Thin Mylar Foil Research Articles

Chemical characterization of cement samples by radio-analytical methods namely external (in air) PIGE, INAA and ED-XRF for assessing their quality and method validation of radioanalytical techniques

This paper demonstrates novel application of neutron and proton based nuclear analytical techniques for the rapid evaluation of cement quality in terms of compressive strength using Ca to Si ratios. Preliminary phase characterization was performed using X-ray diffraction patterns. External PIGE method was optimized and applied for direct analysis of “as received” samples in thin mylar foils with reduced turn-around time of analysis. Moreover, Pneumatic Carrier Facility at Dhruva reactor of BARC was utilized for NAA for rapid and short irradiation of samples followed by analysis. Quality control of both NAA and PIGE methods were done using several geological Certified / Standard Reference Materials (CRMs and SRMs). EDXRF was employed as alternative analytical technique for comparative evaluation. Statistical evaluation was performed in terms of t-test and F-tests to understand the reliability of measurement and acceptable variance of the results. Eight cementitious samples were analyzed and their compressive strengths were evaluated using NAA and PIGE.

Stopping power of fission fragments in thin Mylar and nickel foils

The energy loss of heavy ions in thin Mylar and nickel foils was measured accurately using fission fragments from 239Pu(nth,f), mass and energy separated by the Lohengrin separator at ILL. The detection setup, placed at the focal plane of the Lohengrin separator enabled to measure precisely the kinetic energy difference of selected fragments after passing through the sample. From these data, the stopping powers in Mylar and nickel layers were extracted and compared to calculations. Whereas large deviations are observed with SRIM-2013 for Mylar, fairly good agreements are obtained with the semi-empirical approach of Knyazheva et al. (2006) and the calculations contained within the DPASS database. In nickel, SRIM-2013 and Knyazheva model are in agreement with our data within about 10%, while large deviations are observed with DPASS. We used our data to provide updated parameters for the Knyazheva model and rescale DPASS database for nickel and Mylar.

Development and operation of an electrostatic time-of-flight detector for the Rare RI storage Ring

An electrostatic time-of-flight detector named E-MCP has been developed for quick diagnostics of circulating beam and timing measurement in mass spectrometry at the Rare-RI Ring in RIKEN. The E-MCP detector consists of a conversion foil, potential grids, and a microchannel plate. Secondary electrons are released from the surface of the foil when a heavy ion hits it. The electrons are accelerated and deflected by 90∘ toward the microchannel plate by electrostatic potentials. A thin carbon foil and a thin aluminum-coated mylar foil were used as conversion foils. We obtained time resolutions of 69(1) ps and 43(1) ps (standard deviation) for a 84Kr beam at an energy of 170 MeV/u when using the carbon and the aluminum-coated mylar foils, respectively. A detection efficiency of approximately 90% was obtained for both foils. The E-MCP detector equipped with the carbon foil was installed inside the Rare-RI Ring to confirm particle circulation within a demonstration experiment on mass measurements of nuclei around 78Ge produced by in-flight fission of uranium beam at the RI Beam Factory in RIKEN. Periodic time signals from circulating ions were clearly observed. Revolution times for 78Ge, 77Ga, and 76Zn were obtained. The results confirmed successful circulation of the short-lived nuclei inside the Rare-RI Ring.

A unique alpha dosimetry technique using Gafchromic EBT3(®) film and feasibility study for an activity calibrator for alpha-emitting radiopharmaceuticals.

