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February, 2007
VENUS Achieves Record-Breaking Beams

VENUS, the Versatile ECR Ion Source for Nuclear Science installed at the 88-Inch Cyclotron, recently achieved record currents of highly charged uranium ions, an important milestone in demonstrating that superconducting technology can meet the demands of future heavy-ion accelerators.

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VENUS, the Versatile ECR Ion Source for Nuclear Science, feeds highly charged ions to the 88-Inch Cyclotron.

VENUS was designed and built by members of Berkeley Lab's Nuclear Science Division in collaboration with the Accelerator and Fusion Research Division's Superconducting Magnet Group and members of the Engineering Division. It is the highest-performing ion source of its kind in the world and serves as the prototype injector source for the proposed Rare Isotope Accelerator (RIA), one of the Department of Energy's top-priority new facilities. Intended to study everything from nuclear structure to astrophysics, the RIA will require a flexible ion source that can deliver intense beams of ions of all kinds of elements, ranging from protons (bare hydrogen nuclei) to uranium atoms that have been stripped of dozens of their surrounding electrons.

This is the kind of challenge the VENUS ECR source was built to meet. ECR stands for electron cyclotron resonance, which describes the way free electrons spiral in the magnetic fields at the heart of the device. VENUS produces medium- and high-charge-state ions by confining them in a dense, stable plasma — a kind of gas of positively and negatively charged particles too hot to combine into neutral atoms — long enough for collisions among the particles to knock more and more electrons off the atoms.

The ability to confine a dense plasma for a long time while it is superheated by high-frequency microwaves depends on superconducting magnets capable of withstanding their own immense forces. VENUS was the first ion source in the world to build such a strong confinement structure and holds the world record for the highest ECR confinement field ever achieved.

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Daniela Leitner heads the 88-Inch Cyclotron's ECR Ion Source Group.

To its string of records VENUS has now added the highest intensity beams of high-charge-state uranium ions ever achieved, producing a current of more than 33 electrical microamperes of uranium ions having plus-33 and plus-34 charge states — eight to ten times more than nonsuperconducting ECRs have been able to produce.

"These results demonstrate for the first time that the high demands of the next generation of heavy-ion accelerators can be met," says Daniela Leitner, Berkeley Lab nuclear scientist and leader of the 88-Inch Cyclotron's ECR Ion Source Group. "However, a lot of R&D still needs to be done before VENUS is ready for the long experimental runs of an operational facility."

Current and former members of the team that developed VENUS include Leitner, Claude Lyneis, and Damon Todd of the Nuclear Science Division; Clyde Taylor and David Grote of the Accelerator and Fusion Research Division; and Matthaeus Leitner, Steve Abbott, the late Roger Dwinell, Tim Loew, Steve Virostek, Gudrun Kleist, and Dennis Collins of the Engineering Division.

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