Production of a high-density hydrogen plasma in a capacitively coupled RF discharge with a hollow cathode enclosed by magnets

A high-density hydrogen plasma with a plasma density higher than 10¹⁰ cm⁻³ is produced by a radio-frequency magnetized capacitively coupled discharge using a hollow cathode, i.e., a cylindrical hole inside the powered electrode surrounded by eight cylindrical neodymium magnets. The magnetic field is calculated to discuss the electron magnetization, i.e., the Hall parameter and Larmor radius of electrons. It is found that for 3 Pa of hydrogen gas pressure the maximum of plasma density estimated from the ion saturation current measured by a Langmuir probe at the center of the hollow trench, which is surrounded by the magnets, is approximately 1.7 times higher than that without the magnets. The addition of magnets results in an expansion of the high-density plasma region inside the trench. The uniformity of the radial profile of the plasma density is better in the presence of the magnets than that without the magnets.