To develop an alpha dosimetry technique for activity calibration of alpha-emitting radiopharmaceuticals using the Gafchromic(®) EBT3 (Gaf-EBT3) radiochromic film (International Speciality product, Wayne, NJ). The Gaf-EBT3 has a tissue equivalent radiosensitive layer (approximately 28 μm) sandwiched between two 100-μm thick polyester sheaths, thereby making it insensitive to alpha particles. We have split a Gaf-EBT3 sheet using a surgical scalpel to remove one of the polyester protective layers and covered the radiosensitive layer with thin Mylar(®) foil (Goodfellow Cambridge Limited, Huntingdon, UK) (2.5 μm). Small pieces of modified film were exposed at contact with a 560-Bq thin (241)Am source for 5, 10, 24 and 94 h. The optical density of the films was evaluated using an optical densitometer. The alpha energy spectra of the (241)Am source were recorded using a Si(Li) surface barrier detector. Time-integrated specific alpha surface activity (kBq cm(-2) h) was represented as a function of optical density. By removing one of the 100 μm thick polyester protective layers, the authors have modified the Gaf-EBT3 film to a sensitive alpha dosemeter. The calibration function relevant to a (241)Am reference source was evaluated from the optical densities of the dosemeter foils. Furthermore, calibration functions for important alpha emitters such as (223)Ra, (225)Ac or (210)Bi were parameterized from the (241)Am reference data. The authors have developed and tested the principle of a clinical alpha dosemeter using Gaf-EBT3 radiochromic films originally developed for photon dosimetry. This novel, user-friendly technique could be implemented in quality assurance and calibration procedures of important alpha-emitting radiopharmaceuticals prior to their clinical applications.

A compact high-resolution elastic recoil detection system for lithium depth profiling

A compact high-resolution elastic recoil detection analysis (ERDA) system was developed for precise Li analysis. 200–400keV He+ ions were used as primary ions and the energy spectra of recoiled Li ions were measured using a magnetic spectrometer. Due to its dispersion the background originating from the scattered primary ions is reduced. The recoiled ions of the substrate other than Li, which may also contribute to the background, were rejected by a thin mylar foil placed in front of a focal plane detector. An electrostatic quadrupole lens was installed at the entrance of the magnetic spectrometer to improve the depth resolution by correcting the effect of the kinematic broadening. The performance of the developed high-resolution ERDA was examined by measuring several samples. A thin Li layer (1.5×1015cm−2) deposited on a graphite surface was clearly observed and the detection limit was estimated to be less than 0.01ML under typical measurement conditions. The depth resolution was estimated to be 0.5nm at the surface and was better than 3nm in the surface region within 5nm from the surface.

Measurements of proton induced γ-ray emission cross sections on MgF2 target in the energy range 1.95–3.05 MeV

In this work we present differential cross sections for γ-ray emission from the reactions 19F(p,p′γ)19F (Eγ=110, 197, 1236 and 1349+1357keV), 24Mg(p,p′γ)24Mg (Eγ=1369keV) and 25Mg(p,p′γ)25Mg (Eγ=390, 585 and 975keV). Differential cross sections were measured for proton energies from 1.95 to 3.05MeV with a 15keV step and beam energy resolution of 0.06%. Thin reference standard, 54.1μg/cm2 of MgF2 deposited on thin Mylar foil with additionally evaporated 4nm Au layer, was used as a target. The γ-rays were detected by a 20% relative efficiency HPGe detector placed at an angle of 135° with respect to the beam direction, while the backscattered protons were collected using silicon surface barrier detector placed at the scattering angle of 165°. Obtained cross sections were compared with the previously measured data available from the literature.

Improvement of sensitivity in high-resolution ERDA

Recently, we have developed a new detector system for a magnetic spectrometer to reduce the background noise in high-resolution Rutherford backscattering spectroscopy. The detector system consists of a MCP detector for ion detection, which has a thin Mylar foil in front of the detector, and an electron detector to detect secondary electrons emitted by the ions upon impact on the Mylar foil. By measuring the ion signal in coincidence with the electron signal, the dark noise of the ion detector can be efficiently rejected. This new detector system is used to improve the sensitivity of high-resolution elastic recoil detection. The detection limit of 0.08 at.% is achieved for the boron depth profiling in Si.

Improvement of sensitivity in high-resolution Rutherford backscattering spectroscopy

The sensitivity (limit of detection) of high-resolution Rutherford backscattering spectroscopy (HRBS) is mainly determined by the background noise of the spectrometer. There are two major origins of the background noise in HRBS, one is the stray ions scattered from the inner wall of the vacuum chamber of the spectrometer and the other is the dark noise of the microchannel plate (MCP) detector which is commonly used as a focal plane detector of the spectrometer in HRBS. In order to reject the stray ions, several barriers are installed inside the spectrometer and a thin Mylar foil is mounted in front of the detector. The dark noise of the MCP detector is rejected by the coincidence measurement with the secondary electrons emitted from the Mylar foil upon the ion passage. After these improvements, the background noise is reduced by a factor of 200 at a maximum. The detection limit can be improved down to 10 ppm for As in Si at a measurement time of 1 h under ideal conditions.

