Excess Noise in Superconducting Bolometers

A large excess of noise above that expected on the basis of thermal fluctuations has been observed in the output of thin-film Sn superconducting bolometers. The noise spectrum has been measured from 50 Hz to 4 MHz, with an additional measurement at 30 MHz as a function of applied magnetic field. The excess noise in the 100 KHz to 30 MHz range is found to be damped by the application of a perpendicular field of from 3 to 15 G. There is a $\frac{1}{f^2}$ component at lower frequencies which is believed to be due to the detection of acoustic bubbling in the liquid helium. This portion of the noise was not affected by the application of a magnetic field.