The number of electronics channels in AMS-02 (~ 300,000 channels) is equivalent to all of the ISS electronics channels combined. This large amount of electronics is needed for the correct operation of AMS-02.
Why do we need Electronics?
650 Electronics boards do AMS-02 working. All the AMS electronic boards are constructed and installed in multiple copies. In the case of failure of the primary board the system will automatically switch to the use of a secondary (or event tertiary) board. The AMS boards do a lot of different things, from power supply to data acquisition (DAQ). Let’s explore a brief gallery.
Common Electronics: there are few basic boards in the system. One of the most important is the Power Distribution System (PDS), the board that feeds with the power coming from the ISS photovoltaic arrays all the AMS-02 electronics. The JMDC (Main DAQ Computer) sends commands and receives replies from all boards. In the case of the special importance of the JMDC board we have a four copy redundancy!
Subsystems Electronics: most of the AMS electronic boards are dedicated to specific tasks, such as the Cryogenic Avionic System (CAB), a board dedicated to the control of the cryogenic system, or the Tracker Thermal Control Electronics (TTCE) able to control heaters and pumps of the Tracker Thermal Control system.
DAQ Electronics: despite the specific requirements imposed by Physics are different for each sub-detector, an unified approach has been adopted for the their DAQ electronics. Analog signals from the detectors are digitized – typically through an Analog-to-Digtal Converter (ADC) – and compressed in Data Reduction boards (TDR for Tracker, RDR for RICH, EDR for ECAL, etcetera). The next node in this tree, the JINF, receives data from up to 24 xDR. In the JINF data from the xDRs are collated, buffered and sent to the top level JINJ boards. The JINJ collates, buffers and passes data to a JMDC. The JMDC receives the complete event and analyses it to ensure that it might contain interesting physics, monitoring also the detector performance. The selected events are then buffered and sent out the HRDL (High Rate Dynamic Link) when they become available.
How the Electronics is built?
The requirements for operating electronics in space are very challenging: it has to be resistant to vibrations, to operate in the vacuum, in the absence of gravity, in the presence of thermal cycles. Most important it has to be resistant to radiation. AMS uses special radiation-tolerant chips, developed for high-energy physics, which are ~ 10 times faster than typical spaceflight computers. This allows us to digitize 300,000 channels of data 2,000 times per second. All of these electronics boards are custom-designed for the AMS Collaboration. Redundancy is systematically implemented: there are at least two of every card, cable, and connector.