Changes

==Tagger Microscope Placement in the Tagger Hall==

==Tagger Microscope Placement in the Tagger Hall==

When discussing the location of the TAGM within the Tagger Hall it is often easiest to reference the starting point of the energy spectrum being tagged. For example, if the TAGM is said to be placed at 9.2 GeV this would indicate that the location of the most upstream column of fibers, with respect to the beamline, is such that a post-bremsstrahlung electron associated with a 9.2 GeV emitted photon will pass through the longitudinal axis of this column of SciFi's. This column is referenced as column #1 in figure 1 below. As the column numbers increase the electrons' energy increases, and as such the energy of the associated photon being tagged decreases. The β angle of each bundle support, which as you recall holds an array of 5x6 fibers with a 2mm² cross section, is selected to correspond to the average crossing angle for the electrons passing through these six columns. Therefore, for each bundle support there is a projection along this β angle that the support can be located. Since the crossing angle of the electrons only varies slightly over the bundle support width, there is a fair amount of play with the placement of the SciFi columns near the focal plane of the Tagger Magnet. To put this in prospective consider a bundle placed at 9.2 GeV. This 5x6 array of fibers will cover an energy range of 54 MeV and will see a change in β angle of only 0.11^o.     

When discussing the location of the Tagger Microscope (TAGM) within the Tagger Hall it is often easiest to reference the starting point of the energy spectrum being tagged. For example, if the TAGM is said to be placed at 9.2 GeV this would indicate that the location of the most upstream column of fibers, with respect to the beamline, is such that a post-bremsstrahlung electron associated with a 9.2 GeV emitted photon will pass through the longitudinal axis of this column of scintillating fibers (SciFi). This column is referenced as column #1 in figure 1 below. As the column numbers increase the electrons' energy increases, and as such the energy of the associated photon being tagged decreases. The β angle of each bundle support, which as you recall holds an array of 5x6 fibers with a 2mm² cross section, is selected to correspond to the average crossing angle for the electrons passing through these six columns. Therefore, for each bundle support there is a projection along this β angle that the support can be located. Since the crossing angle of the electrons only varies slightly over the bundle support width, there is a fair amount of play with the placement of the SciFi columns near the focal plane of the Tagger Magnet. To put this in prospective consider a bundle placed at 9.2 GeV. This 5x6 array of fibers will cover an energy range of 54 MeV and will see a change in β angle of only 0.11^o.