Cellulose Nitrate Detectors Research Articles

The effect of applied voltage and temperature on growth of copper micro‐ and nanowires in etched ion‐track cellulose nitrate detector

The effects of the applied voltage and temperature on growth of Cu micro- and nanowires electrochemical deposited in the etched ion-track Cellulose Nitrate (CN) detector were investigated. Cellulose Nitrate foils of 96-μm thickness were irradiated with heavy ions (U ions of initial energy 17.7 MeV/nucleon and 16.34 MeV/nucleon). By chemical etching of the latent tracks produced by the heavy ions in CN samples, a porous membrane containing nano- and micro-sized cylindrical open pores were prepared. These porous membranes have been used for fabrication of the nano and microwires. Cu micro- and nanowires were grown by electrochemical deposition of copper into pores using the two-electrode electrochemical cell. The electrochemical deposition process was monitored in real time by recording the current during the growth of the wires. The influence of the deposition parameters such as applied voltage and electrolyte temperature on current versus time curve recorded during the manufacturing of Cu microwires and their structure were studied.

Radon Measurements in Soils along the Coast of Accra from Teshie to Nyanyano, Southeastern Ghana

A study has been undertaken along the coast of Accra (Teshie to Nyanyano) in the Greater Accra Metropolitan Area to investigate the emission of soil radon gas in the area using Lenin Resin (LR) 115 cellulose nitrate detectors. Twenty seven sampling points were considered for the investigation. A set of detectors were buried at a time and were replaced fortnightly for a period of 2 weeks. Three exposures were made at each location. Due to logistics constraints, the detectors were buried in phases over a period of 15 weeks. After the exposure period, the detectors were etched, air dried in the laboratory and the registered alpha tracks were counted using the Spark counter. The track density was calculated and the radon gas concentration was computed. The radon concentrations ranged from 1.40 kBqm -3 to 282.87 kBqm -3 for the period of monitoring. The average soil radon concentration measured during the period of the survey was 24.41 kBqm -3 . Local earthquakes of magnitude ranging from 1.1 to 2.8 on the Richter scale were recorded during the study. Continuous monitoring of the gas could confirm high emanation with the activity of the coastal boundary fault. DOI: http://dx.doi.org/10.5755/j01.erem.71.2.7063

Interpretation of the bulk etching process in LR-115 detectors by the many-hit model

The formalism of the many-hit model (MHM) [Fromm, M., Awad, E.M., Ditlov, V.A., 2004. Many-hit model calculation for track etch rate in CR-39 SSNTD using confocal microscope data. Nucl. Instr. Phys. Res. B 26, 565–575; Ditlov, V.A., Awad, E.M., Fromm, M., Hermsdorf, D., 2005. The Bragg-peak studies in CR-39 SSNTD on the basis of many-hit model for track etch rates. Radiat. Meas. 40, 249–254] is applied in order to describe the bulk etching rate V B of non-irradiated polymer detectors. In such a case the etching process should be easier to understand in terms of interactions of physical and chemical processes superimposing material diffusion and reaction kinetics. In a paper [Ditlov, V.A., 2005. Formation model of bulk etching rate for polymer detectors. Radiat. Meas. 40, 240–248] first attempts have been made to develop formulae for the calculation of V B dependence on the concentration C and temperature T of the etchant solution. Therein, it is shown that V B have to be studied in a broad range of C and T including very low and very high values. The formulae of the MHM contain some free adjustable parameters of definite physical meaning, which have to be determined by fitting the experimental data. In the present paper data for V B of LR-115 cellulose nitrate detectors have been analysed to decide on the reliability of the modelling of etching processes and to determine possible physical-based parameters.

