Description: Available online 29 December 2012 Publication year: 2012 Source: Radiation Measurements This study describes the application of two in-house developed dosimeters, the Dose Magnifying Glass (DMG) and the MOS kin dosimeter at the Centre for Medical Radiation Physics, University of Wollongong, Australia, for the measurement of CT dose profiles for a clinical diagnostic 16-slice MSCT scanner. Two scanner modes were used; axial mode and helical mode, and the effect of varying beam collimation and pitch was studied. With an increase in beam collimation in axial mode and an increase of CT pitch in helical mode, cumulative point dose at scanner isocentre decreased while FWHM increased. There was generally good agreement to within 3% between the acquired dose profiles obtained by the DMG and the film except at dose profile tails, where film over-responded by up to 30% due to its intrinsic depth dose dependence at low doses. Highlights ▶ This study shows the CT beam profiles acquired with our institution’s detectors. ▶ The DMG is a relative dosimeter calibrated to absolute MOS kin readings. ▶ There was good agreement between dose profiles acquired by the DMG and the film.

Description: Available online 28 December 2012 Publication year: 2012 Source: Radiation Measurements A polyvinyl butyral film incorporating a radiochromic leuco crystal violet dye (LCV) and a UV-absorber of tinuvin-P has been investigated as a high-dose dosimetry for 60 Co radiation processing in the dose range of 1-100 kGy. Upon γ-ray exposure, the prepared film undergoes visual color change to deep purple color characterized with an absorption band peaking at 594 nm with a shoulder around 552 nm. The response of films stored in dark place at room temperature overall a period of 55 days exhibited good stability, that the increase in response of irradiated and unirradiated films did not exceed 2% and 4%, respectively overall this storage period. The results indicate that no further protection of films from laboratory fluorescent light during the measurement of irradiated film is required. The effect of temperature and relative humidity on the performance of film during irradiation and the overall uncertainty associated with absorbed dose monitoring were investigated in the present study. Highlights ► Preparation of PVB film dosimeter incorporating a radiochromic leucocrystal violet dye for use in routine processing dosimetry. ► The dosimeter useful dose range is 1-100 kGy. ► The response is not markedly dependent on humidity during irradiation in the range of 53-75%. ► The response of unirradiated and irradiated film is good stable during storage period of 55 days. ► Overall uncertainty of the dosimeter did not exceed 7% at 2σ.

Description: Available online 27 December 2012 Publication year: 2012 Source: Radiation Measurements In mixed neutron/γ radiation fields, particle identification based on different filter algorithms and radiation intensities is an important issue for liquid scintillation neutron spectrometry. We have compared the performance of three algorithms for digital neutron/γ discrimination in a deuterated liquid scintillator. The effects of both digital filters and simulated pile-up events on the performance of these techniques were investigated. The discrimination methods utilized are the digital charge comparison (CC) method, simplified digital charge collection (SDCC) method and pulse gradient analysis (PGA) method. The results show that the SDCC and the CC methods are preferred choices when applied in low count-rates fields, whereas PGA method with a seven-point average running filter is favorable when pile-up signals constitute a large fraction of the detected events. All these discrimination approaches are potentially suitable for developing a compact digital neutron spectrometer in mixed neutron/γ radiation fields for use in various applications. Highlights ► We describe three digital n/γ discrimination algorithms. ► Effects of both digital filters and simulated pile-up events were studied. ► The CC and SDCC algorithms are preferred in low count-rates fields. ► The PGA algorithm with a digital filter is favorable in high count-rates fields.

