HI Michael-
IThe offsets that go into blast.sc_cal are LOFF0[i], LOFF1[i], ROFF0[i],
ROFF1[i] for left top and bottom, right top and bottom tubes respectively.
They are determined in the section of code:
//CALCULATE THE OFFSETS
___________________________________________________________
for (int i=0;i<16;i++){
LOFF0[i] = tdc_left_top[i]->GetMean() - 1000 - L_FLASH_POS[i] + L_COPL_POS[i];
LOFF1[i] = tdc_left_bot[i]->GetMean() - 1000 + L_FLASH_POS[i] - L_COPL_POS[i];
ROFF0[i] = tdc_right_top[i]->GetMean() - 1000 - R_FLASH_POS[i] + R_COPL_POS[i];
ROFF1[i] = tdc_right_bot[i]->GetMean() - 1000 + R_FLASH_POS[i] - R_COPL_POS[i];
I think for the NC bars, since they are horizontal, you can use cosmics to
determine the position center, and then use this to see how far off
from center the flasher connection is for each bar (it may not be off at all)
Anyway, the above lines give the offsets that are put into blast.sc_cal.
Pete
On Mon, 15 Mar 2004, Michael Kohl wrote:
> Thank you Peter for your explanations.
> However, in regard of the FLASH_POS, COPL_POS offsets that are applied in
> addition to what you determine from the flasher data, this confuses me
> even more. It looks to me like a tautology.
>
> Which offsets are used for crunching (blast.sc_cal) and how have they
> been determined??
>
>
> MK
>
>
>
>
> On Mon, 15 Mar 2004, Peter Karpius wrote:
>
> > Hi guys-
> >
> > OK I have put the macro that I used in January to incorporate
> > Chris' results and get the tdc offsets fro the tofs (which seem to be
> > correct mow after the recent test of last week). This macro runs off of
> > raw data (so you know you are not crunching with any offsets!) It is:
> >
> > /home/daq/blast/pro2004/analysis/macros/Raw/tof_tdc_offsets.C
> >
> > As for your questions:
> > > Chris has told me that your offsets analysis for the ToFs from flasher and
> > > his offsets analysis from cosmics both yield compatible results.
> > >
> >
> > This is correct but it is like "an identity" i.e. 1=1. This is because my
> > macro incorporates Chris' flasher position offsets and his offsets from
> > cosmics for coplanarity (which I believe give sector-sector offsets)" You
> > can see this in the initial lines of the macro where there is an array of
> > numbers:
> > int L_FLASH_POS[16] = {...}
> > int R_FLASH_POS[16] = {...}
> > int L_COPL_POS[16] = {...}
> > int R_COPL_POS[16] = {...}
> >
> > The first two arrays address the fact that the flasher is offset and align
> > remove the offset between top and bottom tube and flasher, the second two
> > arrays remove any sector-sector offsets (but again these numbers were
> > handed to me by Chris so he can explain from where they come)
> >
> > > Could you perhaps explain once exactly what the criterium is for the
> > > "offset" of a channel which enters the blast.sc_cal file?
> >
> > OK, in the macro mentioned, here is how the offsets are determined:
> > //CALCULATE THE OFFSETS
> > ___________________________________________________________
> > for (int i=0;i<16;i++){
> >
> > LOFF0[i] = tdc_left_top[i]->GetMean() - 1000 - L_FLASH_POS[i] + L_COPL_POS[i];
> > LOFF1[i] = tdc_left_bot[i]->GetMean() - 1000 + L_FLASH_POS[i] - L_COPL_POS[i];
> > ROFF0[i] = tdc_right_top[i]->GetMean() - 1000 - R_FLASH_POS[i] + R_COPL_POS[i];
> > ROFF1[i] = tdc_right_bot[i]->GetMean() - 1000 + R_FLASH_POS[i] - R_COPL_POS[i];
> >
> > So the target flasher channel is 1000. I take the difference with the
> > raw tdc and 1000. As for why I subtract L_FLASH_POS[i] and add
> > L_COPL_POS[i] or vice versa, why? -> you have to ask Chris. You see I
> > just put it all together in this little macro
> > Chris was the brains behind it!
> >
> > > Can you just use the flasher in common start mode as it is in every run or
> > > do you need coda in "flashrun" configuration (thinking of downloaded
> > > delays etc.)?
> > >
> > You definitely want to use the flasher with real physics data with beam.
> > This way you know you have the right delays already. Just select event
> > type 7 to extract flasher events (I thought it was 8
> > but I just checked my code and it has):
> >
> > if (raw.GetEventClass() == 7){ // is this a flasher event?
> > ...}
> >
> > > I found a macro of yours (tdc_offsets.C) which determines offsets such
> > > that tdcsum becomes 2000 (or 1000 for the average) and tdcdiff=0. Does
> > > this "target channel 1000" requirement already account for the light
> > > traveling times?
> >
> > This is an old macro - use the one listed above _ I should go through and
> > delete all of this junk.
> >
> > >
> > > Please let me know which macro you are presently using to determine the
> > > ToF offsets from flasher.
> > >
> > /home/daq/blast/pro2004/analysis/macros/Raw/tof_tdc_offsets.C
> >
> > but notice that it uses a class called TBLScRecon that writes the
> > blast.sc_cal file - you should make a version of this for the NC bars-
> >
> > Take a look at this class in BlastLib2
> >
> > >
> > > Thanks and regards,
> > >
> > > Michael
> > >
> >
> > Sure, no problem!
> >
> > Pete
> >
> > PS Chris, if you have read this, please correct any mistakes I have made!
> >
> >
> >
> >
> > ----------------------------------------------
> > Pete Karpius
> > Graduate Research Assistant
> > Nuclear Physics Group
> > University of New Hampshire
> > phone: (603)862-1220
> > FAX: (603)862-2998
> > email: karpiusp@einstein.unh.edu
> > http://pubpages.unh.edu/~pkarpius/homepage.htm
> > ----------------------------------------------
> >
> >
> >
> >
> >
> >
>
> --
>
> +-------------------------------------+--------------------------+
> | Office: | Home: |
> |-------------------------------------|--------------------------|
> | Dr. Michael Kohl | Michael Kohl |
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> | Middleton, MA 01949 | U.S.A. |
> | U.S.A. | |
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> | http://blast.lns.mit.edu | |
> +-------------------------------------+--------------------------+
>
>
>
>
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>
>
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>
----------------------------------------------
Pete Karpius
Graduate Research Assistant
Nuclear Physics Group
University of New Hampshire
phone: (603)862-1220
FAX: (603)862-2998
email: karpiusp@einstein.unh.edu
http://pubpages.unh.edu/~pkarpius/homepage.htm
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