Measurement of indoor radon levels in Erbil capital by using solid state nuclear track detectors

Radon alpha activity concentration has been measured in 28 homes in the Erbil Capital-Iraqi Kurdistan region during the autumn season by using time-integrated passive radon dosimeters containing CR-39 solid state nuclear track detectors “SSNTDs”. The radon activity concentrations in these homes range from (10.33–90.34) with an average of . The average absorption effective dose equivalent for a person living in homes for which the investigation were done was found to be , obtained by using an equilibrium factor of 0.5 and an occupancy factor of 0.8. The average lung cancer cases per year per 10⁶ person was found to be 23±12.     

Investigation of free radicals induced by light ions in CR-39 using ESR spectroscopy

In previous investigations the formation of radicals induced by γ-irradiation in CR-39 samples has been studied by electron spin resonance (ESR) spectroscopy. On the other hand, all attempts fail to detect radicals in samples irradiated by particles (p, and neutrons). The present work succeeded in detection of radicals produced by charged particle radiation in CR-39 (TASTRAK). The detectors were irradiated with protons of 7 MeV and -particles of 3 MeV with fluences in the order of 10¹¹–10¹² particles/cm². The observed ESR signal is composed of at least four different resonance lines for each of which we determined the amplitudes, g-factors, lifetimes and the G-value. The amplitude of the total ESR signal decreases rapidly with a short and a longer lifetime. About 5 days after irradiation the ESR intensity decreased to an undetectable value. The lowest detectable dose (LDD) is of the order of 1 kGy.     

Measurement of neutron fluence with CR-39 using a UV spectrophotometer

Measurement of the correct neutron fluence in various energy intervals in and around the neutron sources is important for the purpose of personnel and environmental neutron dosimetry. In the present paper we present a method for the measurement of neutron fluence using a CR-39 plastic track detector. The samples exposed to fission neutrons from a reactor with 10¹²– fluence and to fast neutrons from a ²⁴¹Am–Be source with a fluence of were etched for 14 time intervals starting from 10 to 570 min in 6 N NaOH at . The etched samples were exposed to the monochromatic light signal from an iodine–tungsten lamp and the transmittance was measured after each etching time interval using a UV Spectrophotometer. An exponential decay of the transmittance has been observed with increasing etching time. The behaviour of the fission neutrons having four different values of fluence has been observed to be distinctly different from that of the fast neutrons. It has also been observed that there is a linear relationship between the transmittance decay constant and fission neutron fluence.     

Flux and energy distribution of axial protons emitted from the hydrogen plasma focus

Experimental results and theoretical studies show that protons from the hydrogen plasma focus are emitted predominantly in the axial direction. In this work the results of the flux and energy distribution measurements of the axial protons using CR-39 detector are presented. The main purpose of the experiment is to test the suitability of a plasma focus device as a source for (p,) nuclear reactions, especially and .     

An extensive indoor Rn/Rn monitoring in North-East India

The behaviour of ubiquitous radon (), thoron () and their progeny in the indoor atmosphere generally reflect a complex interplay between a number of processes, the most important of which are radioactive -decay, ventilation, attachment to aerosols and deposition on the surfaces. The present work involved a long-term (1997–2000) passive monitoring of and in the indoor environment of the North-Eastern region of India. This region being a zone of high seismicity, the indoor radon and thoron measurement of the region will provide a better insight and a valuable database for any study related to radon and thoron anomalies.     

Alpha-recoil track densities in mica and radiometric age determination

Recoiling daughters of -decaying U and Th impurities in mica and other minerals produce localised lattice damage: alpha-recoil tracks. The age of a sample can be calculated from the number of tracks per unit volume (N_ART). To this end, the mica is etched and the etch pits at the sites of recoil-tracks are counted under the optical microscope. Because the measured track densities increase with etching time, N_ART is calculated from the fitted regression line. A number of problems inherent in this approach are overcome by the etch–anneal–etch and the mirror-image methods. The track densities determined with these methods are independent of etching time. Although both methods need improvement, they hold the potential of a precise determination of N_ART from a single measurement in future recoil-track dating.     

Studies of UV-cured CR-39 recording properties in view of its applicability in radiobiological experiments with alpha particles

In radiobiology, low doses of high-LET radiation correspond to a few particle traversals through the cell population. Therefore, for studies on cell monolayers irradiated with a low dose of -particles, it is extremely useful if the number and position of particle traversals can be determined. In this study we describe a new method, based on UV-curing, to obtain a thick CR-39 grafted onto a thick PolyEthylene Terephtalate (PET). This thin double polymeric layer, used as a dish base, has a regular and reproducible detector thickness which can be traversed by 3.5 MeV -particles, with a sufficient residual energy to traverse mammalian cells attached to the base. The recording properties of a PET-CR-39 dish, together with a demonstration of its use for radiobiological experiments, are presented. This new tool allows the precise determination of single-track impact parameters at a sub-cellular level.     

