Modeling efforts on the Mercury Laser system Mercury Andy Bayramian, Camille Bibeau, Ray Beach Prop ’92 work: Ron White French Collaboration with MIRO:Olivier Morice, Bruno Legarrac, Marc Nicolaizeau, Xavier Ribeyre

UCRL-PRES Comparison of important spectroscopic and thermal properties between pertinent laser host / dopants Yb:S-FAP has the unique property of high cross sections and long lifetime allowing efficient pumping and extraction with a minimum number of diodes The low saturation fluence in S-FAP allows efficient extraction below typical material damage thresholds

UCRL-PRES Calculation of gain Pump Equations: Gain/Extraction Equations: (Franz-Nodvik) Feathered doping to equilibrate the gain through the amplifier head Symmetric pumping from left and right sides make gain profiles symmetric about center slab 77% of the diode pump light is transferred from the diode backplanes to the extractable area of the amplifier 13% of the diode pump light is transmitted through the amplifier due to pump saturation

UCRL-PRES Transfer efficiency of the pump delivery system output matches optical modeling data Diode Array Laser beam Gas - cooled slabs Hollow pump light homogenizer Hollow pump light concentrator Diode Array He gas in

UCRL-PRES Amplifier 1 Deformable Mirror Reverser Pockels Cell Amplifier 2 Relay plane 1.5 x output telescope lens The Mercury laser system minimizes damage by arranging the lenses, amplifiers, Pockels cell, and mirrors near relay planes Front End 3.5 meters Relay plane Relay plane

UCRL-PRES Advanced beam propagation modeling using MIRO a diffraction code developed by the French The MIRO code uses the paraxial wave equation with full diffraction and an adaptive mesh, which allows accurate modelling of a beam through an image relayed system MIRO results include: F(x,y,z,t) I(x,y,z,t) Pulse shaping B-integral

UCRL-PRES Current Mercury models show promising results Caveats to current modeling results Amplifier phase files are simulations Low frequency information lost due to small files Arbitrarily randomized to simulate multiple slabs Phase distortions on amplifiers only Thermal distortions not included yet Benchmarking in progress against Prop 92 and experiments E in = 20 mJ, E out = 83 J Energy through a 5X DL spot: 96.0% a 1X DL spot: 81.2% B-integral (5 ns): 0.7 radians Using  = 300 GHz bandwidth requires increase injection: E in = 165 mJ, E out = 85.0 J

UCRL-PRES B-Integral causes beam breakup as the pulswidth decreases below 1 ns 5 ns 1 ns 0.5 ns

MIRO OPTICAD: architecture delivery efficiency multiplexing angle VB 1D Pump: 1-way 1D abs/slab 1-way 1D gain/slab OPTICAD: 1-way 2D pump light deposition/slab VB 1D Extract: 2-way 1D gain/slab E, B-integral,  ASE, power density Fritz VB process: 2-way 2D gain/slab 2D norm. source desc. TOPAZ: 2D temp. distribution NIKE: 2D map of stress and displacement OPL: 2D thermal OPL map OPL PLOT: 2D thermal phase map Experimental: Wavefront, input, and loss measurements ZEEMAX/CODE V: Lense shape AAA drawings Expected wf error ghost analysis ASAP: Pinhole sizes Pencil beam analysis TEXTAN: Heat xfer coef. FIDAP: Diffuser design code flow chart.ppt ASE: Slab aperture limitations and geometry Edge cladding

UCRL-PRES Prop ’92 benchmarking of the MIRO code Front End PC L5b S1-S7 L5c M5 L5d Output Relay Plane G = 2 uniform flattop F sat = 3.0 J/cm 2 Per slab L5a FS2 FS1 Front end for first 4 propagations Energy = 0.1 J Wavelength = 1047 nm Temporal FWHM = 5 ns Time exponent = 50 Height FWHM = 2.8 cm Width FWHM = 4.8 cm Spatial exponent in X & Y = 20 Currently benchmarking simple propagation such that Energy, intensity, phase, and B-integral match Phase and gain files then added and re-verified Optional: The full mercury system modeled

UCRL-PRES Trivalent ytterbium shows high cross sections and long lifetime in the Sr 5 (PO 4 ) 3 F (S-FAP) host  em = 6 x cm 2  abs = 9 x cm 2  em = 1.14 ms Absorption Emission