Yasushi Murayama

Comparison of a Multichip 10-V Programmable Josephson Voltage Standard System With a Superconductor–Insulator–Superconductor-Based Conventional System

We developed a 10-V dc programmable Josephson voltage standard (PJVS) using a multichip technique. The PJVS was based on NbN/TiNx/NbN junctions and operated using a 10-K compact cryocooler. We carried out an indirect comparison with a superconductor-insulator-superconductor-based conventional Josephson voltage standard (JVS) by measuring the voltage of a 10-V zener diode reference standard. The combined standard uncertainty of the comparison was u c = 0.03 muV(k = 1), and the relative combined standard uncertainty was 3 times10-9.

Measurement System for Quantum Hall Effect Utilizing a Josephson Potentiometer

In order to improve the measurement accuracy of the quantum Hail effect, a new method has been developed utilizing a Josephson potentiometer and a Superconducting Quantum Interference Device (SQUID) galvanometer. A relative uncertainty of a few parts in 108 can be realized for the measurement of the ratio of the quantized Hall resistance to a reference resistor using this method.

Ten-volt Josephson voltage standard at the ETL

A voltage standard system using a 10 V Josephson junction array has been developed. The uncertainty is 0.6/spl times/10/sup -8/ for measurement of the 10 V output of a Zener diode reference standard. A comparison of the 10 V array system with the conventional 10 V measurement system composed of a 1 V array and a voltage divider was performed through measurements of a 10 V output of a Zener. The result agreed within the uncertainty (2/spl times/10/sup -8/) of the comparison. The 10 V output voltages of a Zener reference standard are measured consecutively by the 10 V array system.

An improved Josephson potentiometer system for the measurement of the quantum Hall effect

Several improvements have been made on a Josephson potentiometer and superconducting quantum interference device (SQUID) galvanometer system previously reported. Results of the measurement of the quantized Hall resistance obtained by the use of this system are in agreement with those obtained by means of a conventional potentiometer system to 0.02 ± 0.08 ppm for silicon-MOSFET samples. A comparison of the Hall resistance between two different quantized values corresponding to h/4e2 and h/8e2, for a sample, has been made without an uncertainty associated with the linearity of voltage-ratio measurements. A discussion is presented in relation to completeness of the quantization.

Ten-volt Josephson junction array

An array of 20144 Josephson junctions divided into four strip line branches has been developed and tested. The array generates quantized voltages up to about 14 V under millimeter-wave irradiation of 90 mW at 92.5 GHz, and will be used in a 10-V voltage standard. >

Automated voltage divider to calibrate a 10-V output of Zener voltage standard

The authors present a voltage divider developed to calibrate the 10-V output of a Zener-diode voltage standard with reference to a 1-V Josephson array voltage standard. The ratio of the divider can be automatically self-calibrated by a digital voltmeter and a switching system controlled by a computer. The principle used for ratio calibration of the voltage divider is discussed. The configuration used for measurement of the divider ratio and the configuration used for calibration of the 10-V output of the Zener standard are described. The operation of the system is also described. >

Single-Chip 10-V Programmable Josephson Voltage Standard System Based on a Refrigerator and Its Precision Evaluation

We precisely evaluated a single-chip 10-V programmable Josephson voltage standard (PJVS) system based on a closed-cycle refrigerator by directly comparing it with a conventional Josephson voltage standard system. The PJVS chip fabricated using NbN/TiNx/NbN junction technology was used. The result of the measurement showed a good agreement with a combined standard uncertainty of 3.1 parts in 1010 at 10 V.

A direct comparison of a 10 V Josephson voltage standard between a refrigerator-based multi-chip programmable system and a conventional system

A multi-chip 10 V programmable Josephson voltage standard (PJVS) system was demonstrated using a closed-cycle refrigerator. We precisely measured the PJVS by a direct comparison measurement with a conventional Josephson voltage standard. The result agreed within a combined standard uncertainty of 3.9 × 10−10 at 10 V.

Automatic Measuring System for a Control of Standard Cells

The automatic measuring system developed in the Electrotechnical Laboratory to monitor standard cells requiring a lot of measurements is described. It is composed of a scanner, an integrating-type digital voltmeter, a programmer or minicomputer, etc., and carries out the data acquisition and processing for a maximum of 200 cells. The difference in EMF of two cells is measured precisely. To reduce the effect of the induced EMF in the scanner, a delay unit is provided, and procedures minimizing errors and evaluating random errors have been adopted. In the on-line version of system, a great part of the data processing is done during the delay and integrating time of digital voltmeter. Applying this system to the measurement of standard cells, a precision of the order of 0.1 ?V has been obtained.

A precise null-balancing technique (PNB) for the 10 V Josephson junction array voltage standard system

A precise null-balancing technique, which we call the PNB technique, has been developed for the 10 V Josephson-junction-array voltage standard system (10 V JJAVS) in order to improve the accuracy in null detection. Precision is achieved by (1) precisely capturing the desired Josephson step within /spl plusmn/3 step by using a newly developed mercury reed-relay switch, (2) adjusting the millimeter-wave frequency to attain strict null-balancing, and (3) using a stable chopper-type of digital voltmeter (DVM) as a null detector. This PNB technique was successfully applied to a 10 V JJAVS attaining a total uncertainty of 6/spl times/10/sup -9/ and reducing the calibration time to 20 min to 30 min.