Some optimum parameters of golay detector of infra-red radiation

The relation for the sensitivity of the pneumatic detector based on the analysis of the thermal, pneumatic and optical parts of the instrument is derived. From this relation the optimum diameter of the flexible mirror and the optimum gas pressure in the detector cell are calculated.List of symbols used B brightness sb] - C thermal capacity of absorbing membrane cal cm^–2 grad^–1] - c specific heat of gas in cell cal g^–1 grad^–1] - D diameter of grid cm] - d diameter of flexible mirror cm] - E illumination ph] - F ₂ area of light spot cm²] - F ₃ area of flexible mirror cm²] - f,f ₁ focal distance cm] - f ₀ chopping frequency of infra-red radiation sec^–1] - h depth of cell cm] - k radiation cooling constant cal cm^–2 sec^–1 grad^–1] - k ₀ reflectivity of flexible mirror - k ₁,k ₂,k ₃,k ₄ constants - L total length of edge of half of grid cm] - l distance between lens and flexible mirror cm] - M, N constants - m refractive power of flexible mirror cm^–1] - n number of grammolecules of gas in cell - P radiative power cal sec^–1] - p,p ₀,p pressure, atmospheric pressure, change in pressure dyne cm^–2] - R gas constant erg grad^–1] - r coordinate - r ₀ radius of flexible mirror cm] - r ₁,r ₂ radii of beam of rays cm] - t tension of flexible mirror dyne cm^–1] - , T, T _f absolute temperature and its change grad] - V, V volume and increase in volume cm³] - v coordinate - v ₀ maximum height of deflection of flexible mirror cm] - x, x distance of object and image from focal planes cm] - , angles - specific weight of gas at pressure of 1 atm. g cm^–3] - absorption coefficient of infra-red radiation - thermal conductivity of gas cal cm^–1 sec^–1 grad^–1] - v number of lines of grid per 1 cm cm^–1] - radius of light spot on grid cm] - T time constant sec] - ₀, ₁, ₂, ₃ light flux and its change lm]