CLIC Drive Beam Phase Stabilisation CLIC Drive Beam Phase - - PowerPoint PPT Presentation

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CLIC Drive Beam Phase Stabilisation CLIC Drive Beam Phase - - PowerPoint PPT Presentation

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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

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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 02/08/2013 1 CLIC Drive Beam Phase Stabilisation

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02/08/2013 2

  • CLIC overview
  • CLIC stability simulations
  • Error Tolerances
  • Analysis of error propagation
  • Stabilisation via a feed-forward
  • CTF3 measurements
  • Simulation of feed-forward

system prototype

Content Content

CLIC Drive Beam Phase Stabilisation

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SLIDE 3

Phase stability simulations for CLIC

02/08/2013 3 CLIC Drive Beam Phase Stabilisation

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02/08/2013 4

CLIC Layout at 3 TeV - Overview CLIC Layout at 3 TeV - Overview

“[…] Key studies will address stability and alignment, timing and phasing […]” – CLIC CDR (Executive Summary: work-packages 2012–2016)

CLIC Drive Beam Phase Stabilisation

beam size 45 x 1 nm

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02/08/2013 5

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

Drive Beam Tolerances and Error Analysis Drive Beam Tolerances and Error Analysis

CLIC Drive Beam Phase Stabilisation Plot: D. Schulte

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02/08/2013 6

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

Drive Beam Tolerances and Error Analysis Drive Beam Tolerances and Error Analysis

CLIC Drive Beam Phase Stabilisation Plot: D. Schulte

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02/08/2013 7

Error propagation analysis Simulation tool Error propagation analysis Simulation tool

CLIC Drive Beam Phase Stabilisation

Simplified process diagram of

  • peration of Drive Beam error

tracking simulation tool.

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02/08/2013 8

Analysing the errors (1/4) Drive Beam accelerator Analysing the errors (1/4) 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

  • 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

RF potential (V) Wake potential (V)

RF potential Wake potential

CLIC Drive Beam Phase Stabilisation Simulations: R. Wegner

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02/08/2013 9

Best stability is provided by chicane with R56= -0.1m

Analysing the errors (2/4) Compressor chicane Analysing the errors (2/4) Compressor chicane

CLIC Drive Beam Phase Stabilisation Simulations: A. Aksoy

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SLIDE 10

02/08/2013 10 CLIC Drive Beam Phase Stabilisation

Analysing the errors (3/4) Recombination scheme Analysing the errors (3/4) 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

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SLIDE 11

02/08/2013 11

Analysing the errors (3/4) Recombination scheme Analysing the errors (3/4) 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

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SLIDE 12

02/08/2013 12 CLIC Drive Beam Phase Stabilisation

Analysing the errors (4/4) Main Beam acceleration Analysing the errors (4/4) Main Beam acceleration

Analyze the impact

  • f the Drive Beam errors
  • n the Main Beam energy
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02/08/2013 13

Analysing the errors (4/4) Main Beam acceleration Analysing the errors (4/4) Main Beam acceleration

  • Interval 11.7 GHz – 12.3 GHz
  • Calculate in frequency domain, then fft

CLIC Drive Beam Phase Stabilisation Simulations: O. Kononenko

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02/08/2013 14

  • Strong filtering by the in combination scheme
  • Peaks from errors resonant with 240 ns long trains
  • Suppression of peaks by drive beam accelerating

structures

  • Suppression of high frequencies by convoluting the signal

with main beam accelerating structure RF filling

Analysing the errors Phase error as function of frequency Analysing the errors Phase error as function of frequency

When trains recombine, their errors overlap

CLIC Drive Beam Phase Stabilisation

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02/08/2013 15

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

Drive Beam Tolerances and Error Analysis Drive Beam Tolerances and Error Analysis

CLIC Drive Beam Phase Stabilisation Plot: D. Schulte

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02/08/2013 16

Feed-forward corrector chicane Feed-forward corrector chicane

  • 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 Plot: D. Schulte, P. Skowroński

