Beam loss monitoring with unfolding techniques

M Caresana,M Reginatto,M Ferrarini,M Frosini

doi:10.1140/epjp/s13360-021-01203-7

Abstract

Since the first particle accelerator’s construction in 1931, an exponential spread of these machines occurred worldwide, in different kinds of applications. Nowadays, these are mainly used for industrial (60%) and medical (35%) purposes and for scientific research (5%). High energy secondary mixed fields produced by the particle beams interaction with matter imply a complex environmental dosimetry and special radiation protection regulations able to guarantee workers and population safety. In the medical field, this aspect is particularly emphasized in hadrontherapy centres, where high energy charged particles such as protons and carbon ions modify environmental doses, with a significant increase in the neutron contribution. This work proposes a technique to identify points of losses of the primary particle beam around an acceleration ring and has been developed within the radiation protection section at the National Centre for Oncological Hadrontherapy situated in Pavia. In the first part, the radiation field produced by protons and carbon ions interactions with structural materials at different energies was investigated. The main instrument of analysis is the Monte Carlo code for particle transport FLUKA, supported by experimental measurements in the treatment room carried out with the rem counter LUPIN, designed for pulsed neutron fields dosimetry. This first step allowed an analysis of both the angular and energetic instrumental response and a comparison of experimental results with simulations. The second part proposes a description of the technique for beam loss positions reconstruction around the acceleration ring at CNAO based on the application of unfolding codes.

Highlights

This work proposes a technique to identify points of losses of the primary particle beam around an acceleration ring and has been developed within the radiation protection section at the National Centre for Oncological Hadrontherapy situated in Pavia
The secondary radiation burst generated by a single beam loss is measured at a few fixed positions around the accelerator and the beam loss position is identified by unfolding these data with GRAVEL [9,10], an unfolding program based on an iterative algorithm that is commonly used for Bonner sphere spectrometry data
In order to evaluate the instrumentation response at different angles and energies, associated with mixed fields produced by particle beam interactions with the structural materials, a series of FLUKA simulations have been performed

Summary

Introduction

The secondary radiation burst generated by a single beam loss is measured at a few fixed positions around the accelerator and the beam loss position is identified by unfolding these data with GRAVEL [9,10], an unfolding program based on an iterative algorithm that is commonly used for Bonner sphere spectrometry data. The advantage of this technique is to greatly reduce the number of BLMs deployed along the acceleration ring

Objectives

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Results

Conclusion