Time-Resolved Energy Spread Studies at the ANKA …accelconf.web.cern.ch/AccelConf/ipac2017/talks/moocb1...Measurement principle 5 2017/05/15 Benjamin Kehrer - Time-resolved energy

0 2017/05/15 Benjamin Kehrer - Time-resolved energy spread studies at theANKA storage ring

KIT

Institute for Beam Physics and Technology (IBPT)

Time-resolved energy spread studies at theANKA storage ring

Benjamin Kehrer, E. Blomley, M. Brosi, E. Bründermann, N. HillerA.-S. Müller, M. Nasse, P. Schütze, J. L. Steinmann, M. SchedlerM. Schuh, P. Schönfeldt, M. Schwarz, N. Smale

KIT – The Research University in the Helmholtz Association www.kit.edu

Project is funded by the FederalMinistry of Education and Researchunder contract number 05K16VKA

Outline


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Introduction

Setup and DAQFast-gated intensified camera (FGC)Schottky diodes + DAQ

Synchronous measurements

Short bunch-length bursting

Summary and outlook

Micro-bunching instabilities


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Self-interaction of bunch with its own field

Deformation of longitudinal phase spaceOccurs above the bursting thresholdCSR emission (THz range) in bursts



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Self-interaction of bunch with its own fieldDeformation of longitudinal phase space

Occurs above the bursting thresholdCSR emission (THz range) in bursts

−5 0 5Position (σz, 0)

−6

−4

−2

0

2

4

6

Ener

gy (σ

E,0)

0

5

10

15

20

25

Char

ge D

ensit

y (a

rb. u

nits

)


−6

−4

−2

0

2

4

6

Ener

gy (σ

E,0)

0

5

10

15

20

25

Char

ge D

ensit

y (a

rb. u

nits

)



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Self-interaction of bunch with its own fieldDeformation of longitudinal phase spaceOccurs above the bursting threshold

CSR emission (THz range) in bursts


−6

−4

−2

0

2

4

6

Ener

gy (σ

E,0)

0

5

10

15

20

25

Char

ge D

ensit

y (a

rb. u

nits

)


−6

−4

−2

0

2

4

6

Ener

gy (σ

E,0)

0

5

10

15

20

25

Char

ge D

ensit

y (a

rb. u

nits

)



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Self-interaction of bunch with its own fieldDeformation of longitudinal phase spaceOccurs above the bursting thresholdCSR emission (THz range) in bursts


−6

−4

−2

0

2

4

6

Ener

gy (σ

E,0)

0

5

10

15

20

25

Char

ge D

ensit

y (a

rb. u

nits

)


−6

−4

−2

0

2

4

6

Ener

gy (σ

E,0)

0

5

10

15

20

25

Char

ge D

ensit

y (a

rb. u

nits

)

0 2 4 6 8Time (ms)

0

50

100

150

200

250

300

Det

ecto

r sig

nal (

mV)

Examples of previous studies


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MeasurementsEnergy spread above bursting threshold→ Increases with bunch current1

Energy spread and microwave radiation→ Same modulation period length

Simulation: Bunch length and CSR→ Same modulation period length

Idea: Time-resolved energy spread studies with single-turn resolutionand benchmark against CSR

1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).



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Energy spread and microwave radiation→ Same modulation period length2

Simulation: Bunch length and CSR→ Same modulation period length


1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).2U. Arp et al., Phys. Rev. ST Accel. Beams 4, 054401 (2001).



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Simulation: Bunch length and CSR→ Same modulation period length3


1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).2U. Arp et al., Phys. Rev. ST Accel. Beams 4, 054401 (2001).3R. Warnock et al., Nucl. Instrum. Meth. A561, 186 (2006).



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Simulation: Bunch length and CSR→ Same modulation period length3


1K Bane, K. Oide, M. Zobov, SLAC-PUB-11007 (2005).2U. Arp et al., Phys. Rev. ST Accel. Beams 4, 054401 (2001).3R. Warnock et al., Nucl. Instrum. Meth. A561, 186 (2006).

