X-RayGasTube_YPN1 » Page 1 of 1

Years ago I remember being fascinated reading about the "homemade atom smasher "article in the book "The Amateur Scientist", Strong; I remember that electron beam targets should be light atomic weight to minimize X-Ray production. I have always been fascinated with gas discharge tubes and experimenting with them; recently in the last few years I built several using aluminum electrodes , just in case, to minimize any possible X-Ray production. I decided to check this out with one of the Geiger counters that I purchased from Ebay.

This page is to document the very brief experiment for testing cold cathode gas discharge tube's X-Ray production verses the approximate gas pressures radiation observed. The experiment was extremely brief and relative to avoid exposure to the X-Ray radiation detected. Basically the Geiger counter and high voltage 35KV power supply was active as the gas tube was being pumped; when radiation was detected the powersupply was immediately switched off.; however pressure readings had to allow for the TC sensor to catch up with the actual pressure.

While conducting this experiment I stood at some distance where the geiger count was small; and control the HV power supply switch for turning off X-Ray production. At this distance the TC gauge could be read; however because the Geiger tube connecting wire was relatively short to its control unit the radiation level couldn't be visually read. Only the audio clicking level could be sensed at a relatively safe distance. I have labeled the expewrimental results as "relative" due to the TC gauges response speed and audio clicking rate as the radiation level indication and the very short time spot check time lapse; minimizing radiation exposure. I decided that for any future experimentation, and to get accuracy, will require X-Ray shielding for my safety; I thought about surrounding the gas tube with thick lead glass for viewing. As a result I have dismandled the gas tube and put into storage until I can operate it safely.

When I started testing the gas tube; the Geiger counter ( shield open) was set about six feet from the tube. The TC gauge's response is relatively slow compared to the actual pump speed of the vacuum pump. Being careful to provide pump down time delay for the TC to catch up; the following results were observed.

Continuous count rates: some audio clicks seemed above background at about 20 microns; the count increased significantly at about 15 microns; the count rate seemed to decrease significantly somewhare between 5 -to- 10 microns. Counts in bursts: below 5 microns the tube discharged into bursts more so getting close to 1 micron ( note that TC calibretion is still in question) with associated powerful radiation count bursts. When the GM tube was placed close to the anode (see photo below) approximately the same radiation peaks verses pressure was about the same; however during the peak the audio click rate was high pitch frequency; which is very alarming; in spite using aluminum electrodes.

The book "High Vacua" , Kaye, 1927 ; free down load fromhttp://archive.org/details/texts , states in chapter III "The pressure in a gas X-ray tube of average size, in which the residual gas is air, ranges from about 0.005 to 0.01 mm..." which seems to follow fairly close to my very rough measurements.