Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

Abstract

We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasma show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.

Effects of a static inhomogeneous magnetic field acting on a laser-produced carbon plasma plume

“…This configuration can be achieved by using two parallel magnets, which generate a magnetic field which is either transverse [24][25][26] or parallel [27][28][29] to the axial direction of the expanding laser plasma plume. Harilal et al 24 reported on the plasma dynamics and optical emission of an Al laser-produced plasma propagating in an almost uniform transverse ∼0.6 T magnetic field.…”

“…Pagano and Lunney 27 observed lateral confinement effects on a Cu laser-produced plasma propagating in a ∼ 0.3 T axial magnetic field, and reported an enhancement in the on-axis ion beam emission. Roy et al 28 investigated the extreme ultraviolet emission (EUV) of a Sn laser-produced plasma expanding in a 0.5 T axial magnetic field, in high vacuum. Although no significant effect on the EUV emission was observed, the off-axis ion beam emission was significantly reduced in the presence of the field.…”

“…The observed increase in the axial ion flux is also consistent with previous reports, 27 and also with an observed strong reduction in the off-axis flux when an axial magnetic field is applied, as reported elsewhere. 28 In this context, previous investigations show that at low laser intensities, ∼1 GW/cm 2 , as in this case, the dominant ion acceleration mechanism is gas-dynamical, as opposite to electrostatic, due to the high pressure gradients produced at the initial stages of laser plasma formation. 36 This can explain the long time scale for energetic ion emission, with characteristic ion energy decaying as the pressure gradients in the laser target region also decays.…”

Collimation of laser-produced plasmas using axial magnetic field

“…Laser-produced tin plasma has come up as a most promising and energy-efficient next generation EUV light source for the semiconductor lithography industry (Bakshi, 2009;Roy et al, 2014a;2014b). A high-brightness and debris-free source emitting at 13.5 nm radiation with 2% bandwidth (in-band) is necessary for this purpose.…”

“…In the field of inertial fusion, confinement of the expanding target plasma using a B-field offers a potential means to slow high-energy particles before they implant in the surrounding structures. The B-field is also used for controlling or diverting ion debris in extreme ultraviolet (EUV) lithography laser-produced plasma (LPP) sources (Harilal et al, 2006;Roy et al, 2014a;2014b).…”