LCLS-II Capabilities & Overview - Stanford University · 2015. 2. 9. · LCLS-II Science Opportunities Workshop, February 9-13, 2015 LCLS-II baseline will deliver same beam parameters

LCLS-II Capabilities & Overview LCLS-II Science Opportunities Workshop

Tor Raubenheimer

February 9th, 2015

Outline

LCLS-II Science Opportunities Workshop, February 9-13, 2015

1. Overall machine goals and layout

2. Primary parameters

• Nominal X-ray wavelength and pulse energy curves

• X-ray power

• Bunch charge versus X-ray length

• Timing and energy stability

3. Simulations of performance

4. Future enhancements

Talk largely consists of slides extracted from recent LCLS-II

reviews and much more information can be found there.

2

LCLS-II Concept CW linac based on SCRF technology to complement LCLS CuRF


SCRF offers advantages in

terms of X-ray power,

stability, and repetition rate

Challenge is cost for high

energy CW accelerator and achieving comparable peak

brighness

LCLS-II will benefit from best of both CuRF and SCRF

• Use CuRF for high peak brightness at short wavelengths

• Use SCRF for very high average brightness with stable beam

and uniform bunch spacing

3

LCLS-II 1.3 GHz Cryomodule Similar to EuFEL but modified for CW operation

Total length ~12.2 m Nearly the final LCLS-II cryomodule design


Cryomodules will be similar to EuXFEL with modifications for

CW operation; cavities will be processed for high Q0 operation

Baseline 16 MV/m with Q0 = 2.7x1010

CM allows 150 Watts max cooling

20 MV/m max gradient @ 2.7x1010

or 16 MV/m @ 1.8x1010

4

LCLS-II Concept Use 1st km of SLAC linac for CW SCRF linac

5 LCLS-II Science Opportunities Workshop, February 9-13, 2015

with space for 7 GeV

Revised LCLS-II (Phase II) Baseline Deliverables

Self seeding between 1.2-4 keV

requires x-ray optics development

Self seeding at high rep rate above

4keV will require ~4.5 GeV electron

beam, not a baseline deliverable

today

Cu Self Seeded

High Rep Rate SASE

Self Seeded (Grating)

Cu SASE

Photon Energy (keV)

0 5 10 15 20 25

SC Linac High Rep Rate

Cu Linac

Legend

4.0 GeV

LCLS-II Science Opportunities Workshop, February 9-13, 2015 6

LCLS-II Accelerator Layout New Superconducting Linac LCLS Undulator Hall


• Two sources: high rate SCRF linac and 120 Hz Cu LCLS-I linac

• North and South undulators can operate simultaneously in any mode

Undulator SC Linac (up to 1 MHz) Cu Linac (up to 120Hz)

North

0.20 - 1.3 keV

South

1.0 - 5.0 keV

up to 25 keV

higher peak power pulses

• Concurrent operation of 1-5 keV and 5-25 keV is not possible

HXU

SXU Sec. 21-30 Sec. 11-20

0.2-1.3 keV (0 -1 MHz)

SCRF

4 GeV 1-25 keV (120 Hz) 1-5 keV (0 -1 MHz)

LCLS-I Linac 2.5-15 GeV

proposed FACET-II LCLS-II Linac

7

FEL X-ray Performance

LCLS-II FAC Review, February 5-6, 2015

SCRF linac can deliver ~1 MHz beam to either undulator

• Undulators limited to 120 kW electron beam power

• 100 pC at 300 kHz and 4 GeV or 33 pC at 900 kHz and 4 GeV

• Goal is to provide >20 Watts in SASE over wavelength range

of 0.2 to 5 keV to experiments with good mirror figure

- X-ray Transport is designed to handle up to 200 Watts

- Maximum X-ray pulse energy is function of X-ray wavelength,

e.g. 0.9 mJ at 200 eV; 1 mJ at 1 keV; 20 uJ at 5 keV

• Soft X-ray self-seeding will provide narrower bandwidth with

pulses a few times transform-limit

CuRF linac will deliver LCLS-like bunches and mJ-scale

SASE X-ray pulses to >25 keV

8

9

Possible Operating Modes Very flexible operation

Configuration Linac Parameters SXR HXR

High rate to SXR and

HXR

SCRF: 4 GeV, 0.929 MHz; 60 pC

CuRF: off

50-200 W at 1 keV

(120-450 uJ at 460 kHz) 20 W at 3 keV

(43 uJ at 460 kHz)


medium pulse energy

at HXR


CuRF: off

80-200 W at 250 eV

(350-900 uJ at 210 kHz) 20 W at 1.5 keV (1 mJ at 20 kHz)

