HIF 2010
18th International Symposium
on Heavy Ion Inertial Fusion -
Information

Title:	Dr.
Family Name:	Qin
First Name:	Hong
E-Mail:	hongqinprinceton.edu
Affiliation for Badge:	Princeton University
Institute:
Address (Street):	Princeton Plasma Physics Lab
Postal Code, City:	Princeton, NJ, 08540
Country:	United States
Phone:	609 243 3310
Fax:	609 243 2661
Payment:	Cash at the conference site
Author(s):	Hong Qin and Ronald C. Davidson Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 USA B. Grant Logan Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA
Institute(s):
Title:	Centroid and envelope dynamics of high-intensity charged particle beams in an external focusing lattice and oscillating wobbler* * Research supported by the U.S. Department of Energy.
Abstract:	Recent heavy ion fusion target studies show that with appropriate beam energy ramp and beam smoothing techniques, it may be possible to achieve ignition with direct drive and energy gain larger than 100 at 1MJ. With the newly envisioned shock ignition method, an energy gain of 1000 could be achieved using 1.5MJ heavy ion direct drive. To realize these advanced heavy ion fusion schemes based on direct drive, it is important to develop a reliable beam smoothing technique to mitigate instabilities. The centroid and envelope dynamics of a high-intensity charged particle beam are investigated as a beam smoothing technique to achieve uniform illumination over a suitably chosen region of the target. The motion of the beam centroid projected onto the target follows a smooth pattern to achieve the desired illumination, for improved stability properties during the beam-target interaction. The centroid dynamics is controlled by an oscillating "wobbler", a set of electrically-biased plates driven by RF voltage. Using a model based on moments of the Vlasov-Maxwell equations, we show that the wobbler deflection force acts only on the centroid motion, and that the envelope dynamics are independent of the wobbler fields. If the conducting wall is far away from the beam, then the envelope dynamics and centroid dynamics are completely decoupled. This is an ideal situation for the beam wobbling technique, because the wobbler system can be designed to generate the desired centroid motion on the target without considering the potentially deleterious effects on the envelope and emittance.
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