Low-noise electronics
One of the main reasons to operate at low temperatures is the lower thermal noise power, proportional to the physical temperature, that allows to measure fainter signals. This is crucial when ultimate sensitivity is needed, like for astronomical detectors, or when energy-efficiency is of concern. Indeed in this case voltages and currents must be lowered, which requires specific electronics. In particular low-noise amplifiers are required to sense signals at room temperature; low noise signal sources are also necessary to operate circuits in the quietest way.
At lower temperatures, the circuits themselves can operate with lower power consumption and deliver signals with less noise, but often at the cost of different electrical parameters that change their properties, which implies the need to re-qualify and re-optimize the circuits. These requalification and re-optimization tasks at cryogenic temperature are a potential application of the platform, especially for semiconductor components. Optimized cryo-electronic circuits or devices require precise characterization measurements at low temperature which are time consuming due to thermal cycling and iterations between design and fabrication on the one hand, and measurements on the other.
For these purposes our turnkey Cryo-P platform allows to perform fast tests in a convenient way, with the possibility of parametrized measurements based on the large number of devices measured simultaneously, in a single cooling of the platform.
Cryo-P comes with 8-channel modules, like the one of the right picture dedicated to low-noise amplifiers. Six such modules are installed for the standard version, corresponding to 96 bias wires. More modules can be added for more complex circuits requiring several hundred of wires. The only limit is fixed by the power consumed by the circuits under test that must stay below about 100 mW if measurements must be done down to 4K. A much higher power of several watts is possible for circuits under tests if measurements are only needed at higher temperature like from 20K to 80K.
Cryo-P includes :
- modules of 8 low-noise amplifiers with noise of about 3nV/√Hz with a choice of 2 different bandwidths of 100 kHz (Neon module) or 500 kHz (Argon module). Gain is 1, 10, 100 or 1000 for Neon amplifiers and 100, 1000 or 10000 for Argon amplifiers, controlled digitally ;
- modules of 8 low-noise unidirectional (Krypton module) or bidirectional (Xeon module) current sources with current noise below 1 nA/√Hz @ 1 kHz and gains of 0.1, 1, 10 and 100 nA/volt, controlled digitally ;
- an 8-channel temperature module to sense 8 different places simultaneously in the cryo-cooled volume, either at the 4K stage or on the 20-50 K stage.
The standard total number of modules is 8 for a platform with 96 wires, excluding the temperature sensor module. Modules can be any mix of the Neon, Argon, Krypton or Neon modules , depending on needs.
All these modules are purely analogue for better noise performance and can be run on rechargeable batteries or through an integrated power delivery system by a computer-controlled control and acquisition system.
An example of interference-diffraction figure of a SQUID measured with a similar electronics is shown below. It allows to observe the quality of the measurements made with such a low-noise electronics.