Track etch velocity and chemical damages induced by ions in a cellulose nitrate detector

We sum up here the results obtained on a cellulose nitrate detector (LR 115). LR 115 was irradiated with ions from proton and oxygen ions in the energy range 1–10 MeV/amu. Each irradiated sample consisted of a stack of several detectors (about 20–30) each 12 μ m thick. So chemical damages were studied according to the energy lost in each detector. Broken bonds were identified and quantified using infrared spectroscopy. In the same time we develop the same approach as proposed by Katz R. for the nuclear emulsion response. This approach is based on the hit theory, where the hits are produced by the secondary electrons removed by the incoming ion. Using this approach, neglecting any differences in the initial electron energy spectra and in the temporal aspect of energy deposition, it is surprising to simulate, with the very same parameters, the chemical cross sections from protons and oxygen ions.

Fast neutron irradiation effects on CN-85 solid state nuclear track detector

Samples from cellulose nitrate (CN-85) sheets of 0.3 mm thickness were irradiated with fast neutrons with equivalent doses in the range 1–10 Sv. The effect of fast neutron irradiation on the thermal properties of CN-85 has been investigated using thermo-gravimetric analysis (TGA) and differential thermo-gravimetric (DTG). The onset temperature of decomposition T o and thermal activation energy of decomposition E a were calculated. The results indicate that the cellulose nitrate detector decomposes, in one main breakdown stage, at temperatures much lower than that of several other SSNTDs due to the weak nitrogen oxygen bonds. Also, the variation of transition temperatures with the equivalent neutron dose has been determined using differential thermal analysis (DTA). The results indicate that the CN-85 thermograms were characterized by the appearance of one endothermic peak due to melting. These melting temperatures were found to be dependent on the equivalent neutron dose. In addition, the effect of both temperature and neutron dose on the intrinsic viscosity of the liquid CN-85 samples were studied. The results indicate that the cellulose nitrate polymer does not have a high resistance to degradation possessed by several other SSNTDs.

Field comparison of two different passive radon detectors

The present paper describes field performance of two different passive radon monitor devices formed, respectively, by a CR-39 track detector enclosed in a diffusion chamber and a cellulose nitrate detector (LR-115) in a heat-sealed polyethylene bag. The most important scope of these investigations was to study the performance of these detectors directly in the field. To this end, two different types of radon monitors mentioned above have been exposed simultaneously in 100 school rooms within the Italian region Friuli Venezia Giulia. Finally, the accuracy of their responses has been evaluated by exposing them under extreme humidity conditions and/or together with other radon measurement instruments.

Chemical bond scission induced by 1H +, 16O 8+, and γ-rays in a cellulose nitrate detector (O-082)

Chemical damages induced by γ-rays ( 60Co), proton and oxygen ions in a cellulose nitrate detector (LR115) were quantified by infra-red spectrometry. The linear relationship between chemical damages and parameters like dose, ion fluence and LET proves that similar radiation chemistry occurs for those different exposures and that the chemical damages can not be described with a Poisson law.

Intrinsic efficiency of LR-115 in alpha particles detection: simulations and experiments

A numerical simulation is developed to characterize the response of the cellulose nitrate detector “LR-115 type II” to alpha particles of different incidence angles and energies. It permits to know whether an alpha particle at a given energy and direction is able to produce a visible etched track or not. For this purpose, a V t-variable track etch rate model is used. We have considered that the track etch rate is a function of the ionization rate and the defect created by delta rays along the alpha particle trajectory. Validation of the model is presented in the form of comparisons between theoretically computed values of the sensitive energy range and the track diameters and experimentally determined ones.

Experimental study on the aging process of the LR 115 cellulose nitrate radon detector