ANKA


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Synchrotron light source at KITCircumference: 110.4 mBunch spacing: 2 nsRegular low-αc runs→ Short bunchesStudies of micro-bunchinginstabilities

Measurement principle


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Energy spread σδMeasure the horizontal bunch size σx in dispersive section of storage ring

σδ =1

Dx

√σ2

x −βx · εx

Single turn base?→ Use a fast-gated intensified camera

CSR

Fast THz detectors: Schottky diodesIn-house developed DAQ (KAPTURE)

Synchronisation

Hardware synchronisation schemeTriggered beam based calibration



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σδ =1

Dx

√σ2

x −βx · εx


CSRFast THz detectors: Schottky diodesIn-house developed DAQ (KAPTURE)

Synchronisation

Hardware synchronisation schemeTriggered beam based calibration

M. Brosi, THOBA1



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σδ =1

Dx

√σ2

x −βx · εx


CSRFast THz detectors: Schottky diodesIn-house developed DAQ (KAPTURE)

SynchronisationHardware synchronisation scheme4

Triggered beam based calibration

M. Brosi, THOBA1

4B. Kehrer et al.; IPAC’16 (MOPMB014).

Fast-gated intensified camera (FGC)


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Setup at visible light diagnostics beamline5,6

Based on previous works of J. Corbett, W. Cheng7 and A. Fisher8

5P. Schuetze et al., IPAC’15 (MOPHA039).6B. Kehrer et al., IPAC’15 (MOPHA037).7W. Cheng et al., PAC’09 (TH6REP032).8A. Fisher et al., AIP Conference Proceedings (Vol. 868, No. 1, pp. 303-312).



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CameraAndor iStar 340TGate width: 1.55 ns FWHMGate separation: > 6 turns (500 kHz)




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Mirror7 mm apertureGalvo drive




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Mirror7 mm apertureGalvo drive

Drawback: compromise betweenresolution and time rangeIdeal: Continuous turn-by-turn data


FGC: Data analysis


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FGC raw image

Determine spot size → 2D Gaussian fitsTiming calibration

FGC: Data analysis


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FGC raw imageDetermine spot size → 2D Gaussian fits

Timing calibration

FGC: Data analysis


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FGC raw imageDetermine spot size → 2D Gaussian fits

Timing calibration

Raw data 2D fit

FGC: Data analysis


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FGC raw imageDetermine spot size → 2D Gaussian fitsTiming calibration

Raw data 2D fit

FGC: Data analysis


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FGC raw imageDetermine spot size → 2D Gaussian fitsTiming calibration

Raw data 2D fit

Schottky diodes + KAPTURE


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Required: CSR intensity once per bunch and turn

Detectors: Schottky barrier diodes

Room temperatureResponse time < 200 ps50 GHz up to 1 THz + narrowband detectorsCommercially available (ACST, VDI)

DAQ: KAPTURE

In-house developed DAQ system9

4 ADC with turn-by-turn and bunch-by-bunch capability (sampling with fixedphase)Continuous streaming

9M. Caselle et al., Journal of Instrumentation 12, C01040 (2017).



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Detectors: Schottky barrier diodesRoom temperatureResponse time < 200 ps50 GHz up to 1 THz + narrowband detectorsCommercially available (ACST, VDI)

DAQ: KAPTURE

In-house developed DAQ system9





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Detectors: Schottky barrier diodesRoom temperatureResponse time < 200 ps50 GHz up to 1 THz + narrowband detectorsCommercially available (ACST, VDI)

DAQ: KAPTUREIn-house developed DAQ system9



Horizontal bunch size and CSR: Example I


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0 2 4 6 8Time (ms)

7580859095

100

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

050

100150200250300

Det

ecto

r sig

nal (

mV)



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0 2 4 6 8Time (ms)

7580859095

100

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

050

100150200250300

Det

ecto

r sig

nal (

mV)

Energy spread with same modulation pattern as CSR



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0 2 4 6 8Time (ms)

