Divergence in intense ion beams caused by incomplete charge neutralization

Conference · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7113166

Olson, C L; Poukey, J W

Space charge neutralization for light ion fusion (LIF) ion beam transport is usually assumed to be perfect in the charge-neutral'' region of the diode and in the gas transport cell. However, small charge clumps in the beam will not be totally charge-neutralized, and the residual net space charge may contribute to the beam microdivergence {theta} {sub {mu}}. If the net potential of the clump is limited only by electron trapping, the minimum potential will be e{phi} {approximately} 1/2 m{sub e}v{sub i}{sup 2} where m{sub e} is the electron mass and v{sub i} is the ion velocity. For proton beams this leads to {theta}{sub {mu}} {approximately} (m {sub e}/M{sub p}){sup 1/2} {approximately} 23 mrad, where M{sub p} is the proton rest mass. For non-protonic beams, different results occur. The mechanism predicts no dependence of {theta} {sub {mu}} on diode voltage, non-protonic {theta} {sub {mu}} greater than proton {theta} {sub {mu}} for proton-contaminated beams, and axial energy spread {Delta}{var epsilon}{sub {parallel}}/{var epsilon}{sub {parallel}} {approximately} {plus minus} 2 {theta} {sub {mu}}, which are all consistent with present data. Results of analytic studies and computer simulations of this mechanism are presented. Plasma shielding reduces the effects of this mechanism but collisions and magnetic fields reduce the plasma shielding effects. 2-D PIC MAGIC simulations show that this mechanism contributes to {theta} {sub {mu}} both in the charge-neutral'' region and in the gas transport region. It is concluded that this mechanism is especially important in the charge-neutral'' region.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 7113166
• Report Number(s): SAND-91-2744C; CONF-920515--27; ON: DE92016891
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
430200 -- Particle Accelerators-- Beam Dynamics
Field Calculations
& Ion Optics
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700411* -- Inertial Confinement Devices-- (1992-)
BEAM NEUTRALIZATION
BEAM TRANSPORT
BEAMS
CONFINEMENT
DIFFUSION
FOCUSING
INERTIAL CONFINEMENT
ION BEAM FUSION REACTORS
ION BEAMS
ION SOURCES
PLASMA CONFINEMENT
PLASMA SIMULATION
SHIELDING
SIMULATION
SPACE CHARGE
THERMONUCLEAR REACTORS