High-charge divergent electron beam generation from high-intensity laser interaction with a gas-cluster target (original) (raw)
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Study of the propagation of ultra-intense laser-produced fast electrons in gas jets
Journal de Physique IV (Proceedings), 2006
We present the results of some recent experiments performed at the LULI laboratory using the 100 TW laser facility concerning the study of the propagation of fast electrons in gas targets. Novel diagnostics have been implemented including chirped shadowgraphy and proton radiography. Proton radiography images did show the presence of very strong fields in the gas probably produced by charge separation. In turn, these imply a slowing down of the fast electron cloud as it penetrates in the gas, and a strong inhibition of propagation. Indeed chirped shadowgraphy images show a strong reduction of the electron cloud velocity from the initial value close to a fraction of c.
Plasma Physics and Controlled Fusion, 2019
An experimental study of laser driven electron acceleration in N 2 and N 2-He mixed gas-jet target using laser pulses of duration ~60-70 fs is presented. Generation of relativistic electron beam with quasi-thermal spectra was observed at a threshold density of ~1.6×10 18 cm-3 in case of pure N 2 , and the threshold density was found to increase with increasing doping concentration of He. At an optimum fraction of 50% of He in N 2, generation of quasi-monoenergetic electron beams was observed at a comparatively higher threshold density of ~2×10 18 cm-3 , with an average peak energy of ~168 MeV, average energy spread of ~21%, and average total beam charge of ~220 pC. Electron acceleration could be attributed to the direct laser acceleration as well as the hybrid mechanism. Observation of an optimum fraction of He in N 2 (in turn threshold plasma density) for comparatively better quality electron beam generation could be understood in terms of the plasma density dependent variation in the dephasing rate of electrons with respect to transverse oscillating laser field. Results are also supported by the 2D PIC simulations performed using code EPOCH.
Plasma Physics and Controlled Fusion
An experimental investigation on laser plasma acceleration of electrons has been carried out using 3 TW, 45 fs duration titanium sapphire laser pulse interaction with nitrogen gas jet at intensity of 2×10 18 W/cm 2. We have observed stable generation of well collimated electron beam with divergence and pointing variation ~ 10 mrad from the nitrogen gas jet plasma at an optimum plasma density around 3×10 19 cm-3. The energy spectrum of the electron beam was quasi-monoenergetic with average peak energy and charge around 25 MeV and 30 pC respectively. The results will be useful for better understanding and control of ionization injection and laser wakefield acceleration of electrons in high-Z gases and also to develop practical laser wakefield accelerators for various applications including injectors for high energy accelerators.
Plasma Physics and Controlled Fusion
An experimental study of laser driven electron acceleration in N 2 and N 2-He mixed gas-jet target using laser pulses of duration ~60-70 fs is presented. Generation of relativistic electron beam with quasi-thermal spectra was observed at a threshold density of ~1.6×10 18 cm-3 in case of pure N 2 , and the threshold density was found to increase with increasing doping concentration of He. At an optimum fraction of 50% of He in N 2, generation of quasi-monoenergetic electron beams was observed at a comparatively higher threshold density of ~2×10 18 cm-3 , with an average peak energy of ~168 MeV, average energy spread of ~21%, and average total beam charge of ~220 pC. Electron acceleration could be attributed to the direct laser acceleration as well as the hybrid mechanism. Observation of an optimum fraction of He in N 2 (in turn threshold plasma density) for comparatively better quality electron beam generation could be understood in terms of the plasma density dependent variation in the dephasing rate of electrons with respect to transverse oscillating laser field. Results are also supported by the 2D PIC simulations performed using code EPOCH.
Table-top laser-plasma acceleration as an electron radiography source
Laser and Particle Beams, 2006
A “table-top” high power laser has been used to generate beams of accelerated electrons up to energy of 20 MeV from interactions with underdense plasmas. The energy spectrum of these beams was measured using a magnetic spectrometer and proof-of-principle experiments were performed to evaluate the suitability of these beams for electron radiography applications.
Ultraintense Laser-Produced Fast-Electron Propagation in Gas Jets
Physical Review Letters, 2005
We study the propagation of fast electrons in a gas at different densities. A large relativistic electron current is produced by focusing a short-pulse ultrahigh-intensity laser on a metallic target. It then propagates in a gas jet placed behind the foil. Shadowgraphy in the gas shows an electron cloud moving at sub-relativistic average velocities. The experiment shows (i) the essential role of the density of background material for allowing propagation of fast electrons, (ii) the importance of the ionization phase which produces free electrons available for the return current, and (iii) the effect of electrostatic fields on fast-electron propagation.
Characterization of electron beams produced by ultrashort (30 fs) laser pulses
Physics of Plasmas, 2001
Detailed measurements of electron spectra and charges from the interaction of 10 Hz, 600 mJ laser pulses in the relativistic regime with a gas jet have been done over a wide range of intensities (10 18 -2ϫ10 19 W/cm 2 ) and electron densities (1.5ϫ10 18 -1.5ϫ10 20 cm Ϫ3 ), from the ''classical laser wakefield regime'' to the ''self-modulated laser wakefield'' regime. In the best case the maximum electron energy reaches 70 MeV. It increases at lower electron densities and higher laser intensities. A total charge of 8 nC was measured. The presented simulation results indicate that the electrons are accelerated mainly by relativistic plasma waves, and, to some extent, by direct laser acceleration.
Generation of high-energy electrons in a double gas jet and laser wakefield acceleration
IEEE Transactions on Plasma Science, 2000
High-energy electrons were generated by the synchronized interaction of a 2-TW laser beam with a nitrogen gas jet and a 10-TW laser beam with helium gas jet. The jets centers are separated by 0.5 mm distance and the propagation of the lasers are collinear. Plasma electrons were trapped and accelerated by the wakefields generated in the gas jet plasmas to above 20 MeV.