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Abstract This paper discusses an instrument intercomparison performed in the high-energy field at the CERF facility at CERN between 2015 and 2017 (October 2015, May 2016, November 2016 and June 2017). Measurements were performed in several reference exposure locations with the CERN extended-range Bonner Sphere Spectrometer (BSS), a Berthold LB4611, the LINUS rem counter from CERN, the LUPIN rem counter from ELSE Nuclear, the FHT 762 Wide Energy Neutron Detection Instrument (WENDI-II) from Thermo Scientific, the LUDLUM MODEL 42–41 PRESCILA NEUTRON PROBE and two models of Tissue-equivalent proportional counters (TEPCs) from Far West Technologies. All results are compared with the latest FLUKA reference values from simulations performed in 2017. Highlights • The BSS , WENDI II, LINUS and LUPIN agree amongst them and with the FLUKA simulations within one sigma of uncertainty. • The LB6411 underestimates up to 35% as compared to FLUKA and the extended rem counters. • The PRESCILA overestimates the high-energy component and underestimate the evaporation part. Therefore, the PRESCILA overestimates the H*(10) on the CT and underestimates it on the IT. • Concerning the two TEPC , they agree within their range of uncertainty for all positions. The agreement with FLUKA is satisfactory on the CT/CS but the TEPCs show underestimation on the IT. [ABSTRACT FROM AUTHOR]

Neutron spectrometry measurements with an extended-range Bonner Sphere Spectrometer (BSS), as well as neutron H*(10) measurements using an extended-range rem meter WENDI-2, a conventional rem meter LB 6411 and a tissue-equivalent proportional counter, were performed inside and around the Fixed-Beam Treatment Room at the proton therapy facility of Essen, in Germany. The WENDI-2 stood out as the easiest detector for making accurate neutron H*(10) measurements, since its direct measurements were equivalent to the H*(10) rates obtained with the BSS. The measurements were also compared to simulation results obtained with MCNPX 2.7.0 using two different selections of physics models for the hadron interactions above 150 MeV: the Bertini & Dresner models and the CEM03 model. For neutron H*(10) rates outside the treatment room, factors of 1.6–1.8 were obtained between the results of the two simulations, the Bertini & Dresner models yielding the largest values in all positions. The comparison of the simulation results with the WENDI-2 and BSS measurements for positions inside the treatment room showed that the Bertini & Dresner models reproduce the global neutron production in the water phantom relatively well, whereas the CEM03 model underestimates it by a factor of ∼1.3. At the most-forward angle, however, the Bertini model (unlike the CEM03 model) seemed to overestimate the production of neutrons with energies above 100 MeV. Outside the shielding, the simulated H*(10) overestimated the WENDI-2 measurements by factors of 2–3 with the Bertini & Dresner models, and 1.1–1.7 with the CEM03 model. Both simulations were thus conservative with respect to the neutron fluxes transmitted through the concrete walls. This conservative behaviour is probably caused by a combination of several uncertainties, including for instance uncertainties on the proton and neutron interaction cross-sections and uncertainties on the concrete composition and density. [ABSTRACT FROM AUTHOR]

Tissue equivalent proportional counters (TEPCs) can be used as radiation monitors in different radiation environments, including on board of a spacecraft or aircraft. Usually, the gas density of the counter is set to simulate site sizes of 1 μm or 2 μm. However, especially for sealed counters which should be operative for long time without being refilled, the gas density inside the counter could change significantly. The immediate consequence of density variations is a gas gain shift. This in turn is not a serious problem, because the gas gain can be measured and corrected by increasing the bias voltage. A more critical consequence of an increase of the density is that the shape of the microdosimetric spectrum changes, affecting the response of the detector. Consequently, this limits the reliability of sealed TEPC over time, especially because the gas pressure is not directly monitored. Therefore, the aim of this study is to propose an experimental procedure to estimate the TEPC sensitive-site size by performing two independent measurements, one in a gamma radiation field and the other one in a neutron field. The results show that it is possible to assess the site size of sealed TEPCs with an accuracy of 5%. [ABSTRACT FROM AUTHOR]

