Application of the Beta-ray alignment for the OPERA CSDs

Application of theBeta-ray alignment for the OPER

A CSDs

Seigo Miyamoto

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

At first, division of area (5mm x 5mm)

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.

Some Samples

Some Samples

Some Samples

Some Samples

Some Samples

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

beta-ray alignment summary

Continual area ratio of CSDs

sucessful

sucessful

The reason of below 90%

• Not enough beta-rays to align.

---- 1

• Peak is detected, but double.

---- 5

• Large Gap exists.

---- 1

Examples , Double Peak

Examples , Double Peak

Examples , Double Peak

Examples , Double Peak

Examples , Large Gap is Detected.

Examples , Large Gap is Detected.

Examples , Large Gap is Detected.

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.