Coulomb blockade thermometer: Tests and instrumentation

Coulomb blockade thermometry (CBT) provides a simple method for absolute th ermometry in every day laboratory use at cryogenic temperatures. CBT has be en found insensitive to even high magnetic fields. We review the principles and the operation of CBT and the fabrication of the sensors, and present n ew data on radiation hardness and stability of the sensors. We describe the instrumentation of CBT in detail. We have developed two signal conditionin g units for CBT measurements. One is a modified alternating current resista nce bridge, a versatile laboratory instrument operating with a PC computer, and the other one is a simple stand-alone instrument for direct temperatur e reading. Test results on their performance are also presented. Both proto types have a short-term reproducibility of 0.3% or better in temperature me asurement. (C) 1998 American Institute of Physics. [S0034-6748(98)03912-4].