P. Emma LCLS FAC [email protected] 12 Oct. 2004 Comments from LCLS FAC Meeting (April 2004): J....

P. EmmaP. Emma

LCLS FACLCLS FAC [email protected]@SLAC.Stanford.edu

12 Oct. 200412 Oct. 2004

Comments from Comments from LCLSLCLS FACFAC Meeting (April 2004): Meeting (April 2004):

J. RJ. Roßoßbach:bach: “How do you detect weak FEL power when the “How do you detect weak FEL power when the gain is very low (few hundred)?”gain is very low (few hundred)?”

K. Robinson:K. Robinson: “Can you modulate the laser heater in some “Can you modulate the laser heater in some way to help FEL signal detection?”way to help FEL signal detection?”

Comments from Comments from LCLSLCLS FACFAC Meeting (April 2004): Meeting (April 2004):

J. RJ. Roßoßbach:bach: “How do you detect weak FEL power when the “How do you detect weak FEL power when the gain is very low (few hundred)?”gain is very low (few hundred)?”

K. Robinson:K. Robinson: “Can you modulate the laser heater in some “Can you modulate the laser heater in some way to help FEL signal detection?”way to help FEL signal detection?”

Laser-Heater ModulationLaser-Heater ModulationP. Emma, Z. Huang, J. WuP. Emma, Z. Huang, J. Wu

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

PP 370 kW ( 370 kW (not 10 GWnot 10 GW))

1.5-Å 1.5-Å LCLSLCLS, but , but x,yx,y 3.6 3.6 mm

GainGain 470 470

LCLS with poor gain (large emittance, jitter, M. Xie model)LCLS with poor gain (large emittance, jitter, M. Xie model)

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

modulate laser power modulate laser power (1.2 to 19 MW @ 7 Hz)(1.2 to 19 MW @ 7 Hz)

Kem Robinson idea…Kem Robinson idea…

modulated slice energy spread modulated slice energy spread (0.01% to 0.04% rms at 14 GeV)(0.01% to 0.04% rms at 14 GeV)

laser heaterlaser heater

Laser Heater at 135 MeVLaser Heater at 135 MeV

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

Simulate LCLS (Linac + M. Xie) with linac jitter, large emittance Simulate LCLS (Linac + M. Xie) with linac jitter, large emittance (3 (3 m), spontaneous radiation background, and laser-heater m), spontaneous radiation background, and laser-heater modulated at 7 Hz (or other unique frequency << 120 Hz)modulated at 7 Hz (or other unique frequency << 120 Hz)

1.5-1.5-ÅÅ LCLSLCLS, except , except x,yx,y == 3.6 3.6 mm

2% rms charge jitter2% rms charge jitter0.5 ps rms gun-timing jitter0.5 ps rms gun-timing jitter0.1-deg rms RF phase jitter (each of 4 linacs)0.1-deg rms RF phase jitter (each of 4 linacs)0.1% rms RF amplitude jitter (each of 4 linacs)0.1% rms RF amplitude jitter (each of 4 linacs)2% rms emittance jitter2% rms emittance jitterincludes small emittance growth in laser-heaterincludes small emittance growth in laser-heater10-MW spontaneous power (1% BW cut)*10-MW spontaneous power (1% BW cut)*10% rms radiation energy measurement noise10% rms radiation energy measurement noise

fast, accurate 2fast, accurate 2ndnd-order linac -order linac model in model in MatlabMatlab, with jitter, with jitter

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

Modulate Slice Energy Spread with HeaterModulate Slice Energy Spread with Heater(Square-wave suggested by Gennady Stupakov)(Square-wave suggested by Gennady Stupakov)

7 Hz7 Hz

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

Effects of Effects of linac jitter & linac jitter & modulationmodulation

bunch bunch lengthlength

energy energy spreadspread

peak peak currentcurrent

ee relative energy relative energy bunch bunch arrival arrival timetime

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

PP < < PPsatsat ::

PP > > PPsatsat ::

1-D startup power:1-D startup power:

Use ‘Use ‘Ming XieMing Xie’ model to calculate gain ’ model to calculate gain length, length, LLgg, then calculate power as:, then calculate power as:

Assume 1% BW cut to get 10-MW spontaneous powerAssume 1% BW cut to get 10-MW spontaneous power

(none)(none)

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

RedRed:: Total power + meas. noiseTotal power + meas. noiseMagentaMagenta:: Spontaneous powerSpontaneous powerGreenGreen:: FEL powerFEL power

