Readout Electronics Update: New Readout Cards for noise and power. New Bias Cards for power. New Power Supply for noise. All firmware can be re- programmed over the fibre. Command and Control described by Don Wiebe

A very simple readout system: Squids provide sensitive, very fast current amplification. Many bolometers can be read out with one squid, either one after the other (Time Domain Multiplexing) or by running the detectors at separate AC frequencies (Frequency Domain)

The voltage across a squid is periodic in the applied flux. Operate where gain is high

We apply a “feedback” flux at each squid to keep it operating at the peak slope of its V-  curve.

Time-Domain Multiplexing: Leave the detectors running, and turn on only one 1st stage squid at a time. A single Squid-2 can read 40 bolometers. (Depends on L/R.) NIST makes these TD Multiplexors.

Simplified time-domain multiplexing: All the first stage squids in a given row are biased on at one time. Signals are read out in columns.

Each box of electronics contains: One Clock Card--Receives commands, packages the data, can reprogram other cards One Address card--Selects row 0 to 40 of the multiplexor. ( The pixels in row 40 are “dark”.) Readout Cards-- Each reads eight columns, calculates and applies feedback signals, collects and filters data for an 8x41 segment of the array. Bias Cards--Control squids in amplifier chain. An Address card in a Bias slot has allowed fast Squid-2 switching. One Power Supply card Boxes bolt directly to the cryostat wall. Mark Halpern, UBC Physics and Astronomy