Generation of warm dense matter using an argon based capillary discharge laser

Abstract

Argon based capillary discharge lasers operating in the extreme ultra violet (EUV) at 46.9 nm output up to 0.5 mJ energy per pulse at up to 10 Hz repetition rates are capable of focussed irradiances of 10 9 -10 12 W cm −2 and can be used to generate plasma in the warm dense matter regime by irradiating solid material. To model the interaction between such an EUV laser and solid material, the 2D radiative-hydrodynamic code POLLUX has been modified to include absorption via direct photo-ionisation, a super-configuration model to describe the ionisation dependant electronic configurations and a calculation of plasma refractive indices for ray tracing of the incident EUV laser radiation. A simulation study is presented, demonstrating how capillary discharge lasers of 1200 ps pulse duration can be used to generate warm dense matter at close to solid densities with temperatures of a few eV and energy densities up to 1 × 10 5 J cm −3 . Plasmas produced by EUV laser irradiation are shown to be useful for examining the properties of warm dense matter as, for example, plasma emission is not masked by hotter, less dense plasma emission as occurs with visible/infra-red laser target irradiation.

Perspective on Advances in Laser-Based High-Resolution Mass Spectrometry Imaging

“…According to the equation, reducing laser wavelength (λ) to the extreme ultraviolet (EUV) , or vacuum ultraviolet (VUV) − region makes it possible to focus the laser beam into a sub-100 nm spot, because of a reduction in the diffraction limit. In addition, by reducing the laser wavelength into the EUV region, direct photoionization becomes the dominant ionization mechanism as the plasma is transparent to the incident laser light. ,− The superior focus ability and specific interaction mechanisms enable EUV MSI to implement nanoscale resolution imaging. , Menoni and his co-workers combined the MSI with EUV (46.9 nm), achieving a lateral resolution of ∼240 nm (based on the probed crater area), an imaging resolution of 75 nm and a depth resolution of 20 nm to map the molecular composition of organic samples in 2015 . Such high imaging resolution has also been realized by the isotope distribution imaging of uranium oxide particles .…”

Extreme ultraviolet laser ablation of solid targets

“…The modeling and simulation of the interaction of 46.9 nm radiation with solid targets has been investigated in previous publications by the authors. The two-dimensional fluid code POLLUX was modified to include laser absorption by direct photo-ionization using a super-configuration model to describe the ionization dependent electron distributions [11]. Direct photo-ionization occurs in atoms with ionization energy less than the capillary laser photon energy (26.4 eV) so that solid target material is initially opaque to the laser radiation and bleaches to transparency as the material is ionized.…”

The creation of radiation dominated plasmas using laboratory extreme ultra-violet lasers

“…The plasma formed by lower irradiance (< 10 11 Wcm −2 ) EUV capillary laser irradiation of solid targets has been investigated [7], [9], [10], [11]. The critical electron density for EUV wavelengths in the range 10 -100 nm ranges from 30 10 25 − 10 23 cm −3 .…”