Post on 12-Jan-2016
description
1 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
1LCLS Undulator StatusMarch 12, 2010
LCLS-II Undulator Parameters
Heinz-Dieter Nuhn – LCLS Undulator Group LeaderMarch 12, 2010
2 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
2LCLS Undulator StatusMarch 12, 2010
LCLS-II
An initial rough evaluation of LCLS-II undulator parameters will be presented.
Priority is given to the Soft-Xray line, which is likely to be based on short variable gap undulators.
Segment shortness is required to enable the low beta-functions needed for increased FEL performance.
3 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
3LCLS Undulator StatusMarch 12, 2010
ExistingExistingPhase-0Phase-0Phase-1Phase-10.75-15 Å 0.75-15 Å
4-14 GeV4-14 GeV
FEE-1Existing 112-m Undulator (1.5-15 Å)
0.75 Å0.75 Å
SHAB30 m
Shortened 74-m Undulator
5 m
FEE-2SXR2 (45 m)
5 m
full polarization full polarization controlcontrol
self-seeding self-seeding optionoption
6-60 6-60 ÅÅadjust. gap adjust. gap
6-60 6-60 ÅÅadjust. gap adjust. gap
SXR1 (45 m)3-7-GeV bypass3-7-GeV bypass
4-GeV SXR and 14-GeV HXR simultaneous op’s with bypass line
2-pulse 2-pulse 2-color2-color
No civil construction. Uses existing beam energy and quality.No civil construction. Uses existing beam energy and quality.
full polarization full polarization controlcontrol
Phase-2Phase-2Phase-3Phase-3
EEHG*?EEHG*?
240 nm 240 nm 6 nm 6 nm
Phased Enhancement Plan for LCLS-II
* G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009) * G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009)
5 m
full polarization full polarization controlcontrol
Shortened (1.5-15 Å)
Larger Gap Undulator(0.75-7.5 Å)
self-seeding self-seeding HXR optionHXR option(2 bunches)(2 bunches)
Large GapLarge Gap (0.5-5 Å)(0.5-5 Å)
Large GapLarge Gap (0.5-5 Å)(0.5-5 Å)
4 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
4LCLS Undulator StatusMarch 12, 2010
LCLS-I U 1 Enhancement
=
2.8
I pk
= 3
00
0 A
,
xy=
0.6
µm
15 Å 1.5 Å23 Å 1.24 Å
11 Å 0.62 Å
9.6 Å 0.52 Å 130 m
15 GeV3.5 GeV
5 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
5LCLS Undulator StatusMarch 12, 2010
LCLS-II U 2 FEL Performance Estimatelin
ear
hel
ical
<>
= 5
m,
= 2
.8I pk
= 2
00
0 A
,
xy=
0.6
µm
6 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
6LCLS Undulator StatusMarch 12, 2010
LCLS-II U 2 FEL Performance Estimatelin
ear
hel
ical
<>
= 5
m,
= 2
.8I pk
= 2
00
0 A
,
xy=
0.6
µm
7 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
7LCLS Undulator StatusMarch 12, 2010
LCLS-II U 2 Small Period Undulator
<>
= 4
m,
= 2
.8I pk
= 2
00
0 A
,
xy=
0.6
µm
hel
ical
hel
ical
8 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
8LCLS Undulator StatusMarch 12, 2010
Optimum beta functions at u = 4.0 cmh
elic
alh
elic
al
9 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
9LCLS Undulator StatusMarch 12, 2010
Beta Function and Undulator Length
Undulator: 1.80 m Break0.70 m
Break0.70 m
Half FODO Length: 2.50 m
Minimum <x,y> = 5 m
ChicaneRF Cavity BPMQuadrupole
The smallest average beta-function achievable with a FODO lattice is
The FODO length is determined by segment length and break length
Breaks between segments need to be sufficiently wide to allow space for essential components, such as quadrupole, BPM, Chicane.
Smallest practical quadrupole separation is 2.5 m, corresponding to a FODO length of 5 m .
