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Simulation and Experimental Results of SSRF Top-up Operation
Haohu Li, Manzhou ZhangSSRF
Top-up Workshop, Melbourne2009.10.08
Contents
• Brief introduction of SSRF Project
• Demands of top-up operation in SSRF
• Goal of top-up operation
• Requirements for top-up operation
• Some simulation and experimental results
• Summarize
Brief introduction of SSRF Project
• SSRF is a third generation light source, the main parameters are as follows– Energy 3.5GeV– Circumference 432m– Effective Emittance ~4nm·rad– Beam Current 5mA(single bunch)/300mA(multi bunch)– Lifetime >10hours– Orbit Stability <10% of beam size– Straight Section sixteen 6.5m / four 12m
Machines In SSRF
150MeV Linac
Full Energy BoosterC=180m
3.5GeV Storage Ring
C=432m
Lattice Parameters
• 20 DBA cells, 4 superperiods• Four 12m long straight section used for
– One for injection system– One for RF system– Others for users
• Theoretical minimum emittance 1.5nm.rad• Norminal working point 22.22/11.29
Twiss Functions for 1/8 ring
Main Milestones during SSRF Construction
• 2004.12.25 Ground breaking• 2007.05.15 First beam from LINAC• 2007.10.05 First 3.5GeV beam in booster• 2007.12.24 First stored beam (3GeV) in storage ring• 2008.01.03 Reached 100mA@3GeV• 2008.05.10 Light reached the end of the first beamline• 2008.09.30 Reached [email protected]• 2009.03.07 Light reached the end of the last beamline• 2009.05.06 Open to user• 2009.07.18 Reached [email protected]
Running status for users
105.6 103.3
160.1 159
145.0
190.4
108.3
67.6 68.265.1
8896.5 95.3 94.6
87.599.2 98.9 93.9 94.7 90.4
15.125.8
32
17.7 16.1
47.636.1
11.3
34.1
16.3
0
20
40
60
80
100
120
140
160
180
200
User Operat i on(hours) Avai l abi l i t y(%) MTBF
595 people did 122 experiments in about 2 and a half months
The longest non-stop running for users -137 hours
Hardware failure during user time (05.06-07.16)
Stati st i cs of the fai l ure t i me
MPS0. 5%
Uti l i ty5%
Physi cs2%
PS20%
I nj ecti on &Extracti on
38%
RF24%
Li nac5%
Beaml i ne1%
PPS1%
Vacuum1%
Beam Di agnosti c1%
Control2%
h
Demands of Top-up Operation in SSRF
• To provide more stable beam for users– Electron orbit stability, which we have already taken a
lot of methods to keep the beam stabilized within 2~5 microns
– Heating stabililty of beamline monochromator, which must be solved by keeping beam current as stable as possible, i.e. top-up injection
• Beam current will oscillate within less than 1% level during top-up operation, that means the injection process will running frequently, mostly once per several minutes, and the users can still do experiment during this period.
Orbit vs. current
Goal of top-up operation
• Current stability– Single bunch <1%– Multibunch <0.1%
• Orbit disturbance– Stored beam oscillation <0.1mm
Requirements of Top-up Operation
To achieve a good current stability, the system must haveHigh injection efficiency >99%
High injection efficiency
• The injection efficiency of storage ring will be affected by the following conditions– Extraction beam property from booster– Injection system acceptance– Stored beam loss during injection
• For the booster, digital power supplies are used to get a stable extraction beam’s energy, slow bump magnets (100ms) and high performance septa are helpful to increase the stability of the extraction orbit.
• For the injection system of storage ring, we use collimators to limit the injection beam’s emittance, and this will also protect our insertion device with small gap.
• For the stored beam, there should have no loss during injection, if the injection elements’ performance is good enough, because of its very small beam size, just 0.3mm for 1σx.
SP1QD SP2-1QD
BP2
QFBENDKICK
BP1
BP3
SP2-2
Efficiency of the injector (15~20 minites)
Injection efficiency of Storage ring
• During injection, we measured the booster and storage ring’s dcct, injection efficiency >95%
Booster DCCT 0.74mA ~0.444nC
SR DCCT 0.3mA ~0.43nC
High injection efficiency
• The injection efficiency of storage ring will be affected by the following conditions– Extraction beam property from booster– Injection system acceptance– Stored beam loss during injection
• For the booster, digital power supplies are used to get a stable extraction beam’s energy, slow bump magnets (100ms) and high performance septa are helpful to increase the stability of the extraction orbit.
• For the injection system of storage ring, we use collimators to limit the injection beam’s emittance, and this will also protect our insertion device with small gap.
• For the stored beam, there should have no loss during injection, if the injection elements’ performance is good enough, because of its very small beam size, just 0.3mm for 1σx.
Collimator System
• Collimator system is used to protect the elements, especially small-gap IDs.
