Design Considerations for the NGLS (Next Generation Light Source)

Paul Emma, et. al.Sep. 18, 2013

Design Considerations for the NGLS (Next Generation Light Source)

NGLS

What are the new facility directions ?

High-rate and Continuous Wave (CW) operation

FEL seeding for narrow BW & full coherence

Femtosecond x-ray pulses (~ 10-15 sec)

Multiple FELs with independently tunable wavelengths

Pulse length and BW control at FT-limit

Two-Color pulses with variable relative timing & color

Expandable facility well into the future

A Next Generation Light Source (NGLS)

A High Repetition Rate CW X-Ray FEL ArrayCW Superconducting Linac

X-Ray Beamlines and End-stations

3-9 FELs

~10 ms

~100 ms 600 ms

1 ms (CW)

BC1 BC2 2.4 GeV1 MHz injector

An Array of Unique Free-Electron Lasers

FEL-1Self-Seeded(250-1250 eV)

FEL-3Two-Color(250-1000 eV)

FEL-22-Stage HGHG(100-600 eV)

NGLS Layout

1 MHz CW e- injector ( = 0.6 mm, Q = 300 pC)1.3-GHz CW SRF @ 15 MV/m (24 CM’s, 0.3 mA)Two bunch compressors + heater (500 A)Beam spreader using RF deflectors (9 FELs)Three (initial) very diverse FEL designsDiagnostics and collimation sections720-kW main beam stops (3)

injector linac spreaderFELs (1-9)

beam stops

compressorse- diagnostics

e- diagnostics

exp. halls

collimation

Parameter Value UnitRF frequency 1300 MHzOperating temperature 1.8 KNumber of cav. per CM 8 -Mean operating gradient 14 MV/mAverage Q0 per CM 2101

0-

Lorentz detuning 1.5 Hz/(MV/m)2

Peak detune allowance 15 HzQext 3107 -Min. RF power per cavity 5.4 kWTotal cavity dynamic load 12.5 WRF AC power 1.8 MWTotal cryo-plant AC power 3.6 MW

Parameters for the CW SC-Linac (2.4 GeV)

J. Corlett, L. Doolittle, A. Ratti, R. Wells, et al.

Linac V(MV)

(deg)

Grad.(MV/m)

N CM’s

L0 95 ~0 15.9 1L1 129 –20 8.2 2L2 604 –23 12.9 6L3 1630 0 14.0 15

Average current = 0.3 mA

Achieved:Successful CW operationExcellent RF design performance at full power (20 MV/m)E-beam design energy (0.75 MeV)< 10-10 gun vac. pressureCs2Te cathode generating 100’s of pC/bunch @ 1 MHz40 C in 4 days: QE goes from 10% to 4% (promising lifetime)

Next Steps:Test CsK2Sb cathodes (green laser)6D phase space characterization at gun energy (and later at 30 MeV)

NGLS Photo-Cathode Gun (APEX)

F. Sannibale, D. Filippetto, C. Papadopoulos, R. Wells

186MHz

e-

NGLS High-Rate Injector (R&D at APEX - LBNL)

RF Gun

0.8 MeVwarm

UV

Bunch charge 300 pC

Beam rate 1 MHzGun gradient 20 MV/mLaser pulse (flat top) 44 ps

7 A (45 A)

Final e-beam energy 94 MeV

Energy spread (rms) 20 keVDrive laser l (Cs2Te) 266 nmQuantum efficiency ~5 %

solenoids1.3-GHz buncher

8

x,y < 0.6 mm

Ipk 45 A

sE/E 20 keV

APEX Gun (1 MHz CW)

Cs2Te

F. Sannibale, D. Filippetto, C. Papadopoulos, R. Wellscold

94 MeV

Eight 9-cell TESLA cavities (1.3 GHz)

APEX Parameters (done):

first beam

Mar. 18 ’13

velocity bunching ( 1/6)

186MHz

650-MHz booster for the injector? Possible layout for injector and first linac section

moderate ( RF compression beam is close to parabolic.

at end of linacNo need for 3.9 GHz RF linearizer

1.5-2 kAM. Venturini

Removing Energy Chirp with a Wakefield

add 5-m long de-chirper(2a = 6 mm)

L3 on crest

…or 35-deg off crest

5-m long dechirper

NGLS Longitudinal Phase Space

K. Bane,P. Emma,H.-S. Kang,G. Stupakov,M. Venturini

point-charge wake

PAL-ITF Dechirper Simulationsdechirper off

a = 4-15 mmp = 0.5 mmh = 0.6 mmg = 0.3 mmL = 1 m

dechirper on

PAL-ITF (Korea)

corrugated pipe

Aug. ‘13 experiment

Linac and Compressor Layout for 4 GeV

(cathode to undulator)

