Ultimate Storage Rings
PEP-X and SPring-8 II
R. Hettel for the PEP-X design team
and T. Watanabe et al., SPring-8
FLS 2012
JNAL
March 7, 2012
What is the Future of X-ray Sources at SLAC?
2 km warm linac (33 GeV) +
damping rings:
PEP injection
FACET
LCLS 2
1 km warm linac (16 GeV):
LCLS 1
PEP-II
SPEAR3
LCLS
LCLS 2
LCLS
injector
PEP-X Design Study
PEP-X Baseline Concept
(consolidated experimental halls)
E = 4.5 GeV
I = 1.5 A
ex = 150 pm-rad
(~0.06 nm-rad w/o IBS)
ey = 8 pm-rad
s = 3/6 mm
(without/with 3rd harm rf)
 = ~1 h
top-up injection
every few seconds
(~7 nC, multiple bunches)
• 2 arcs of DBA cells with 32 ID
beam lines (4.3-m straights)
• 4 arcs of TME cells
• ~90 m damping wigglers
• 6 ea 120-m straights for injection, RF,
damping wigglers long IDs, etc.
Same coherent flux as 11-pm USR: higher emittance and current
PEP-X: Diffraction-Limited Storage Ring at SLAC
Energy
4.5-5 GeV
Current
200 mA
Emittance (x/y)
11/11 pm
Bunch size (x/y, ID)
7.4/7.4 mm rms†
Bunch length
4 mm rms*
Lifetime
>2 h*
Damping wigglers
~90 m
ID length (arc)
~4 m
ID length (straight)
<100 m
Beta at ID center, (x/y) 4.92/0.8-5 m
Circumference
2199.32 m
Harmonic number
3492
† Vertical beam size can be reduced towards 1 mm
* Harmonic cavity system would increase bunch length
to ~8 mm and double the lifetime
sufficient dynap
for off-axis
injection
Multibend Achromat Cells
7BA cell
modified from
MAX-4
cancelling all 3rd
and 4th order
resonances except
2nx-2ny
Y.Cai et al., SLAC-PUB-14785, 2011
optimizing dynap and lifetime
with ELEGANT
M. Borland
USRs - Spectral Brightness
Brightness Envelopes
not including SC IDs
10
1.E+23
25-m ID
1.E+22
6
1
ALS upgrade: 1.9 GeV, 0.5 A, 195 m
2200 x 30 pm-rad, 4-4.5 m IDs
2
NSLS-II: 3 GeV, 0.5 A, 792 m
600 x 8 pm-rad, 3-4 m IDs
3
MAX-IV: 3 GeV, 0.5 A, 528 m
263 x 8 pm-rad, 3.8 m IDs
4
PETRA IIII: 6 GeV, 0.1 A, 2304 m
1000 x 10 pm-rad, 5 m IDs
5
APS upgrade: 7 GeV, 0.18 A, 1060 m
2500* x 8 pm-rad, 4.8 m IDs
9
6
brightness (ph/s/mm2/mr2 0.1%BW)
5-m ID
8
1.E+21
5
1.E+20
6
4
2
1.E+19
7
3
1.E+18
1
1.E+17
0.01
7
SDLS: 2 GeV, 0.5 A, 250 m
40 x 40 pm-rad, 4 m IDs
8
PEP-X: 4.5 GeV, 0.2 A, 2200 m
11 x 11 pm-rad, 4 m IDs
9
USR7: 7 GeV, 0.2 A, 3160 m
15 x 15 pm-rad, 8 m IDs
10
0.1
1
photon energy (keV)
10
100
Cornell ERL: 5 GeV, ~3150 m
30 x 30 pm-rad, 0.1 A or
8 x 8 pm-rad, 0.025 A
TevUSR: 11 GeV, 0.1 A, 6283 m
1.3 x 1.3 pm-rad, 4 m IDs
USRs – Coherent Fraction
Coherent Fraction
1.E+00
7
3
coherent fraction
1.E-01
6
4
2
1 ALS upgrade: 2200 x 30 pm
1.E-02
5
1
2 NSLS-II: 600 x 8 pm
3 MAX-IV: 260 x 8 pm
1.E-03
4 SDLS: 40 x 40 pm
5 USR7: 15 x 15 pm
1.E-04
6 PEP-X: 11 x 11 pm
7 TevUSR: 1.3 x 1.3 pm
1.E-05
0.01
0.1
1
photon energy (keV)
10
100
PEP-X Soft X-ray FEL in switched bypass
Ee- = 4.5 GeV
ex,y = ~11 pm-rad
lFEL = 1 nm
l/4p = 80 pm-rad
Ipk = 300 Apk
LID = 50-100 m
Ppk = few hundred kW
rep rate: kHz
Can inject special short, high peak
current bunch to lase for a few turns
Soft X-ray Partial Lasing with Stored Beam in PEP-X
Z. Huang, C. Pellegrini et al.
3.3 nm
379 eV
30 nm
42 eV
Preliminary studies show that radiation from 50-100 m undulator whose first
harmonic is tuned to < ~380 eV (> 3.3 nm) would be enhanced by one to two
orders of magnitude by the SASE FEL process acting with the stored beam.
