Changes

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.  

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.  

Every bundle support (a.k.a. popsicle stick) supports a 5x6 array of 30 fibers. Each individual fiber is constructed from a 2.0 cm long section of BCF-20 SciFi thermally fused to 163.1 cm of BCF-98 lightguide. These fibers have a 2x2 mm² square transverse cross section. The angle of each bundle support with respect to the focal plane (&beta; angle) is selected to correspond to the average crossing angle for the electrons passing through these six columns of fibers. Therefore, for each bundle support there is a projection along this &beta; angle that the support can be located and still remain within the design specifications of the TAGM. Since the &beta; angle of the electrons only varies slightly over the entire bundle support's width, there is a fair amount of play with the exact location of the SciFi columns near the focal plane of the Tagger Magnet, provided they remain along the electron of interest's path. To put this in prospective consider a bundle placed at around 9.2 GeV (E_&gamma;). This 5x6 array of fibers will cover an energy range of 54 MeV and will see a change in &beta; angle of only 0.11^o from its first column of fiber to its last (6^<u>th</u> column).     

Every bundle support (a.k.a. popsicle stick) supports a 5x6 array of 30 fibers. Each individual fiber is constructed from a 2.0 cm long section of BCF-20 SciFi thermally fused to 163.1 cm of BCF-98 lightguide. These fibers have a 2 x 2 mm² square transverse profile. The angle of each bundle support with respect to the focal plane (&beta; angle) is selected to correspond to the average crossing angle for the electrons passing through these six columns of fibers. Therefore, for each bundle support there is a projection along this &beta; angle that the support can be located and still remain within the design specifications of the TAGM. Since the &beta; angle of the electrons only varies slightly over the entire bundle support's width, there is a fair amount of play with the exact location of the SciFi columns near the focal plane of the Tagger Magnet, provided they remain along the electron of interest's path. To put this in prospective consider a bundle placed at around 9.2 GeV (E_&gamma;). This 5x6 array of fibers will cover an energy range of 54 MeV and will see a change in &beta; angle of only 0.11^o from its first column of fiber to its last (6^<u>th</u> column).