Journal Article

PreJuSER-5853

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Optimized K alpha x-ray flashes from femtosecond-laser-irradiated foils

Lu, W. ; Nicoul, M. ; Shymanovich, U. ; Tarasevitch, A. ; Zhou, P. ; Sokolowski-Tinten, K. ; von der Linde, D. ; Masek, M. ; Gibbon, P.FZJ* ; Teubner, U.

2009
APS College Park, Md.

This record in other databases:  

Please use a persistent id in citations: http://hdl.handle.net/2128/9322  doi:10.1103/PhysRevE.80.026404

Abstract: We investigate the generation of ultrashort K alpha pulses from plasmas produced by intense femtosecond p-polarized laser pulses on Copper and Titanium targets. Particular attention is given to the interplay between the angle of incidence of the laser beam on the target and a controlled prepulse. It is observed experimentally that the K alpha yield can be optimized for correspondingly different prepulse and plasma scale-length conditions. For steep electron-density gradients, maximum yields can be achieved at larger angles. For somewhat expanded plasmas expected in the case of laser pulses with a relatively poor contrast, the K alpha yield can be enhanced by using a near-normal-incidence geometry. For a certain scale-length range (between 0.1 and 1 times a laser wavelength) the optimized yield is scale-length independent. Physically this situation arises because of the strong dependence of collisionless absorption mechanisms-in particular resonance absorption-on the angle of incidence and the plasma scale length, giving scope to optimize absorption and hence the K alpha yield. This qualitative description is supported by calculations based on the classical resonance absorption mechanism and by particle-in-cell simulations. Finally, the latter simulations also show that even for initially steep gradients, a rapid profile expansion occurs at oblique angles in which ions are pulled back toward the laser by hot electrons circulating at the front of the target. The corresponding enhancement in K alpha yield under these conditions seen in the present experiment represents strong evidence for this suprathermal shelf formation effect.

Keyword(s): J ; copper (auto) ; electron density (auto) ; high-speed optical techniques (auto) ; plasma density (auto) ; plasma production by laser (auto) ; plasma simulation (auto) ; plasma X-ray sources (auto) ; titanium (auto)

Note: This work was supported by the Deutsche Forschungsgemeinschaft (Contract No. SFB 616 and Grants No. GI 300/3-1, No. TE 190/6-1, and No. So 408/6-3) and the European Union (Marie-Curie-network FLASH).

---

Contributing Institute(s):

1. Jülich Supercomputing Centre (JSC)

Research Program(s):

1. Scientific Computing (P41)

Appears in the scientific report 2009

---

Database coverage:
;

---