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Development of CZT array detector technology for Synchrotron

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Development of CZT array detector technology for Synchrotron Powered By Docstoc
					FEL Experiments at the DUV FEL:
    Past, Present and Future


                 Li Hua Yu

            for DUV-FEL Team
      National Synchrotron Light Source
       Brookhaven National Laboratory

     DUVFEL Workshop, BNL, 19-20/2004
                  Outline
• The DUVFEL performance and the system
  parameters
• Suggestion on some of the experiments that can
  be carried out at DUVFEL to address the
  associated issues in the Cascading HGHG
  scheme
DUV-FEL Configuration




             DUVFEL using NISUS wiggler
       Step 1. SASE at 400 nm (2. 2002)
       Step 2. direct seeding at 266nm (8.2002)
       Step 3. HGHG 800nm 266 nm(10.2002)

       After energy upgrade
       Next Goal 400nm 100 nm
  Deep UV Free Electron Laser at SDL

    Relation of pulse lengths                                                        Cathode driver 4 ps
                                                                                  Uncompressed bunch 4-5ps
    During 2002-2003 operation                                                      Compressed 1ps

                                                Seed 9ps



                                                                  FEL seed
                                                                  at 800 nm
                                                                                               Normal incidence
                                                             Modulator                 177
                                      Nisus Wiggler          Undulator                 MeV               77 MeV


Ion Pair Imaging                     NISUS pop-in     Dispersion                  CTR Monitor Adjustable Photoinjector
Experiment                             monitors        Magnet RF zeroPhasing                   Chicane
at 88 nm                                                                       Trim Chicane
                                                                                                         30 mJ
                                                                                                         Ti:Sapphire
            FEL Measurements                                                                             Amplifier
            Energy, Spectrum, Synchronization
            and Pulse Length Measurements
            at 266 nm
                   NISUS Undulator Parameters
• Period λw= 3.9 cm
• Length 10 m
• Canted poles provide horizontal focusing and reduce vertical focusing
• 4-wire focusing provide tuning ability to reach equal focusing Natural
  focusing: betatron wavelength λβ =20 m for 177MeV
• Because focusing is not strong, also because period 3.9 cm is large, gain
  length is far from optimized.
• Can be tapered
                          FEL gain length
• Simulation: HGHG reaches saturation at 400 nm with current
 I0= 300 amp, emittance n= 5 mm-mrad, energy spread

 σγ/γ=1.510-3, gain length LG=1.1 m
• We do not expect SASE saturation, because we have only 10 gain length
• SASE in February 2002 : LG=0.9 m
                                  Use Pop-in Monitors to Find Beam Matrix
                                            And Match into NISUS Wiggler
                                                       Nisus Beam Size Horizontal
rms size (um)




                600           match17
                              match18
                400           match19

                200

                 0
                      0       1         2      3       4       5       6       7        8   9    10
                                                       Nisus Beam Size Vertical
                                                             Distance (m)
                600
rms size (um)




                              match17
                400           match18
                              match19
                200

                 0
                      0   4   1         2      3        4      5       6       7        8   9    10
                      x 10                                   Distance (m)
                10


                          Found n= 4 m, agree with quad scan
                 5

                 0

                 -5
                      0             2              4               6                8       10        12
SASE @ 400 nm (Camera image after exit window) indicates
           good quality of transverse profile
            Direct seeding at 266nm (8/2002)

             2660Å                          2660Å



                                                    880Å




Based on SASE result at 400nm, we expect
       Fundamental at 266 nm: 0.13 mJ ,
       Harmonic at 88 nm: 0.6-1 J, pulse length ~1ps
       e-beam: 200 Amp, 4 mm-mrad, 170MeV
       Application in chemistry

Near saturation achieved (8/2002)
                        HGHG Experiment
      800 nm                                   266nm


                                                       88nm
                 MINI    Dispersion   NISUS
                           Section




HGHG from 800 nm266 nm,
Output at 266 nm: ~ 120J,
e-beam: 300 Amp, 3 mm-mrad,
Energy 176MeV

Output at 88 nm ~ 1 J
On-going Experiment Application in Chemistry
          HGHG power vs. distance (266 nm)




E-beam: 300 pC 4.7 μm (rms)        1.ps (FWHM)
Power measured by kicking beam off axis agree with photo-
diode measurement along NISUS
     Bunch Length Measurement by Zero Phasing
                    (12/2002)




         Head Left                           Head Right

•Projection of energy chirped pulse on energy axis, so the profile is
         not current but related to current.
•Ripples are due to small energy modulation, not large density modulation
•Average current: 300pC/1ps =300 Amp
Slice Emittance Measurement Without Compression
  Integrated emittance = 4.8 m, Q=200 pC
              W.Graves, Data from 3/25/02.