Description: Available online 26 December 2012 Publication year: 2012 Source: Radiation Measurements Estimation of soil-radon activity, Q was first carried out for faults in Central Mongolia. Eight study sites were located in epicentral zones of Mogod (M = 7.8; 05 January1967) and Avdar (M = 3.8; 22 March 2009) earthquakes, and in the vicinity of Ulaanbaatar, where small seismic events (M = 1.0–2.5) occurred in the past few years. Profile radon surveys were conducted at fifteen faults that differ in size and geodynamic activity, yet clearly topographically manifested as scarps or straightened segments of valleys of ephemeral streams. By applying the formalized method of processing of the survey results, it was possible to reveal radon anomalies and to establish that their shape, intensity and contrast are mainly determined by the structure of the fault zone. Due to heterogeneous permeability of fault zones, shapes and quantitative parameters of radon anomalies are variable at different faults and in individual cross-sections of one and the same fracture. Radon anomalies in Central Mongolia are diverse, yet the most frequent are the cases where (1) a radon anomaly is discontinuous in shape due to the presence of small domains with minimum values ​​of Q ; (2) a major part of the anomaly is located in one fault wall; and (3) a fault scarp is marked by a minimum value of Q . In Central Mongolia, intensities of radon anomalies, Q max near neotectonic faults differ by more than an order of magnitude. The most intense anomaly (20,200 Bq/m 3 ) is registered at Hustai fault in the vicinity of Ulaanbaatar, which indicates the importance of assessment of radon hazard for the capital city of Mongolia, where almost half the population of the country reside. The contrast of radon anomaly, К Q is determines as a ratio of a maximum value of Q max to a minimum value of Q min outside the fault zone; it varies from 1.4 to 17.3 for faults of Central Mongolia. Faults characterized by ultra-high ( K Q 〉10), high (10≥ K Q 〉5), increased (5≥ K Q 〉3), medium (3≥ K Q 〉2) and low ( K Q ≤2) radon activity are distinguished. A relative index, K Q can be effectively applied for assessment of geodynamic activity of faults in Central Mongolia. On the one hand, it correlates with sizes and seismic potential of the studied faults; on the other hand, it significantly reduces the complicating influence of regional factors, such as radioactivity of rocks, sediment thickness, meteorological conditions of measurements, etc. The application of К Q , the formalized method of detection of radon anomalies, long-distance base cross-sections, and reduction of the measurement interval near faults - these key features of the profile survey are recommendable for further more accurate estimations on the basis of the first measurements of soil-radon activity in Central Mongolia. Highlights ► Soil-radon activity for the first time is estimated for neotectonic faults in Central Mongolia. ► The main parameters and types of fault radon anomalies are established. ► It is shown, that a radon activity of faults is caused by its geodynamic activity.

Description: Available online 26 December 2012 Publication year: 2012 Source: Radiation Measurements α-Al 2 O 3 :C phosphor was studied for improvement of its dose threshold using thermally assisted optically stimulated luminescence(TA-OSL) phenomenon. The dose threshold of phosphor depends on the standard deviation of the background signal which affects the signal to noise ratio of the instrument. In case of OSL measurement, the background signal is due the scattering of the stimulation light intensity from the planchet. On reducing the stimulation light intensity, the scattering component and thus the standard deviation of the background signal reduces considerably. The reduction in stimulation light intensity increases the readout time due to the dependence of decay constant of OSL signal on the former. The decay constant depends on the photoionization cross-section of the OSL active traps in the phosphor participating in OSL phenomenon and thus on the readout temperature due to the temperature dependence of photoionization cross-section. In order to achieve the same decay constant for two sets of measurements for α-Al 2 O 3 :C i.e. to take the OSL measurement in the same time at lower stimulation light intensity as that taken for higher light intensity, the temperature of measurement for α-Al 2 O 3 :C for the former was raised. Moreover, the increase of readout temperature does not affect the standard deviation in the background signal of OSL readout. The optimized elevated temperature for α-Al 2 O 3 :C was found to be 85oC as the main dosimetric peak starts giving signal due to depletion of its filled traps, at temperatures higher than 90 oC. As a result of lowering the stimulation intensity at higher temperature (85oC), the standard deviation in the background signal and thus the overall dose threshold of α-Al 2 O 3 :C was found to improve by 1.8 times. Highlights ► Method of improvement in dose threshold of α-Al2O3:C is suggested using TA-OSL technique. ► The overall dose threshold of α-Al2O3:C was found to be improved by 1.8 times. ► The temperature dependence of photoionization cross-section on the decay constant has been discussed. ► The method can be applied to other phosphors also to improve dose threshold.

Description: Available online 23 December 2012 Publication year: 2012 Source: Radiation Measurements

Description: Available online 21 December 2012 Publication year: 2012 Source: Radiation Measurements Radon concentration levels were measured in the soil and indoors of Jerash city using time-integrated passive radon dosimeters enclosing CR-39 solid-state nuclear track detectors (SSNTDs). The city was divided into five sectors over which four hundred dosimeters were distributed randomly; one hundred dosimeters were installed into soil and the rest were distributed indoors. The study revealed that radon concentration in soil ranges from 0.98 to 3.05kBq/m 3 with an average of 2.29kBq/m 3 . Indoors radon concentration measurements versus floor elevation showed that the maximum concentration was in the basement and decreases gradually for upper floors. A considerable variation in concentration levels for the same floor in the different sectors was noticed and attributed to the difference in the type of the soil of each sector. Results showed that soil and indoors radon concentration are strongly related for the same area of study. In general, it is found that the average indoor radon concentration in Jerash city is 49.21 Bq/m 3 . The measured radon levels are within the globally accepted values and no unusual concentrations were observed. Highlights ► The average soil radon concentration is 2.29kBq/m 3 and for indoor radon 49Bq/m 3 . ► Radon levels as a function of the elevation in dwellings was measured. ► The old Roman city in Jerash revealed a relatively high level of radon.

