July LEReC Review July 2014 Low Energy RHIC electron Cooling Brian Sheehy Laser and Timing

July Outline Scope High Level System Description Parameters Procurements Relocated equipment –used/borrowed/repurposed –Moved to make space Equipment installation location and conventional facilities requirements Timeline Summary 2

July Scope Provide laser pulses to the photocathode in the electron gun –synchronized with the 704 MHz accelerating RF –flexible macrobunch patterns tailored to complement ion bunch lengths and separations at different ion bunch energies (next slide). –Pulse width 50 psec FWHM, temporal shape TBD by beam dynamics simulations.  Flat top  Gaussian –Transverse shaping or truncated Gaussian spatial profile –Noise stabilization 3

July Scope: flexible timing, pulse pattern 1.42 nsec 30 electron bunches 120 ion bunches in the ring Overlap 30 e - bunches with each ion bunch e - bunch separation 1/ RF(gun)

July Scope: flexible timing, changing periods 5 Need to maintain synch between ions, electrons and accelerator RF over a range of orbital periods 9 MHz system tunes at 120 x  Harmonic number for MHz must vary Gun need only tune over a range of 

July High Level Systems Description 704 MHz fiber-coupled 1040 nm seed source, locked to RF –For temporal flat-top: mode-locked 10 psec FWHM –‘Gaussian’: electro-optically modulated CW laser Electro-optic modulation to select pulse pattern Multi-stage Yb-doped fiber & fiber rod amplifier Frequency-doubling to 520 nm in noncritically phase-matched Lithium triborate (LBO) crystal Temporal and transverse shaping –Pulse stacking for flat-top pulse 6

July System Description: seed source options 7 EOM 1 Amplifier chain Narrow bandwidth CW laser 100 MHz Pulser & PLL 9.1 MHz Pulser EOM 2 EOM = Electro-optic modulator PLL = phase-locked loop Fiber coupling 10 psec mode- locked laser & PLL (if flat top) ‘Gaussian’

July System Description, amplifier & doubling 8 A similar 150 Watt amplifier at Cornell (Zhao et al JOSA B 31, 33 (2014)

July Parameters 9 REQUIRED AT PHOTOCATHODE (GREEN): 1.6 MeV2 MeV gamma total charge per ion bunch QnC 3.0 # e- bunches/ion bunch 30.0 Q/ebunchpC laser pulse 1% QE nJ 23.8 ion bunch rep rateMHz average rep rateMHz average currentmA avg laser 1%QEW peak power 10 psec FWHMkW 2.4 peak power 50 psec FWHMkW 0.5 LaserIRGreen energy/pulsenJ average powerW pulse width (FWHM)ps flat top107(stack to 50 ) Gaussian7050 peak powerkW flat top5531 (4.4 after stacking) Gaussian M intensity noise (rms)%12 jitter wrt RF (rms)psec11 Assumes 40% conversion efficiency Plenty of overhead in power capability for shaping, transport, QE degradation.

July Procurements Laser Modulator and amplifier$240,000 Frequency Doubling module$20,000 Transport fibers$10,000 fiber launch system with stabilization feedback$10,000 transport and control optics$6,000 transport and control optomechanics$3,500 diagnostics: cameras & lenses$6,000 diagnostics: power meters$5,000 diagnostics: photodetectors$4,000 materials for pulse generators$20,000 10

July Relocated Equipment Laser room from Coherent electron cooling experiment will be used for LEReC laser room as well –Some reuse of transport path will also be possible Some reuse of existing 700 MHz laser system may be possible 11

July Location in LEReC 12 Laser Room Laser room location relative to the CeC experiment, also at 2 o’clock ~ 30 meter transport length

July Timeline Finalize pulse shape requirement: July 2014 Oscillator/modulator/preamp procurement December 2014 Amplifier design October 2014 Amplifier component procurement complete January 2015 Amplifier Construction complete March 2015 Operation for gun tests in bldg 912 Summer

July Summary Fiber rod based laser system with flexible pulse pattern 1 um fundamental, frequency doubled in LBO Fiber transport from 2 o’clock laser building to LEReC gun Available for gun tests in bldg 912 summer

July Backup

July Backup: parameters in upgrade case 16 REQUIRED AT PHOTOCATHODE (GREEN): 1.6 MeV2 MeV5 MeV gamma total charge per ion bunch QnC # e- bunches/ion bunch Q/ebunchpC laser pulse 1% QE nJ ion bunch rep rateMHz average rep rateMHz average currentmA avg laser 1%QEW peak power 10 psec FWHMkW peak power 50 psec FWHMkW LaserIRGreen energy/pulsenJ average powerW pulse width (FWHM)ps flat top107(stack to 50 ) Gaussian7050 peak powerkW flat top5531 (4.4 after stacking) Gaussian M intensity noise (rms)%12 jitter wrt RF (rms)psec11 Assumes 40% conversion efficiency Overhead of 5x or more in power capability