Drive Laser Operations

Transcription

1 Drive-Laser Operations Drive Laser Thales laser Transport system Recent Laser Milestones Safety Technical Where do we stand today? Laser Acceptance Status Laser Commissioning UV on cathode Injector Commissioning Laser Operations Future 1

2 UV pulse goals IR to UV conversion efficiency > 10 %, 2.5 mj 255 nm nm, < 2% energy stability 120 Hz, MTBF > 5000 hours Spatial Profile Temporal Profile FWHM = 10 ps (5-20 ps) FWHM = mm flat-top, < 8% peak-to peak rise and fall times < 1 ps 2

3 Challenges Temporal Shape Spatial Shape UV conversion 120 Hz Synchronization Reliability Characterization Most Difficult Very Difficult Compounds both! 3

4 Laser Beam Specifications on the Cathode Parameter Central Wavelength Pulse Energy Spatial Fluence Profile Spot Radius Centroid Position Stability Repetition Rate Temporal Power Profile Profile FWHM Profile Rise/Fall time Timing Jitter Nominal Spec 255nm >0.4mJ Continuously adjustable Uniform (adjustable) Adjustable from 0.6mm to 1.5mm <10% radius (RMS) 120Hz, 60Hz, 30Hz, 10Hz, 1Hz Uniform (adjustable) Slope adjustable from -10% to +20% 10 psec (adjustable to from 5 to 20 psec) 1.0ps (10% to 90%) < 0.25 psec (shot-to-shot) Tolerance +/- 3nm <2% RMS variation (shot-to-shot) <20% (peak-to-peak) <4% (Shot-to-shot) <8% peak-to-peak on the plateau < 2 % RMS (over multiple shots) with respect to the external RF source 4

5 Parameter Wavelength Pulse energy Spatial fluence profile Thales Laser System Specifications Pointing Stability Rep rate Temporal power profile profile FWHM Rise/fall time Timing jitter Nominal spec 255nm nom. > 2.5 mj Gaussian, M 2 <2 Less than 25 microradian 120Hz, 60Hz, 30Hz, 10Hz, 1Hz Uniform 10 psec adjustable from 5 to 20 psec 1.0 psec (10% - 90%) < 0.25 psec (shot-to-shot) Tolerance +/- 3nm < 2 % rms variation <10% peak-to-peak variation within the profile) <8% peak-to-peak on the plateau < 2 % (RMS over multiple shots) MTBF >5000 hours With periodic maintenance 5

6 Thales Laser system Stretcher Dazzler UV Conversion Oscillator Preamplifier Regen Compressor Final Amplifier 6

7 Oscillator Includes SP-Millenia pump 50nm bandwidth 760 nm 400 mw 7

8 8

9 Jedi Pump Lasers QCW diode pumped MOPA design 2 amps KTP doubler 9

10 Supervision Software 10

11 Drive Laser Pulse Control To Cathode Energy Control High Voltage Supply Beam Dump Laser Trigger (120 Hz) PPS MPS MCC High Speed Driver Pockels Cell Laser Pulses 120HZ 11

12 Laser Feedback Laser RF Reference Programmable HV Pulse??? 120/N Hz MPS RF Phase Shifter FemtoLase Locking Electronics Laser Oscillator Amplifier Pulse Slicer Compressor UV Transport Linac Cavity Accelerator Gun Cathode IM01 Current Monitor Virtual Cathode Pointing Feedback (EPICS) <1Hz Thales Laser Phase Feedback <120 Hz Laser Energy Feedback <120 Hz SLAC Laser Group 765 nm 255 nm e-beam wire 12

13 Pulse Shaping - Dazzler 13

14 Solid State Saturation Fluence Input Output g = σ n A 0 Material Dependent A 0 e gl J sat = hν σ g = I s g I hν = στ f I s In general, lasers are designed to operate at Jsat because: Optimize gain and energy extraction Better energy stability 14

15 Intensity at Saturation (2 ps) Material Jsat (J/cm 2 ) Imax (W/cm 2 ) Nd:Silicate 6 3x10 12 Yb:Silicate x10 13 Ti:Sapphire 1 5x10 11 ALL >> 5x10 9 W/cm 2 Conclusion: We must reduce pulse INTENSITY during amplification 15

16 Short pulse oscillator Chirped Pulse Amplification t Dispersive delay line Δt stretch = J sat /I damage Nd:Glass ~ 1 ns Ti:Al 2 O 3 ~ 200 ps t Solid state amplifiers Saturation is Reached Safely t Inverse delay line Strickland & Mourou,, Opt. Comm.56, 219, 1985 Peak Power Increase Proportional to Δt stretch > 1000 t 16

17 Conventional CPA Stretcher/Compressor Positive dispersion stretcher Negative dispersion compressor l S 1 2f S 2 l eff =(f-s 1 )+(f-s 2 ) Intensity Intensity Time Time 17

18 Generic Regenerative Amplifier V t seed output V t WP PC1 Doubled Nd:YLF pump beam pol PC2 Low energy seed pulse injected into regen cavity First Pockels cell traps pulse in cavity Pulse gains energy on each pass through rod Second Pockels cell ejects pulse off of polarizer when stored energy is depleted Pulse build-up in regen cavity 18

19 Generic Regenerative Amplifier seed V output t WP Doubled Nd:YLF pump beam pol PC 19

20 THG Module Two type I BBO SHG and THG crystals Doubler Tripler Time Delay 20

21 Coupled NL Splitstep FFT Pulse Propagation Temporal discretization > 4096 Spatial discretization per stage > 1000 Brent Stuart, John Heebner, Chris Ebbers, Igor Jovanovic, Susan Haynes, Ben Pyke (LLNL) 21

