Instrument intercomparison in the high-energy mixed field at the CERN-EU reference field (CERF) facility

This paper discusses an intercomparison campaign carried out in several locations around the CERN Proton Synchrotron. The locations were selected in order to perform the measurements in different stray field conditions. Various neutron detectors were employed: ionisation chambers, conventional and extended range rem counters, both commercial and prototype ones, including a novel instrument called LUPIN, specifically conceived to work in pulsed fields. The attention was focused on the potential differences in the instrument readings due to dead-time losses that are expected to affect most commercial units. The results show that the ionisation chambers and LUPIN agree well with the expected H*(10) values, as derived from FLUKA simulations, showing no relevant underestimations even in strongly pulsed fields. On the contrary, the dead-time losses of the other rem counters induced an underestimation in pulsed fields that was more important for instruments characterised by a higher dead time.

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“…A detailed description of the detectors as well as of their response functions can be found in refs (4,5).…”

Section: Instrumentationmentioning

confidence: 99%

Comparison of the performance of different instruments in the stray neutron field around the CERN Proton Synchrotron

Aza

Caresana

Cassell

et al. 2013

Radiation Protection Dosimetry

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“…A similar experiment was conducted in 2012 by Caresana et al [14] to investigate the performances of conventional and extended-range rem-counters including a novel instrument called LUPIN, two TEPCs and bubble detectors. The results were also compared with the FLUKA reference values [3].…”

Section: Test Workplace Field Calibration and Intercomparison Of Radmentioning

confidence: 99%

The CERN-EU high-energy Reference Field (CERF) facility: applications and latest developments

Silari

Pozzi

2017

EPJ Web Conf.

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Abstract. The CERF facility at CERN provides an almost unique high-energy workplace reference radiation field for the calibration and test of radiation protection instrumentation employed at high-energy accelerator facilities and for aircraft and space dosimetry. This paper describes the main features of the facility and supplies a non-exhaustive list of recent (as of 2005) applications for which CERF is used. Upgrade work started in 2015 to provide the scientific and industrial communities with a state-of-the-art reference facility is also discussed.

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“…The LUPIN used during the intercomparison allowed the real-time reading of H * (10) with an integration time of 1 s. Therefore, it was possible to reconstruct and analyse H * (10) variations with 1 s time resolution. The detection capabilities of the LUPIN were demonstrated both in terms of response to high-energy neutrons (Caresana et al 2014b, Dinar et al 2018 and in pulsed fields (Aza et al 2014. The LUPIN was chosen as the reference rem-counter in this intercomparison.…”

Section: Lupinmentioning

confidence: 99%

Joint EURADOS WG9-WG11 rem-counter intercomparison in a Mevion S250i proton therapy facility with Hyperscan pulsed synchrocyclotron

et al. 2022

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Objective Proton therapy is gaining popularity because of the improved dose delivery over conventional radiation therapy. The secondary dose to healthy tissues is dominated by secondary neutrons. Commercial rem-counters are valuable instruments for the on-line assessment of neutron ambient dose equivalent (H*(10)). In general, however, a priori knowledge of the type of facility and of the radiation field is required for the proper choice of any survey meter. The novel Mevion S250i Hyperscan synchrocyclotron mounts the accelerator directly on the gantry. It provides a scanned 227 MeV proton beam, delivered in pulses with a pulse width of 10 µs at 750 Hz frequency, which is afterwards degraded in energy by a range shifter modulator system. This environment is particularly challenging for commercial rem-counters; therefore, we tested the reliability of some of the most widespread rem-counters to understand their limits in the Mevion S250i stray neutron field. Approach This work, promoted by the European Radiation Dosimetry Group (EURADOS), describes a rem-counter intercomparison at the Maastro Proton Therapy centre in the Netherlands, which houses the novel Mevion S250i Hyperscan system. Several rem-counters were employed in the intercomparison (LUPIN, LINUS, WENDI-II, LB6411, NM2B-458, NM2B-495Pb), which included simulation of a patient treatment protocol employing a water tank phantom. The outcomes of the experiment were compared with models and data from the literature. Main results We found that only the LUPIN allowed for a correct assessment of H*(10) within a 20% uncertainty. All other rem-counters underestimated the reference H*(10) by factors from 2 to more than 10, depending on the detector model and on the neutron dose per pulse. In pulsed fields, the neutron dose per pulse is a fundamental parameter, while the average neutron dose rate is a secondary quantity. An average 150-200 µSv/GyRBE neutron H*(10) at various positions around the phantom and at distances between 186 cm and 300 cm from it was measured per unit therapeutic dose delivered to the target. Significance Our results are partially in line with results obtained at similar Mevion facilities employing passive energy modulation. Comparisons with facilities employing active energy modulation confirmed that the neutron H*(10) can increase up to more than a factor of 10 when passive energy modulation is employed. The challenging environment of the Mevion stray neutron field requires the use of specific rem-counters sensitive to high-energy neutrons (up to a few hundred MeV) and specifically designed to withstand pulsed neutron fields.

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Instrument intercomparison in the high-energy mixed field at the CERN-EU reference field (CERF) facility

Cited by 10 publications

References 18 publications

Comparison of the performance of different instruments in the stray neutron field around the CERN Proton Synchrotron

Comparison of the performance of different instruments in the stray neutron field around the CERN Proton Synchrotron

The CERN-EU high-energy Reference Field (CERF) facility: applications and latest developments

Joint EURADOS WG9-WG11 rem-counter intercomparison in a Mevion S250i proton therapy facility with Hyperscan pulsed synchrocyclotron

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