Design, development and power test of a spiral buncher RF cavity for the high current injector at IUAC

Abstract

Abstract A 48.5 MHz spiral buncher cavity in the Medium Energy Beam Transport section (MEBT) of the High Current Injector (HCI) provides longitudinal beam matching at the entrance of the Drift Tube Linac (DTL). The spiral type cavity has been chosen for its high shunt impedance and mechanical stability. The cylindrical chamber was fabricated of copper plated stainless-steel, while OFHC copper was used for the inner components, leading to better results than previous similar cavities. The experimentally measured quality factor, shunt impedance, and resonance frequency fit very well with the design values. The bead-pull measurement technique has been used to validate the electric field profile. A fine tuner has been developed and installed to correct the frequency shift while the cavity is phase and amplitude locked. An air-cooled power coupler has been designed, developed, and installed. The cavity has been tested up to the full power of 1 kW to produce 27 kV across each gap. The X-ray energy spectroscopy technique has been used to measure the gap voltages across the drift tubes. The designed and measured value of the quality factor is 4000 and 3600, respectively. The details of the design, development, and power testing are discussed in this article.