Stopping power measurements for 16O, 19F and 28Si ions in Mylar by a transmission technique

Electronic energy loss of charged particles in materials is a fundamental process responsible for the unique response of materials in applications of advanced nuclear power, radiation detectors and advanced processing of electronic devices. In this study, stopping powers of 16O, 19F and 28Si heavy ions crossing thin Mylar foils have been determined in transmission geometry. The energy loss was measured over a continuous range of energies from 1.6 to 5.5 MeV/n (MeV per nucleon) using the data that was tagged by a surface barrier detector (SBD) with and without stopping foils. We have compared the obtained stopping values to those predicted by SRIM-2008 computer code, ICRU-73 stopping data tables and MSTAR calculations. The effective charge values of these heavy ions have been also deduced from the experimental set of data.

Collection and behaviour of radon progenies on thin Mylar foils

Abstract Thin Mylar foils are often used to protect detectors from contamination. However, these foils can be electrostatically charged, possibly leading to their contamination with airborne radon progenies. In the present work, the collection and behaviour of radon progenies on Mylar foils was investigated in detail using alpha spectrometry. The radon progenies collection rate of a small Mylar foil (3 cm 2 ) is equivalent to an air sampler with a flow rate of approximately 0.1 m 3 /h. It was demonstrated that such contamination may jeopardise the validity of the entire analysis if not interpreted correctly.

Generation of intense proton beams from plastic targets irradiated by an ultraintense laser pulse

Proton beams generated from thin aluminum and Mylar foil targets that are irradiated by a 30fs Ti:sapphire laser pulse with an intensity of 2.2x10;{18}Wcm;{2} were investigated. Protons from the Mylar targets were observed to have an energy higher by a factor of 2 and were higher in number by an order of magnitude as compared with those generated from the aluminum targets. The maximum proton energy of 1.3+/-0.12MeV obtained from the Mylar target was found to be similar with previous observations that used laser pulses with different intensities. To address the anomalous behavior of the maximum proton energy for plastic targets, an acceleration model is proposed. In this model, the protons are accelerated by a resistively induced electric field in the front of the target, which can account for the experimental observations.

A new vacuum component: fast acting puncture valve

Generally, for proton induced X-ray emission (PIXE), external-PIXE, gamma ray spectrometry, charge particle spectrometry or ion beam irradiation in air using large vacuum system like particle accelerator, a thin Mylar or Kapton foil are used as a window material (chamber) for above beams to perform experiments. The problem arises when this thin Mylar or Kapton foil gets destroyed accidentally in mid-run. Air with high velocity rushes inside, which disturbs the inside vacuum of the chamber or beam lines and causes failure of the experimental system. In order to avoid this, one needs a sensitive arrangement, which can sense the rush of air and stop it entering in to the vacuum chamber or lines. The solution to the above problem is achieved by design a new fast acting puncture valve. The valve is working on the basis of differential pressure and the basic underlying principle to sense the rushing air is based on Bernoulli's principle and Pascal's law, which is different from commercially available fast acting valve. The new valve is installed in the External beam line of 3MV tandem pelletron accelerator at Institute of Physics, Bhubaneswar and working fine in both rough as well as high vacuum.

A low-mass neutron flux monitor for the n _TOF facility at CERN

A small-mass system has been developed for monitoring the flux of neutrons with energy up to 1 MeV at the new time-of-flight facility at CERN, n_TOF. The monitor is based on a thin Mylar foil with a 6Li deposit, placed in the neutron beam, and an array of Silicon detectors, placed outside the beam, for detecting the products of the 6Li(n, alpha)³H reaction. The small amount of material on the beam ensures a minimal perturbation of the flux and minimizes the background related to scattered neutrons. Moreover, a further reduction of the gamma-ray background has been obtained by constructing the scattering chamber hosting the device in carbon fibre. A detailed description of the flux monitor is here presented, together with the characteristics of the device, in terms of efficiency, resolution and induced background. The use of the monitor in the measurement of neutron capture cross-sections at n_TOF is discussed

