Development of dielectric de Laval nozzles for laser electron acceleration by ultrashort pulses micromachining

Laser-machined two-stage nozzle optimised for laser wakefield acceleration

“…Although additive manufacturing processes like stereolithography and selective laser sintering are also limited to throat diameters down to 1 mm, complex channels are manufactured in a single step (Döpp et al 2016;Andrianaki et al 2023). Femtosecond laser-induced chemical etching (FLICE), laser trepanning and electrical discharge machining (EDM) can be used to produce diameters smaller than 100 µm (Takahashi et al 2013;Tomkus et al 2019;Chiomento et al 2021;Zuffi et al 2022). However, de Laval-shaped channel formation is typically a two-step process for laser trepanning and EDM techniques (Li et al 2018;Chiomento et al 2021;Zuffi et al 2022).…”

Creation and spatial-temporal characterization of gas targets and plasmas for laser-electron acceleration

“…All these features make ultrafast laser micromachining ideal for fabricating nozzles for our experiments. Thus, de Laval nozzles were initially manufactured on metallic substrates using ultrafast laser micromachining by the percussion method [116,119] . Figure 5.2 presents topographic maps obtained by optical profilometry (Zegage, Zygo Inc.) of a typical nozzle exit and throat on a 0.5 mm thickness copper substrate, manufactured by laser pulses with an energy of ℰ S = 150 µJ that were focused by an f = 50 mm achromatic doublet.…”

“…The results exhibited in Figure 5.2 lead our group to look for other approaches to manufacture nozzles aiming to get circular holes. This was obtained by modifying the machining process from percussion to trepanning, and replacing the metallic substrates with dielectric materials [116,180,192] . The trepanning method rotates the substrate in which the nozzle is being manufactured, while the laser acts as a cutting tool displaced from the rotating axis, smoothing out the laser beam inhomogeneities and preserving the cylindrical symmetry.…”

“…Particle-in-cell (PIC) simulations have been showing us the possibility to generate tens of MeV electron bunches by SM-LWFA, using TW or sub-TW laser pulses and gaseous targets with submillimetric dimensions [58,111,112,113,114] . In addition to computational PIC simulation support, we are currently focusing efforts on several developments required for a LWFA installation, such as a source of high-peak-power laser pulses [115] , proper gaseous and plasma target creation [116,117] , and development and implementation of diagnostic tools to assist and monitor the experiments [118,119] .…”

“…During this PhD, I worked on the development of techniques to manufacture micrometric de Laval nozzles by ultrafast laser micromachining [116,120] . We established a methodology to manufacture high-quality de Laval nozzles by ultrashort laser pulses trepanning on alumina substrates (Al2O3), a dielectric ceramic.…”