The neutron dose equivalent rate measurements by R3DR/R2 spectrometers on the international space station.

The data from two Bulgarian-German instruments with the basic name "Radiation Risk Radiometer-Dosimeter" (R3D) are discussed. The R3DR instrument worked inside the ESA EXPOSE-R facility (2009-2010), while R3DR2 worked inside the ESA EXPOSE-R2 facility (2014-2016). Both were outside the Russian Zvezda module on the International Space Station (ISS). The data from both instruments were used for calculation of the neutron dose equivalent rate. Similar data, obtained by the Russian "BTNNEUTRON" instrument on the ISS are used to benchmark the R3DR/R2 neutron dose equivalent rate. The analisys reveals that the "BTNNEUTRON" and R3DR/R2 values are comparable both in the equatorial and in the South Atlantic Anomaly (SAA) regions. The R3DR/R2 values are smaller than the "BTNNEUTRON" values in the high latitude regions. The comparison with the Monte Carlo simulations of the secondary galactic cosmic rays (GCR) neutron ambient dose equivalent rates (El-Jaby and Richardson, 2015, 2016) also shows a good coincidence with the R3DR/R2 spectrometer data obtained in the equatorial and high latitude regions.

Neutron dose assessment in laser-generated ultra-short pulsed fields.

ELI Beamlines is one of the pillars of the Extreme Light Infrastructure European Research Infrastructure Consortium (ELI ERIC), the European project aiming at building the next generation of high power lasers for fundamental research and industrial applications. Several high-power lasers are hosted by the ELI Beamlines facility. Even at a power lower than the nominal one, when interacting with a target, the laser can generate mixed ionizing radiation fields of unique nature. One of the major laser systems, High-repetition-rate advanced petawatt laser system (HAPLS) was already used in commissioning experiments. Detecting the neutrons generated during these experiments has been a challenging task, since certain difficulties were faced. First, the experimental conditions were frequently altered during the commissioning phase (such as laser beam parameters, experimental geometry or target type). Next, the extremely short duration of the ionizing radiation pulse generated by the laser (~10-14 s) complicated the correct interpretation of the data provided by the detectors designed and calibrated in standard fields. Here, one commissioning experiment is described, together with the means of addressing the problem of the detection of the ionizing radiation and the lessons learned in this endeavour.

Latitudinal effect on the position of Regener-Pfotzer maximum investigated by balloon flight HEMERA 2019 in Sweden and balloon flights FIK in Czechia.

When primary space radiation particles enter into the atmosphere of the Earth, they generate showers of secondary radiation. The intensity of secondary radiation reaches its maximum, called the Regener-Pfotzer maximum; its exact position depends on the geomagnetic effective vertical cut-off rigidity, the phase of the solar cycle and also on the type of detected particles. In this paper, several balloon flight experiments are described focusing on the study of the latitudinal effect on the position of the Regener-Pfotzer maximum. Altitude profile of ionization in the atmosphere was measured using radiation detectors flown during several flights at locations with different effective vertical cut-off rigidities (flight HEMERA over Sweden and flights FIK-5 and FIK-6 over Czech Republic). The measured results are supplemented also with simulations using EXPACS 4.11 and the variation of obtained positions of Regener-Pfotzer maximum is discussed.

Simulation and experimental verification of ambient neutron doses in a pencil beam scanning proton therapy room as a function of treatment plan parameters.

Out-of-field patient doses in proton therapy are dominated by neutrons. Currently, they are not taken into account by treatment planning systems. There is an increasing need to include out-of-field doses in the dose calculation, especially when treating children, pregnant patients, and patients with implants. In response to this demand, this work presents the first steps towards a tool for the prediction of out-of-field neutron doses in pencil beam scanning proton therapy facilities. As a first step, a general Monte Carlo radiation transport model for simulation of out-of-field neutron doses was set up and successfully verified by comparison of simulated and measured ambient neutron dose equivalent and neutron fluence energy spectra around a solid water phantom irradiated with a variation of different treatment plan parameters. Simulations with the verified model enabled a detailed study of the variation of the neutron ambient dose equivalent with field size, range, modulation width, use of a range shifter, and position inside the treatment room. For future work, it is planned to use this verified model to simulate out-of-field neutron doses inside the phantom and to verify the simulation results by comparison with previous in-phantom measurement campaigns. Eventually, these verified simulations will be used to build a library and a corresponding tool to allow assessment of out-of-field neutron doses at pencil beam scanning proton therapy facilities.

