• B.K. Sahu, R. Ahuja, G.K. Chowdhury, R.N. Dutt, S. Ghosh, D. Kanjilal, D.S. Mathuria, A. Pandey, P. Patra, A. Rai, A. Roy, K. Singh
  IUAC, New Delhi

The existing phase locking scheme of the quarter wave resonators(QWR) in the first operational module of the superconducting heavy ion linear accelerator of Inter University Accelerator Centre consists of a fast (electronic) and a slow time scale control. Helium gas operated slow tuner turns out to be a complicated, somewhat unreliable and expensive for long term operation of the linac. In an alternate scheme to handle the slow time part of the phase control, the tuner plate is deflected by using a combination of a stepper motor for course adjustments and a piezoelectric crystal for fine adjustment of the frequency. The piezoelectric actuator is used in closed loop along with dynamic I-Q based electronic tuner to phase lock the superconducting cavities. During a recent cold test of a QWR, the frequency range of the resonator by the piezoelectric tuner was measured to be 1 kHz. In this test, the fundamental frequency of the QWR was first brought to 97.000 MHz by the mechanical course tuner. The resonator was then locked at a field of 3.8 MV/m at 6 W of helium power and 40 W of forward power from the RF amplifier using the resonator controller along with the piezoelectric tuner.