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SMURF

SMURF. II. The return of the tiny blue beasts. SMURF 1 quick recap. 2 orders of magnitude increase in signal. Extension of cut-off energy of a factor of 2. SMURF 1 quick recap. Most features reproduced by single atom SFA.

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SMURF

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  1. SMURF II The return of the tiny blue beasts

  2. SMURF 1 quick recap 2 orders of magnitude increase in signal. Extension of cut-off energy of a factor of 2

  3. SMURF 1 quick recap Most features reproduced by single atom SFA. Now will need to try and taken phase matching into account to increase absolute on top of relative photon numbers.

  4. SMURF 1 quick recap SMURF field ionises less than single colour fields: can push to higher intensities

  5. Water-window X-rays • Defined as the energy region between the carbon K edge (284eV) and the oxygen K edge (543eV) • Transparent to water but highly absorbed by carbons • Very good for imaging biological samples • HHG is one of the most promising sources of water-window X-rays.

  6. Who’s done what when and how? • Ti:Sapph • 5fs, 720nm pulse to generate 1keV photons (very few) Seres and co. 2005 • Using QPM they increased their photon yields in WW

  7. Who’s done what when and how? • Mid-IR • 1.6um, get 450eV, tune PM with pressure, Takahashi, 2008 • 1.5um, very efficient WW X-ray using fibre, KML, 2009 • 1.5um from HE-TOPAS, 400eV, Xiong, 2009 • 800nm+1300nm, SAP from long pulses, no CEP lock, Takahashi, 2010

  8. Who’s thought of what when? • Scaling of HHG efficiency above 500eV more favourable at mid-IR, Gordon, 2005 • Scaling of HHG efficiency above 500eV even more favourable at mid-IR with SMURF, Lan, 2010

  9. Set-up Variable reflector wheels RD 800nm 1.5 mJ 8mJ HE TOPAS Idler 0.5mJ ? HHG Signal 0.5mJ combination

  10. Wavelengths • 800 nm, 1.5mJ, 35fs • signal +idler, 0.5mJ ish, 50fs

  11. 8mJ 7.5 mJ 450 uJ 50 uJ Dichroic mirrors Dispersive Glass block BBO signal BBO WLC idler 800 nm dump 800 nm dump insides of the TOPAS

  12. Steps • 800nm + signal • 800nm + idler • Signal + idler • Triple whammy!

  13. piezo piezo Gas jet • Use attotech: • Free expansion • Interaction length • 0.5mm to 1mm • Gaussian ish profile • Tube extension • Interaction length • 5mm to few cm • Linear ish ramp

  14. Beam combination

  15. Focussing • Need to balance intensity and number of emitters • Long focal: less I, more emitters • Short focal: less emitters, more I • HHG cut-off scales as F^2 • HHG intensity scales as F^4 • IR: 0.5mJ, 50fs F=20cm: Ipeak=3.5e14W/cm2

  16. Target density • From KML work: low density can favour phase matching over long distances (if no Gouy shift) • Short gas jet limit: HHG intensity increases as N^2: the more the better • Worth going to solenoid gas jet to increase density further?

  17. Detection • Flat field spectrometer: go to 2400 lines/mm for SXR detection • MCP or andor camera? Andor has potential for photon counting but need to block IR efficiently and account for filter transmission and quantum efficiency. • Calibrated vacuum photodiode (where can you get one from?)

  18. Filter wheel detector XUV Gas jet slits SXR IR FF grating 2mm differential pumping hole Movable Xray vacuum photodiode Inside vacuum chamber

  19. Any moresuggestions???

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