Application of the Beta-ray alignment for the OPERA CSDs Seigo Miyamoto
Dec 20, 2015
Beta-ray alignment• New alignment metho
d by using beta-ray from environmental radioactive isotopes.
• Coincidence at contacted emulsion layers.
• Effective to correct the distortion( is essential for good position resolusion) of film by development or drying .
Detection ofposition displacement
peak of beta-ray-Take all combination of dx in ~+-100um
- Angle allowance is FREE.
2.1um 1.8um
If the tightness of packing is enough,
Position displacement of high energy tracks from beta-ray alignment peak (um)
Application for the OPERA CSD
• Alignment accuracy is less than 1um.
• Effective to reject BG tracks very much.
Samples :
Cosmic run events ---- 26 CSDs
Neutrino events ---- 32 CSDs
Procedure
Taking all combinations of MicroTracks in contacted layers,
And Detection of beta-ray alignment peaks in each unit areas.
Position displacement distribution from the X-ray alignment
40 um20um in delta position space
Plot vector as the center of peak in each unit area on the film map -> Relative Distortion map.
Estimation of successful area• Continuity check is suitable which beta-ray alignment is
success or not because distortion should be continual.
-Check the difference of vector between adjacent area.
-For example,
d(dX)(a,b)=dXb-dXa
- if d(dX) < 10umfor >=2 adjacent areas, “a” is defined as continual(successful).
b
a c
d
e
The reason of below 90%
• Not enough beta-rays to align.
---- 1
• Peak is detected, but double.
---- 5
• Large Gap exists.
---- 1
Summary
• Beta-ray alignment was applied to real OPERA Experiment.
• The number of beta-ray for alignment is enough.
• We estimated mechanical tightness. 26/32 CSDs is aligned successfully. 5/32 CSDs have Double Peaks, these are recoverable by detection both (We have 2 alignments, BG Doublet tracks become twice).
1/32 CSD has large (more than 100um) gap, we can detect it.
• We continue the study of these 6 events.