TRIUMF, Vancouver
PAVAC, Richmond, B.C.
The ISAC-II heavy ion linear accelerator has been in operation at TRIUMF since 2006. The high beta section of the accelerator, consisting of twenty cavities with optimum beta=0.11, is currently under production and is scheduled for completion in 2009. The cavities are superconducting bulk Niobium two-gap quarter-wave resonators with a frequency of 141 MHz, providing, as a design goal, a voltage gain of Veff=1.08 MV at 7 W power dissipation. Production of the cavities is with a Canadian company, PAVAC Industries of Richmond, B.C. after two prototype cavities were developed, produced and successfully tested. Cavity production details and test results will be presented and discussed.
TRIUMF, Vancouver
DAE/VECC, Calcutta
A 0.5 megawatt electron linear accelerator is being designed at TRIUMF in support of its expanding rare isotope program, which targets nuclear structure and astrophysics studies as well as material science. The first stage of the project, a 25 MeV, 5 mA, cw linac matching the isotope production target power-handling capability in the next five-year plan, is planned to be completed in 2013. The injector cryomodule development, which is being fast tracked, is the subject of a scientific collaboration between TRIUMF and the VECC laboratory in Kolkata, India. The paper gives an overview of the accelerator design progress.
TRIUMF, Vancouver
In the TRIUMF cyclotron when a spark occurs it is necessary to shut off the RF drive and to initiate a RF restart procedure. It is also desirable to restore the full operational dee voltage as soon as possible in order to prevent thermal detuning of the resonant cavity. However, when the RF drive is shut off, the disappearance of Lorentz force on the resonator hot-arms causes the hot-arms to vibrate at their mechanical resonant frequency. When the RF field is being restored, the electromagnetic resonance is coupled to the mechanical resonance through the Lorentz force, and the amplitudes of both the mechanical vibration and the RF field depend on the timing when RF drive is re-applied. Computer simulations and experimental results will be presented to demonstrate that an optimum exists as to when to initiate the RF restart. With this optimal timing, the Lorentz force is used to damp the mechanical vibrations of the hot-arms. The reduction in hot-arm vibrations increases the probability of successful restarts as well as reduces the stress on the RF components.
TRIUMF, Vancouver
An energy upgrade in the Radioactive Ion Beam (RIB) facility at ISAC-II will see the installation of 20MV of superconducting heavy ion linac. The addition includes twenty beta=11% bulk niobium quarter wave cavities housed in three cryomodules with six cavities in the first two and eight cavities in the last. Each cavity is specified to add 1MV in accelerating potential corresponding to peak surface fields of ~30MV/m. Transverse focusing is achieved with a 9T superconducting solenoid inside each cryomodule. The first module in the expansion has now been assembled and tested. Developments include a new ball screw tuner, locally produced cavities, modified coupler design and LN2 cryogenic circuits. The new developments are described and the results of the first cold tests are presented.
University of Pennsylvania, Philadelphia, Pennsylvania
TRIUMF, Vancouver
The quality factor of superconducting radio-frequency cavities typically degrades with increasing field at moderate gradients before the on-set of field emission. The origin of the so called medium field Q-slope is not fully described and understanding it would be important in order to develop a cavity design or treatment which minimizes this effect, allowing us to produce cavities with reduced cryogenic losses. This paper will present an analysis of the medium field Q-slope data measured on cavities at different frequencies treated with buffered chemical polishing (BCP) at TRIUMF. The data is compared with existing models and agreements-discrepancies will be highlighted.
TRIUMF, Vancouver
The rf control system for the 1.3 GHz TRIUMF e-linac elliptical superconducting cavities is a hybrid analogue/digital design. It is based in part on an earlier design developed for the 1/4 wave superconducting cavities of the ISACII linac. This design has undergone several iterations in the course of its development. In the current design, down-conversion to an intermediate frequency of 138MHz is employed. The cavity operates in a self-excited feedback loop, while phase locked loops are used to achieve frequency and phase stability. Digital signal processors are used to provide amplitude and phase regulation, as well as mechanical cavity tuning control. This version also allows for the rapid implementation of operating firmware and software changes, which can be done remotely, if the need arises. This paper describes the RF control system and the experience gained in operating this system with a single-cavity test facility.