CM01 CM2,3 CM04 CM08 CM09 CM34

BC1280 MeV

R56 = -85 mmIpk = 100 A

Lb = 0.75 mmsd = 0.62 %

BC2850 MeV

R56 = -80 mmIpk = 500 A

Lb = 0.13 mmsd = 0.50 %

GUN0.75 MeV

LH94 MeV

R56 = -5 mmIpk = 46 A

Lb = 1.5 mmsd = 0.02 %

L0 0

V0 94 MV

L1 = -17.0°

V0 = 195 MV

HL = 180°

V0 = 0

L2 = -18°

V0 = 600MV

L3 = 0

V0 = 3150 MV

Spreader4.0 GeVR56 = 0

Ipk = 500 ALb = 0.13 mmsd 0.008 %

300 pC; Machine layout 2013-08-27; Bunch length Lb is FWHM

3.9GHz

Linac eV(MeV)

(deg)

Acc. Grad. (MV/m)

N. Cryo Mod’s

Spare Cav’s

L0 94 ~0 15.9 1 1

L1 194/215 -17/-30 12.4/15.9 2 1

HL 0/-30 -180 15.2/15.9 1 (3.9GHz) 0

L2 600/630 -18/-25 15.2/15.9 5 2

L3 3150/3200 0/±10 15.5/15.7 26 12

t

V 186

139

139 MHz = 3/4186 MHz (7.2 ns)

zDC bendseptumseptum

Beam Spreader System

RFdeflector

Split again 3 times with 3 more deflectors at 151 MHz = 13/16186 MHz (6.6 ns)

y

x

y

x

y

x

x

RF gun frequency = 1300/7 MHz 186 MHz(5.4 ns)

end oflinac

Phase-I (3 FELs) needs only one

RF deflector

Keep l long (139 MHz)

Dt = 5.4 nscollide two x-ray pulses

distribute e- bunches to 3-9 FELsM. Placidi,C. Sun

5.4 ns

Pulse-Stealing Diagnostics (BC1, BC2, EOL)

250-W dump

1200-W dump

1 MHz Linac

Intercepting diagnostics used only at low rate

Measure at 1 kHz:• Energy• Proj. energy spread• Slice energy spread• Proj. emittance• Slice emittance• Bunch length• Charge…

1 kHz Kicker (<1 ms)

TCAV

Screens/wires

100-W dump

Superconducting Undulator Technology

LCLS

Nb 3Sn

Perm. Mag.

NbTiNGLS

S. Prestemon, D. Arbelaez80% of short sample limit

Use Nb3Sn SC-undulators for efficiency & rad. hardness

Magnetic gap = 7.5 mm. Vacuum chamber 5.5 mm

97 m

Lmag = 26.4 m, Nu = 8 Lmag = 36.3 m, Nu = 11 P 

35.2 m 52.8 m

8.8 m

mon

o.20

000

4.4 mFEL-1 (SASE/Self-Seeded)

1 MHz230-1250 eVTo 2 keV SASENear FT-limit

58 m

         P    

rad-1mod

-1

rad-2mod

-2

4.4 m

6.0 m66 6 6

Lmag = 26.4 m, Nu = 8

FEL-2 (2-Stage HGHG)

0.1 MHz100-600 eV + 3rd stage optionFT-limited pulses (7 - 70 fs)

123 m

Lmag = 33 m, Nu = 10 P   

4.4 m

mod

1

48.4 m

Lmag = 33 m, Nu = 10 P

48.4 m

mod

2

0.5 mr

3 m

mFEL-3 (Two-Color FEL)

0.1 MHz, 230-1000 eV, two 1-fs pulses, variable color, pol., & timing

Based on Fermi Results in Trieste

Based on SXRSS

Based on SPARC Chirp/Taper Results in Frascati

Chirped/Tapered 2-Color FEL

Two 1-fs pulses at 0.1 MHz, 250-1000 eV, var. color, pol., & timingPossible attosec. pulse with ESASE

Few cycle 2-5 mm laser pulse chirps very short section of e-beam

G. Marcus, A. Zholents

ΔtFWHM ≈ 1.7 fs

21010 at1.0 keV

addtaper

8 fs

chirpedSASE

e-

More LBNL Presentations Soon

Wed. Sep. 25 (13:30)G. Penn - Three Unique FEL’s for NGLSJ. Byrd - Longitudinal Feedback for SRF Linac

Thurs. Sep. 26 (09:00)M. Venturini – Bunch Compression and DynamicsF. Sannibale – High-Rate, High-Brightness Injector

Wed. Oct. 2 (13:30)?J. Corlett - Superconducting RF Linac Design

C. Steier - Collimation