Discussion:
There are several limitations to the experiments done here:
- Smoke detector sources have significant self-absorption, due to the thickness of the coating, leading to a broadening and lowering of the energy compared to a source designed for alpha particle spectroscopy.
- The PIN photodiode and amplifier pair are far noisier than a professionally designed detector/amplifier, and do not include optimized pulse shaping.
- There are few options in the MCA software to deal with more complicated pulses or spectra.
- Measuring the energy loss spectra while moving the sample inherently brings in geometric effects which aren't present when changing the pressure for fixed geometry.
- The stopping power measurement depends on differentiating measured energy spectra with distance, and hence have large uncertainties.
However, these limitations do not obscure the learning outcomes of the experiment. For the first time at our university we can teach the basics of nuclear and particle physics simultaneously to 40 students.
Importantly for the design of our course as a whole, we have built reconfigurable op-amp amplifiers with performance far exceeding a similar circuit built on a proto-board. We also have 20 of the STEMlab instruments which have been used for experiments probing the quantized conductance in gold wires\cite{Tolley_2013}, teaching LabVIEW by using a silicon diode as a thermometer, and in several projects in the latter part of our courses. We wanted to simplify the transition from set experiments to open-ended projects by giving students access to cheap, powerful and flexible instrumentation during the early part of the lab course. The first iteration of this course was a success, and we intend to extend this still more with subsequent deliveries.