Jan2008WorkshopGWinters

From MariachiWiki

January 26, 2008, Workshop

One of several MARIACHI workshops, on January 26, 2008, several Physics teachers came together to calibrate our existing muon detectors. We have now built detectors, have installed them in our classrooms, and are collecting data. Now, knowing that they work, we needed to find the optimal operational voltage to run each one of them. We had been calling this procedure calibration, but I do NOT think it means that countrates at one site will be equivalent to countrates at another site. We'll just have the best performance possible from each detector, and that should be similar from one detector to another.

Joe Willie, from Walter Panas HS, Cortland Manor, NY
Most interesting, Joe Willie started the day talking to us about his cosmic ray projects in upstate New York. He now works in West Chester county, so I hope he comes back to visit or work with our group. He gave us links to his website, complete with data, and to the NOAA, which he found was a great source of x-ray and images.

Calibration
We spent the afternoon working on our detectors with Dima's help and under Helio's watchful eye. The objective was to find the operational point (a balance of high efficiency and low noise) for our detectors. We sandwiched one of our detectors between two previously calibrated detectors. We then measured counts for each of the three detectors, and recorded 2-fold and 3-fold coincidences for applied voltages between approximately 5V and 6V. We graphed efficiency and noise rates vs. applied voltage. The optimal operational voltage was at a point on the graph that had high efficiency but still low noise rates.

Here is the calibration curve (optimization) for detector 4 for Smithtown HS East. The optimal voltage is approximately 5.9 V: high efficiency but still low noise rate. Click for a larger image.

This optimal voltage assumed an inner resistance in the circuitry, and from the optimal voltage we calculated a value of resistor that we need to put in the detection circuit. We will iterate the process, inserting this resistor and iterating, according to Dima's procedure.

Here we see Dima et al. working on one of the muon detectors; Tania, Harry and Dima calibrating, and Joe and Gillian calibrating other detectors.
			Joanne and students Glen and Hochan confer with Helio about the current cosmic ray research project. Calibration data, and Dima, Tom and Jeff having lunch.

For me, this was one of the best MARIACHI workshops. We had a great talk to start us off, and then learned a little while we were working on our own detectors doing something to improve their performance. Here's to many more ...