Fluorescent Tube "Spark Chamber" for Cosmic Ray Muon Detection
Simple Do-It-Yourself (DIY) "Spark Chamber"
Based on an experiment performed by Sascha Schmeling et al. in 2000 at CERN.
This is another method for detecting and visualizing cosmic ray muons. The detector just
contains several fluorescent tubes (often wrongly named neon tubes), which needn't
be functional, wire meshwork and a high voltage supply.
Place at least 2 tubes above each other, wrap wire meshwork around each tube and pass the wire on to
the next tube, wrap the wire around the tube again etc. as outlined in the schematic and
connect the wires to the high voltage supply (black = GND; red = high voltage).
Turn on the power supply and rise the voltage - depending on the tubes, wire meshwork, number of turns and the spacing
of the wires, faint flashes in each segment will occur between a voltage of 100V to about 1000V DC. As soon as a
muon flys thru the tubes, the gas inside the tube is ionized. The ionized particles are accelerated
due the high electrical field, produce a particle cascade and a faint flash ("spark") will occur
within each tube.
Since also terrestrial radioactivity can trigger a flash, just look for flashes occuring within several
tubes at the same time - if that happens, a muon was flying thru those tubes.
A single radioactive decay has not enough energy to trigger an event in more
than one tube.
NOTES:
- You need to operate this experiment in total darkness in order to see the faint flashes!
- Use ~5mm x 0.8mm wire meshwork (used for grounding) - insulated or even bare wire works poorly or not at all
- Experiment with the spacing of the wire and the number of turns of the wire around the tubes
- Use thick tubes (38mm diameter) - the 26mm type don't seem to work
- Also the length of the tube is critical: try to get at least 1200mm long tubes
- If you get old tubes from a recycling center, check if they are for visible light. Many 38mm tubes
are UV tubes used for solariums (tanning booths) - those don't work, since our eyes can't see ultra
violet light.
This is the setup which worked best for me so far: 5mm x 0.8mm wire meshwork; 3 turns around each tube;
spacing of about 12cm; voltage at about 850V DC. For some reason only the outermost segments flashed - the
reason for this behaviour has to be determined yet. The background was about 1 flash every 2-3 seconds.
Positive muon detections (concurrent flashes in 2 segments on upon each other) about every 30 +/-15 seconds.
You will see that this setup works only after some trial and error. As outlined in the notes above,
there are several factors which contribute to either success or failure. But in any case this is not
a reliable method to detect muons, but rather a fun, unusual and cheap method for muon visualization.
BE VERY CAREFUL WHEN HANDLING HIGH VOLTAGES!
I'M NOT LIABLE FOR ANY SORT OF DAMAGE!
Last-Modified: Fri, 26 Aug 2005 19:02:06 GMT
Be very careful when handling high voltages!
cosmicrays.org cannot be held liable for damage of any sort!
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