Arduino-Based Novel Hardware Design for Liquid Helium Level Measurement

Liquid helium (LHe) is used as a cryogen in a variety of applications involving superconductivity and is routinely monitored for conducting low-temperature experiments. Thermoacoustic oscillations, which are inevitably present inside closed LHe containers, are utilized for level detection by sensing the vibrations at the warm end of a thin capillary tube inserted into the Dewar. The position of the capillary tube at which a sudden change occurs in these oscillations is manually sensed to identify the liquid level. The present work proposes a novel hardware design to identify the thermoacoustic oscillations in a reliable way using an accelerometer driven by an Arduino microcontroller. Further, an automated approach has been devised to quantify the rate of change of these helium oscillations to measure the LHe level. The proposed method has been tested during several trials on a 120 L and 100 L capacity Dewar using the proposed hardware, and the mean error in measuring the LHe level was calculated to be less than 1 cm in comparison with the gold standard niobium-titanium level sensor. The results encourage the use of the proposed method to evolve as a cost-effective alternative to the widely used superconducting level sensors in measuring LHe level.

Present status of the fine-structure frequencies of the 23P helium level

A new measurement of the fine-structure frequencies of the 23 P level in 4He is presented. The result for the largest interval 23 P0–23 P1 is 29 616 952.7(1.0) kHz, and 2 291 167.7(11.0) kHz for the smallest one, 23 P1–23 P2. Taking into account this new result, an agreement among different experiments at the 1 kHz level is found. Implications of this situation for the determination of the fine-structure constant α are discussed. PACS Nos.: 31.15.Pf, 31.30.Jv, and 32.10.Hq

RSFQ TECHNOLOGY: PHYSICS AND DEVICES

Rapid Single-Flux-Quantum (RSFQ) logic, based on the representation of digital bits by single quanta of magnetic flux in superconducting loops, may combine several-hundred-GHz speed with extremely low power dissipation (close to 10-18 Joule/bit) and very simple fabrication technology. The drawbacks of this technology include the necessity of deep (liquid-helium-level) cooling of RSFQ circuits and the rudimentary level of the currently available fabrication and testing facilities. The objective of this paper is to review RSFQ device physics and also discuss in brief the prospects of future development of this technology in the light of the tradeoff between its advantages and handicaps.