Mr Michal Elias (CERN)
The HIE-ISOLDE project is a major upgrade of the ISOLDE and REX-ISOLDE (radioactive nuclear beams) facilities at CERN. The most significant improvement will come from replacing most of the existing REX accelerating structure by a 40 MV superconducting linac based on 32 independently phased superconducting quarter-wave resonators (cavities). The resonators operate at a frequency of 101.28 MHz and at a relatively high Q, providing an operational bandwidth of only a few Hertz. The LLRF system is designed to be fully digital, with direct RF sampling and digital quadrature demodulation, as well as direct RF generation by a fast DAC. The field in the superconducting resonator needs to be stabilized with an accuracy of 0.2°/0.2%. This imposes strict requirements on the system reference clock quality in terms of stability and aperture jitter. A low phase-noise clock generator locked to a GPS disciplined reference oscillator has been developed. This poster presents the design and performance of the clock generator as well as achieved results with the direct RF sampling and generation.
Dr Daniel Valuch (CERN)