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02/08/2013 17

240ns 20ns 10ns 5ns 50ns

Feed-forward amplifier rise time Feed-forward amplifier rise time

Lower amplifier rise time (= higher bandwidth) allows more efficient correction

CLIC Drive Beam Phase Stabilisation

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02/08/2013 18

Feed-forward for different types of noise Feed-forward for different types of noise

MHz Hz

df f P f a A

20 50 2

) ( ) (

CLIC Drive Beam Phase Stabilisation

A t 1 

Reduction of phase error amplitude Improvement of phase tolerances

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SLIDE 19

02/08/2013 19 CLIC Drive Beam Phase Stabilisation

Synchronisation requirements along CLIC Synchronisation requirements 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

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SLIDE 20

Time synchronisation along CLIC Time synchronisation along CLIC

02/08/2013 20 CLIC Drive Beam Phase Stabilisation

Phase signal distribution - two approaches: A). Drive Beams alignment B). Master clock near the IP

  • n the outgoing Main Beams.

defines the nominal phase.

Advantage: No distribution system noise. Advantage: Better alignment between the two Main Beams. ΔL < 1% requires σstep < 3.34 μm ΔL < 0.1% requires σstep < 1.06 μm

Plot: D. Schulte

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Summary of the CLIC Drive Beam stabilisation studies Summary of the CLIC Drive Beam stabilisation studies

02/08/2013 21 CLIC Drive Beam Phase Stabilisation

  • 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

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Phase stability measurement and simulations for CTF3

02/08/2013 22 CLIC Drive Beam Phase Stabilisation

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23

CTF3 phase measurements Position of phase monitors CTF3 phase measurements Position of phase monitors

CLIC Drive Beam Phase Stabilisation 02/08/2013

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24

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5 1 13 25 37 49 61 73 85 97 109 121 133 145 157 169 181 193 205 217 229 241 253 265 277 289 301 313 325 337 349 361 373 10 20 30 40 50 1 13 25 37 49 61 73 85 97 109 121 133 145 157 169 181 193 205 217 229 241 253 265 277 289 301 313 325 337 349 361 373

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CC

STD = 5.25 deg@12GHz

CR

STD = 6.31 deg@12GHz

CL475

STD = 0.52 deg@12GHz

CL290

STD = 1.45 deg@12GHz

CT

STD = 6.77 deg@12GHz

CE03

STD = 5.0 deg@12GHz

CE17

STD = 4.9 deg@12GHz

CTF3 phase measurements average pulse phase CTF3 phase measurements average pulse phase

CLIC Drive Beam Phase Stabilisation 02/08/2013 Measurement: E. Ikarios

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25 CLIC Drive Beam Phase Stabilisation 02/08/2013

CTF3 phase measurements with different R56 values of the chicane CTF3 phase measurements with different R56 values of the chicane

  • Correl. = -0.23
  • Correl. = 0.21
  • Correl. = 0.73

Correl.= -0.80

  • Correl. = 0.95
  • Correl. = 1.00
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SLIDE 26

CTF3 phase measurements with different R56 values of the chicane CTF3 phase measurements with different R56 values of the chicane

Phase in deg@12 GHz

26 CLIC Drive Beam Phase Stabilisation 02/08/2013

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SLIDE 27

CTF3 phase measurements with different R56 values of the chicane CTF3 phase measurements with different R56 values of the chicane

02/08/2013

R56 = 0.0 R56 = 0.45 Monitor CL 475 Monitor CT 532

STD = 1.80 STD = 1.65 STD = 0.90 STD = 10.13

Phase (deg. At 12 GHz)

10 5

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Phase (deg. At 12 GHz)

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Phase (deg. At 12 GHz)

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Phase (deg. At 12 GHz)

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40 20

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Measurement: E. Ikarios

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Dispersive energy measurement in TL1 (BPI0608 monitor)

