Beam Break Up (BBU)
Download
Report
Transcript Beam Break Up (BBU)
Energy recovery
linacs
Sverker Werin
MAX-lab
8 July 2003
1
• Source development
• What is an ERL?
Energy recovery
linacs
• Quality of radiation
• Special ERL topics
• Instabilities and limitations
Sverker Werin
MAX-lab
• Challenges and development
• ERLs yesterday, today and tomorrow
8 July 2003
2
Path of development
Have today
Light sources
• Repetition rate
• 1st generation
parasitic SR on high energy physics
storage rings
• 2nd generation
dedicated bending magnet sources
• 3rd generation
dedicated undulator sources
• 4th generation….
• Stability
• Tunability
• Polarisation
• Brilliance – average/peak
Need in the future
?
• Coherence
• Power
ERL
3.5th gen
FEL
#3
• Fs pulses
• Diffraction limited radiation
• Brilliance – average/peak
S. Werin
3.5 generation storage ring
Gives us
• Coherence
• Power
• Pulse slicing fs pulses
• Some diffraction limited radiation
• Brilliance – average/peak
#4
S. Werin
http://www.soleil.u-psud.fr
http://www.diamond.ac.uk
Free electron laser
Gives us
• Coherence
• Power
• Fs pulses
• Diffraction limited radiation
• Brilliance – average/peak
• Low repetition rate
#5
S. Werin
http://www.bessy.de/publications/01.felscientific/sc.html
Energy Recovery Linac
Gives us
• Coherence
Cornell ERL
• Power
D. Bilderback, SRN 2/27/01.
• Fs pulses
• +Diffraction limited radiation
• Brilliance – average/peak
• Medium repetition rate
Articles on "ERL" or "Energy Recovery Linac"
40
35
30
M. Tigner, Nuovo
Cimento 37 (1965)1228.
25
20
15
10
5
S. Werin
PAC 03
EPAC 02
PAC 01
EPAC 00
PAC 99
EPAC 98
#6
PAC 97
EPAC 96
0
What is an ERL?
Linac
injection
#7
S. Werin
What is an ERL? Step 2
• Emittance defined by
source/gun ( not ring
equilibrium)
<=0.1 nmRad
• Brilliance >= storage rings
• Pulse length small (not
ring equilibrium)
< 100 fs
• SC linac – save RF
power, independent of
current
• CW operation (gun limit)
Opposite phase
Deceleration
Energy given back
to linac structure and
stored there
#8
S. Werin
KHz-MHz
• Low dump energy, less
radioactivity
<10 MeV
Linac power
Pwall
Shunt
impedance
Eˆ L
Zs
Loading of a cavity
1,2
Q-value
0,8
t
E E0 1 e Q
Field
W
1
Q Pwall
0,6
0,4
0,2
QNC ~ 1*104
QSC-TESLA ~ 3*109
#9
S. Werin
0
0
0,5
1
1,5
2
Time
2,5
3
3,5
4
Brilliance
Flux
photons
s 0.1% BW A
Flux
Brilliance
4 2 x x ' y y '
x x2 r2
x ' x2' r2'
# 10
S. Werin
What counts
To compare
Peak brilliance
Average brilliance
During the peak of
a bunch
Forever or during a
macro pulse from
the accelerator
Brilliance
Brilliance
Flux
4 2 x x ' y y '
x x2 r2
x ' x2' r2'
Peak brilliance
Average brilliance
1E+35
1E+27
TESLA
TESLA
1E+33
Peak Brilliance (ph/s*mRad^2*mm^2*0.1%BW)
1E+29
1E+27
USRLS
1E+25
ESRF
Diamond
Cornell
ERL
SPring8
1E+23
APS
# 11
1E+19
