 MeV/A for the heaviest ions. Portions of the linac have been in operation since 1978 and, over the last decade, more than 35000 h of operating experience have been accumulated. The long-term stability of niobium resonators, and their feasibility for use in heavy-ion accelerators is now well established.

Status of the uranium upgrade of ATLAS

The status of and the first operational experience with the he positive-ion injector for ATLAS are summarized. The new injector consists of an ECR (electron cyclotron resonance) ion source on a 350-kV platform followed by a superconducting injector linac of a new kind. In the first phase of this project, the ECR source, voltage platform, bunching system, beam-transport system, and a 3-MV injector linac were completed and tested in early 1989 by the successful acceleration of a /sup 40/Ar/sup 12+/ beam. Most of the new system operated as planned, and the longitudinal emittance of the 36-MeV beam out of the injector was measured to be only 5 pi keV-ns, much smaller than the emittance for the present tandem injector. When completed in 1990, the final injector linac will be enlarged to 12 MV, enough to allow the original ATLAS linac to accelerate uranium ions up to 8 MeV/u.<<ETX>>

Initial use of the positive-ion injector of ATLAS

The ATLAS (Argonne Tandem Linear Accelerator System) 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 0.007 c to 0.05 c. 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 are discussed.<<ETX>>