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

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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

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Measurement conditions

3.0e6 1.0e4 Quality Factor 1 25 Frequency sensitivity [kHz] 1600 80 Measurement points (RF pulses) 0.5 10 Frequency step from pulse to pulse [kHz] 1300.0 +/-0.4 1298.0 +/-0.4 Frequency range [MHz] Cold Warm

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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

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Horizontal Test Stand

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Hardware and Software

• f the Measurement Setup

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Measurements: System characteristic

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Measurements: Warm SC Cavity on a Table

Frequency sweep (-2MHz; -20MHz) with step 10kHz

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Measurements: Warm SC Cavity on a Table

Frequency sweep (-2MHz; -10MHz) with step 10kHz

Matlab interface DOOCS panel

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Measurements: Warm SC Cavity in CHECHIA

Motor Tuner Test

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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

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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

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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

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Thank You