1E+1
1E+23
USRLS
LCLS
1E+21
ESRF
Cornell
ERL
SPring8
Diamond
1E+19
APS
1E+17
BESSY II
BESSY II
1E+2
1E+3
1E+4
Energy (eV)
S. Werin
Average Brilliance (ph/s*mRad^2*mm^2*0.1%BW)
LCLS
1E+31
1E+21
TTF
1E+25
TTF
1E+5
1E+6
1E+15
1E+1
1E+2
1E+3
1E+4
Energy (eV)
1E+5
1E+6
Diffraction limit
Flux
Brilliance
4 2 x x ' y y '
x'
2
x'
r r
2
r'
2
100
Emittance (nmRad)
x x2 r2
Diffraction emittance -
10
1
0,1
0,01
0,0E+00
5,0E+02
1,0E+03
Photon energy (eV)
# 12
S. Werin
1,5E+03
2,0E+03
Emittance comparison
Horisontal emittance
Ring
Emittance
g
Emittance 1
g
# 13
S. Werin
2
periodicity
ERL/Linac
Vertical emittance
Ring
3
vert ≈ 0.05 hor
ERL
vert= hor
Emittance comparison
7
Ring
6
g
M
Vertical
emittance
Horisontal
emittance
2
Ring
ERL
ESRF
APS
SPring8
ERL-1
M4-X
M4-SoftX
ALS
Diamond
BESSY II
Soleil
USRLS
3
Emittance - nmRad
5
4
3
ERL/Linac
1 mm mRad
2
1
1
g
0
0
# 14
2
4
6
Energy (GeV)
S. Werin
8
10
Pulse length
Storage ring
10 ps
Lifetime sacrifice
+ bunch slicing
50 fs
Low flux, simple
Linac (FEL, ERL)
~ 20 fs Photo cathode laser, space charge,
CSR (coherent synch.rad.), slippage
# 15
S. Werin
Quick duty
Please
talk!
Discuss with your neighbour
A 20 fs electron bunch passes a 100 period
long undulator producing radiation at a
wavelength of 60 nm.
How long is the radiation pulse?
The radiation from one e- consists of a wave train with
100 periods at 60 nm 100*60 nm = 6*10-6 m
The length in time is 6*10-6/c = 6*10-6/3*108 = 20 fs
Add the pulse length
and the total length will be 20 + 20 = 40 fs
# 16
S. Werin
15
30
45
60
Energy savings …?
A 100 mA 5 GeV electron
beam carries 500 MW
power.
Stornorrfors powerstation
591 MW @ 1000 m3/s
Save energy!
# 17
S. Werin
Energy savings go superconducting
LBL LUX proposal
600 MeV linac – 4 recirculations
10 KHz
# 18
S. Werin
NC
SC
RF-power peak
240 MW
0.288 MW
RF-power average
6 MW
0.288 MW
Cooling power
0
~3.5 MW
6 MW
3.8 MW
Energy savings (nasty version)
Cornell ERL2 - 5 GeV 100 mA
v.
ESRF - 5 GeV 200 mA
# 19
S. Werin
Cornell
ESRF
RF-power peak
1.1 MW
2.6 MW
RF-power average
1.1 MW
2.6 MW
Cooling power
16.4 MW
0
17.5 MW
2.6 MW
Radiation savings …?
Dump beam powers
ERL
100 mA
5 GeV
Recovery
Dump @ 10 MeV
1 MW
linac
NO recovery
Dump @ 5 GeV
500 MW
# 20
S. Werin
ESRF
200 mA, 5 GeV
24 hours, c 850 m
31 mW
Limitations
Space charge
effects
Wakefields
Increase
current
Energy spread
HOMs
Shorter
bunches
Emittance
increase
Heat up
of SC cavities
CSR
# 21
S. Werin
Cooling
power
increase
Beam Break Up (BBU)
Displacement of the bunch
due to transverse wakefields
induced by a previous bunch
beeing off center.
# 22
S. Werin
Damp modes
Good alignment
Coherent Synchrotron Radiation
A sufficiently short bunch
will radiate coherently.
The radiation from the tail
can irradiate the head of
the bunch.
