• X.H. Yang, C.L. Tian, Y. Yin, T.P. Yu
  National University of Defense Technology, Changsha, Hunan
• Y.Q. Gu
  Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang
• S. Kawata, Y.Y. Ma
  Center for Optical Research and Education, Utsunomiya University, Utsunomiya
• F.Q. Shao
  National University of Defense Technology, Graduate School, Changsha
• H. Xu
  National University of Defense Technology, Parallel and Distributed Processing, Changsha
• M.Y. Yu
  Ruhr-Universität Bochum, Bochum

We have proposed a scheme for the generation of collimated proton beams from the interaction of an ultra-intense laser pulse with a rear hole target, which is studied by a 2.5D particle-in-cell (PIC) code PLASIM. When an ultraintense short laser pulse irradiates on such a target, the hot electrons will expand fast into the hole from the inner surfaces of the hole, and strong longitudinal sheath electric field and transverse electric field are produced. However, the plasma in the corners expand slower and be compressed strongly, and then a strong plasma jet is sprayed out from the corner with very high speed, which is just like what happened in armor piercing bullet due to the cumulative energy effect. The two jets extend into the hole and focus along the axis of the hole. At last, a high quality collimated proton beam can be obtained near the end of the hole along the propagation axis. It's found that the beam can propagate over a much longer distance without divergence. The effect of the hole diameter on the collimated proton beam is also investigated. Such target may serve as an important source for collimated proton beam in practical applications.

• C. Sun, J.Y. Li, S.F. Mikhailov, V. Popov, W. Wu, Y.K. Wu
  FEL/Duke University, Durham, North Carolina
• A. Chao
  SLAC, Menlo Park, California
• H. Xu, J. Zhang
  USTC/NSRL, Hefei, Anhui

Touschek lifetime of an electron beam in a storage ring depends on the beam polarization through the intrabeam scattering effect. Consequently, the electron beam polarization can be determined by comparing the measured Touschek lifetime of a polarized beam and an unpolarized beam. In this paper, we report a systematic experimental procedure to study the radiative polarization of a stored electron beam. Based upon this technique, we have successfully observed the polarization build-up of a 1.15 GeV electron beam in the Duke storage ring. Using the Touchek lifetime data, we are able to determine the equilibrium degree of the electron beam polarization and the time constant for the polarization build-up process.

• G. Feng, W. Fan, W.W. Gao, W. Li, L. Wang, H. Xu, S.C. Zhang
  USTC/NSRL, Hefei, Anhui

HLS (Hefei Light Source) is a dedicated synchrotron radiation research facility, whose emittance is relatively large. In order to improve performance of the machine, especially getting higher brilliance synchrotron radiation and increasing the number of straight sections for insertion devices, an upgrade project is on going. A new low emittance lattice, which keeps the circumference of the ring no changing, has been studied and presented in this paper. For the upgrade project, a new ring will be installed on current ground settlement of HLS and all of the magnets will be reconstructed. After optimization, two operation modes have been chosen for different users. Nonlinear dynamics shows that dynamic aperture for on-momentum and off-momentum particle is large enough. Beam lifetime has also been studied. Calculation results proves that expected beam lifetime about 8.5 hours can be obtained with a fourth harmonic cavity operation.

• L. Wang, W. Fan, G. Feng, W.W. Gao, W. Li, H. Xu, S.C. Zhang
  USTC/NSRL, Hefei, Anhui

The Hefei Light Source is composed of an 800 MeV storage ring, a 200 MeV electron linac and transfer line, which was designed and constructed twenty years ago. Several factors limit the performance of HLS, for example, less number of insertion devices and large beam emittance. To meet the requirements of synchrotron radiation users, an upgrade project of HLS will be carried out in the next two years. Several sub-systems will be renewed, such as magnet system, power supply, beam diagnostics, vacuum system, etc. The upgrade scheme is described in this paper, including magnet lattice design, nonlinear performance, collective effects,beam injection, orbit detection and correction, injector, etc.

• J.Q. Lan, B. Sun, Y.C. Sun, H. Xu
  USTC/NSRL, Hefei, Anhui

A brief, but clear, review of beam polarization theory is given in the paper. Particularly, the algorithm of spin linear transfer matrix (SLIM) is applied to remark the situation of beam in storage ring, specific to HLS (Hefei Light Source). Theoretical analysis indicates that the beam in HLS, working at 800MeV and 2.58/3.58 transverse tunes, could keep away from a variety of spin resonances, and should be able to build up high polarization.

• S.C. Zhang, W. Fan, G. Feng, W.W. Gao, H. Geng, Z.G. He, W. Li, L. Wang, H. Xu
  USTC/NSRL, Hefei, Anhui

In order to meet the increasing requirements of synchrotron radiation users, an upgrading plan of hefei light source is undergoing by National Synchrotron Radiation Laboratory (NSRL). The emittance of storage ring is reduced from 166nm.rad to 36nm.rad. In this paper, we study the beam close orbit distortions' (COD) sensitivity to the field and alignment errors in magnets. Estimation of the COD from various error sources is investigated. The distribution of beam position monitors and the location of correctors are reported in the paper. Simulation proves that COD can be corrected down to 50 microns level. In the same time the corrector strengths are weaker enough in the correction scheme.

• S.C. Zhang, W. Fan, G. Feng, W.W. Gao, W. Li, L. Wang, H. Xu
  USTC/NSRL, Hefei, Anhui

To enhance the performance of Hefei Light Source, an upgrade project is undergoing. The magnet lattice of storage ring will be reconstructed with 4 DBA cells, whose advantages are lower beam emittance and more straight section available for insertion devices. In order to assure smooth beam accumulation process under new low emittance lattice, the injector, which is composed of electron linac and beam transfer line, would be updated. The detail of upgrading Hefei Light Source transport line will be described in this paper. It include the upgrading of lattice, the orbit control of beam transfer line and others. It is hopeful to realize a high transfer efficiency and high injection efficiency for new lower beam emittance storage ring.