1. Diagnostics for Benchmarking Experiments L. Van Woerkom The Ohio State University University of California, San Diego Center for Energy Research 3rd MEETING FUSION SCIENCE CENTER FOR EXTREME STATES OF MATTER AND FAST IGNITION PHYSICS

2. Overview High level of activity in establishing Z-Petawatt – Laser still under construction – Z machine takes priority – 2 postdocs, 5 grad students over several months Benchmarking  crucial to advance diagnostics – Laser diagnostics – Standard diagnostics – New techniques

3. Why are Laser diagnostics important? Proton production & focusing Temperature of proton irradiated foil from XUV images Size of proton irradiated region via XUV  dominated by target geometry Temperature strongly dependent on laser. Scatter in data probably due to laser

4. Why are target diagnostics important? Current seems to drop quickly near front surface mfp ~ 70  m d Big unresolved issues: No agreement in theory No agreement in codes Inability of experiment to provide sufficient information to discriminate amongst them Scale length on order of resolution Diagnostics must improve

5. Diagnostics Laser Diagnostics – Develop in-situ peak intensity monitoring – Build robust high dynamic range autocorrelator – Build robust prepulse/pedestal system Target Diagnostics – Standard techniques K  x-ray imaging  hot electrons XUV imaging  temperature profile HOPG spectra  temperature Streaked XUV  temporal heating – New techniques Time- and Space-resolved reflectivity Time- and Space-resolved polarimetry Space-resolved XUV spectroscopy

6. Laser Diagnostic Development Goals In-situ peak intensity monitor – – currently SNL – Directly measure intensity in focal region Third order single-shot autocorrelator – design and building at OSU – Gives time direction – Gives pulse fidelity out to ~100 picoseconds Pedestal measurement – design and building at OSU – Fast photodiodes – Plasma shutters for increased dynamic range

7. Intensity calibration Indirect method – Various laser parameters are measured outside the interaction region, from which peak intensity can be inferred Direct (in situ) method – Based on measurement of intensity dependent phenomena at the interaction region, intensity at the focus can be ascertained

8. Physics tells us about Laser Neon 1 + - 8 + We have a detailed understanding of high intensity laser atomic physics after two decades of extensive study. The laser has been used to understand the physics. Now, we use the physics to understand the laser. Highest charge states are well represented by current analytical atomic physics models and ratios of charge states from a single laser shot yield the peak focused laser intensity.

9. Pulse Width Measurement Making robust diagnostic tools, not reinventing the wheel Taking advantage of many years of short pulse high intensity laser research Along with the intensity measurement, this gives the actual experimental transfer function

10. Improvements in Standard Techniques Distinguishing models/codes requires improved resolution in space & time Improving spatial resolution requires – Crystal manufacturing – Mirror alignment – Careful optical design Improving temporal resolution – Streaked XUV – Streaked HOPG

11. New Diagnostic Development Chirped probe beam Pump beam Imaging spectrometer and polarization analyzer camera Anomalous near-surface physics Reflectivity & Polarization Temporal & Spatial Mapping Surface conductivity Magnetic fields A. Benuzzi-Mounaix, M. Koenig, J. M. Boudenne, et al., Physical Review E 60, R2488 (1999).

12. Experimental Scenarios Bragg crystal CCD HOPG Bragg crystal CCD

13. Who is doing what and where? Supported fully or in part by the FSC Core concentration at Sandia Z-Petawatt – J. Pasley  project coordinator – E Chowdhury  intensity measurement – D Offermann  intensity measurement & reflectivity – A Link  intensity measurement & Cu K  imager – N Patel  Cu K  imager – E. Shipton  optical interferometry Support work at OSU – D Clark  HOPG design & construction – J Morrison  reflectivity development – V Ovchinnikov  reflectivity & deformable optics XUV imaging spectrometer – A Link (will be in the UK over summer) Data archiving and information – J Young, R Weber, K Highbarger, N Patel

14. Summary & Conclusion Core efforts focused at Sandia Z-Petawatt Advancing the understanding of FI requires – Robust, reliable, in-situ laser diagnostics – Improved spatial & temporal target resolution – Development of a new generation of high spatial & temporal diagnostic technologies