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ON/OFF news

ON/OFF news. Compact design of the high RF power variable (mechanically) reflector. ON. OFF. Transmitted. RF power, dB. Reflected. Stroke 8.0 mm. Piston position (gap width), mm.

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ON/OFF news

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  1. ON/OFF news

  2. Compact design of the high RF power variable (mechanically) reflector ON OFF Transmitted RF power, dB Reflected Stroke 8.0 mm Piston position (gap width), mm 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

  3. PETS ON/OFF operation (CLIC PETS) ON OFF Power extracted from the drive beam Power to the structure

  4. Broadband high RF power variable reflector prototype RF measurements Open Closed Stroke 8 mm

  5. High power variable short circuit Originally the reflector was designed to provide reliably the 1800 phase advance. The dynamic range was increased up to about 2200 by further movement of he piston, until the chamber resonance became a danger. +30MHz

  6. Variable reflector (for tuning the recirculation coupling) TBTS PETS layout with internal recirculation for testing the ON/OFF concept. PETS output ON OFF Structure input Movable RF short circuit (for tuning the resonant length) (as predicted by computer simulation)

  7. The components have been installed on the PETS tank. Variable reflector Movable RF short circuit

  8. Few words about TBTS results during the past testing period Chat in a corridor: Igor... ‘Roberto, why do we need to run PETS with power levels above 200 MW?’ Roberto... ‘ Well, it works, so why do you ask? As well we have showed 150 M/m.’ It did, indeed! With BDR> 0.3 when peak power was > 200 MW! Measured RF power extraction Peak power in the PETS MW CLIC requirement BDR in recycling loop ns

  9. Let’s look inside Highest peak power point phase shifter IN OUT OUT attenuator E-bend/split E-bend/direct IN attenuator load split E-bend IN • Observations: • All he stainless steel flanges show sort of breakdown erosion on the surface. • The copper surfaces in attenuator (GYCOM) are seriously damaged in ALL the channels. • In the phase shifter (also made by GYCOM) copper surface is pretty clean.

  10. ON/OFF tests with beam. The RF variable reflector prototype installed in TF3 OFF Reflection Transmission Bold line – measured Thin line -HFSS Variable reflector installed in CTF3 TBTS PETS tank ON

  11. ON/OFF, operation with beam

  12. Short circuit S-parameters measured at two extreme (locked) positions Step#1: Identify the short circuit position for the full (in-phase) recirculation as a reference. 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

  13. Step#2: Validate the short circuit position for the destructive (anti-phase) recirculation (0FF-mode). Waveform for the different reflection and fixed (1800) phase advance In the PETS 1800 Combination x 4 0N 0FF To the accelerating structure 0N 0FF 0N 0N 0FF 0FF • 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. Summarized by AlexeyDubrovskiy Due to some? luck, the necessary RF phase tuning range stays within the hardware limits.

  14. PETS with recirculation modeling and analysis Measured transfer spectra of the recycling loop 0N OFF artificial RF phase delay for tuning PETS single bunch response (GDFIDL) 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

  15. “0” “45” “90” “135” “180” Examples of the power production for the full reflection and varying recirculation phase (ideal current pulse ).

  16. Simulation vs. experiment PETS output, forward Spectra comparison 0N (simulated/measured) OFF (measured) OFF (simulated)

  17. 30 October (logbook pictures) 2.7 A, 340 ns 4.5 A, 240 ns Interlock level #1 #3 #2 interlock was deactivated #4 #1 Power #2 150 MW 45 MW Vacuum gauges PMT signal Peak power Current #3 80 MW #4 80 MW Pulse length at 50% level Breakdown events? PMT installed on the PETS tank

  18. TBTS processing results to date

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