,x y FODOL
EXAMPLE:
Be
llow
s
10 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
10LCLS Undulator StatusMarch 12, 2010
Multi-Segment variable gap undulators require phase shifters between segments to adjust gap dependent inter-segment phase slippage. An example for such achicane is shown here. Field levels have been kept low to reduce in-tunnel powerrelease.
Example Chicane Dimensions
L = 9 cm
L = 4.5 cm L =4.5 cm
xmax
L = 24 cm
3 cm
E 7.0 3.0 GeV
r 1.2 6.0 nm
B 203 195 G
x’ 78 175 µrad
xmax 7.6 17 µm
360 360 degXray
x -5.9 -13.2 µm
R56 0.74 3.7 nm
11 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
11LCLS Undulator StatusMarch 12, 2010
Beta-Function at 6 nm
Smallest practical beta function 4-5 m is above optimum.
Lsat,mag~10.0 m for x,y = 4 m
Lsat,mag~10.8 m for x,y = 5 m
Opt
imum
12 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
12LCLS Undulator StatusMarch 12, 2010
‘Optimum’ Beta-Function at 6nm
Optimum beta function would reduce saturation length by more than factor 2 but is not accessible.
Lsat,mag~4.3 m for x,y ~ 0.1 m
13 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
13LCLS Undulator StatusMarch 12, 2010
Optimum Beta-Function at 0.6 nm
At 0.6 nm beta function of 4-5 m is close to optimum.
Considered Value
Optimum Value
14 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
14LCLS Undulator StatusMarch 12, 2010
Undulator TypesA number of different variable field undulator types are under consideration
Parallel-Pole Variable Gap Fixed Linear Polarization
Hybrid or Pure Permanent Magnet
Apple Type Variable Gap Variable Linear/Circular Polarization
Hybrid or Pure Permanent Magnet
Delta Type Variable Phase Variable Linear/Circular Polarization and Intensity
Pure Permanent Magnet
Superconducting Helical Variable Excitation current Fixed Circular Polarization [Substantial R&D required]New Designs …
Key issues arePrecision Hall probe measurementsK stability and settabilityCompact design to mount on movable girders.Gap > 7 mm
15 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
15LCLS Undulator StatusMarch 12, 2010
Variable Polarization Undulator TypesTwo adjustable phase undulators assembled in one device**.
**A. Temnykh, Phys. Rev. ST Accel. Beams 11, 120702 (2008).
DE
LT
A
*J. Bahrdt, et al., UNDULATORS FOR THE BESSY SOFTX- RAY FEL, Proccedings of the 2004 FEL Conference, pp. 610-613.
Adjustable Phase Undulators
APPLE-II APPLE-III*
Variable Gap
Fixed Gap
Full K range available through row adjustment
16 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
16LCLS Undulator StatusMarch 12, 2010
The LCLS-I undulator resonance can be shifted to lower wavelengths with moderate loss in xray energy.Initial parameter development for the LCLS-II undulators has started, giving priority to the new soft x-ray line.The goal is a compact variable gap design to cover wavelengths between 6 nm and <0.6 nm at electron energies in the range 3-7 GeV.The low emittance and lower electron energy require beta functions of order 5 m or smaller for best utilization.Low beta-functions require a short FODO length, i.e., short undulator segments of length 1.8 m and compact break sections.The total length of each of the 2 soft x-ray undulator lines is expected to be about 50 m.
The LCLS-I undulator resonance can be shifted to lower wavelengths with moderate loss in xray energy.Initial parameter development for the LCLS-II undulators has started, giving priority to the new soft x-ray line.The goal is a compact variable gap design to cover wavelengths between 6 nm and <0.6 nm at electron energies in the range 3-7 GeV.The low emittance and lower electron energy require beta functions of order 5 m or smaller for best utilization.Low beta-functions require a short FODO length, i.e., short undulator segments of length 1.8 m and compact break sections.The total length of each of the 2 soft x-ray undulator lines is expected to be about 50 m.
Summary
17 Heinz-Dieter Nuhnnuhn@slac.stanford.edu
17LCLS Undulator StatusMarch 12, 2010
End of Presentation