FRIB, East Lansing, USA
INFN/LNL, Legnaro (PD), Italy
TRIUMF, Vancouver, Canada
JLab, Newport News, Virginia, USA
The Facility for Rare Isotope Beams (FRIB) driver linac is to accelerate all the stable ion beams from proton to uranium beyond 200 MeV/u with beam powers up to 400 kW, which will be the first large-scale, CW SRF ion linac. The beam commissioning of the front end (from the ion source to the RFQ) already began and is in progress. The Accelerator Readiness Review (ARR) for beam through the first three β=0.041 cryomodules is scheduled for May 2018. The next step is the beam commissioning through the 12 SRF cavities housed in these 3 cryomodules with 6 superconducting solenoid magnets. The cryomodules and the adjacent warm diagnostics boxes in between have been already installed and aligned in the tunnel. This paper describes the installation progress of the β=0.041 cryomodules and plans for ARR02.
FRIB, East Lansing, USA
The commissioning of the FRIB Front End with 12 keV/u argon beam started in the spring of 2017*. Beam profile monitors were used to evaluate RMS Twiss parameters in various locations along the beam line. Beam dynamics in the LEBT was simulated using full 3D model of beam optics elements in the tracking codes. We found a good consistency between measured and simulated data. A beam image viewer was used to measure the beam density distribution in the real space. A hollow beam structure was observed in the Ar9+ beam with the current of ~20 eμA. Extensive beam dynamics study with 3D tracking code suggests that the hollow density distribution can be generated by space charge effects of the multi-component, multi-charge state ion beam just after the ECR ion source. This paper reports studies of a mechanism that can produce a hollow beam structure.
*E. Pozdeyev, invited talk at this conference
NSCL, East Lansing, Michigan, USA
FRIB, East Lansing, USA
Benchtop calibration of capacitive beam position monitors (BPMs) in low energy beamlines is challenging due to non-relativistic effects. Typical benchtop calibrations cannot account for these effects because they rely on speed of light fields transmitted along a straight wire. However, it is possible to replicate the electromagnetic fields generated by non-relativistic beams using a helical line pulse instead of a straight wire. In order to properly replicate the fields from a beam, a method must be developed for tailoring input pulses into the helical line to match bunch shape and a model of the impedance of the helix should be developed to assist with matching. This paper uses the sheath helix model to analyze signal propagation along a helical line in the time domain, with attention to dispersive effects and impedance matching. The results from this model are then compared to Microwave Studio simulations.
FRIB, East Lansing, USA
NSCL, East Lansing, Michigan, USA
This paper presents recent developments of accelerator physics related topics for the Facility for Rare Isotope Beams (FRIB) being built at Michigan State University. While extensive beam dynamics simulations including all known errors do not show uncontrolled beam losses in the linac, ion beam contaminants extracted from the ECR ion source 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 ECR to MEBT has been developed and applied to meet important project milestones. Similar work is planned for the beam commissioning of the first 3 cryomodules in the superconducting linac.
