Can i use a neon lamp as radiation detctor?

[patric44]

hi guys
i was just wondering if i can use one of those neon indicator as some sort of ionization champer
or as a crude geiger-mullar tube.
and use the basic circuit of the radiation detector to make a simple radiation detector/counter
this is the circuit i came up with :

so the circuit works as folowing :

1- the radiation ionize the neon which is already close to its breaking Point from the applied voltage
2-then the electron accelerated tho the anode passing to the capacitor forming a pulse
3-then this small pulse trasformed to a square wave using a shmidt triger circuit or a comparator
4-then counting it using the arduino .

i need your opinions if this could work to start building it ?
thanks.

 

[tech99]

The Neon tube has a break-down voltage of about 100V, so 12V is not enough. A string of PP3 batteries would work. Once the tube strikes, it will keep burning. I believe they are sensitive to ionising radiation and also electric fields and microwaves. The series resistor must be higher, maybe 100k or 1M to avoid over heating the tube. If you shunt the tube with a capacitor, it will strike at intervals, and maybe the time interval will be radiation sensitive. I think the subsequent circuitry is less important than getting the tube to detect radiation in the first place.

 

[tech99]

Also in your circuit, I notice that the 1nF capacitor will pass pulses of about 20 volts directly to the logic gate, which it might not like.

 

[patric44]

The Neon tube has a break-down voltage of about 100V, so 12V is not enough. A string of PP3 batteries would work. Once the tube strikes, it will keep burning. I believe they are sensitive to ionising radiation and also electric fields and microwaves. The series resistor must be higher, maybe 100k or 1M to avoid over heating the tube. If you shunt the tube with a capacitor, it will strike at intervals, and maybe the time interval will be radiation sensitive. I think the subsequent circuitry is less important than getting the tube to detect radiation in the first place.

thank you tech99 for resbonding
i didnt mean to but 12v( those numpers from the proteus8 i didnt bother to change its value )

i didnt understand what you mean by (once the tube strikes ,it will keep burning) !
- the resistor that value was just random value i will use 1M or 10m as you sugested
with the capacitor problem how can i determine the best value to use ? i mean on what basis
- should i use a voltage divider after the cap?

 

[tech99]

The tube requires, say, about 100v to strike, but will then continue alight with about 80V. So once it strikes it will not go out.
The capacitor will give a time constant with the resistor equal to CxR, so for instance 1M x 10uF = 10 seconds. Actually it will flash faster than this.
The logic circuit must not load the neon, so must have an impedance much higher than the series resistor. I suggest a small capacitor - maybe 1nF will be OK - and maybe you could protect the logic input with a 5 volt Zener. It is possible that a very slow flash rate would be best.

 

[patric44]

thank you so much tech99.

but i have another question :) :
- the counting on the circuit depends on C*R (the flash rate) not the radiation ionization it self (or that wouldn't matter since i can add some correction on the arduino )
and what that correction would be ?

 

[tech99]

I think the flash rate will increase if radiation is present. I cannot see another method of avoiding the continuous glow of the tube after it fires.