Medium rate and

pulse energy at SXR

and HXR


CuRF: off

20 W at 500 eV

(1 mJ at 20 kHz) 20 W at 4 keV

(0.4 mJ at 50 kHz)


high pulse energy at

HXR


CuRF: 15 GeV, 120 Hz, 130 pC

200 W at 250 eV

(500 uJ at 400 kHz) 0.5 W at 3 keV

(4 mJ at 120 Hz)


short wavelength at

HXR


CuRF: 15 GeV, 120 Hz, 130 pC

50 - 200 W at 1.2 keV

(50-200 uJ at 920 kHz) 0.1 W at 25 keV

(500 uJ at 120 Hz)


CuRF Linac Driven X-ray Pulse Energy

LCLS-II Science Opportunities Workshop, February 9-13, 2015 H-D Nuhn 10

X-ray Pulse Energy from SXR and HXR driven by SCRF Analytic estimates vs. simulation results

LCLS-II Science Opportunities Workshop, February 9-13, 2015 G. Marcus

SC linac + SXR 100 pC, ~50 fs FWHM

300 kHz, 4 GeV SC linac + HXR

100 pC, ~50 fs FWHM

300 kHz, 4 GeV

SXR 3w (approximate)

HXR 3w (approximate)

103 104

10-5

10-4

10-3

Photon Energy (eV)

Ener

gy/p

uls

e (J

)

102

20 pC e-beam

20 fs FWHM

11

12

Example: 100 pC IMPACT, HXR SASE, Eγ = 2 keV

0 20 40 60 80 100 120 14010

-4

10-2

100

102

104

2 keV, energy [J]

z [m]

E [

J]

0 10 20 30 40 50 60 700

10

20

30

40

s [m]

P [

GW

]

0 10 20 30 40 50 60 700

1

2

3

4

I [k

A]Emax ~ 655 μJ

Pavg ~ 10 GW

Δt = 58 fs

Example: 20 pC IMPACT, HXR SASE, Eγ = 5 keV


0 50 100 15010

-4

10-3

10-2

10-1

100

101

102

z [m]

E [

J]

No taper

Taper

0 5 10 15 200

0.5

1

1.5

2

s [m]

P [

GW

]

0 5 10 15 200

0.2

0.4

0.6

0.8

I [k

A]

4975 4980 4985 4990 4995 50000

2

4

6

8

10

12x 10

11

E [eV]

P(w

) [a

.u.]

ENT ~ 8 μJ

ET ~ 25 μJ

Δt ~ 18 fs

ΔEγ,FWHM ~ 2.1 eV

ΔEγ,FWHM/E0 ~ 4.2 x 10-4

13

Example: 100 pC IMPACT, SXR SS, Eγ = 500 eV,


0 20 40 60 8010

-4

10-2

100

102

z [m]

E [

J]

E ~ 113 μJ after 9

downstream undulator

sections

0 10 20 30 40 50 600

2

4

6

8

10

s [m]

P [

GW

]

Δtmean ~ 20 fs

490 495 500 5050

1

2

3

4

5

6x 10

12

E [eV]

#/

eV

ΔEγ,FWHM ~ 0.22 eV

ΔEγ,FWHM/E0 ~ 4.4 x 10-4

14

5 more undulator segments for

post-saturation taper if desired

Working to

understand

pedestal

Bunch Charge and Pulse Length Charge and rate determined by 120 kW limit


LCLS-II baseline will deliver same beam parameters to both

undulators

- Specified to operate with 10 – 300 pC bunch charge @ <120 kW

- 100 pC with 60 fs FWHM; 20 pC with 20 fs FWHM

Baseline is 100 pC per bunch with roughly 60 fs FWHM X-ray

pulse length (1 kA) at 300 kHz (120 kW)

- Working on techniques to shorten X-ray pulse without changing

charge or chirp etc – how rapidly are changes desired?

