[Sneap] De-ionized water

[Brett Longworth]

Hi Alan,

We're using a deionized loop with a similar setup to David's. Generally, 
it's pretty trouble-free corrosion-wise, but we did have some problems 
about two years ago which coincided with starting up a new AMS on the 
same loop. During this period, the background current in our ion source 
rose rapidly and we noticed a lot of black gunk building up in the 
cooling lines. After a period of replacing DI cartridges and even adding 
a secondary deionizer on our ion source cooling water, the problem 
disappeared following a period when the new magnets and supplies were 
turned off. We use stainless, copper, aluminum, and some brass 
components in the lines, but we're pretty careful about keeping 
dissimilar metals apart.

My suspicion  is that there's a sort of positive feedback between loop 
conductivity and corrosion- as the loop gets a little bit conductive, 
corrosion starts, adding more ions to the loop, increasing conductivity 
which increases corrosion. Any ideas on this?

As far as I know, we don't have a sacrificial anode, but it sounds like 
a great idea. I think you'd want things set up such that the anode 
doesn't corrode under normal conditions, just a safety mechanism in case 
the loop gets screwed up. This might have prevented an expensive repair 
to a Danfysik supply at another AMS lab- the cooling lines developed 
pinholes after only a few years of use and ruined the supply.

-Brett





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