• H. S. Kim, Y.-S. Cho, I.-S. Hong, D. I. Kim, H.-J. Kwon, K. T. Seol, Y.-G. Song
  KAERI, Daejon

The RF amplitude and the phase stability requirements of the LLRF system for the PEFP(Proton Engineering Frontier Project) proton linac are within 1% and 1 degree, respectively. As a prototype of the LLRF, a simple digital PI control system based on commercial FPGA board is designed and tested. The main features are a sampling rate of 40 MHz which is four times higher than the down-converted cavity signal frequency, digital in-phase and quadrature detection, pulsed mode operation with the external trigger, and a simple proportional-integral feedback algorithm implemented in a FPGA. The developed system was tested with 3 MeV RFQ and 20 MeV DTL, and satisfied the stability requirements.

• K. T. Seol, Y.-S. Cho, D. I. Kim, H. S. Kim, H.-J. Kwon
  KAERI, Daejon

The PEFP LLRF system for the 3MeV RFQ and 20MeV DTL has been developed. The stability of ±1% in the amplitude and ±1˚ in the phase is required. Therefore, the drift of the analog components should be low to satisfy the requirement. Analog chassis as a prototype of LLRF system is configured and tested. RF components including an IQ modulator, an RF switch, a mixer, phase comparators, RF splitters, RF filters and trip circuit for high VSWR are installed in this chassis. This performs the shift of RF amplitude and phase from IQ signal, down-conversion to 10MHz IF signal, interlock for arc and high VSWR, and RF/clock distribution. The amplitude and phase stability of each component are measured to check the effect on the whole system performance. The detailed configuration and test results are presented.

• H.-J. Kwon, Y.-S. Cho, I.-S. Hong, J.-H. Jang, D. I. Kim, H. S. Kim, K. T. Seol
  KAERI, Daejon

The beam test of the Proton Engineering Frontier Project (PEFP) 20 MeV proton linear accelerator started again, after the upgrade of the RF control system, One of the important goals of the test is to increase the beam current to the design level. Tuned current transformers were installed along the DTL tanks to measure the beam current itself and possible beam loss along the accelerator. Because there were no empty drift tubes, the current transformers should be installed between DTL tanks. Therefore, the tuning plans were developed to obtain the desired beam properties with the limited number of beam diagnostic devices. Also two BPMs for the time of flight measurement and energy degrader were installed at the end of the 20 MeV accelerator to measure the beam energy. In this paper, the overall test results including beam current and energy measurement are presented.