A thermal 0.8 m3enclosure with submillikelvin stability

The authors have constructed a thermally insulated box-shaped enclosure of approximate (1*1*0.8) m internal dimensions to carry out precision measurements at room temperature. The design of the enclosure is based on the solution of the heat conduction equation by a finite-difference approximation method. Temperature measurements carried out inside the enclosure in consecutive periods of eleven days over a four-month interval show that the stability obtained lies within +or-0.5 mK h -1 and the gradients are less than 50 mu K mm -1 . The power spectrum analysis, via a fast Fourier transform (FFT) technique, shows the still significant components inside the insulating enclosure.