Fermilab, Batavia, Illinois, USA
Analysis of the beam position monitor (BPM) signals at the H⁻ test linear accelerator PIP2IT showed that a large portion of the signals scatter comes from the beam jitter. BPM position measurements of the jitter modes were compared with beam motion responses to perturbations excited by driving various beamline parameters in a low frequency sinusoidal manner. The main contributor to the jitter was found to be a low frequency noise in the input reference to the ion source high voltage (HV) power supply. Filtering the HV power supply reference signal decreased the rms scatter in BPM readings by a factor of 2-3.
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ORNL RAD, Oak Ridge, Tennessee, USA
The Spallation Neutron Source (SNS) uses 300-400μ g/cm2 nanocrystalline diamond foils grown in-house at the Center for Nanophase Materials Sciences to facilitate charge exchange injection (CEI) from the 1 GeV H⁻ linac into the 248~m circumference accumulation ring. These foils have performed exceptionally well with lifetimes of thousands of MW·hrs. This contribution shares some experience with the operation of these foils during 1.4 MW operation, and discusses current operational concerns including injection related losses, foil conditioning, deformation, and sublimation due to high temperatures. The implications for the SNS Proton Power Upgrade are also discussed.
FRIB, East Lansing, Michigan, USA
The Facility for Rare Isotope Beams (FRIB), a major nuclear physics facility for research with fast, stopped, and reaccelerated rare isotope beams, is approaching the commencement of user operation in 2022 as planned. The readiness of the linear accelerator for the production of rare isotopes was verified by the acceleration of Xenon-124 and Krypton-86 heavy ion beams to 212 MeV/u using all 46 cryomodules with 324 superconducting cavities. Several key technologies were successfully developed and implemented for the world¿s highest energy continuous wave heavy ion beams, such as full-scale cryogenics and superconducting radiofrequency resonator system, stripping heavy ions with a thin liquid lithium film flowing in an ultrahigh vacuum environment, and simultaneous acceleration of multiple-charge-state-heavy ion beams. These technologies are required to achieve ultimate FRIB beam energies beyond 200 MeV/u and beam power up to 400 kW. High intensity pulsed beams capable in delivering 200 kW beams to the target in CW mode were studied in the first segment of the linac.