Influence of oxygen on the track etch rate along light ion trajectories in CR-39

The role of oxygen for stabilising radicals to form permanent damages in irradiated samples which are basically important for the etching process of track detectors has been studied. Samples of CR-39 were irradiated with 4 MeV -particles with a fluence of 30 000 particles per cm². The irradiations were performed in three different regimes:

• variation of out-gassing time in vacuum before irradiation;

• no out-gassing time but varied post-irradiation storage times in vacuum;

• variation of both storage times in vacuum before and after irradiation.

Generally, the absence of dissolved oxygen in the irradiated sample results in a decreased detection sensitivity in comparison with the detection properties and track parameters of samples irradiated in air. To determine the sensitivity the depth dependence of the track etch rate v_T(x) along the particle trajectory has been measured. From the observation of the dependence of the decreasing sensitivity on the post-irradiation storage time in vacuum, a lifetime of free radicals of 30 min could be derived. The amount of permanent damages responsible for the etching mechanism is related to the concentration profile of back-diffused oxygen and the REL-dependent radical concentration. This confirms previous results that the detection sensitivity is not a simple function of REL but depends on both REL and x the stronger the deeper within the irradiated sample.     

Alpha-particle calibration of CR-39 using a beehive collimator

A device to determine the detection efficiency of CR-39 for alpha particles is presented. A beehive collimator restricted the angle of incidence of alpha particles on a CR-39 sheet, such that the total number of alpha emitters could be determined. This makes it possible to obtain the critical angle of incidence, Θ_C, and the maximum angle of incidence resulting in round (diameter ratio <1.100) etch pits, Θ_max. In this work, these angles were determined for incidence energies around 7.5 MeV (more specifically 6.1 and 8.8 MeV).     

A joint UAB-IReS-IPNO neutron comparison exercise with nuclear track detectors

The response of PN3 and CR-39 personal dosemeters with different configurations, developed by the IReS (Strasbourg), the IPNO (Orsay) and the UAB (Barcelona) groups, is investigated in this study. Both dosemeters were mounted on a water-filled phantom and were simultaneously exposed under different incidence angles (0, 30 and 60) to the following: (i) three ISO neutron sources (²⁴¹Am-Be, bare ²⁵²Cf and moderated ²⁵²Cf with Cd shielding), and (ii) two realistic neutron sources (SIGMA and moderated ²⁵²Cf) at the IRSN (Cadarache) facilities. After irradiation, the plastic detectors were etched and evaluated according to local routine procedures and corrections for the effect of source-to-detector distance were taken into account. A comparison of the average background, the minimum detectable dose equivalent and the field calibration factor is performed as well.     

Radiator design for detecting high-energy neutrons with a nuclear track detector

Subsequent to the proposal of a two-layer structured radiator for more efficient detection of high-energy neutrons with a plastic nuclear track detector (PNTD), its availability has been investigated both experimentally and theoretically. An inner deuterized hydrocarbon (CD₂) layer adjacent to PNTD should play the role of both a radiator of deuterons recoiled there and a degrader for energetic protons recoiled in the outer layer of a CH₂ material. It was found that the energy dependence of the efficiency was changed sensitively by the thickness of the CD₂ layer. A best combination of CH₂ and CD₂ thickness was estimated under a condition of a constant total thickness. For example, the sensitivity could be flattened within 20% between about 5 and 70 MeV by using -CD₂ and -CH₂.     

Radon activity and exhalation rates measurements in fly ash from a thermal power plant

Radon exhalation rate from fly ash samples and from the homogeneous mixture of fly ash of different proportions additive in soil and cement samples to study the effect of the addition was measured by cup dosimeter using SSNTDs. Radon activities were found to vary from (1018±38) to ( whereas the radon exhalation rate varied from (366±14) to . A gradual increase has been observed in samples having fly ash as an additive in cement samples whereas a gradual decrease was observed in soil samples after the addition of fly ash. ²³⁸U in fly ash was measured by a low-level NaI (Tl)-based gamma ray spectrometer. The results show enhancement in U concentration in fly ash as compared to coal samples, whereas radon exhalation rate is less in fly ash samples.     

: Hadronic molecules in effective field theory

We consider the implications from the possibility that the recently observed state X(3872) is a meson–antimeson molecule. We write an effective Lagrangian consistent with the heavy-quark and chiral symmetries needed to describe X(3872). We explore the consequences of the assumption that X(3872) is a molecular bound state of D^*0 and mesons for the existence of bound states in the and channels.     