          4
   (m)




          2
   n




          0
                0              5             10
                         Slice Number
Global energy spread measurement result: 5-4
        Based on measurement of 12/11/2002: LG =0.8m ,
        current = 300 amp, slice emittance εn< 4mm-mrad
           Theory : local energy spread (rms) < 0.05%
                                                          εn
                                                          4.5 rad
                                                          4.0 rad

                                                          3.5 rad
                                                          3.0 rad

                                                          2.5 rad
LG(m)




                         σγ/γ
     Two sets of data compared with             10
                                                     2




                            Pulse Energy (J)
           TDA Simulation                       10
                                                     0




                                                         0   2      4       6
                                                                              (a) 1.8 MW
                                                                              (b) 30 MW
                                                                              TDA




                                                                 Wiggler Length (m)
                                                                                    8      10




    Current 300 A, Energy spread  110                                                             –4,   Dispersion dd = 8.7
(a) 12/11/02 Model: Pin=1.8MW                                                                   pulse length 0.6 ps, slice emittance 2.7 mm-mrad
     dd = 8.7
(b) 3/19/03 Model: Pin=30MW                                                                     pulse length 1 ps, projected emittance 4.7 mm-
    mrad, dd = 3
                        Whole bunch contributes to the output.
                         Autocorrelation Pulse Length
                          Measurement (Zilu, 2003)




                   (a)                                              (b)
      current 300 Amp, energy spread  110 –4, dispersion dd = 8.7
(a)   12/11/02 Model: Pin=1.8MW pulse length 0.6 ps, slice emittance 2.7 mm-mrad
(b)   3/19/03 Model:     Pin=30MW    pulse length 1 ps, projected emittance 4.7 mm-mrad
      Whole bunch contributes to the output
                   Spectrum of HGHG and unsaturated SASE at 266 nm
                          under the same electron beam condition



                                            HGHG
Intensity (a.u.)




                                           0.23 nm FWHM

                                                   SASE x105




                              Wavelength (nm)
         HGHG vs. Saturated SASE




If NISUS were increased to 20 m, the SASE
would be saturated. The gray line is a Genesis1.3
Simulation.
Average spacing between peaks in SASE spectrum also
gives pulse length ~ 1ps

           4nm
         14 peaks                             Average Spacing
                                             = 4 nm/14  0.3 nm




                             ( 266nm 
                                         2
             2
Tb                                               1.2 ps S.Krinsky
       0.64 c       0.64  3 108 m / s  0.3nm          (2001)
                                   HGHG
   Intensity (a.u.)
                                   0.23 nm FWHM
                                         SASE x105



                          Wavelength (nm)

For a flat-top 1ps pulse the bandwidth is
                        ( 266nm   0.23nm
                               2
                     2
                
                 c 1 ps  3 108 m / s

   HGHG output is nearly Fourier transform limited
                Shot to Shot Intensity Fluctuation
              Shows High Stability of HGHG output



Unsaturated
  SASE




 HGHG
Wen Li, A. Suits (PRL. 2003)
      R&D Towards Cascading HGHG:
     One of the Earlier Calculated Schemes
                                              A Soft X-Ray Free-Electron Laser
          1-ST STAGE                                     2-ND STAGE                                3-RD STAGE                                FINAL AMPLIFIER

     MODULATOR                 AMPLIFIER          MODULATOR                AMPLIFIER           MODULATOR             AMPLIFIER                     AMPLIFIER
       w = 11 cm              w = 6.5 cm          w = 6.5 cm            w = 4.2 cm           w = 4.2 cm         w = 2.8 cm                   w = 2.8 cm
      Length = 2 m             Length = 6 m       Length = 2 m             Length = 8 m        Length = 2 m         Length = 4 m                  Length = 12 m
       Lg = 1.6 m               Lg = 1.3 m         Lg = 1.3 m               Lg = 1.4 m          Lg = 1.4 m          Lg = 1.75 m                    Lg = 1.75 m




