Comparison between experimental and theoretical results for the fast-head-tail instability in PEP

Conference · Fri Jul 01 04:00:00 EDT 1983

OSTI ID:5665291

The fast-head-tail instability has been observed at several storage rings. This is a single-bunch beam instability where the unstable motion can occur in either the horizontal or vertical plane. Kohaupt and Talman have offered a simplified treatment of this instability by modeling the bunch as two rigid macroparticles executing synchrotron oscillations and thus exchanging their longitudinal positions periodically. While the wake field forces which drive the fast-head-tail instability are the same ones which drive the slow-head-tail instability, the growth mechanism is considerably different. The two particle model describes the particle motion with two normal modes; below a certain stability threshold, these two modes are stable with different frequencies. In the limit of zero beam current only one of these modes has a center-of-charge motion. However, as the current is increased, both modes acquire center-of-charge motions and at threshold the center-of-charge components of their motions become equal in magnitude, thus when the center-of-charge motion is excited by an impulse as by an injection kicker, the relative amplitude of the two modes depends upon the ratio of bunch current to the threshold current. We shall describe the character of this coherent motion both theoretically and experimentally.

• Research Organization: Stanford Linear Accelerator Center, CA (USA)
• DOE Contract Number: AC03-76SF00515
• OSTI ID: 5665291
• Report Number(s): SLAC-PUB-3175; CONF-830822-29; ON: DE84000990
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
430200* -- Particle Accelerators-- Beam Dynamics
Field Calculations
& Ion Optics
430400 -- Particle Accelerators-- Storage Rings
BEAM DYNAMICS
DIFFERENTIAL EQUATIONS
EQUATIONS
EQUATIONS OF MOTION
INSTABILITY
OSCILLATIONS
PARTIAL DIFFERENTIAL EQUATIONS
PEP STORAGE RINGS
STORAGE RINGS
SYNCHROTRON OSCILLATIONS