BigBite Optics et cetera #19

Compass measurement:

In the report that Andrej prepared is a small problem with the orientation of the target coordinate system. Please see the figure below for the explanation.

Current configuration during Ay and ee'd

Plots below show currents in all three Helmholtz coils during Ay and ee'd:

Results of Compass calibration:

Here are the results of the compass calibration: TrueFieldOrientation.pdf

BigBite Magnetic Field:

Here are the plots of simulated BigBite magnetic field. This simulation was done by Vladimir. He prepared a 3D mesh for all three components of the field. The distance between two points in the mesh is 2cm in every direction. Here are the plots for few different x (horizontal direction).

Using these result I then made an algorithm that calculates field density in any arbitrary point in the bigbite using 4D interpolation. Here are some of my results.

BigBite Simulation:

I put this new (more realistic) approximation of the BigBite magnetic field into my BigBite simulation and realized that results have changed dramatically. The bending angle of the central track is now 25deg instead of 20deg, that we got with the old simulation. This value now agrees with the BigBite NIM article from NIKHEF. The simulated vertical acceptance also agrees with the true value (+- 24mr). However, the horizontal acceptance seems to be smaller than the true one (+-10mr). I am still trying to understand this discrepancy. Here is the plot of the simulated track, with the old and new field.

Last modified: 08/18/10