A simple cryostat for annealing spectra measurements in the temperature range 78 to 700 °K is described and its specifications are given. The rise time at the annealing temperature is chosen equal to 1.5 minutes, giving thus, a practically square shape of the temperature pulse. An analogue valve regulates automatically a stream of cold nitrogen gas and maintains the temperature of the samples constant within ±0.05 °C. The rise time varies from 1 min, or even less, to about 7 min, when there is no control of temperature through the cold gas.