position of the 3rd harmonic system
DESCRIPTION
Position of the 3rd Harmonic System. T. Limberg. Injector (with first Bunch Compression Stage). Injector Hall. XTIN: Length = 48m, accommodates Gun, ACC1, 3,9GHz, Laser Heater, Diagnostics, Dump Line. XSE: Length = 22.55m, accommodates Shielding, Dogleg. Start Linac Tunnel. Dogleg. - PowerPoint PPT PresentationTRANSCRIPT
T. Limberg
Position of the 3rd Harmonic System
Position of the 3rd Harmonic System
Injector (with first Bunch Compression Stage)2
European XFEL MAC May 2010T. Limberg
Position of the 3rd Harmonic System
Injector Hall 3
European XFEL MAC May 2010T. 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 Restraints4
European XFEL MAC May 2010T. 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 Diagnosticsdescribes the boundary conditions for optics functionsShielding: - 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 distanceof 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 Optimization5
European XFEL MAC May 2010T. Limberg
Assumed: - ideal installation of the quadrupoles without any offsets.- Energy spread of the bunch is 2% RMS
Results:- Emittance growth due to chromaticityeffects over the first 80m is about 5-10%
LH BC0
DOGLEG
Position of the 3rd Harmonic System
Laser Heater6
European XFEL MAC May 2010T. Limberg
Horizontal Vertical
, m 4.65 18.33
1.6 -2.6
D, m 0.03 0
, m 615 271
Off-crest acceleration in ACC1 energy spread of 2%
22 D
27,2y
x
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 OTRUNDULATOR
Position of the 3rd Harmonic System
MAC Proposal
Avoid energy chirp in laser heater and dogleg:
• Shift 3rd harmonic rf system downstream of dogleg
• Provide chirp for compression with 3rd harmonic
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European XFEL MAC January 2010T. Limberg
Position of the 3rd Harmonic System
Compression System Overview8
European XFEL MAC January 2010T. 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 2010T. Limberg
Position of the 3rd Harmonic System
Running fundamental on crest 10
European XFEL MAC January 2010T. Limberg
nn
nn
a
a
a
nkk
nk
p
p
p
sin
cos
0)(
00
011
''
'1
22
Control of third derivative (tail control) is lost
For given energy a1 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.11
European XFEL MAC January 2010T. 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 2010T. Limberg
Position of the 3rd Harmonic System
RF and LLRF Issues
Klystron will be installed underneath module
LLRF system will be installed close to 3rd harmonic rf
→ no additional problems for these systems at the linac tunnel position
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European XFEL MAC January 2010T. Limberg
Position of the 3rd Harmonic System
Summary for Shifting 3rd 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 2010T. Limberg