MCE

MCE described here borrows heavily from the designs used at NIST. Changes have been made to upgrade components, achieve higher integration, and match to the specific SCUBA-2 configuration.

In basic operation, one box of the MCE controls the SQUID amplifiers and multiplexer, and reads signals from one 32×41 pixel sub-array. The system hardware is completely modular at the sub-array level. Each sub-array is connected via woven cryogenic cables to a single box of MCE, mounted directly on the cryostat wall through 5 MDM connectors. Each box of the MCE is in turn connected by an optical fibre to a single data-acquisition PC running real-time Linux and data-acquisition software (DAS) developed by SCUBA-2 team at UK Astronomy Technology Centre.

Each MCE consists of hybrid analog/digital hardware and firmware developed for Altera Stratix FPGAs. Every MCE has 10 cards: 4 readout cards each of which reads 8 output-columns through 14-bit 50MHz ADCs; 1 address card to multiplex the first-stage SQUIDs biases at around 20kHz; 1 clock card to interpret commands and to synchronize all the cards using a 25MHz clock; 3 bias cards to control the SQUID series-array feedback, the second-stage SQUID bias and feedback as well as the bolometer bias and heater; and 1 power-supply card. During detector setup, MCE is used to calculate the optimal operating points for the bolometers and the SQUID amplifiers by measuring their characteristics using open and closed feedback loops. During observation, MCE uses a running PID-calculation to determine the first-stage SQUID feedback necessary to keep the whole amplification chain in a linear regime.

In conjunction with the MCEs, a Sync Box supplies data-valid pulses with serial numbers to all MCEs and to the telescope pointing system. This allows synchronization between the data acquisition, the pointing system, and the telescope housekeeping.

Collaborations (in chronological order)

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