IPAC2011 - List of Authors (Qin, Q.)

Paper	Title	Page
MOPS059	Transverse Impedance Calculation for Simplified Model of Ferrite Kicker Magnet with Beta < 1	742
	N. Wang, Q. Qin IHEP Beijing, Beijing, People's Republic of China
	In high intensity rings, kicker magnet is usually considered as a main source to the total impedance. Transverse coupling impedance of a simplified kicker model has been derived analytically in the ultrarelativistic limit. We extend the result to the general case of v < c, and present the analytical formulae of both horizontal and vertical transverse impedances. Numerical results are given for the CSNS extraction kicker magnets.

MOPS073	Impedance Calculation for Simple Models of Kickers in the Non-ultrarelativistic Regime	772
	N. Biancacci, N. Mounet, E. Métral, B. Salvant, C. Zannini CERN, Geneva, Switzerland N. Biancacci, M. Migliorati, A. Mostacci, L. Palumbo Rome University La Sapienza, Roma, Italy Q. Qin, N. Wang IHEP Beijing, Beijing, People's Republic of China
	Kicker magnets are usually significant contributors to the beam coupling impedance of particle accelerators. An accurate understanding of their impedance is required in order to correctly assess the machine intensity limitations. The field matching method derived by H. Tsutsui for the longitudinal and transverse dipolar (driving) impedance of simple models of kickers in the ultrarelativistic regime was already extended to the non-ultrarelativistic case, and to the quadrupolar (detuning) impedance in the ultrarelativistic case. This contribution presents the extension to the quadrupolar impedance in the non-ultrarelativistic case, as well as benchmarks with other available methods to compute the impedance. In particular, all the components of the impedances are benchmarked with Tsutsui's model, i.e. in the ultrarelativistic limit, with the model for a flat chamber impedance recently computed by N. Mounet and E. Métral, in the case of finite relativistic gamma, and with CST Particle Studio simulations.

THPZ011	Optimization of Chromatic Sextupoles in Electron Storage Rings Using Genetic Algorithms	3705
	Z. Duan IHEP Beijng, Beijing, People's Republic of China Q. Qin IHEP Beijing, Beijing, People's Republic of China
	Funding: Work supported by National Science Foundation of China contract 10725525. In order to suppress the head-tail instability, strong chromatic sextupoles are used in modern electron storage rings to correct large chromaticities due to small emittance or strong insertion quadrupoles to squeeze the bunch size at some places. However, the introduction of strong chromatic sextupoles also brings severe nonlinearity and might reduce dynamic aperture drastically. In the case of several sextupole families, the genetic algorithms are applied to find suitable configurations of sextupole strengths, directly maximizing dynamic aperture. A GeneRepair operator is introduced into the algorithm to correct chromaticities and optimize the dynamic aperture simultaneously in electron storage rings.

THPZ012	Luminosity Enhancement and Performance in BEPCII	3708
	Q. Qin, J. Cao, J. Cheng, Y.L. Chi, H. Dong, Z. Duan, D. Ji, W. Kang, S.P. Li, L. Ma, H. Qu, C.H. Wang, G.W. Wang, J.Q. Wang, X.H. Wang, Y. Wei, J. Xing, G. Xu, C.H. Yu, J. Yue, C. Zhang, Y. Zhang IHEP Beijing, Beijing, People's Republic of China
	The Beijing Electron Positron Collider (BEPC) was upgraded to a factory-like machine –- BEPCII, during last several years. From last November, the BEPCII was commissioned again for its luminosity. Efforts on optics correction including optimizing the strengths of superconducting quadrupoles near the IP, orbits correction concerning beam energy, etc, make the transvers tunes possible to move very close to half integer, bringing a big luminosity increase. The background of the detector is also reduced with beam commissioning, and finally fit the requirements of data taking. Further luminosity commissioing, including coupling optimization, beta-waist tuning, was carried on, and the luminosity reached 6.49·10³² cm^-2 s^-1 during routine operation. Some measures of luminosity enhancement and the luminosity related accelerator physics issues will be discussed.