- Pulse energy simply proportional to pulse length

Low charge options include 10 and 20 pC at up to 929 kHz

- Better performance (pulse energy/bunch charge)

15

Nonlinear Harmonic Generation and Harmonic Lasing


• Nonlinear harmonic generation produces third harmonic

radiation at ~1% of the fundamental when K>1.5

• Harmonic lasing can produce significant radiation with a

narrow spectrum when the fundamental is suppressed

- Investigating options for harmonic lasing

- Should be reasonable to upgrade HXR undulator if needed

Fundamental 2 keV 3 keV

Bunch charge 100 pC 20 pC

3rd harmonic 6 keV 9 keV

Efficiency 1% 0.75%

Energy/pulse 1 uJ 0.14 uJ

16

Stability Goals


• LCLS-II SCRF FEL will be more stable than LCLS

• Baseline specs for electron beam:

- DE/E < 0.01% rms

- DI/I < 4% rms

- Dt < 20 fs rms

- DX/sX, DY/sY < 15% rms

• LLRF has been specified to provide stability in ‘worst’ case

of correlated errors

• X-ray pulse has added intensity jitter from SASE and optics

• MHz beam rate should allow further stabilization with

addition of fast feedback systems

17

Longer-Term Goals Can Provide Exceptional Stability


ENERGY

PEAK

CURRENT

ARRIVAL

TIME

Now simulate the best case:

0.01% and 0.01 deg rms jitter

and all uncorrelated Energy stable to 0.003% rms

Peak current stable to 1.8%

Timing stable to 5 fs

* The gun timing error is compressed by 3.85 from gun to 100 MeV, due

to velocity compression.

Best Case Jitter Simulations in LiTrack

See PRD: LCLSII-2.4-PR-0041

P. Emma 18

Parameter Range for: Timing

Parameter Name

(Unit)

Ready for First

Light

Possible within

the first year or

two of operation

It could happen –

don’t laugh

Short term laser

vs X-ray jitter

<100 fs RMS* <50 fs RMS

10 fs RMS

probably the limit

X-ray vs laser 1-

day drift

1 ps 100 fs 10 fs with pulsed

fiber locking

X-ray / optical

cross correlator**

Probably not

ready

10-50 fs 10 fs

LCLS_I to

LCLS_II jitter

200 fs RMS 100 fs RMS 100 fs RMS

*Assuming full performance LLRF system for the accelerator

** if applicable for beam operating conditions

J. Frisch, July 31, LCLS-II Parameters Review


LCLS-II Planned Undulator Layout Replace Existing LCLS Undulator with HXR and add SXR

32 HXU Segments

Existing Diamond Crystal

Self-Seeding System

New SXR Self-Seeding

System for High Power Loads

21 SXU Segments

Space for future upgrades? Space for polarization

upgrade?

Considering vertical polarization of X-rays from HXR line


Enhanced Modes of operation (G. Marcus, July 31, LCLS-II Parameters Review)

• High rep-rate HXR SS

• External seeding

• HGHG

• EEHG

• ?SASE

• iSASE

• pSASE

• Harmonic Lasing

• Two-Color

• Split undulator and gain modulation

• Two-bunches

• FWM via selective amplification

• Short pulses

• low charge, beam spoiling, laser modulation, self-seeding / chirp

• Timing control

• Defined by laser

• Easy to adjust pulse duration

• Improved stability in photon energy and #

• Possibly near transform limited pulses

• Increase cooperation length

• Narrow spectrum

• Extend tuning range of FEL beamline

• X-ray pump & probe

• Four-wave mixing


Option for complete HXR self-seeding monochromator Possible layout options not fully explored

• Two-stage diamond wake-field monochromator seeding sections and a grating

monochromator seeding section

• Seeding below 3 keV • Both diamond systems are retracted

• Seeding above 3 keV • Grating system is retracted

• Between 3 – 5 keV • Both diamond monochromators in use using (111) crystals

• Above 5 keV with CuRF linac • Only 2nd diamond mono. in use with (400) crystal


Summary


• Broad capability

- High rate beam from 0.20 – 5 keV with >20 W X-ray power

- High intensity pulses with LCLS charactistics to >25 keV

• SCRF linac will provide >10x better stability than CuRF

- How best to take advantage of benefits?

- What else is needed?

