IPAC2013 - List of Authors (Meng, C.)

Paper	Title	Page
TUPWO019	A Local Achromatic Design of C-ADS MEBT2	1922
	H. Geng, Z. Guo, Z. Li, C. Meng, S. Pei, J.Y. Tang IHEP, Beijing, People's Republic of China
	The accelerator of China Accelerator Driven Sub-critical system consists of two injectors to ensure its high reliability. The Medium Energy Beam Transport line-2 is an essential part of the accelerator to transport and match the beam from either injector to the main linac. This paper presents a local achromatic design, which uses four bending magnets, for CADS MEBT2. It is found that both transverse and longitudinal emittance growths can be well controlled below 15% from MEBT2 entrance to the exit of the following superconducting spoke-021 section. The beam dynamics of MEBT2 will be discussed and the multi-particle tracking results will also be shown.

TUPWO020	Error Analysis for C-ADS MEBT2	1925
	H. Geng, Z. Guo, Z. Li, C. Meng, S. Pei, J.Y. Tang IHEP, Beijing, People's Republic of China
	A local achromatic scheme has been developed for C-ADS MEBT2. This paper presents the error analysis results for this MEBT2 scheme. The effects of magnet and cavity misalignment, static and dynamic errors of electric and magnetic field, the displacement of the input beam as well as the initial mismatches of the incoming beam will be studied. Beam trajectory correction scheme will also be discussed.

TUPWO023	Parasitic Slow Exraction of Extremely Weak Beam From a High-intensity Proton Rapid Cycling Synchroton	1931
	Y. Zou, H.T. Jing, C. Meng, J.Y. Tang, Z. Yang IHEP, Beijing, People's Republic of China
	This paper proposes a new method to extract extremely weak beam from a high-intensity proton rapid cycling synchrotron in the parasitic mode, while maintaining the normal fast extraction. The usual slow extraction from a synchrotron by third-order resonance method cannot be applied in a RCS due to very short flat-top at the extraction energy. This is even more difficult when it is high-intensity synchrotron due to the strict control on beam loss. The parasitic slow extraction method to extract extremely weak beam from the RCS of CSNS has been studied in details. By moving only beam halo to a scatting foil in the arc region by a local orbit bump in about 2 ms before the fast extraction, one can extract a very small part of the scattered particles with very limited beam loss in the process. At 1.6 GeV and 62.5 A in beam power, halo particles of about 10^-4 total particles are involved in the parasitic slow extraction can result in a beam intensity of 2105 protons per cycle or lower. Detailed studies including scattering effect in the foil, orbit bumps by bump magnets and energy displacement by adjusting RF, and multi-particle simulations by ORBIT and TURTLE codes are presented.

THPWO042	Macroparticle Simulation Studies of a Beam-core Matching Experiment	3860
	H. Jiang, P. Chen, S. Fu, T. Huang, F. Li, P. Li, H.C. Liu, C. Meng, M. Meng, Z.C. Mu, H.F. Ouyang, J. Peng, L.Y. Rong, B. Sun, J.M. Tian, B. Wang, S.C. Wang, W.Q. Xin, T.G. Xu, L. Zeng, F.X. Zhao IHEP, Beijing, People's Republic of China
	We compared the 3-D nonlinear macro- particle code IMPACT simulations with the measured beam-core profiles obtained by the wire-scanners in the beam-core matching experiment. Quadrupole scans were used to determinate the transverse properties of the RFQ output beam. The Gaussian distribution was chosen as the initial particle distribution, which is well fit with the measured beam-core profile. We matched the beam using the least-squares fitting procedure that adjusted the first four matching quadrupoles to produce equal rms beam size in the last six wire scanners. Simulations had been fairly successful in reproducing the core of the measured matched beam profiles.

THPWO043	Progress on the Physics Design of the C-ADS Injector Scheme I	3863
	Z. Li, P. Cheng, H. Geng, C. Meng, H.F. Ouyang, B. Sun, J.Y. Tang, F. Yan, Z. Yang IHEP, Beijing, People's Republic of China
	Funding: Surported by China ADS Project The China ADS (C-ADS) driver linac is composed of two parallel 10 MeV injectors and a main linac which boosts the beam further to 1.5 MeV. There are two design schemes for the injectors based on different working frequency and superconducting cavity structures and are under developing at the same time on IHEP and IMP. The Injector Scheme I, which is proposed by IHEP, works at 325 MHz, the same frequency of the main linac, and superconducting Spoke cavities with geometry beta of 0.12, the same type of cavity as the main linac too, are applied after the RFQ. In this paper, the latest progress on physics design will be presented.

THPWO044	Error Analysis and Beam Loss Control in C-ADS Main Linac	3866
	C. Meng, Z. Li, J.Y. Tang, F. Yan IHEP, Beijing, People's Republic of China
	The China ADS (C-ADS) driver linac is defined to deliver a CW proton beam of 1.5 GeV in energy and 10 mA in current. To meet the extremely high reliability and availability, it is very important and imperative to perform detailed error analysis to simulate the real machine, where the errors always exist. The error studies are by very intense macro-particle simulations by both Trace-Win and TRACK codes with space charge effects included. Through error analysis the proper closed-orbit correction scheme and the maximum tolerable hardware and alignment errors can be found. This paper presents the method to optimize the apertures of elements in the C-ADS main linac. According to the detailed sensitivity analysis of different errors, the static and dynamic errors for the main linac are proposed. The basic lattice scheme has also been re-optimized based on the error studies. The correction scheme is also described, and with the correction scheme the residual orbit can be controlled very well. The influence of the correctors and BPM failures on the correction scheme is also studied.