7580859095

100

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

050

100150200250300

Det

ecto

r sig

nal (

mV)

Energy spread with same modulation pattern as CSR

Energy spread rises

at onset of burst

Horizontal bunch size and CSR: Example II


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0 2 4 6 8Time (ms)

70727476788082

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

0

200

400

600

800

Det

ecto

r sig

nal (

mV)



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0 2 4 6 8Time (ms)

70727476788082

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

0

200

400

600

800

Det

ecto

r sig

nal (

mV)

Energy spread decreases



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0 2 4 6 8Time (ms)

70727476788082

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

0

200

400

600

800

Det

ecto

r sig

nal (

mV)


CSR increases



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0 2 4 6 8Time (ms)

70727476788082

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

0

200

400

600

800

Det

ecto

r sig

nal (

mV)


CSR increases

Energy spread

reaches limit



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0 2 4 6 8Time (ms)

70727476788082

FGC

spo

t siz

e (p

x)

0 2 4 6 8Time (ms)

0

200

400

600

800

Det

ecto

r sig

nal (

mV)


CSR increases

Energy spread

reaches limit

Onset of next burst

Horizontal bunch size and CSR: Example III


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0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

FGC

spo

t siz

e (p

x)

0.0 0.1 0.2 0.3 0.4Time (ms)

0

200

400

600

Det

ecto

r sig

nal (

mV)

Study in more detail → 24 turns gate separation, 500 µs time range



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0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

FGC

spo

t siz

e (p

x)

0.0 0.1 0.2 0.3 0.4Time (ms)

0

200

400

600

Det

ecto

r sig

nal (

mV)

CSR negligible




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0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

FGC

spo

t siz

e (p

x)

0.0 0.1 0.2 0.3 0.4Time (ms)

0

200

400

600

Det

ecto

r sig

nal (

mV)

CSR negligible

CSR starts to increase→ sub-structures




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0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

FGC

spo

t siz

e (p

x)

0.0 0.1 0.2 0.3 0.4Time (ms)

0

200

400

600

Det

ecto

r sig

nal (

mV)

CSR negligible


Sub-structures too small

to increase bunch size




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0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

FGC

spo

t siz

e (p

x)

0.0 0.1 0.2 0.3 0.4Time (ms)

0

200

400

600

Det

ecto

r sig

nal (

mV)

CSR negligible




Minimum energy spread




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0.0 0.1 0.2 0.3 0.4Time (ms)

727476788082

FGC

spo

t siz

e (p

x)

0.0 0.1 0.2 0.3 0.4Time (ms)

0

200

400

600

Det

ecto

r sig

nal (

mV)

CSR negligible




Minimum energy spread

Onset of next burst


Bursting threshold


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0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

66

68

70

72

74

FGC

spo

t siz

e (p

x)

Bursting thresholdMean spot size

Bursting threshold


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0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

66

68

70

72

74

FGC

spo

t siz

e (p

x)


Microbunching instabilities→ Energy spread increase

Bursting threshold


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0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

66

68

70

72

74

FGC

spo

t siz

e (p

x)



Energy spread

constant

Bursting threshold


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0.2 0.3 0.4 0.5 0.6 0.7 0.8Bunch current (mA)

66

68

70

72

74

FGC

spo

t siz

e (p

x)



Energy spread

constant

But: Not always the case

“Short bunch-length bursting”


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Simulations predicted weak instability below the bursting threshold10

Measured on CSR at ANKA11 for αc ≤ 2.64 · 10−4

Instability would lead to energy spread increase

10K. Bane et al., Phys. Rev. ST Accel. Beams 13, 104402 (2010).11M. Brosi et al., IPAC’16 (TUPOR006).



