The Electronics

RAM2-M.jpgThe 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.

650 electronics boards are installed in AMS-02. All of them are constructed and installed in multiple copies. In the case of a failure of the primary board, the system will automatically switch to a secondary (or even tertiary) board.

The requirements for operating electronics in space are very challenging: it has to resist to vibrations, to operate in the vacuum, in the absence of gravity and in the presence of thermal cycles. Most important, it has to resist radiation. AMS-02 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.

The AMS boards do a lot of different things, from power supply to data acquisition (DAQ). The electronics can be sorted into three groups:

  • 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 all the AMS-02 electronics with power from the ISS photovoltaic arrays. The JMDC (Main DAQ Computer) sends commands and receives replies from all boards. Because the JMDC board is so important to the operation of AMS-02  there is a four copy redundancy!
  • Subsystems Electronics: most of the AMS electronic boards are dedicated to specific tasks. For example, the Tracker Thermal Control Electronics (TTCE) which is able to control the heaters and pumps of the Tracker Thermal Control system.
  • Electronics1.jpgDAQ Electronics: despite the different specific requirements of each subdetector, a unified approach has been adopted for the the 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, etc.). The next node in this tree, the JINF, receives data from up to 24 xDR. In the JINF, data from the xDRs is 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 while also monitoring the detector performance. The selected events are then buffered and sent out the HRDL (High Rate Dynamic Link) when they become available.