LCLS

Linac Coherent Light SourceLinac Coherent Light SourceUpdateUpdate

John N. GalaydaJohn N. GalaydaLCLS Project ManagerLCLS Project Manager

Basic Energy Sciences Advisory Committee MeetingBasic Energy Sciences Advisory Committee Meeting2-3 August 20012-3 August 2001

LCLS

R&D progress•Gun•Bunch compression•Undulator•X-ray optics•FEL experiments

Near-term R&D goals•Determine baseline gun performance•Improve understanding of coherent synchrotron radiation effects•Sub-Picosecond Photon Source (SPPS)

LCLS

1977-1990

National Synchrotron Light Source, Brookhaven National Lab

1990-2001

Advanced Photon Source,

Argonne National Lab

LCLS

LLINACINAC C COHERENTOHERENT L LIGHTIGHT S SOURCEOURCE

I-280I-280

Sand Hill RdSand Hill Rd

LCLS

Peak and time

averaged

brightness

of the LCLS and

other facilities

operating or

under

construction

Performance Characteristics of the LCLS

~ TESLA Performance

LCLS

Electrons are bunched under the influence of the light that they radiate.The bunch dimensions are characteristic of the wavelength of the light.

Excerpted from the TESLA Technical Design Report, released March 2001

Self-Amplified Spontaneous Emission

LCLS

At entrance to the undulator Exponential gain regime Saturation(maximum bunching)

Excerpted from the TESLA Technical Design Report, released March 2001

LCLS

R&D progress – Gun

BNL Accelerator Test Facility•Measurement of 0.8 mm-mrad emittance with 0.5 nC of charge•Such high performance could make shorter LCLS pulses possible•Details to be published in NIM-A, 2001 FEL Conference Proceedings

LCLS

Charge, picocoulombs

mm

-mra

dR&D progress – Gun

SLAC gun test facility•Comparison of computed and measured emittances•Agreement is good for configurations tested thus far•Facility upgrades planned to study configurations with lower emittance

LCLS Specification

LCLS

Producing short bunches

At low energy, space charge repulsion degrades the beam properties

Accelerate the bunch, then compress it.

SLAC linac tunnel undulator hall

Linac-0L6 m

Linac-1L9 mrf 38°

Linac-2L330 mrf 43°

Linac-3L550 mrf 10°

BC-1L6 m

R56 36 mm

BC-2L24 m

R56 22 mm DL-2L66 mR56 = 0

DL-1L12 mR56 0

undulatorL120 m

7 MeVz 0.83 mm 0.2 %

150 MeVz 0.83 mm 0.10 %

250 MeVz 0.19 mm 1.8 %

4.54 GeVz 0.022 mm 0.76 %

14.35 GeVz 0.022 mm 0.02 %

...existing linac

new

RFgun

25-1a30-8c

21-1b21-1d

21-3b24-6dX

Linac-XL0.6 mrf=

LCLS

zz

zz

zz

VV = = VV00sin(sin())

zz00

zz

zz = = RR5656

Under-Under-compressioncompression

Over-Over-compressioncompression

RF AcceleratingRF AcceleratingVoltageVoltage

RF AcceleratingRF AcceleratingVoltageVoltage

Path Length-EnergyPath Length-EnergyDependent BeamlineDependent Beamline

Path Length-EnergyPath Length-EnergyDependent BeamlineDependent Beamline

LCLS

Coherent Synchrotron Radiation (CSR)Coherent Synchrotron Radiation (CSR)Coherent Synchrotron Radiation (CSR)Coherent Synchrotron Radiation (CSR)

RR

e–

Free space radiation from bunch tail at pointFree space radiation from bunch tail at point AA overtakes bunch head, a overtakes bunch head, a distancedistance ss ahead of the source, at the pointahead of the source, at the point BB which satisfies...which satisfies...

ss = arc( = arc(ABAB) – |) – |ABAB| = | = RR – 2 – 2RRsin(sin(/2) /2) RR 3 3/24/24

and forand for ss = = zz (rms bunch length) the overtaking distance is...(rms bunch length) the overtaking distance is...

LL00 | |ABAB| | (24 (24zzRR22))1/31/3, (, ( LCLSLCLS: : LL00 ~ 1 m ~ 1 m))

Free space radiation from bunch tail at pointFree space radiation from bunch tail at point AA overtakes bunch head, a overtakes bunch head, a distancedistance ss ahead of the source, at the pointahead of the source, at the point BB which satisfies...which satisfies...

ss = arc( = arc(ABAB) – |) – |ABAB| = | = RR – 2 – 2RRsin(sin(/2) /2) RR 3 3/24/24

and forand for ss = = zz (rms bunch length) the overtaking distance is...(rms bunch length) the overtaking distance is...

