1. 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

2. W.S. Graves 2002 Berlin CSR workshop 2 SDL Facility 1.6 cell gun with copper cathode 75 MeV Bend 50 m 5 MeV Bend Dump IR interferometer Time domain measurements UndulatorsLinac tanks 200 MeV Bunch compressor 30 mJ, 100 fs Ti: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.

3. W.S. Graves 2002 Berlin CSR workshop 3 Tank 1Tank 2 Tank 4 Tank 3 Chicane Kly AKly CKly B 1.6 cell gun with copper cathode Pop 14 YAG DUVFEL Accelerator 45 MW Thompson Klystrons 197 MeV137 MeV77 MeV40 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 scan Matching triplet

4. W.S. Graves 2002 Berlin CSR workshop 4 Technical Data Gun 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 SDL data from 1/8/2002 -2-1.5-0.500.511.52 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Hor. Position (mm) Intensity (A.U.) File: lasera, Hor. RMS width = 0.695 mm -2-1.5-0.500.511.52 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Ver. Position (mm) Intensity (A.U.) File: lasera, Ver. RMS width = 0.64 mm UV laser virtual cathode image Horizontal projection Vertical projection -3-20123 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 Time (ps) Detector (mV) File: CC010822, RMS length = 1.26 ps UV laser time profile -2.5-2-1.5-0.500.511.522.5 0 5 10 15 20 25 30 35 Time (ps) Current (A) File: rfplus01, RMS length = 0.763 ps Ebeam time profile

5. W.S. Graves 2002 Berlin CSR workshop 5 Energy spectrum measurement L1L2L3L4 L3 off Chicane varies from 0 cm < R56 < 10.5 cm L2 phase varies, amplitude constant L1 phase = 0, amplitude constant L4 off L1L2L3L4 L1L2L3L4 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

6. W.S. Graves 2002 Berlin CSR workshop 6 72.272.472.672.87373.2 Energy (MeV) RMS width = 151 keV 74.274.474.674.87575.2 Energy (MeV) RMS width = 90.1 keV 75.675.87676.276.476.6 Energy (MeV) RMS width = 16.6 keV 76.276.476.676.87777.2 Energy (MeV) RMS width = 74.6 keV 74.474.674.87575.275.4 Energy (MeV) RMS width = 188 keV Energy spectrum measurement with chicane off. L1L2L3L4 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.

7. 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.

8. W.S. Graves 2002 Berlin CSR workshop 8 Energy spectrum measurement with chicane on. L1L2L3L4 L3 off 0 cm < R56 < 10.5 cm L2 phase = -28, amplitude constant L1 phase = 0, amplitude constant L4 off 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.

9. 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

10. W.S. Graves 2002 Berlin CSR workshop 10 7272.472.8 Energy (MeV) RMS width = 139 keV 7272.472.8 Energy (MeV) RMS width = 120 keV 72.472.873.2 Energy (MeV) RMS width = 87.9 keV 72.472.873.2 Energy (MeV) RMS width = 68.3 keV 72.272.673 Energy (MeV) RMS width = 151 keV 051015 60 70 80 90 100 110 120 130 140 150 160 Bend Angle (deg.) RMS dE (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 cmR56 = 1.5 cmR56 = 2.7 cmR56 = 4.3 cmR56 = 6.3 cm

11. W.S. Graves 2002 Berlin CSR workshop 11 L1L2L3L4 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 L4 phase = -90 degreesL4 phase = +90 degrees L3 corrects residual chirp, L4 is off

12. W.S. Graves 2002 Berlin CSR workshop 12 -2.5-2-1.5-0.500.511.522.5 0 5 10 15 20 25 30 35 Time (ps) Current (A) File: rfplus01, RMS length = 0.763 ps -2-1.5-0.500.511.52 0 5 10 15 20 25 30 35 Time (ps) Current (A) File: rfminus01, RMS length = 0.572 ps -0.4-0.200.20.4 0 100 200 300 400 500 Time (ps) File: rfzero01, RMS length = 0.0493 ps -3-20123 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 Time (ps) Detector (mV) 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 degreesL4 phase = +90 degreesL4 is off

13. W.S. Graves 2002 Berlin CSR workshop 13 00.2 0.40.6 0.81 1.2 1.4 0 100 200 300 400 500 600 700 Current (A) Time (ps) 11.522.5 0 20 40 60 80 100 120 140 160 Current (A) Time (ps) 11.522.533.544.5 0 10 20 30 40 50 60 70 Current (A) Time (ps) RF zero phasing measurement of electron beam time profile. No compression Mild compression Strong compression 1 2 3 4 5 6 12 3 4 5 68 7 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.

