Diffusion pump help

[guest]

Just got my diffusion pump.
It is a really good one.
But like all things Ebay it's got something going on.
My pump is a 5" throat device that is water cooled and nicely built of stainless steel.
The heater is a 220 volt unit.
That's the good news.
What I don't understand is the setup of this pump.
It has a standard foreline inlet.
But it's the high vac side that's weird.
The large opening is sealed with a bolted on cover ( Whew!)
It has a 1 1/2 tube from the top of the main unit to a What looks like a water cooled baffle of some sort.
On top of the baffle is a threaded fixture with a brass
fixture mount on top. It is a 3/8" opening.
I've seen a few diffusion pumps before but this looks like a custom rig. I can remove stuff and make it work like a champ but don't want to blow up anything vital.
The attached tube rises 3" above the main opening.
Everything looks like normal asa fittings.
Is this some kind of ganged pump?

Larry Leins
Physics Teacher

[guest]

My buddy from National Bureau of Standards just laughed. He told me that the reason I had never
seen a Liquid cooled guage port is that the government was too cheap to buy them like that.
Mystery solved.....

Larry Leins
Physics Teacher