Beam emittance plays an important role in any accelerator, and it is a main parameter to judge the performance of an accelerator. Emittance optimization is an indispensable part in conditioning and operation of the facility. For a laser-driven high brightness injector, different time structure of the laser pulse has different effects on transverse emittance. In order to compare Gaussian and flat-top laser pulse, systematic simulations of 500 pC have been done. From the simulation results, one can see that flat-top pulse laser will yield smaller minimal transverse beam size and transverse beam emittance than Gaussian pulse laser.
An S-band cavity BPM is designed for a new injector for HLS (Hefei Light Source). It consists of two cavities that work on 2448 MHz: a re-entrant position cavity tuned to TM110 mode and a reference cavity tuned to TM010 mode. Cut-through waveguides are used as pickups to suppress the monopole signal. Simulations with different assumption of dimension change are performed to evaluate errors caused by mechanical error and give general tolerance. Design of electronics is given. Theoretical resolution of this design is 31 nm.
A photocathode radio frequency gun,which is an S-band normal conducting 1.6 copper cell cavity with water cooling system,was installed in Hefei Light Source.In order to know its characteristics and get it into normal operation,continuous conditioning was conducted in the last few months.Beam charge and dark current charge were measured using integrating current transformer.The beam transverse size was determined as 1.63 mm in minimum using YAG screen and GigE Vision camera.Using multi-slits technique,the transverse emittance was measured and normalized at 1.95 mm·mrad with beam charge of 240 pC.The results provide a way to optimize the facility.
Bunch current is an important parameter for studying the injection fill-pattern in the storage ring and the instability threshold of the bunch, and the bunch current monitor also is an indispensable tool for the top-up injection. A bunch current measurement (BCM) system has been developed to meet the needs of the upgrade project of Hefei Light Source (HLS). This paper presents the layout of the BCM system. The system based on a high-speed digital oscilloscope can be used to measure the bunch current and synchronous phase shift. To obtain the absolute value of bunch-by-bunch current, the calibration coefficient is measured and analyzed. Error analysis shows that the RMS of bunch current is less than 0.01 mA when bunch current is about 5 mA, which can meet project requirement.
YANG YongLiangMA TianJiSUN BaoGenLU PingWANG JiGangZOU JunYingTANG LeiLei