Abstract: In the past few years, miniaturized tissue-equivalent gas detectors (mini TEPCs) have been developed for application of microdosimetry in radiotherapy. These mini-TEPCs are characterised by millimetric dimensions. They are equipped neither with an internal calibration source nor with electric field tubes, which would properly define the sensitive volume hence the simulated site size. In spite of these lacks, mini TEPCs working in gas flow conditions have proven to be precise and reliable detectors. However, for future therapeutic plans including microdosimetric data, consistency between experimental and calculated data is important. Existing general-purpose Monte Carlo codes have proven to be very useful to calculate the energy deposition due to ionization in macroscopic targets, even in various complex radiation fields. However, theoretical models implemented in these codes for simulating electron transport and straggling are valid only for energies above a few keV. This restricts their applicability for simulating radiation transport at a micrometric level, where low-energy electrons play a dominant role. In this work, we calculate frequency distributions of deposited energy in a mini TEPC (with sizes equivalent to 1 and 2 μm) due to photons using the Monte Carlo code FLUKA. Comparisons between simulated and experimental data show a rather good agreement. Differences due to different FLUKA settings are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Cosmic ray dosimetry measurements were carried out on board a Global Express business jet operated by TAG Aviation (UK) during a pole-to-pole flight sequence that took place in November 2008. One Hawk TEPC and two EPDN2s were flown, and the TEPC measurements compared to calculated values from the route dose codes AVIDOS, CARI 6M, EPCARD versions 3.2 and 3.34, QARM and SIEVERT (online version). The largest difference between measured and calculated doses for the total flight sequence was found to be 13%. Agreement between the readings of the TEPC and the EPDN2s (once a calibration factor from the CERN High Energy Reference Field had been applied) was reasonably good given the relatively large uncertainties associated with the EPDN2 measurements. [ABSTRACT FROM AUTHOR]

Abstract: In 2007, the European Space Agency (ESA) initiated the development of European Crew Personal Active Dosimeters. The hardware development objective is to produce an active personal dosimeter which shows absorbed dose and dose equivalent spectra similar to a Tissue Equivalent Proportional Counter (TEPC), but which is based on more robust silicon detector devices. Several detector/dosimeter components have been investigated – by computer simulations – for their performance in the radiation field at the ISS position. [ABSTRACT FROM AUTHOR]

Abstract: In this study we investigate the dependence of the sensitivity of a TEPC upon its surface area and demonstrate that a compact multi-element tissue equivalent proportional counter (METEPC) has a counting sensitivity comparable to a commercially available 12.7 cm (5 inch) diameter spherical TEPC. The METEPC incorporates 61 cylindrical counting volumes of internal diameter of 0.5 cm and height 5 cm, machined in a single block of tissue equivalent plastic. It is the simplest design available in the multi-element geometrical configuration and is approximately nine times smaller in volume than that of a conventional 12.7 cm spherical TEPC. The neutron sensitivity of commercially available TEPCs and the METEPC simulating a 2 μm tissue site size was examined experimentally using the McMaster University 1.25 MV double stage Tandetron accelerator, which produces low energy neutrons via the 7Li(p, n)7Be reaction. The mean energy of the neutron beams produced ranged from 34 keV to 354 keV. The results presented in this study suggests that the compact METEPC is able to produce measurements in low dose rate radiation environments with the same precision in a given length of time as could be obtained with a 12.7 cm diameter spherical TEPC. [ABSTRACT FROM AUTHOR]

