TRIUMF, Vancouver
Heavy Ion superconducting cavities and cryomodules have undergone a renaissance in the last ten years as new heavy ion applications are being discussed to support drivers and post-accelerators primarily for radioactive ion beam facilities. The accelerators are characterized by cw operation and the push has been for high Qo at the operating point to get high performance with a reasonable cryogenic load. New features include particulate control in cavity processing and assembly, cryomodules engineered with separated vacuum for beam and thermal isolation volumes, high performance mechanical tuners and rf couplers and layouts with strong periodic focusing to permit high gradient operation. The present state of the art for high gradient operation is the ISAC-II heavy ion linac but many projects are now in preparation or being developed. A survey of the planned projects and facility upgrades will be presented.
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.
ANL, Argonne
TechSource, Santa Fe
CLASSE, Ithaca
Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
A new cryomodule with seven low-beta superconducting radio frequency (SRF) quarter wave niobium cavities has been designed and constructed as an energy upgrade project for the ATLAS accelerator at Argonne National Laboratory. The technology developed for this project is the basis for the next generation superconducting heavy ion accelerators. This paper will discuss the methods employed to tune the cavities eigenfrequency to match the accelerator master oscillator frequency and the development of the RF systems used to both drive the cavity and keep the cavity phase locked during operation.
TRIUMF, Vancouver
ISAC is the TRIUMF facility for the production and post acceleration of Rare Isotope Beams (RIBs). The post acceleration section includes two normal conducting linacs, an RFQ injector and a variable energy IH-DTL, and a superconducting linac composed of five cryomodules each containing four quarter wave bulk niobium resonators. All three machines operate CW. The RFQ and DTL deliver beam since 2000 to a medium energy area with energies variable between 150 keV/u and 1.8 MeV/u. The superconducting linac, with an effective voltage of 20 MV started delivering in 2007 with performances exceeding design specifications reaching final energies up to 11 MeV/u for lighter particles. The linac gradients show no average degradation in performance. Well established operational and tuning procedures allow reliable operations. Schemes have been developed to effectively deliver the very low intensity (as low as few hundred particles per second) radioactive ion beams. The superconducting linac will be upgraded with the addition of twenty more cavities (boosting the acceleration voltage to 40 MV) by the end of 2009 making the reliability quest more challenging. In this paper we present past, present and planned operations with the ISAC linacs.
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.
IUAC, New Delhi
A 15 UD Pelletron electrostatic accelerator is in regular operation at Inter-University Accelerator Center (IUAC). It has been providing various ion beams in the energy range from a few tens of MeV to 270MeV for scheduled experiments. A superconducting linac booster module having eight niobium quarter wave resonators has been made operational for boosting the energy of the heavy ion beams from the Pelletron for experiments at higher energies. A new type of high temperature superconducting electron cyclotron resonance ion source (HTS-ECRIS) was designed, fabricated and installed. It is in regular operation as a part of an alternate high current injector (HCI) system being developed for injection of highly charged ions having higher beam current in to the superconducting linac. A radio frequency quadrupole (RFQ) accelerator is being developed to accelerate highly charged particles (A/Q ~ 6) to an energy of 180 keV/A. The beam will then be accelerated further by drift tube linacs (DTLs) to the required velocity for injection of the beams to the linac booster. Details of various developmental activities related to the heavy ion accelerators and associated systems are reported.
TIFR, Mumbai
BARC, Mumbai
The superconducting LINAC booster, indigenously developed to boost the energy of the heavy ion beams from the 14 MV Pelletron accelerator at TIFR, Mumbai, has been fully operational since July 2007. The LINAC consists of seven modular cryostats, each housing four lead plated quarter wave resonators, designed for an optimum velocity β0=0.1 at an operating frequency of 150 MHz. In order to maintain a stable phase and amplitude of the electric field in the cavity, the RF controller cards based on a self-excited loop (SEL) with phase and amplitude feedback have been developed indigenously. The cryogenic system for the LINAC has been designed for a typical power dissipation of 6 W in each resonator. Initial beam trials have yielded average energy gain of 0.4 MV/q per cavity corresponding to 80% of the design value. Operational experience of the LINAC, namely, empirically devised procedures for the acceleration of different beams and RF settings, and associated developments are presented.
Tokyo Institute of Technology/RIKEN, Tokyo
Tokyo Institute of Technology, Tokyo
Kyushu University, Fukuoka
JAEA, Ibaraki
BNL, Upton
We are investigating space charge dominated beam dynamics in a Radio Frequency Quadrupole (RFQ) linac. In some accelerator systems, desired ions with different charge state ions are simultaneously injected into an RFQ linac. To describe the evolution of the multi charge beam inside the RFQ, we did particle simulation by using Particle-Mesh (PM) method. Here the high-intensity carbon beam made up of C4+, C5+ and C6+ was applied to the simulation (C5+ was set to the designed ion). The space charge contributions to the transverse emittance growth and to the transverse and longitudinal particle motions are presented.
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.