[Amps] SS amps watercooling - was PowerGenius XL

[John Lyles]

Continuing this thread, we used deionized/deoxygenated water for our RF 
power tubes at the accelerator plant. I designed the anode cooling 
tubing to have no more than 500 uA of leakage current per hose, based on 
old RCA and Eimac application notes. This is at 23 kV DC plate voltage. 
The resistivity always stays above 2 Megohm-cm for this. We have 
Culligan bottles that are always bypassing a fraction of the 900 GPM 
that cools the four transmitters, all of the tubes.

On the other hand, we use long water column dummy loads (no resistors 
inside) that are about 5 wavelengths long at 200 MHz. They need some 
conductivity, so we use the same deionized water, then dope it with 
about 0.5% of a particular corrosion inhibitor that has a molybdate 
salt. This yields a DC conductivity (1/resistivity) of about 490 uS/cm. 
With this there is a 20 dB return loss in the load. It is tuned with the 
concentration of solute.

Both the ultra pure deionized system and the ionized doped system are 
closed loop with pumps and a heat exchanger, that has cooling tower 
water on the other side.

We have some air cooling for things like filament stem under tubes, and 
heat sinks/resistors in various power supplies, but the majority is 
water cooled 24/7.
73
John
K5PRO

> FYI:  I'm afraid I have to disagree on the statement below about
> distilled water being conductive.
>
> In industrial experiments in the use of distilled water,  I found it to
> be very non-conductive.  If I recall correctly, it has a measured
> conductivity of 50 to maybe 100 micro-Siemens per centimeter squared.
> That's not much.  Pure water becomes conductive only if it becomes
> contaminated with salt like contaminates.  For a comparison, seawater
> typically measures in the thousands of micro-Siemens per centimeter
> squared, because of the high salt content.
>
> While working on a clients project to do so, I spent many hours
> attempting to inject RF into water of various solutions.  It was very
> difficult in the lab trying to get RF to propagate thru pure water.
> Other more contaminated solutions not so much..
> 73,
> Ray, W4BYG