Current Sensing Noise Thermometry: A Fast Practical Solution to Low Temperature Measurement

Abstract

We describe the design and performance of a series of fast, precise current sensing noise thermometers. The thermometers have been fabricated with a range of resistances from 1.290 Ω down to 0.2 mΩ. This results in either a thermometer that has been optimised for speed, taking advantage of the improvements in superconducting quantum interference device (SQUID) noise and bandwidth, or a thermometer optimised for ultra-low temperature measurement, minimising the system noise temperature. With a single temperature calibration point, we show that noise thermometers can be used for accurate measurements over a wide range of temperatures below 4 K. Comparisons with a melting curve thermometer, a calibrated germanium thermometer and a pulsed platinum nuclear magnetic resonance thermometer are presented. For the 1.290 Ω resistance we measure a 1 % precision in just 100 ms, and have shown this to be independent of temperature.

Magnetic cooling for microkelvin nanoelectronics on a cryofree platform

“…b) dominik.zumbuhl@unibas.ch and extended hold time compared to the traditional wet system, due to liquid He transfers increasing the temperature of the entire system. First operative AND systems on cryogen-free platforms have been implemented using both PrNi 5 and Cu as nuclear refrigerant [9][10][11] . In contrast to the single nuclear stage experiment, the parallel network of NRs amends itself for nanoelectronics providing direct cooling of the electrons in each of the wires connected to the sample.…”

Progress in Cooling Nanoelectronic Devices to Ultra-Low Temperatures

“…Information about the current state of metrology in ultralow temperature thermometry can be found in [25]. More information about techniques that are particularly relevant to micro-/nanoelectronic devices at ultralow temperatures can be found, for example, in [26][27][28] for noise thermometry, [29][30][31][32] for Coulomb blockade thermometry and [33][34][35] for quantum dot-based thermometry. Almost all of the work discussed below makes use of one or more of these thermometry techniques.…”

Noise Thermometry for Ultralow Temperatures

“…The much higher sensitivity of dc-SQUIDs allowed one to open up the bandwidth and thus speed up the measurement process by several orders of magnitude. Following up this work about 15 years later, practical current noise thermometers were developed and characterized over a wide range of temperatures [35][36][37][38][39][40][41].…”

“…With a one-point calibration, the noise thermometer showed excellent agreement with the 3 He melting curve thermometer in relative primary mode in the entire range with a standard deviation of below 2% after integrating for 160 s. However, a small heat leak of a few fW led to a thermal decoupling of the electrons in the noise generating 0.34 mΩ resistor below 1 mK and prevented the use of this thermometer in relative primary mode in this range [37]. An improved version of this type of noise thermometer has been used to demonstrate the applicability in relative primary mode down to about 0.3 mK before similar decoupling effects occur [38]. Figure 4a shows the power spectral density of current noise ⟨I 2 N ⟩ at 500 mK as a function of frequency for three current-sensing noise thermometers with noise-generating copper foils having different resistances.…”