Study of plasma characteristics for KOMAC microwave ion source using optical emission spectroscopy

The Korea multi-purpose accelerator complex 100 MeV proton linac uses a 2.45 GHz microwave ion source. In this study, an ion source test stand was constructed to perform various microwave ion source tests. Certain structural modifications, including increasing the solenoid electromagnet size and water cooling of the plasma chamber, were implemented. Note that the operation parameters related to plasma in the ion source are vacuum pressure (hydrogen flow rate), microwave power, and the solenoid electromagnet current. Optical emission spectroscopy (OES) analysis was performed to confirm the effect of plasma characteristics, such as electron density and temperature, on beam formation. Characteristic plasma experiments on the microwave ion source revealed some structural changes in the ion source, but electron densities remained unchanged, suggesting no changes in the beam characteristics of the ion source. This paper presents the process of structural change according to the microwave ion source, improvements in the ion source test bench, and plasma characteristics of the ion source using OES.