Measurement Of Mass Attenuation Coefficients Research Articles

C133 活性炭吸着層内エタノール吸着量分布の可視化・計測(OS4 省エネルギー・コジェネ・ヒートポンプ(2))

It is important for a design of an adsorber to clarify adsorbed refrigerant distribution in adsorbent bed during transient conditions with adsorption or desorption, because the adsorption and desorption process is complex phenomena with heat and mass transfer and strongly effect on the cycle performance of an adsorption refrigerating cycle. Adsorbed refrigerant distributions in an activated carbon particle bed in a metallic rectangular vessel had been quantitatively measured by a neutron radiography method. Ethanol was used as the refrigerant. An umbra method using a checked neutron absorber grid was applied for a quantitative measurement. The measured mass attenuation coefficient of ethanol was 0.386 m^2/kg. It was confirmed from the measurement for an adsorption bed in adsorption equilibrium that the adsorption amount could be quantitatively measured by the method. From the experiments of adsorption and desorption process with heat transfer, it could be clearly visualized that the adsorbed amount in the adsorption process was strongly affected by the position of the heat-transfer surface. In the desorption process, the effect was relatively small, because the heat diffusion in the adsorption bed might be enhanced by regenerated superheated vapor flow.

Measurement of mass attenuation coefficients of Eremurus–Rhizophora spp. particleboards for X-ray in the 16.63–25.30 keV energy range

The roots of Eremurus spp. were used as a bio-adhesive in the fabrication of Rhizophora spp. particleboards. The mass attenuation coefficients of Eremurus–Rhizophora spp. particleboard of six samples with two different weight percentages of the Eremurus spp. root (6% and 12%) and three various Rhizophora spp. particle sizes (≤149µm, 149–500µm and 500–1000µm) were determined by using X-ray fluorescence (XRF) photons in 16.63keV and 25.30keV of the photon energy range. The results were compared with theoretically calculated mass attenuations using the XCOM computer program for younger-age (breast 1: 75% muscle+25% fat), middle-age (breast 2: 50% muscle+50% fat), and old-age (breast 3: 25% muscle+75% fat) breasts. The results indicated that Eremurus–Rhizophora spp. particleboard is the appropriate suitable phantom in the diagnostic energy region. The mass attenuation coefficient in the low weight percentage of the bio-adhesive and the large Rhizophora spp. particle size were found very close to breast 1. Moreover the mass attenuation coefficient of the sample with high weight percentage of the bio-adhesive and small Rhizophora spp. particle size was found very close to water as a standard material phantom. In addition, the viscosity of dissolved Eremurus spp. root in water could be considerably higher than that of formaldehyde-based adhesives, which affects on some properties such as high strength and high binding.

Measurements of mass attenuation coefficient, effective atomic number and electron density of some amino acids

The mass attenuation coefficients of some amino acids, such as dl-aspartic acid-LR(C4H7NO4), l-glutamine (C4H10N2O3), creatine monohydrate LR(C4H9N3O2H2O), creatinine hydrochloride (C4H7N3O·HCl) l-asparagine monohydrate(C4H9N3O2H2O), l-methionine LR(C5H11NO2S), were measured at 122, 356, 511, 662, 1170, 1275 and 1330keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma-rays were detected using NaI (Tl) scintillation detection system with a resolution of 0.101785 at 662keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff), and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) initially decrease and tend to be almost constant as a function of gamma-ray energy. Zeff and Neff experimental values showed good agreement with the theoretical values with less than 1% error for amino acids.

