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The high power demonstration of the PETS ON/OFF operation with beam. I. Syratchev for CLIC team. Some history…. Back in 2003 we have looked into many different scenarios of the local RF power production termination…. …and developed the very special one with modification of the PETS impedance.
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The high power demonstration of the PETS ON/OFF operation with beam. I. Syratchev for CLIC team
Back in 2003 we have looked into many different scenarios of the local RF power production termination… …and developed the very special one with modification of the PETS impedance
In 2008, with changing the CLIC frequency, the different options with destructive recirculation were reconsidered and special RF components were developed… Variable reflector #1 Tuneable splitter with rotating section On Off Internal recirculation External recirculation PETS power production On Off
Compact design of the high RF power variable reflector #2 (2010) Transmission 10.5 Gap width (mm) 2.5 Frequency, GHz 11.0 13.0 The variable reflector is a core element of the PETS ON/OFF mechanism. It is activated when the local termination of the RF power production in PETS is required. Radiation through the chokes S-parameters, dB ON S-parameters, dB OFF
PETS ON/OFF operation (CLIC PETS) “Closed” circuit RF phase was tuned using HFSS simulations with beam. ON /2 at 12 GHz (WR90) OFF Stored energy, arb. /4 (working point) Extra length of the WR90 straight section, mm Full model analysis (GDFIDL + HFSS) Power extracted from the drive beam Power to the structure
The variable RF reflector. The variable RF short circuit OFF Reflection Transmission Bold line – measured Thin line -HFSS ON
Modification of the TBTS PETS tank layout in 2011. External recirculation loop Internal recirculation Variable reflector Variable short circuit Variable Power splitter and Phase shifter, GYCOM (Russia).
Short circuit S-parameters measured at two extreme (locked) positions Full recirculation. Reference point. Forward Piston tuning range RF phase RF power Reflected Phase tuning Reference (“0”) phase position • Procedure: • Low (3A) current, short (200 ns) pulse • Reflector was set on the full reflection • The short circuit position was tuned to provide highest peak power and flat RF phase both for the forward and the reflected pulses. Reflector is set on full reflection Measured isolation>20 dB
Waveform for the different reflection and fixed (1800) phase advance In the PETS Combination x 4 0N 1800 0FF To the accelerating structure 0N 0FF 0N 0FF 0N 0FF Summarized by AlexeyDubrovskiy • Procedure: • Medium (10 A) current, long (240 ns) pulse • The short circuit was set on the expected 1800 phase advance position. • The variable reflector position was change from full transmission to the full reflection.
PETS with recirculation modeling and analysis Measured transfer spectra of the recycling loop Measured current pulse Artificial RF phase delay for tuning PETS single bunch response (GDFIDL) 0N OFF Number of round trips OFF case Number of bunches Multi-bunch part OFF case OFF case The complete system single bunch response and spectrum RESULT
Simulation vs. experiment PETS output, forward Spectra comparison On power (simulated/measured) OFF power (measured) OFF power (simulated)
The PETS ON/OFF capability was successfully demonstrated in experiments with drive beam in CTF3. Currently it is used to provide RF power for the two-beam experiments in TBTS