Cavity Frequency Measurement at FLASH and XFEL V. Ayvazyan, W. - PowerPoint PPT Presentation

Cavity Frequency Measurement at FLASH and XFEL V. Ayvazyan, W. Koprek, D. Kostin, G. Kreps Workshop on Linac Operation with Long Bunch Trains DESY, 23.02.2010

Goals • Remote cavity tuning at FLASH, XFEL and test stands – Remote and simultaneous frequency measurement of all cavities (no need to go in the tunnel) – Make use of standard RF distribution system, klystron, LLRF system, Master Oscillator etc. • Check tuner step motors in warm conditions to exclude mistakes of connectors, wires and software • Tuning of the cavities at the 1.3 GHz after cool down • Relax the cavities to initial frequencies before warming up • Test of the procedure in horizontal cryostat CHECHIA – warm SC cavity – low power from klystron – checking the frequency range and resolution DESY, 23.02.2010 Workshop on Linac Operation with Long 2 Bunch Trains

Measurement conditions Warm Cold Quality Factor 1.0e4 3.0e6 Frequency range [MHz] 1298.0 +/-0.4 1300.0 +/-0.4 Frequency step from pulse to pulse [kHz] 10 0.5 Measurement points (RF pulses) 80 1600 Frequency sensitivity [kHz] 25 1 DESY, 23.02.2010 Workshop on Linac Operation with Long 3 Bunch Trains

Requirements for the Frequency Sweeping System • Sweeping with constant reference frequency – 1.3GHz from Master Oscillator • Frequency range from -2.4 MHz to +0.4 MHz relative to 1.3GHz • Frequency resolution at least 0.5 kHz • Standard methods for field detection by diagnostic ADCs using DOOCS DESY, 23.02.2010 Workshop on Linac Operation with Long 4 Bunch Trains

Horizontal Test Stand DESY, 23.02.2010 Workshop on Linac Operation with Long 5 Bunch Trains

Hardware and Software of the Measurement Setup DESY, 23.02.2010 Workshop on Linac Operation with Long 6 Bunch Trains

Measurements: System characteristic DESY, 23.02.2010 Workshop on Linac Operation with Long 7 Bunch Trains

Measurements: Warm SC Cavity on a Table Frequency sweep (-2MHz; -20MHz) with step 10kHz DESY, 23.02.2010 Workshop on Linac Operation with Long 8 Bunch Trains

Measurements: Warm SC Cavity on a Table Frequency sweep (-2MHz; -10MHz) with step 10kHz Matlab interface DOOCS panel DESY, 23.02.2010 Workshop on Linac Operation with Long 9 Bunch Trains

Measurements: Warm SC Cavity in CHECHIA Motor Tuner Test DESY, 23.02.2010 Workshop on Linac Operation with Long 10 Bunch Trains

Conclusions • Cavity characterization in wide range of frequency ±20 MHz with high resolution 0.1 kHz • Safe solution for warm cavities – possible measurement of very small field gradient (only 1kW forward power from klystron at CHECHIA, 2.5W in warm cavity at resonance frequency) • No need for hardware change for the sweeping procedure (RF reference signal from MO) • Automated and simultaneous scan of many cavities will speed up setup of FLASH • Developed important procedure for large scale machines like XFEL & ILC DESY, 23.02.2010 Workshop on Linac Operation with Long 11 Bunch Trains

Plans • FLASH commissioning – Check of tuner motors at FLASH in March 2010 – Tuning of the cold cavities at FLASH in April 2010 – Preparing of DOOCS server for operators – Automated data logging • In future – Integration with the LLRF controller DESY, 23.02.2010 Workshop on Linac Operation with Long 12 Bunch Trains

Acknowledgements • Markus Hoffmann – for the theoretical advise • Clemens Albrecht and Frank Hoffmann – for help with CHECHIA test • Guenter Moeller – for hardware setup for initial tests DESY, 23.02.2010 Workshop on Linac Operation with Long 13 Bunch Trains

Thank You DESY, 23.02.2010 Workshop on Linac Operation with Long 14 Bunch Trains