Mass attenuation coefficients of fabricated Rhizophora spp. particleboard for the 15.77 – 25.27 keV range

The Rhizophora spp. wood what is hard and heavy is considered strong in strength and is suitable for structural purposes. Generally, Rhizophora spp. was used in radiation dosimetry research and it is being used in this project too. There are some disadvantages in using the raw (natural) material of Rhizophora spp. in radiation dosimetry research and there is a need to modify this natural wood to be easily used as a phantom in radiation dosimetry. The mass attenuation coefficients (/) of fabricated Rhizophora spp. particleboard were determined for photons in the energy range of 15.77–25.27 keV. This was carried out by studying the attenuation of X-ray fluorescent photons from zirconium, molybdenum, palladium, silver, indium and tin targets. The results were compared with theoretical values for average breast tissues in youngage, middle-age and old-age groups calculated using photon cross section database (XCOM), the well-known code for calculating attenuation coefficients and interaction cross-sections. The measured mass attenuation coefficients were found to be very close to the calculated XCOM values in breasts of old-age group.

Determination of K shell parameters of silver using high resolution HPGe detector spectrometer

The K shell parameters such as K shell photoelectric cross-section at K shell binding energy, K shell jump ratio, K shell jump factor, the Davisson- Kirchner ratio and K shell oscillator strength of silver have been determined using high resolution HPGe detector coupled to 16K multichannel analyser. In this method the K X-ray photons in the energy region from 8 to 52 keV are generated by sending 59.56 keV gamma photons from Am-241 source on various targets. These X-ray photons are allowed to pass through a silver foil in good geometry arrangement. By measuring the intensities of incident and transmitted photons, the mass attenuation coefficients are determined at various X-ray energies. Measured mass attenuation coefficient around K shell binding energy and K shell parameters have been compared with values predicted by XCOM and FFAST and with other experimental values.

Effect of detector collimation on the measured mass attenuation coefficients of some elements for 59.5–661.6 keV gamma-rays

Mass attenuation coefficients were determined experimentally for Sc, Ni and W for gamma energies of 59.5, 122, 276, 302, 356, 383 and 662keV for different detector collimator diameters ranging from 2 to 10mm. The aim was to investigate the quantitative analysis of detector collimator diameter effect on measured mass attenuation coefficients. It was found that measured mass attenuation coefficients decrease systematically with the increasing collimator diameter. The relative difference was found to be up to around 3% in some cases. The observed decrease in mass attenuation coefficients was attributed to the detection of elastic and inelastic scattered photons from the absorber. In elastic scattering process the photons change in direction but not in energy and get counted under the full energy peak if they reach the detector. In inelastic scattering however, both direction and energy of the scattered photons change. It was seen that most of the inelastic scattered photons also get counted by the detection system since they lose an amount of energy lower than the energy resolution of the detector. It is understood from the present results that it is essential to take into account the experimental geometry when reporting mass attenuation coefficients.

Measurement of mass attenuation coefficients of Rhizophora spp. binderless particleboards in the 16.59–25.26 keV photon energy range and their density profile using x-ray computed tomography

The mass attenuation coefficients of Rhizophora spp. binderless particleboard with four different particle sizes (samples A, B, C and D) and natural raw Rhizophora spp. wood (sample E) were determined using single-beam photon transmission in the energy range between 16.59 and 25.26keV. This was done by determining the attenuation of Kα1 X-ray fluorescent (XRF) photons from niobium, molybdenum, palladium, silver and tin targets. The results were compared with theoretical values of young-age breast (Breast 1) and water calculated using a XCOM computer program. It was found that the mass attenuation coefficient of Rhizophora spp. binderless particleboards to be close to the calculated XCOM values in water than natural Rhizophora spp. wood. Computed tomography (CT) scans were then used to determine the density profile of the samples. The CT scan results showed that the Rhizophora spp. binderless particleboard has uniform density compared to natural Rhizophora spp. wood. In general, the differences in the variability of the profile density decrease as the particle size of the pellet samples decreases.