• Variable gap udulators allow flexible operation

- Broad bandwidth coverage; Strong tapering; Rapid wavelength scans

• Broad spectrum of upgrade options

- LCLS is pioneering many techniques that may be implemented in LCLS-II

• Please suggest your X-ray goals

- Opportunity to modify development plans but need strong science case

23

BACKUP


Must Use Gas Based Techniques for SXR

• Design concept similar to LCLS-I gas attenuator, but

- Using Ar gas, 5 m long volume, up to 10 torr

- Differential pumping w/ 1st variable (impedance) apertures to reduce

conductance (beam size ~ 10 mm at 200 eV at location)


Impact of Intensity Fluctuations on Gas Attenuator Beam drills hole through gas

Intensity fluctuation induced inaccuracy in attenuation ~ 10%

T (

K)

Att

n A

ch

ieve

d

Intensity fluctuation induced baseline temperature variation ~ 200 °K

Operating pressure ~ 2.5 torr, effective attenuation 5x10-4 ~ absorbed 200 W into gas detector

Y. Feng LCLS-II Science Opportunities Workshop, February 9-13, 2015

LCLS-II (SCRF) Baseline Parameters

Parameter symbol nominal range units

Electron Energy Ef 4.0 2.0 - 4.14 GeV

Bunch Charge Qb 100 10 - 300 pC

Bunch Repetition Rate in Linac fb 0.62 0 - 0.93 MHz

Average e- current in linac Iavg 0.062 0.0 - 0.3 mA

Avg. e- beam power at linac end Pav 0.25 0 - 1.2 MW

Norm. rms slice emittance at undulator e-s 0.45 0.2 - 0.7 m

Final peak current (at undulator) Ipk 1000 500 - 1500 A

Final slice E-spread (rms, w/heater) sEs 500 125 - 1500 keV

Final bunch length (rms) tb 8.5 3 - 50 m

Avg. CW RF gradient (powered cavities) Eacc 16 - MV/m

Photon pulse length (FWHM) txray 70 10 - 350 fs

Photon energy range of SXR (SCRF) Ephot - 0.2 - 1.3 keV

Photon energy range of HXR (SCRF) Ephot - 1 - 5 keV

Photon energy range of HXR (Cu-RF) Ephot - 1 - 25 keV

See LCLSII-1.1-PR-0133

External seeding modes

UV

seeds

radiator mod1

mod2

UV

seed

fresh

bunch

delay

mod1 rad1 mod2 rad2

EEHG

HGHG

9 fs rms

0.22 eV rms

16 fs rms 0.12 eV rms

~ 2 x transform limit

• Allows long coherent pulses

• Highly sensitive to laser quality, less so to electron bunch

• Highly sensitive to electron

bunch parameters

• Consistently poor spectrum

• QHG (with reviewers) relax

conditions on harmonic jumps


External seeding performance and requirements


• EEHG

• Performance

- Long, coherent pulses

- Near Fourier transform limit (~ 2x FTL @ 1nm)

• Requirements

- Stable (amplitude and phase) laser @ 260 nm

- 2 chicanes and 2 modulators

• HGHG

• Performance

- Best for short pulses

- Hard to control spectrum

- Below 2 nm is pushing limits

• Requirements

- 3 chicanes (one for fresh bunch), 2 modulators, intermediate radiator

- 260 nm laser

Harmonic lasing using 100 pC, 1 kA e-beam slice

properties

0 50 100 15010

2

104

106

108

1010

z [m]

P [

W]

Ideal beam comparison

5 keV @ fund.

5 keV @ 3rd

harm.

Additional phase shifters needed

0 50 100 15010

2

103

104

105

106

107

108

z [m]

P [

W]

7 keV

6-7 keV photons become possible

with attenuators

• Tune first undulators such that 3rd

harmonic at desired wavelength

• Tune second undulators such that 5th

harmonic is at desired wavelength and

equal to 3rd upstream

0 20 40 60 80 100 12010

0

102

104

106

108

1010

z [m]

P [

W]

E,f

~ 4.1 keV

1.38 keV

4.1 keV

0.83 keV

2.5 keV

4.1 keV

Pavg ~ 200 MW

HXR

SXR


Two-color generation: Some recent LCLS results

• Split undulator scheme

• Gain modulation

l1,2 = lw1+K1,2

2

2g 2


Two-color generation: Two-bunch xFEL demonstrated

at LCLS

Photocathode Laser Pulse

Adjustable delay stage

Double Pulse

Electron Gun

Linac

Few ps delay

Bunch Compressor 1

Bunch Compressor 2

Few fs delay

~1% energy separation

UNDULATOR

time time

Energ

y

Energ

y

2-color

X-Rays

Splitter

l1,2 = lw1+K 2

2g 2

1,2


FEL for FWM


• Control of

• Timing

• Color

• Angle of incidence

• Large bandwidth, coherent short (~1-2

fs) pulses

• Can be further compressed (~0.5

fs)

• Many additional components and

significant R&D required

• Easily fits in SXR tunnel

Ferrite Loaded Transmission Line Kicker Hardware testing has begun

• Loaded sections of ferrite and discrete capacitors

simulate a transmission line.

