# Precise Photographic Monitoring of MEG II Thin-film Muon Stopping Target Position and Shape

## TL;DR

This paper presents a photographic method for precisely monitoring the position and shape of a thin-film muon stopping target in the MEG II experiment, achieving high accuracy despite challenging conditions.

## Contribution

The paper introduces a novel photographic technique capable of continuous, high-precision monitoring of the target in a high magnetic field and radiation environment.

## Key findings

- Measurement precision of 0.010 mm normal to the film surface.
- Measurement precision of 0.030 mm parallel to the film surface.
- Technique exceeds the precision requirements for MEG II.

## Abstract

We describe and show results of a photographic technique for continuously monitoring the position, orientation, and shape of a thin-film muon stopping target for the MEG II experiment. The measurement is complicated by the target being located in a region with 1.3 T magnetic field, significant radiation and having limited access. The technique achieves a measurement precision of 0.010 mm normal to and 0.030 mm parallel to the film surface, significantly better than required for the MEG II experiment.