Vacuum Tube Specifications:

(1) Inner glass tube diameter is 37mm, Outer glass tube diameter is 47mm.
(2) Tubes length is 1.5m.
(3) The material used for the all-glass evacuated tubes is borosilicate glass 3.3, which has a thermal expansion coefficient of 3.3?0-6 K-1.
(4) The selective absorbing surface is graded aluminum-nitrogen-carbon on an aluminum base layer (Al-N-C). The absorbance is up to 0.94(M1.5), and the emittance is around 0.07-0.08(at 80oC).
(5) The 5x10-3 Pa vacuum effectively inhibits out-gassing from the glass, and provides a high degree of insulation preventing convective heat loss from the inner tube.