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Optics and magnetic field calculation for the Hall D Tagger

Optics and magnetic field calculation for the Hall D Tagger. Guangliang Yang Glasgow University. Contents. 1 . Magnetic field calculated using Opera 3D. 2. Tagger optics calculated using Opera 3D. 3. Tagger optics along the straight line focal plane. 4. Conclusion.

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Optics and magnetic field calculation for the Hall D Tagger

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  1. Optics and magnetic field calculation for the Hall D Tagger Guangliang Yang Glasgow University

  2. Contents 1. Magnetic field calculated using Opera 3D. 2. Tagger optics calculated using Opera 3D. 3. Tagger optics along the straight line focal plane. 4. Conclusion.

  3. Part 1. Magnetic field calculation. The magnetic field of the Hall D Tagger is calculated by using a finite element software- Opera 3D, version 10.025 Two identical dipoles and one quadupole are included in the same mesh model. More than 2 million elements and 1.5 million nodes have been used in the calculation. The magnetic fields have been checked along various electron trajectories.

  4. Mesh used by Tosca for magnetic field calculation . Magnetic field calculated by using Opera 3D, version 10.025.

  5. TOSCA Magnetic Field Calculation. Magnetic field along a line perpendicular to the magnet output edge. Mid-plane magnetic field histogram calculated by TOSCA.

  6. Magnetic field along electron beam trajectories between 3.9 and 5.0 GeV.

  7. Y-component of stray field at focal plane position. Minimum distance between focal plane detector and EFB

  8. Component of stray field normal to y-direction at focal plane position. Minimum distance between focal plane detector and EFB

  9. Part 2. Optics calculated using Opera 3D. • The electron trajectories of various energies have been evaluated using the calculated magnetic field. • By using the calculated electron trajectories, optical properties of the Tagger are determined.

  10. Beam trajectories (1-9 GeV) and the straight line focal plane position Tosca. • Electron trajectories have been calculated using Opera 3 D post processor. • The focal plane position is determined by using the calculated electron trajectories and spot sizes. Different colours indicate different energies

  11. Calculated electron trajectories (81 per ray bundle). Electron trajectory bundles according to their directions at the object position (Angle variations span 4 theta_C). (3 GeV) (8 GeV) 2 1 2 1 Beam trajectories calculated from TOSCA in the mid plane for 3 GeV and 8 GeV.Those trajectories having the same directionfocus on position 1, and those trajectories having the same starting position focuson position 2.( Electrons travelling in the direction shown by the top arrow ).

  12. Sketch showing the two focusing positions Object Lens Image Position 1 Position 2 From the TOSCA calculation, the best location for a straight line focal plane is close to position 2 for the lower electron energies. For high electron energies the best location is close to position 1.

  13. Beam trajectories calculated by TOSCA in a vertical plane for 3 GeV electrons. Rays with different starting points but with a common angle Y position depends on emission angle of bremsstrahlung electrons. Exit edge Exit edge Focal plane Focal plane With quadrupole Without quadrupole

  14. Bundles are well separated at focal plane (without quadrupole)

  15. Par 3. Tagger optics along the straight line focal plane. • The optical properties have been determined using Tosca ray tracing . • The optical properties meet the requirements of GlueX.

  16. Straight line focal plane position Magnet 1 Magnet 1 Photon beam Straight thin window flange (parallel to the straight line focal plane determined by TOSCA ray tracing) Main beam

  17. Comparison of optical properties along the Straight Line focal plane (without and with quadrupole). (quadrupole field optimized for 3 GeV electrons.) Resolution. Half vertical height.

  18. Comparison of optical properties along the Straight Line focal plane (without and with quadrupole). Dispersion. Beta. (Perpendicular to electron trajectory) Beta is the angle between an outgoing electron trajectory and the focal plane.

  19. Conclusions • The magnetic field of the Hall D Tagger has been calculated by using a finite element software- Opera 3D. • The electron trajectories of various energies have been evaluated using the calculated magnetic field. • By using the calculated electron trajectories, optical properties of the Tagger are determined. • The optical properties along the straight line focal plane of the two identical magnets Tagger meet the GlueX specifications.

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