W.S. Graves 2002 Berlin CSR workshop 1

Microbunching and CSR experiments at BNL’s Source Development Lab

William S. Graves

ICFA CSR Workshop

Berlin, Jan., 2002

W.S. Graves 2002 Berlin CSR workshop 2

SDL FacilitySDL Facility

1.6 cell gun with copper cathode

75 MeV

Bend

50 m

5 MeV

Bend

DumpDump

IRinterferometer

Time domainmeasurements

Undulators Linac tanks

200 MeV

Bunch compressor

30 mJ, 100 fsTi:Sapphire laser

Goal is to reach deep UV wavelength using High Gain Harmonic Generation (HGHG) process seeded by conventional laser for full longitudinal coherence.

Currently commissioning undulator with SASE at 400 nm.

W.S. Graves 2002 Berlin CSR workshop 3

Tank 1Tank 2Tank 4 Tank 3

Chicane

Kly AKly C Kly B

1.6 cell gun with copper cathode

Pop 14 YAG

DUVFEL AcceleratorDUVFEL Accelerator

45 MW Thompson Klystrons

197 MeV 137 MeV 77 MeV 40 MeV

Bend 3m S-band tanks

25 m

30 mJ, 100 fs Ti:Sapphire laser

5 MeV

Coherent IR detector

OTR screen can intercept dipole

radiation and not beam

Slice quad scanMatching triplet

W.S. Graves 2002 Berlin CSR workshop 4

Technical DataGun energy: 5.37 MeV

Gradient: 114 MV/m.

E-beam parameters at chicane entrance: Emitnx = 1.08 um, Alphax = -0.78, Betax = 3.1 m, Emitny = 1.30 um, Alphay = -1.78, Betay = 3.1 m

Initial phase: leading edge of beam at 30 degrees from phase of zero crossing.

RMS laser size on cathode: 0.695 mm hor, 0.640 mm ver.

Charge: 50 pC

Pop14: pixel size: 28.8 um (all electron beam profiles are from pop14), image size: 640 X 480, dispersion: 1.1 m

Cathode pix.el size: 13.75 um

Linac gradient approx. 11.89 MV/m.

Final max energy: 76.7 MeV

Chicane angle at 50 A, 75 MeV: .2097 rad

100 200 300 400 500 600

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SDL data from 1/8/2002

-2 -1.5 -1 -0.5 0 0.5 1 1.5 200.10.20.30.40.50.60.70.80.9

1

Hor. Position (mm)

Inte

nsit

y (A

.U.)

File: lasera, Hor. RMS width = 0.695 mm

-2 -1.5 -1 -0.5 0 0.5 1 1.5 200.10.20.30.40.50.60.70.80.9

1

Ver. Position (mm)

Inte

nsit

y (A

.U.)

File: lasera, Ver. RMS width = 0.64 mm

UV laser virtual cathode image

Horizontal projection

Vertical projection

-3 -2 -1 0 1 2 30

0.020.040.060.080.1

0.120.140.160.18

Time (ps)

Det

ecto

r (m

V)

File: CC010822, RMS length = 1.26 ps

UV laser time profile

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50

510

1520

2530

35

Time (ps)

Cur

rent

(A

)

File: rfplus01, RMS length = 0.763 ps

Ebeam time profile

W.S. Graves 2002 Berlin CSR workshop 5

Energy spectrum

measurement

L1

L2

L3

L4

L3 off

Chicane varies from 0 cm < R56 <

10.5 cm

L2 phase varies,

amplitude constant

L1 phase = 0, amplitude constant

L4 off

L1

L2

L3

L4

L1

L2

L3

L4

RF zero-phase time

profile

L3 phase = +90, amplitude varies (removes chirp

from L2)

L4 phase = -90, amplitude varies (adds known chirp)

L2 phase varies,

amplitude constant

L1 phase = 0, amplitude constant

T. Smith method time

profile

Chicane varies from 0 cm < R56 <

10.5 cm

Chicane set for R56 ~ 9

cm

L3 off

L4 phase = -90, amplitude ~

1/R56

L1 phase = 0, amplitude constant

L2 phase varies,

amplitude constant

W.S. Graves 2002 Berlin CSR workshop 6

72.2 72.4 72.6 72.8 73 73.2

Energy (MeV)

