WARNING: THIS DATA IS BASICALLY UNUSABLE There was no WLS fiber in the sim and the optical interfaces were ill-defined.

My goal was to investigate which elements of the simulation resulted in greater photon generation, and to replicate the physical light loss measurement if possible. I investigated the following properties:

• PTFE reflectivity (1.00, 0.99, 0.98, 0.95)
• Al Mask reflectivity (1.00, 0.99, 0.98, 0.95)
• Al Hole size (ranging in 0.2 mm steps from 1 mm up to 2.4 mm)
• Air gap (none vs. 0.1 mm; for comparison, PTFE thickness is 0.5mm)
• WLS thickness (Standard of 1.03 mm (1mm core, 0.03 cladding) vs. 2.06mm (2mm core, 0.06mm cladding) vs. no WLS fiber)

I will be examining the number of PE detections in each case, seeking to obtain a computational analogue to our experimental data posted here: Effect of WLS Fiber on Energy

First, the PE counts from the unmasked (“whole”) scintillator are shown below. Each PE mean and uncertainty was obtained by fitting a Gaussian to the PE count peak location, and the uncertainty was taken as the statistical uncertainty on that mean location (this is not the same uncertainty obtained by using the std. dev. of the Gaussian).

For comparison, the experimental unmasked results yielded 1770 +/- 20 PE (estimating the error in mean location here, but it's close to what my error method would yield). This indicates that a PTFE reflectivity of R=0.99 is the most appropriate choice. This agrees with measurements of PTFE reflectivity Study on PTFE reflectivity, cites 99% above 350 nm cites reflectivity of 95%+ achievable depending on number of layers wrapped, especially above 0.5mm which is the PTFE thickness I'm using

With these results, I chose a reflectivity of 0.99 across the spectrum. This is a crude estimate perhaps, but I'm going to try to achieve comparable PE detections using this PTFE reflectivity for the masked sample. The two most important parameters for the PE counts in the masked sample were the size of the hole in the Al mask and the Al reflectivity. I chose a range of reflectivities for Al to be 0.95 - 1.00, a realistic upper bound for highly reflective types of Al foil. I also discovered that we may have been dramatically underestimating what might be realistic for the Al hole size. I tried poking some holes and measured them. I've given a matrix below with the resulting data:

For comparison, the experimental case yielded about 304 +/- 11 PEs. A comparison of the two experimental/computational results are shown below:

The “default” settings:

• Al Reflectivity: 1.00
• PTFE Reflectivity: 0.99
• Air gap: 0.1 mm (kept for all runs since it didn't end up making a statistically significant difference)
• The geometry: an elliptical tube of major axis 21.14 mm, minor axis 19.38 mm, length 4.5 cm.
• Hole size: 2.2 mm

The muons are incident in a 1cm by 1cm rectangle projected onto the scintillator, as if it was being triggered from two crossed scintillator paddles. The muons crossed the “short” end of the cross-section of the elliptical cylinder (i.e. parallel to the 19.38 mm axis of the ellipse)

Using these default settings, I also tested a few special parameters: Air gap (with and without the mask) and WLS fiber size (to see if a larger fiber made a difference with the same Al hole size):

The presence of the air gap seems to not make a significant difference in the results of the simulation. Also, more significantly, the size of the WLS fiber (or even its presence at all) seems to have no impact on the number of PE detections. Our scintillator is probably just not long enough for the photons trapped by the WLS fiber to overcome the photons which would have struck the PMT face anyway.

All of the data used here is stored in /data/chocula/schmitz/condor_output/HannahTestStand/data/paper/muon2/