• 𝑓𝑖𝑙𝑙 𝑡𝑖𝑚𝑒 =𝐿𝑡𝑜𝑡𝑎𝑙×𝐼

𝑉 where we will have 3

separate kickers for 1/3 fill time ~100ns.

Recent measurements (7 out of 23)

Individual magnets

Integrated kick

T. Beukers

Test Pulser Schematic of 1m kicker


Two-color performance and requirements


• Split undulator/gain modulation

• Performance - Peak power 5-10 x lower for both colors

- Different source points

- Only up to ~ 2.5 keV on HXR due to long saturation lengths

• Requirements - Chicane (SXR)

• Two bunch

• Performance - Both colors achieve saturation

- Smaller photon tunability due to chromatic effects in transport, on order of 1-2%

• Requirements - Beam splitter for photocathode laser

• FEL for FWM

• Performance - Short pulses

- Large bandwidth

- Flexibility in timing, photon energy, angle of incidence

• Requirements - Two modulators, four small chicanes, single-cycle mid IR laser, beam splitter, delay stages

Parameter Sensitivities

SXR is robust at 1.25 keV; HXR is limited at 5 keV

LCLS-II Science Opportunities Workshop, February 9-13, 2015 H-D Nuhn

Using LCLS to Benchmark IMPACT S-2-E Simulations uBI effects will be important

LCLS microbunching studies: 4GeV, 180pC, 1kA

Measured final t-p phase space vs laser heater preliminary analysis of bunching factor

D. Ratner, Y. Ding, et al. LCLS-II Science Opportunities Workshop, February 9-13, 2015

LCLS-II Layout (P. Emma, LCLS-II FAC Review)

L2-Linac L3-Linac

HXU

SXU

Sec. 21-30

LH BC1 BC2

BC3

D2

D10

-wall

0.65 m 0.93 m

2.50 m

L1

kicker LTUH

LTUS

“glowing” sections indicate these are not in the vertical plane of either linac

LCLS-I

Linac

See PRD: LCLSII-2.5-PR-0134

(plan view - not to scale) N

ew

SC

RF

Lin

ac (

4 G

eV

)

Byp

ass

Lin

e

1s

t D

og

Leg

LT

U

Tra

nsp

ort

un

du

lato

rs

Beam

Sp

read

er

LCLS-II Science Opportunities Workshop, February

9-13, 2015

Solid-State Amplifiers Simplify LLRF and offer better performance


• Installing

3.8 kW SSA

• Need 2.6 kW

with no f offset

or overhead

• Need 3.8 kW

with 10 Hz

-phonic offsets,

6% overhead for losses and 10 % tuning overhead

- Same power allows operation at ~ 50% duty with 60 uA at 23

MV/m with 3 Hz max detuning, QL = 6e7 and the same overheads

Linac

Sec.

V0

(MV)

j

(deg)

Acc.

Grad.*

(MV/m)

No.

Cryo

Mod’s

No.

Avail.

Cav’s

Spare

Cav’s

Cav’s

per

Amp.

L0 100 varies 16.3 1 8 1 1

L1 211 -12.7 13.6 2 16 1 1

HL -64.7 -150 12.5 2 16 1 1

L2 1446 -21.0 15.5 12 96 6 1

L3 2206 0 15.7 18 144 9 1

Lf 202 ±34 15.7 2 16 1 1

HXU

SXU Sec. 21-30 Sec. 11-20

0.2-1.3 keV (0.1-1 MHz)

SCRF

4 GeV 1-25 keV (120 Hz) 1-5 keV (0.1-1 MHz)

LCLS-I Linac 2.5-15 GeV

proposed FACET-II LCLS-II Linac

High Level Photon Parameters Table 2 from Bill Schlotter’s LCLS-II Introduction document


Undulator Uni

ts SXR HXR

Linac SC SC Cu

Photon Energy ke

V 0.25-1.25 1-5 >5 1-25

Max Repetition

Rate kH

z 1000 1000 .12

Max Pulse Energy mJ 1.9-1.6 2.3-1.9 2.3-0.1 0.2 4.2-1.4 10-3.3

Max Power in

FEE W 200 200 1.2-0.4

Max Power to

End Station W 20 20 0.4

FWHM Pulse

Duration fs 70 fs

@100 pC 10 fs

@10 pC 70 fs

@100 pC 10 fs

@ 10 pC 25 fs

@100 pC

Tracking a 100, 300, and 20 pC Bunch Charge (with CSR, long. wakes, and separate injector runs – ASTRA & Elegant)