RMS width = 151 keV

74.2 74.4 74.6 74.8 75 75.2

Energy (MeV)

RMS width = 90.1 keV

75.6 75.8 76 76.2 76.4 76.6

Energy (MeV)

RMS width = 16.6 keV

76.2 76.476.6 76.8 77 77.2

Energy (MeV)

RMS width = 74.6 keV

74.4 74.6 74.8 75 75.2 75.4

Energy (MeV)

RMS width = 188 keV

Energy spectrum measurement with chicane off.

L1

L2

L3

L4

L3 off

R56 = 0 cm

L2 phase varies,

amplitude constant

L1 phase = 0, amplitude constant

L4 off

Pop 14 YAG Images from Pop 14 at varying L2 phase and and chicane

off. Energy spectrum is modified by CSR in chicane.

L2 = -16 deg. L2 = -8 deg. L2 = 0 deg. L2 = +16 deg. L2 = +28 deg.

W.S. Graves 2002 Berlin CSR workshop 7

L2 = -32 deg. L2 = -28 deg. L2 = -24 deg. L2 = -20 deg. L2 = -16 deg.

L2 = -12 deg. L2 = -8 deg. L2 = -4 deg. L2 = 0 deg. L2 = +4 deg.

L2 = +8 deg. L2 = +16 deg. L2 = +24 deg. L2 = +28 deg.

Energy profiles at many L2 phases

L2 phase varying. Chicane, L3, and L4 off.

W.S. Graves 2002 Berlin CSR workshop 8

Energy spectrum measurement with chicane on.

L1

L2

L3

L4

L3 off

0 cm < R56 < 10.5 cm

L2 phase = -28, amplitude

constant

L1 phase = 0, amplitude constant

L4 off

File: t2phi02

100 200 300 400 500 600

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450

File: c3005

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450

File: c4006

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File: c5007

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R56 = 0 cm, L2 = -28

deg.

R56 = 1.8 cm, L2 = -

28 deg.

R56 = 3.3 cm, L2 = -28

deg.

R56 = 5.2 cm, L2 = -28

deg.

Pop 14 YAG

Images from Pop 14 at fixed L2 phase and increasing chicane strength. Energy spectrum is modified by CSR in

chicane.

W.S. Graves 2002 Berlin CSR workshop 9

0 deg. -8 deg. -16 deg. -24 deg. -28 deg.

R56

L2 phase

~1.6 cm

~6.8 cm

~2.9 cm

~4.6 cm

0 cm

Two parameter scan: Energy profiles as function of upstream chirp and chicane strength.

Scan of L2 phase and chicane strength

W.S. Graves 2002 Berlin CSR workshop 10

72 72.4 72.8

Energy (MeV)

RMS width = 139 keV

72 72.4 72.8

Energy (MeV)

RMS width = 120 keV

72.4 72.8 73.2

Energy (MeV)

RMS width = 87.9 keV

72.4 72.8 73.2

Energy (MeV)

RMS width = 68.3 keV

72.2 72.6 73

Energy (MeV)

RMS width = 151 keV

0 5 10 1560708090

100110120130140150160

Bend Angle (deg.)

RM

S d

E (

keV

)

Energy spectrum measurement vs chicane strength

Bunch is compressing with increasing chicane strength.

Energy spectrum can only be modified by CSR and wakes. Charge = 50 pC.

L2 phase = -16 degrees.

L3, L4 are off.

