Difference between revisions of "Alignment"

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<pre>
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1) create straw centers along the x axis,
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==Technical Definition==
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with inner most straw at x=0, direction pointing along +y
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This section explains how the tracker alignment is defined. 
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1a) apply panel alignment rotation in this basis
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as a right-handed rotation about x, then y, then z
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* There are three places that alignment transforms are inserted
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from db delta values du, dv, dw
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** between the whole tracker and the nominal geometry
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where u=x, v=y, w=z.  using u,v,w empahsizes that
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** between each plane and the aligned tracker
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these are not the experiment coordinates for the panel
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** between each panel and the aligned plane
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1b) apply panel alignment postion, in this basis
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* transforms
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using db values du dv and dw
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** apply rotation before displacement
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2) apply the nominal geometry transformaton to put
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** a rotation is defined as right-handed about the local x, then y, then z axes (rad)
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  the panel in the plane: push it out the x axis, tweak the z,
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** add an offset in position (mm)
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  rotate about the z axis.
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* tracker geometry object are in coordinate centered at the nominal tracker center
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2a) apply the plane alignment rotion in this basis
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from db delta values rx, ry, rz
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Here is how the geometry is conceptually built up, including the alignment
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2b) apply the plane offset in this basis
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from db delta values dx, dy, dz
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<ol>
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3) apply the nominal transformation to place the
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<li>create straws within the panel
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plane in the tracker - shift along z
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* straw direction is +y
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2a) apply the detector alignment rotion in this basis
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* straws are placed around the +x axis with the longer (innermost) straw near x=0
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from db delta values rx, ry, rz
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* the origin is the average position of the two innermost straws
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2b) apply the detector offset in this basis
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* straw z is plus or minus half the layer spacing
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from db delta values dx, dy, dz
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</li>
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</pre>
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<li>Apply the panel alignment of rotations and displacements.  The coordinates are these current local coordinates. For example, to move a panel to a larger radius in the final detector, apply a +x alignment.</li>
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<li>Place the panel in the plane.  This involves rotating the panel to its nominal phi position around the z axis, and adding its nominal displacement of about <code>x += 380*cos(phi)</code> and <code>y += 380*sin(phi)</code> </li>
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<li>Apply the plane alignment of rotations and displacements. The coordinates are the center of the plane. For example, to move a plane vertically up in the final detector, apply a +y alignment.</li>
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<li>Place the plane within the tracker.  This only involves moving it along the z axis.</li>
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<li>Place the tracker by applying the tracker alignment.  The coordinates are all the same as the final detector.  To move it closer to the calorimeter, apply a +z alignment. To spin it about its axes apply a z roation.</li>
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</ol>
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[[Category:Computing]]
 
[[Category:Computing]]
 
[[Category:Code]]
 
[[Category:Code]]
 
[[Category:Database]]
 
[[Category:Database]]

Revision as of 22:09, 28 February 2019


Technical Definition

This section explains how the tracker alignment is defined.

  • There are three places that alignment transforms are inserted
    • between the whole tracker and the nominal geometry
    • between each plane and the aligned tracker
    • between each panel and the aligned plane
  • transforms
    • apply rotation before displacement
    • a rotation is defined as right-handed about the local x, then y, then z axes (rad)
    • add an offset in position (mm)
  • tracker geometry object are in coordinate centered at the nominal tracker center

Here is how the geometry is conceptually built up, including the alignment

  1. create straws within the panel
    • straw direction is +y
    • straws are placed around the +x axis with the longer (innermost) straw near x=0
    • the origin is the average position of the two innermost straws
    • straw z is plus or minus half the layer spacing
  2. Apply the panel alignment of rotations and displacements. The coordinates are these current local coordinates. For example, to move a panel to a larger radius in the final detector, apply a +x alignment.
  3. Place the panel in the plane. This involves rotating the panel to its nominal phi position around the z axis, and adding its nominal displacement of about x += 380*cos(phi) and y += 380*sin(phi)
  4. Apply the plane alignment of rotations and displacements. The coordinates are the center of the plane. For example, to move a plane vertically up in the final detector, apply a +y alignment.
  5. Place the plane within the tracker. This only involves moving it along the z axis.
  6. Place the tracker by applying the tracker alignment. The coordinates are all the same as the final detector. To move it closer to the calorimeter, apply a +z alignment. To spin it about its axes apply a z roation.
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