Description: Available online 20 December 2012 Publication year: 2012 Source: Radiation Measurements Proton-recoil detectors offer the possibility to unfold fast-neutron energy spectra of various sources. However, quantifying the confidence of the unfolding methodology is a complex task. In this paper, we present a comparative analysis of the maximum-likelihood, expectation-maximization (MLEM) method and one-step-late (OSL) method for neutron energy spectra unfolding. The analysis is performed on Monte Carlo simulated data for several monoenergetic neutron sources and continuous-in-energy 252 Cf, 241 Am-Be and 241 Am-Li neutron sources. The results obtained for the monoenergetic neutron spectra show that both unfolding methods provide results that are in good agreement with the reference data. Very good agreement between the unfolded and the reference data is achieved for 252 Cf, 241 Am-Be, and 241 Am-Li neutron spectra by using the OSL method. In the paper it is demonstrated that the MLEM and OSL methods can be applied to accurately unfold the simulated pulse-height distributions for organic liquid scintillation detectors. Comparative analysis between the two unfolding methods has shown that the OSL method has superior unfolding performance than the MLEM method. Highlights ► Proton-recoil detectors offer the possibility to unfold fast-neutron energy spectra. ► Pulse height distributions simulated by the MCNP-Polimi code. ► Maximum-Likelihood Expectation Maximization (MLEM), one-step-late (OSL) methods. ► Unfolding of monoenergetic and continuous-in-energy neutron sources. ► Study has shown the OSL method has superior unfolding performance to the MLEM method.

Description: Available online 20 December 2012 Publication year: 2012 Source: Radiation Measurements With the cosmic radiation exposure at altitude in 2009 being at a relative high intensity due to the current position in the 11 year solar cycle, a year-long study of Air Canada pilots was undertaken. The empirical Predictive Code for Aircrew radiation exposure (PCAire) along with corresponding in-flight measurements were used to estimate their exposures from flight data and crew rosters continually provided by Air Canada. Almost all of the pilots studied received more than the annual general public limit of 1 mSv, with the majority receiving around 3 mSv and none exceeded the recommended intervention level of 6 mSv. The highest route exposures were found to be on flights from Canada to Asia, Europe and the Southern hemisphere. The routes with the highest dose rates were to Europe and the long haul flights over Canada and the northern USA, a result of the distortion of the vertical cutoff rigidity from the magnetic North Pole’s location in Canada. Although altitude, geomagnetic latitude and flight time are contributing factors to the exposures to the pilots on each route, Canada’s unique geomagnetic location indicated a need to assess Canadian aircrew over their careers. Highlights ► Air Canada pilots were surveyed for cosmic radiation exposure for one year. ▶ The semi-empirical code, PCAire, was utilized to conduct this survey. ► This survey allowed for a realistic and practical assessment of aircrew exposure. ► Both measurements and survey results were comparable and as expected. ► The results are conservative due to the 2009 radiation peak in the solar cycle

Description: Available online 20 December 2012 Publication year: 2012 Source: Radiation Measurements Hydroxyethylammonium (L) tartrate monohydrate (HEALT) single crystals were grown by slow evaporation solution growth method and irradiated at room temperature with 100MeV oxygen and 200MeV gold ions. The powder X-ray diffraction study shows that the title crystal has undergone lattice disorder after irradiation. UV-Visible study reveals that there is a decrease in band gap values on irradiation. The scanning electron and atomic force micrograph discloses the defects which was formed due to irradiation. The unirradiated as well as irradiated crystals were characterized by photoluminescence. Further dielectric and Vickers microhardness measurements were studied for oxygen and gold ions irradiated crystals and compared with pristine HEALT single crystals. Highlights ► The title crystal was irradiated with oxygen and gold ions for the first time. ► The effects due to irradiation were studied using characterization techniques. ► The AFM and SEM study reveals the formation of defects after irradiation. ► The crystal has undergone amorphization after irradiation.