IT is assumed that thermalization and high temperature have been achieved in ZETA1, although theoretical considerations demand a much longer period than that available for the process to take place2. This discrepancy between apparently observed and the theoretically expected thermalization time may be due to unknown processes occurring which speed up the process of thermalization2. This explanation, however, does not seem to be valid. Moreover, it is possible to explain most of the observed facts, if one assumes a ‘betatron type’ of acceleration of deutrons in ZETA, for the following reasons: