IHEP Beijing, Beijing
BEPCII is major upgrades of BEPC (Beijing Electron-Positron Collider). It is a double ring e±e collider as well as a synchrotron radiation (SR) source with its outer ring, or SR ring. As a collider, BEPCII operates in the beam energy region of 1-2.1 GeV with design luminosity of 1*1033cm-2s-1 at 1.89 GeV. As a light source, the SR ring operates at 2.5 GeV and 250 mA. Construction of the project started in the beginning of 2004. Installation of the storage ring components completed in October 2007. The BESIII detector was moved to the Interaction Region (IR) on May 6, 2008. In accordance to the progress of construction, the beam commissioning of BEPCII is carried out in 3 phases: Phase 1, with conventional magnets instead of the superconducting insertion magnets (SIM’s)n in the IR; Phase 2, with SIM’s in the IR; Phase 3, joint commissioning with the detector. The maximum luminosity reached to 2.3*1032cm-2s-1. This paper summarizes progress of the construction and commissioning in 3 phases, while focusing on the third phase.
* On behalf of the BEPCII Team
IHEP Beijing, Beijing
SINAP, Shanghai
RF deflectors can be used for bunch length measurement with high resolution. This paper describes the completed S-band travelling wave RF deflector and the bunch length measurement of the electron beam produced by the photocathode RF gun of Shanghai DUV-FEL facility. The deflector’s VSWR is 1.06, the whole attenuation 0.5dB, and the bandwidth 4.77MHz for VSWR less than 1.1. With laser pulse width of 8.5ps, beam energy of 4.2 MeV, bunch charge of 0.64 nC, the bunch lengths for different RF input power into the deflector were measured, and the averaged rms bunch length of 5.25 ps was obtained. A YAG crystal is used as a screen downstream of the deflector, with the calibrated value of 1pix =136um.