# Optical Radiation during Sputtering of Lithium into a Noble Gas Using a Nanosecond Electron Beam
## 2 Materials and Methods
A hole for a CrAl-type thermocouple was drilled on the inner side of the cuvette. The temperature changes were recorded using a DTB 969 temperature controller. A hermectically sealed connector was installed on the lid of the experimental chamber for switching the thermocouple and the ohmic heater. The next step was to install the target node with the lithium CPS into the experimental chamber of the setup, which was pre-filled with argon. The next step was to fill the matrix of the metal CPS with lithium. In general, the procedure for the manufacture of lithium CPS was as follows:  
* Heat the lithium using the ohmic heater to a temperature of about 523 K and condition it at this temperature for 1 h under continuous vacuum pumping using a fore-vacuum pump;
* Supply the argon into the chamber up to a pressure of about 30 kPa;
* Heat the lithium target to a temperature of 773 K and condition it at this temperature for \(\sim\)45 min;
* Heat the lithium target to a temperature of 900 K and condition it at this temperature for \(\sim\)30 min;
* Let the temperature decrease to 573 K and condition it at this temperature for \(\sim\)15 min;
* Turn off the heating and pump the argon out from the installation chamber at a temperature of 453 K.  
During the visual observation from the quartz window, according to the outer view and typical metallic luster typically for lithium, it was found that the porous material was completely filled with lithium. A visual illustration, showing the complete filling of the metal mesh with lithium is shown in Figure 2 below. The chamber was covered with a white layer by the end of the measurements, including the quartz windows and the beryllium window. The layer was relatively easy to clean off, the dusting of the window had no noticeable effect on the light transmission. It is pointed out here that picture in Figure 2 was taken after the end of the irradiation of a lithium layer with an electron beam. The trace of the electron beam can be seen, as  
Figure 2: Appearance of lithium target after the irradiation with an electron beam. outgrowths, formed as a result of the lithium target heating to high temperatures during the measurements. The use of the above-described method of manufacturing a lithium target allowed for obtaining a lithium CPS with the required technical characteristics. The distance from the beryllium cathode window to the target was 30 mm. The irradiation chamber was filled with argon, krypton, or xenon at a pressure up to 60 kPa. The optical radiation was led out of the chamber through two quartz windows; light from the first window led through a 2m long fiber-optic cable to the QEPro-Abs spectrometer (Ocean Insight, Singapore). The emission spectrum was recorded in 15 s, with 20 pulses of the electron beam passed through during this time. The light from the second window was led through a 12 m long fiber-optic cable to another room to record the temporal parameters of the optical radiation, using the PDM02-9113-CN (ET Enterprises, Uxbridge, UK) photomultiplier module (PMT) and the MDR-204 monochromator. The photomultiplier was operated in current mode with a 50-Ohm load and the temporal signal was recorded on the screen of the Tektronix TBS2204B digital oscilloscope. The line intensities were measured using an optical spectrometer or PMT and are provided without correction for the spectral sensitivity of the setup.