Filter Box

MCE Filter Board

The filter board is sealed in a faraday cage and connects to the cryostat MDM connectors using a drive shaft. Each analog signal from the cryostat is filtered using a 150pF capacitor connected between the signal and the chassis or cryostat wall. The MCE uses 5 identical filter boards that attach directly to the cryostat wall.

Notes

1k PCB capacitance

Typical Readout sig/ret capacitive load = 16pF +/- 2pF

Typical row_select sig/ret capacitive load = 23pF +/- 1pF

(both measured at 100Hz, 1kHz, 10kHz, and 100kHz using a Wayne Kerr Automatic LCR meter (4250)

Cryocable Impedance

30-50pF per meter (typically <2m)

265-Ohm, 190-Ohm, 110-Ohm (quoted from various experiments)

Bandwidth restriction caused by cable impedance in conjunction with the filter

Assuming 100pf/200-Ohm cable and 150pf filter, the cable has a pole at: 3.2MHz

[[ In our test cryostat next run we expect the wiring to have R~90 ohms (round trip) and C~180 pF between pairs, in case that informs the component choice.

Flight Cryostat: 48" + 45" test cable becomes 3m + 45" for fligth