Tagger raytracing results
D. Sober 

(Links to results of some earlier studies can be found in the chronological listing chrono.html)

Path lengths in tagger magnet - 03-Aug-2017

Energy overlap of TAGH counters after 2016/2017 - 08-May-2017

Results of Fall 2016 survey of beam elements - 30-Jan-2017

Calculations relating to possibility of scattering to counters in same plane - 02-November-2016

First results from tagger Monte Carlo simulation -- 13-Jul-2016

Derivatives files for high-energy rays (no quadrupole) -- added 03-Jun-2016

High-energy rays (6.69 GeV < E_e < 9.00 GeV) -- Calculated 07-Jan-2016
Note: These rays use a different SNAKE setup, with the EXIT field box instead of the FOCAL field box.
[The derivatives for low-energy rays (0.18 GeV < E_e <6.99 GeV) were posted on 26-June-2015.]

Tagger beam pipe collimation of low-energy electrons -- rev. 18-May-2016

Beam optics derivatives with quadrupole -- 11-May-2016

[Note: The derivatives for high-energy rays (E_e > 6.99 GeV) with no quadrupole were posted 03-Jun-2016]

Comparison of raytracing results at 12 GeV using measured map and Tosca field -- 07-March-2016

Plot difference in x-intercept, energy, angle (Data-Tosca.pdf)

Quadrupole: Comparison of using Tosca field map and simple analytic form -- 03 March 2016

Demonstrate that the analytic form employed for the results of my note of 26-Feb-16 is just as good as using the Tosca quadrupole field map (Quad_Tosca_and_linear.pdf)

Raytracing with the quadrupole, and effects of radiator position -- 26 February 2016

A first look at using the quadrupole magnet (Quad_and_radiator_position.pdf)
Also discusses differences between goniometer and amorphous radiator positions.
Presented at beam meeting of 29 February 2016

Efficiency of the tagger fixed array -- 02 February 2016

Efficiencies, gaps between counters, and effect of dipole magnet poles (Tagger_ratios_and_gaps.pdf)
Presented at beam meeting of 02 February 2016
NOTE: All the material in this note about collimation by the magnet poles is nonsense. The beampipe apertures between the quadrupole and the dipole vacuum chamber have a much larger effect -- see notes of 18 May 2016 and later.

Derivatives of beam optical quantities (no quadrupole) -- 26 July 2015

I have calculated first derivatives of the focal plane quantities xFP, x-angle, zFP and z-angle, with respect to x, x', z and z' at the radiator, as a function of electron energy (assuming E0 = 12 GeV). These derivatives were calculated by taking positive offsets of 1 mm in x and z and 1 electron characteristic angle in x' and z', and comparing with the central ray.
I have checked that the dependence is essentially linear except for one case: dxFP/dx'0 vanishes at the point-to-point focal plane, which intersects the nominal focal plane at Ee ~ 3.3 GeV. In this region, the calculated first derivative is small and not very meaningful.
Of the 16 possible derivatives, four (the derivatives of z and z' with respect to x and x') are exactly zero. The "crossed" derivatives of x and x' with respect to z and z' are small and, for much of their range, randomly distributed due to precision uncertainties of order 0.5 ppm.

Using the new fixed-array counter positions from the mounting plates -- 02-July-2014

The fixed-array counters were installed in the tagger hall on June 30. Only then did it come to my attention that the counter positions on the mounting plates are not the same as those in the table in the GlueX Wiki (based on our May 2013 calculations). Many of the counters were shifted along their nominal electron trajectories either (a) to increase the spacing between phototube assemblies or (b) to avoid other conflicts with mounting hardware. The net effect of these changes on the energy calibration is small but not negligible, as described below.
(Links to results of some earlier studies can be found in the chronological listing chrono.html>