PEP-X ERL – some options
Option: 2-pass with
2.5-GeV linac
• SCRF = 1.3 GHz
• “bunch stealing” @ ~ 1 MHz could drive FELs
SPring-8 II
http://www.spring8.or.jp/en/about_us/whats_sp8/spring-8_II
SPring-8 upgrade plans
(from T. Watanabe)
Goal:
- Significant improvement in light source performance,
especially brilliance
- In 2019 with 1 year shutdown
- Cost range: approx. 40 billion Japanese yen
“Boundary conditions”:
- To take full advantage of existing resources
>> Reuse the existing tunnel
- ID beamline hutches should not be moved.
- Same X-ray spectral range : a few to 100 keV
- Good stability
SPring-8 II – at-energy linac injector
A high-quality injection beam is needed.
At SPring-8 we have XFEL Linac, which will be used as a full-energy
injector to the storage ring.
XFEL(SACLA)
Booster
SR
Linac Parameters:
(typical)
Energy: 8 GeV (max.)
Emittance: 40 pm.rad
Energy Spread: 0.01 %
Bunch Length: 30 fs (rms)
Electron Charge: 300 pC – 1 nC
14
SPring-8 II – electron energy
24
Intra-beam scattering (IBS)
10
23
10
22
Brilliance
10
21
10
20
10
6 GeV
8 GeV
Current
19
10
18
10
17
10
4 – 6 GeV is the best
1
10
100
Energy (keV)
6 GeV is better than
8 GeV up to 100+ keV
6 GeV is presently assumed, but 4.5-5 GeV under consideration
1000
SPring-8 II – 6-bend achromat lattice
Emittance = K
(Electron energy)2
(#
bends)3
X D
Natural emittance
= 67 pm.rad
＋
Damping by ID's
Damping wiggler
Damping partition control
Coupling control
etc...
SPring-8 II – damping by IDs and wigglers
SPring-8
Electron energy
Current
Emitance
Energy spread
Coupling
Bunch length (rms)
Circumference
# beamlines
8 GeV
100 mA
3.4 nm.rad
0.0011
0.2 %
13 ps
1436 m
62 max.
SP-8 II
(planned)
6 GeV
~300 mA
67→10 pm.rad
~0.001
~2 %
>20 ps
1436 m
62+ max.
* Parameters for SP8-II may be changed.
Brilliance: SPring- 8 vs. SPring-8 II
X 1000
Energy :
6 GeV
Emittance: 35 pm.rad
Coupling: 2 %
Energy spread: 0.1%
Current:
300 mA
SPring-8 II – possibility of short bunch operation
1) ~ 1 ps, using x3.5 harmonic cavity
2) Should not affect extremely small emittance bunch
Rough image:
SP-8 II
40ps
40ps
1ps
40ps
XFEL
~10 fs
Now under discussion with users
SPring-8 II – new injection scheme
※DA ~ ±3 mm
A single device that enables both
on- and off-axis injections
SPring-8 II – strong multipole magnets
A quarter of the unit cell
Beam
Critical magnets
Need R&D
New vacuum design necessary
SPring-8 II – new RF system
New design
Fundamental RF system
HOM
damper
（MAFIA）
f [MHz]
508.58
508.58
mode
TM010
TM020
Q0
40000
61300
Rz [MΩ]
6.2
7.6
Rz/Q0
155
123
Compact design for fitting in new
straight sections.
520 mm
SP8-II
Bell-shaped
(measured)
Goal:
8MΩ
Cavity for
current
SP8
SPring-8 II – harmonic RF system
e-bunch needs to be lengthened
for lifetime and less IBS effect
New higher harmonic RF system
enables it.
SPring-8 II – dynamic aperture
Dynamic aperture
with 20um SX errors
Sextupole alignment error:  = 10 mm, cutoff = +/-20 mm
SPring-8 II – Summary
- Goal: ~10pm.rad = ultimate storage ring
- Planned for 2019 with one-year shutdown
- Take full advantage of existing resources
- Now under extensive studies for lattice design and
technology developments
- Challenging issues clarified
- New components proposed and studied, but need more
- A couple of design alternatives. Open to any change.
- R&D will start in FY2012