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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