 Submillimeter APEX Bolometer Camera Bolometer Development Group Millimeter & Submillimeter Astronomy Group Max-Planck-Institut für Radioastronomie (MPIfR)
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Welcome to the official SABOCA website SABOCA ( Submillimeter APEX Bolometer Camera) is a multi-beam bolometric receiver developed by the Max-Planck-Institut für Radioastronomie (MPIfR) of Bonn SABOCA is a superconducting (TES) bolometer camera installed on the APEX telescope for operation in the 350 micron atmospheric window Readout Scheme and Data
Acquisition
The TES bolometers are read out in a
time domain multiplexing scheme via four independent SQUID
amplifiers/multiplexers chains providing 10 channels each for a total
of 40 possible elements. The multiplexers and the associated
electronics have been designed and manufactured by IPHT.
 The four SQUID amplifiers are attached to the liquid helium cold plate and operated at the temperature of the pumped liquid helium (~1.6 K). The 40 SQUID multiplexers, divided in four groups of ten, are located at the four sides of the bolometer array. They are operated at the same temperature as the bolometers (~300 mK). In order to operate the SQUIDs in such a contaminated and unstable electromagnetic environment as the C-cabin of APEX, some magnetic shielding is required. In SABOCA this is achieved in two stages: a) on the outside, an envelope made of high magnetic permeability metal (called mu-metal) covers most of the cryostat; b) by superconducting shielding of the innermost parts, activated when the temperature goes below 1.2 K (critical temperature of aluminum). The tests have proven the effectiveness of the shielding and the reproducibility of the SQUIDs operation point: although the system was recycled several times inside the C-cabin, it was always possible to operate the SQUIDs with the same pre-defined optimal settings, by restoring them from a data file, making the system easy to operate. The backend software, running on the same backend computer used by LABOCA, is used to collect the bolometer signals from the de-multiplexers of SABOCA and provide the TCP data stream required by the APEX control software. With the use of the same bridge computer of LABOCA, real-time digital signal processing (Fourier filtering, downsampling) of the raw data is also possible, although not strictly required. |
| web: gsiringo (at) mpifr-bonn.mpg.de | last edit: G. Siringo, MPIfR - February 2009 |