Monte Carlo simulation of semiconductor-based detector in mixed radiation field in the atmosphere.

Calculation of radiation protection quantities in tissue equivalent material from measurements using semiconductor detectors requires correction factors for conversion of the measured values in the semiconductor material to the tissue equivalent material. This approach has been used many times in aircraft and for space dosimetry. In this paper, we present the results of Monte Carlo simulations which reveal the need to take into account both the radiation field and the detector material when performing the conversion of measured values to radiation protection quantities. It is shown that for low Z target material, most of the dose equivalent at aviation altitudes comes from neutrons originating from nuclear reactions, while in high Z targets most of the dose equivalent comes from photons, originating from electromagnetic reactions.

Neutron Radiation Dose Measurements in a Scanning Proton Therapy Room: Can Parents Remain Near Their Children During Treatment?

Purpose: This study aims to characterize the neutron radiation field inside a scanning proton therapy treatment room including the impact of different pediatric patient sizes. Materials and Methods: Working Group 9 of the European Radiation Dosimetry Group (EURADOS) has performed a comprehensive measurement campaign to measure neutron ambient dose equivalent, H*(10), at eight different positions around 1-, 5-, and 10-year-old pediatric anthropomorphic phantoms irradiated with a simulated brain tumor treatment. Several active detector systems were used. Results: The neutron dose mapping within the gantry room showed that H*(10) values significantly decreased with distance and angular deviation with respect to the beam axis. A maximum value of about 19.5 µSv/Gy was measured along the beam axis at 1 m from the isocenter for a 10-year-old pediatric phantom at 270° gantry angle. A minimum value of 0.1 µSv/Gy was measured at a distance of 2.25 m perpendicular to the beam axis for a 1-year-old pediatric phantom at 140° gantry angle.The H*(10) dependence on the size of the pediatric patient was observed. At 270° gantry position, the measured neutron H*(10) values for the 10-year-old pediatric phantom were up to 20% higher than those measured for the 5-year-old and up to 410% higher than for the 1-year-old phantom, respectively. Conclusions: Using active neutron detectors, secondary neutron mapping was performed to characterize the neutron field generated during proton therapy of pediatric patients. It is shown that the neutron ambient dose equivalent H*(10) significantly decreases with distance and angle with respect to the beam axis. It is reported that the total neutron exposure of a person staying at a position perpendicular to the beam axis at a distance greater than 2 m from the isocenter remains well below the dose limit of 1 mSv per year for the general public (recommended by the International Commission on Radiological Protection) during the entire treatment course with a target dose of up to 60 Gy. This comprehensive analysis is key for general neutron shielding issues, for example, the safe operation of anesthetic equipment. However, it also enables the evaluation of whether it is safe for parents to remain near their children during treatment to bring them comfort. Currently, radiation protection protocols prohibit the occupancy of the treatment room during beam delivery.

MEASUREMENT OF THE REGENER-PFOTZER MAXIMUM USING DIFFERENT TYPES OF IONISING RADIATION DETECTORS AND A NEW TELEMETRY SYSTEM TF-ATMON.

Stratospheric balloons are a useful tool for the investigation of cosmic radiation at high altitudes and the tests of new detectors of cosmic radiation. Due to necessary data processing, the balloon gondola needs to carry, together with radiation detectors, additional supplementary sensors measuring humidity, temperature, location and orientation, altitude, atmospheric pressure, acceleration, etc. A newly developed universal system TF-ATMON, based on using already existing tools of the PX4 open-source project, enables apart from data recording and monitoring, also the possibility to trace the balloon gondola after the flight. The application was demonstrated on stratospheric balloon flight FIK-6. This flight was unique because three different types of radiation detectors were used at one flight. It enabled us to compare the altitude of the Regener-Pfotzer maximum measured with different types of sensors sensitive to a different type of secondary cosmic radiation generated in the atmosphere.

CALIBRATION OF SILICON DETECTORS LIULIN AND AIRDOS USING COSMIC RAYS AND TIMEPIX FOR USE AT FLIGHT ALTITUDES.

