Re: Run 4264, understanding magnetic fields in BRAHMS

From: Flemming Videbaek (videbaek@sgs1.hirg.bnl.goV)
Date: Sat Aug 18 2001 - 08:23:26 EDT

  • Next message: Jens Jorgen Gaardhoje: "Re: Run 4264, understanding magnetic fields in BRAHMS"

    Ian,
    
    There are several tools
    a) The system is read back through the CDEV control interface. This info
    which addresses changes (compared to previous)
        is available from the ~daq webpage as (surprise)
    http://pii3.brahms.bnl.gov/~daq/opus-home-daq-run/magnetStatus.html
    as the 5 items on the index page.
    
    On the page itself you get(and I attache below some info)
    >From this you see that the D2 off was not intentional and preceeded by
    errors
    starting about 17:23 caused by interchange of computer and magnet watch
    work.
    
    
    Sat Aug 18 00:21:20 2001 | D2 | 921.96417126988 | B | On, Remote
    Sat Aug 18 00:20:50 2001 | D2 | 623.95092623676 | B | On, Remote
    Sat Aug 18 00:19:20 2001 | D2 | 400.0061037019 | B | On, Remote
    Sat Aug 18 00:18:50 2001 | D2 | 356.42567217017 | B | On, Remote
    Sat Aug 18 00:18:20 2001 | D2 | -0 | B | On, Remote
    Sat Aug 18 00:17:20 2001 | D2 | -0 | B | Stby, Remote
    Sat Aug 18 00:16:50 2001 | D2 | -0 | B | Stby, Local
    Sat Aug 18 00:07:52 2001 | D2 | -0 | B | Off, Fault, Remote, Load Fault,
    Security Trip, Cooling Fault, AC Fault, DC Fault, Device over Temperature,
    Component Fault
    Sat Aug 18 00:07:22 2001 | D2 | -0 | B | Off, Fault, Local, Load Fault,
    Cooling Fault, Component Fault
    Fri Aug 17 23:50:22 2001 | D2 | -0 | B | Stby, Remote
    Fri Aug 17 23:49:52 2001 | D2 | -0 | B | On, Remote
    Fri Aug 17 23:49:22 2001 | D2 | -0 | B | Stby, Fault, Remote, DC Fault
    Fri Aug 17 23:47:22 2001 | D2 | -0 | B | Stby, Remote
    Fri Aug 17 23:45:52 2001 | D2 | -0 | B | Stby, Fault, Remote, DC Fault
    Fri Aug 17 23:28:22 2001 | D2 | -0 | B | Stby, Remote
    Fri Aug 17 23:27:52 2001 | D2 | -0 | B | On, Remote
    Fri Aug 17 23:13:22 2001 | D2 | 921.96417126988 | B | On, Remote
    Fri Aug 17 23:09:52 2001 | D2 | 499.98474074526 | B | On, Remote
    Fri Aug 17 23:09:22 2001 | D2 | 199.95727408673 | B | On, Remote
    Thu Aug 16 21:13:10 2001 | D5 | 350.01678518021 | B | On, Remote
    Thu Aug 16 21:13:10 2001 | D4 | 892.02551347392 | B | On, Remote
    Thu Aug 16 21:13:10 2001 | D3 | 977.99615466781 | B | On, Remote
    Thu Aug 16 21:13:10 2001 | D2 | 922.97128208258 | B | On, Remote
    Thu Aug 16 21:13:10 2001 | D1 | 1126.0109256264 | B | On, Remote
    rat code is calculated from
    
    b) The current from the RUNDB is NOT this read value, but rather the
    intended value that people put into the
    begin run sheet . This is a value guarenteed to be there, but may not be
    correct. The B-filed in the brat code is calculated from
    this value. For the run in question the filed was set to zero - the field is
    calculated based on the current, but since it is a secon oder pol (that I
    recall has an offset but check in BrMagnetVolume for contstants), this is
    probably the reason for the value read
    
    c) Additionaly the Hall probes are now all read out etc, and recorded in the
    MonitorKeithely RUNDB entries. This should also
        be made available to the code, but this has to be done. Additionaly one
    needs to convert the Voltage read to some field value
        (which I do not know), and make a cross calibration to the current
    setting/reading.
    
    Cheers, and enjoy your weekend
    
    Flemming
    
    ------------------------------------------------------
    
    Flemming Videbaek
    Physics Department
    Brookhaven National Laboratory
    
    tlf: 631-344-4106
    fax 631-344-1334
    e-mail: videbaek@bnl.gov
    ----- Original Message -----
    From: "Ian Bearden" <bearden@nbi.dk>
    To: "Brahms-L@Bnl. Gov" <brahms-l@bnl.gov>
    Sent: Saturday, August 18, 2001 6:49 AM
    Subject: Run 4264, understanding magnetic fields in BRAHMS
    
    
    > Hi all,
    > I am not sure how to direct this question, so I go for the broadest
    possible
    > group.
    > Run 4264 (which was taken from roughly 0430 to 0530 Sat. GMT, or 1130
    Friday
    > night to 0030 Sat. morning BNLNST) has, according to the shift report and
    > the run index, D2 turned off.  This is great, as it should allow me to
    > 'tune' the FFS geometry.
    > I have looked at some of the data, now, and I find that if I use the run
    > data base and the SetMagnetField() in BrModuleMatchTrack, I obtain a field
    > value (and here I must confess that I do not remember, and did not check
    > whether the message there returns the value of GetField() or GetBdl())
    > of -0.106.  This raises the question (at least to me): How do the magnet
    > settings get written into the run data base?
    > Is there some monitor that measures the current, or is it the current
    > setting?
    > Also, do we have, at present, any method of checking the fields in the
    > magnets?
    >
    > I realize, of course, that this is not a big problem since 0.1 is not too
    > big (only a few percent of the fields we actually use), but I am a bit
    > curious as to how this could come about.  Any info is much appreciated.
    And
    > you should all be happy to know that there are tracks in all TPCs for
    > 4264...at least the first sequence.
    >
    > Have a nice Saturday, I hope the weather were you are is as beautiful as
    it
    > is
    > here in Birkerød.
    > -Ian
    >
    >
    



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