# Linear Plasma Device for the Study of Plasma-Surface Interactions
## 2 Materials and Methods  
The developed experimental plasma installation, KAZ-PSI, is versatile and allows for materials testing under the combined influence of both plasma flux and high thermal loads generated by an electron beam. The use of this plasma installation provides the capability to promptly obtain preliminary experimental data on the behavior of materials under conditions associated with their interaction with plasma at high thermal loads [15]. The overall appearance of the linear plasma installation KAZ-PSI is shown in Figure 1a. The main elements of the plasma installation shown in Figure 1b consist of a plasma-beam discharge chamber, an interaction chamber, an electron-beam gun, a target assembly, and a system of magnetic coils. The electron-beam gun consists of a cylindrical cathode (LaB6) and an anode ring, separated by a ceramic insulator. The cathode is heated in a resistive way, with a constant current source providing up to 25 kW of power. The vacuum chamber consists of a discharge chamber and an interaction chamber. The discharge chamber is made in the form of a narrow cylinder 1 m long and 0.15 m in diameter. The interaction chamber is designed as a complex assembly with six ISO160 flanges. The target assembly contains a holder in which retaining elements in the form of spouts are installed to place the target in them. The target holder is a hollow cylinder with a diameter of 80 mm which has pipe connections for water cooling. The vacuum pumping system comprises a backing pump and a turbomolecular pump, and is capable of maintaining residual gas pressure in the chamber at a level of 5\(\cdot\)10\({}^{-8}\) Pa. The typical base working pressure is on the order of 5\(\cdot\)10\({}^{-4}\)-5\(\cdot\)10\({}^{-5}\) Pa. The gas injection system consists of vacuum-leak valves designed to introduce gas into the vacuum chamber with a controlled flow rate within a strictly specified small range, allowing for smooth adjustment. The power supply system encompasses power units for electromagnetic coils, vacuum pumping means, diagnostics, cooling, parameter monitoring, and the source providing negative potential to the target. It also includes a complex set of power supplies for the electron beam gun, comprising a DC power supply for the heater unit and an adjustable high-voltage unit for shaping the primary beam of the plasma-beam discharge. The diagnostic system comprises a quadrupole mass spectrometer, a Langmuir probe, and pyrometers. The control system incorporates computer programs for remote control of the installation components. In Figure 2, a schematic representation of the linear plasma installation KAZ-PSI is depicted. The operation of the plasma installation unfolds as follows. The electron gun forms an axially symmetric electron beam. The gun's cathode is heated using a tungsten filament. The cathode heating power regulates the power of the gun. Upon the introduction of the working gas into the discharge chamber, the electron beam interacts with the working gas, giving rise to a plasma-beam discharge. Figure 1: General view and essential elements of the linear plasma installation KAZ-PSI. (**a**) General view of the installation; (**b**) Installation diagram. The working gases employed include hydrogen, deuterium, helium, and others. The focusing of the plasma beam is achieved through the use of electromagnetic coils which generate a longitudinal magnetic field in the discharge chamber. The magnetic field strength is adjusted by varying the electric current flowing through the electromagnetic coils. The plasma beam impinges upon the target (test material) positioned in the plasma receptacle located within the interaction chamber. To ensure a high ion concentration and attain the maximum power of the plasma flow without disruptions, a negative accelerating potential of up to 2 kV is applied to the target using the PCH6000-20H power supply. The Langmuir probe is used to determine the parameters of the plasma flow. An electric conductor is placed in the plasma, depending on its potential [16].