sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hi John,

One of the names that you've missed is Zeynep Altinbas --- actually the only female major participant in this Test.   ( I don't include Anette Meier coming two times to verify our 5
Gauss line. :-) )   Zeynep is in charge of the PXIe, the "central-brain" of the quench-protection system, doing the voltage tap comparison (with the thresholds) etc.  and sending
the "quench signal" when something violate any threshold or a heart-beat (from PLL) was lost.

Kin

On 02/13/2018 05:33 PM, John Haggerty wrote:

Kin,

We were watching the ramp (and holding our breath) during today's review.  Congratulations to you and all the many people who have made this possible.  From the extension designed by Paul Kovach in SMD to the work on the low field test by Joe Muratore and many others, to Carl and Pablo on the power supplies and quench detection, and the design and construction of the flux return by John Hock and others, and the cryo work by Roberto and Paul, and controls by Winston and others... I know I haven't named everybody who has worked on this, which is what makes Brookhaven such a great place to do science: the collection of expertise, experience, and stick-to-itiveness that makes it possible to do more than any one of us could.  Thanks.

On 2/13/18 4:57 PM, Kin Yip wrote:

Hi,

As Achim has disclosed earlier, we reached ~4830 A this afternoon and due to the availability of Liquid He, we stayed for ~40 minutes. They actually watched that the gas-cooled lead voltage stabilized, stopping to go up, before they started the slow discharge.   Carl and the Cryo group have been discussing about optimizing the lead flow rate from 0.27 g/s to 0.33 g/s as the max.  (at 5000 A).   Brian van Kuik told me that the max. they reached was ~0.31 g/s.

This morning, when we tried to ramped to 2 A/s to 4000 A, the pet page etc. suddenly all disappeared in front of us (in 912 or my office or anywhere).  The C-AD control file system crashed ! When did this happen last time ?!    One felt like everything was against us, at that point.   At that time, the power supply/magnet was ramping up and after the file system crash, we could only observe from Zeynep's quench-detection system (PXIe) screen  or Pablo's power supply touch-screen :-)   Around 2500 A, Carl's phase-locked-loop (PLL) was lost which causing Zeynep's PXIe to issue a fast-discharge (for quench protection) --- which had not happened since we started testing in 912.   Maybe, the loss of PLL was due to the control system failure or maybe not ??!   ( Depending on who you ask ... )   We couldn't ramp (even John Morris discouraged from there doing so) as there was no Logging (slow
logging or fast logging) to monitor etc.

Luckily, shortly before 1 pm, the control system was back to operation.   After testing a bit at 100 A, we started ramping at 2 A/s to 4000 A and then 2 A/s in 200 A step (or 230 A for the last step).

As mentioned, we reached ~4830 A and stayed there for ~40 minutes and did the slow-discharge, to avoid the Liquid Helium tank being empty.  The slow-discharge is slow and the calculator that I created said that it'd take ~6102 seconds to go from 4830 A to 0.   It's slower at the end :-)    Just like BaBar, people don't want to wait for it to slowly go to 0.  So, at below 1000 A (or ~966 A or so), we did a fast discharge.  This saved
waiting for another almost 40 minutes.

I attached the 2018-2-13.gif for today's current and Magnetic field.  Our Opera calculation/simulation assuming 1010 steel, for this Return Flux
(Steel Box), predicts a magnetic field of 1.37 T at 4596 A.     At ~4830 A, we got ~1.34 T whereas at 4600 A, we got ~1.275 T. Almost 7% lower than
expectation.   I guess the probe was probably not exactly at the center and the 40+ years old steel is far from what we expected (rusty too).

A surveyer today was also there trying to measure any sidewards expansion and I heard that he got only 0.002 inch (within their error/uncertainty)
between 0 and 4000 A.   Jon Hock came to my office to make me plot his linear pots and there we also saw the maximum of 0.002 inches between 0
and 4830 A.   All smaller than the engineers have been worried about.

Kin

PS:
I've read Monday Memo and heard about the "new" Day-to-Day Appreciation and Recognition more than once.   I'm trying to fill out the "Group Food Celebration Recognition Form", https://sbms.bnl.gov/SBMSearch/subjarea/55/5509e011.pdf ,

to see whether it'd work :-)



On 02/13/2018 02:57 PM, Franz, Achim wrote:

Great news

Magnet is at 4830A = 105% operating point

Sent from my iPhone
Achim Franz


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