                DISPERSION                                  DISPERSION                                         DISPERSION

                 d d  = 1                                 d d  = 1                                       dd = 0.5




e-                                                                                                                                                                       e-


     LASER                                    DELAY       “Fresh”                  “Spent”    DELAY                                  DELAY
     PULSE                                                                        electrons
                                                         electrons

                                                            “FRESH BUNCH”
                                                                                                        “Fresh”
                                                                                                       electrons
                                                                                                                          “Spent”
                                                                                                                         electrons                             1.7
           e-                    e-                            CONCEPT                                                                                         GW
     500                                                                                      800 MW                         70
     MW                                       400 MW                                                                         MW                                  2.128
                5                            53.2 nm            5                           10.64 nm 5                                                         nm
     266 nm
     SEED
     LASER                     e-beam 750Amp                                       1mm-mrad
                               2.6GeV                              /γ=2×10 – 4                                   total Lw =36m
               Fresh Bunch
                Technique
                           Electron
  Laser                    bunch
  pulse
          Before Shifter         After Shifter


Technical issues:
•Time jitter of seed << electron bunch length
•Reduce number of stages: higher harmonic,
      smaller local energy spread
•Shorter seed laser pulse
      Some of the experiments that can be carried
       out at DUVFEL to address the associated
        issues in the Cascading HGHG scheme
1.   Chirped Pulse Amplification
         study how to generate short pulse in HGHG
2.   8’th harmonic HGHG (800nm100nm)
          possibility to reduce the number of stages of HGHG
          study how small the local energy spread is
          relation of coherence with harmonic number?
3.   HGHG with seed shorter than electron bunch length
       study the jitter and its relation to pulse shape
4.   Regenerative synchronization of seed pulse and electron bunch
        accurate synchronization is essential for cascading
5.   Cascading using NISUS+VISA: 400nm100nm50nm.
         Proof-of-principle experiment for cascading
6.   Tuning of HGHG without changing seed (Timur Shaftan)
         feasibility study at DUVFEL
Preliminary Data of CPA HGHG Spectra (A. Doyuran, et al., 8. 2003)




                                                              

                                   t
         Interpretation of 3 sets of measurements: effect of
         RF curvature; the second matched e-beam chirp to
         seed chirp
Chirped and Unchirped HGHG spectra

                      SASE spectrum
                      HGHG spectrum no chirp
                      CPA HGHG ~1 MeV
                      CPA HGHG ~2 MeV
                      CPA HGHG ~3 MeV
    Bandwidth vs Chirp                            1/3 BW of seed
                                                                   1.8nm



                                                                   1.5nm




                  / (%)
Seed bandwidth is 5.5 nm currently, thus 1.8 nm     Spectrum at /  .62 %
is expected at third harmonic.
 •Near future: SPIDER measurement of phase distortion
 • CPA: expected pulse length > 50fs (B. Sheehy, Z. Wu)
 •R&D: CPA at 100 nm?
                Possible Step: 8th Harmonic HGHG

      800nm                                  100 nm




                                                   33 nm
                MINI    Dispersion   NISUS
                         Section



•Electron beam energy upgrade to 300 MeV
•Need to reduce modulator vacuum chamber gap
•Increase flexibility of wavelength tuning
    Power vs. distance for 100 nm in HGHG from 800nm




•   Calculated for the same beam conditions as the present HGHG:
    current 300 Amp, energy spread  110 –4, slice emittance 2.7 mm-mrad input seed with
    60 MW
•   Going for higher harmonic and increase dispersion will lower the upper limit of the local
    energy spread estimate, possibly below 110 –4: 510 –5 ? Simulation for
    controlled local energy spread?
  Regenerative synchronization of seed pulse and
       electron bunch (L.H.Yu, FEL2003)
HGHG output 266 nm, 1ps
                                                           266 nm, 6 ps
                                               stretcher

                          compressor

                            delay
                      266 nm, 0.2ps




          •The jitter between the seed pulse and the electron
          bunch will be reduced by the compression ratio
          •It is possible to reduce jitter to below 50fs: an
          unprecedented precision. Important for multi-stage
          cascading to X-ray FEL
          •Can be tested without significant cost under present
          conditions
          •Energy fluctuation is also reduced by the same ratio
          Cascading HGHG Using Fresh Bunches
          Under the present e-beam Conditions


