Design Integration of the Frib Driver Linac

2016

The FRIB driver linac accelerates all the stable ion beams including uranium over 200 MeV/u with a CW beam power of 400 kW in order to produce isotopes as rare as possible. Except for 0.5 MeV/u RFQ, the linac is making use of superconducting (SC) RF technology. The beam power, which is an order of 2.5 as high as those of existing SC heavy ion linac, gives rise to many technical challenges as well as beam physics related ones. In particular, the uranium beam loss power density is approximately 30 times as high as the proton one with the same beam energy per nucleon and the same beam power. For this reason, the machine protection system needs a special care. Another example of the technical challenges is to install beam focusing solenoid as close as possible to SC cavities in order to keep the beam focusing as frequent as possible both longitudinally and transversely. This paper reviews all these challenges with development results of their mitigation as well as construction status.

The Facility for Rare Isotope Beams (FRIB) is a high-power heavy ion accelerator facility presently under construction at Michigan State University to support nuclear physics. FRIB consists of a driver linac and experimental facility, and the linac accelerates all stable ions including uranium to kinetic energies of more than 200 MeV/u and continuous wave beam power up to 400 kW. This beam power is more than two orders of magnitude higher than the existing heavy ion linac facilities, resulting in various beam dynamics challenges for the driver linac. In this paper, we review these challenges for the FRIB driver linac and undergoing studies to address them.

2019

The Facility for Rare Isotope Beams (FRIB) superconducting (SC) driver linac is designed to accelerate all stable ions including uranium to energies above 200 MeV/u primarily with 46 cryomodules containing 324 quarter-wave resonators (QWR) and half-wave (HWR) resonators. With the newly commissioned helium refrigeration system supplying liquid helium to the QWR and solenoids, heavy ion beams including Ne, Ar, Kr and Xe were accelerated to the charge stripper location above 20 MeV/u with the first linac segment consisting of 15 cryomodules containing 10⁴ QWRs of β=0.041 and 0.085 and 39 solenoids. Installation of cryomodules with β=0.29 and 0.53 HWRs is proceeding in parallel. Development of β=0.65 elliptical resonators is on-going supporting the FRIB energy upgrade to 400 MeV/u. This paper summarizes the SC-linac installation and phased commissioning status that is on schedule and on budget to the FRIB project.

2015

This paper surveys the key technologies and design challenges that form a basis for the next generation of high intensity hadron accelerators, including projects operating, under construction, and under design for science and applications at MW beam power level. Emphasis is made on high intensity linacs like the Facility for Rare Isotope Beams (FRIB).

The Facility for Rare Isotope Beams (FRIB), a Department of Energy (DOE) national user facility to provide intense beams of rare isotopes for nuclear science researchers, is currently being established on the campus of Michigan State University (MSU). A superconducting driver linac will deliver cw beams of stable isotopes with an energy of >200 MeV/u at a beam power of 400 kW. Highly charged ions will be produced from an Electron Cyclotron Resonance Ion Source (ECRIS) with a total extraction current of several mA. Multiple charge states of heavier ions will be accelerated simultaneously to meet the final beam power requirement. The FRIB driver linac lattice design has been developed and end-to-end beam simulations have been performed to evaluate the machine performance. An overview of the beam dynamics is presented.

1999

An ion linac formed of superconducting rf cavities can provide a multi-beam driver accelerator for the production of nuclei far from stability. A multi-beam driver supports a wide variety of production reactions and methods. This paper outlines a concept for a 1.3 GV linac capable of delivering several hundred kilowatts of uranium beam at an energy of 400 MeV per nucleon. The linac would accelerate the full mass range of ions, and provide higher velocities for the lighter ions, for example 730 MeV for protons. The accelerator will consist of an ECR ion source injecting a normally conducting RFQ and four short IH structures, then feeding an array of more than 400 superconducting cavities of six different types, which range in frequency from 58 to 700 MHz. A novel feature of the linac is the acceleration of beams containing more than one charge state through portions of the linac, in order to maximize beam current for the heavier ions. Such operation is made feasible by the large transverse and longitudinal acceptance provided by the large aperture and high gradient which are characteristic of superconducting rf cavities.

2018

This paper presents recent developments of accelerator physics related topics for the Facility for Rare Isotope Beams (FRIB) being built at Michigan State University [1]. While extensive beam dynamics simulations including all known errors do not show uncontrolled beam losses in the linac, ion beam contaminants extracted from the Electron Cyclotron Resonance (ECR) ion source (ECRIS) together with main ion beam can produce significant losses after the charge stripper. These studies resulted in development of beam collimation system at relatively low energy of 16 MeV/u and room temperature bunchers instead of originally planned superconducting ones. Commissioning of the Front End enabled detailed beam physics studies accompanied with the simulations using several beam dynamics codes. Settings of beam optics devices from the ECRIS to Medium Energy Beam Transport (MEBT) have been developed and applied to meet important project milestones. Similar work is planned for the beam commissioni...

2015

The FRIB driver linac is a front runner for the future high power hadron linacs, making full use of CW, superconducting acceleration from very low β. accelerator driven nuclear waste transmutation system (ADS), international fusion material irradiation facility (IFMIF), Project-X type proton accelerators for high energy physics and others may utilize the technologies developed for the design, construction, commissioning and power ramp up of the FRIB linac. Although each technology has been already well developed individually (except for charge stripper), their integration is another challenge. In addition, extremely high Bragg peak of uranium beams (several thousand times as high as that of proton beams) gives rise to one of the biggest challenges in many aspects. This report summarizes these challenges and mitigations, emphasizing the commonly overlooked features.

There is considerable interest worldwide in the research which could be done at a next generation, advanced radioactive beam facility. To generate high quality, intense beams of accelerated radionuclides via the "isotope separator on-line" (ISOL) method requires two major accelerator components: a high power (100 kW) driver device to produce radionuclides in a production target/ion source complex, and a secondary beam accelerator to produce beams of radioactive ions up to energies on the order of 10 MeV per nucleon over a broad mass range. In reviewing the technological challenges of such a facility, several types of modern linear accelerators appear well suited. This paper reviews the properties of the linacs currently under construction and those proposed for future facilities for use either as the driver device or the radioactive beam postaccelerator. Other choices of accelerators, such as cyclotrons, for either the driver or secondary beam devices of a radioactive beam complex will also be compared. Issues to be addressed for the production accelerator include the choice of ion beam types to be used for cost-effective production of radionuclides. For the post-accelerator the choice of ion source technology is critical and dictates the charge-to-mass requirements at the injection stage.

2019

The driver linac for Facility for Rare Isotope Beams (FRIB) will accelerate all stable ion beams from proton to uranium beyond 200 MeV/u with beam powers up to 400 kW. The linac now consists of 10⁴ superconducting quarter-wave resonators (QWR), which is the world largest number of low-beta SRF cavities operating at an accelerator facility. The first 3 QWR cryomodules (CM) (β = 0.041) were successfully integrated with cryogenics and other support systems for the 2nd Accelerator Readiness Review (ARR). The 3rd ARR scope that includes 11 QWR CM (β=0.085) and 1 QWR matching CM (β=0.085) was commissioned on schedule by January 2019, and then we met the Key Performance Parameters (KPP), accelerating Ar and Kr > 16 MeV/u at this stage, in a week upon the ARR authorization. We examine a variety of key factors to the successful commissioning, such as component testing prior to system integration, assessment steps of system/device readiness, and phased commissioning. This paper also report...