# Optical Radiation during Sputtering of Lithium into a Noble Gas Using a Nanosecond Electron Beam
## 2 Materials and Methods  
The research was carried out on the experimental setup, as shown in Figure 1.  
An X-ray tube with an explosive cathode generates an electron beam, with an energy of about 150 keV and a duration of 5 ns [12]. The electrons were led into the gas through a 150 \(\upmu\)m thick beryllium window. The calculations were performed using the Casino software to estimate the energy of the electrons at the output from the beryllium window. The Casino software uses the Monte Carlo method to simulate the interaction of a beam of electrons and matter and can be used to calculate the interaction of the low-energy electrons with the solids [13]. This program is widely used in studies of cathodoluminescence [14; 15] and lasers with electron beam pumping [16]. It has been shown in [17] that Casino is quite precise (maximum error 10%) to simulate an electron pathway with energy of about 10 keV. The following conditions were chosen for the simulation:  
* Mono-energy electrons with an energy of 150 keV were used;
* The minimum energy of the initial electrons monitored using the software was 0.05 keV;
* The possibility of secondary electron formation through the collisions of the initial electrons in the beryllium window was considered. The simulations using the Casino software showed that the electron energy at the output from the beryllium window ranges from 0 to 105 keV, with an average electron energy of 49 keV. To simulate the processes during the excitation of the noble gas atom and lithium caused by the \({}^{6}\)Li(n,\(\alpha\))\({}^{3}\)H nuclear reaction products, a special target node was developed. The target node consisted of a metal cuvette, on which an ohmic heater, a 30 mm diameter lithium capillary porous structure (CPS), a movable rod enabling adjustment of the distance of the lithium target from the cathode, an ohmic heater, connected to a ceramic-insulated hermetic connector, a Cr-Al-type thermocouple, and leads for thermocouples and current leads were attached. A DC power supply (B5-21) was used in the manufacturing process of the lithium CPS, which produced a continuously adjustable DC stabilized voltage and a current. As a CPS, a matrix of 12 Cr18 Ni10 Ti stainless steel was used, which was a woven mesh with a cell size of about 100 \(\upmu\)m and a thickness of 0.1 mm. CPS was used to ensure the stabilization of the lithium in the liquid state during the experiments above the melting point of lithium. The lithium target was mounted on the top of the viewport with a slight angle of inclination. The tilt angle of the lithium target did not exceed 5\({}^{\circ}\). The temperature of the lithium target was measured using a thermocouple and the gas temperature was not controlled. Figure 1: Scheme of the experimental setup. Lithium CPS was directly fabricated in the experimental chamber of the experimental setup. For these purposes, a cuvette with a diameter of 30 mm was created. A 12 Cr18 Ni10 Ti stainless steel cuvette was clamped with a washer for a snug fit with the rod. Before the preparation of the lithium target, the CPS matrix was placed in a solution of concentrated nitric (HNO\({}_{3}\)) acid and washed in alcohol in stages, using a ProsKit SS-803F ultrasonic cleaner. The methods, techniques, and procedures for purifying lithium metal used in this work are described in detail in the monograph _Lithium_[18]. The CPS matrix filling procedure using lithium was carried out using previously developed and experimentally tested techniques [19]. The procedure of loading lithium into the cuvette was carried out in an argon box to minimize the interaction of lithium with impurities (N\({}_{2}\), CO\({}_{2}\), O\({}_{2}\), H\({}_{2}\), etc.). Further, the stainless-steel mesh was spot welded into the cuvette with the loaded lithium. To achieve a more uniform heating of the test sample and minimize the temperature gradients over the volume of the lithium CPS, an ohmic heater was wound around the outer circumference of the target.