Characterization of the PTW 34031 ionization chamber (PMI) at RCNP with high energy neutrons ranging from 100 – 392 MeV

Chris Theis ,D Perrin,C Urscheler,L Jaegerhofer,M Widorski,D Forkel-Wirth,K Hatanaka,Noriaki Nakao ,Takashi Nakamura ,Jun Nishiyama ,Tatsuhiko Sato ,Daiki Satoh ,Akihiko Masuda ,Michel Pangallo ,S Roesler,Masayuki Hagiwara ,Hiroshi Iwase ,A Tamii,Shingo Taniguchi ,Pierre Carbonez ,Yoshibumi Nakane ,T Shima,Toshiro Itoga ,Yosuke Iwamoto ,Eduard Feldbaumer ,Helmut Vincke ,Tadao Matsumoto ,Hiroshi Yashima ,Hiroshi Nakashima ,Hideki Harano ,Yukio Sakamoto

doi:10.1051/epjconf/201715308018

Abstract

Radiation monitoring at high energy proton accelerators poses a considerable challenge due to the complexity of the encountered stray radiation fields. These environments comprise a wide variety of different particle types and span from fractions of electron-volts up to several terra electron-volts. As a consequence the use of Monte Carlo simulation programs like FLUKA is indispensable to obtain appropriate field-specific calibration factors. At many locations of the LHC a large contribution to the particle fluence is expected to originate from high-energy neutrons and thus, benchmark experiments with mono-energetic neutron beams are of high importance to verify the aforementioned detector response calculations. This paper summarizes the results of a series of benchmark experiments with quasi mono-energetic neutrons of 100, 140, 200, 250 and 392 MeV that have been carried out at RCNP - Osaka University, during several campaigns between 2006 and 2014.

Highlights

Radiation monitoring at high-energy proton accelerators poses a considerable challenge due to the complexity of the encountered stray radiation fields
At CERN gas-filled ionization chambers are commonly used in such mixed fields as they are sensitive to many different particle types which directly or indirectly cause ionization of the active detection medium
As a consequence the use of Monte Carlo simulation programs like FLUKA (1)(2) is indispensable to study and obtain an appropriate monitor calibration depending on the radiation field (3)

Summary

Introduction

Radiation monitoring at high-energy proton accelerators poses a considerable challenge due to the complexity of the encountered stray radiation fields. At CERN an air-filled ionization chamber under atmospheric pressure PTW-34031, which internally is named PMI and manufactured by PTW, is utilized for the measurement of dose in the LHC experiment caverns during the operation of the machine as well as the determination of the residual dose after the beam has been turned off The response of this monitor to mixed fields has been studied with the help of Monte Carlo simulations as well as experimental benchmarks (5). Among these facilities there is a time of flight (TOF) tunnel of 100 m length which is available for experiments with quasi-mono-energetic neutrons. In order to compare the results all values have been scaled and normalized to the same distance of 18 m using the 1/r2 law

Benchmark experiments at RCNP

Comparison of simulation and measurements

Findings

Conclusion