Theory and Simulations on Space Charge Effects in the Transport of Charged Particle Beams
- Steven Lund, Lawrence Livermore National Laboratory (LLNL) & Lawrence Berkeley National Laboratory (LBNL)
Tuesday, November 19, 4:00 PM - Special Seminar
Biomedical & Physical Sciences Bldg., Rm. 1400
Transport of charged particle beams with high intensity in terms of beam power and/or strong space-charge intensity occur in a plethora of applications ranging from high average power machines like the Facility for Rare Isotope Beams (FRIB) at MSU, spallation neutron sources, and next-generation light sources, to high space-charge intensity machines associated with beam-driven Heavy Ion Fusion (HIF) and High Energy Density Physics (HEDP) and Warm Dense Matter Physics (WDM) studies. Such applications require a high degree of beam control to minimize particle losses and preserve beam quality. This necessitates a detailed understanding of the beam distribution, machine alignment tolerances, applied fields, halo production processes, and parasitic species effects such as electron cloud formation. Strong space-charge effects also occur near injection energy on most machines and are present from the source to the target on machines designed for HIF and HEDP/WDM applications. When space-charge intensity is high, a charged particle beam behaves much as a plasma with the applied focusing forces taking the role of a neutralizing species in a plasma. Collective waves and instabilities associated with this regime have rich physics, can generate excessive halo, degrade beam quality by growing phase-space area, and result in a loss of beam control. In this seminar, first I briefly overview historical and recent activities of the combined Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory group which developed machines for beam-driven HIF and HEDP applications. Extensive numerical simulation tools created in this effort are highlighted. Then I overview physics issues relating to how much space-charge can be transported in realistic periodic focusing channels without degrading the quality of the beam. The solution of a 30 year mystery on the origin of empirically known space-charge transport limits is covered. Physics clarified in this understanding enable design more reliable future machines. Resources developed associated with these studies include extensive simulation tools and graduate-level teaching materials which can be brought to MSU in support of the FRIB/NSCL facility.