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Line 17: + + − The tagger microscope (TAGM) consists of six major components: upper enclosure, lower enclosure, optical fibers, electronics, shielding, and darkening shroud. As seen from the CAD image above, Figure 1, the lower enclosure houses the microscope's electronics, while the upper enclosure contains the optical fiber bundle supports (a.k.a. popsicle sticks). The bundle supports are used to align the scintillating fiber (SciFi) longitudinal axis to the incoming electron's path angle as it passes through the tagger magnet's focal plane. The designed angular tolerance, e.g. fiber to electron allowable angular error, is < 0.5<sup>o</sup>. MC simulations were performed to test the effect of various amounts of misalignment between the electron angle and the SciFi axis. Figure 4 shows a plot of one of these simulations with the solid line showing the scintillation response of the central fiber, while the dashed lines are the response for the adjacent fibers. A factor of three separation between adjacent signal amplitudes is achievable when alignment is < 3<sup>o</sup>. In order to achieve optimal alignment, similar to < 0.2<sup>o</sup> that was seen in bench tests, the SciFi end of the optical fibers are affixed to bundle supports (Figure 5) in the upper enclosure, with the light guide potion of the fiber extending down to silicon photomultipliers (SiPMs) located on preamplifier boards (Figure 6) in the lower enclosure. − [[Image:Mounting_Test_Popsicle_Stick.jpg|right|thumb|300px|Figure 5: Picture taken during testing phase of a bundle support with mounted fibers. Note that the bundle support does not have its mounting rods installed. These rods are used to secure the bundle support to the parallel railing system located in the upper enclosure.]] − [[Image:SiPM_alignment.png|right|thumb|300px|Figure 6: Image of the preamplifier board and open chimney (light guide holder) before fiber installation. The chimney aligns the 2mm<sup>2</sup> lightguide end to the center of the 3mm<sup>2</sup> active area of the SiPM with only a 0.5mm air gap between the two.]]+ + + + + + +
Moving the Tagger Microscope (view source)
Revision as of 02:46, 25 March 2021
, 02:46, 25 March 2021→Moving the Tagger Microscope Along the Focal Plane
TAGM_Back.jpg|Figure 3: TAGM during reassembly just prior to installation in the Tagger Hall. The side of the TAGM seen here will face away from the Tagger Magnet when installed.
TAGM_Back.jpg|Figure 3: TAGM during reassembly just prior to installation in the Tagger Hall. The side of the TAGM seen here will face away from the Tagger Magnet when installed.
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[[Image:e-angle_fiber-amp.png|right|thumb|300px|Figure 4: Result of a MC simulation performed to predict the response of adjacent scintillating fiber columns due to fiber axis misalignment with respect to a post-bremsstrahlung electron's path. The solid line represents the response seen by the central fiber, while the dashed lines are the adjacent fibers' response.]]
[[Image:e-angle_fiber-amp.png|right|thumb|300px|Figure 4: Result of a MC simulation performed to predict the response of adjacent scintillating fiber columns due to fiber axis misalignment with respect to a post-bremsstrahlung electron's path. The solid line represents the response seen by the central fiber, while the dashed lines are the adjacent fibers' response.]]
The tagger microscope (TAGM) consists of six major components: upper enclosure, lower enclosure, optical fibers, electronics, shielding, and darkening shroud. As seen from the CAD image above, Figure 1, the lower enclosure houses the microscope's electronics, while the upper enclosure contains the optical fiber bundle supports (a.k.a. popsicle sticks). The bundle supports are used to align the scintillating fiber (SciFi) longitudinal axis to the incoming electron's path angle as it passes through the tagger magnet's focal plane. The designed angular tolerance, e.g. fiber to electron allowable angular error, is < 0.5<sup>o</sup>. MC simulations were performed to test the effect of various amounts of misalignment between the electron angle and the SciFi axis. Figure 4 shows a plot of one of these simulations with the solid line showing the scintillation response of the central fiber, while the dashed lines are the response for the adjacent fibers. A factor of three separation between adjacent signal amplitudes is achievable when alignment is < 3<sup>o</sup>. In order to achieve optimal alignment, similar to < 0.2<sup>o</sup> that was seen in bench tests, the SciFi end of the optical fibers are affixed to bundle supports (Figure 5) in the upper enclosure, with the light guide potion of the fiber extending down to silicon photomultipliers (SiPMs) located on preamplifier boards (Figure 6) in the lower enclosure.
<gallery caption="The two ends of the optical fibers" widths="300px" heights="300px" class="center">
Mounting_Test_Popsicle_Stick.jpg|Figure 5: Picture taken during testing phase of a bundle support with mounted fibers. Note that the bundle support does not have its mounting rods installed. These rods are used to secure the bundle support to the parallel railing system located in the upper enclosure.
SiPM_alignment.png|Figure 6: Image of the preamplifier board and open chimney (light guide holder) before fiber installation. The chimney aligns the 2mm<sup>2</sup> lightguide end to the center of the 3mm<sup>2</sup> active area of the SiPM with only a 0.5mm air gap between the two.
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Moving the TAGM to a new energy range not only involves the physical relocation of the microscope and its shielding along the tagger magnet's focal plane, but also requires internal realignment of the fiber, which is the subject of this page. The realignment of the scintillating fibers' longitudinal axes requires all 17 bundle supports to have new, individual crossing angles (&beta angle) with respect to the focal plane. These angles are derived from a table generated based on a TOSCA map of the post-bremsstrahlung crossing angles as they pass through the magnet's focal plane. Since the crossing angle changes with energy (e.g. displacement along the focal plane) each bundle support will have a slight "kick" or "tow" from the adjacent bundle support. The tow is typically on the order of 0.1<sup>o</sup>. an adjustment of the parallel railing system
==Coordinate System==
==Coordinate System==