3" by 2.125" BC412 plastic detector by iRad

It is certainly possible to roll out your own detectors for cosmic ray studies. Building your own detectors can be fun! Kits of parts are available from iRad Inc at the address below.

If you want to skip this step and move on to taking the data, we recommend buing a detector rather than building one. We performed our studies using the detector shown below.

Figure Det.1. A 3" by 2.125" plastic detector by iRad Inc. is sufficient to get you started. Do not forget to order the High Voltage / signal splitter box!

The detector is available from stores.ebay.com/The-Rad-Lab. You can also e-mail your questions to Tom Hall at iradinc @ att.net. His offer includes complete detectors, DIY detector kits, and parts such as phototubes and scintillators. You will find his assortment very helpful for assembling your desktop cosmic ray laboratory.

General guidelines for optimizing the detector

We have not tested the following loose guidelines yet. These are just our thoughts.

• Increasing the detector area will increase both the count rate and the number of random coincidences (proportional to the count rate).
• Increasing the detector thickness will increase the probability that the mu-meson stops within the detector volume (proportional to thickness).
• Increasing the linear dimensions N times will increase both the count rate and the number of random coincidences N*N times, and the number of captured mu-mesons N*N*N times. The true-to-random ratio will improve (N*N*N)/(N*N) = N times. At the same time, the fluctuations will decrease N times (square root of the count rate).
• If we define the figure-of-merit FOM as signal-to-noise divided by fluctuations, then the FOM will improve N times.
• Increasing the stopping power is a separate way of improving the number of stopped mu-mesons. This can be achieved with detector medium of higher density than the standard plastic. Scintillators such as NaI(Tl), CsI(Tl), lead glass, barium fluoride, or BGO may be available from your friendly National Laboratory or university. You may also consider using LSO or LYSO, but these scintillators contain natural radioactive isotopes which will increase the random background.
• Water is a promising medium because it is readily available in large quantities (did we need to say this?). We envision using distilled water in order to eliminate natural radioactivity such as potassium-40. A dehumidifier can become a good source of such pure water. The main hurdle is how to reliably attach a photosensor to a water tank.

We will update this space with more detector ideas in the future.