Q = 100 pC ex=0.350.42 m (20%)

heater = 5.5 keV rms

jL1 = -12.7 deg

V3.9 = 64.7 MV

j3.9 = -150 deg

R56-BC2 = -37.0 mm

Q = 300 pC ex=0.610.77 m (26%)

heater = 11 keV rms

jL1 = -14.0 deg

V3.9 = 58.0 MV

j3.9 = -150 deg

R56-BC2 = -36.7 mm

Q = 20 pC ex=0.090.13 m (44%)

heater = 2.0 keV rms

jL1 = -21.0 deg

V3.9 = 55 MV

j3.9 = -165 deg

R56-BC2 = -62 mm

0.6 kA L. Wang

HXR Components


SXR Device Symbol HXR

Count Notes

Adjustable Aperture type 1 1 New Design

Adjustable Aperture type 2 (mirror Slits) 1 Similar to LUSI

Attenuators (Gas and Solid) 1 Modifications to the existing Gas attenuator

New solid attenuator Design based on LUSI

Flat Mirror 2

No upgrades to the existing HOMS mirrors

New HOMS mirrors to cover SC energy range

Gas Energy Monitor 2 Repurposed with upgrades

High Resolution Imager 3 New design based on LUSI

In line Spectrometer 1 Repurpose existing

Mono 1 Repurpose existing

Rapid Turnaround Diagnostics Station 1 Repurpose existing

Stopper 1 New design SB

SB

PH

OT

ON

BE

AM

ST

OP

PE

R

M2H

(N

)

MIR

RO

R

IMA

GE

R

HO

MS

1 (

E)

MIR

RO

R

IMA

GE

R

AD

J

AP

ER

GA

S

MO

NIT

OR

GA

S

MO

NIT

OR

AD

J

AP

ER

RA

PID

DIA

GN

OS

TIC

CH

AM

BE

R

SP

EC

TR

OM

ET

ER

UN

DU

LA

TO

R

CE

NT

ER S

HA

DO

W

WA

LL

(E

)

K-M

ON

O

SO

LID

AT

TE

N

IMA

GE

R

GA

S A

TT

EN

M1

H (

N)

MIR

RO

R

HO

MS

2 (

E)

MIR

RO

R

XR

T &

FE

H

DU

MP

WA

LL

NE

H W

AL

L

TH

ER

MA

L B

AR

RIE

R

WA

LL

DU

MP

AR

EA

FE

E

AR

EA

NE

H

AR

EA

FE

E W

AL

L

HU

TC

H 1

AR

EA

Beam Direction

SXR Components


SXR Device Symbol SXR count Notes

Adjustable Aperture type 1 1 New Design

Adjustable Aperture type 2 (mirror Slits) 1 Similar to LUSI

Attenuator (Gas) 1 New Gas attenuator, design similar to LCLS-I

Flat Mirror 2 New System: very low figure error, water cooled

Gas Energy Monitors 2 One repurposed system with upgrades, one new

system with similar design to LCLS-I system

High Resolution Imager 4 New System, design borrows elements from LUSI

K-B mirrors 1 New System: Bender design leveraged on CXI

system

Rapid Turnaround Diagnostics Station 1 New System, use LCLS-I design

Stopper 1 New Design SB

SBA

DJ

AP

ER

TU

RE

1G

AS

AT

TE

NU

AT

OR

RA

PID

DIA

GN

OS

TIC

IMA

GE

R

AD

J

AP

ER

TU

RE

2

IMA

GE

R

M1S

1 M

IRR

OR

SH

IELD

ING

WA

LL

M2S

1 M

IRR

OR

DU

MP

AR

EA

FE

E A

RE

A

BE

AM

ST

OP

PE

R

GA

S E

NE

RG

Y M

ON

ITO

R

IMA

GE

R AR

RIV

AL

TIM

E

WA

VE

FR

ON

T

GA

S M

ON

ITO

R

CE

NT

ER

UN

DU

LAT

OR

DU

MP

WA

LL

IMA

GE

R

FE

E W

ALL

KB

M1

HO

RIZ

ON

TA

L

KB

MIR

RO

R

EN

D S

TA

TIO

N 1

KB

M1-

VE

RT

ICA

L

KB

MIR

RO

R

TH

ER

MA

L W

ALL

NE

H

HU

TC

H-1

LCLS

Operations

Verify RF Stability Tolerances by Tracking (P. Emma, LCLS-II FAC Review)

* The gun timing error is compressed by 3.85 from gun to 100 MeV, due to velocity compression.

