sPHENIX discussion of the superconducting solenoid

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

Hi,

I've also played converting the voltages to strain and also used the thermal 
correction, by using the coefficients that we've got from BaBar.
I've used the definition:

              strain = dR / R(without strain) / Gauge-factor    

where dR = R(measured) - R(without strain).      R(without strain) and 
Gauge-factor were provided by BaBar.

I've made thermal correction using the formula:   thermal correction = -56. + 
2.49T  -1.49E-2*T^2 + 1.9E-5T^3 (where T in deg. Celsius from BaBar) 
but the thermal correction is very small when the temperature was ~25/26 C or 
so.    And then corrected strain = strain - thermal correction.

This is from what I've read from the BaBar pages (that Thomas Tallerico/Paul 
Orfin have pointed me to in the past).   So, let me know if the
above doesn't make sense.

I somehow looked at the strain voltages for the two datasets before and after 
the rotation (taking mean/rms on all the measurements).    Apparently,
it's more interesting to look at the values during rotation as John has 
shown.  

But here I just showed a plot of the strains before and after rotation for 
all 28 strain gauges.  I compared with a few that have obvious trends in 
John's 
plot and it seems looking at the strain voltages aren't that different from 
just looking at the strain.

Kin

-----Original Message-----
From: sphenix-magnet-l-bounces AT lists.bnl.gov 
[mailto:sphenix-magnet-l-bounces AT lists.bnl.gov] On Behalf Of John Haggerty
Sent: Saturday, August 08, 2015 4:18 PM
To: sphenix-magnet-l AT lists.bnl.gov
Subject: [Sphenix-magnet-l] First look at the strain gauges

Thanks to Piyush Joshi and his students and Paul Giannotti, we have some data 
from the magnet's strain gauges before, during, and after the rotation on 
Thursday and Friday.  I took a first look at it, and found it was quite 
stable while the magnet was sitting still, with remarkably small RMS spread 
in the measurements, about 5 mohm in the nominally 350 ohm strain gauges.  So 
I went on and looked at one of the files where the rotation angle was 
measured, and it looks like many (but not all) of the strain gauges saw the 
effect of the rotation.  I didn't see effect of temperature in the small 
temperature range of a few degrees C, so it looks pretty real to me.  That's 
nice, it will give us some knowledge of what we can expect to see in the 
cooldown.  I attached plots of the strain gauges as a function of the angle 
they recorded for the 28 strain gauges.

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

Attachment: strain.gif
Description: strain.gif