Onboard electronics


AMS has over 600 separate computers on it. Some are little computers - a small, not-very-autonomous one to watch over the gas system, for example. Some are big computers - like the master computer which actually collects the particle data. One of the special challenges of AMS's electronics is due to the high levels of radiation in space; AMS uses special radiation-tolerant chips, developed for high energy physics, which are ~10 times as fast as typical spaceflight computers. This allows us to digitize 300,000 channels of data some 2000 times per second. All of these electronics are custom-designed just for the collaboration.

All of our electronics cards are redundant. There are at least two of every card, cable, and connector.

By way of illustration, let's look at some particular electronics items.

  • Cryomagnet Avionics Box, which has the high-power components needed to charge and discharge the magnet. This is the only AMS system that carries a "UPS" (Uninterruptible Power Supply) to keep its monitors awake even if the power is turned off.
  • Universal Slow Controls Module, a set of versatile little modules that handle "housekeeping" for all of the detectors (turning things on and off, monitoring voltages and temperatures, etc.)
  • The Main DAQ computer processes all of AMS's data, does preliminary analysis, decides which events to keep, and sends the data off to ISS. We cannot take data if the DAQ computer breaks, so we are launching four redundant copies.
  • The Power Distribution Box manages the power supplies for all of AMS's components. It has to convert 2,000 watts of power from 128V DC (used on the Station) to 28 V DC, which is needed by the rest of AMS. DC-DC conversion is not as easy as AC-AC or AC-DC conversion, yet we need the PDB to convert with better than 95% efficiency, and be as light as possible.
  • A circuit board called the "UFE" (Ubergangstrahlung Front End) amplifies the analog pulses from 64 tubes of the TRD; measures and digitizes the size of the pulses; and sends the data to the UDR (Ubergangstrahlung Data Reduction). The UDR filters and compresses the digital data and reports it (via an intermediate board) to the main computers. It takes 82 UFE boards to read the entire TRD.
  • A similar chain to the TRD - front-end board, data reduction board, main computer - reads out each of the detectors.
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    Technical details

  • Total power: ~2000 W
  • Total weight: ~450 kg
  • Number of cards: 532
  • Electronics coordinator: Dr. Mike Capell, MIT/CERN
  • Electronics summary lower ram crate upper ram crates Lower wake crates upper wake cratees Cryomagnet avionics box