Measuring depths of sub-micron tracks in a CR-39 detector from replicas using Atomic Force Microscopy

One of the challenging tasks in the application of solid-state nuclear track detectors (SSNTDs) is the measurement of the depth of the tracks, in particular, the shallow ones resulting from short etching periods. In the present work, a method is proposed to prepare replicas of tracks from particles in the CR-39 SSNTDs and to measure their heights using atomic force microscopy (AFM). After irradiation, the detectors were etched in a 6.25 N aqueous solution of NaOH maintained at 70 °C. The etched detectors were immersed into a beaker of the replicating fluid, which was placed in a water bath under ultrasonic vibration and maintained at room temperature to facilitate the filling of the etched tracks with the replicating fluid. As an example of application, these results have been used to derive a V function for the CR-39 detectors used in the present study (for the specified etching conditions).     

On localized tachyon condensation in and

We study some aspects of localized tachyon condensation on non-supersymmetric orbifolds of the form C²/Z_n and C³/Z_n. We discuss the gauged linear sigma models for these orbifolds. We show how several features of the decay of orbifolds of C³ can be realised in terms of orbifolds of C².     

Dose distribution of carbon ions in air assessed using imaging plates and ionization chamber

A system to expose biological specimens to medium-energy (2.6–6.0  MeV/u) irradiation has been developed at the NIRS-HIMAC. In order to determine the beam energy or LET at the irradiation position in air, the dose distribution for 6.0  MeV/u carbon beam has been obtained using a secondary electron monitor and a flat-type ionization chamber by using air as the energy absorber. Imaging plates were applied to assess the beam profile distribution. The intensity of photo-stimulated luminescence (PSL) was found to be almost proportional to the energy deposited within the sensitive layer of the imaging plate. It has been confirmed that a uniform irradiation field can be produced (about ±5% within 20 mm in diameter) at low-intensity exposure from 10¹ to . Long-term beam stability in the low-intensity condition has also been demonstrated. As a consequence, the methodology for uniform, stable and low-intensity beam exposure has been established, and the continuously variable linear energy transfer (LET) values have also been obtained by changing the distance from the endcap of beamport, for biological studies.     

Correlators of matrix models on homogeneous spaces

We investigate the correlators of TrA_μA_ν in matrix models on homogeneous spaces: S² and S²×S². Their expectation value is a good order parameter to measure the geometry of the space on which non-commutative gauge theory is realized. They also serve as the Wilson lines which carry the minimum momentum. We develop an efficient procedure to calculate them through 1PI diagrams. We determine the large N scaling behavior of the correlators. The order parameter shows that fuzzy S²×S² acquires a 4-dimensional fractal structure in contrast to fuzzy S². We also find that the two point functions exhibit logarithmic scaling violations.     

Search for Uranium Source in Warcha Sandstone, Salt Range, Pakistan, using SSNTD Technique

The similarity in sedimentary depositional characteristics of the Warcha Sandstone of Nilawahan Group in the Salt Range to the uranium bearing sandstones of Siwalik Group in the foot hills of Himalaya and Sulaiman Ranges, Pakistan, tempted geologists to investigate the former group for the occurrence of uranium deposits in it. Like volcanic ash beds in Siwaliks, phosphatic nodules may be a possible source of uranium mineralization in Warcha Sandstone. Samples of phosphatic nodules occurring in the Warcha sandstone near Chakwal were collected and subjected to the solid state nuclear track detection technique for the determination of their uranium concentration. The uranium concentration in these samples ranges from (434±32) to (964±74) with an average of . The high uranium content indicates that the phosphatic nodules may be the possible source of uranium mineralization in Warcha Sandstone. These results are quite encouraging and favor the idea of exploring the area in detail for any possible occurrence of uranium deposits.     

Angular response of CR-39 to relativistic heavy ions and high-energy protons

Track etch detectors CR-39 irradiated with relativistic heavy ions (C, Ne, Si and Fe, ) and high-energy protons (35–230 MeV) were etched both chemically and electrochemically. To determine an angular dependence of response in detail (step 1), an arrangement of a single detector bent into a semi-cylindrical form was used. Experimental data were fitted by polynomic functions and the detection efficiencies for isotropic irradiation were calculated. Critical angles of registration were also determined for heavy ions. The possible influence of additional absorbers and radiators was also estimated.     

Upgrading of LET track-etch spectrometer calibration: Calibration and uncertainty analysis

The spectrometer of linear energy transfer (LET) was developed several years ago. It is based on the chemically etched polyallyldiglycolcarbonate (PADC) track-etch detector. LET spectra are determined through track parameters determination and analysis by an automatic optical image analyser LUCIA G. For the past few years, we have used three materials, Page, 0.5 mm thick and Tastrak, 1 and 0.5 mm thick. To upgrade and determine their calibration curves, we have performed irradiation in high-energy heavier charged particle beams at Dubna, Russia and at Chiba, Japan. We were able to irradiate detectors by means of particles from ¹²C to ⁵⁶Fe with LET in water from 7.9 to . Upgraded calibration curves were obtained through a regression analysis, including systematic uncertainty estimation. The results obtained were combined with statistical uncertainty treatment and were used to analyse recently and previously obtained data. Examples of the results are presented and analysed.