The TWIST Data Acquisition System at Triumf

The TRIUMF Weak Interaction Symmetry Test (TWIST) is an experiment to measure precisely the Michel parameters describing the energy and angular dependence of positrons emitted from the decay of polarized positive muons. The detector consists of a 2 Tesla superconducting solenoid containing 56 planar chambers for high precision tracking of the positrons through readout of some 4200 multihit TDC channels. Being a high precision, high statistics experiment, control and monitoring of the beam and ambient conditions had to be closely integrated into the data acquisition system. A successful data run in 2002 produced more than 6 Giga events expected to yield some first physics results. This paper will describe the details and performance of the DAQ system including slow controls and online monitoring techniques.