A study of the performance of the LED-based monitoring system for Fermi National Accelerator Laboratory experiment E683's main calorimeter detector
In the experiment E683 at Fermi National Accelerator Lab (FNAL) in Batavia, Illinois, a modular, high-energy sampling calorimeter was the basis of the detector system. In order to monitor each of the 528 modules of the calorimeter, an embedded LED was flashed directly into each of the 528 PMT tubes (which normally pick up the light from the sampling modules of the calorimeter) and their responses were recorded. The purpose of this investigation was to observe, study, and possibly make corrections for any fluctuations in the PMT response to the LED signals. Also, as a check, the PMT data was analyzed to see if any LED fluctuations were correlated with any fluctuations in the calorimeter module data coming from particles produced when targets were exposed to accelerator beam particles. These studies were done using a VAXstation model 4000/60, and the database and graphics components (called 'N-tuples' and `PAW' respectively) of a High Energy Physics math package called 'CERNLIB'. By putting the analyzed data into n-tuple files, many different modelings of the same data could be checked more efficiently. The study found that the LED system was useful for detecting and correcting for signal degradation due to calamp failure and these corrections were put in the E683 analysis package. It was also found that long term LED response signal fluctuations were not completely explained, but that there was no correlation with beam induced calorimeter response signal fluctuations.