R56 = 0 cm R56 = 1.5 cm R56 = 2.7 cm R56 = 4.3 cm R56 = 6.3 cm

W.S. Graves 2002 Berlin CSR workshop 11

L1

L2

L3

L4

RF zero-phase time profile

L3 phase = +90, amplitude varies (removes chirp

from L2)

L4 phase = +/-90, amplitude varies (adds known chirp)

L2 phase varies,

amplitude constant

L1 phase = 0, amplitude constant

Chicane varies from 0 cm < R56 <

10.5 cm

100 200 300 400 500 600

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450

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L4 phase = -90 degrees L4 phase = +90 degreesL3 corrects residual chirp,

L4 is off

W.S. Graves 2002 Berlin CSR workshop 12

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50

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10

15

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25

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35

Time (ps)

Cur

rent

(A

)

File: rfplus01, RMS length = 0.763 ps

-2 -1.5 -1 -0.5 0 0.5 1 1.5 20

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10

15

20

25

30

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Time (ps)

Cur

rent

(A

)

File: rfminus01, RMS length = 0.572 ps

-0.4 -0.2 0 0.2 0.40

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200

300

400

500

Time (ps)

File: rfzero01, RMS length = 0.0493 ps

-3 -2 -1 0 1 2 30

0.020.040.060.080.1

0.120.140.160.18

Time (ps)

Det

ecto

r (m

V)

File: CC010822, RMS length = 1.26 ps

UV laser profile from scanning

cross-correlation with laser IR pulse.

Resolution ~200 fs.

RF zero-phase time profiles

L4 phase = -90 degrees L4 phase = +90 degreesL4 is off

W.S. Graves 2002 Berlin CSR workshop 13

400 2001007550

0

0.2

0.4

0.6

0.8

1

Wavelength (microns)

Coh

eren

t pow

er (

A.U

.) No compressionMild compressionStrong compression

0 0.2 0.4 0.6 0.8 1 1.2 1.40

100

200

300

400

500

600

700C

urr

en

t (A

)

Time (ps)

1 1.5 2 2.5020406080

100120140160

Cu

rren

t (A

)

Time (ps)

1 1.5 2 2.5 3 3.5 4 4.50

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20

30

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60

70

Cu

rren

t (A

)

Time (ps)

RF zero phasing measurement of electron

beam time profile.

No compression

Mild compression

Strong compression

1

2

3

4

5

6

123

4

5

687

Mild compression case shows ~7 periods in ~1 ps = 45 um

wavelength.

Strong compression case shows ~5 periods in 0.8 ps = 60 um

wavelength.

IR Spectrum from scanning interferometer courtesy of L. Carr (10 minutes/scan).

Data from March, 2001. Charge = 250 pC.

W.S. Graves 2002 Berlin CSR workshop 14

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50

20406080

100120140160180

Time (ps)

Cur

rent

(A

)

File: c5007t4, RMS length = 0.204 ps

Phi2 = -28

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5020406080

100120140160180

Time (ps)

Cur

rent

(A

)

File: c5006t4, RMS length = 0.195 ps

Phi2 = -26

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50

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20

30

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60

Time (ps)

Cur

rent

(A

)

File: c5003t4, RMS length = 0.354 ps

Phi2 = -16

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5020406080

100120140160180

Time (ps)

Cur

rent

(A

)

File: c5005t4, RMS length = 0.211 ps

Phi2 = -24

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50

1020304050607080

Time (ps)

Cur

rent

(A

)

File: c5004t4, RMS length = 0.327 ps

Phi2 = -20

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50

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Time (ps)

Cur

rent

(A

)

File: c5001t4, RMS length = 0.613 ps

Phi2 = 0, chicane on

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.505

1015202530354045

Time (ps)

Cur

rent

(A

)

File: c5002t4, RMS length = 0.461 ps

Phi2 = -8

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.50

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10

15

20

25

30

Time (ps)

Cur

rent

(A

)

File: rfplus03, RMS length = 0.808 ps

Phi2 =0, chicane off

RF zero-phase time profiles vs chirp

Chicane = 50 A,

4.1 cm < R56 < 5.2 cm,

-28 deg. < L2 phi < 0 deg.

W.S. Graves 2002 Berlin CSR workshop 15

-2 0 2 4 6 8 100

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20

30

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Time (ps)

Cu

rre

nt

(A)

3.0 mm spot, FWHM=3.0 ps 2.5 mm spot, FWHM=3.9 ps 2.0 mm spot, FWHM=4.6 ps 1.5 mm spot, FWHM=5.8 ps

Time profiles vs cathode diameterRF zero-phasing data from March, 2001 before gun upgrade and laser

cross-correlation measurements.

Gradient ~95 MV/m, charge = 200 pC, chicane off.