Paper

Title

Page

A Local Achromatic Design of C-ADS MEBT2

1922

H. Geng, Z. Guo, Z. Li, C. Meng, S. Pei, J.Y. Tang
IHEP, Beijing, People's Republic of China

The accelerator of China Accelerator Driven Sub-critical system consists of two injectors to ensure its high reliability. The Medium Energy Beam Transport line-2 is an essential part of the accelerator to transport and match the beam from either injector to the main linac. This paper presents a local achromatic design, which uses four bending magnets, for CADS MEBT2. It is found that both transverse and longitudinal emittance growths can be well controlled below 15% from MEBT2 entrance to the exit of the following superconducting spoke-021 section. The beam dynamics of MEBT2 will be discussed and the multi-particle tracking results will also be shown.

TUPWO020

Error Analysis for C-ADS MEBT2

1925

H. Geng, Z. Guo, Z. Li, C. Meng, S. Pei, J.Y. Tang
IHEP, Beijing, People's Republic of China

A local achromatic scheme has been developed for C-ADS MEBT2. This paper presents the error analysis results for this MEBT2 scheme. The effects of magnet and cavity misalignment, static and dynamic errors of electric and magnetic field, the displacement of the input beam as well as the initial mismatches of the incoming beam will be studied. Beam trajectory correction scheme will also be discussed.

TUPWO023

Parasitic Slow Exraction of Extremely Weak Beam From a High-intensity Proton Rapid Cycling Synchroton

1931

Y. Zou, H.T. Jing, C. Meng, J.Y. Tang, Z. Yang
IHEP, Beijing, People's Republic of China

This paper proposes a new method to extract extremely weak beam from a high-intensity proton rapid cycling synchrotron in the parasitic mode, while maintaining the normal fast extraction. The usual slow extraction from a synchrotron by third-order resonance method cannot be applied in a RCS due to very short flat-top at the extraction energy. This is even more difficult when it is high-intensity synchrotron due to the strict control on beam loss. The parasitic slow extraction method to extract extremely weak beam from the RCS of CSNS has been studied in details. By moving only beam halo to a scatting foil in the arc region by a local orbit bump in about 2 ms before the fast extraction, one can extract a very small part of the scattered particles with very limited beam loss in the process. At 1.6 GeV and 62.5 A in beam power, halo particles of about 10^-4 total particles are involved in the parasitic slow extraction can result in a beam intensity of 2105 protons per cycle or lower. Detailed studies including scattering effect in the foil, orbit bumps by bump magnets and energy displacement by adjusting RF, and multi-particle simulations by ORBIT and TURTLE codes are presented.

THPWO042

Macroparticle Simulation Studies of a Beam-core Matching Experiment

3860

H. Jiang, P. Chen, S. Fu, T. Huang, F. Li, P. Li, H.C. Liu, C. Meng, M. Meng, Z.C. Mu, H.F. Ouyang, J. Peng, L.Y. Rong, B. Sun, J.M. Tian, B. Wang, S.C. Wang, W.Q. Xin, T.G. Xu, L. Zeng, F.X. Zhao
IHEP, Beijing, People's Republic of China

We compared the 3-D nonlinear macro- particle code IMPACT simulations with the measured beam-core profiles obtained by the wire-scanners in the beam-core matching experiment. Quadrupole scans were used to determinate the transverse properties of the RFQ output beam. The Gaussian distribution was chosen as the initial particle distribution, which is well fit with the measured beam-core profile. We matched the beam using the least-squares fitting procedure that adjusted the first four matching quadrupoles to produce equal rms beam size in the last six wire scanners. Simulations had been fairly successful in reproducing the core of the measured matched beam profiles.

THPWO043

Progress on the Physics Design of the C-ADS Injector Scheme I

3863

Z. Li, P. Cheng, H. Geng, C. Meng, H.F. Ouyang, B. Sun, J.Y. Tang, F. Yan, Z. Yang
IHEP, Beijing, People's Republic of China

Funding: Surported by China ADS Project
The China ADS (C-ADS) driver linac is composed of two parallel 10 MeV injectors and a main linac which boosts the beam further to 1.5 MeV. There are two design schemes for the injectors based on different working frequency and superconducting cavity structures and are under developing at the same time on IHEP and IMP. The Injector Scheme I, which is proposed by IHEP, works at 325 MHz, the same frequency of the main linac, and superconducting Spoke cavities with geometry beta of 0.12, the same type of cavity as the main linac too, are applied after the RFQ. In this paper, the latest progress on physics design will be presented.

THPWO044

Error Analysis and Beam Loss Control in C-ADS Main Linac

3866

C. Meng, Z. Li, J.Y. Tang, F. Yan
IHEP, Beijing, People's Republic of China

The China ADS (C-ADS) driver linac is defined to deliver a CW proton beam of 1.5 GeV in energy and 10 mA in current. To meet the extremely high reliability and availability, it is very important and imperative to perform detailed error analysis to simulate the real machine, where the errors always exist. The error studies are by very intense macro-particle simulations by both Trace-Win and TRACK codes with space charge effects included. Through error analysis the proper closed-orbit correction scheme and the maximum tolerable hardware and alignment errors can be found. This paper presents the method to optimize the apertures of elements in the C-ADS main linac. According to the detailed sensitivity analysis of different errors, the static and dynamic errors for the main linac are proposed. The basic lattice scheme has also been re-optimized based on the error studies. The correction scheme is also described, and with the correction scheme the residual orbit can be controlled very well. The influence of the correctors and BPM failures on the correction scheme is also studied.