An experimental determination of the aging process of cellulose nitrate detector material was based on the examination of special properties of the LR 115 solid state nuclear track detectors (SSNTDs) of various ages up to 18 years. The examined relevant parameters are the bulk etching rate v b and the track etching rate v t. These parameters are responsible for the appearance, the size and the registration efficiency of tracks of α-particles from radon gas in the detector. To find a correlation between these material parameters and the detector sensitivity an experimental calibration of indoor room and outdoor soil detector devices based on LR 115 took place at the Umweltforschungszentrum Leipzig-Halle (Germany). To avoid routine calibration work in external radon exposure facilities a correction of the age dependent calibration factors with the material parameters measured in one's own laboratory was targeted. In this study a general age dependence, however, was not found. The following statements for practical applications can be made. (i) the bulk etching rate v b for detectors of the same batch has a depth dependence and this dependence is constant over 2 years (LR 115 September 1994). (ii) detectors of different batches older than 5 years and stored at room temperature show an odd v b behaviour when v b is used for describing track shapes. (iii) the calibration factor of detectors of different batches that were stored at about +4°C is constant over 5 years (LR 115 September 1994 and February 1999, Table 2). The conclusion is that LR 115 detectors not older than 5 years and stored in a refrigerator at about +4°C should be preferred for radon measurements. Furthermore these detectors should be recalibrated every year and the microscope work of this calibrations should be performed by the same person who performs the measurements. In addition, a phenomenon related to fundamental track formation mechanisms was found, that the time straggling of the time t through when vertical tracks penetrate the 12 μm thick detector layer is independent of the age of the detectors and the energy of the α-particle at the detector surface.

Observation of nuclear track in organic material by Atomic Force microscopy in real time during etching

The developments of Atomic Force Microscopy (AFM) allow to investigated solid surfaces with a nanometer scale. These techniques are useful methods allowing direct observation of surface morphologies. Particularly in the nuclear track fields, they offer a new tool to give many new informations on track formation. In this paper we present the preliminary results of a new use of this technique to characterize continuously the formation of the revealed track in a cellulose nitrate detector (LR115) after an alpha particle irradiation. For that, a specific cell has been used to observe, by nano-observations, the evolution of track shapes simultaneously with chemical treatment. Thus, the track shape evolution has been studied; visualizing the evolution of the tracks in real time, in situ during the chemical etching process.

Quantitative α-particle detection in a homogeneous medium with LR115

Agreement between theoretical and experimental track densities in LR115 cellulose nitrate detectors shows that α-particles can be detected quantitatively in air, solutions, and finely divided solids. For general use, a readily applicable form of the numerically integrated track registration equation for LR115 contact autoradiography is presented.

Track fading and track regrowth in cellulose nitrate SSNTD

Isothermal post-irradiation annealing at room temperature, i.e. practical fading of alpha particle tracks in cellulose nitrate (CN) detectors has been studied. It is found that the fading process, by itself, lasts about a month. Thereafter the registration efficiency is stabilized and holds constant for about ten days. Then a new process begins which was not observed earlier for CN-detectors. This new process-growing has time boundaries too and lasts 1–2 months. On its completion the registration efficiency becomes equal to the initial value. Experimental data obtained in 1990–1993 on fading and growing of alpha particle tracks are presented in this paper for a long-term storage of irradiated detectors. Mathematical description of the dependence obtained is given for two processes—fading and growing, and some facts elucidating the nature of this effect are considered.

Radon activity concentration in the ground and its correlation with the water content of the soil

Radon activity concentration in the ground was measured using Kodak LR-115 cellulose nitrate detectors for approx. 3 yr as part of a survey of exposure to radiation from radon and its decay products. The results show seasonal periodicity with a maximum (summer) to minimum (winter) ratio of the order of 10. The amount of water stored in the soil was deduced from meteorological data on the basis of the water balance of the region. The minima in water content were correlated to maxima in radon concentration resulting in a correlation coefficient of 0.76.

An apparatus complex for radon measurements and calibrations

An apparatus complex is developed for measurements of radon volume activityby the track method. The equipment has been attested at the D.I. Mendeleev All-Russia Research Institute of Metrology, and is intended for mass scale usage. The complex has passive track radiometers of radon based on cellulose nitrate detectors, a spark counter of the type “AIST-2V”, a thermostating etching device, as well as a calibration radon rack “KARST”.