CTF3 measurements with R56 = 0.45 Phase change in the chicane vs. energy CTF3 measurements with R56 = 0.45 Phase change in the chicane vs. energy

28 CLIC Drive Beam Phase Stabilisation 02/08/2013

=> Large portion of additional phase error is caused by the beam energy error

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29 CLIC Drive Beam Phase Stabilisation 02/08/2013

CTF3 measurements with R56 = 0.45 Beam energy vs. beam phase in linac CTF3 measurements with R56 = 0.45 Beam energy vs. beam phase in linac

=> Energy error is partially caused by the beam phase error in the Drive Beam linac

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30 CLIC Drive Beam Phase Stabilisation 02/08/2013

CTF3 measurements with R56 = 0.45 Klystron phase CTF3 measurements with R56 = 0.45 Klystron phase

=> Phase error in the linac is partially caused by the phase error of first two klystrons Correlation of the beam phase error in linac with the phase of each individual klystron

  • Standard

deviation of klystron phase errors is comparable

  • Correlation

between any two klystrons is < 0.3

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31 CLIC Drive Beam Phase Stabilisation 02/08/2013

CTF3 measurements with R56 = 0.45 Klystron phase CTF3 measurements with R56 = 0.45 Klystron phase

Assumed chain of error transfer:

klystron phase error -> beam phase error in linac -> beam energy error -> additional beam phase error in the chicane

? ? Correlation of the additional beam phase error in the chicane and the beam energy with the phase of each individual klystron

  • Standard

deviation of klystron phase errors is comparable

  • Correlation

between any two klystrons is < 0.3

    

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SLIDE 32

32

CTF3 phase feed-forward prototype CTF3 phase feed-forward prototype

CLIC Drive Beam Phase Stabilisation 02/08/2013

Phase measurement Phase correction

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SLIDE 33

Calculate feed-forward with Where b is time of 20 ns corresponding to 50 MHz amplifier bandwidth, a is correction amplification a=0.85×σ(TL2)/ σ(TL1) = 0.5

Monitor position and feed-forward type σ in deg at 12 GHz TL1 39.48 TL2 without feed-forward 23.30 TL2 with 1-to-1 feed-forward 23.66 TL2 with 1-to-0.5 feed-forward 13.51 TL2 with 1-to-0.5 feed-forward with 17⁰ maximal correction 14.75

  

  

2 / 2 / ,

1

b n b n i mi mn ff mn

a b   



 

m n mn

n m

2

) ( 1  

Figure of merit - standard deviation of the bunch phase: with m being number of train, n being number of bunch in the train => Correction will produce a measurable effect

CLIC Drive Beam Phase Stabilisation 02/08/2013

Simulation of phase feed-forward prototype performance Simulation of phase feed-forward prototype performance

33

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02/08/2013 34

  • CLIC must be stabilised to a very high degree
  • Stabilisation of the Drive Beam phase is planned to be

performed via a feed-forward system

  • Simulations show that the proposed feed-forward system

is feasible

  • Amplifier must have a bandwidth > 17.5 MHz
  • Distribution system error must be < 1.06 μm per decelerator
  • CTF3 phase error after the stretching chicane is caused

by

  • the beam phase error in the linac and
  • the klystron phase error
  • Feed-forward system prototype with will produce a

measurable effect at CTF3 and will be tested in 2013. Specifications:

  • 50 MHz amplifier bandwidth
  • 17⁰ at 12 GHz maximal correction

Summary Summary

CLIC Drive Beam Phase Stabilisation

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SLIDE 35

02/08/2013 35 CLIC Drive Beam Phase Stabilisation

Questions? Questions? Thank you very much for your attention! Thank you very much for your attention!

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02/08/2013 36 CLIC Drive Beam Phase Stabilisation

Backup Slides Backup Slides

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02/08/2013 37

Analysing the errors: Combiner Ring 1 Analysing the errors: Combiner Ring 1

Phase Stability of CLIC Drive Beam