Josephson Effects in Frequency-Domain Multiplexed TES Microcalorimeters and Bolometers

Abstract

Josephson Effects in Frequency-Domain Multiplexed TES Microcalorimeters and Bolometers Gottardi, L.; Smith, S. J.; Kozorezov, A.; Akamatsu, H.; Bruijn, M. P.; Chervenak, J. A.; Gao, J. R.; Jackson, B. D.; Ridder, M.; More AuthorsAbstract Frequency-division multiplexing is the baseline read-out system for large arrays of superconducting transition-edge sensors (TES's) under development for the X-ray and infrared instruments like X-IFU (Athena) and SAFARI, respectively. In this multiplexing scheme, the sensors are ac-biased at different frequencies from 1 to 5 MHz and operate as amplitude modulators. Weak superconductivity is responsible for the complex TES resistive transition, experimentally explored in great detail so far, both with dc-and ac-biased read-out schemes. In this paper, we will review the current status of our understanding of the physics of the TES's and their interaction with the ac bias circuit. In particular, we will compare the behaviour of the TES nonlinear impedance, across the superconducting transition, for several detector families, namely: high-normal-resistance TiAu TES bolometers, low-normal-resistance MoAu TES microcalorimeters and high-normal-resistance TiAu TES microcalorimeters.

High aspect ratio transition edge sensors for x-ray spectrometry

“…The high frequency pixels are characterized by strongly fluctuation values of α and β , especially for low values of R/R n . The oscillations are caused by the weak-link effect 19,20 . The low frequency pixels are less affected by this problem.…”

“…Here k B is Boltzmann's constant and M 2 is the excess noise, given by the difference between the measured and predicted noise. This excess noise is typically explained by other noise sources, such as the weak-link effect described by the resistively shunted junction (RSJ) model 20,45 , the presence of phase-slip lines 46 , or ITFN 11,15,[47][48][49] . In this paper, we will not go into a detailed analysis of the origin of the excess noise, but instead use it as a guideline to find the optimal TES design.…”

Progress in the Development of Frequency-Domain Multiplexing for the X-ray Integral Field Unit on Board the Athena Mission

“…At the low bias frequency, for the first time, we have archived DC bias compatible performance under AC bias 13,14 . At higher frequency, there is a slight degradation which can be impacts of AC loss 15 , AC Josephson effect 16 and contributions from the room temperature electronics. Both performances are better than predictions from the integrated noise equivalent power (NEP).…”

Development of a Ti/Au TES Microcalorimeter Array as a Backup Sensor for the Athena/X-IFU Instrument

“…In the past few years, an extensive research collaboration on this issue has been made between NASA/Goddard and SRON. As outcomes, two types of frequency-dependent physical effects, namely AC losses and the Josephson effect, have been identified and theoretical analyses have shown that both effects can be mitigated by increasing the total TES normal resistance [4,5]. This is possible by decreasing the TES thickness however, it seems also important to have a thick TES film for a better thermal conductivity.…”