Download Current Status of SPring-8 Insertion Devices and SCSS Project

Overview of the SCSS project
and beam calculations
Toru HARA
RIKEN/SPring-8
• Recent progress of SCSS project
- Electron gun
- Accelerator components
- Undulator
• Beamline design
- Chicane
- FEL (3D code SIMPLEX)
SCSS project
SCSS (SPring-8 Compact SASE Source) is a dedicated FEL facility, and 3 groups of
RIKEN are collaborating for construction of LINAC (Shintake’s group), Undulator
(Kitamura’s group) and Beamline (Ishikawa’s group).
Key technology
• Thermionic electron gun
• High-gradient C-band accelerator (40 MeV/m)
• In-vacuum undulator (lu=15mm)
First phase
Second phase
1 (or 0.5) GeV beam energy for 3.6 (or 15) nm radiation
+ User experiments
~ 6 GeV for 1 Å radiation
+ Multi beamlines
Current status
• Building design (budget for building is not approved yet).
• Development of components, electron gun, accelerating tube, undulator,
BPM, mover etc...
Where to build SCSS?
Next to 1 km BL
How to build 1 GeV SCSS?
Injector of SCSS (still tentative)
L-band extended and X-band aborted.
(by Y.Kim)
Development of thermionic electron gun
•
•
•
•
High temperature single crystal cathode CeB6 (mirror surface).
Stable and long life time (>10000 hours).
Uniform electron emission.
No grid.
By K.Togawa and Onoe
Cathode heating test
By K.Togawa and Onoe
500 kV electron gun test bench
High voltage test, emission test
and emittance measurement are planned.
COM free cavity BPM
TM010 mode does
not couple out to
pickup antenna.
Submicron resolution
By T. Shintake
Other components
Klystron and modulator
Mover (resolution < 1 mm)
Demagnetization test against high energy electrons (by T. Bizen)
Possibility of using permanent focusing magnets
Accelerating tube test (by H. Matsumoto and T. Inagaki)
In-vacuum undulator
800
1520
φ1 5 0
More compact than conventional
SPring-8 undulators
960
Magnetic period
15 mm
Number of periods
300
Segment length
4.5m
(1 segment consists of 4 units)
Minimum gap
2 mm
K at 3.6 mm gap
1.3
45° tilted Halbach type (by T.Tanaka)
Independent movement of upper
and lower magnet arrays
In-vacuum undulator
Magnetization is tilted by 45°
for magnet sorting.
By T. Tanaka
Field measurement and alignment
By T. Tanaka and T. Seike
1 mm thick 3-axis hole probe
Chicane in front of the undulator
• Dog-leg or chicane in front of the undulator to
- cut off dark current from LINAC,
- inject alignment laser on the axis of the undulators,
- inject seed laser (plan, collaboration with CEA),
- analyze beam energy.
• In case of a dog-leg, strong Q-magnets are needed to keep
achromaticity, note that the length should be compact.
• Chicane can be used as a bunch compressor.
Chicane design (tentative)
12
βｘ
βy
8
-0.05
-0.10
-0.15
4
B2
B1
B3
Undulator
B4
-0.20
0
-0.25
0
2
4
6
8
Z (m)
Input
st= 0.1 ps, 4kA gaussian bunch
en=2.0p mm mrad, DE/E=2.0e-4
Need optimization
Output
Slice values ~a few 10 % increase
Projected values a few times increase
Estimation using ELEGANT
10
12
14
Dispersion
Beta function (m)
0.00
Design example (not confirmed yet)
Using double-bend to avoid CSR effect after bending exit?
Ecsr= Erad_ret+Ecol_ret
Erad_ret is same as SR emitted
in 1/g cone.
?
With four 50 cm (R=8m) bends.
With four 49 cm (R=8m)
+ four 8cm (R=80m) bends.
FEL simulation code “SIMPLEX” (by T.Tanaka)
• 3D calculation on SASE or amplifier mode.
• Real undulator field can be used.
• Easy GUI interface to use.
• Windows, LINUX, Mac OSX.
Data input through GUI
Calculation using real undulator fields
SCSS FEL calcualtion example
Simplex
Genesis
8
Peak power (W)
10
107
106
105
104
103
102
0
5
10
15
Z (m)
20
25
Electron beam
energy
peak current
emittance
bx,y
energy spread
1 GeV
2kA
2p mmmrad
~8m
2.0e-4
Undulator
lu
K
gap
15 mm
1.3
~3 mm
Radiation
l
3.6 nm
Saturation in 25 m (5 undulator segments)