ON/OFF news

Reflected Transmitted Stroke 8.0 mm RF power, dB Piston position (gap width), mm ON OFF Compact design of the high RF power variable (mechanically) reflector Radiation through the chokes 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. S-parameters, dB

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

OpenClosed RF measurements Broadband high RF power variable reflector prototype Stroke 8 mm

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

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

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

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.’ Few words about TBTS results during the past testing period MW ns Measured RF power extraction CLIC requirement Peak power in the PETS BDR in recycling loop It did, indeed! With BDR> 0.3 when peak power was > 200 MW!

attenuator E-bend/split INOUT IN OUT phase shifter E-bend/direct Highest peak power point Let’s look inside attenuator loadsplit 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.

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

ON/OFF, operation with beam

Piston tuning range Phase tuning 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. Measured isolation>20 dB Forward Reflected RF phaseRF power Reference (“0”) phase position Reflector is set on full reflection 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.

Step#2: Validate the short circuit position for the destructive (anti-phase) recirculation (0FF-mode) FF 0N Waveform for the different reflection and fixed (180 0 ) phase advance Procedure:  Medium (10 A) current, long (240 ns) pulse  The short circuit was set on the expected phase advance position.  The variable reflector position was change from full transmission to the full reflection. 0N 0FF Summarized by Alexey Dubrovskiy To the accelerating structure Due to some? luck, the necessary RF phase tuning range stays within the hardware limits. Combination x 4 In the PETS 0N 0FF 0N 0FF

PETS single bunch response (GDFIDL) Measured transfer spectra of the recycling loop artificial RF phase delay for tuning Number of round trips The complete system single bunch response and spectrum Multi-bunch part Number of bunches PETS with recirculation modeling and analysis OFF case RESULT 0N OFF case OFF OFF case

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

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

interlock was deactivated Vacuum gauges Peak power Pulse length at 50% level PMT installed on the PETS tank Interlock level 2.7 A, 340 ns4.5 A, 240 ns #1 #2 #3 #2 #3#4 Breakdown events? Power PMT signal Current 30 October (logbook pictures) 45 MW 150 MW 80 MW

TBTS processing results to date