CLIC Drive Beam Phase Stabilisation CLIC Drive Beam Phase Stabilisation Alexander Gerbershagen Doctoral thesis for: University of Oxford, FONT group CERN, BE-ABP-CC3 group CLIC Drive Beam Phase Stabilisation 02/08/2013 1
Content Content • CLIC overview • CLIC stability simulations Error Tolerances Analysis of error propagation Stabilisation via a feed-forward • CTF3 measurements Simulation of feed-forward system prototype CLIC Drive Beam Phase Stabilisation 02/08/2013 2
Phase stability simulations for CLIC CLIC Drive Beam Phase Stabilisation 02/08/2013 3
CLIC Layout at 3 TeV - Overview CLIC Layout at 3 TeV - Overview beam size 45 x 1 nm “[…] Key studies will address stability and alignment, timing and phasing […]” – CLIC CDR (Executive Summary: work-packages 2012–2016) CLIC Drive Beam Phase Stabilisation 02/08/2013 4
Drive Beam Tolerances Drive Beam Tolerances and Error Analysis and Error Analysis Plot: D. Schulte Step 1: Analyse the error, consider four Drive Beam sections: 1. Drive Beam accelerator 2. Compressor chicane 3. Recombination scheme 4. PETS & Main Linac Step 2: Correct the error with a feed-forward system CLIC Drive Beam Phase Stabilisation 02/08/2013 5
Drive Beam Tolerances Drive Beam Tolerances and Error Analysis and Error Analysis Plot: D. Schulte Step 1: Analyse the error, consider four Drive Beam sections: 1. Drive Beam accelerator 2. Compressor chicane 3. Recombination scheme 4. PETS & Main Linac Step 2: Correct the error with a feed-forward system CLIC Drive Beam Phase Stabilisation 02/08/2013 6
Error propagation analysis Error propagation analysis Simulation tool Simulation tool Simplified process diagram of operation of Drive Beam error tracking simulation tool. CLIC Drive Beam Phase Stabilisation 02/08/2013 7
Analysing the errors (1/4) Analysing the errors (1/4) Drive Beam accelerator Drive Beam accelerator • RF amplitude and phase errors lead to beam energy errors • Drive Beam bunch charge errors cause beam loading error in the accelerator leading to beam energy error RF potential Wake potential Wake potential (V) RF potential (V) Simulations: R. Wegner • Calculated in frequency domain, then fft to time domain • Higher order resonances included in wake fields calculation • 3 points per sinus wave, hence strong beating in RF potential CLIC Drive Beam Phase Stabilisation 02/08/2013 8
Analysing the errors (2/4) Analysing the errors (2/4) Compressor chicane Compressor chicane Simulations: A. Aksoy Best stability is provided by chicane with R 56 = -0.1m CLIC Drive Beam Phase Stabilisation 02/08/2013 9
Analysing the errors (3/4) Analysing the errors (3/4) Recombination scheme Recombination scheme • Bunch frequency is 0.5 GHz • 240 ns long trains have a relative phase-shift of 180⁰ • Acceleration at 1 GHz is equal for all trains • RF deflector at the delay loop operates at 0.5 GHz and distinguishes between the ‘even’ and the ‘odd’ trains CLIC Drive Beam Phase Stabilisation 02/08/2013 10
Analysing the errors (3/4) Analysing the errors (3/4) Recombination scheme Recombination scheme Beam has a recombination factor 24, changing bunch frequency from 0.5 to 12GHz Recombination in the first combiner ring is non-trivial, since the design allows to accommodate longer trains for the lower energy operation modes CLIC Drive Beam Phase Stabilisation 02/08/2013 11
Analysing the errors (4/4) Analysing the errors (4/4) Main Beam acceleration Main Beam acceleration Analyze the impact of the Drive Beam errors on the Main Beam energy CLIC Drive Beam Phase Stabilisation 02/08/2013 12
Analysing the errors (4/4) Analysing the errors (4/4) Main Beam acceleration Main Beam acceleration • Interval 11.7 GHz – 12.3 GHz Simulations: O. Kononenko • Calculate in frequency domain, then fft CLIC Drive Beam Phase Stabilisation 02/08/2013 13
Analysing the errors Analysing the errors Phase error as function of frequency Phase error as function of frequency • Strong filtering by the in combination scheme • Peaks from errors resonant with 240 ns long trains • Suppression of peaks by drive beam accelerating When trains recombine, structures their errors overlap • Suppression of high frequencies by convoluting the signal with main beam accelerating structure RF filling CLIC Drive Beam Phase Stabilisation 02/08/2013 14