• Two collimators: horizontal and vertical
• Location : inject straight section
• Material : Ta
• Thickness : 30mm(H)/60mm(V)
Horizontal Collimator
0 50 100 150 200 250 300 350 4000
5
10
15
20
25
30
s (m)
Lo
ss R
ate
/ b
eta
X (
m)
12 14 16 18 2060
65
70
75
80
85
90
95
100
Horizontal collimator gap (mm)
Inje
ctio
n e
ffici
en
cy (
%)
95% of total lost beam are
lost on the collimator
Gap : ±14mm
0 50 100 150 200 250 300 350 400
0
2
4
6
8
10
12
14
16
s (m)
Lo
ss R
ate
/ b
eta
Y (
m)
Vertical Collimator
0 50 100 150 200 250 300 350 4000
2
4
6
8
10
12
14
16
s (m)L
oss
Ra
te /
be
taY
(m
)
In-vacuum ID( cell 15)
In-vacuum ID( cell 17)
Without V Collimator
99.5% of total lost beam are lost on the collimator
With V collimator, gap ±2.7mm
Experimental Results
Vertical Lower Part
Vertical Upper Part
Requirements of Top-up Operation
To achieve a good current stability, the system must haveHigh injection efficiency >99%Sufficient long life time, >5 hours for single bunch and >
10 hours for multibunch
Sufficient life time
• For single bunch mode, the designed beam current is 5mA. Assume the lifetime is τ, the beam will lose 1% after τ*ln(1/0.99)=0.01 τ. When τ equal 5 hours, that means we must inject electron each 3 minutes.
• For multibunch mode, the designed beam current is 300mA. In the same way, when life time equal 10 hours, the injection should be running each minute to reach ±0.1%.
Requirements of Top-up Operation
To achieve a good current stability, the system must have High injection efficiency >99% Sufficient long life time, >5 hours for single bunch and >10 hours fo
r multibunch Good diagnostic system for beam current, especially single bunch
mode, at least 50 μA resolution.
The store beam orbit stability during injection is only depends on the injection elements’ performance, such as septum’s leakage field, kickers’ jitter, kickers’ field uniformity, and the difference between four kickers, etc.
0.935
0.600
2.400
0.600
0.800
0.120
0.800
0.750 0.600
2.400
0.600
0.935
12.000m
KI K4 KI K3KI K1KI K2
Septum 1
Septum 2
Stri p
0.460
Injected Beam
Stored Beam
Injection System of SSRF storage ring
Machine acceptance
Bumped acceptance
Stored
Beam Bumped
Beam
Injected
Beam
Septum
A
Main Parameters of injection elements
NameMagnetic Length
(m)
Strength (mrad)
Field (Tesla)
Waveform Up/Down
(s )
Stability of Amplitude
Timing Jitters
Vacuum Aperture H/V (mm)
Repetition Rate
(Hz)
Kicker 1&4 0.60 4.83 0.094 4 0.5% 10ns 64/24 2
Kicker 2&3 0.60 -4.83 0.094 4 0.5% 10ns 64/24 2
Septum 1 0.80 55 0.80 60 0.2%100n
s28/12 2
Septum 2 0.80 55 0.80 60 0.2%100n
s28/12 2
Effects of Injection elements’ error
• Errors– Timing jitter of kickers– Field reproducibility– Field uniformity– Installation misalignment– Injection beam mismatch– Leakage field of septa– ……
• The first four types of errors will not only affect the injection beam, but also the stored beam. The fifth error will only affect the injection efficiency. The last one’s effect can be negligible with magnetic shielding layer on septum.
Timing jitter and field reproducibility of kickers
• The horizontal emittance of the injection beam and the stored beam is about 110 nm·rad and 4~10 nm·rad, respectively, so the field instability will mostly affect the stored beam
• The effective emittance will grow due to the power supply instability
• If the amplitude of the kicker strength is θ0, the phase is φ0, and their errors are Δθi and Δφi, respectively, the subscript i represents different kicker, then we have
B
A
Bxx
Axxx
0001
00001
sin
sin12
2
1
22
0
ii
ii aa
A
2
1
22
0
i
iB
235.1235.4765.7765.10a
Timing jitter of kickers
Timing Jitter(σ=2ns)
Horizontal orbit disturbation
RMS(μm) Maximum(μm)
1σ 70 440
2σ 110 750
3σ 130 840
4σ 130 860
5σ 130 880
6σ 130 920
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02
X (mm)
XP
(m
rad
)
0 0.5 1 1.5 2 2.5 3 3.5 4
x 10-4
0
20
40
60
80
100
120
Maximum Horizontal Disturbance (mm)
Nu
mb
er
of
Se
ed
s
Right Figure: After injection process, store beam center position at the center of injection straight (timing jitter : 2ns, seed : 1000)
Timing jitter and field reproducibility of kickers
ns2%1.00
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-0.06
-0.04
-0.02
0
0.02
0.04
0.06
X (mm)
XP
(m
rad
)
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
X (mm)
XP
(m
rad
)
ns0%1.00
-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
X (mm)
XP
(m
rad
)
ns200
1000 seeds, 3σ
Field uniformity of kickers
• This error mainly comes from the metallic coating in ceramic vacuum chamber, because the kicker’s waveform width is very short, only 4μs.
