Superconducting RF Development at Nuclear Science Centre

2001

This paper reports the status of the construction of a superconducting linear accelerator as a booster to the 15UD Pelletron accelerator, at Nuclear Science Centre, New Delhi. The linac will use niobium quarter wave resonators to accelerate ions upto mass ~ 100 above the Coulomb barrier. Prototype resonator and resonators for the first linac module have been fabricated in collaboration with Argonne National Laboratory in USA. Resonators for the remaining two modules will be fabricated indigenously. For this a superconducting resonator fabrication facility is being set up. Details of the linear accelerator, cryogenics system, RF electronics, control system, beam transport system, and resonator fabrication facility are presented.

Proceedings of the 2005 Particle Accelerator Conference, 2005

As part of its efforts for the SNS construction project, Jefferson Lab has produced 23 cryomodules for the superconducting linac. These modules contained 81 industrially produced multicell Nb accelerating cavities. Each of these cavities was individually tested before assembly into a cryomodule to verify that they achieved the required performance. This ensemble of cavities represents the 3rd largest set of production superconducting cavities fabricated and tested to date. The timely qualification testing of such a collection of cavities offers both challenges and opportunities. Their performance can be characterized by achieved gradient at the required Qo, achieved peak surface field, onset of field emission, and observations of multipacting. Possible correlations between cavity performance and process parameters, only really meaningful in the framework of a large scale production effort, will also be presented. In light of the potential adoption of these cavities for projects such as the Rare Isotope Accelerator or Fermilab Proton Driver, such an analysis is crucial to their success.

Physics of Particles and Nuclei Letters, 2018

The project for a new injector linac for the Nuclotron-NICA accelerator tandem has been under development since 2015. The linac will accelerate protons and light ions to energies of 25 MeV and 7.5 MeV/nucleon, respectively. To fulfill the project, technology for fabricating superconducting RF cavities needs to be developed. The current status of the project, including the linac design, the required parameters of RF cavities, and our simulations of beam dynamics, is presented. Technological restrictions on the RF cavity parameters are discussed.

2012

The superconducting driver and post-accelerator linacs of the FRIB project, the large scale radioactive beam facility under construction at MSU, require the construction of about 400 low-β Quarter-wave (QWR) and Half-wave resonators (HWR) with four different optimum velocities. 1st and 2nd generation prototypes of βâ = 0.041 and 0.085 QWRs and βâ = 0.53 HWRs have been built and tested,

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1989

A series of superconducting structures for the acceleration of high-current ion beams is being developed, and two prototype Nb cavities are under construction. These cavities operate in a frequency-velocity range which, for superconducting structures, has been little explored: frequencies of 0.4 GHz to more than 1 GHz, and velocities of 0.1~ to 0.5~. Issues discussed include: need for strong beam loading ( -104), need for strong focusing elements located close to the cavities, minimization of beam impingement and beam instabilities.

Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167), 1998

Two superconducting radiofrequency quadrupoles, SRFQ1 and SRFQ2, resonating at 80 MHz, will provide acceleration from b=v/c=0.009 to 0.035 in PIAVE, the new injector for the superconducting linac ALPI at INFN -Laboratori Nazionali di Legnaro . The construction of the full niobium structures was preceded by the development of a full size stainless steel prototype of SRFQ2 ( , through which most of the construction techniques also applying to the niobium cavities, electromagnetic characterization of the resonator and its mechanical vibration spectrum can be investigated. This paper presents the most relevant design issues of the superconducting RFQ resonators and the construction techniques adopted.

Physical Review Special Topics-accelerators and Beams, 2009

A superconducting linear accelerator based on niobium quarter wave resonators has recently become operational to boost the energy of the heavy ion beams available from the existing 15 UD (unit doubled) Pelletron accelerator. The niobium resonators typically performed at an accelerating field of 3-6 MV=m at 6 watts of input power in the test cryostat. When they were tested in the linac cryostat, the accelerating fields were drastically reduced and a number of other problems were also encountered. At present, all the problems have been diagnosed and solved. Many design modifications, e.g., in power coupler, mechanical tuner, helium cooling system, etc. were incorporated to solve the problems. A novel method of vibration damping was also implemented to reduce the effect of microphonics on the resonators. Finally, the accelerated beam through linac was delivered to conduct experiments.

2010

In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV, an accelerator prototype is presently under design for the first phase of the project. A superconducting option has been chosen for the 5 MeV RF Linac, based on a cryomodule composed of 8 low-beta Half-Wave Resonators (HWR), 8 Solenoid Packages and 8 RF couplers. This paper will focus on the HWR sub-system: the RF, thermo-mechanical design, and the realization of the first prototype of HWR will be presented. The resonator tuning frequency is controlled by an innovant Cold Tuning System (CTS), located in the central region of the cavity. The different options for tuning will be discussed and the final thermo-mechanical design will be detailed. First validation test results of the CTS are expected for the conference.

The medium beta section of the ISAC-II heavy ion superconducting linear accelerator, consisting of 20 cavities, has been in operation at TRIUMF since 2006. The high beta section of the accelerator, consisting of an additional twenty cavities, is currently under development and is scheduled for completion in 2009. The cavity is a superconducting bulk Niobium two-gap quarter-wave resonator for frequency 141 MHz, optimum β ο =0.11, providing, as a design goal, a voltage gain of V a =1.08 MV at 7 W power dissipation. The inner conductor is equipped with a donut drift tube. The cavity has a double wall mechanical structure with liquid Helium inside. Two prototype cavities for the ISAC-II high beta section were developed at TRIUMF and produced by a Canadian company, PAVAC Industries of Richmond, B.C. The prototypes are equipped with a mechanical dissipator to damp detuning environmental mechanical vibrations. An inductive coupler, developed at TRIUMF, provides low power dissipations to the liquid helium system. Superconducting RF tests of both cavity prototypes show that we have achieved the required frequency and exceeded the design goal parameters. Response of the cavity to liquid helium pressure fluctuations, Lorenz force detuning and microphonic sensitivity with and without the damper was tested. RF design, prototype production details and cavity test results will be presented and discussed. . ISAC-II high beta cavity design.

IEEE Transactions on Nuclear Science, 2000