Radioctivity: radiation detector with an LED

[rumelote]

TL;DR Summary

I want to create a particle detector with ion chamber principle with LED

Hi I'm a student working on my last assignment in physics department. now I'm trying to make a radioactive radiation detector with the principle of ion chamber. i want to add some new mechanism which when a charged particle pass through the chamber, an LED would emit a light. is there any reference i can use?

i will upload my work and the circuitry soon
Thank you very much

 

[chemisttree]

Isn’t that a Geiger tube?

Like this:
https://www.imagesco.com/articles/geiger/build_your_own_geiger_counter_-_gm_tube.html

 

[Rive]

Summary:: I want to create a particle detector with ion chamber principle with LED

is there any reference i can use?

Maybe this topic can be useful...

 

[chemisttree]

Like this:
https://www.imagesco.com/articles/geiger/build_your_own_geiger_counter_-_gm_tube.html

From the link above:
“The Geiger Counter produces an audible click and blinks a LED each time it detects a radioactive particle.”

 

[Rive]

From the link above:

A real DIY ion chamber (NOT a GM tube!) is a very different can of worms.
It is a real can of worms.

 

[gleem]

Summary:: I want to create a particle detector with ion chamber principle with LED

Hi I'm a student working on my last assignment in physics department. now I'm trying to make a radioactive radiation detector with the principle of ion chamber

If that is a true ion chamber detector, it measures current, due to the production many ionization processes occurring in the chamber. Thus single ionization events cannot be identified. This current is of the order of nano amps so a DC amp of great sensitivity and low noise is required.

 

[rumelote]

From the link above:
“The Geiger Counter produces an audible click and blinks a LED each time it detects a radioactive particle.”

Thanks for your response, but i tend to build an ion chamber without using the GM tube, what i intend to is to do something, like i found from the techlib.com site, where an ion chamber emits light when being approached to radioactive radiation. here is the link
http://www.techlib.com/science/ion.html#Experimenters Chamber

 

[rumelote]

If that is a true ion chamber detector, it measures current, due to the production many ionization processes occurring in the chamber. Thus single ionization events cannot be identified. This current is of the order of nano amps so a DC amp of great sensitivity and low noise is required.

Thank you for your response, yes i noticed that the current caused by ionization is very low, so I'm using the darlington pair. i follow this circuitry which i got from techlib.com .

i'm using the bc547 as the npn transistor and bc557 as the pnp transistor. another problem occur, now that my detector works not merely as radiation detector but to touch detector as well. everytime my hand pass across the chamber , the LED lights. i just don't know how to solve this problem

 

[gleem]

Out of curiosity what radiation source/activity are you using and how close do you have to be to get a reading?

 

[rumelote]

Out of curiosity what radiation source/activity are you using and how close do you have to be to get a reading?

i am using Americium 241 and Ra226, so far my detector can detect the americium, but got zero results for Ra226. like i said there is still some error when i approach my hand close to detector, the led lights.
so I'm not really sure, whether the LED lights because of radiation or the energy from my hand. i think i just found an anomaly, not sure

 

[gleem]

Hmm. That is curious. Are your sources commercial check sources with activities of about 37000 becquerel (1μ-curie )? Radium source is one of the highest radiation emitting sources per unit activity.

Regarding the interference of your hand. The ion chamber may be picking up stray electric fields from your hand.

 

[dlgoff]

... when i approach my hand close to detector, the led lights.

Can you Earth ground your ion chamber? It probably has to do with the stray electric field from your hand as @gleem mentioned.

 

[rumelote]

Can you Earth ground your ion chamber? It probably has to do with the stray electric field from your hand as @gleem mentioned.

i connect the cathode plate to the circuitry as i mentioned above, or should i parallel another single wire directly to the ground?

 

[rumelote]

Hmm. That is curious. Are your sources commercial check sources with activities of about 37000 becquerel (1μ-curie )? Radium source is one of the highest radiation emitting sources per unit activity.

Regarding the interference of your hand. The ion chamber may be picking up stray electric fields from your hand.

i haven't tried to check the sources, i will consult it with my teacher later.

Any idea how to block those stray electric fields?

 

[dlgoff]

... parallel another single wire directly to the ground

Yes. Give it a try.

 

[Rive]

i follow this circuitry which i got from techlib.com

You should be aware (and keep it in mind all the time) that this circuit is intended to be a simple toy, not a real instrument.
To 'repair' its flaws - well, you kind of have to put the worms back to the can.
Start over and do it bigger, more sophisticated (just try another design).