Abstract: Monte Carlo simulations of heavy ion interactions using the Geant4 toolkit were compared with measurements of energy deposition in a spherical tissue-equivalent proportional counter (TEPC). A spherical cavity with a physical diameter of 12.7mm was filled with propane-based tissue-equivalent gas surrounded by a wall of A-150 tissue-equivalent plastic that was 2.54mm to thick. Measurements and Monte Carlo simulations were used to record the energy deposition and the trajectory of the incident particle on an event-by-event basis for ions ranging in atomic number from 2 (4He) to 26 (56Fe) and in energy from 200MeV/nucleon to 1000MeV/nucleon. In the simulations, tracking of secondary electrons was terminated when the range of an electron was below a specified threshold. The effects of range cuts for electrons at 0.5μm, 1μm, 10μm, and 100μm were evaluated. To simulate an energy deposition influenced by large numbers of low energy electrons with large transverse momentum, it was necessary to track electrons down to range cuts of 10μm or less. The Geant4 simulated data closely matched the measured data acquired using a TEPC for incident particles traversing the center of the detector as well as near the gas-wall interface. Values of frequency mean lineal energy and dose mean lineal energy were within 8% of the measured data. The production of secondary particles in the aluminum vacuum chamber had no effect on the response of the TEPC for 56Fe at 1000MeV/nucleon. The results of this study confirm that Geant4 can simulate patterns of energy deposition for existing microdosimeters and is valuable for improving the design of a new generation of detectors used for space dosimetry and for characterizing particle beams used in hadron radiotherapy. [Copyright &y& Elsevier]

Abstract: Ambient dose-equivalent results from an in-flight comparison between different tissue-equivalent proportional counters and silicon diode spectrometers from seven European institutes are presented and compared with calculations using the EPCARD computer program. The measurements were performed on 40000 and 32000ft in narrow target areas at latitudes and . Keeping the altitude and geographic position almost constant provided unique conditions for comparisons. The different measuring systems as well as the calculations are in remarkably good agreement, with an average standard deviation in the ambient dose equivalent between 6% and 21%. The ratio between calculated and measured ambient dose-equivalent rates varies between 0.91 and 1.09, with an average of . Nevertheless some systematic differences in the experimentally determined ambient dose equivalent and its low-LET and high-LET components are noticed and discussed. It is concluded that the standard deviation between different instruments can through optimization and harmonization of the calibration procedures be reduced by up to a factor of two. [Copyright &y& Elsevier]

Measurements of the radiation environment inside the Mir space station were performed with a tissue equivalent proportional counter (TEPC) during the Antares mission in 1992, and over a long period following it. Interesting results concerning radiation measurements show (a) the South Atlantic Anomaly crossing, (b) the increase of radiation near the poles, and (c) the effects of solar particle events (the most important one occurring in early November 1992). This data also provides information about the dose and the quality factor of the radiation to which the cosmonauts were exposed during different missions. These data are compared with measurements obtained using a solid state detector. [Copyright &y& Elsevier]

Tissue equivalent proportional counter (TEPC) model HAWK FWAD-3 was used for the evaluation of absorbed dose, dose equivalent rate (Ḣ TEPC) and microdosimetric spectra measured (i) in the mixed radiation fields formed mainly by cosmic rays onboard aircraft during the flights between Mumbai and the Indian station Bharati (Progress air base), two polar flights at Antarctica, and (ii)ground level environmental radiation field at locations situated in three continents, namely Antarctica, Africa and Asia with different latitudes. The study also includes evaluation of absorbed dose rate, dose equivalent rate of cosmic rays and terrestrial radiation using active detectors namely RADEYE-G and BERTHOLD Rem counter. An effort was made to compare the measured dose equivalent rate by TEPC for the commercial flight routes to Antarctica with the values calculated by the software code EPCARD and a good agreement was observed. The 35th expedition to Bharati, Antarctica showed higher values of dose equivalent at the pole (Larsemann Hills region, 69°24′37.60″S, 76°11′01.70″E) than the world average for an evaluation period of six months during summer. • TEPC used for the measurement of absorbed dose, Ḣ TEPC and microdosimetric spectra for the flight routes. • Measurement of absorbed dose, Ḣ TEPC and microdosimetric spectra at locations of three continents including Antarctica. • Analysis of low and high LET components of cosmic ray to absorbed dose at different altitudes. • Comparison of the measured flight route doses were made with the calculated values by the software code EPCARD. [ABSTRACT FROM AUTHOR]