Carbon particle formation due to interaction between H2 plasma and carbon fiber composite wall

Formation of carbon particles due to plasma surface interaction has been studied using an electron cyclotron resonance (ECR) plasma device. The interaction produces two sizes of groups: small spherical ones of 2-25 nm in size and large particles of irregular shape and above 100 nm in size. The latter are considered to be flakes peeled from carbon films deposited on the reactor wall. The total amount and average size of small particles tends to decrease with increasing the sheath voltage V_s between plasma and the carbon fiber composite (CFC) wall from 14 to 214 V. Optical emission intensities of CH and C as well as gas absorption rate to the CFC wall also decrease with increasing V_s. These results suggest that the carbon-containing species emitted from the CFC wall contribute to formation of small particles.