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
> ----------------------------------------------
>
>
>
>
>
>
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