MainPage:Nuclear:Summer2012:PrototypeExperiment
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The Prototype
This prototype was designed and built by Marco and Mike (graduated 2012) to model a small section of the SHMS Kaon Aerogel Detector, and to study the characteristics and behavior of both the aerogel panels and the 5" diameter PMTs. It is composed of a single metal light box in which the aerogel panel is held by a wire grid (note that the aerogel is not flush with the sides of the light box). The 5" PMT window is positioned in the bottom half of the light box, and the lid of the light box is removable to allow for changing the number of aerogel tiles stacked within.
The PDF construction plan is available here: File:Body.pdf
The Experimental Setup
The experimental setup will be composed of a triple coincidence with the initial gate being provided by two 2" diameter PMTs with plastic scintillator paddles.
2" PMT Double Coincidence Runs
The 2" PMTs are currently being tested in double coincidence for optimization. Runs have been performed over a range of high voltages (1600-2200V). There is approximately 55cm^2 of overlapping scintillator paddle area, meaning that ideally we ought to see approximately 55 muons per minute.
First, coincidence runs were performed with the scintillator paddles of the 2" PMTs approximately 1cm apart. It was found that there was a dramatic increase in the number of coincidences recorded above 2100V. At 2200V the muon count/minute ratio is 20.45 which, although less than half of the ideal expected muon rate, still shows that the setup and equipment is functional and yields strong data.
Ongoing at the moment are double coincidence runs with the same two PMTs set approximately 36cm apart (the height of the prototype with stand), in order to have a baseline for the event rate we can expect from the tripple coincidence testing with the prototype. As is to be expected, the number of coincidences is much reduced from the above number.
Upcoming projects still include making a more permanent rig for the 2" PMTs for prototype testing, as well as possibly making new, longer signal cables.
Initial Prototype Experiments
The first prototype experiment was run at JLab using 5cm of aerogel. The gate (80ns) was provided by the double coincidence of the two 2" PMTs (2000V, 50-60mV signal). The 5" PMT signal was between 200mV and 300mV (at 1800V). There were 2204 events in 17 hours.
The calculated number of photo-electrons is 2.6; the simulated number of photo-electrons is 11 on average. This discrepancy is being investigated. The calculated number of photo-electrons from Arthur's prototype with 5cm of aerogel is 9 (however this prototype used Millipore, not Mylar).
Documentation
Excel Workbook File:Coincidence runs.pdf