Development of the HLS 40kW Solid State Amplifier

In the HLS(Hefei Light Source) phase III upgrade plan, the 204MHz 40kW RF Solid State Amplifier (SSA) will replace the 25kW tetrode amplifier as the new RF power generator of 800MeV electron storage ring. This SSA contains sixty-five 650W amplifier units (one unit drives sixty-four’s), with two-stage combination to reach the 40kW output. All of the SSA components has been manufactured and tested, each of them meets the requirements. The SSA system has been assembled in the end of 2012 and is in testing to date. The 45kW output power has been obtained. The SSA’s design, manufacture, and test results are presented in the paper. DESIGN OF THE HLS RF SSA In the past ten years, more and more high power Solid State Amplifiers have been used in accelerators, since the first one was developed in SOLEIL [1-6]. In the HLS phase III upgrade plan, the 25kW tetrode amplifier will be retired, we decide to develop a 40kW SSA. The development began in 2008, when the available RF power of single SSA module was 330W, therefore 128 modules would be needed to obtain the 40kW. The power combining method is 8×8×2(twice of 8-1 and then 2-1), the corresponding power splitting way of the drive signal is 1÷2÷8÷8. Ten 330W modules and samples of each kind of combiners/splitters were produced and tested in 2010[7]. However, in 2011 a new kind of SSA module manufactured by China BBEF Company can output 650W (nominal value). We decided to modify the SSA design. The sixty-four 650W modules would be used and their output be combined by 8×8. The structure of the 40kW RF SSA is shown in the figure 1. The 40kW SSA is designed to leave a large space for the HLS future upgrade, since the RF power requirement of the phase III project is about 22kW. But the power efficiency of amplifier module is low, when the 40kW SSA works at the 20kW level. In order to improve the efficiency, the 30kW operating model will be adopted for HLS Phase III. One 1-6 splitter and one 6-1 combiner replaces the first 1-8 and the last 8-1 respectively. the combining method is changed to 8×6, only 48 modules will be used . The conversion from 30kW to 40kW or in turn is convenient, without too much adjustment in the main structure of the SSA.