Goals

Separation Scheme Options in the LCLS-II Modified LTU Lattice

Y. Nosochkov

LCLS-II Physics Meeting, May 9, 2012

Y. Nosochkov 2

Goals

5/9/2012

Compare HXR/SXR beam separation schemes in the modified LTU lattice:

1. Horizontal kicker with current sheet septum

versus

2. Vertical kicker with Lambertson septum (less expensive)

Compare the kicker strength, orbit amplitude, number of LTU magnets, R56, I5 (ISR emittance growth)

Y. Nosochkov 3

Full lattice with modified LTU

5/9/2012

LTUBypass

Linac

Undulator

HXR

L0

L1 L2 L3HXRSXR

µ

BC2BC1

gun

DL1 DL211-3 to 14-4 14-7 to 20-4

11-1

sd

sd sd

sd

sd

sd

sd

sd

sz szsz

Y. Nosochkov 4

Existing design of Lambertson septum for vertical separation scheme

5/9/2012 P. Emma

Dy = 7 mm at septum

Y. Nosochkov 5

First look at the current sheet septum design for horizontal separation (C. Spencer)

5/9/2012

Assume Dx = 10 mm at septum, B = 2.6 kG, L = 2 m.HXR correction may be required to compensate for residual field.

SXR HXR

More expensive

Y. Nosochkov 6

diagnosticC1

Long drift to minimize wall interference

Low bx at bends

kick

er

sept

um

5/9/2012

Include the kicker orbit as part of the reference trajectoryAdjust septum and SXR main bend field for correction

LTU SXR lattice for horizontal separation

Y. Nosochkov 7

sept

um

kick

er

QDL

44BX

42Q

DL45

QDL

46

QDL

43

X = -10 mm at septumOff-axis through QDL44,45,46 and BX42

Horizontal separation orbit from kicker

5/9/2012

Y. Nosochkov 8

LTU SXR lattice for vertical separation

5/9/2012

3 extra cells are included thus making the LTUS longer by 52.8 mSeptum angle is reduced ~30%

C1 diagnosticKick

er-1

Kick

er-1

sept

um

C2 C3 C4

by is reduced, but bx at bends is increased

SXR geometry downstream of LTU may need to be adjusted

Y. Nosochkov 9

Vertical separation orbit and dispersion

5/9/2012

Y. Nosochkov 10

Parameters

5/9/2012

X-separation Y-separation

LTU HXR + SXR quads 48 54

LTU HXR + SXR main bends 8 8

LTU HXR R56 (mm) 0.385 0.385

LTU SXR R56 (mm) 1.004 0.497

LTU HXR I5 3.0e-9 7.6e-9

LTU SXR I5 4.1e-9 7.7e-9

Kicker-1 (kGm) at 15 GeV 0.173 0.053

Kicker-2 (kGm) 0 0.071

DC1 (kGm) 0.200 0.182

DC2 (kGm) 0.159* 0.394

DC3 (kGm) 0.326* 0.150

DC4 (kGm) 0.055* 0.207

DgISR = 4 10∙ -8 I5 E∙ ∙ 6 = 0.0035 mm-rad at I5 = 7.7e-9 and 15 GeV

* Part of bend field

Y. Nosochkov 11

Some comparison

5/9/2012

• Lambertson septum: less expensive, lower R56, one extra kicker

• Current sheet septum: fewer quads in LTU, lower emittance growth, correctors combined with dipoles