Laser Status Update J. Moody, E. Oz, P. Muggli MPP Future Accelerators AWAKE Collaboration

Background/Purpose of Laser High Intensity Laser Needed For: Ionization of rubidium vapor plasma source Seeding of Self-Modulation Instability Photocathode drive laser for the electron source (after third harmonic generation) To ionize the Rb vapor via tunnel ionization, we must have a sustained intensity above: I threshold = 1.7 TW/cm^2

Laser Requirements for Ionization of Plasma Cell at CERN These laser parameters : Spot size at waist Rayleigh length Pulse length Pulse energy Are chosen to ionize the Rb vapor over 10 m with ~ 1 mm without depletion. Parameters from CERN design report

Factory Acceptance Test Occurred in Late Amplitude Technologies E. Oz, P. Muggli and J. Moody attended

Sample Measurement: Pulse Length From Bonsai Single-Shot autocorrelator

Results of Factory Acceptance Testing Courtesy of Amplitude Technologies Meets or exceeds desired specifications

Laser Room at MPP Laser room: Currently under construction Will be finished on Monday (29 September 2014). Laser has arrived at MPP, currently in storage … until next week!

MPP Laser Room Layout Compressor Amplifier Vapor Source or Heat Pipe Oven Oscillator Offner Stretcher Regenerative Amplifier and Preamp Beam Dump and Diagnostics Power Supply for Amplifier

Ionization Studies at MPP Best scaled approximation to the CERN AWAKE case. Understanding laser propagation and ionization in Rb vapor – Near resonance-linear dispersion – Nonlinear propagation (self focusing, self-steepening) – Ionization effects on propagation. Characterization of Rb vapor plasma source. Limitations: – In Air compressor -> Cannot operate at full power Maximum compressed power: fs – Damage threshold of any windows. – Damage threshold of final turning mirror Turning mirror ~2m from laser waist. DT of TLMB 40fs. Best case focusing situation for MPP is currently being designed

Potential Ionization Studies Heat pipe oven – Uses buffer gas to confine Rb vapor – Can now extend vacuum system without worry of Rb contamination of mirrors, damage threshold of windows 3m Rb vapor source – Requires fast valves – Fast Rayleigh range Laser Diagnostics – Single shot autocorrelator – Transverse profile monitor – Energy monitor Heat Pipe Oven

Plan and Schedule Next week (29 September – 05 Oct) – Monday: Laser room construction finished. – Tuesday: Laser table, compressor table, and dump/diagnostic table move-in. – Wednesday: Laminar flow enclosure delivered and assembled around laser table. – Thursday-Sunday: Bring laser out of storage, place components (06 Oct – 17 Oct) Two week installation, on-site acceptance testing and laser training. 19 Oct 2014 ~ Summer 2015 Ionization studies with laser and prepare to move laser to CERN Amplitude – Placing pressure on amplitude for : Quote for vacuum compressor Photocathode drive amplifier, THG Stretcher. (Recycle MPP in-air compressor)

Extra Slides Focusing Scheme proposed by Amplitude.

Full energy configuration (Vacuum Compressor ) f1 = -200 mmf2 = 500 mm f3 = mm 643 mm 253 mm40,2 m Ø 10 1/e² Ø 1,56 1/e² Ø 33,6 1/e² Ø 41,8 1/e² folding mirror 15 m Colorbar indicates the fluence in J/cm² at 0°incidence Beam fluence on lens 3 Ø /e² E = 650 mJ Beam fluence on folding mirror Ø /e² E = 455 mJ (70 % transmission of compressor)

In-Air Compressor Fluence Limit Colorbar indicates the fluence in J/cm² at 0°incidence f1 = -200 mmf2 = 500 mm f3 = mm 540 mm 566 mm 39,5 m Ø 10 1/e² Ø 2,2 1/e² Ø 23,4 1/e² Ø 36,7 1/e² 15 m folding mirror Ø 23,4 mm Beam fluence on lens 3 Ø /e² E = 400 mJ Beam fluence on folding mirror Ø /e² E = 280 mJ (70% transmission of compressor) In amplifier