Use of the alpha->beta quartz transition to monitor the temperature increase produced by a proton microbeam

Ion microbeams induce in certain cases local heating of a sample under investigation, especially in insulators. To obtain experimental values of this temperature increase, we used a quartz sample which presents its own internal thermometer with the alpha-->beta transition observed at 573 degrees C. At this temperature, the transition is easily observed from the rapid variation of the bubble size contained in a melted inclusion trapped in the quartz. We measured the temperature increase produced by a 3 MeV proton microbeam. For this purpose, the nuclear microprobe chamber was equipped with a sample heating stage. The decrease of the power injected by the heater element (beam on) required to observe the transition has been interpreted as a local increase of the temperature under microbeam exposure.