Special triggers

Along with the main data stream we will store various samples of uncompressed raw data:

• Zero Bias: At a low duty cycle we will simply output a small section the the raw data to tape. This will be done with no bias at all: no muon has to be in the TPC etc. This data sample will be very important in proving that we did not throw away important events or bias our data by our online compression algorithm.
• Impurity Scan: The TPC region around the end of each muon track will be scanned for secondary high threshold hits. Such events are indicative of muon capture on an impurity atom. These events will be rare but very important is calibrating the final level of impurities in our gas. These events will be read out raw.
• $\mu d$ Diffusion Events: To calibrate the exact amount of residual deuterium in the gas we will track a large fraction of $\mu d$ diffusion candidates. If the external tracking points far from a unique muon track, the TPC region near the end of the track will be scanned for evidence of an elctron track. If a track is not found, the region will be recorded raw so that the offline program can search for the track of the diffused $\mu d$. These are our cleanest sample of deuterium related events.