PAC2013 - List of Authors (Shin, K.R.)

Paper	Title	Page
WEPMA22	Investigation on Double Dipole Four-Vane RFQ Structure	1028
	K.R. Shin ORNL RAD, Oak Ridge, Tennessee, USA M.S. Champion, Y.W. Kang ORNL, Oak Ridge, Tennessee, USA A.E. Fathy University of Tennessee, Knoxville, Tennessee, USA
	Four-vane RFQ is a general choice for the low energy injector of light ion accelerators. In this commonly used four-vane RFQ structure, each vane has undercuts at both ends to create open magnetic field path that realizes uniform electromagnetic fields along longitudinal direction. Meanwhile, there exists another undercut method called as double dipole (DD) that requires undercuts only on 2 vanes interleaved with vanes with no undercut. The RFQ with DD cutback can provide a design option besides the traditional 4 vane cutback (4C) method. In this paper, we investigate and discuss some important DD RFQ features in detail: 1) Finite on-axis field at DD RFQ end section which is similar to split coaxial structure, 2) Open and short circuit ends dipoles, those lead to the unique mode spectrum and enhanced cavity coupling, and 3) Perturbation and tuning sensitivity. 3D simulation is utilized for DD RFQ analysis.

WEPMA23	Design and Measurement of Double Gap Buncher Cavity Proposed for Reduction of X- ray Radiation	1031
	K.R. Shin ORNL RAD, Oak Ridge, Tennessee, USA M.S. Champion, Y.W. Kang ORNL, Oak Ridge, Tennessee, USA A.E. Fathy University of Tennessee, Knoxville, Tennessee, USA
	X-ray radiation from accelerating cavities can be serious problem not only in high energy section but also in low energy part including beam matching section with buncher cavity. Two approaches can be considered to be useful for the radiation reduction. First, lower gap voltage may decrease a radiation dose and hard X-ray generation. Second, lower electric peak field with smooth gap geometry may help to minimize field emission current. Regarding these considerations, in this paper we propose a double gap buncher cavity for low energy part of H⁻ ion accelerators such as medium energy beam transport (MEBT) section in Spallation Neutron Source. For MEBT application, the cavity may use Transverse Magnetic (TM) mode at about 400MHz as the operating mode. A drift tube supported by a stem in the cavity can form two gaps that can divide the required gap voltage to a half per each gap. Lower peak field can be realized since this double gap cavity can enhance the particle transit time factor. 3D simulation is utilized to address the analysis of non-axisymmetric structure. An Aluminum scaled model is built and tested at low power. The measured results are in good agreement with simulations.

Paper

Title

Page

Investigation on Double Dipole Four-Vane RFQ Structure

1028

K.R. Shin
ORNL RAD, Oak Ridge, Tennessee, USA
M.S. Champion, Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA
A.E. Fathy
University of Tennessee, Knoxville, Tennessee, USA

Four-vane RFQ is a general choice for the low energy injector of light ion accelerators. In this commonly used four-vane RFQ structure, each vane has undercuts at both ends to create open magnetic field path that realizes uniform electromagnetic fields along longitudinal direction. Meanwhile, there exists another undercut method called as double dipole (DD) that requires undercuts only on 2 vanes interleaved with vanes with no undercut. The RFQ with DD cutback can provide a design option besides the traditional 4 vane cutback (4C) method. In this paper, we investigate and discuss some important DD RFQ features in detail: 1) Finite on-axis field at DD RFQ end section which is similar to split coaxial structure, 2) Open and short circuit ends dipoles, those lead to the unique mode spectrum and enhanced cavity coupling, and 3) Perturbation and tuning sensitivity. 3D simulation is utilized for DD RFQ analysis.

WEPMA23

Design and Measurement of Double Gap Buncher Cavity Proposed for Reduction of X- ray Radiation

1031

K.R. Shin
ORNL RAD, Oak Ridge, Tennessee, USA
M.S. Champion, Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA
A.E. Fathy
University of Tennessee, Knoxville, Tennessee, USA

X-ray radiation from accelerating cavities can be serious problem not only in high energy section but also in low energy part including beam matching section with buncher cavity. Two approaches can be considered to be useful for the radiation reduction. First, lower gap voltage may decrease a radiation dose and hard X-ray generation. Second, lower electric peak field with smooth gap geometry may help to minimize field emission current. Regarding these considerations, in this paper we propose a double gap buncher cavity for low energy part of H⁻ ion accelerators such as medium energy beam transport (MEBT) section in Spallation Neutron Source. For MEBT application, the cavity may use Transverse Magnetic (TM) mode at about 400MHz as the operating mode. A drift tube supported by a stem in the cavity can form two gaps that can divide the required gap voltage to a half per each gap. Lower peak field can be realized since this double gap cavity can enhance the particle transit time factor. 3D simulation is utilized to address the analysis of non-axisymmetric structure. An Aluminum scaled model is built and tested at low power. The measured results are in good agreement with simulations.