TY - BOOK

T1 - X-Band LLRF Developments for High Power CLIC Test Stands and Waveguide Interferometry for Phase Stabilisation

AU - Edwards, Amelia

PY - 2022/10/12

Y1 - 2022/10/12

N2 - This thesis describes the upgrade of the first high power X-band RF test for highgradient accelerating structures at CERN, as required for the e+ e- collider researchprogram; Compact Linear Collider, CLIC.Significant improvements to the control system and operation of the first teststand, Xbox-1, are implemented. The design and commissioning of the new LowLevel Radio Frequency, LLRF, system is described in detail. The upgrade also encompasses software, interlock systems, timing, safety and control. The new LLRFrequires an up-convertor to convert an input signal at 187.4 MHz to 11.806 GHz. Themost common method is a phase locked loop, PLL, an alternative method was envisioned which uses single side-band up-convertor. This necessitated the design andmanufacture of a custom cavity filter. The up-convertor and PLL are compared andboth are implemented in the new LLRF.The new LLRF system is implemented at Xbox1 and used to RF condition a50 MW CPI klystron, the final output power was 45 MW for a 50 ns RF pulse length.The phase and amplitude of the LLRF, TWT and klystron are characterised withboth the PLL and up-convertor. The klystron phase stability was studied using asensitivity analysis.The waveguide network between the klystron and the accelerating structures isapproximately 30 m. This network is subject to environmental phase changes whichaffect the phase stability of the RF arriving at the structures. A single path inteferometer was designed which will allow a phase measurement pulse at a secondary frequency to be injected into the waveguide network interleaved with klystron pulses.The interferometer is commissioned in the lab and low power measurements validate its operation. The system is then integrated into the high power network atXbox1 and used to measure phase shifts in the waveguide network which are correlated with temperature.

AB - This thesis describes the upgrade of the first high power X-band RF test for highgradient accelerating structures at CERN, as required for the e+ e- collider researchprogram; Compact Linear Collider, CLIC.Significant improvements to the control system and operation of the first teststand, Xbox-1, are implemented. The design and commissioning of the new LowLevel Radio Frequency, LLRF, system is described in detail. The upgrade also encompasses software, interlock systems, timing, safety and control. The new LLRFrequires an up-convertor to convert an input signal at 187.4 MHz to 11.806 GHz. Themost common method is a phase locked loop, PLL, an alternative method was envisioned which uses single side-band up-convertor. This necessitated the design andmanufacture of a custom cavity filter. The up-convertor and PLL are compared andboth are implemented in the new LLRF.The new LLRF system is implemented at Xbox1 and used to RF condition a50 MW CPI klystron, the final output power was 45 MW for a 50 ns RF pulse length.The phase and amplitude of the LLRF, TWT and klystron are characterised withboth the PLL and up-convertor. The klystron phase stability was studied using asensitivity analysis.The waveguide network between the klystron and the accelerating structures isapproximately 30 m. This network is subject to environmental phase changes whichaffect the phase stability of the RF arriving at the structures. A single path inteferometer was designed which will allow a phase measurement pulse at a secondary frequency to be injected into the waveguide network interleaved with klystron pulses.The interferometer is commissioned in the lab and low power measurements validate its operation. The system is then integrated into the high power network atXbox1 and used to measure phase shifts in the waveguide network which are correlated with temperature.

U2 - 10.17635/lancaster/thesis/1802

DO - 10.17635/lancaster/thesis/1802

M3 - Doctoral Thesis

PB - Lancaster University

ER -