6533b837fe1ef96bd12a1ede

RESEARCH PRODUCT

Ion source research and development at University of Jyväskylä: Studies of different plasma processes and towards the higher beam intensities

subject

description

MonPS16; International audience; The long-term operation of high charge state electron cyclotron resonance ion sources fed withhigh microwave power has caused damage to the plasma chamber wall in several laboratories.Porosity, or a small hole, can be progressively created in the wall on a year time scale, which cancause a water leak from the cooling system into the plasma chamber vacuum. A burnout of theVENUS chamber is investigated. Information on the hole formation and on the necessary localhot electron power density is presented. Next, the hot electron flux to the wall is studied bymeans of simulations. First, the results of a simple model assuming that electrons are fullymagnetized and strictly following magnetic field lines are presented. The model qualitativelyreproduces the traces left by the plasma on the wall and shows characteristic sub-patterns, whichare seen experimentally. However, it is too crude to reproduce localized power densities of theelectrons at the wall necessary to make a hole in the chamber wall. Second, the results of aMonte-Carlo simulation following a population of hot electrons into the ion source is presented.The simulation includes electron scattering. This time, a localized, high power density depositionto the wall results. A comparison between simulation and experiment is discussed in the case ofthe VENUS source. Finally, options to avoid hole formation in ECR ion sources chamber wallsare explored.