| Paper | Title | Page |
|---|---|---|
| FR5RFP079 | Recent Observations, Experiments and Simulations of Electron Cloud Buildup in Drift Spaces and Quadrupole Magnets at the Los Alamos PSR | 4722 |
|
||
|
Funding: Work supported, in part, by DOE SBIR Grant No. DE-FG02-04ER84105 and CRADA No. LA05C10535 between TechSource, Inc. and the Los Alamos National Laboratory. Recent beam studies have focused on understanding the main sources and locations of electron clouds (EC) which drive the observed e-p instability at the Los Alamos Proton Storage Ring (PSR). Strong EC signals are observed in drift spaces and quadrupole magnets at PSR which together cover ~65% of the ring circumference. New results making use of two longitudinal barriers to isolate the drift space electron diagnostic provide definitive evidence that most of the drift space EC signal is “seeded” by electrons ejected longitudinally by ExB drifts from adjacent quadrupole magnets. This result can explain why weak solenoids and TiN coatings in several drifts spaces had no effect on the e-p instability threshold. Modeling of EC generation in 3D quadrupoles using a modified version of the POSINST code shows that a sizeable fraction of the electrons generated in the quadrupoles are ejected longitudinally into the adjacent drifts. The experimental findings and simulation results will be presented. |
||
| FR5REP070 | Development of IH Accelerating Structures with PMQ Focusing for Low-Beta Ion Beams | 4938 |
|
||
|
We are developing high-efficiency room-temperature RF accelerating structures based on inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. Such IH-PMQ accelerating structures following a short RFQ can be used in the front end of ion linacs or in stand-alone applications such as a compact deuteron-beam accelerator up to the energy of several MeV. New results from our detailed electromagnetic 3-D modeling combined with beam dynamics simulations and thermal-stress analysis for a complete IH-PMQ accelerator tank, including the end-cell design, will be presented. |
||
| FR5REP072 | Use of a Debuncher Cavity for Improving Multi-Beam Operations at LANSCE | 4944 |
|
||
|
Funding: This work is supported by the U. S. Department of Energy, Contract DE-AC52-06NA25396. The Los Alamos Neutron Science Center simultaneously provides both H- and H+ beams to several user facilities. Opposite polarity beams are usually accelerated in the linac during the same macropulse when beam-loading limitations are not exceeded. Presently, the Weapons Neutron Research (WNR) H- and Isotope Production Facility (IPF) H+ beams are accelerated simultaneously during the same macropulse. The amplitude of the cavity field in the last 201-MHz buncher, located in the common transport just upstream of the DTL, is a compromise between the optimal values for each beam. Recent beam dynamics studies have shown that implementing a debuncher cavity in the H- low-energy beam transport would allow for more optimal operation of both beams. For this application where space is limited, a compact 201-MHz quarter-wave cavity will be used. This paper will report on the beam dynamics simulations performed and the quarter-wave cavity design being developed to address this issue. |