Cyclotrons2013 - List of Keywords (bunching)

Paper	Title	Other Keywords	Page
WEPPT014	Analysis of Phase Bunching in the Central Region of the JAEA AVF Cyclotron	acceleration, cyclotron, simulation, ion	350
	N. Miyawaki, H. Kashiwagi, S. Kurashima, S. Okumura JAEA/TARRI, Gunma-ken, Japan M. Fukuda RCNP, Osaka, Japan
	Phase bunching generated in the central region of an AVF cyclotron was estimated by a simplified geometric trajectory analysis model for particles traveling from the first to the second acceleration gap. In principle, a rising slope of a dee-voltage at the first acceleration gap is more or less effective for production of the phase bunching. The phase difference between particles at the second acceleration gap depends on combination of four parameters: the acceleration harmonic number (h), a span angle of the dee electrode, a span angle from the first to the second acceleration gap, a ratio between a peak dee-voltage and an extraction voltage of an ion source. In the case of the JAEA AVF cyclotron, the effective phase bunching was realized for h = 2 and 3, and the geometric condition of phase bunching was unrealistic for h = 1. An orbit simulation for the JAEA AVF cyclotron indicated that the initial beam phase width of 40 RF degrees for h = 2 was compressed to 11 RF degrees. The phase bunching evaluation based on the simplified geometric trajectory analysis was consistent with the orbit simulation result, and practical phase bunching was verified by beam phase width measurement.

WEPPT019	Investigation on the Transverse Emittance Growth of Intense Beam during Bunching	emittance, simulation, space-charge, solenoid	361
	P. Sing Babu, A. Goswami, V.S. Pandit VECC, Kolkata, India
	Bunchers are widely used in the injection system of cyclotrons to transform dc beam into a bunched beam in a desired phase width. In the case of low beam current, the longitudinal compression of beam has very little effect on the transverse dynamics. However in the case of high current bunching the increase of current in the specified bunch width as the beam advances affects the transverse behavior. A 2D particle-in-cell code has been developed to study the transverse dynamics during beam bunching in the injection system of 10MeV, 5mA compact proton cyclotron. We have used a linear increase of beam current in the specified bunch width from the buncher position to the time focus. In the PIC method this effect is introduced by reweighting the charge and mass of the macroparticles during the transport with longitudinal compression. The evolutions of beam envelope and emittance growth have been estimated for various initial particle distributions. It is observed that the rms beam size is independent of particular beam distribution whereas rms emittance grows with nonuniformity of the distribution and peaks near the time focus.

Paper

Title

Other Keywords

Page

WEPPT014

Analysis of Phase Bunching in the Central Region of the JAEA AVF Cyclotron

acceleration, cyclotron, simulation, ion

350

N. Miyawaki, H. Kashiwagi, S. Kurashima, S. Okumura
JAEA/TARRI, Gunma-ken, Japan
M. Fukuda
RCNP, Osaka, Japan

Phase bunching generated in the central region of an AVF cyclotron was estimated by a simplified geometric trajectory analysis model for particles traveling from the first to the second acceleration gap. In principle, a rising slope of a dee-voltage at the first acceleration gap is more or less effective for production of the phase bunching. The phase difference between particles at the second acceleration gap depends on combination of four parameters: the acceleration harmonic number (h), a span angle of the dee electrode, a span angle from the first to the second acceleration gap, a ratio between a peak dee-voltage and an extraction voltage of an ion source. In the case of the JAEA AVF cyclotron, the effective phase bunching was realized for h = 2 and 3, and the geometric condition of phase bunching was unrealistic for h = 1. An orbit simulation for the JAEA AVF cyclotron indicated that the initial beam phase width of 40 RF degrees for h = 2 was compressed to 11 RF degrees. The phase bunching evaluation based on the simplified geometric trajectory analysis was consistent with the orbit simulation result, and practical phase bunching was verified by beam phase width measurement.

WEPPT019

Investigation on the Transverse Emittance Growth of Intense Beam during Bunching

emittance, simulation, space-charge, solenoid

361

P. Sing Babu, A. Goswami, V.S. Pandit
VECC, Kolkata, India

Bunchers are widely used in the injection system of cyclotrons to transform dc beam into a bunched beam in a desired phase width. In the case of low beam current, the longitudinal compression of beam has very little effect on the transverse dynamics. However in the case of high current bunching the increase of current in the specified bunch width as the beam advances affects the transverse behavior. A 2D particle-in-cell code has been developed to study the transverse dynamics during beam bunching in the injection system of 10MeV, 5mA compact proton cyclotron. We have used a linear increase of beam current in the specified bunch width from the buncher position to the time focus. In the PIC method this effect is introduced by reweighting the charge and mass of the macroparticles during the transport with longitudinal compression. The evolutions of beam envelope and emittance growth have been estimated for various initial particle distributions. It is observed that the rms beam size is independent of particular beam distribution whereas rms emittance grows with nonuniformity of the distribution and peaks near the time focus.