Performance Characteristics of a New Low-Temperature Bolometer

Abstract

An infrared bolometer detector designed to operate at liquid helium temperatures has been constructed by using the core of a carbon composition resistor as the sensitive element. We have made use of the well-known fact that the temperature coefficient of resistance of certain commercial carbon resistors is extremely large at low temperatures. Since the specific heat at these temperatures is small, it has proven to be relatively simple to construct a detector with a time constant of the order of milliseconds and a signal-to-noise figure surpassing any other known thermal detector of radiation. Furthermore the resistivity of the material is such that most of the radiation striking the surface is absorbed even at frequencies in the far infrared. A brief discussion of the noise to be expected under nonequilibrium conditions is given. In practice it is found that current noise is about an order of magnitude larger than all other sources of noise.