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Contribution of the Wigner Institute

Contribution of the Wigner Institute. Imre F. Barna. Outline. - Our Starting Point , just to Remember - E xperimental Setup & Recent Results - Theoretical Work & Recent Results. Starting Point & Requirement. Figure is taken from Patric Muggli .

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Contribution of the Wigner Institute

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  1. Contribution of the Wigner Institute Imre F. Barna

  2. Outline - Our Starting Point, just to Remember - Experimental Setup& Recent Results - Theoretical Work & Recent Results

  3. Starting Point & Requirement Figure is taken from Patric Muggli  Homogenous ionization of Rb gasis needed!!! How to do it?? This is the coupling point for Wigner Institute

  4. Our idea to create homogenous plasma Idea: use the short laser pulse to populate the 7s and 5d two-photon resonant excited states to enhance the total single-ionization cross sections in the laser-Rb interaction and create a homogeneous plasma J. S. Bakos et. al European Physical Journal D, 44 (2007), p. 141 (Model: a laser-atom excitation calculation including propagation phenomena) Rubidium-85 energy levels

  5. The Experimental Setup - A fs laser with high repetition rate Vacuum chamber with 10-6 mbar Rb dispenser atomic beam source MCP detector to detect the ions/electrons later plasma diganostics till now approx. 4 KEuro investment two local grants are for 13 KEuro

  6. Output parameters of the laser system Typical values 806 nm 4.1W 9 mm (1/e2 ,Gauss) Linear, vertical 1 kHz 35 fs 0.25% 800nm 30nm Parameters Mean wavelength Average Power Beam Diameter: Polarisation: Repetition Rate Pulse duration (FWHM): Energy. stab. rms (%): Medium wavelength: Bandwidth (FWHM):

  7. The Femtosecond Lab

  8. The Femtosecond Lab Primary laser source - fs-duration system: Ti:sapphire oscillator + regenerative amp. P. Dombi, A. Czitrovszky, P. Rácz, Gy. Farkas, N. Kroo, I. Földes use the laboratory for HHG experiments, surface plasmons Clean room: 3000-4000 particles/foot3

  9. HELIOS 1 – 1 KHz, 4,3 mJ, 31 fs

  10. The Vacuum Chamber Pressure: 10-6 mbar large enough for the source and the MCP

  11. Rubidium Atom Source MCP detector approx 1010 particles/cm3 getter current 4.5 A at 2 V Laser Rb atom beam source (dispenser)

  12. General Overview of the Experimental Setup Mirror Shutter to cut 5-10 pulses Mirror

  13. Recent experimental results The three photon ionisation proccess is almost measured Laser parameters: Mean wavelength: 800 nm Beam diameter: 9 mm (1/e2 ,Gauss)NO focusing Max: Intens 1011 W/cm2 varied via Q-switch Far from being ideal Polarization: Linear, vertical Repetition rate: 1 kHz Pulse duration: 35 – 45 fs

  14. Recent Experimental Results&Direct MCP Signal The signal of the MCP was closed with 50 Ohm in the oscilloscope, the noise was filtered with a 11 point smoothing algorithm, saturated ionisation current is measured

  15. Improvements a polarfillter will be applied the slit of the ion getter will be enlarged the atom beam becomes more stable later a 50 cm long ion-source is planned to use, with 2-3 MCPs to detect ionization currents

  16. Theoretical Works Direct relativistic mechanical calculations for electron acceleration in underdense plasma MSc Thesis, Mr. Pocsai Improve the quantum optical calculation, to include ionisation states for the Rb gas Quantum optical improvement of PIC simulations for electron acceleration Phd work Mr. Pocsai

  17. Electron Acceleration in Underdense Plasma The relativistic Newtonian equations of motion Lorentz force External fields Chirped pulse Retarded time in vacuum & underdense plasma Index of refraction

  18. Electron Acceleration in Underdense Plasma Laser parameters: Wavelength: 800 nm Intensity: 1017W/cm2 Pulse length: 35 fs Only downchirp causes acceleration, the sharpest edgedoes the job. Downchirp = a dephasing effect The plasma parameters at n = 1015 cm-3 nm =0.9999997 basically no diference from vacuum solutions

  19. Results Energy gain vs. Initial momentum The direction of pulse propagation The direction of injection

  20. Results Energy gain vs. Carrier–envelope phase and laser pulse length

  21. Results Energy gain vs. the chirp parameter and laser intensity

  22. Colleagues & Publication Published: Nucl. Instr. And Meth. in Phys. Res. A 740, (2014) 203-207 arXiv: 1309.2442

  23. Thank you for your attention!

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