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Bursting threshold





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Bursting threshold

Short bunch-

length bursting





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Bursting threshold

Short bunch-

length bursting





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0.1 0.3 0.5 0.7Bunch current (mA)

65

70

75

80

85

90

FGC

spo

t siz

e (p

x)




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0.1 0.3 0.5 0.7Bunch current (mA)

65

70

75

80

85

90

FGC

spo

t siz

e (p

x)


0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Bunch current (mA)

62

63

64

65

66

67

FGC

spo

t siz

e (p

x)




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0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Bunch current (mA)

62

63

64

65

66

67

FGC

spo

t siz

e (p

x)


16 ≤ Ib ≤ 40µA

Energy spread

increase



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0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Beam current (mA)

62

63

64

65

66

67

FGC

mea

n sp

ot s

ize

(px)

0

20

40

60

80

100

120

Fluc

tuat

ion

of T

Hz

dete

ctor

sig

nal (

mV)

16 ≤ Ib ≤ 40µA

Energy spread

increase



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0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Beam current (mA)

62

63

64

65

66

67

FGC

mea

n sp

ot s

ize

(px)

0

20

40

60

80

100

120

Fluc

tuat

ion

of T

Hz

dete

ctor

sig

nal (

mV)

16 ≤ Ib ≤ 40µA

Energy spread

increase

Coincides with

CSR increase



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0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10Beam current (mA)

62

63

64

65

66

67

FGC

mea

n sp

ot s

ize

(px)

0

20

40

60

80

100

120

Fluc

tuat

ion

of T

Hz

dete

ctor

sig

nal (

mV)

16 ≤ Ib ≤ 40µA

Energy spread

increase

Coincides with

CSR increase

→ Signature of short-bunch length bursting

Acknowledgements


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KIT THz-Team (from IBPT, IMS, IPE, IPS and LAS):M. Balzer, E. Blomley, T. Boltz, A. Borysenko, M. Brosi, E. Bründermann,M. Caselle, C. Chang*, N. Hiller, S. Höninger, M. Hofherr, E. Huttel, K.S. Ilin,V. Judin*, M. Klein*, S. Marsching, Y.-L. Mathis, M.J. Nasse, G. Niehues,A. Plech, J. Raasch, P. Rieger*, L. Rota, R. Ruprecht, M. Schedler,A. Scheuring, P. Schönfeldt, M. Schuh, P. Schütze*, M. Schwarz, M. Siegel,N.J. Smale, B. Smit, J. Steinmann, P. Thoma*, M. Weber, S. Wuensch, M. Yan,and A.-S. Müller*THz-Alumni

For interesting discussions, good ideas and a lot of fun:F. Caspers (CERN), S. Khan (DELTA), P. Peier, B. Steffen (DESY),H.-W. Hübers, A. Semenov (DLR), P. Kuske, G. Wüstefeld (HZB),V. Schlott (PSI) ,Y. Cai, J. Corbett, R. Warnock (SLAC), S. Bielawski, C. Evain,E. Roussel, C. Szwaj (U. Lille)

Summary


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Fast-gated intensified camera versatile setup for energy spreadstudies

Synchronous measurementsCoherent synchrotron radiation (CSR)Horizontal bunch size → energy spread

For certain beam currents and machine parameters→ Energy spread with same modulation frequency as CSR burstsShort bunch-length bursting (weak instability)→ Energy spread increase

Next stepsContinuous sampling and data streamingFor CSR already possible (KAPTURE)Using a 256-pixel line array for turn-by-turn sampling of a single bunchLongitudinal bunch profile: Electro-Optical Spectral DecodingHorizontal bunch profile: Replace FGC to overcome resolution limit

Summary


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Fast-gated intensified camera versatile setup for energy spreadstudiesSynchronous measurements

Coherent synchrotron radiation (CSR)Horizontal bunch size → energy spread



Summary


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For certain beam currents and machine parameters→ Energy spread with same modulation frequency as CSR bursts

Short bunch-length bursting (weak instability)→ Energy spread increase


Summary


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Summary


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Thank you for your attention!


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Thank you for your attention!

Horizontal planeCourtesy Paul Schütze

Documents

Time-Resolved Energy Spread Studies at the ANKA …accelconf.web.cern.ch/AccelConf/ipac2017/talks/moocb1...Measurement principle 5 2017/05/15 Benjamin Kehrer - Time-resolved energy