Laser-Matter Interactions at SCARLET Science Center for Advanced Research on Lasers & Engineered Targets Linn Van Woerkom The Ohio State University Presented at the Fast Ignition Workshop 05 November 2006

Goal Develop techniques/protocols for the new generation of rep-rated Petwatt-class lasers Targets  mass production & insertion Diagnostics Data management Thus enabling systematic studies of ultraintense laser-matter interactions With ultimate GOAL of providing test-bed infrastructure for developing point designs for Fast Igniton

We are NOT ….. building a big, bad laser …..

Why Another Center? Currently there are many 20 – 200 TW lasers Many laser-matter processes studied Limitations due to low duty cycle –Need better statistics & reproducibility –Eventually need power plant Solution  Build high rep rate petawatt lasers Problem  What to do w/ rep-rated Petawatt laser? What about targets? –current targets ~$1-5k each  at 1 Hz that hurts –Need mass production What about diagnostics –Currently film packs used for many diagnostics What about data collection?  high data rates

The Team The Ohio State University –PI’s  L. Van Woerkom & R. Freeman –Optics & diagnostics  Dr. Enam Chowdhury –Facility & Integration  John Marketon General Atomics –PI  R. Stephens –Design  Neil Alexander + others Targeting collaboration with CLF at RAL, UK

The Place Nuclear Physics Van de Graaff Facility ~10,000 ft 2 total~10,000 ft 2 total ~3000 ft 2 High bay~3000 ft 2 High bay Lots of electricalLots of electrical Renovations in initial design phaseRenovations in initial design phase

The Place II

The New Place

The Plan Now  parallel efforts –OSU purchases 20 TW system 20 fs, 400 mJ, 10 pps Ti:S commercial system –OSU renovates Van de Graaff building –OSU develops rep-rated diagnostics –OSU develops data management systems –GA designs & builds prototype target carrier Test at LLNL and/or others Work with target designers at RAL, UK Move into new facility July 2008 –Upgrade laser to 250 – 1000 TW

Need Systematic Studies To explore efficiencies –Laser-electron  front surface morphology –Laser-proton  rear surface morphology To understand relativistic charge transport –Surface fields & resistivity –Transport in dense plasmas To develop diagnostic abilities –Transfer technology to large facilities On the road to a real point design ….. Real Progress  reproducible data  rep-rated systems

Requirements 0.1 – 1.0 Petawatt Peak Power PRR  10 shots/hour scaleable to Hz level Two short pulse beams Automated target insertion & alignment Automated focus correction on each shot Reasonable contrast ratio Highly diagnosed laser record of each shot Modular architecture  if $ stops we don’t

Concept Schematic 20 fs, 400 mJ, 10 pps Ti:S Front End 20 TW - Phase I Commercial System 20 fs, 4J, 10 pps Ti:S amplifier 200 TW – Phase II ~2009 Thermal loading issues Need to load w/o amplifying Feedback to adaptive optics Scaleable to higher PRR Adaptive optics diagnostic target must align to diagnostics laser must align to target 20 fs, 20J, 1 pps Ti:S amplifier 1-3 PW – Phase III (dreams are free) Rapid target insertion Rep-rated diagnostics

Must produce peak focused intensities in the range of Use ultrashort pulses  25 – 35 fs At 25 fs –1 PW  25 J/pulse J before compression ~ J/pulse pump energy for Ti:S Power & Energy Issues

Pulse Repetition Rate Issues Start “easy”  minutes between shots –We need the time for target manipulation –Scale later to hertz-ish rates Solve problems along the way to higher PRR

Alignment Procedure Issues Diagnostics  fixed point in space –How do we make it & find it? Align target to diagnostic center –How to align rep-rated targets? Align laser to target –straightforward using industrial technology? Maintain optimal focal properties –How do we move focus w/o destroying focus?

Target Insertion Issues Must handle 10 shots/hour & scale to faster Run several hours w/o venting target chamber Handle complex targets –Multilayers –Cones –Structures Must be economical!!?? Align target to diagnostic center –Use industrial machine vision –Advanced image processing Protect subsequent targets –Radiation issues? –Debris issues

Target Fabrication

Metrology & SCARLET Positioner A transfer standard is passed between the systems A reference target (e.g. a rigidly mounted cube) is put in the Metrology Station –Its center and orientation are noted Fiducial lasers (orthogonal) Fiducial cameras (orthogonal) Hexapod Positioner Fiducial lasers (orthogonal) Fiducial cameras (orthogonal) Hexapod Positioner Target Target camera and lens (orthogonal) SCARLET CHAMBER METROLOGY STATION Hexapod: Alio Industries

The Hexapod Hexapod for Prototype High Vacuum Version Hexapods made by Alio industries

Target System Attachment port for target magazine Optical table leg Vacuum chamber jacket around leg Target Elevator Hexapod

Target Handling Target Elevator Target Manipulator shaft Hexapod Target Alignment Tube and receptacle attach to hexapod here Target Assemblies will get dropped of here (tube will surround hexapod, shown here offset

Alignment Issues Diagnostics bolt onto fixed chamber Must maximize solid-angle real estate Some diagnostics use collection optics –K  & XUV –Can we move the collection optic and align to the target? What about laser pointing stability? –Must be “Titan-like” and then better know everything about everything on EVERY shot  AT HIGH REP-RATE

Conclusions SCARLET at OSU  laser-target facility –Look at rep-rated system issues TargetsDiagnostics Data Management –Goal is to develop the infrastructure for rep-rated HEDP We have the building –Design in progress –Phase I – Target Insertions + 20 TW laser ~Summer ‘08 GA designing targets & carriers & metrology Technology transferred to other facilities