π Microwave Filter | Thermalizer

Designed for mili-Kelvin and sub-mili-Kelvin experiments

Microwave filtering and thermalization of signal wires are two critical ingredients in setting up a sensitive low-temperature experiment, such as quantum transport measurements. BASPI offers compact cryogenic microwave filter-thermalizers (MFT) that unite unmatched thermalization of the wires with ultra-strong microwave attenuation. The superior performance of the MFT was proven in an experiment that cooled a Coulomb blockade thermometer down to to 7.5 mK with the dilution fridge temperature at 5 mK (ref: Scheller et al. APL 2014).


Two MFT options are available: The standard MFT and the πMFT. The standard MFT consists of a copper wire embedded into a highly conductive silver matrix to ensure optimal thermalization. The π-MFT is identical to the standard MFT, but equipped with an additional pair of discoidal capacitors, resulting in an improved microwave suppression.

Customized designs are possible, e.g. packing several filters in a compact box or user-defined connector or wire types. 

This graph shows typical room temperature attenuation spectra of an MFT (red) and a πMFT (blue). The measurements are performed with a signal analyzer (1 kHz – 10 MHz) and a vector network analyzer (10 MHz – 40 GHz). Black triangles indicated the noise floor, measured with an open connection. Operation at 4.2K may shift the attenuation profile towards slightly higher frequencies.

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