Changes

       <li> These electrons will pass through the center of the first column of SciFi fibers</li>

       <li> These electrons will pass through the center of the first column of SciFi fibers</li>

   </ul>

   </ul>

   <li>Using &beta;₁ calculate the X-displacement along the focal plane (&Delta;x) from the center of the first fiber column to the center of the sixth fiber column of the first bundle support</li>

   <li>Using &beta;₁ calculate the X-displacement along the focal plane (&Delta;x) from the center of the first fiber column to the center of the sixth fiber column of the first bundle support</li>

   <ul>

   <ul>

       <li>Repeat the above two steps until the bundle support angle &beta; (e.g. average between &beta;₁ & &beta;₆) does not change appreciably</li>

       <li>Repeat the above two steps until the bundle support angle &beta; (e.g. average between &beta;₁ & &beta;₆) does not change appreciably</li>

   </ul>

   </ul>

Now we know the focal plane crossing locations for the first and sixth SciFi columns in our first bundle. Additionally, we know the &beta; angle of the first bundle (noted as &beta_avg above), which gives us the optimal alignment for each fiber in the bundle to their respective electron's path. The &beta; angles for the first and sixth columns will be off by the same magnitude, but with opposite signs.

 

 

 

Now we know the focal plane crossing locations for the first and sixth SciFi columns in our first bundle. Additionally, we know the &beta; angle of the first bundle (noted as &beta;_avg above), which gives us the optimal alignment for each fiber in the bundle to their respective electron's path. The &beta; angles for the first and sixth columns will be off by the same magnitude, but with opposite signs.

[[Image:e_path_in_Bundle.png|center|thumb|800px|Figure : Sketch showing the path of electrons that pass through the center of the fiber columns near the focal plane. At the back-end of the 2 cm. SciFi a misalignment of around 0.03 mm (with respect the the fiber's axis) results from using an averaged &beta; angle for the bundle support location.]]

[[Image:e_path_in_Bundle.png|center|thumb|800px|Figure : Sketch showing the path of electrons that pass through the center of the fiber columns near the focal plane. At the back-end of the 2 cm. SciFi a misalignment of around 0.03 mm (with respect the the fiber's axis) results from using an averaged &beta; angle for the bundle support location.]]

Unfortunately, the 5x6 fiber bundles were designed with two 5x3 bundle halves offset so that the center of the front face of the center column in each bundle half would sit on the magnetic focal plane for a &beta; angle of 12.0^o. This angle was selected as a compromise to allow coverage over the photon energy range of 10 - 5.6 GeV. <i><u>As a side note</u> - If required and finances permit, the 17 bundle supports can be easily redesigned for a different &beta; angle. This redesign would take less than an hour of CAD work, with a manufacturing turn-around time in as little as two days. Costs are estimated to be around $2k. A CAD drawing of a new bundle support design already exists, which incorporates updated locations of the threaded holes for mounting the clamps that keep the bundle straps in place. The best time to replace/modify the bundle supports, if so desired, would be during fiber replacement. This way the new fibers can be mounted to the new bundle support outside the tagger hall, before ever making it to JLab. A conservative time estimate for changing the TAGM fiber configuration would be approximately two days (16 hours).</i>

The 5x6 fiber bundle supports were designed with two 5x3 bundle halves offset such that the center of the front face of the middle column in each bundle half would sit on the magnetic focal plane for a &beta; angle of 12.0^o. This angle was selected as a compromise that would allow coverage through the photon energy range of 10 - 5.6 GeV. <i><u>As a side note</u> - If required and finances permit, the 17 bundle supports can be easily redesigned for a different &beta; angle. This redesign would take less than an hour of CAD work, with a manufacturing turn-around time in as little as two days. Costs are estimated to be around $2k. A CAD drawing of a new bundle support design already exists, which incorporates updated locations of the threaded holes for mounting the clamps that keep the bundle straps in place. The best time to replace/modify the bundle supports, if so desired, would be during fiber replacement. This way the new fibers can be mounted to the new bundle support outside the tagger hall, before ever making it to JLab. A conservative time estimate for changing the TAGM fiber configuration would be approximately two days (16 hours).</i>

Each bundle has a "pivot point" that when placed on the focal plane, provides the optimal y-displacement from the focal plane for each fiber column in that bundle. If the bundle &beta; angle &ne; 12^o, then the 1^<u>st</u> & 6^<u>th</u>, 2^<u>nd</u> & 5^<u>th</u>, and 3^<u>rd</u> & 4^<u>th</u> fiber columns will have the same magnitude offset from the focal plane in Y, but with opposite signs. This is all provided that when the bundle support is mounted on the parallel railing system the tagger magnet's focal plane passes through the midpoint between the front and rear bundle halves (the so called pivot point).

Each bundle has a "pivot point" that when placed on the focal plane, provides the optimal y-displacement from the focal plane for each fiber column in that bundle. If the bundle &beta; angle &ne; 12^o, then the 1^<u>st</u> & 6^<u>th</u>, 2^<u>nd</u> & 5^<u>th</u>, and 3^<u>rd</u> & 4^<u>th</u> fiber columns will have the same magnitude offset from the focal plane in Y, but with opposite signs. This is all provided that when the bundle support is mounted on the parallel railing system the tagger magnet's focal plane passes through the midpoint between the front and rear bundle halves (the so called pivot point).