Sentence:  It is sufficiently small compared with the surface temperature of the anode holder , to make the <WSD>energy</WSD> flux radiated from the environment toward the anode holder negligible within the accuracy of the present measurements . 
Meaning of the word marked with <WSD> tags:  (physics) a thermodynamic quantity equivalent to the capacity of a physical system to do work; the units of energy are joules or ergs