Optical BPM Progress A0 Photoinjector July 17th, 2009 Tim Maxwell, Jinhao Ruan, Philippe Piot & Mike Church

Optics Status and Roadmap 1) Laser Autocorrelator (SHG) For single-shot laser pulse duration measurement Also for synchronizing laser pulses Now assembled and functioning 2) Frequency Resolved Optical Gating (FROG) An autocorrelator with a diffraction grating Measures λ vs. t shot-to-shot (duration and chirp) Kit awaiting assembly pending study of autocorrelator

Optics Status and Roadmap 3) Fiber Transport For IR laser transport line from laser room to cave Fibers and launch optics ready Need FROG to characterize fiber dispersion effects 4) Laser pulse stretcher (and compressor) Introduce chirp for EO spectral encoding Help compensate for fiber dispersion Above experiments needed to proceed Fiber measurements to determine compensation needed FROG to verify performance

Single-shot autocorrelator Autocorrelator based on ~SHG and spatial encoding When pulses cross simultaneously (brightest and centered blue spot) blue stripe is autocorrelation of pulse Split laser pulse, duration (thickness) exaggerated BBO Crystal

Single-shot autocorrelator Second-best layout Half angle between lasers at crystal of ~19° ~ Revised layout Half angle between lasers at crystal of ~9° ~ ~ ~ ~

Single-shot autocorrelator

Single-shot autocorrelator For single-shot mode, scan delay to find peak signal and find… First result last night (7/16/09)

Single-shot autocorrelator Finding time axis calibration factor Convert micro controller position to time delay: Δt = 2 Δx / c Scan stepper recording spot centroid as a function of delay Slope of centroid position vs. delay yields conversion pix to sec Centroid calculated two ways: Brightest horizontal trace X projection Projection shows roll off in this result (no background correction). Used linear region of “Trace” Preliminary calibration: 2.5 fs / pix

Preliminary first results Revisiting peak horizontal trace and x projection from earlier: RMS laser pulse length 140 fs …if only I had also measured the bandwidth for comparison.

Conclusions Autocorrelator up and running and seems to work well so far Clean up the control and analysis scripts (Matlab) Compare single-shot method (shown here) with scanning method Vary Ti:Sapph bandwidth and measure pulse length We had to cut incidence angle in half Should be able to use bigger angle according to theory Did I just not see the dot in original set up? Want bigger angle for in-pipe autocorrelator! When done with initial exploration, attempt larger angle again? Extend into Frequncy Resolved Optical Gating with the kit Assemble and test remaining optics for EO experiment, as mentioned Somewhat unrelated: Also still looking into wake filed calculations for the proposed EO pipe section…