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 200mA@3.5GeV• 2009.03.07 Light reached the end of the last beamline• 2009.05.06 Open to user• 2009.07.18 Reached 300mA@3.5GeV

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 !