clic and high gradient fel design d. schulte for the clic collaboration and fel friends d. schulte,...

D. Schulte, LSUM, Ankara, October 20131

CLIC and High Gradient FEL Design

D. Schulte for the CLIC collaboration and FEL friends

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What is the Connection to FELs?

• CERN does not do light sources– It is not part of CERN’s mandate

• But use of X-band in FELs in other labs would help CLIC for a number of tasks– Further technical developments with industry

• Will create the industrial basis

– Performance studies of accelerator parts and systems• From components up to large scale main linac system test

• We think that FELs can profit from X-band technology– For you to judge based on further studies

• Need to find one/several laboratories to build an FEL and help them as needed (including RF, instrumentation, alignment, beam dynamics, test stands, industrial contacts …)– This is why we do this



FEL Overview

Looked a bit into a linac design for a typical Angstrøm FELWe do not know the real user needs

Swiss FEL (C-band, approved): E=5.8GeV Q=200pC σz=7μm ε≈200nm-500nm

Proposal of Ch. Adolphsen et al. shows concept for X-band E=6GeV Q=250pC σz=8μm ε≈400nm-500nm

As example we did chose E=6GeV, Q=250pC, σz=8μm, ε≈400nmDo not study injector (use the one from PSI for now) or undulator

A. Aksoy


Longitudinal Dynamics

A. LatinaE [MeV] E [MeV] E [GeV]

Example structure: a/λ=0.14 and G=67.5MV/mσz = 7.96 μm, σE = 0.0071%, σE,slice = 0.0027%(Swiss FEL: σz=7μm, σE,slice = 0.006%)Looks promising but detailed studies needed• realistic figure of merit for final beam distribution• radiation in compressors• operational margins•…

Transverse Dynamics

Stability of beam with initial jitterrequires to stay above red line


(Strong) CLIC lattice and simplified wakefield

Emittance growth with 100um tolerances:We need dispersion free steering orCLIC-style alignment for FEL

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Example SASE FEL CalculationParameter Unit ValueBeam Energy 5 GeVPeak current 8 kAEmittance 1 µmrad

Energy Spread 0.1 %Undulator strength 1.2 #

Undulator period 2 cm

Resonant λFEL 2.5 ÅPole number 200 #No of Undulator 11 #

Lattice type FODO #FEL parameter (ρ) 8.5x10-4 #Lsat 1D ~25 m

Saturation Power 4 GWPulse Length ~10 fsPeak Brightness ~1032 #photons.m

m2 mrad2.s

/0.1% BW

A. Aksoy

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Cost MinimisationBased on simple cost model

Uses CLIC structure database (K. Sjobak, A. Grudiev)

Beam dynamics constraints included

Many solutions at almost the same costCan chose most reasonable parameter set

Need to refine cost model design constraints

Preliminary



~11 m, 16.3 cm

2x ScandiNova solid state modulators

50 MW1.5 s(Operated@45MW)

2x CPI klystrons

100 (90) MW1.5 s

468 MW(418 MW)150 ns

10 m, 7.5 active

x 10 accelerating [email protected]/m (65MV/m)46.8MV (41.8MW) input power

Electron linac RF unit layout based on the existing (industrialized) RF sources (klystron and modulator)

TE01 900 bend

TE01 transfer line (RF=0.9)

Inline RF distribution network

Common vacuum network

410 kV, 1.6 s flat top

X 5.2

This unit should provide ~516 (488) MeV acceleration beam loading.Need 12 (12) RF units.Cost 51.7 a.u., 4% more than optimum

I. Syratchev,modified by me

Preliminary


Examples for Basic Parameters

unit CLIC_502 Opt. Swiss

Structures per RF unit 12 16 10 4

Klystrons per RF unit 2 2 2 1

Structure length m 0.23 0.23 0.75 1.98

<a>/lambda 0.145 0.145 0.125

Allowed gradient MV/m 100 80+

Operating gradient MV/m 77 67.5 65 27.5

Energy gain per RF unit MV 213 248 488 203

RF units needed 27 23 12 26

Total klystrons 54 46 24 26

Linac active length m 74 85 88 206

Cost estimate a.u. 76.2 71.5 51.7

Preliminary


FEL Interest• Had a meeting of several institutes that are interested in use of X-band for

