max cornacchia, slac lcls project overview besac, feb. 26-27, 2001 lcls project overview what is the...

Max Cornacchia, SLAC

LCLS Project Overview

BESAC, Feb. 26-27, 2001


• What is the LCLS ?• Transition from 3rd generation light sources to x-

ray free-electron lasers• The SASE principle and linac-driven free-electron

lasers• Performance• Accomplishments• R&D and construction plan



BESAC, Feb. 26-27, 2001

• Single pass Free-Electron Lasers• Uses SLAC Linac• 1.5 - 15 Å (0.5-5 Å in 3rd harmonic)• Peak brightness 10 orders of magnitude above Advanced

Photon Source (APS)• Time averaged brightness 2-4 orders of magnitude above APS• Sub-picosecond pulses• Fully transversely coherent radiation• Design and R&D studies, a ANL-BNL-LANL-LLNL-SLAC-UCLA

collaboration

The X-ray FEL is a powerful tool to explore matter and fundamental physics.

What is the LCLS ?



BESAC, Feb. 26-27, 2001

The transition from 3rd generation light sources to x-ray free-electron lasers

3rd generation X-ray FELs

High flux and brightness Many order of magnitude higher than in 3rd generation sources

Short pulses (tens of ps)

1-2 order of magnitude shorter (sub-ps)

Partially transversely coherent Fully transversely coherent (Degeneracy factor 109)

Bandwidth = 1/number of undulator periods

FELs



BESAC, Feb. 26-27, 2001

The SASE principle and linac-driven free-electron lasers

• Main components of a SASE FEL

– A bright electron source (photo-injector)

– A bunch compression system

– A linear accelerator– An undulator– The photon beamlines– The experimental areas

21

2

2

2

Kw

4



BESAC, Feb. 26-27, 2001

LCLS layout



BESAC, Feb. 26-27, 2001

SASE FEL theory well developed

and verified by simulations and experiments•FEL radiation starts from noise in spontaneous radiation

•Transverse radiation electric field modulates the energy and bunches the electrons within an optical wavelength

•Exponential build-up of radiation along undulator length

SASE FELs

Undulator RegimeUndulator Regime

Exponential Gain Regime

Exponential Gain Regime

Saturation

Saturation

0.2 fs

0.9 fs

1 % of X-Ray Pulse1 % of X-Ray Pulse

Electron BunchMicro-Bunching

Electron BunchMicro-Bunching



BESAC, Feb. 26-27, 2001

• Wavelength 1.5 Å

(range 1.5-15 Å, 1st harm)

• Electron energy 14.35 GeV (range 14.35-4.54)

• Bunch length 230 fsec (full)

• 1012 coherent photons/pulse

• Undulator length 120 m

• Undulator gap 6 mm

• Saturation peak power

9 GW• Peak brightness

1.2 1033

• Average brightness

4.2 1022

Main parameters



BESAC, Feb. 26-27, 2001

Light source performance chart

Peak and time

averaged

brightness

of the LCLS and other

facilities,

operating or

planned

Average Peak



BESAC, Feb. 26-27, 2001

Other FEL based light sources are being tested, built or planned• The TESLA Test Facility (TTF) at DESY

– Lasing with gain ~3000 observed at 80-180 nm

• X-ray FEL TESLA at DESY (associated with the linear collider project)– CDR being written

• Source Development Laboratory (SDL) at BNL-NSLS– Electron beam testing

• Harmonic Generation (HGHG) experiment successful at BNL-ATF

• VISA experiment at BNL-ATF– Study the FEL radiation with beam characteristics and tolerances

close to those of the LCLS

• FELs under study in Japan, Italy, England and Germany (BESSY II)

• LEUTL at ANL-APS– First observation of saturation



BESAC, Feb. 26-27, 2001

FEL experiment

• A crucial milestone in FEL physics was reached when the LEUTL experiment measured large amplification and evidence of saturation last summer at 530 and 385 nm

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

370380

390400

410420

VLD2VLD3

VLD5VLD7

VLD9In

ten

sity [a

.u.]

Saturation

BeyondSaturation

ExponentialGain



BESAC, Feb. 26-27, 2001

6D particle tracking through LCLS accelerator6D particle tracking through LCLS accelerator

150 MeV150 MeV

250 MeV250 MeV

250 MeV250 MeV

4.54 GeV4.54 GeV

14.3 GeV14.3 GeV

Ene

rgy

devi

atio

n al

ong

elec

tron

bun

chE

nerg

y de

viat

ion

alon

g el

ectr

on b

unch

Tra

nsve

rse

cros

s se

ctio

n of

ele

ctro

n be

amT

rans

vers

e cr

oss

sect

ion

of e

lect

ron

beam



BESAC, Feb. 26-27, 2001

How to achieve a short bunch

• The simulation tool was used to optimize the electron beam in 6-dimensional phase space–Preservation of transverse electron brightness leads to shorter undulator and more relaxed tolerances–Mechanism for achieving short electron bunches (230 fs) confirmed by the simulations–Even shorter bunches can compromise transverse electron brightness

230 fs bunch length is the result of optimization in all 6 dimensions



BESAC, Feb. 26-27, 2001

X-ray optics transport simulations

0 150

GINGER output:

Tables of electric field valuesat undulator exitat different times

Time Domain

Frequency Domain

TemporalTransform

SpatialTransform

00

1.94

150-150Transverse position, microns

x 1015 wattsc m2

Power Density

0

1.94

x 1015 wattsc m2

0 6Time, femtoseconds

42

Power Density

0w0w0-400/fs

1.73

x 1017 wattsc m2

w0+400/fs

frequency

Power Density

0-10

1.73

-325 304Wavenumber, mm-1

x 1017 wattsc m2

Power Density

viewer

Viewer

Transformation to Frequency Domain

Propagationto arbitrary

z

tit Ni ..1

R, mm



BESAC, Feb. 26-27, 2001

FFTB hall for undulator and diagnostics

LCLS Undulator Hall and Experimental Area Layout

Hall A:Atomic PhysicsWarm Dense MatterX-Ray Physics

Hall B:Nanoscale DynamicsFemtochemistryBiological Imaging



BESAC, Feb. 26-27, 2001

Conceptual Design Report

• Conceptual Design Report is on schedule• First draft contributions are being reviewed• Goal is to have it ready, in draft form, by early

summer 2001



BESAC, Feb. 26-27, 2001

Summary• Substantial progress made in most areas• Experimental confirmation of the photo-injector

brightness is the most important short term goal– Program is receiving strong support from SLAC

• Integration photo-injector/FEL physics/x-ray optics to continue– Realistic x-ray FEL characteristics, tolerances, match to the

experiments

• X-ray optics to address detailed requirements of the “first experiments”

• Focus on CDR for the next 6-8 months• Preparation for Lehman Review

max cornacchia, slac lcls project overview besac, feb. 26-27, 2001 lcls project overview what is the...

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