This paper describes a mirror furnace that has been developed for neut
ron diffraction work at temperatures up to 2300 K. It is based on a re
flecting rotational ellipsoid, in which the heating element, a halogen
lamp, is placed at one focus and the sample at the other. It works in
a normal, i.e. oxidizing, atmosphere, but can also be used in a vacuu
m. It has been developed for experiments of long duration. The stabili
ty and reproducibility of the temperature are better than 1% of the se
tting temperature. Further main characteristics are applicability to s
ingle-crystal and powder work, very low background, low power consumpt
ion and very easy and cheap handling. Several experiments have been ca
rried out with the furnace.