FELs– TAC, Australian Light Source, Elettra, Shanghai, Uppsala , (CERN)

• Agreed to join forces to coordinated R&D and exploit synergy– Between CLIC and FELs– Between different FEL projects

• Started common discussion groups to report in February

• TAC and Australia want to go for new FEL– Similar timescales but TAC more advanced

• Elettra and Shanghai want to use X-band for upgrades• Uppsala wants to explore

• Other institutes expressed interest in a longer timescale– E.g. PSI, Norway


Timescale• Prepare a CDR (O(12months))

– To establish a project with an attractive scope and good, robust design and reasonable funding prospects

– To propose and justify R&D phase toward a TDR and project proposal– Mainly theoretical work based on existing hardware experience and simulations– This work will profit from close collaboration between different FEL proponents and

CLIC– One can imagine a “modular CDR”, where parts are shared

• Prepare a project proposal/TDR (O(4 years))– This will require hardware developments

• E.g. an RF unit

– There may be high potential for synergy between different FEL projects as well as CLIC in this phase

• FEL construction– Also at this stage collaboration appears beneficial

• The level of mutual benefits will evolve with the designs


CDR Activities• Defining the goals and main parameters of the FELs

– User needs– Beam time structure– Other beam parameters

• Putting together an integrated model to evidence beam performance– Sources– Linacs– Photon lines

• Defining the RF design– Pulse compressors– Structures– Klystrons– …

• Other components could maybe treated in less detail• Cost estimate and site study• Definition of the R&D for the TDR

– Coordinated with other projects


Options• Baseline: Single bunch with 50Hz

• Option 1a: Single bunch with 500Hz• Option 1b: Few bunches with 50Hz– With space to separate them into different photon lines

• Option 2: Few bunches with 500Hz– As above

• Option 3: Full CLIC bunch train at 50Hz– Can the experiments survive this?

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Conclusion• X-band seems a good technology for an X-FEL

– Simplistic example study with CLIC structure and RF design and soon available commercial klystrons already promises good performance and cost

– Your FEL project might profit from X-band

• CLIC would profit from fostering the use of X-band technology– We are looking for collaborations on X-band FELs

• Would need to define the scope that users like– Number of bunches– Repetition rate– Other beam parameters

• Based on this one can define a CDR design– Also cost will need to be considered D. Schulte, LSUM, Ankara, October 2013


Reserve


Options20ms

2ms

Baseline• Single bunches at 50Hz• Cheapest option• Can either have a single user line or several

– But need to distribute pulses

• Single bunches at up to 500Hz• Can either have a single user line or several• More costly klystrons• 10 times higher power consumption• Heating issues in the structures• Injector issues

80fs


Options II

20ms

50ns

• A few bunches in a train spaced by 20-50ns (or so), trains 50Hz• Can use a kicker to distribute bunches into different beam lines

– Requires several photon lines• Linac not significantly more costly than baseline• Power consumption similar to baseline

• A few bunches in a train spaced by 0.5ns, trains 50Hz• Can use a kicker to distribute bunches into different beam lines• Requires several photon lines• More costly klystrons• 10 times higher power consumption than baseline• Heating issues in the structures• Injector issues

2ms

50ns


Options III

20ms

0.5ns

• Many bunches (e.g. 300) in a train spaced by 0.5ns, trains 50Hz• Will all go down the same photon line• Linac not significantly more costly than baseline• Power consumption similar to baseline

• Is this good for anybody?

• At which spacing could the bunches be used in the same line?

clic and high gradient fel design d. schulte for the clic collaboration and fel friends d. schulte,...

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