Field Profile Adjustment and Beam Acceleration Test of PEFP 3 MeV RFQ

As a front end part of the 100-MeV proton linac of Proton Engineering Frontier Project (PEFP), a 20-MeV proton accelerator has been installed and tested at Korea Atomic Energy Research Institute (KAERI) site. The 20-MeV accelerator consists of a 50-keV proton injector, a 3-MeV Radio frequency quadrupole (RFQ) and a 20-MeV Drift Tube Linac (DTL). After the permission of the accelerator operation at April 2007 from KINS, efforts were focused on the stabilization and increase of the proton beam current, especially from the 3-MeV RFQ. Several modifications were applied to both the proton injector and RFQ such as an reduction of the extraction hole diameter of the ion source, reduction of the whole length of the Low Energy Beam Transport (LEBT), an installation of the electron trap in front of the RFQ, re-align of the accelerator components. Finally, we measured and re-tuned the RFQ cavity field profile and could obtain the 20mA peak current from the RFQ. In this paper, we discuss about the retuning of the RFQ field profile and its effect on the beam current increase