LL00 | |ABAB| | (24 (24zzRR22))1/31/3, (, ( LCLSLCLS: : LL00 ~ 1 m ~ 1 m))

Coherent Coherent radiation for:radiation for:rrzz

Coherent Coherent radiation for:radiation for:rrzz

rr

zz

...from Derbenev, et. al....from Derbenev, et. al.

LCLS

CSR Effects CSR Effects Bunch Energy Gradient Bunch Energy GradientCSR Effects CSR Effects Bunch Energy Gradient Bunch Energy Gradient

zz

Charge distributionCharge distribution

~CSR wakefield~CSR wakefield

HEADHEAD

TAILTAIL

(mean loss)(mean loss)

2 3 4 30.22 e Brms

z

r NLE E

R 2 3 4 30.22 e B

rmsz

r NLE E

R

zz

LCLS

CSR Effects CSR Effects Emittance Growth Emittance GrowthCSR Effects CSR Effects Emittance Growth Emittance Growth

s

Radiation in bendsRadiation in bendsRadiation in bendsRadiation in bendsEnergy loss in bends causesEnergy loss in bends causestransverse position spread aftertransverse position spread afterbends bends xx-emittance growth-emittance growth

Energy loss in bends causesEnergy loss in bends causestransverse position spread aftertransverse position spread afterbends bends xx-emittance growth-emittance growth

LCLS

R&D Progress – Coherent Synchrotron Radiation•CSR sets a lower limit on LCLS as a laser•LCLS could produce ~50 fsec pulses of spontaneous radiation•New ANL model fits latest data – is the model accurate?•LCLS bunch compression can be retuned to accommodate

ener

gyen

ergy

spre

ad

spre

ad

[%]

[%]

rms

rms

bun

ch

bun

ch

leng

th

leng

th

[ps

[ps ]]

emitt

ance

em

ittan

ce

[mm

-mra

d][m

m-m

rad]

minimum compressionminimum compression

ElegantElegantmodelmodel

Courtesy M. Borland, J. Lewellen, Courtesy M. Borland, J. Lewellen, ANLANLCourtesy M. Borland, J. Lewellen, Courtesy M. Borland, J. Lewellen, ANLANL

QQ 0.3 nC 0.3 nCM. Borland, PRST-AB v.4, 074201(2001)Borland, Braun, Doebert, Groening, & Kabel, CERN/PS 2001-027(AE)

LCLS

R&D Progress – Prototype Undulator

•Titanium strongback mounted in eccentric cam movers

•Magnet material 100% delivered

•Poles >90% delivered

•Assembly underway

LCLS

Helmholtz Coil – magnet block measurement Translation stages for undulator segment

Poletip alignment fixture Magnet block clamping fixtures

LCLS

Planned beam diagnostics in undulator include pop-in C(111) screenTo extract and observe x-ray beam, and its superposition on e-beam

LCLS

R&D Progress – Undulator diagnostics•P. Krejcik, W. K. Lee, E. Gluskin•Exposure of diamond wafer to electron beam in FFTB-•Same electric fields as in LCLS•No mechanical damage to diamond•Tests of crystal structure planned

Before After

LCLS

R&D Progress – X-ray optics

•LLNL tests of damage to silicon crystal•Exposure to high- power laser with similar energy deposition•Threshold for melting 0.16 J/cm2, as predicted in model

•Fabrication/test of refractive Fresnel lens•Made of aluminum instead of carbon•Machined with a diamond point•Measurements from SPEAR presently under analysis

LCLS

FocusingOptic

Incident BeamMonitors

Back-scatterx-ray

spectrometer

Spectrometer

Laser

Outgoing Beam

Monitor

FELBeam

100 mm thick

sample50-100 maperture

Variablebeam

attenuator

250 maperture

Imagingdetector

OpticsTank

SampleTank

WDM Shielded Room

PPS beam stops

13 m

Warm Dense Matter Experiment

LCLS

R&D Progress – FEL physics

•More complete analysis of HGHG•A. Doyuran, et al. PRL vol. 86, Issue 26, pp. 5902-5905, June 25, 2001

•LEUTL experiments ongoing•Milton, et al. Science vol. 292, Issue 5524, 2037-2041, June 15, 2001

•VISA experiment saturation•To be published in proceedings of 2001 FEL conference

Data from BNL/ANLHigh-Gain HarmonicGeneration(HGHG)Experiment

LCLS

Distance Traversed in Undulator (m)

Rad

iate

d E

ner

gy

(a.u

.)LEUTL Gain Curve @ 530 nm on March 10, 2001

107

106

105

104

103

102

101

100

0 5 10 15 20 25

October,2000

LCLS

Preliminary recent results (unpublished) from VISA showing large gain (2 106) in SASE FEL radiation and evidence of saturation at 830 nm.