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

x,y = 3.6 m

14.7 14.7 ± 4.1 m± 4.1 m 0.029 0.029 ± 0.013 %± 0.013 % 4.2 4.2 ± 0.6 kA± 0.6 kA

0 0 ± 0.088 %± 0.088 % 1.0 1.0 ± 0.02 nC± 0.02 nC 21 21 ± 3.0 ± 3.0 mm

LLgg 13-29 m 13-29 m

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

7 Hz7 Hz

FFT of total power + noiseFFT of total power + noise

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

EEnhanced nhanced SSelf-elf-AAmplified mplified SSpontaneous pontaneous EEmissionmission

A. ZholentsA. Zholentsbb

P. EmmaP. Emmaaa, W. Fawley, W. Fawleybb, Z. Huang, Z. Huangaa, ,

S. ReicheS. Reichecc, G. Stupakov, G. Stupakovaa, ,

a)a) SLACSLAC, , b)b) LBNLLBNL, , c)c) UCLAUCLA

First proposed by A. Zholents (LBNL)First proposed by A. Zholents (LBNL)Submitted to PRLSubmitted to PRLLCLS study published in FEL’04 proc.LCLS study published in FEL’04 proc.

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

Only one optical cycle is shown

ESASE: “nuts and bolts”ESASE: “nuts and bolts”

Energy modulation in Energy modulation in wiggler at 4 GeV wiggler at 4 GeV

• Laser peak power ~ 10 GWLaser peak power ~ 10 GW• Wiggler with ~ 10 periodsWiggler with ~ 10 periods

BunchingBunchingAccelerationAccelerationModulationModulation

Pe

ak c

urr

ent

, P

eak

cu

rre

nt, I

/II/I00

zz / /LL

50 fs laser pulse50 fs laser pulseLL= 2 microns= 2 microns

• Electron beam after bunching Electron beam after bunching at optical wavelengthat optical wavelength

20-25 kA20-25 kA

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

TheThe output x-ray radiation from a single micro-output x-ray radiation from a single micro-bunchbunch

• Each spike is nearly temporally coherent and Fourier transform limitedEach spike is nearly temporally coherent and Fourier transform limited

• Pulses less than 100 attoseconds may be possible with 800 nm laser Pulses less than 100 attoseconds may be possible with 800 nm laser

~200 as

-200 -100 0 100 200

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

A schematic of the LCLS with ESASEA schematic of the LCLS with ESASE

SLAC linac tunnelSLAC linac tunnel research yardresearch yard

BC1BC1 BC2BC2

LTULTUDL1DL1

undulatorundulatorL L =130 m=130 m

6 MeV6 MeVz z 0.83 mm 0.83 mm

135 MeV135 MeVz z 0.83 mm 0.83 mm

250 MeV250 MeVz z 0.19 mm 0.19 mm

4.3 GeV4.3 GeVz z 0.022 mm 0.022 mm

13.6 GeV13.6 GeVz z 0.022 mm 0.022 mm

...existing linac...existing linac

Linac-0

Linac-0

rfrfgungun

Linac-1Linac-1 XX Linac-2Linac-2 Linac-3Linac-3

laserlaser

wigglerwiggler

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

Beta and dispersion functions in the LCLSBeta and dispersion functions in the LCLS3-m wiggler3-m wiggler existing buncherexisting buncher

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

Peak current, emittance and energy spread after linacPeak current, emittance and energy spread after linac

xx

yy

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

At undulator entrance: At undulator entrance: EE = 14 GeV = 14 GeV

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

FEL SimulationsFEL Simulations

GenesisGenesis

GingerGinger

laser wavelength of 0.8 or 2.2 nmlaser wavelength of 0.8 or 2.2 nm

P. EmmaP. Emma


12 Oct. 200412 Oct. 2004

SummarySummaryShorter gain length, higher power, ~same average powerShorter gain length, higher power, ~same average power

Adjustable x-ray pulse duration by changing laser pulseAdjustable x-ray pulse duration by changing laser pulse

Nearly temporally coherent and transform limited radiation Nearly temporally coherent and transform limited radiation within spike with random carrier phase between spikes - within spike with random carrier phase between spikes - solitary attosecond x-ray pulsesolitary attosecond x-ray pulse

Absolute synch. between laser pulse and x-ray pulseAbsolute synch. between laser pulse and x-ray pulse

Relaxes emittance requirementRelaxes emittance requirement

Shorter x-ray wavelengths possibleShorter x-ray wavelengths possible

Better with smaller Better with smaller (and closer und. quad spacing) (and closer und. quad spacing)

Work on impedance issues ongoing (see FEL’04 proc.)Work on impedance issues ongoing (see FEL’04 proc.)

P. Emma LCLS FAC [email protected] 12 Oct. 2004 Comments from LCLS FAC Meeting (April 2004): J....

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