A low background neutron flux monitor for the n_TOF facility at CERN

A small-mass system has been developed for monitoring the flux of neutrons with energy up to 1 MeV at the new time-of-flight facility at CERN, n_TOF. The monitor is based on a thin Mylar foil with a 6Li deposit, placed in the neutron beam, and an array of silicon detectors, placed outside the beam, for detecting the products of the 6Li( n, α) 3H reaction. The small amount of material on the beam ensures a minimal perturbation of the flux and minimizes the background related to scattered neutrons. Moreover, a further reduction of the γ-ray background has been obtained by constructing the scattering chamber hosting the device in carbon fibre. A detailed description of the flux monitor is here presented, together with the characteristics of the device, in terms of efficiency, resolution and induced background. The use of the monitor in the measurement of neutron capture cross-sections at n_TOF is discussed.

Tritium digital autoradiography with a Medipix2 hybrid silicon pixel detector

We report on the first measurements of 3H beta autoradiography obtained using a room temperature hybrid pixel detector, consisting of the Medipix2 single particle counting read-out chip bump-bonded to a 300 μm thick silicon pixel detector. This system has 256×256 square pixels of 55 μm pitch for a total sensitive area of 14×14 mm 2. Each pixel contains a double threshold discriminator and a 13-bit counter. Using a detection threshold equivalent to less than 6 keV and a background count rate of 5×10 −3 counts mm −2 s −1, with exposures up to several hours, real-time images have been obtained of tritium-labeled solution drops spotted on a thin mylar foil placed in contact with the continuous top electrode of the silicon detector, in open air condition.

Separation of proton-induced fission isotopes from dominant evaporation residues by adapted target stacking

To study low yields of fission products from proton-induced reactions we introduce two activation methods based on target stacking with suppression of otherwise dominating evaporation and spallation products; one method using thin Mylar foils which only transmit the fission products, the other one using cylindrical catchers at both sides of the target foils. The methods require no radiochemistry. Tests have been performed with targets of decreasing atomic number and decreasing fission cross-sections.

Investigation of geochemical composition of lake sediments using ED-XRF and ICP-AES techniques

The elemental composition of lake bottom sediment indicates the environmental changes of biological and geochemical processes in the water body and in the sediment‐water interface. Changes in soil-forming processes and vegetation in the catchment area also influence the quantitative composition of sediment. In order to analyse sediment quantitatively, several core samples were collected from depths of 600‐800 cm in a peat bog located in NE Hungary. The original wet core was divided into subsamples of 1 cm thickness, dried, homogenized and digested with nitric acid and hydrogen peroxide for inductively coupled plasma atomic emission spectrometry (Ca, Fe, Mn, Sr, Ba). The undissolved parts of the samples were analysed by energy-dispersive x-ray fluorescence spectrometry using the fundamental parameter method for Si, Ca, K, Ti, Zr and Y. The X-ray excitation of the samples was carried out with a Siemens K710-H x-ray generator applying Mo and Cr tubes for ranges of elements 21 < Z <4 0 and 14 <Z < 23, respectively. The primary spectra of the tubes were reconstructed by measured spectra scattered from a thin (20 mm) Mylar foil. The software outputs were the intensities of the x-ray fluorescence lines of the samples and of some pure elements which were provided by independent measurements with the Mo and Cr tubes. The final results of this combined quantitative analysis were used in the evaluation of the soil-development model using multivariate statistical analysis of the elemental composition of the sediment samples. Copyright ” 1999 John Wiley & Sons, Ltd.

