45 GHz Microwave Power Transmission and Coupling Scheme Study with Superconducting ECR Ion Source at IMP.

A next generation heavy ion accelerator complex HIAF (High Intensity heavy ion Accelerator Facility) was proposed by IMP and officially approved for nuclear physics and high energy density physics research. HIAF requests ion source that is able to deliver 50 pμA of 238U35+ pulsed beam and 25 pμA of ²³⁸U³⁵⁺ CW beam for injector of a superconducting heavy ion linac. In order to meet the beam intensity requirements of highly charged heavy ions, a 45 GHz superconducting ECR ion source FECR (a Fourth generation ECR ion source) is under intense R&D at IMP. The effective power absorption form the microwaves to the plasma is key issue for increasing the beam intensity. Therefore, we introduced a 45 GHz gyrotron system which is capable for providing output power up to 20 kW in both CW and pulse modes as a microwave power source for FECR. Other than the gyrotron oscillator, the microwave power transmission coupling and ECR heating are critical issues for FECR. Since the wavelength of 45 GHz microwave is about 6.67 mm and the maximum power level is 20 kW, the quasi-optical transmission scheme is utilized for high power transmission. The technical details of transmission line and coupling system will be presented in this paper. After off-line tests of microwave transmission efficiency and mode purity, 45 GHz gyrotron microwave source will be commissioned with SECRAL II (a superconducting ECR ion source optimized for 28 GHz operation), and some preliminary results of ECR heating and intense beam production will be discussed in this paper. [ABSTRACT FROM AUTHOR]