Excess Noise in Superconducting Bolometers

Abstract

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 l// 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.

Effects of Dynamic External Pair Breaking in Superconducting Films

“…ability ?7^7xlO" 2 , taking the conversion efficiency of the light power F = \. This is in reasonable agreement with values estimated by combining experimental Kapitza resistance measurements 5 and theory. 6 In principle, one may attempt to obtain the intrinsic 7 recombination time T R -{2N T R)~l either from extrapolation of data like that in Fig.…”

“…The luminescence from the condensed phase, which has been observed in Si 1 and Ge, 2 indicates (from the low-temperature line shape 2 " 4 and its temperature dependence 4 ) that the condensate is an electron-hole liquid. While it is well established that excitons exist at low carrier densities in the gas phase, 5 we shall present evidence that the gas is an electron-hole plasma at high densities near the critical point. We shall discuss only briefly the transformation between excitons and plasma, since it is not as yet understood.…”

Noise Limitations of Miniature Thermistors and Bolometers

“…Therefore the 1/f noise is practically absent in bolometers having transition temperature in the 1…10 K range. However, the statistical fluctuation of the temperature can be observed (Maul et al, 1969).…”

Transition-Edge Sensors

“…Aside from ITFN, excess electrical noise with the same frequency dependence as Johnson noise has been observed by multiple research groups using many different TES geometries and materials [6,7,64,25,65,66,67,68] (see Fig. 5).…”

“…One of the principal barriers to their adoption was the difficulty of matching their noise to FET amplifiers (the TES normal resistance is typically a few ohms or less). In order to noise match, the TES was sometimes read out using a cross-correlation circuit to cancel noise [6], ac biased in conjunction with a step-up transformer [7], or fabricated in long meander lines with high normal resistance [8,9]. In recent years, this problem has been largely eliminated by the use of superconducting quantum interference device (SQUID) current amplifiers [10], which are easily impedance-matched to low-resistance TES detectors [11,12].…”