Silicon detectors such as Liulin and AIRDOS are used for cosmic radiation measurements onboard aircraft. These measurements can be used for the verification of computer programs assessing aircraft crew radiation exposure. Recently performed intercomparison flights showed large variances of absorbed doses among individual detectors and significant differences between results of silicon detectors and computer programs. In order to explain for these differences, we have developed energy calibration method that can be performed on short flights. The method is based on cross-calibration of Liulin and AIRDOS deposited energy spectra with deposited energy spectra measured by Timepix which has superior detection properties in terms of energy resolution and the detection threshold. Moreover, the portion of dose which is omitted due to low sensitivity for low-energy deposits was calculated. The resulting absorbed dose rates at two intercomparison flights show significantly improved variation of results and better agreement with modelled absorbed dose rates.

CHARACTERISATION OF AIRDOS-C DETECTOR FOR MEASUREMENT OF HIGH-ENERGY EVENTS IN THE ATMOSPHERE.

At the flight altitudes of modern airplanes, cosmic rays intensity is several times higher than on the Earth's surface. The radiation field is not constant in time and due to various effects, not routinely considered in calculations, the exposure can increase several times. Therefore, a continuous monitoring of radiation exposure on board is required. This article characterises newly developed detectors Airdos-C with diverse scintillation crystals. Unlike detectors based on a Si diode, which are commonly used for long-term measurements, these detectors can also be used for detection of high-energy gamma-rays generated in thunderstorms. For a correct interpretation of the measured data it is important to perform an energy calibration and to verify the detector response in known radiation fields. The results obtained with several radionuclide sources were analysed using mathematical statistics methods. The detectors were also exposed onboard aircraft under well-defined conditions.

SPACEDOS: AN OPEN-SOURCE PIN DIODE DOSEMETER FOR APPLICATIONS IN SPACE.

A new Open-Source dosemeter, SPACEDOS, has been developed for measurements of cosmic radiation on board spacecraft and small satellites. Its main advantages are that it is small and lightweight with low power consumption. It can be adjusted for specific applications, e.g. used in pressurized cabins of spacecraft or in vacuum environments in CubeSats or larger satellites. The open-source design enables better portability and reproduction of the results than other similar detectors. The detector has already successfully performed measurements on board the International Space Station. The obtained results are discussed and compared with those measured with thermoluminescent detectors located in the same position as SPACEDOS.

VERTICAL DOSIMETRIC MEASUREMENT OF ELECTRIC DISCHARGE INDUCED AT LIGHTNING IMPULSE VOLTAGE GENERATOR.

This paper deals with the measurement of ionising radiation emitted in the vertical field of electric discharge generated between the tip and the grounded plate electrode. The generator set-up was for 400 consecutive negative discharges with voltage amplitude 0.9 MV, waveform shape 1.2/50 $\mu $s, discharge energy 80 kJ and electrodes 1 m apart. Thermoluminescent, passive detectors were used to avoid electromagnetic interference from the discharge. The detectors were placed at the electrodes and three vertical positions 1 m from the discharge axis. This work extends a previous study focused on dosimetry in the plane parallel to the ground. This experiment confirmed the presence of a photon/electron component at the electrode tip and 0.5 m vertical position at a distance of 1 m from the discharge axis. In addition, the presence of neutrons was found for new positions in the vertical axis and the ground electrode.

SPECTROMETRY OF HIGH-ENERGY PHOTONS ON HIGH MOUNTAIN OBSERVATORY LOMNICKÝ STÍT DURING THUNDERSTORMS.

Lomnický stít, Slovakia, 2634 m above sea level, is known to be a place of extreme electric fields measured during thunderstorms and is thus a suitable place for thunderstorm-related ionising radiation research. We present one of the strongest Thunderstorm ground enhancements (TGE) ever detected, which occurred on 12 September 2021. The TGE was detected with the SEVAN detector and also with the new Georadis RT-56 large volume gamma spectrometer. In the paper, we present spectra of the TGE measured with the spectrometer as well as SEVAN coincidence data supplemented by the data from electric field mill.

INVESTIGATION OF NUCLEAR EMULSIONS IN TERMS OF NEUTRON DOSIMETRY.

Neutron detection using nuclear emulsions can offer an alternative in personal dosimetry. The production of emulsions and their quality have to be well controlled with respect to their application in dosimetry. Nuclear emulsions consist mainly of gelatin and silver halide. Gelatin contains a significant amount of hydrogen, which can be used for fast neutron detection. The addition of B-10 in the emulsion is convenient for thermal neutron detection. In this paper, standard nuclear emulsions BR-2 and nuclear emulsions BR-2 enriched with boron produced at the Slavich Company, Russia, were applied for evaluation of fast and thermal neutron fluences. The results were obtained by calculation from the presumed emulsion composition without prior calibration. Evidence that nuclear emulsions used in the experiment are suitable for neutron dosimetry is provided.

