Bunch Length Measurements at SPEAR3 Jeff Corbett for the SPEAR3 - - PowerPoint PPT Presentation

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Bunch Length Measurements at SPEAR3 Jeff Corbett for the SPEAR3 Accelerator Group Outline 1. SLAC, LCLS, SPEAR3 and short bunch operation (low- ) 2. Streak camera measurements 3. Cross-correlation measurements 4. Summary Second DITANET

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SLIDE 1

Bunch Length Measurements at SPEAR3

Outline

  • 1. SLAC, LCLS, SPEAR3 and short bunch operation (low- )
  • 2. Streak camera measurements
  • 3. Cross-correlation measurements
  • 4. Summary

Jeff Corbett for the SPEAR3 Accelerator Group

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 2

SLAC Project M circa 1962

Stanford Linear Accelerator Center

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 3

SLAC 2-mile accelerator and SPEAR storage ring

Early view of SLAC SLAC with LCLS SPEAR circa 1972 SPEAR3 circa 2009

LCLS

SPEAR3

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

LCLS PEP-II

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SLIDE 4

Free-Electron Lasers

  • short pulse, high power, coherence

FELS Rings

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 5

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

Electron and Photon Pulse Structure: SASE Electron Photon

START MIDDLE END

…the (LCLS) X-ray pulse duration appears much shorter than the nominal 80 fs (bunch) …the 80fs mode of operation actually produces X-ray pulses of ~20-40fs (L. Young, et al, Nature 446,1 July 2010)

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SLIDE 6

Back to the SPEAR3 Light Source 3 GeV, 10nm-rad 18 DBA cells

Circa 2002

Injector

SPEAR3

Visible Diagnostic Beam Line

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 7

Achromat

SPEAR3 Accelerator Optics

x~10m y~5m

18 cell racetrack lattice

¼ ring

Single cell optics

||=20ps rms

reduce alpha  2ps rms

Double-bend Achromat

x>0 x>0

Low Emittance Low Alpha (short bunch)

x=0

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 8

2 ) sgn( 1 2 1 exp 1 z z A z z

  • I

I z I

200 400 600 800 1000 1200 100 200 300 400 500 600 700 800 900 1000

asymmetry term R2 synchroscan ~5 pixel focus

R1: 157.45ps 0.1538ps/px R2: 704.41ps 0.6879ps/px R3: 1214.60ps 1.1861ps/px R4: 1686.50ps 1.6470ps/px

screen height ps/px

Typical streak camera data

~50ps fwhm

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 9

filter change

Low-emittance optics: bunch length vs. current

Bunch current (au) time (ps) Longitudinal bunch profile

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 10

Current scan and ring impedance

note distortion Bunch current (mA) Bunch current (mA) Bunch current (mA) Bunch length Asymmetry Synchronous Phase Shift

Amplitude

Z/n=0.20, L=25nH 7.5 V/pC, R = 600 Ohm

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 11

filter change?? Amplitude

Bunch length measurements in low-alpha mode

Amplitude

( /340) Low beam current (~10-20pc , SR emission) Streak camera resolution limit ~2.4ps rms R1 range R2 range

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 12

alpha/59

Current increase

Bunch length scaling in low- mode (cont’d)

Current dependence - single-bunch

0.0001 0.001 0.01 0.1 1 10 0.1 1 10

single bunch current [ma] bunch length [ps, rms]

0.50 kHz 1.50 kHz 2.16 kHz 3.16 kHz 3.95 kHz 10.0 kHz

BESSY-II SPEAR3 ~2.4ps rms Streak camera limit

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SLIDE 13

CCD camera phosphor sweep plates

head tail

electrons photocathode mcp computer display/analysis bunch photons

head tail

Streak camera resolution issues

barrel Hamamatsu c5680

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

Trigger

  • r

119MHz

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SLIDE 14

System Calibration

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

Focus mode Glass Etalon

5-6 pixel FWHM Use 2L/c echo to determine px/ps

R1: 157.45ps 0.1538ps/px R2: 704.41ps 0.6879ps/px R3: 1214.60ps 1.1861ps/px R4: 1686.50ps 1.6470ps/px

screen height ps/px

R1 R2 R3

450550 700nm 650 600

Chromatic dispersion

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SLIDE 15

Synchroscan integrates but has ripple Triggered-scan isolates but has noise 50ms horizontal deconvolve ripple, ~1ps phase noise 20ms 10ms 5ms