PEAK

CURRENT

(<4%)

ARRIVAL

TIME

(<20 fs)

ENERGY

(<0.01%)

Jitter Simulations in LiTrack

(DE/E0)rms =

0.008%

Dtrms =

20 fs

(DIpk/Ipk)rms =

3.8%

Now verify by tracking 1000 times with random jitter

Jitter may be correlated or uncorrelated (cav. to cav.)

Include bunch charge, gun laser, & chicane supplies

uncorrelated rms

jitter tols per cavity

if jitter is correlated

(cavity to cavity)

OK

OK

OK


200 W Requirement on Photon Beamlines Will have impact but looks achievable


• Photon beamlines have been speced to operate at 20 W

with good figure performance and 200 W

• The FEL’s can deliver >200W over much of photon range

• The 200 W requirement is to provide headroom in

operations and to allow for harmonics, …

• 200 W requirement impacts stoppers, attenuators, and

photon diagnostics

• Most issues have been resolved with small impact

• Some new challenges have been uncovered

100 pC, 1 kA: SXR SS simulation results @ Eγ = 1.24

keV – typical run


0 20 40 60 8010

-4

10-2

100

102

104

z [m]

E [

J]

Energy gain curve

E ~ 1.5 μJ

0 10 20 30 40 50 60 700

0.05

0.1

0.15

0.2Power (blue), Current (green)

s [m]

P [

GW

]

0 10 20 30 40 50 60 700

0.5

1

1.5

2

I [k

A]

1230 1235 1240 1245 12500

2

4

6

8x 10

9

E [eV]

#

/eV

[N

]

Spectrum (blue), Filter (red)

1230 1235 1240 1245 12500

0.005

0.01

0.015

0.02

E ~ 200 μJ

0 10 20 30 40 50 60 700

0.5

1

1.5

2x 10

5 Power (blue), Current (green)

s [m]

P [

W]

0 10 20 30 40 50 60 700

0.5

1

1.5

2

I [k

A]

1238 1239 1240 1241 12420

2

4

6

8

10x 10

7 Spectrum

E [eV]

#

/eV

[N

]

0 10 20 30 40 50 60 700

5

10

15

20Power (blue), Current (green)

s [m]

P [

GW

]

0 10 20 30 40 50 60 700

0.5

1

1.5

2

I [k

A]

1238 1239 1240 1241 12420

1

2

3

4

5

6x 10

12 Spectrum

E [eV]

#

/eV

[N

]

ΔEFWHM ~ 64 meV

ΔEFWHM/E0 ~ 5.1 x 10-5

TBP ~ 4.3 eV-fs = 2.4 FTL

Saturation after 16 out of

21 undulators

G. Marcus

FWHM ~ 65 fs

20 pC, 500 A: HXR SASE simulation results @ Eγ = 5.0

keV


0 20 40 60 80 100

10-4

10-2

100

102

z [m]

E [

J]

Energy gain curve

0 5 10 15 20 250

1

2

3

4

5

6

7Power (blue), Current (green)

s [m]

P [

GW

]

0 5 10 15 20 250

0.2

0.4

0.6

0.8

1

1.2

1.4

I [k

A]

5000 5005 5010 5015 5020 5025 50300

0.5

1

1.5

2

2.5

3

3.5x 10

11 Spectrum

E [eV]

P(w

) [a

.u.]

ΔEFWHM ~ 3.5 eV

ΔEFWHM/E0 ~ 7.0 x 10-4

E ~ 27.4 μJ

Saturation after 24 out of 32 undulators

G. Marcus

FWHM ~ 20 fs

100 pC IMPACT e-beam slice properties, HXR


s [m]

E [

GeV

]

0 10 20 30 40 50

3.98

3.99

4

4.01

4.02

0 10 20 30 40 50-40

-20

0

20

40

60

s [m]

- 0

0 10 20 30 40 500

1

2

3

4

5

I [k

A]

0 10 20 30 40 500

0.5

1

s [m]

e n [m

m-m

rad

]

0 10 20 30 40 500

1

2

3

4

5

I [A

]

