High-quality stable electron beams from laser wakefield acceleration in high density plasma

Abstract

High-quality, stable electron beams are produced from self-injected laser wakefield acceleration using the interaction of moderate 3 TW, 45 fs duration Ti:sapphire laser pulses with high density (>5 × 10 19 cm −3 ) helium gas jet plasma. The electron beam has virtually background-free quasimonoenergetic distribution with energy 35.6 þ3.9 −2.5 MeV, charge 3.8 þ2.8 −1.2 pC, divergence and pointing variation ∼10 mrad. The stable and high quality of the electron beam opens an easy way for applications of the laser wakefield accelerator in the future, particularly due to the widespread availability of sub-10 TW class lasers with a number of laser plasma laboratories around the world.

Electron radiography with different beam parameters using laser plasma accelerator

“…Furthermore, L > λ p would also lead to an overlap of injected electrons with the laser field, and, hence, a contribution of the transverse laser electric field, i.e., DLA, should also be applicable [3][4][5][6][7]. Generally, collimated high-energy QM electron beams are observed from the wakefield mechanism of acceleration [43,44], similar to the case of He in the present experiment. On the other hand, from the DLA mechanism comparatively larger divergence electron beams with broad spectra are observed [3][4][5][6][7] as seen in the case of Ar.…”

“…In the present experimental conditions, the laser pulse length (L ¼ cτ, where c is the velocity of light and τ is the laser pulse duration) is longer than the plasma wavelength (λ p ) and, therefore, falls in the regime where selfmodulation of the laser pulse may lead to a wakefield excitation and acceleration of electrons known as selfmodulated laser wakefield acceleration (SM-LWFA) [1,[39][40][41][42][43][44]. Furthermore, L > λ p would also lead to an overlap of injected electrons with the laser field, and, hence, a contribution of the transverse laser electric field, i.e., DLA, should also be applicable [3][4][5][6][7].…”

Quasi-monoenergetic electron beams from a few-terawatt laser driven plasma acceleration using a nitrogen gas jet

“…The gas jet was well characterized for number density of gas atoms at different backing pressures using interferometry measurements [23]. The focused laser pulse when interacts with the nitrogen gas, the nitrogen atoms will be tunnel ionized to N 5+ state by the foot of the laser pulse at intensity ~ 110 16 W/cm 2 and further ionization to N 6+ requires intensity ~ 110 19 W/cm 2 which is 5 times the peak intensity of the laser pulse at focus in vacuum. We estimate the plasma density in the interaction region accordingly from the known number density of nitrogen atoms for a given backing pressure of the gas jet.…”

Design of a double dipole electron spectrometer

“…8 In this case, the initial angle of the electron beam in the dipole is unknown, which can lead to an error in determining the energy. This effect can be mitigated using a collimator 17 which allows the reduction of the incoming angle uncertainty but has the disadvantage of decreasing the charge and increasing the emittance. An imaging system (magnetic 18,19 or a plasma lens 20,21 ) can reduce this effect for a given energy range at the cost of a lower charge and a larger footprint.…”