Australia's Science Forum

We have a very old model Alpha Particle Spark Counter, probably a 70's model. It has been here longer than any of us on staff and we can find no instructions on how to use it. It is encased in clear perspex, has a VOLTAGE-OFF switch on the top left hand side and the Detector head is on the front. It has a hand written instruction to use 9V. We can get it to spark at this and the counter revolves, but it does not change when the source is placed near it nor does it register the source if we do not have it sparking already. The instructions Ifound on Google, obviously for a much "younger" model, suggest a much higher voltage. We are hesitant to discard the device without knowing for sure it is not working. I would appreciate hearing from anyone with a knowledge of this model.

Yours Rhonda

Hi Rhonda,
I don't know this model directly but I have seen a detector head.
The detector must be open to the air.
The voltage should be adjusted to the point where sparking just stops.
Take care as the unit must use an internal voltage step up system.
The voltage will typically be around 1000V per mm in dry air in the spark gap.
The alpha source is then placed with the open end facing the spark detector.
It should be at a very close distance as alpha particles quickly loose their ionizing energy even in air.
Any ionized track from the particle should cause the detector to spark and count.

Hope this helps
Can't give any other suggestions without trying it myself.

you could try Eddie Bishop, a repair chap in NSW, appin I do believe.

If you have not heard of Eddie, please pm for his details.

To Pommy,
I do have Ed Bishops contact details, thank you for the suggestion.

Rhonda W

Thank you Bob,
That is pretty well what we did, but I will give it another go and see if I've missed anything.
Cheers Rhonda W