Visible to Infrared SASE Amplifier

Enclosure for 4-m long VISA undulator

Enclosure for 4-m long VISA undulator

Pop-In DiagnosticsPop-In Diagnostics

Data Points taken along VISA Undulator

Data Points taken along VISA Undulator

Direction of Electron Beam

Direction of Electron Beam

Wavelength 830 nm

Wavelength 830 nm

Onset of Saturation

Onset of Saturation

VISA Pulse Energy vs. Position

Wavelength 830nmRMS Bunch Length: 900 fsAverage Charge: 170 pCPeak Current: ~200 AMeasured Projected Emittance: 1.7 mm mradEnergy Spread: 7×10-4

Gain Length 18.5 cmEquivalent Spontaneous Energy: 5 pJPeak SASE Energy: 10 JTotal Gain: 2×106

16 March 2001

BNL-LLNL-SLAC-UCLA

LCLS

Near-term R&D goals

•Gun R&D•Thorough investigation of gun operation at LCLS parameters

•Laser upgrade•Linac energy upgrade

•Experiment/model comparison at 1 mm-mrad emittance, 0.5-1 nC

•Bunch compression, coherent synchrotron radiation•Install a bunch compressor in the SLAC linac•Continue start-to-end modeling

LCLS

Bunch compression studies with SLAC linac in 2003

•Compatible with PEP-II injection•Capable of producing 80 fsec electron bunches

• Goal: first studies in 1/2003, 1 year of tests•pump/probe techniques•Accelerator physics opportunities to study wake fields

Of great importance to LCLS

Short bunches are ideal for advanced accelerator R&D; Strong SLAC support

LCLS

LCLS – X-ray Laser Physics The “sixth” experiment – Produce < 230 fsec pulses of SASE radiation

LCLS will be used to explore means of producing ultra short bunches (< 50 fs). Alternative techniques will be investigated:

Stronger compression of the electron bunch• No new hardware is required

Photon bunch compression or slicing• Principle: spread the electron and photon pulses in energy;

recombine optically or select a slice in frequency

z

Seeding the FEL with a slice of the photon pulse

•Principle: select slice in frequency, then use it to seed the FEL

LCLS

Two-Stage Chirped-Beam SASE-FEL for High Power Femtosecond X-Ray Pulse GenerationC. Schroeder*, J. Arthur^, P. Emma^, S. Reiche*, and C. Pellegrini*

^ Stanford Linear Accelerator Center*UCLA

Strong possibility for shorter-pulse operation

LCLS

Two-stage Two-stage undulator for undulator for shorter pulseshorter pulse

52 m52 m43 m43 m

ee

30 m30 m

SASE gain (SASE gain (PPsatsat/10/1033)) SASE Saturation (23 GW)SASE Saturation (23 GW)

SiSi monochromator monochromator((TT = 40%) = 40%)

timetime

Ene

rgy

Ene

rgy

timetime

Ene

rgy

Ene

rgy

EEFWFW//EE = 1.0% = 1.0%

timetime

ttFWFW = 230 fsec = 230 fsec

x-ray pulsex-ray pulse

1.01.0101044

timetime

ttFWFW < 10 fsec < 10 fsecMitigates Mitigates ee energy energy jitter and jitter and undulator undulator wakeswakes

Mitigates Mitigates ee energy energy jitter and jitter and undulator undulator wakeswakes

Also a Also a DESYDESY scheme which emphasizes line-width reduction (B. Faatz) scheme which emphasizes line-width reduction (B. Faatz)

UCLUCLAA

LCLS

LCLS Construction

•FY2003: $6M for project engineering and design, $3M for R&D•Prepare bid packages

•FY2004: Start of Construction•Injector construction and installation•Bunch compressor construction•Start construction of near hall•Undulator procurement

•FY2005:•Injector commissioning•Bunch compressor installation•Start construction of far hall•Undulator, experiment construction

•FY2006: Installation•Linac commissioning•Undulator and experiment installation•LCLS commissioning

LCLS

LCLS research activities span the full range of challenges to be met in creating and exploiting an x-ray laser

SLAC has supplemented its extraordinary capabilities with the expertise and resources at partner labs to make LCLS possible

LCLS can be a reality by 2007

LCLS

End of Presentation