Interactive Nixie simulation Nagy Sándor honlapjára Nagy Sándor: Nukleáris Címszavak Glosszáriumába, melyhez ez a lap is tartozik A Tékába, mely ehhez hasonló animációkhoz/szimulációkhoz vezet Nagy Sándor webhelyén

If probability theory and statistics are your favorite try this and this too.
Here you can find a picture of an instrument featuring tubes like the ones below. || To the Hungarian version english
The frames used in the simulation are from Wikipedia. I borrowed the trick of JavaScript-based animation from Chip Chapin. Then I asked Mr. Gábor Gombási E-mail küldése to add some features to it which I missed. He did a great job: thanks for it!



Set count rate to


Swap Nixie for Dekatron nyíl

How to use it

The (mean) count rate can be set by the user. You don't have to stop the counter: as soon as it detects the next radiation particle it notices the change and adjusts itself to the new rate that you set. It is very instructive to follow this sequence of steps: (1) start the counting, (2) type in a couple of 0s after the preset value, then (3) watch the tubes for a while. Then (4) hit the Backspace key and after a short while hit it again to see how the behavior of the tubes changes. Can you see that the randomness of radioactive decay (or background) is more obviously present in the behavior of the second tube?

Random behavior

I am using exponentially distributed random numbers to drive the simulation. That means that the waiting times between subsequent decay events are assumed to follow exponential statistics. This type of sequence is referred to as a Poisson process. Suppose you are dealing with a Poisson process. If you measure the number of events occurring within a set interval of time (like 1 min, for instance), then mathematicians will tell you that those random 'counts' will be distributed as Poisson. That is why nuclear scientists expect that counts measured with a long-lived radionuclide obey Poisson statistics.


If you push up the count rate too much, you will find that that the simulation will not get proportionally faster.
I could claim that this is because I have cleverly programmed the dead time of the detector into the simulation. However this was not necessary.
The truth is that this behavior is due to the browser (I think). It is caused by its inability (or the lack of its willingness) to follow arbitrarily fast changes demanded by a script.
It is worth checking the original animated version of the table below, in the second column of which animated numbers show up in sequence at different rates:

The numbers are supposed to swith at the frame rate given in the first column, that is, the animation is in the first row should be the fastest.
However, I am using now a Chrome browser which shows the second one (0.02 seconds) as the fastest because it cannot keep pace with the first one.
This is why I have limited the number of digits in the input box to six.

Nixie tubes are still around

In the nuclear chemistry lab at ELTE, BSc students still have a chance to work with simple radiation counters featuring Nixie tubes—instruments that are considered nostalgia pieces elsewhere. I took the picture below on March 21, 2012. It shows a model produced by Gamma Works in the last decade of the 20th century.

Vissza Nagy Sándor honlapjára. Releváns |tIt| kínálat: Nukleáris Glosszárium, Asimov Téka

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