0 10 20 30 40 500

1

2

s [m]

sE [

MeV

]

0 10 20 30 40 500

1

2

3

4

5

I [A

]

head I ~ 720 A

ϵn,x ~ 0.35 mm-mrad

ϵn,y ~ 0.42 mm-mrad σE ~ 450 keV

SXR shows larger fluctuations here,

but otherwise is comparable

SXR self-seeded geometry (LCLS)


1239 1239.5 1240 1240.5-0.2

0

0.2

E [eV]

Am

p

1239 1239.5 1240 1240.5-0.1

0

0.1

Ph

ase

• λu = 39 mm

• Lu = 3.4 (87 per.)

• Lbr = 1.0 (25 per.)

• 7 undulator sections

• U8 removed

• R = 5,000 (FWHM)

• Aiming for R = 10,000

• Gaussian filter

• 2% efficiency

• Will implement optical

propagation that includes

relevant spatio-temporal

couplings

• Full 3D seed

• λu = 39 mm

• Lu = 3.4 (87 per.)

• Lbr = 1.0 (25 per.)

• 14 undulator sections

SS experience with LCLS, measurement and simulation


• S2E simulations

• ASTRA/ELEGANT/GENESIS

• Phenomenological and wave

optics simulation of mono.

• Shows excellent overall

agreement both in energy and in

spectrum D. Ratner, S. Serkez

20 pC IMPACT e-beam slice properties, HXR


s [m]

E [

GeV

]

0 10 20 30 40 50 60

3.995

4

4.005

4.01

4.015

0 10 20 30 40 50 60-10

-5

0

5

10

s [m]

- 0

0 10 20 30 40 50 600

0.1

0.2

0.3

0.4

0.5

0.6

0.7

I [k

A]

0 10 20 30 40 50 600

0.1

0.2

s [m]

e n [m

m-m

rad

]

0 10 20 30 40 50 600

0.1

0.2

0.3

0.4

0.5

0.6

0.7

I [A

]

0 10 20 30 40 50 600

1

2

s [m]

sE [

MeV

]

0 10 20 30 40 50 600

0.1

0.2

0.3

0.4

0.5

0.6

0.7

I [A

]

head I ~ 350 A

ϵn,x ~ 0.15 mm-mrad

σE ~ 450 keV

Time-dependent S2E parameter scan (very time

consuming), HXR Eγ = 2 keV


d

1.8 2 2.2 2.4 2.6

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

Emax ~ 655 μJ

ξ = 0.03

d = 2.1

ETI ~ 470 μJ

ξ = 0.06

d = 2.15

30% difference in final energy

Pulse length control – emittance spoiling


• Calculations indicate an emittance spoiler foil can withstand the full beam at

high rep rate

• However, the increased load on the collimators might force operation at a

low(er) rep rate

Dispersed bunch

Y

X

• Energy chirped e-beam has

x-t correlation in region of

high dispersion

• Insert foil with triangular

width to continuously tune

the pulse duration

Emittance spoiling foil measurements at LCLS


~100 fs ~6 fs

Y. Ding

Measured foil scan movie at LCLS


Y. Ding

Pulse length control – differential heating


• It is fairly easy to put a notch in the laser heater profile

• Here we assume a 1 ps notch but you can get to a few 100 fs with no heroic

efforts…

unspoiled beam

@ heater spoiled beam

@ heater

A. Marinelli

After compression and acceleration (S2E with

ELEGANT, 100 pC)


few fs lasing

core

garbage

~6 fs

FWHM

A. Marinelli

LCLS MD shifts will be dedicated to this study in the near future

Self-seeding with a chirped e-beam for short pulses


• A chirped e-beam generates a SASE signal

• Monochromator selects a narrow bandwidth and helps to control the seed pulse

duration

• The seed is amplified only over a fraction of the bunch and dominates SASE

• Superradiance can possibly be used to further compress the pulse

SASE undulator Amplifier undulator

K0 K1

λ1 λ1

SXRSS

Y. Ding

chirp SASE BW Mono BW

SASE undulator Amplifier undulator

K0 K1

λ1 λ1

SXRSS

LCLS example


Power profile Power spectrum

0.14eV 13 fs ~7 fs 0.3eV

Documents

LCLS-II Capabilities & Overview - Stanford University · 2015. 2. 9. · LCLS-II Science Opportunities Workshop, February 9-13, 2015 LCLS-II baseline will deliver same beam parameters