Investigative techniques for radon level characterization

Radon concentration measurements can be used for numerous applications in earth sciences and as an indicator of health risks in radioprotection. In this paper, two techniques for in situ radon level characterisation are presented: a proportional counter (active) and solid state nuclear track detectors (passive). A new development of the proportional counter has been performed. This electronic device measures radon concentrations in soil, ground water or the atmosphere on a continuous basis. Different parameters such as temperature and atmospheric pressure can also be measured during the radon detection process. Results are stored in an associated data processor. A special cell using a cellulose nitrate detector (LR115, Kodak France) has been developed for the passive technique. The response of these detectors, including the influence of the device's polyethylene membrane (used to wrap the cell to protect the detectors from humidity and thoron exposure) on diffusing radon toward the detection cell, has been modeled.

Determination of microquantities of Be in samples using α-sensitive track etch detectors

A new technique of determining Be content in samples using 4.6∸6 MeV γ-rays is proposed. This energy range is sufficient to knock out the neutron from the 9Be nucleaus and to excite the first 2.9 MeV level of the 8Be nuclei. 1.5 MeV alpha particles are registered by means of CR-39 or cellulose nitrate detectors. Alpha particles produced in the reaction of γ-rays with Li nuclei which are contained in samples may cause the background. The latter is excluded by heating of samples before irradiation for Li molecules to be evaporated. 11B nuclei do not produce alpha particles at the energy range of γ-rays presented above. The results obtained in the experiments of determining Be content in natural beryl crystal samples are in good agreement with their known chemical composition. Microparticles containing Beryllium were found in soil samples from the Ust-Kamenogorsk are deposit region, which contains 10 −3 − 10 −4 g/g of Be. The sensitivity of the method is 10 −6 g/g of Be in solids.

Use of radiometer with cellulose nitrate detector (CND) in indoor radon measurements in Omsk, 1993

Detection properties of Russian - made CNDs (Pereslavl-Zalesskiy) were examined experimentally. The detectors were etched for 100 minutes in 5N NaOH at 50° C, without stirring. The tracks developed were read out with a spark counter against a permanent 70±20 tr/cm 2 background. The sensitivity of the radiometer is 0.7± 0.2 tr/cm 2 per 1 kBq·h·m −3. In 1993, our radiometers were used when measuriing radon indoors in Omsk. Among 132 measurements made, only one exceeded a 400 Bq ∗m −3 radon activity level.

DC conductivity and dielectric constant of cellulose nitrate detector

The temperature dependence of DC conductivity as well as the temperature and frequency dependence of dielectric constant of cellulose nitrate (CN) track detector was undertaken for better understanding of the track response of the detector. In the temperature range −100° to + 100°C, CN is found to be an insulating semiconductor with activation energies 0.04 eV, 0.78 eV and 1.24 eV. The transition of the activation processes takes place at (−10±1)°C and (60±1)°C. The high activation energy transition temperature coincides with the glass transition temperature of CN. The dielectric constant is found to increase with temperature and decrease with frequency. These results reveal the physical basis of the Ion Explosion Spike model of Fleischer et al. (1975). A possible explanation of the registration temperature effect is also given on the basis of these results.

Application of track detectors for alpha-activity measurement of soil, water and the surfaces of objects in the 30-km zone of the Chernobyl NPP

Cellulose nitrate detectors and spark-counters for nuclear track counting were used to measure the alpha-activity of soil, water and the surfaces of objects in the 30-km region of the Chernobyl Nuclear Power Plant (NPP) in 1986 and 1990. The equipment, method and calibration experiments are described. The data obtained are compared with the results of radiometric measurements and radiochemical analysis. It is shown that the method used is a convenient and reliable means for large-scale measurements of alpha-nuclide contamination.

Growth rates of the ferromanganese nodules obtained by the cellulose nitrate detector LR-115

Nine pelagic ferromanganese nodules from the South-Eastern Pacific have been analyzed by the alpha-radiography technique using the nitrate cellulose detector LR-115 (type 1). The obtained distributions of the total alpha-radioactivity characterize the growth processes in the recent time. The surface rinds of the nodules accumulated at 1–16 mm/Ma, a value which is in the normal range for deep-sea nodules from this region. Some nodules have been analyzed along two different radial directions which have rather different rates of accretion.