Spark Gap Reply

[Tom N. Massey <massey@oual2.phy.OhioU.Edu>]

> I'm looking for information on spark gaps containing radioactive material that
> were used in old transformers.
> 
> 1.  What was their intended purpose?

      The base on our experience at our tandem accelerator, the purpose of 
      including radioactive material in old transformers was most likely to
      assure a that the spark gap functioned at a given voltage rather than 
      fluctuating depending on the atmospheric conditions.  The radioactive 
      decay of beta particles would have provided an ion trail to start a 
      spark across the gap.

> 2.  How long were they used?
> 3.  What isotopes were used and what quantity?  I understand Ra and Cs were
> used, any others?

      Any long lived isotope which beta decay's or is the parent of a beta 
      decaying isotope could be used for this application.   I have no 
      information on what had been used.  As little as 2,000 Bq would have 
      been sufficient to assure operation at the rated voltage,  however, 
      engineers often over design and quite a large increase over this amount .
 
> 4.  Was there a relationship between the size of the gap, amount of 
>      radioactive material used and intended function? 

> 5.  Any regulatory concerns or vendor requirements for using/labeling these
> devices other than the obvious?
      
      It is possible that this material was below regualtory concern at the
time due to the low amount of radioactive material required. (see 1)

> 
> Any information or references relating to the above questions would be greatly
> appreciated.
> 

Thomas N. Massey
Dept. Physics
Ohio University
Athens, Ohio
(614)593-4152
massey@oual2.phy.ohiou.edu