LCLS-II Particle Tracking: Gun to Undulator

P. EmmaJan. 12, 2011

SLAC linac tunnel BTH & U-Hall

Linac-0’L 6 m

Linac-1’L 9 mrf -20°

Linac-2’L 326 mrf -32°

Linac-3’L 582 mrf 0°

BC1’L 6.5 m

R56 -46 mm

BC2’L 23 m

R56 -29 mmDL1’

L 12 mR56 6.3 mm

undulatorsL 120 m

6 MeVz 0.62 mm 0.05 %

135 MeVz 0.62 mm 0.07 %

250 MeVz 0.13 mm 1.1 %

4.2 GeVz 7 mm

0.43 %

13.5 GeVz 7 mm 0.01 %

Linac-X’L 0.6 mrf -160

V0 -19 MV

11-3b14-4dX

SXR

1-km bypass

line

11-1b,c,d

...existinglinac

14-7b20-4d

LCLS-I

LCLS-I

0.24-2 keV

2-13 keV

L0-a,b

rfgun HXR

0.5-10 keV

LCLS-II Accelerator for 13.5 GeV, 120 Hz, 250 pC

Jan. 12, 2011, 11:16 AM - PE

LCLS-II Layout (After Linac)

LCLS-I

LTUH

LTUS

LTU2

LTU1

LCLS-II

mLINACEND

muon plug wall

LCLS-II Layout (After Linac)

LCLS-II Optics in Elegant (250 pC, 13.5 GeV)

BC1 BC2

Bypass Line2.4°

bends

HXR und.

Thanks to Mark Woodley and Yuri Nosochkov

2E5 macro particles (250 pC) tracked through Parmela to 135 MeV.

1st and 2nd-order optics (dipoles, quads, soln’s) and sinusoidal RF.

Longitudinal wakes of SLAC S-band RF structures.

Resistive longitudinal wakes of 1240 meters of 2-inch diameter stainless steel beam pipe (sector 20-5 to exit of muon-plug wall).

Resistive longitudinal wakes of 330 meters of 1.625-inch diameter copper plated (?) LTU2 beam pipe.

CSR in all bends (1D model in Elegant) - includes transients but ignores transverse beam size (typically not a big impact).

ISR in all bends – small impact on slice E-spread and slice emittance.

Laser heater adds 17 keV rms E-spread at 135 MeV.

All components are error-free: perfect alignment & CSR-steering is removed.

What’s Included in the Elegant Tracking?

LCLS-II Particle Distributions (in Longitudinal Phase Space)

Output from Parmela at135 MeV

Outputfrom Elegant at 14 GeV

35 A

~3 kA…with CSR

0.01% rms

CSR-Induced Emittance Growth Along BC2 (250 pC, 4.2 GeV)

This calculation removes the linear correlations in x and x’ with energy in order to reveal only the irrecoverable CSR effect. The projected emittance after the BC2 without removing these linear correlation is 1.32 mm.

1.32 mm

1.09 mm

0.53 mm

gex

gey

Includes double-horn distribution of LCLS

CSR-Induced Slice Emittance Before and After BC2 (250 pC, 4.2 GeV)

Slice Emittance Before BC2

Slice Emittance After BC2

Includes double-horn distribution of LCLS

CSR-Induced Emittance Growth Along LCLS-II Accelerator (13.5 GeV)

BC1 BC2Bypass

Dog-Leg

LTU2 2.4-deg Bends

might be

fixed?

Vertical Bends

Includes double-horn distribution of LCLS

Emittance across LTU2 bend system (horizontal in black and vertical in blue), including the 2.4-deg bends and the LTUS SXR branch line optics (8 dipoles total).

CSR-Induced Emittance Growth Along LTU2 & LTUS (13.5 GeV)

2.4° bends LTUS DL-bends

pulsed bend

Includes double-horn distribution of LCLS

Resistive-Wall Longitudinal Wakefield of 1240-m of 2-inch SS Pipe(Existing Bypass Line)

Bane, Sands

Resistive-Wall Longitudinal Wakefield of 1240-m of 2-inch SS Pipe(Existing Bypass Line)

Before bypass linev

After bypass line

Final Slice Emittances (x & y) - with CSR - Before Undulator(250 pC, 13.5 GeV)