sPHENIX discussion of the superconducting solenoid

["Yip, Kin" <kinyip AT bnl.gov>]

Hi,

 

As you may see from the JPG file, the outlet temperature is now ~141 K.    The cool-down rate seems quite slow in the last 24 hours,

only about 0.333 K per hour or so.

 

You may read Roberto’s explanation (maybe even for a few times … at least I did) for how they hopefully are trying to avoid any frozen-water

blockage.   Apparently,  right now, they’re not using the Cryo refrigerator/plant and they’ll use Cryo plant once we reach 130 K … which then

should hopefully be faster (if there is no more plug reappearing J )

 

In addition to learning how to deal with various sPHENIX-related parties in this “sPHENIX Magnet project”and how to run (and change

parameters in) ”Opera” to calculate force, energy, inductance, magnetic field etc.,  I’ve learnt and experienced a little about the Cryogenics,

too J

 

Kin

 

On 03/11/2016 12:58 PM, Than, Yatming (Roberto) wrote:

 

Kin,

 

The plug is happening on return line, with the helium return temperature above 155K.

The question is, is water the plug or is air the plug.

Triple point for N2 is 63K, for O2 is 54K.

The dewpoint meter was reading -90C, [183K], and the N2 was less than 1 ppm

 

The going theory is that the coax bayonet at the valvebox, the seal between the supply and return was leaking across, so when we started sending colder gas [ 95K with just the LN2 gas cooler] on supply line, now 10K, the leak caused the return helium going into the return side of coax to be cooler than 155K.

even though the dewpoint is low, once below 183K, the water will knock out from the return helium since this is colder than 155K.

 

The source of the water is the warm helium gas with dewpoint of 183K, valve H3611 we used to mix to get the correct temperature.

So we still have the source of water, but now I am leaking 92K gas to return mixing  with 145K gas and hopefully not cold enough to knockout water.

 

Once we reach 130K supply, we can shutoff warm gas mixing, and use cryo plant, 10K supply.

 

Yes, we are being somewhat conservative.

So far so good.

 

R.

 

 

From: Yip, Kin
Sent: Friday, March 11, 2016 12:41 PM
To: Than, Yatming (Roberto)
Subject: not using the refrigerator ?

 

Hi Roberto,

 

I see that the cool-down speed in the 12 hours or so is even slower than the 12 K  a day or 0.5 K per hour.  

The cryo control room seemed to say that it’s because we’re only using the Nitrogen to cool …

 

Is it because you’re suspicious of the refrigerator giving out H2O or whatever to cause any blockage ??

( Because we had been cooling for ~10 days without blockage but after the plant/refrigerator was used,

blockage appeared. )     Or you’re just being cautious and you’ll turn on the refrigerator soon ??

 

Kin

 

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