  The goal of the ASACUSA (Atomic Spectroscopy And Collisions Using Slow
Antiprotons) CUSP experiment at CERN's Antiproton Decelerator is to measure the
ground state hyperfine splitting of antihydrogen in order to test whether CPT
invariance is broken.
  The ASACUSA hodoscope is a detector consisting of two layers of 32 plastic
scintillator bars individually read out by two serially connected silicon photo
multipliers (SiPMs) on each end. Two additional layers for position resolution
along the beam axis were scintillator fibres, which will now be replaced by
scintillating tiles placed onto the existing bars and also read out by SiPMs.
If the antiproton of antihydrogen annihilates in the center of the hodoscope,
particles (mostly pions) are produced and travel through the various layers of
the detector and produce signals.
  The hodoscope was successfully used during the last data taking period at
CERN. The necessary time resolution to discriminate between particles
travelling through the detector from outside and particles produced in the
center of the detector was achieved by the use of waveform digitisers and
software constant fraction discrimination. The disadvantage of this readout
scheme was the slow readout speed, which was improved by two orders of
magnitude. This was done by omitting the digitisers and replacing them with
TDCs reading out the digital time-over-threshold (ToT) signal using leading
edge discrimination.