Structure is due to laser. At high charge density structure smears (and pulse lengthens) due to space charge near cathode. Speculate that

structure is shifted from time to energy.

W.S. Graves 2002 Berlin CSR workshop 16

0 0.5 1 1.5 2 2.50

100

200

300

400

500

600

Time (ps)

Cur

rent

(A

)

File: comp02, RMS length = 0.471 ps

Single pulse beam break-up at full

compression of 300 pC

Interesting observations

Single-frequency perturbation

W.S. Graves 2002 Berlin CSR workshop 17

-4 -2 0 2 40

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Time (ps)

Det

ecto

r (m

V)

File: uv010315, RMS length = 1.98 ps

72.3 72.4 72.5 72.6 72.7 72.8 72.9 730

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Energy (MeV)

Cur

rent

(A

)

File: q50pc02 blm, RMS length = 165 keV

1

2

3

4 56

7 8

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20

25

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35

Time (ps)

Cur

rent

(A

)

File: q50pc02 blm, RMS length = 0.719 ps

Two-pulse studies

UV laser time profile from cross-correlation measurement. Fourier-plane mask produces

two closely spaced pulses.

Energy distribution using T. Smith method. R56 = 9.5 cm, upstream chirp near zero (~no

compression).

Peak spacing ~64 um.

Head Tail

W.S. Graves 2002 Berlin CSR workshop 18

L1

L2

L3

L4

Chicane set for R56 ~ 9

cm

L3 off

L4 phase = -90, amplitude ~

1/R56

L1 phase = 0, amplitude constant

L2 phase varies,

amplitude constant

-3 -2 -1 0 1 20

5

10

15

20

25

30

Time (ps)

Cur

rent

(A

)

File: onepulse minus, RMS length = 0.713 ps

-2 -1 0 1 20

5

10

15

20

25

30

Time (ps)

Cur

rent

(A

)

File: onepulse plus, RMS length = 0.661 ps

-2 -1 0 1 20

10

20

30

40File: onepulse03, RMS length = 0.605 ps

T. Smith method time profile measurement

W.S. Graves 2002 Berlin CSR workshop 19

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = -35 mr

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = -27 mr

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = -19 mr

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = -11 mr

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = -3.4 mr

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = 4.5 mr

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = 13 mr

-10 -8 -6 -4 -2 0 2

Time (ps)

BBO ang. = 18 mr

Laser time profiles

Time profiles measured by scanning cross-correlation (difference frequency generation) of few ps UV cathode pulse with 100 fs IR oscillator pulse. Time

resolution is 200 fs FWHM. Data from B. Sheehy and H. Loos. ~5 minutes/scan.

Different plots are for different matching angles in BBO harmonic generation crystal.

130 uJ

120 uJ

280 uJ700 uJ1000 uJ

880 uJ80 uJ 420 uJ

W.S. Graves 2002 Berlin CSR workshop 20

Image of electron beam on pop14. Horizontal axis is time. Laser BBO crystal deliberately detuned to produce structure.

Bunch time profile from YAG image. Structure is due to laser…chicane off.

Streak camera measurement of UV light. Hamamatsu FESCA 500 streak camera with reflective input optics, sub-ps synch, and wide-response cathode.

Measured FWHM time resolution is 760 fs repetitive mode, 1.0 ps single-shot at 800 nm, and 2.4 ps single-shot at 266 nm.

0 2 4 6 8 10 120

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35

Time (ps)

Cur

rent

(A

)

File: p14f.bmp

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20406080

100120140160180200

175

225

275

325

375

15 17 19 21 23 25 27 29 31

Time (ps)

RF zero-phase compared to ‘sub-ps’ streak camera

W.S. Graves 2002 Berlin CSR workshop 21

Next steps…

Tomography: Use existing RF and chicane to measure complete 2D longitudinal distribution upstream of chicane. Currently under test.

IR spectrum: Installing new interferometer to measure CSR spectrum.

RF Deflector: Would provide unambiguous single-shot 2D longitudinal distribution upstream and downstream of chicane.

Simulation: Continue to build detailed comparison with experiment.

Benchmark different codes against experiment.