Angular distribution measurements of 12C(d,p) 13C reaction below 350 keV deuteron energies using nuclear track detectors

Angular distribution of 12C(d,p) 13C reaction were measured at 13 angles for 223, 308 and 332 keV deuteron energies using nuclear track detectors (NTDs). The measurements were carried out over 25 to 164 degree angles in 10 degree steps using scattering chamber of 80° beam line of the 350 kV accelerator. In each run, a semiconductor surface barrier (SSB) monitor detector, masked by thin mylar foil, was placed at +164 degree and was used for flux and target thickness normalization between two runs of each angular distribution. In order to check the performance of the NTDs, angular distribution measurement was also repeated at 250 keV deuteron energy at which data had already been taken with surface barrier detectors. The angular distribution measured by NTDs was found comparable with measurements carried out using SSB detectors which indicate the possibility of using NTDs instead of expensive SSB detectors. The angular distributions of 12C(d,p) 13C reaction at 223, 250, 308, and 322 keV deuteron energies are backward peaked similar to those measured using SSB detectors. Within the experimental uncertainties, the detection efficiency of PM-335 NTDs for the protons from the 12C(d,p) 13C reaction for the −164 degree angle was found to be almost 100%.

X-ray study of the influence of water on the cellulose membrane structure

In spite of its application in technology the process of water permeation through a cellulose membrane has not been explained fully. Hydrophilic membranes play an important role in membrane processes. Recently, a swollen dry-layer model has been developed to describe permeation process through such membranes [1]. In the process, the permeation has been described generally as the sorption of liquid, its diffusion, and the evaporation and desorption of vapour. According to this model the layer containing liquid water in the swollen membrane exists on the upstream side of the membrane and another layer with vapour water on the downstream side. Also an isotope effect of H±D and O±O in the permeation process was observed, for the cellulose membranes Tomophan and Cuprophan [2, 3]. Structural research on the water permeation through membranes was carried out mainly in the static stage concerning the structure of water during the water±membrane contact (sorption). The research included infrared and nuclear magnetic resonance studies and molecular dynamics approaches [4±8]. Also a study of some parameters of the permeation process was performed [2]. It was found that water molecules form two kinds of bond of different strengths named ` free water'' and ` bound water''. The studies give evidence mainly about structural changes at a short distance (interatomic). In the present letter we have used X-ray methods to study the structural changes in cellulose caused by the sorption process. The expected results should inform us about the changes at larger distances than the interatomic distance. We studied the sorption of light and heavy water, in both the liquid and the vapour phase. Samples were prepared from cellulose membrane Tomophan I, 0.02 mm thick. First, we studied swelling of the membrane in contact with water. After soaking the membrane in water for a short time (about 3 s) its weight increased about two fold. A longer time of soaking did not effect the real increase. Next we tried to expose the membrane to the vapour. Independently of the exposure conditions (20±80 8C; 1±6 h), the weight of the membrane increased by 20%. For this weight increase the stage of saturation of the water-backbone bonds was reached. The differences between the light and heavy water, taking into account the density difference (10%), were very small. We decided to measure ®ve membranes in X-ray experiments: a dry membrane as a reference sample, two vaporized membranes and two membranes soaked in liquid, applying in all the above cases both light and heavy water. For the X-ray measurements, the membranes were covered with thin Mylar foil to avoid reduction in the water content. For the small-angle X-ray scattering (SAXS) experiment, which needed thick samples, small pieces of the membrane were put in a sample vessel, covered with two Mylar windows at both sides. The SAXS method considers scattering on whole particles having a mean electron density different from that of the medium and forming interface boundaries with it. Such particles can be pores or inclusions [9]. The total radiation intensity scattered in the small-angle region, using a Kratky-type set for measurements, can be expressed by the equation

Determination of vanadium and nickel in oil, asphaltene and bitumen using thin‐film energy‐dispersive x‐ray fluorescence spectrometry

AbstractThe concentration of vanadium and nickel in crude oils, bitumen and asphaltenes is an important parameter from the viewpoint of oil exploration. This kind of sample can be successfully analysed by energy‐dispersive x‐ray fluorescence spectrometry. A thin‐film sample preparation procedure is described. This involves first the addition to the sample of an internal standard, Pb, as a solution in chloroform, then pipetting some of the obtained solution on a thin Mylar foil, which covers the sample holder, followed by solvent evaporation, leaving a thin film. Laboratory‐prepared and commercial standards were used for calibration. Detection limits of 5 ppm for V and 2 ppm for Ni were obtained. The overall precision of the procedure expressed as relative standard deviation was 7%. Results obtained by two calibration procedures and other reported results for some samples are compared.