Intercomparison of radiation protection instrumentation in a pulsed neutron field

Caresana, M.; Denker, A.; Esposito, A.; Ferrarini, M.; Golnik, N.; Hohmann, Eike; Leuschner, A.; Luszik-Bhadra, M.; Manessi, Giacomo Paolo; Mayer, Sabine; Ott, K.; Röhrich, J.; Silari, M.; Trompier, F.; Volnhals, M.; Wieluński, M.

doi:10.1016/j.nima.2013.11.073

Cited by 43 publications

(33 citation statements)

References 25 publications

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“…D half depends only on the detector and the values used here were taken, when possible, from the values given in ref. [2]; k depends on the weight of the scattered component of the field; A describes the decreasing weight of the scattered part of the field as the value of H*(10) per burst increases.…”

Section: Discussionmentioning

confidence: 99%

“…The effectiveness of the fitting equation needs to be further verified, as it has been applied only to the data acquired in this experiment and, by imposing k = 0, to the data obtained in the HZB experiment [2]. Other systematic studies conducted to test the response of detectors in PNF do not seem to be present in the literature.…”

Section: Discussionmentioning

confidence: 99%

“…However, an attempt was made to find a fit that was more physically meaningful. Caresana et al [2] formulated a method to fit the data obtained in a similar experiment at the Helmholtz Zentrum Berlin (HZB). The fitting equation expressed the transition between the linear and the saturation region via a parameter called D half , typical of each detector, i.e.…”

Section: Fitting Equationmentioning

confidence: 99%

“…The values of D half used for the fitting were the same as the ones found in the HZB experiment [2] since they are dependent on the type of detector used and not on the field characteristics. Figure 25 shows the difference between the fitting equations (1) and (2) applied to a set of Biorem data.…”

Section: Fitting Equationmentioning

confidence: 99%

“…the diminution of the gas multiplication factor of proportional counters during the detection of a neutron burst [1] and volume recombination effects for ionization chambers. A comprehensive study focused on the evaluation of the behaviour of active neutron detectors in PNF has been recently carried out by Caresana et al [2]. This paper presents and discusses the results of a similar experiment conducted at the High Radiation to Materials (HiRadMat) facility at CERN [3], with a different set of detectors and under different conditions.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Instrument intercomparison in the pulsed neutron fields at the CERN HiRadMat facility

Aza¹,

Caresana²,

Cassell³

et al. 2014

Radiation Measurements

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Fitting Equationmentioning

confidence: 99%

Section: Fitting Equationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Instrument intercomparison in the pulsed neutron fields at the CERN HiRadMat facility

Aza¹,

Caresana²,

Cassell³

et al. 2014

Radiation Measurements

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Shielding verification and neutron dose evaluation of the Mevion S250 proton therapy unit

Prusator

Ahmad

Chen

2018

J Applied Clin Med Phys

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For passive scattering proton therapy systems, neutron contamination is the main concern both from an occupational and patient safety perspective. The Mevion S250 compact proton therapy system is the first of its kind, offering an in‐room cyclotron design which prompts more concern for shielding assessment. The purpose of this study was to accomplish an in‐depth evaluation of both the shielding design and in‐room neutron production at our facility using both Monte Carlo simulation and measurement. We found that the shielding in place at our facility is adequate, with simulated annual neutron ambient dose equivalents at 30 cm outside wall/door perimeter ranging from background to 0.07 mSv and measured dose equivalents ranging from background to 0.06 mSv. The in‐room measurements reveal that the H*/D decreases when the distance from isocenter and field size increases. Furthermore, the H*/D generally increases when the angle around isocenter increases. Our results from in‐room measurements show consistent trends with our Monte Carlo model of the Mevion system.

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Radiation shielding and safety implications following linac conversion to an electron FLASH‐RT unit

et al. 2021

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Purpose Due to their finite range, electrons are typically ignored when calculating shielding requirements in megavoltage energy linear accelerator vaults. However, the assumption that 16 MeV electrons need not be considered does not hold when operated at FLASH‐RT dose rates (~200× clinical dose rate), where dose rate from bremsstrahlung photons is an order of magnitude higher than that from an 18 MV beam for which shielding was designed. We investigate the shielding and radiation protection impact of converting a Varian 21EX linac to FLASH‐RT dose rates. Methods We performed a radiation survey in all occupied areas using a Fluke Biomedical Inovision 451P survey meter and a Wide Energy Neutron Detection Instrument (Wendi)‐2 FHT 762 neutron detector. The dose rate from activated linac components following a 1.8‐min FLASH‐RT delivery was also measured. Results When operated at a gantry angle of 180° such as during biology experiments, the 16 MeV FLASH‐RT electrons deliver ~10 µSv/h in the controlled areas and 780 µSv/h in the uncontrolled areas, which is above the 20 µSv in any 1‐h USNRC limit. However, to exceed 20 µSv, the unit must be operated continuously for 92 s, which corresponds in this bunker and FLASH‐RT beam to a 3180 Gy workload at isocenter, which would be unfeasible to deliver within that timeframe due to experimental logistics. While beam steering and dosimetry activities can require workloads of that magnitude, during these activities, the gantry is positioned at 0° and the dose rate in the uncontrolled area becomes undetectable. Likewise, neutron activation of linac components can reach 25 µSv/h near the isocenter following FLASH‐RT delivery, but dissipates within minutes, and total doses within an hour are below 20 µSv. Conclusion Bremsstrahlung photons created by a 16 MeV FLASH‐RT electron beam resulted in consequential dose rates in controlled and uncontrolled areas, and from activated linac components in the vault. While our linac vault shielding proved sufficient, other investigators would be prudent to confirm the adequacy of their radiation safety program, particularly if operating in vaults designed for 6 MV.

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Intercomparison of radiation protection instrumentation in a pulsed neutron field

Cited by 43 publications

References 25 publications

Instrument intercomparison in the pulsed neutron fields at the CERN HiRadMat facility

Instrument intercomparison in the pulsed neutron fields at the CERN HiRadMat facility

Shielding verification and neutron dose evaluation of the Mevion S250 proton therapy unit

Radiation shielding and safety implications following linac conversion to an electron FLASH‐RT unit

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