Paper

Title

Page

Transverse Impedance Calculation for Simplified Model of Ferrite Kicker Magnet with Beta < 1

742

N. Wang, Q. Qin
IHEP Beijing, Beijing, People's Republic of China

In high intensity rings, kicker magnet is usually considered as a main source to the total impedance. Transverse coupling impedance of a simplified kicker model has been derived analytically in the ultrarelativistic limit. We extend the result to the general case of v < c, and present the analytical formulae of both horizontal and vertical transverse impedances. Numerical results are given for the CSNS extraction kicker magnets.

MOPS073

Impedance Calculation for Simple Models of Kickers in the Non-ultrarelativistic Regime

772

N. Biancacci, N. Mounet, E. Métral, B. Salvant, C. Zannini
CERN, Geneva, Switzerland
N. Biancacci, M. Migliorati, A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma, Italy
Q. Qin, N. Wang
IHEP Beijing, Beijing, People's Republic of China

Kicker magnets are usually significant contributors to the beam coupling impedance of particle accelerators. An accurate understanding of their impedance is required in order to correctly assess the machine intensity limitations. The field matching method derived by H. Tsutsui for the longitudinal and transverse dipolar (driving) impedance of simple models of kickers in the ultrarelativistic regime was already extended to the non-ultrarelativistic case, and to the quadrupolar (detuning) impedance in the ultrarelativistic case. This contribution presents the extension to the quadrupolar impedance in the non-ultrarelativistic case, as well as benchmarks with other available methods to compute the impedance. In particular, all the components of the impedances are benchmarked with Tsutsui's model, i.e. in the ultrarelativistic limit, with the model for a flat chamber impedance recently computed by N. Mounet and E. Métral, in the case of finite relativistic gamma, and with CST Particle Studio simulations.

THPZ011

Optimization of Chromatic Sextupoles in Electron Storage Rings Using Genetic Algorithms

3705

Z. Duan
IHEP Beijng, Beijing, People's Republic of China
Q. Qin
IHEP Beijing, Beijing, People's Republic of China

Funding: Work supported by National Science Foundation of China contract 10725525.
In order to suppress the head-tail instability, strong chromatic sextupoles are used in modern electron storage rings to correct large chromaticities due to small emittance or strong insertion quadrupoles to squeeze the bunch size at some places. However, the introduction of strong chromatic sextupoles also brings severe nonlinearity and might reduce dynamic aperture drastically. In the case of several sextupole families, the genetic algorithms are applied to find suitable configurations of sextupole strengths, directly maximizing dynamic aperture. A GeneRepair operator is introduced into the algorithm to correct chromaticities and optimize the dynamic aperture simultaneously in electron storage rings.

THPZ012

Luminosity Enhancement and Performance in BEPCII

3708

Q. Qin, J. Cao, J. Cheng, Y.L. Chi, H. Dong, Z. Duan, D. Ji, W. Kang, S.P. Li, L. Ma, H. Qu, C.H. Wang, G.W. Wang, J.Q. Wang, X.H. Wang, Y. Wei, J. Xing, G. Xu, C.H. Yu, J. Yue, C. Zhang, Y. Zhang
IHEP Beijing, Beijing, People's Republic of China

The Beijing Electron Positron Collider (BEPC) was upgraded to a factory-like machine –- BEPCII, during last several years. From last November, the BEPCII was commissioned again for its luminosity. Efforts on optics correction including optimizing the strengths of superconducting quadrupoles near the IP, orbits correction concerning beam energy, etc, make the transvers tunes possible to move very close to half integer, bringing a big luminosity increase. The background of the detector is also reduced with beam commissioning, and finally fit the requirements of data taking. Further luminosity commissioing, including coupling optimization, beta-waist tuning, was carried on, and the luminosity reached 6.49·10³² cm^-2 s^-1 during routine operation. Some measures of luminosity enhancement and the luminosity related accelerator physics issues will be discussed.