Energy spread
Emittance growth if
dispersion
Cure:
Longer bunches, less current
# 23
Shielding, larger radius
S. Werin
Challenges
# 24
S. Werin
Guns
► CW
Optics in arcs
► Multi energy, CSR
Control of RF
► The beam ”runs” the RF
Beam loss
► Messes up RF
Instabilities (BBU…)
► Limits current
HOM cooling
► More power to SC cooling
Around the world
1960
M. Tigner, Nuovo Cimento 37 (1965)1228.
1970
MUSL Univ of Illinois, 1977
1980
SCA, Stanford, 1986
1990
S-DALINAC, 1990
CEBAF, 1995
IR FEL Jlab, 1999
JAERI, 2002
# 25
S. Werin
2000
LUX (LBL)
Cornell
PERL (NSLS)
4 GLS (Daresbury)
ERLSYN (Erlangen)
KEK
…
MUSL-2 – Univ. Of Illinois
# 26
S. Werin
Stanford SCA
First energy recovery
T.I. Smith, et al, NIM A 259 (1987) 1-7
50 MeV
# 27
S. Werin
JAERI – ERL + FEL
17 MeV
5 mA
In operation
# 28
S. Werin
N. Nishimori et.al., EPAC 2002, Paris
S-DALINAC - Darmstadt
130 MeV
# 29
S. Werin
http://linac.ikp.physik.tu-darmstadt.de/linac/introduction.html
Jlab FEL
Jefferson Lab
Newport News, VA
IR Demo FEL
In operation since 1999
40 MeV
5 mA
FEL upgrade
2003 160 MeV
10 mA
# 30
http://www.jlab.org/FEL/feldescrip.html
S. Werin
MARS
6 GeV
Multipass
Accelerator
Recuperator
Source
undulator
undulator
Novosibirsk
undulator
undulator
Linac 700 MeV
Linac
Gun
Injector
Dump
# 31
G. Kulipanov et.al. SRI 2001, ERL workshop
S. Werin
CEBAF
CEBAF 6 GeV
(12 GeV upgrade)
Jefferson Lab
Newport News, VA
# 32
S. Werin
http://www1.jlab.org/ul/jpix/high/upgrade_187.jpg
LUX - LBL
Multi-user facility proposal
Repetition rate 10 kHz
Pulse length
< 100 fs
Current
10 µA
3 GeV proposal
# 33
http://jncorlett.lbl.gov/FsX-raySource/
S. Werin
Cornell-Jefferson ERL
Proposal
Cornell, Ithaca NY
Energy 100 MeV phase I
5 GeV phase II
Cornell ERL
Current 10/100 mA
# 34
D. Bilderback, SRN 2/27/01.
S. Werin
PERL
NSLS, Long Island
# 35
J. Murphy, SRI 2001, ERL workshop
S. Werin
4 GLS
Daresbury, UK
# 36
http://www.4gls.ac.uk/
S. Werin
ERLSYN
Erlangen, Germany
3.5 GeV
# 37
S. Werin
http://www.erlsyn.uni-erlangen.de/
KEK ERL
Photon Factory - KEK
Energy
2.5 ~ 5.0 GeV
Beam Current
~100 mA
Horizontal Emittance
~0.01 nmRad
Bunch Length
1 ps ~ 100 fs
# 38
http://conference.kek.jp/JASS02/23_harada.pdf
S. Werin
Summary
ERLs will give us
Fs pulses (some tricks needed)
CW (almost) KHz-MHz repetition rate
Brilliance ≥ new rings above 5 GeV
Diffraction limited < 2-5 KeV = ”Ultimate source”
Reduced radiation from dump (v. linacs)
Proof of principle done
But
Many new proposals, especially in the US
•
Small energy savings
Compact CW driver for FEL
•
Instabilities limits current
•
HOMs limits short bunches
Diffraction
limit
Coherence
Fs
pulses
Multi
user
Brilliance,
average
Brilliance,
peak
Rep.
rate
-hor, +vert
-
-
+
0
-
+
FEL
0
+
+
0
0
+
-
ERL
0
-
+
+
0
-
0
Storage ring
# 39
S. Werin
END
40