Measuring temperature on an isolated sample is quite difficult. One option was to use a pyrometer but it could be problematic to measure through the quartz glass tube in the chamber. The other option is to use thin thermocouples attached on the test specimen. One problem is to insert them through the chamber without resulting in gas leakage. However, that is a later problem that I think we can manage to fix. I found some nice thermocouples at Pentronic which are reusable, which is good since they are quite expensive. The type I bought was Pt-Rh type S. By burning off the isolation, the Pt- and Rh-threads can be welded to receive a good spot for temperature measuring.