Joseph R. Kinard

Performance of multilayer thin-film multijunction thermal converters

New multilayer, thin-film multijunction thermal converters (MJTCs) suitable as high performance ac-dc transfer standards have been fabricated and studied at NIST. This paper describes their thermal and physical features and the materials chosen to improve performance. Performance data are given over a wide range of frequencies and conditions. >

AC-DC difference relationships for current shunt and thermal converter combinations

The relationship between the overall AC-DC difference of a thermal converter and current shunt combination and the characteristics of the separate thermal converter and current shunt is described. Predicted and measured results are given for shunts used with different thermal converters. The disagreement is generally small compared to the uncertainty of AC current measurements at the individual frequencies. >

Thermal transfer measurements at microwatt power levels

This paper presents the design, fabrication and preliminary results for a thermal transfer standard operating at a power level of 20 /spl mu/W, or less, and at temperatures below 10 K. The new converter employs a superconducting-resistive-transition edge thermometer.

Integrated thin-film micropotentiometers

Integrated micropotentiometers, new devices fabricated with thin-film technology and the micromachining of silicon, have been developed for the accurate determination of ac voltage from 1 to 200 mV at frequencies from audio to 1 MHz and with the potential for higher frequencies. >

Evaluation of coaxial single range thermal voltage converters with multijunction thin-film thermoelements

The NIST and SNL are developing new thin-film multifunction thermal converters (MJTC) for use as standards of AC-DC difference. Elements of the fabrication process allow control of various features of the device affecting the optimal configuration (e.g. thermal time constant, heater resistance, etc...). A negative AC-DC transfer difference, caused by a capacitive coupling of AC signal to the silicon obelisk, is observed in devices with a silicon obelisk at high-frequency. A circuit model illustrates the dependence of this difference on the substrate resistivity. Devices that are assembled in a coaxially mounted single-range thermal voltage converter configuration are discussed.

Multijunction thermal converters by commerical CMOS fabrication

New multijunction thermal converters (MJTCs) fabricated in a commerical CMOS foundry are described. The MJTC is a cantilever structure with a suspended, resistance heating element and thermocouple hot junctions located near the heater on the cantilever. The pit etched below is 150 /spl times/ 150 /spl mu/m in size. The heater structure is composed of a polysilicon resistor and the thermocouples are made of aluminum-polysilicon. The results of measurements of their AC-DC transfer characteristics are given.<<ETX>>

Hybrid construction of multijunction thermal converters

Multijunction thermal converters designed for frequencies ranging from audio up to tens of megahertz and for heater currents from a few milliamperes up to hundreds of milliamperes, using thin-film and thick-film technologies, are described. Prototypes with various test features are reported. Different thermocouple geometries and guard couples have been included to investigate the heater temperature distribution and to study ways to optimize other characteristics. Different metals are also being investigated for use as the heater and thermocouples. The construction involves unsupported, dielectric membranes. Packages have been designed and fabricated to provide long-term stability, small distributed capacitance and inductance, and minimum skill effect through the use of all nonmagnetic materials.<<ETX>>

Improved vacuum thermocouples

Prior construction of single junction vacuum thermal convertors (SJTCs) did not consistently produce units with AC-DC differences of a few ppm or less. Four improvement modes have been introduced. (1) Elimination of flaming during the making of the mounting bead. (2) Changing of the feed-through posts from Dumet to platinum-iridium. (3) Decrease of the Thomson coefficient by changing from nickel-chromium to Evanohm heater wire. (4) Lowering of the temperature gradient along the heater wire in the vicinity of the thermocouple. SJTCs can now be constructed with AC-DC differences of less than 0.3 ppm at a high yield.<<ETX>>

Improved high-current thin-film multijunction thermal converters

We report on the fabrication of new thin-film multijunction thermal converters suitable for the measurement of current and new, simpler multiconverter modules that are much easier to manufacture than previous multiconverter modules.

A high-temperature superconducting transmission line for cryogenic electrical metrology applications

This paper describes the design, realization, and testing of a high-temperature superconducting (HTS) transmission line structure for delivering calibrated dc and ac signals to a cryogenic test platform. The inclusion of the HTS transmission line in the signal path reduces parasitic wiring resistance, maintains thermal isolation within the cryostat, and transmits dc through audio frequency signals with minimal loss and degradation.