sPHENIX discussion of the superconducting solenoid

[John Haggerty <haggerty AT bnl.gov>]

Dave,

From the experiment's point of view, if we could reverse the field, we 
would only do so once or twice during a long RHIC run, as we do in 
PHENIX.  To me, it has always been an unproved assertion that there is 
all that much benefit from reversing the field in order to understand 
the systematic errors in the tracking, because after you do it, you have 
to recalibrate everything, but whenever you change the conditions of an 
experiment in a controlled way, there is the potential to learn something.

I didn't reply earlier because it's not clear at all to me whether 
reversing the polarity is feasible from the point of view of mechanical 
stress and strain and the effects on the magnet in the case of a quench. 
 After thinking about it, I'd have to defer that to experts who could 
calculate it.

But it seems to me that we would not need to reverse the polarity any 
more than PHENIX or STAR does now, and it takes a while to ramp up and 
ramp down anyway, so going to the trouble and expense of having a 
reversing switch does not seem necessary.

I suppose we might want to start with the field "the same direction" as 
in BaBar... if we can figure out what that was.

On 7/9/15 1:34 PM, Phillips, David B wrote:
> The power supply/dump resistor from SLAC does not have a  reversing switch.
>
> Do we want/need one for sPHENIX?
>
> David Phillips
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John Haggerty
email: haggerty AT bnl.gov
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