Drive Beam Tolerances Drive Beam Tolerances and Error Analysis and Error Analysis Plot: D. Schulte Step 1: Analyse the error, consider four Drive Beam sections: 1. Drive Beam accelerator 2. Compressor chicane 3. Recombination scheme 4. PETS & Main Linac Step 2: Correct the error with a feed-forward system CLIC Drive Beam Phase Stabilisation 02/08/2013 15
Feed-forward corrector chicane Feed-forward corrector chicane Plot: D. Schulte, P. Skowroński • Measure the longitudinal phase error before the turnaround • Send the signal to the chicane before the beam arrives • Chicane changes path length of the beam One can modify longitudinal position of the bunches CLIC Drive Beam Phase Stabilisation 02/08/2013 16
Feed-forward amplifier rise time Feed-forward amplifier rise time 240ns 50ns 20ns 10ns 5ns Lower amplifier rise time (= higher bandwidth) allows more efficient correction CLIC Drive Beam Phase Stabilisation 02/08/2013 17
Feed-forward for Feed-forward for different types of noise different types of noise Reduction of phase error amplitude 20 MHz 2 A a ( f ) P ( f ) df 50 Hz Improvement of phase tolerances 1 t A CLIC Drive Beam Phase Stabilisation 02/08/2013 18
Synchronisation requirements Synchronisation requirements along CLIC along CLIC 1% luminosity loss at CLIC would result from: 0.2 deg @ 12 GHz error in the relative Drive Beam - Main Beam phase 0.6 deg @ 12 GHz error between the two Main Beams phases at the IP The signal of the nominal phase must be distributed along almost 50 km long CLIC collider CLIC Drive Beam Phase Stabilisation 02/08/2013 19
Time synchronisation along CLIC Time synchronisation along CLIC Phase signal distribution - two approaches: A). Drive Beams alignment B). Master clock near the IP on the outgoing Main Beams. defines the nominal phase. Advantage: Advantage: Better alignment No distribution between the two system noise. Main Beams. ΔL < 1% requires σ step < 3.34 μm ΔL < 0.1% requires σ step < 1.06 μm Plot: D. Schulte CLIC Drive Beam Phase Stabilisation 02/08/2013 20
Summary of the CLIC Drive Beam Summary of the CLIC Drive Beam stabilisation studies stabilisation studies • To achieve the required beam spot size of the Main Beam, the Drive Beam must be stabilised to a high degree • Stabilisation of the longitudinal phase can be performed via Error filtering by recombination scheme for high frequencies Peaks at n x 4.17 MHz remain unfiltered Low frequencies remain unfiltered Feed-forward system with a chicane and a high bandwidth amplifier for lower frequencies Required improvement of RMS error by factor 12 is possible with 17.5 MHz amplifier Distributed timing system can be implemented, stability specification would be 1.06 μm average error per decelerator segment CLIC Drive Beam Phase Stabilisation 02/08/2013 21
Phase stability measurement and simulations for CTF3 CLIC Drive Beam Phase Stabilisation 02/08/2013 22
CTF3 phase measurements CTF3 phase measurements Position of phase monitors Position of phase monitors CLIC Drive Beam Phase Stabilisation 02/08/2013 23
CTF3 phase measurements CTF3 phase measurements average pulse phase average pulse phase 50 40 30 6 CR 20 4 10 STD = 6.31 2 CL290 0 deg@12GHz 0 13 37 61 85 109 133 157 181 205 229 253 277 301 325 349 373 13 37 61 85 109 133 157 181 205 229 253 277 301 325 349 373 STD = 1.45 1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 -2 1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 25 -4 deg@12GHz 20 -6 15 CC 10 1.5 5 STD = 5.25 1 0 0.5 deg@12GHz 13 37 61 85 109 133 157 181 205 229 253 277 301 325 349 373 -5 0 1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 CL475 13 37 61 85 109 133 157 181 205 229 253 277 301 325 349 373 -10 -0.5 1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 0 -1 STD = 0.52 13 37 61 85 109 133 157 181 205 229 253 277 301 325 349 373 -10 -1.5 1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 -20 deg@12GHz -2 -30 CE03 -40 5 STD = 5.0 -50 0 -60 deg@12GHz -5 13 37 61 85 109 133 157 181 205 229 253 277 301 325 349 373 -70 1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 -10 CT -80 0 -15 -20 13 37 61 85 109 133 157 181 205 229 253 277 301 325 349 373 STD = 6.77 -10 1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 -25 deg@12GHz -30 -20 CE17 -35 -30 -40 STD = 4.9 -40 deg@12GHz -50 -60 CLIC Drive Beam Phase Stabilisation 02/08/2013 24 Measurement: E. Ikarios
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