22 Beam shaper Table in the tunnel Vacuum cell L1 Virtual Cathode Transport -Layout L2 Powermeter L3 Zoom Steering system L4 Transport tube F1=200 F2=120 F3=-150 F4=F5=5000 F6=1500 Camera Polarizer L5 Photocathode Waveplate Shutter L6 Active Steering Stabilization 22

23 Active Steering Stabilization In order to meet centroid position stability requirement (min 60μm) M6 should be stabilized with 35μrad accuracy Sensitivity of the mirror mount 7arcsec 34 μrad Laser Bay Transport Tube M6 From Virtual Cathode Table in the tunnel M3 C2 Camera M4 Camera M5 To Photocathode M2 Steering Stabilization system test is underway C1 23

24 Testing of the Newport Shaper Input beam 24 Image of the aperture after the shaper Courtesy of John Castro

25 Safety Recent Milestones LSS certified 11/3/06 Final SOP approved 11/6/06 ESC Walkthrough 11/8/06 25

26 Recent Milestones July 21 Laser Arrives at Sector 20 26

27 Recent Milestones July 14 Laser Tables Installed 27

28 Recent Milestones July 24 Complete system on table 28

29 Where are we now? - Today Laser Work Complete LSS Move laser supplies into rack Setup streak camera Setup cross-correlator Setup UV-FROG Setup spatial diagnostics Laser Infrastructure complete 29

30 Thales Laser System Performance Pulse Energy After compressor 35mJ UV output-2.8mj Energy jitter in UV 1.1% (rms) Spatial shape in IR Gaussian, M 2 =1.5 Pointing Stability 5 μrad Timing Jitter 0.21psec 30

31 Energy Jitter Measurements 31

32 Pointing Stability Measurements Measured at the focal plane of the 0.8m focal length lens 32

33 Temporal Shaping and UV Conversion UV Conversion process affects the temporal shape Optimum crystal length is essential UV Pulse SHG crystal 1mm long UV Pulse SHG crystal 0.5mm long IR Pulse 33

34 Where are we now? - Today Streak Camera installed and working 34

35 Where are we now? - Today Cross-Correlator working 25 Cross Correlator Scan - [cc_ txt] 20 τ STD = 0.56 ps τ FWHM = 1.27 ps Signal (mv) Time (ps)

36 Where are we now? - Today TG-FROG working 36

37 Temporal Shaping and UV Conversion UV Conversion process affects the temporal shape Optimum crystal length is essential UV Pulse SHG crystal 1mm long UV Pulse SHG crystal 0.5mm long IR Pulse 37

38 Temporal Shaping Dazzler 45mm long 2 passes in the Dazzler Beam size, collimation and alignment of the Dazzler are critical Resolution of the Dazzler should be 0.3nm 0.3nm hole at 760nm 38

39 Using Dazzler to Shape the Spectrum Spectrum after the compressor Without Dazzler shaping Dazzler spectrum has a hole After the Dazzler After the Compressor 39

40 Temporal Pulse Shape Streak Camera 40 Cross correlator

41 Temporal Pulse Shaping The achieved temporal pulse shape meets physics requirements for the injector commissioning Plan to improve the temporal shape Replace the Lyot filter in the regen amplifier by the edge mirrors this will reduce oscillations Continue working on the Dazzler settings and the optimum UV conversion crystals lengths Thales engineers are coming back in December-January to continue working on shaping Plan B to use stacking of Gaussian pulses Design and parts for pulse stacking are in place 41

42 Spatial Beam Shaping Newport Shaper GBS-UV H Converts Gaussian beam input to flat top output Transmission >97% High profile uniformity - 78% of input power is directed into the flat top with 15% RMS power variation Collimated output beam allows use of conventional optics after beam shaping Provides performance over large wavelength ranges 42

43 Spatial Shaping work in progress Laser Output 43 Spatial Shaper Output

44 Laser Commissioning Transport Shaper Diagnostics Pointing Lock Loops Characterization Calibration of diagnostics Virtual Cathode 44

45 Sector 20 Laser Bay Transport Tubes Launch System 45

46 Transport System in the Laser Bay Remotely Controlled Mirror Beam Size Adjustment Lens Shaper To Transport tube Shaper Input Adjustment Laser Output 46

47 Optical System next to the Photocathode From Transport tube Remotely Controlled Mirror Lens Steering Stabilization Camera Virtual Cathode camera Steering Stabilization Camera Lens Lead Block Powermeter Remotely Controlled Mirrors Lead Blocks Photocathode 47 In vacuum mirror

48 Photocathode Launch System Virtual Cathode camera To the cathode Photocathode launch system has been assembled in the laser bay The system will be tested before it goes into the vault 48

49 What's Next - Laser Commissioning Laser table and LSS in Vault Laser door installed prior to transport Nov 20 Components will be installed and tested in laser bay prior to table moving to vault Support for laser table should be ready for table installation on Nov 28th 49

50 What's Next - Laser Commissioning Virtual cathode work requires GTL. Gun can be installed two weeks after GTL installation UV on cathode one week later. Laser optimization (temporal profile, stability, automation, etc) will continue until GTL is installed. 50

51 Injector Commissioning UV on Cathode scheduled mid-march Laser group operates the laser Some laser commissioning will continue in parallel Characterization Automation Refine Operation Procedures Refine Maintenance Schedules August 07 Down Train Ops Group Hand off laser in Jan 08 51

52 August 07 Down Hand Over to Ops Train Operations Group on typical Operation Procedures Hand off laser by Jan 08 Laser Group will support Ops Scheduled Maintenance Issues that arise outside of the typical operation envelope 52

53 End 53