A simple dynamic parallel railing system was devised to allow flexibility for the electron crossing angle. In the range of useful photon energies (3-12 GeV) the crossing angle (measured from the focal plane) is calculated to change from 8 to 60 degrees. The adjacent figure illustrates a set of "rails" kept apart by beams parallel to electron trajectory. As shown, this allows for properly positioned mounting sites for both ends of the fiber modules. Additionally, in the high energy photon range (where electrons have low energy and bend significantly) the errors accumulating from keeping the fibers parallel are no longer insignificant. The right-hand side of the parallelogram shown is actually equipped with a slot to allow the lower rail to rotate inward and deviating from this parallel arrangement. It can be shown that the natural alignment of the fiber modules contains allows a small angular shift from one fiber module to the next, satisfying to the necessary extent the alignment with the electron trajectories. | A simple dynamic parallel railing system was devised to allow flexibility for the electron crossing angle. In the range of useful photon energies (3-12 GeV) the crossing angle (measured from the focal plane) is calculated to change from 8 to 60 degrees. The adjacent figure illustrates a set of "rails" kept apart by beams parallel to electron trajectory. As shown, this allows for properly positioned mounting sites for both ends of the fiber modules. Additionally, in the high energy photon range (where electrons have low energy and bend significantly) the errors accumulating from keeping the fibers parallel are no longer insignificant. The right-hand side of the parallelogram shown is actually equipped with a slot to allow the lower rail to rotate inward and deviating from this parallel arrangement. It can be shown that the natural alignment of the fiber modules contains allows a small angular shift from one fiber module to the next, satisfying to the necessary extent the alignment with the electron trajectories. |