14. W.S. Graves 2002 Berlin CSR workshop 14 -2.5-2-1.5-0.500.511.522.5 0 20 40 60 80 100 120 140 160 180 Time (ps) Current (A) File: c5007t4, RMS length = 0.204 ps Phi2 = -28 -2.5-2-1.5-0.500.511.522.5 0 20 40 60 80 100 120 140 160 180 Time (ps) Current (A) File: c5006t4, RMS length = 0.195 ps Phi2 = -26 -2.5-2-1.5-0.500.511.522.5 0 10 20 30 40 50 60 Time (ps) Current (A) File: c5003t4, RMS length = 0.354 ps Phi2 = -16 -2.5-2-1.5-0.500.511.522.5 0 20 40 60 80 100 120 140 160 180 Time (ps) Current (A) File: c5005t4, RMS length = 0.211 ps Phi2 = -24 -2.5-2-1.5-0.500.511.522.5 0 10 20 30 40 50 60 70 80 Time (ps) Current (A) File: c5004t4, RMS length = 0.327 ps Phi2 = -20 -2.5-2-1.5-0.500.511.522.5 0 5 10 15 20 25 30 35 Time (ps) Current (A) File: c5001t4, RMS length = 0.613 ps Phi2 = 0, chicane on -2.5-2-1.5-0.500.511.522.5 0 5 10 15 20 25 30 35 40 45 Time (ps) Current (A) File: c5002t4, RMS length = 0.461 ps Phi2 = -8 -2.5-2-1.5-0.500.511.522.5 0 5 10 15 20 25 30 Time (ps) Current (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.

15. W.S. Graves 2002 Berlin CSR workshop 15 -20246810 0 20 30 40 50 60 Time (ps) Current (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 diameter RF 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.

16. W.S. Graves 2002 Berlin CSR workshop 16 00.511.522.5 0 100 200 300 400 500 600 Time (ps) Current (A) File: comp02, RMS length = 0.471 ps Single pulse beam break-up at full compression of 300 pC Interesting observations Single-frequency perturbation

17. W.S. Graves 2002 Berlin CSR workshop 17 -4-2024 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 Time (ps) Detector (mV) File: uv010315, RMS length = 1.98 ps 72.372.472.572.672.772.872.973 0 5 10 15 20 25 30 35 Energy (MeV) Current (A) File: q50pc02 blm, RMS length = 165 keV 1 2 3 4 5 6 7 8 -1.5-0.500.511.5 0 5 10 15 20 25 30 35 Time (ps) Current (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. HeadTail

18. W.S. Graves 2002 Berlin CSR workshop 18 L1L2L3L4 Chicane set for R56 ~ 9 cm L3 off L4 phase = -90, amplitude ~ 1/R56 L1 phase = 0, amplitude constant L2 phase varies, amplitude constant -3-2012 0 5 10 15 20 25 30 Time (ps) Current (A) File: onepulse minus, RMS length = 0.713 ps -2012 0 5 10 15 20 25 30 Time (ps) Current (A) File: onepulse plus, RMS length = 0.661 ps T. Smith method time profile measurement

19. W.S. Graves 2002 Berlin CSR workshop 19 -10-8-6-4-202 Time (ps) BBO ang. = -35 mr -10-8-6-4-202 Time (ps) BBO ang. = -27 mr -10-8-6-4-202 Time (ps) BBO ang. = -19 mr -10-8-6-4-202 Time (ps) BBO ang. = -11 mr -10-8-6-4-202 Time (ps) BBO ang. = -3.4 mr -10-8-6-4-202 Time (ps) BBO ang. = 4.5 mr -10-8-6-4-202 Time (ps) BBO ang. = 13 mr -10-8-6-4-202 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 uJ420 uJ

20. 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. 024681012 0 5 10 15 20 25 30 35 Time (ps) Current (A) File: p14f.bmp 50100150200250300350400 20 40 60 80 100 120 140 160 180 200 Time (ps) RF zero-phase compared to ‘sub-ps’ streak camera

21. 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.