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LYCCA ToF scintillators [message #18548]

Wed, 07 October 2015 10:09

a_boso
Messages: 16
Registered: July 2014

occasional visitor

From: *pd.infn.it

Dear all,

I am trying to use ToF Start scintillator to get position informations.

Looking at the code I saw the possibility to use a "x_shear" parameter, which permits to introduce a "y-dependent" offset on the x position.
Which is the physical meaning of this quantity? How can I optimize it?

More generally, do you know how can I optimize the position information of the Lycca ToF scintillators? Which resolution should I expect?

Last question:

Could you please share the positions of the PMTs you have in the Lycca/Lycca/Membrane.par file for the ToFStart and ToFStop scintillators?
I have more than one set, and I don't know which one is the right one.

Thank you very much!

Alberto

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Re: LYCCA ToF scintillators [message #19423 is a reply to message #18548]

Fri, 12 August 2016 15:35

Michael Reese
Messages: 9
Registered: August 2016

occasional visitor

From: *gsi.de

Hi,

By just plotting the x vs. y position as it comes from the ToF-scintillator, you will get a pattern of squares. The pattern comes from the gaps between the LYCCA modules.
If everything would be perfect, the lines in the pattern should be perpendicular. In practice they might look a bit sheard.
The "x_shear" and "y_shear" parameters are there to correct for that.

I hope the following schematic drawing makes it clear.

index.php?t=getfile&id=8739&private=0

In addition, the pattern might be shifted in x and y direction, and rotated. There are other parameters forseen to correct these errors.

Regards,
Michael

Attachment: shear_correction.png
(Size: 16.72KB, Downloaded 420 times)

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Re: LYCCA ToF scintillators [message #19424 is a reply to message #19423]

Fri, 12 August 2016 16:26

SMilne
Messages: 30
Registered: July 2014
Location: York

continuous participant

From: 5.151.46*

Hi Michael,

Could I please ask how this calibration would likewise be performed for the ToF start scintillator, i.e. where no such lines are present.

Thanks,
Scott

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Re: LYCCA ToF scintillators [message #19425 is a reply to message #19424]

Fri, 12 August 2016 17:20

Michael Reese
Messages: 9
Registered: August 2016

occasional visitor

From: *gsi.de

Hi,

You need to create a pattern artificially. One possible way to do this is to draw a rectangular gate around the projected TPC-position, i.e. the "true" position, and make a gated ToF x:y plot with the condition that the "true" position is inside that gate. You'll see the distorted shape of whatever gate you have drawn.

Reminder of how to create such a rectangular gate in the config file (I didn't test that piece of code... there might be typos inside):

processor ToF_Start/TPC/gate UTILS.ConditionWindow2D
  x  <-  Frs/S4tracking.xs[5]
  y  <-  Frs/S4tracking.ys[5]
  display x:y | xy_window
end

processor ToF_Start/distored UTILS.PairWithCondition
  first  <- Lycca/ToFStart/Membrane.x
  second <- Lycca/ToFStart/Membrane.y
  condition <- ToF_Start/TPC/gate.inside
  display tested_first:tested_second 
end

If you want to have multiple gates, you could do something like this for 6 gates:

for $i in [0:5]
  processor ToF_Start/TPC/gate_$i UTILS.ConditionWindow2D
    x  <-  Frs/S4tracking.xs[5]
    y  <-  Frs/S4tracking.ys[5]
    display x:y | xy_window
  end
end

processor ToF_Start/distored UTILS.PairWithCondition
  first  <- Lycca/ToFStart/Membrane.x
  second <- Lycca/ToFStart/Membrane.y
  for $i in [0:5]
    condition <- ToF_Start/TPC/gate_$i.inside
  end
  display tested_first:tested_second 
end

Then you could draw gates in the shape of horizontal lines, three gates in the shape of vertical lines, and together they'll make a grid-like shape.

[Updated on: Fri, 12 August 2016 17:24]

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Re: LYCCA ToF scintillators [message #19426 is a reply to message #19425]

Fri, 12 August 2016 17:27

Michael Reese
Messages: 9
Registered: August 2016

occasional visitor

From: *gsi.de

I should mention, that all these corrections should be done after the calibration of the PMTs is already optimized.
Calibrated PMTs will already give a good x:y pattern. The offset, rotation, and shear corrections are for fine-tuning the result.

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Re: LYCCA ToF scintillators [message #19427 is a reply to message #19426]

Fri, 12 August 2016 17:32

SMilne
Messages: 30
Registered: July 2014
Location: York

continuous participant

From: 5.151.46*

Hi Michael,

Thanks for your response. I will give it a try and see what I get.

Yeah, the other calibrations are already completed, this was just to try and optimise them a little more.

Thanks,
Scott

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