Position of the 3rd Harmonic System

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29 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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T. Limberg



Position of the 3rd Harmonic System


Position of the 3rd Harmonic System

Injector (with first Bunch Compression Stage)

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European XFEL MAC May 2010

T. Limberg


Position of the 3rd Harmonic System

Injector Hall

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European XFEL MAC May 2010

T. Limberg

Start Linac Tunnel

XTIN:

Length = 48m, accommodates Gun, ACC1, 3,9GHz, Laser Heater, Diagnostics, Dump Line.

XSE:

Length = 22.55m, accommodates Shielding, Dogleg


Position of the 3rd Harmonic System

Optical Restraints

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European XFEL MAC May 2010

T. Limberg

Laser Heater

Diagnostics

Shielding

Dogleg

BC0

Phase Shifter

LH:


-

round and as stable as possible beam size required

Diagnostics:


-

consists of TDS and 4 OTR screens


-

Optics at OTR screens is implemented by means of a

1.5 FODO cell with the phase advance of 76
°


-

Fixed phase advance between TDS and OTR screens


-

Optics after LH is fixed. Entrance into the Diagnostics

describes the boundary conditions for optics functions

Shielding:


-

Concrete solid wall of 5.1m thickness with a spare place

for the beam pipe. However two quadrupoles inside are

needed to control the beta function.

Dogleg:


-

Combination of two four cell arcs (8 cell system)


-

Provides a vertical displacement of the beam for a distance

of 2,75m over the length of 20m.


-

First order momentum compaction r56 is zero.

Phase Shifter:

-

Two 4m long FODO cells

-

Allows to adjust the phase advance by +
-
36
°



Position of the 3rd Harmonic System

After Chromatic Optimization

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European XFEL MAC May 2010

T. Limberg

Assumed:

-

ideal installation of the quadrupoles

without any offsets.

-

Energy spread of the bunch is 2% RMS

Results:

-

Emittance growth due to chromaticity

effects over the first 80m is about 5
-
10%

LH

BC0

DOGLEG


Position of the 3rd Harmonic System

Laser Heater

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European XFEL MAC May 2010

T. Limberg

Horizontal

Vertical

b
, m

4.65

18.33

a

1.6

-
2.6

D, m

0.03

0

s
,
m
m

615

271

Off
-
crest acceleration in ACC1


energy spread of 2%

2
2

b
s
D


27
,
2

y
x
s
s
at the moment the best possible ratio

Length, mm

BL.1

200

BL.2

200

OTR, BPM

300

UNDULATOR

800

Total

2600

Optics and beam parameters in the undulator

Length of the elements in LH

BL.1

BL.2

BL.2

BL.1

OTR

OTR

UNDULATOR

f5,7
°


Position of the 3rd Harmonic System

MAC Proposal



Avoid energy chirp in laser heater and dogleg:



Shift 3
rd

harmonic rf system downstream of dogleg



Provide chirp for compression with 3
rd

harmonic


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European XFEL MAC January 2010

T. Limberg


Position of the 3rd Harmonic System

Compression System Overview

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European XFEL MAC January 2010

T. Limberg


Position of the 3rd Harmonic System

Relation between rf sum shape and amplitudes and phases of fundamental
and harmonic rf systems (normalized to beam energy)

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European XFEL MAC January 2010

T. Limberg


Position of the 3rd Harmonic System

Running fundamental on crest

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European XFEL MAC January 2010

T. Limberg



































n
n
n
n
a
a
a
nk
k
nk
p
p
p


sin
cos
0
)
(
0
0
0
1
1
'
'
'
1
2
2


Control of third derivative (tail control) is lost




For given energy
a
1

in dogleg, energy
p

upstream of BC0 will


vary for different working points (or otherwise)




Beam
-
based rf feedbacks might get simpler


Position of the 3rd Harmonic System

First checks (0.1 nC case) look o.k.

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European XFEL MAC January 2010

T. Limberg

Longitudinal
phase space

Current
Profile


Position of the 3rd Harmonic System

Effort and cost: Kryo



Feedcap & endcap



Knees for transfer line



Tight installation



(Very) rough estimate for extra kryo cost: 1 M


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European XFEL MAC January 2010

T. Limberg


Position of the 3rd Harmonic System

RF and LLRF Issues


Klystron will be installed underneath module



LLRF system will be installed close to 3
rd

harmonic rf





no additional problems for these systems at the linac tunnel position

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European XFEL MAC January 2010

T. Limberg


Position of the 3rd Harmonic System

Summary for Shifting 3
rd

Harmonic rf and Running First Module on Crest


Plus:


Relaxed conditions in dogleg and laser heater


Might simplify beam
-
based rf feed
-
backs


Minus:


Reduced tunability of bunch compression system


~1 M


extra cost


Tight installation


Independent and early commissioning not possible



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European XFEL MAC January 2010

T. Limberg