microbunching and csr experiments at bnl’s source development lab
DESCRIPTION
Microbunching and CSR experiments at BNL’s Source Development Lab. William S. Graves ICFA CSR Workshop Berlin, Jan., 2002. SDL Facility. 50 m. 1.6 cell gun with copper cathode. IR interferometer. Bunch compressor. Bend. Undulators. Bend. Linac tanks. 75 MeV. 5 MeV. Time domain - PowerPoint PPT PresentationTRANSCRIPT
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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350
400
450
File: c3005
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450
File: c4006
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File: c5007
100 200 300 400 500 600
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450
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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250
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350
400
450
100 200 300 400 500 600
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450
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450
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
5
10
15
20
25
30
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
5
10
15
20
25
30
35
Time (ps)
Cur
rent
(A
)
File: rfminus01, RMS length = 0.572 ps
-0.4 -0.2 0 0.2 0.40
100
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
10
20
30
40
50
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
10
20
30
40
50
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
5
10
15
20
25
30
35
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
5
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
10
20
30
40
50
60
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
5
10
15
20
25
30
35
Energy (MeV)
Cur
rent
(A
)
File: q50pc02 blm, RMS length = 165 keV
1
2
3
4 56
7 8
-1.5 -1 -0.5 0 0.5 1 1.50
5
10
15
20
25
30
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
5
10
15
20
25
30
35
Time (ps)
Cur
rent
(A
)
File: p14f.bmp
50 100 150 200 250 300 350 400
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.