Home » NUSTAR » NUSTAR PRESPEC » Position calculations on start/stop scintillators
Re: Position calculations on start/stop scintillators [message #18126 is a reply to message #18119] |
Thu, 09 April 2015 15:16 |
miree
Messages: 71 Registered: June 2014
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continuous participant |
From: *ikp.physik.tu-darmstadt.de
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Hi,
I guess it is not optimally calibrated. The ToF position determination is very dependent on a good calibration of all PMTs.
By PMT calibration I mean position correction, i.e. the dependence of delta_t(delta_x), where delta_t is the time delay between particle hit and PMT signal, and delta_x is the distance between the particle hit position and the PMT position.
The calibration goes like this: Plotting delta_t over delta_x and determine the slope and offset of the resulting structure
How this structure should look like a straight line (see Figure 1 of this GSI report: http://repository.gsi.de/record/52088/files/PHN-ENNA-EXP-55.pdf)
The offset (intersection of the line with y-axis) and slope (of the line) for each PMT have to be copied into the calibration file for the ToF processor "ToFStart.cal"
This calibration might change between experiments (mainly because of differences in PMT voltages, I guess).
In the prespec analysis script, these corellation plots are created in this section:
########################################################################
# Time of flight start detector
########################################################################
processor Lycca/ToFStart/Preproc UTILS.MhTdcPreprocessor
input[0:15] <- LyccaTargetTofCrate.mhtdc0[0:15]
input[16:31] <- LyccaTargetTofCrate.mhtdc1[16:31]
# ...
end
processor Lycca/ToFStart/Membrane LYCCA.CircularMembraneScintillator
pmt_time[0:31] <- Lycca/ToFStart/Preproc.output[0:31]
x_hit <- Frs/S4tracking.xs[5]
y_hit <- Frs/S4tracking.ys[5]
#....
end
# create the delata_t vs. distance corellation plots for all 32 PMTs
# Membrane.dist[i] is the distance of PMT_i to the particle impact point
# Membrane.T_Tp[i] is the time of PMT_i minus the estimated time of particle impact
for $i in [0:31]
processor Lycca/ToFStart/Diagnostics/Tdist0$i UTILS.Pair
first <- Lycca/ToFStart/Membrane.dist[$i]
second <- Lycca/ToFStart/Membrane.T_Tp[$i]
display first:second 256,0,300:512,-35,55 in TofStart_Tdist_corrlation
end
end
Note that the corellation plot depends on the calibration parameters, the complete process is iterative:
1)start with initial values for offsets and slopes in the calibration file: 0 and 0.01 are good starting values
2)determine offsets and slopes from the corellation plot
3)go to 1)
(2 to 3 iterations are usually enough)
Michael
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Position calculations on start/stop scintillators
By: LScruton on Wed, 08 April 2015 18:24
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Re: Position calculations on start/stop scintillators
By: miree on Thu, 09 April 2015 15:16
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Re: Position calculations on start/stop scintillators
By: thuyuk on Thu, 07 May 2015 17:29
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Re: Position calculations on start/stop scintillators
By: miree on Fri, 08 May 2015 11:23
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Re: Position calculations on start/stop scintillators
By: miree on Mon, 11 May 2015 13:12
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Re: Position calculations on start/stop scintillators
By: thuyuk on Tue, 12 May 2015 13:06
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Re: Position calculations on start/stop scintillators
By: miree on Tue, 12 May 2015 15:24
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Re: Position calculations on start/stop scintillators
By: thuyuk on Tue, 12 May 2015 15:39
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Re: Position calculations on start/stop scintillators
By: miree on Tue, 12 May 2015 16:40
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Re: Position calculations on start/stop scintillators
By: thuyuk on Wed, 13 May 2015 10:56
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Re: Position calculations on start/stop scintillators
By: miree on Wed, 13 May 2015 14:56
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Re: Position calculations on start/stop scintillators
By: thuyuk on Thu, 14 May 2015 12:07
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Re: Position calculations on start/stop scintillators
By: miree on Fri, 15 May 2015 10:48
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Re: Position calculations on start/stop scintillators
By: thuyuk on Tue, 19 May 2015 12:19
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Re: Position calculations on start/stop scintillators
By: miree on Tue, 19 May 2015 14:29
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Re: Position calculations on start/stop scintillators
By: miree on Wed, 20 May 2015 14:13
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Re: Position calculations on start/stop scintillators
By: thuyuk on Thu, 21 May 2015 15:28
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