 

[rumelote]

Yes. Give it a try.

i did, and now not even a single thing was detected.

 

[rumelote]

Summary:: I want to create a particle detector with ion chamber principle with LED

soon

So here is my detector, i build it with Aluminum and Copper as the anode wire. i use the darlington pair circuitry for current gain, bc547 NPN transistor and bc557 PNP Transistor

.

 

[Rive]

I kind of confused by your statement of "put the worms back to the can" what does it mean?

You have started a project which you are not familiar with and so you have severely underestimated the difficulties (to open a can of worms).
To get a control over the project (put the worms back to can) you need a bigger can (start over, but with more care and meticulous effort).

I suggest to start with an exact replica of an ion chamber related project from techlib.com.
Based on your pictures at this point you are far from being able to freely modify the designs there.

 

[rumelote]

You have started a project which you are not familiar with and so you have severely underestimated the difficulties (to open a can of worms).
To get a control over the project (put the worms back to can) you need a bigger can (start over, but with more care and meticulous effort).

I suggest to start with an exact replica of an ion chamber related project from techlib.com.
Based on your pictures at this point you are far from being able to freely modify the designs there.

Right, i will try to put the worms back to the can, haha. but still i will put more effort on this one. thanks for your advice :)

 

[Tom.G]

everytime my hand pass across the chamber , the LED lights. i just don't know how to solve this problem

Try connecting yourself to the outer case of the detection chamber. Use a length of wire and hold it in your hand or wrap it around your wrist. Then see if the circuit triggers.

I do suspect though that a big part of the problem is the long wires from the chamber to the electronics circuit. Those really should be shielded wires with the shield connected to the Emitter of the NPN transistor stage. Do not connect the other end of the shield. You can make all that easier by connecting the wires together at the chamber and connecting them to the electronics with a single shielded wire.

Or maybe You are radioactive from handling all your test samples.

Cheers,
Tom

 

[Atomillo]

Hi:

I myself have some experience building Ion Chambers (and more specifically the models presented in that website). Some clarifications should be in order:

1.- The Darlington Pair must be soldered in air: the leakage current in the protoboard is simply too great. After it has been connected, its terminals and it's body should be cleaned with alcohol. Fingerprints add prohibitive resistance: you should work with gloves. As mentioned previously, this circuit is just a toy, but at this range of currents even toys have to be treated somewhat carefully. Also, and this has been mentioned previously, your cables are way too long, and add what I would suspect to be a considerable amount of noise, including the pickup of 60 Hz mains.

2.- Shield the transistor from light. Trust me, it can be that sensitive.

3.- What exactly are you building? The design you have presented looks nothing like an ion chamber, and a lot like the classic Spark Detector or even a Multi Wire Proportional Chamber. I add an old article about this matter: tell me if you would need more info. If you have a high voltage supply at hand (and know how to use it) you can detect alpha particles (like those emitted from your sources) without all the hassle involved into electrometer-level measurements.

Overall what I see here is a naive attempt at replicating something not fullly understood. If you start digging down the rabbit hole that are ionization chambers or rad-detection schemes in general, some reading will bring you a long way (search for the PDF of Radiation Detection and Measurement, for example).

 

[shjacks45]

i am using Americium 241 and Ra226, so far my detector can detect the americium, but got zero results for Ra226. like i said there is still some error when i approach my hand close to detector, the led lights.
so I'm not really sure, whether the LED lights because of radiation or the energy from my hand. i think i just found an anomaly, not sure

Amerecium241(smoke detector) is a alpha (5.5MeV) emitter as is Ra226 (4-10 MeV). Alpha is blocked by air or paper and beta is blocked by Aluminum foil. These also emit gamma (high energy x-rays) which pass through things easily. Similar to cloud chamber, at the University Hospital I worked at we used a ($$$) large single crystal of Germanium semiconductor.

Like a cloud chamber, a particle generates hole-electron pair that create briefly a conduction path. If you reverse bias a diode, the charge depleted region will act the same, hence visible light photodiodes. LEDs in their clear packages are like regular diodes but react to incoming light.

Another tool was Sodium Iodide crystals, in which the particles emit light if exceeding speed of light in that dense crystal.

Astronauts mention seeing flashes of light when eyes closed; cosmic rays emitting light inside the human eyeball.