Impurity control of tokamaks with in situ metal deposition

The article of record as published may be found at http://dx.doi.org/10.1016/0022-3115(80)90345-1Metal coatings of titanium and chromium of different thickness were deposited in situ in microtor and macrotor tokamaks and tested for impurity control. To improve the microstructure of the metal deposit, Ti and Cr were evaporated at a slow rate of about 20 Å/h during discharge cleaning. A 200 Å fresh metal deposition is required to obtain oxygen free surface layers. The oxygen control by Cr deposits was comparable to the one with Ti coatings. The hydrogen recycling rate increased markedly for Cr deposits. Control measurements show that the problem of hydrogen and deuterium retention in the metal coating during a switchover from one gas to the other can be overcome by short time outgassing to 650 K.US Department of EnergyGrant No. DE-AM03-76SF0001