121351951
LLRF systems for subharmonic buncher system of BEPCII Linac
The linear accelerator (Linac) completed in 2007 for the upgrading project of the Beijing Electron Positron Collider (BEPCII) provides 1.89 GeV electrons and positrons for the storage rings. BEPCII Linac decides to update the bunching system and adopts two-bunch operation to enhance beam quality and injection rate as its second update phase. Two subharmonic bunchers will be used in this project: one operates at 142.8 MHz and the other operates at 571.2 MHz. Each subharmonic buncher consists of the bunching cavity, power source, LLRF system and other related subsystems. This paper mainly describes the LLRF systems for the subharmonic buncher systems (SHB). (C) 2009 Elsevier B.V. All rights reserved.
38812708
Superconducting RF activities at Peking University
The RF superconducting group at the Institute of Heavy Ion Physics of Peking University is developing Nb cavities for high-brightness electron sources. A series of efforts has been made since fall 1988 to construct a class 100 laboratory suitable for processing and assembling Nb cavities, as well as to develop equipment and techniques for the design surface treatment and RF test of superconducting cavities. The fields of fundamental and high-order modes, as well as wakefield potentials, were studied using the SUPERFISH, URMEL, and TBCI codes during design. The preparation of the Nb cavity and the structure of the cryostat are described and preliminary results of Q versus temperature are presented and discussed. An accelerating field of 8.6 MV/m was obtained with a Q/sub 0/ of 6.5*10/sup 8/ at 2.25 K. In addition, coaxial and pillbox cavities were designed and constructed to test the RF properties of high-T/sub c/ YBaCuO samples.<<ETX>>
64627689
The progress of development of four kickers' bump system for injection in HLS ring
There are three kicker magnets to manipulate local bump orbit in Hefei storage ring, which could satisfy basically the commissioning and operations of General Purpose Light Source (GPLS) mode. In the Phase Two Project of HLS, four kicker magnets will be employed and installed in one straight section to form a ladder-shaped bump orbit. So the parameters of bump orbit are independent of the ring lattice. The new system also satisfies the multicycle and multiturn injection of High Brightness Light Source (HBLS) mode and other modes, and it expected to run stably for a long time. This paper presents the development of the new bump orbit system.
54192336
Proton-proton correlations in central collisions of Ni + Ni at 1.93 A.GeV and the space-time extent of the emission source
Small-angle correlations of proton pairs produced in central Ni+Ni collisions at a beam energy of 1.93 A · GeV are investigated with the FOPI detector system at GSI Darmstadt. Simultaneous comparison of longitudinal and transverse correlation functions with the predictions of the Koonin model allows to unravel the space-time ambiguity of the source extension. The determination of the source rest frame is found essential for the identification of this effect. For the present system, the selection of central events comprising about 8% of the total cross section allows for the isolation of a compact source in momentum space which is centered around the c.m. velocity of the colliding nuclei. Taking into account the strong collective expansion of the participant zone, which introduces a reduction of the extracted source radius of more than 30%, r.m.s. radius and emission time parameters of Rrms=(4.2±1.2) fm and trms=(11+7-5) fm/c are extracted, respectively. In contrast, the analysis of the angle-integrated correlation function mixes the spatial and temporal size of the source and gives an upper limit Rrms=(7.0 ± 0.8) fm of the source radius.
122831377
PERFORMANCE OF THE DIAGNOSTICS FOR NSLS-II LINAC COMMISSIONING
The National Synchrotron Light Source II (NSLS-II) is a state of the art 3-GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac, a 3-GeV booster synchrotron and associated transfer lines. The transfer lines not only provide a means to deliver the beam from one machine to another, they also provide a suite of diagnostics and utilities to measure the properties of the beam to be delivered. In this paper we discuss the suite of diagnostics that will be used to commission the NSLS-II linac and measure the beam properties. The linac to booster transfer line can measure the linac emittance with a three screens measurement or a quadrupole scan. Energy and energy spread are measured in a dispersive section. Total charge and charge uniformity are measured with wall current monitors in the linac and transformers in the transfer line. We show that the performance of the diagnostics in the transfer line will be sufficient to ensure the linac meets its specifications and provides a means of trouble shooting and studying the linac in future operation.
54868722
EXPERIMENTAL PROGRESS OF DC-SC PHOTOINJECTOR AT PEKING UNIVERSITY*
Beam loading experiments on DC-SC photoinjector test facility have been finished at 4.4 K. Upon the present experiments, the gradient of 6 MV/m is achieved. The maximum energy gain is 1.1 MeV at 4.4 K. With average beam current of 270 mA, the measured rms emittance is about 5 mm-mrad at the beam energy of 500 keV. Experiments on the test facility has validated that the DC-SC photoinjector is a good choice to provide moderate average current electron beams with low bunch charge and very high repetition rate.
118687006
Transverse Energy and Charged Particle Multiplicity in 14.6 Gev/c Proton-Nucleus Collisions.