A new series array of 1440 Josephson tunnel junctions has been developed and tested as a reference voltage standard. It yields microwave induced quantized voltage steps up to 1.3 V. The steps are usually stable for more than 5 h with a microwave driving frequency of either 70 or 90 GHz. A high-resolution comparison of a constant voltage step at the 1-V level with the electromotive force of a saturated Weston cell is described. The comparison shows that the step voltage is constant to within ±1 nV over the full step width.
1000 Ω and 1290.64 Ω coaxial resistors with calculable frequency dependence have been realized at PTB to be used in quantum Hall effect-based impedance measurements. In contradistinction to common designs of coaxial resistors, the design described in this paper makes it possible to remove the resistive element from the shield and to handle it without cutting the outer cylindrical shield of the resistor. Emphasis has been given to manufacturing technology and suppressing unwanted sources of frequency dependence. The adjustment accuracy is better than 10 µΩ Ω−1.
The transverse mode size of the X-ray free-electron laser is derived using information on transverse coherence. The derived formula for the mode size agrees well with the simulation result.
An integrated microwave circuit with a series array of 1440 Josephson tunnel junctions has been developed. This array provides microwave-induced quantized reference voltages between 0.1 and 1.3 V. A comparison of an array voltage with that of a Weston cell shows that a reproducibility of a few parts in 10" can be reached for a 1V reference voltage at room temperature. No current dependence of a quantized array voltage has been found within an uncertainty of k 7 x V from a comparison of two array voltages.
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