ANL, Argonne
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
The ongoing energy upgrade of the heavy-ion linac ATLAS at ANL includes a new cryomodule containing seven 109MHz β=0.15 quarter-wave superconducting cavities to provide an additional 15 MV voltage. Several new features have been incorporated into both the cavity and cryomodule design. For example, the cryomodule separates the cavity vacuum space from the insulating vacuum, a first for TEM cavities. The cavities are designed in order to cancel the beam steering effect due to the RF field. Clean techniques have been applied to achieve low-particulate rf surfaces and are essential for reliable long-term high-gradient operation. The sealed clean subassembly consisting of cavities, beam spools, beam valves, couplers, vacuum manifold, and support frame has been attached to the top plate of the cryomodule outside the clean room. Initial commissioning results are presented. The module was designed and built as a prototype for the Facility for Rare Isotope Beams (FRIB) driver linac, however, a similar design can be effectively used in the front-end of SC proton linacs based on TEM-class SC cavities.
CERN, Geneva
For the post-accelerator of radioactive ion beams at CERN a major upgrade is planned to take place in the next 4-5 years. The upgrade consists in boosting the energy of the machine from 3MeV/u up to 10 MeV/u with beams of mass-to-charge ratio 2.5<A/q<4.5 and in replacing part of the existing normal conducting linac. The new accelerator is based on two gap independently phased 101.28 MHz Nb sputtered superconducting Quarter Wave Resonators (QWRs). Two cavity geometries, “low” and “high” β, have been selected for covering the whole energy range. A R&D program has started in 2008 looking at the different aspects of the machine, in particular beam dynamics studies, high β cavity development and cryomodule design. A status report of the different activities is given here.
GSI, Darmstadt
HIT, Heidelberg
The Therapy Linac in Heidelberg (HIT) was successfully commissioned in 2006. Required beam parameters were reached except of the beam intensity. The achieved particle transmission for C4+ (design ion) is significantly lower than design. Particle losses are mainly observed in the RFQ. One critical point is the matching section of the RFQ electrodes - Input Radial Matcher (IRM). The original design requires too rigid and narrow beam Twiss-parameters at the RFQ entrance. Also the measured emittance is about twice higher compared to the design. Numerically and experimentally it was proven that the solenoid, used for the beam matching to the RFQ, is not able to provide for the necessary beam size and convergence. As it was shown by beam dynamics simulations using the code DYNAMION, a minor modification of the IRM allows for an improvement of the beam transmission (up to 50%). The proposed measure was realized for an advanced HIT-RFQ-layout, which is recently under test stage. The same modification is already proposed for the linac frontend at Italian Hadrontherapy Center (CNAO, Pavia).
INFN/LNL, Legnaro
GSI, Darmstadt
CNAO, Milan
INFN/LNF, Frascati
INFN/LNS, Catania
The CNAO (Centro Nazionale di Adroterapia Oncologica), located in Pavia (Italy), is a dedicated clinical synchrotron facility for cancer therapy using high energy proton and Carbon beams. The 400 MeV/u synchrotron is injected by a 216.8 MHz 7 MeV/u linac composed by a low energy beam transport (fed by two ion sources), a 400 keV/u 4-rod type RFQ and a 20 MV IHDTL. The commissioning of the two ECRIS ion sources and the low-energy line was successfully completed at the end of January 2009 reaching the proper beam conditions for injection into the RFQ. After installation and conditioning, the RFQ was commissioned with beam by the GSI-CNAO-INFN team in March 2009. The beam tests results are presented and compared to the design parameters.