  400nm                     100nm                50nm
  2MW                       20MW
                                                 180MW
  200fs                     200fs
                                                 200fs



                MINI NISUS          NISUS VISA
                            6m      0.8 m 3m
e-beam     1ps
300Amp     2.7mm-mrad
288MeV      /γ=1×10 - 4
Electro-optical Measurement by Henrik Loos &
Brian Sheehy showed the time jitter between
electron bunch and seed laser is ~ 300fs.

               •   Measuring timing jitter between electron beam and
                   laser is important in externally seeded FEL schemes
                   like HGHG
               •   Single shot measurement decouples jitter from pulse
                   length
               •   Estimated jitter from this electro-optic measurement
                   between electron beam and seed laser is rms 170 fs
               •   Jitter between low-level RF and Ti:Sapphire oscillator
                   is 200 fs
               •   Energy jitter obtained in dipole spectrometer
                   corresponds to 1 ps RF amplitude/phase jitter
               •   Needs more work…
Tomography of electron bunch distribution by Henrik Loos 12/2/03
 Reconstruction Uncompressed Bunch                                                                                                                                   Reconstruction compressed Bunch
                                       50                                                                                                   200
   Energy (keV)




                                                                                                     Energy (keV)
                                       25                                                                                                   100

                                                 0                                                                                                               0

                                    -25                                                                                                -100
         E (keV)




                          20                                                                                                     100




                                                                                                          E (keV)
                           0
                                                                                                                                   0
                         -20
                               -5       -2.5          0           2.5           5                                       -100
                                                                                                                                       -1        -0.5        0       0.5       1
                Current (A)




                                                                                                                Current (A)
                              50                                                                                                 400


                               0
                               -5


                                    -50
                                      -5
                                        -2.5          0           2.5           5




                                                                                        0        5
                                                                                                                                 200

                                                                                                                                   0




                                                                                                                                       -200 -1
                                                                                                                                       -1        -0.5        0       0.5       1
             Intensity




                                                                                                                     Intensity
                              0.1                                                                                                0.1


                               0
                              -10 -8   -6   -4   -2   0   2
                                                  Time (ps)
                                                              4         6   8   10




                                                                                     Time (ps)
                                                                                                                                   0
                                                                                                                                  -10 -8    -6    -4    -2   0   2
                                                                                                                                                         Time (ps)
                                                                                                                                                                     4     6   8   10


                                                                                                                                                                                        -0.5      0    0.5   1
                                                                                                                                                                                               Time (ps)
               Illustration on how to use the electron
                  bunch twice during cascading of
                               HGHG



              400
Current (A)




              200


                0
                    -1      -0.5       0        0.5   1
                                   Time (ps)
                         100 nm 50nm
                                400 nm 100nm

                                   Time (ps)
 Cascading HGHG from 400nm to 100 nm, then
 to 50 nm, input 20MW, dispersion=3.6




If we improve beam current from 300 Amp
to 600 Amp, the saturation is reached before 2 m in VISA
    HGHG with variable wavelength
    (Timur Shaftan, 2004)




There is a small compression of the electron
bunch in the dispersion section, hence the
wavelength is also slightly compressed.
Single-Shot spectra for different chirps
     for the same seed wavelength
 showed different output wavelength
   (Timur, Brian, Henrik, Zilu 2004)




   Possible experiment in near future: increase
   dispersion increased tuning range
                           Summary
•   Analysis of the present HGHG experiment provides
    estimates for the operating parameter range
•   Based on the roughly determined beam parameters,
    we suggest some of the experiments that can be
    carried out at DUVFEL to address the associated
    issues in the cascading HGHG scheme:
    1.   Chirped Pulse Amplification
    2.   8’th harmonic HGHG (800nm100nm)
    3.   HGHG with seed shorter than electron bunch length
    4.   Regenerative synchronization of seed pulse and electron
         bunch
    5.   Cascading using NISUS+VISA: 400nm100nm50nm.
    6.   Tuning of HGHG without changing seed (Timur Shaftan)
ur Shaftan)

				
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