• From SLS kicker measuring result, when the average coating thickness is 3μm and waveform width is 6μs, the field uniformity will reduce to 2%, and this value is far less than 1%.
• In SSRF, the average coating thickness is about 1.5 μm, and the waveform width is 4μs, the field uniformity will better than 3%.
• This error is a system error, it will cause the stored beam disturbance, and can be reduced by adjusting their strength.
a
-5.04 -5.02 -5 -4.98 -4.96 -4.94 -4.92 -4.9 -4.88 -4.86-4.75
-4.7
-4.65
-4.6
-4.55
KIK2 Strength (mrad)
KK
I3 S
tre
ng
th (
mra
d)
0.0883
0.156
0.2240.293
0.361
0.429
0.497
0.565
0.633
0.701
0.769
0.837
0.905
0.973
1.52
1.59
1.65
1.72
1.79
1
2
3
4
5
6
-5.5 -5.4 -5.3 -5.2 -5.1 -5
-4.55
-4.5
-4.45
-4.4
-4.35
-4.3
-4.25
-4.2
-4.15
-4.1
KIK2 Strength (mrad)
KIK
3 S
tre
ng
th (
mra
d)
0.215
0.384
0.553
0.553
0.722
0.8911.06 1.23
1.4
1.57
1.74
1.9
2.07
2.24
2.41
2
4
6
8
10
12
14
16
a = 2% a = 5%
Simulation ResultsSimulation Results
Eddy current effect Before correction After correction KIK2 Strength KIK3 Strength
1% 0.4mm 11μm -4.925mrad -4.725mrad
2% 0.8mm 20μm -5.02mrad -4.62mrad
5% 2.0mm 47μm -5.305mrad -4.305mrad
10% 4.0mm 128μm -5.78mrad -3.78mrad
Installation Misalignment
-20 -15 -10 -5 0 5 10 15 20-3
-2
-1
0
1
2
3
Y (m)
YP
(ra
d) 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
0
50
100
150
200
250
300
350
400
Effective vertical emittance (nm.rad)
Num
ber
• Only roll tolerance of kickers can effect on the stored beam, this is a system error, can not be reduced.
• Assume the roll tolerance is 0.2mrad, 3σ,1000 seeds
0 5 10 15 20 250
20
40
60
80
100
120
140
Maximum vertical amplitude (m)
Num
ber
Commissioning ResultsCommissioning Results
TBT data at BPM(1,2), where beta function is about 12m in both plane
Injection Beam Mismatch
5 10 15 20 25 30 35 40-15
-10
-5
0
5
10
15
50
50 80
8090
90
95
99
beta (m)
alp
ha
-28 -27 -26 -25 -24 -23 -22-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
95989999.5
99.8
99.9
99.95
x (mm)
xp (
mra
d)
Injection efficiency with injection beam twiss parameter
Injection efficiency with injection beam orbit error
Requirements of Top-up Operation
To achieve a good current stability, the system must have High injection efficiency >99% Sufficient long life time, >5 hours for single bunch and >10 hours fo
r multibunch Good diagnostic system for beam current, especially single bunch
mode, at least 50 μA resolution.
The store beam orbit stability during injection is only depends on the injection elements’ performance, such as septum’s leakage field, kickers’ jitter, kickers’ field uniformity, and the difference between four kickers, etc.
The control system must be able to estimate when start and stop the injection process, which bucket need to be refill, and how many electrons need to be filled, etc.
Other considerations of top-up injection and operation
• Control system– Running automatically– Reading beam current and comparing it with the current limit– Choosing buchet and setting timing system– Switching on/off the injection process– Send signal to users
• Safety problem: Because the users will still work during injection, the safety of the optical elements must be very carefully studied.
• Precise model of storage ring : the necessary condition for autocontrol during top-up operation
ProblemsProblems
• BPM offset will change with– Beam current – Bunch current distribution– Some unknown reasons
Filling Pattern
Initial pattern After 12 hours
COD Difference between different filling pattern20 buckets vs. 40 buckets
COD Difference between different filling pattern100 buckets vs. 200 buckets
SOFB results on 2008.06.04
VerticalHorizontal
The last orbit difference with the initial value
Total SOFB time: 5.5hours
BPM number: 135
Eigen Values: 60/60 (H/V)
Orbit drift in the last 5.5 hours
H
V
Beam Current and Lifetime in the 5.5 hours
SOFB results started from 2008.12.01 23:00, 14 hours
80 个 BPM
Eigen values
H : 40
V : 60
SOFB results started from 2008.12.01 23:00, 14 hours
Effects of septum’s leakage field
Septum 1&2
BPM2 of Cell 01~04
100 times TBT data
Some Unknown reasons
Other BPMs
Summarize
• During injection period, the stored orbit disturbance should be less than 130μm(H)/10 μm(V) (rms value) , now the best case is 80μm(H)/30 μm(V) (max. value)
• Beam current stability can achieve 1% ( single bunch ) / 0.1% ( multi bunch ).
• With collimator system, the injection efficiency can achieve 99%. (starting point behind collimator)
• There still have a lot of job need to do before the real top-up operation running.
Thank you !