CR10-A PUBLIC DATABASE OF COSMIC RADIATION MEASUREMENTS AT AVIATION ALTITUDES OF ABOUT 10 KM.

Long-term measurements using silicon radiation spectrometer Liulin on board commercial aircraft have been performed since 2001; results were put into a new database, which covers more than 4500 flights with more than 130 000 measurements. Methodology and tools were developed to normalize the data with respect to latitude and altitude and thus enable comparison with other radiation detectors and with model calculations. This capability is demonstrated using data from the neutron monitor at Lomnický stít. Instead of providing data files for individual measurement period, two software solutions are delivered. First is a web-based user interface for visualizing and downloading arbitrary time window of interest from the database hosted at http://cr10.odz.ujf.cas.cz. The second is a set of interactive Python notebooks available at GitHub. Those implement the calibration, normalization and visualization methods-so the outputs can be tailored to user needs. The software and data are provided under GNU/CC license.

OVERVIEW OF AIRCREW EXPOSURE TO COSMIC RADIATION IN THE CZECH REPUBLIC.

Monitoring of exposures of aircrew members of airline operators registered in the Czech Republic has been performed since 1998. The individual effective doses are calculated using the computer code CARI annually. The calculations are based on information about participation of aircrew members on the specific flights and on the parameters describing the typical flight profiles of the flights; the latter is regularly verified with control measurements performed onboard aircraft. The results show that (1) the average annual effective doses in the period from 1998 to 2017 range from 1.3 to 2.1 mSv, (2) the maximum effective dose of a crew member is 5.7 mSv and (3) the annual collective effective doses range from 1.3 to 4.1 manSv. Combined relative uncertainty of the results is ~25%.

Optimization of the Timepix chip to measurement of radon, thoron and their progenies.

Radon and thoron as well as their short-lived progenies are decay products of the radium and thorium series decays. They are the most important radionuclide elements with respect to public exposure. To utilize the semiconductor pixel radiation Timepix chip for the measurement of active and real-time alpha particles from radon, thoron and their progenies, it is necessary to check the registration and visualization of the chip. An energy check for radon, thoron and their progenies, as well as for (241)Am and(210)Po sources, was performed using the radon and thoron chambers at NIRS (National Institute of Radiological Sciences). The check found an energy resolution of 200 keV with a 14% efficiency as well as a linear dependency between the channel number (cluster volume) and the energy. The coefficient of determination r(2) of 0.99 for the range of 5 to 9 MeV was calculated. In addition, an offset for specific Timepix configurations between pre-calibration for low energy from 6 to 60 keV, and the actual calibration for alpha particles with energies from 4000 to 9000 keV, was detected.

Comparison of cosmic rays radiation detectors on-board commercial jet aircraft.

Aircrew members and passengers are exposed to increased rates of cosmic radiation on-board commercial jet aircraft. The annual effective doses of crew members often exceed limits for public, thus it is recommended to monitor them. In general, the doses are estimated via various computer codes and in some countries also verified by measurements. This paper describes a comparison of three cosmic rays detectors, namely of the (a) HAWK Tissue Equivalent Proportional Counter; (b) Liulin semiconductor energy deposit spectrometer and (c) TIMEPIX silicon semiconductor pixel detector, exposed to radiation fields on-board commercial Czech Airlines company jet aircraft. Measurements were performed during passenger flights from Prague to Madrid, Oslo, Tbilisi, Yekaterinburg and Almaty, and back in July and August 2011. For all flights, energy deposit spectra and absorbed doses are presented. Measured absorbed dose and dose equivalent are compared with the EPCARD code calculations. Finally, the advantages and disadvantages of all detectors are discussed.

Radiation sources in the environment near NPP Temelin.

A widely discussed question is how much a nuclear power plant really contributes to irradiation of the people living in its vicinity. A number of laboratory and in situ measurements were performed in the area surrounding NPP Temelin, on the basis of which we can specify the irradiation of this area from various sources. The evaluation includes the contributions from natural sources, such as radon, terrestrial radiation and cosmic radiation, together with the contribution from inhalation and ingestion of radionuclides. Medical irradiation and nuclear fallout are also included.