fit Gaussians, histogram statistics

triggered dual-scan 500 A, low- 500 A, low-

Synchroscan, dual-scan, triggered-scan operation

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 16

Centriod, Sigma and Sum

Statistical evaluation of triggered-scan data

Single-shot fits Histograms Nominal optics Low-alpha optics

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

Centriod Sigma Sum Bursting in tail

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SLIDE 17

HorSweep (px) VerSweep (px) 100 200 300 400 500 600 700 800 900 1000 200 400 600 800 1000 5 10 15 20 25 30 35 40 45 50 20 21 22 23 time (ms) Fitted sigma p5*px2ps, (ps)

Bursting as seen on the streak camera

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 18

Horizontal single turn profile Gaussian fit (4.7mA, Alpha/21 bursting) pixels (13um*13um pixel size) pixels 100 200 300 400 500 600 700 800 900 1000 100 200 300 400 500 10 20 30 40 50 60 70 80 90 100 200 400 600 800 Fitted amp (a.u.) 10 20 30 40 50 60 70 80 90 100 500 1000 1500 2000 Fitted sigma x at source point(um) Gate number (~100us per gate)

/21 4.7mA Gate trigger freq: ~10kHz 100 gates per exposure

Bursting as seen on fast-gated camera

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 19

500us per frame 200us, from start 100us, delayed 1ms 50us, from start

Injection damping transients – longitudinal plane

De Santis/Byrd De Santis/Byrd

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SLIDE 20

x-y projection and x-t projection of injected beam x-y x-t turn #1 turn #2 turn #3 turn #4 turn #5 turn #6 Fast Gated Camera Streak Camera Fast Gated Camera Streak Camera x-y x-t

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

turns

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SLIDE 21

Goal is to produce ps x-ray pulses at MHz rates for pump/probe SLAC/Stanford PULSE Institute

SPEAR3

LCLS

Laser/SR cross-correlation bunch length measurements

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 22

Short Bunch Measurements with SR IR/THz beam line FIR interferometer/form factor CSR component/electro-optic ‘optical sampling’ in the visible (Zolotorev, et al, ALS)

FrÖhlich Steffen/Müller/Peier

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 23

Laser/ SR Cross-correlation Geometry

SR beam delay line

400nm BBO photodiode Lock-in scope ps SR pulse 50fs Ti:Sa pulse Spatial/temporal overlap Ti:Sa oscillator computer 800nm

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 24

SR Beam

visible, few ps, 1 fJ 1.28MHz

Ti:Sa Laser

0.5 J, 60fs 5.06MHz

BBO Crystal APD RF Lock-in Amp

2

Second-Harmonic in a BBO

Ti:Sa SR

1.28MHz

  • verlap integral

800nm

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 25

White light Streak camera BBO crystal APD

Plan View of Optical Bench

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 26

Laser timing and Lock-in Measurement

476MHz diode pico-motor diode 1.28MHz computer

1.28MHz SR pulse 5.1MHz laser pulse

time

…

Lock-in to 1.28MHz signal 400nm component

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 27

LE 1mA, 21.8 ps LA 1.5 mA, 8.7 ps

Bunch Profile in Low- Optics

1.5mA, 8.7 ps 86uA, 5.9 ps

0.0001 0.001 0.01 0.1 1 10 0.1 1 10

single bunch current [ma] bunch length [ps, rms]

0.50 kHz 1.50 kHz 2.16 kHz 3.16 kHz 3.95 kHz 10.0 kHz

Comparison with SC data

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 28

Profile Measurements in Low-Emittance Optics

14mA, 31 ps 1mA 21.8 ps Streak Camera Data

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

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SLIDE 29

Summary and Future Improvements

  • Low-
  • peration for short-pulse, high rep-rate x-ray beam
  • Streak camera measurements of bunch length scaling law
  • Streak camera limited by low flux, ~2.4ps synchroscan resolution
  • Developing laser/SR cross-correlation measurements (no IR port)
  • Testing different EO crystals, fiber laser
  • Use visible diagnostic beam to provide timing for pump/probe stations

Second DITANET Topical Workshop: Longitudinal Diagnostics 12-13 July 2010

Thank you!