ANL, Argonne
The ATLAS facility provides beams of essentially all stable isotopes at energies above the Coulomb barrier for nuclear physics research. We have developed a two-stage ATLAS upgrade plan which includes the replacement of aging split-ring cavities by high-performance quarter-wave resonators (QWR) capable of accelerating ~100 pμA ion beams. The first stage of the upgrade project funded through the American Recovery and Reinvestment Act includes accelerator efficiency increase by adding a new RFQ injector, development and construction of a new cryomodule containing up to 3 SC solenoids and 8 QWRs. A new 72.75 MHz resonator is designed for an optimum ion velocity β=0.075. To achieve record high accelerating voltage ~2.5 MV at this very low velocity range, EM properties of the resonator are highly optimized to reduce peak surface fields. The resonator will be equipped with a piezoelectric fast tuner and capacitive coupler to transmit several kilowatts of RF power. The vast experience gained during the development, commissioning and operation of the ATLAS energy upgrade cryomodule [1] will be applied for the design of the new cryomodule.
[1] J. Fuerst. ATLAS Energy Upgrade Cryomodule, these Proceedings.
ANL, Argonne
A new large 2 Kelvin test cryostat is being commissioned at Argonne National Laboratory. This system will have a full time connection to the 4.5 Kelvin ATLAS refrigerator and, with integrated J-T heat exchanger, will allow continuous 2 Kelvin operation. The large diameter was chosen to accommodate essentially all of today’s superconducting cavities and the top loading design facilitates clean room assembly. The commissioning run will be with a coaxial half wave cavity to be followed by testing with 1.3 GHz single-cell elliptical cavities. Details of the initial engineering cool down on the cryostat are presented.
