sPHENIX discussion of the superconducting solenoid

[John Haggerty <haggerty AT bnl.gov>]

I'm sorry, I missed the earlier email due to travel, but, in general, if 
it worked for BaBar, it would work for us.

In more detail, the two components of momentum resolution in a 
solenoidal tracker, multiple scattering and space point resolution, both 
go as 1/B in an approximation where space points are measured on a 
radial grid, and we're trying to achieve about 1% momentum resolution at 
low momentum.  Although we would have to do a little more realistic 
study to make sure there is no oddity due to the much less uniform 
distribution of measurements, it seems unlikely that 0.01% variation 
would be a big contributor to the resolution.

A possibly bigger concern is the effects of electrical noise and pickup 
on detector electronics which may have preamps sensitive to a few 
hundred electrons.  I can't think of a good way to estimate this, but I 
know that in both E787 and PHENIX, there was quite a bit of work to get 
the magnet power supplies as quiet as possible, and Pablo probably knows 
whether STAR required any special treatment of the regulation of their 
solenoid.

I'm sorry, I keep missing these meetings because the sPHENIX electronics 
meeting which alternates with it seems to have gotten out of phase....

On 7/22/16 7:27 PM, Kin Yip wrote:
> Hi,
>
> Pablo Rosas (from C-AD) gave a presentation about the power supply (for
> sPHENIX Magnet) this afternoon for more than 1 hour from 3 pm,
> in front of D. Bruno, J. Galarraga, I. Marneris, J. Sandberg, C.
> Schultheiss and myself.     This is about what he's been doing and what
> he'll
> do, the schedule etc.
>
> I've placed his powerpoint here :
>
> https://collab.external.bnl.gov/sites/sPHENIX-Magnet/Past%20Presentations/2016-7-22%20sPHENIX%20Power%20Supply%20review.pptx
>
> It contains many drawings/circuit diagrams that Pablo  has made for this
> power supply --- like what he's done for other power supplies in C-AD.
>
> People have made some suggestions such as doing hipot before the power
> test, finding another magnet with higher load (more than what he's
> got ~750 A), running current over the dump resistor to test, adding DC
> output over-voltage protection etc. etc. that Pablo has noted himself.
>
> The power supply has output ~20 V and 5000 A.   It's mentioned to me
> again that its output regulation (or fluctuation) is ~0.01%.
> This probably means that the B-field has a stability or instability of
> ~0.01%.  This was what BaBar has lived with.   ( So, it's good enough
> for us ? )
> I've never heard of any physics requirement on the B-field [ but I'm
> quite ignorant :-)  ].     I've sent an email to John Haggerty about this.
>
> Kin
>
>
>
> _______________________________________________
> Sphenix-magnet-l mailing list
> Sphenix-magnet-l AT lists.bnl.gov
> https://lists.bnl.gov/mailman/listinfo/sphenix-magnet-l


--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358