Study of non-validity of mixture rule near K-absorption edges by X-ray spectrometric technique

X-ray spectrometric technique has been described to determine the X-ray mass attenuation coeffi- cient, l/q, of X-rays employing HPGe X-ray detector and radioactive sources. The photon intensity is measured by gating the channel of the spectrometer at FWHM/photo peak. Using the technique the ''best value'' values of l/q were obtained for those thicknesses which lie in the transmission (T) range 0.5 C T C 0.02. Total attenuation cross sections for other elements and lead compounds were measured at photon energies from 17 to 88 keV to study the Bragg's additivity law near the absorption edge of the lead. The measured values of mass attenuation coefficient values are compared with theoretical values obtained using Winxcom (programme). This study suggests that measured mass attenuation coefficient values at and near absorption edges differ from the theoretical value by about 17-23%.

Characterization of the Metrology beamline at the SOLEIL synchrotron and application to the determination of mass attenuation coefficients of Ag and Sn in the range 3.5 ≤ E ≤ 28 keV

This work presents the new Metrology beamline at the SOLEIL synchrotron facility and a first attempt to quantitative measurements of mass attenuation coefficients for Ag and Sn performed on the hard X‐ray branch. We first describe the beamline itself and the characterization performed of the unfocused monochromatic beam running mode. We performed a first experimental measurement of mass attenuation coefficients in the range 3.5 ≤ E ≤ 28 keV and we also derived the K‐absorption and L‐absorption jump ratios. The results are compared with theoretical values as well as with other experimental data and agree well with previous published values. Copyright © 2011 John Wiley & Sons, Ltd.

Measurement of Mass Attenuation Coefficients of Blue Sapphire at Different Photon Energy by Compton Scattering Technique

The mass attenuation coefficients of blue sapphire were measured at the different energy of γ-rays using the Compton scattering technique. There are in good agreement of scattered gamma rays energies between theoretical value and experimental value, reflecting the validation of Compton scattering system setup. The results show that, the experimental values of mass attenuation coefficient are in good agreement with the theoretical values. The mass attenuation coefficients increase with the decrease in gamma rays energies. This may be attributed to the higher photon interaction probability of blue sapphire at lower energy. This result is a first report of mass attenuation coefficient of blue sapphire at different gamma rays energies.

MO‐E‐204C‐07: A Scatter Theory Based Approach for MR‐Guided, Individualized PET Attenuation Correction in PET/MR Imaging

Purpose: In PET/MR, creation of an attenuation map from the patient's MR image is critical to quantitative PET but remains challenging because MR signals are not directly related to photon attenuation. The existing methods segment the T1‐weighted MR image and then assign average tissue attenuation coefficients to the segmented classes. Before the segmentation, coregistration between the MR image and CT, initially corrected PET and/or a template of MR images is performed. None of the methods are based on rigorous physical theory. For the first time, we developed a method from quantum scatter theory for estimating the attenuation map using the patient's proton density weighted MR image only. No coregistration is needed. Methods: Photon attenuation in human tissues at the photon energy of 511 keV is dominated by Compton scatter of which the probability depends on Z/A of the tissues. Here Z is atomic number and A atomic mass. Since Z/A is equal or close to 1/2 for the major elements in tissues, except hydrogen (Z/A = 1), the tissue mass attenuation coefficient can be calculated from the amount of hydrogen atoms in unit tissue that is obtained from a proton density weighted MR image. Initial assessment has been done by applying the method to calculating mass attenuation coefficients and then comparing with measured values. Results: The calculated attenuation coefficients agree well with the measured values. The differences between the calculated and measured mass attenuation coefficients for water, dry air, muscle and bone are 0.17%, 0.10%, 1.8% and 0.95%, respectively. The calculated number of hydrogen atoms in 1 gram of water also agrees with the exact value with a deviation of 1.8%. Conclusions: The scatter theory based method produces accurate attenuation coefficients. However, experimental evaluation with phantoms or/and patients must be performed and is currently under way.

Mass attenuation coefficients in the range , K fluorescence yield and relative X-ray emission rate for Ti, V, Fe, Co, Ni, Cu and Zn measured with a tunable monochromatic X-ray source

This work presents new measurements of mass attenuation coefficients in the range 3.8⩽E⩽11keV, K-absorption jump-ratios, Kα and Kβ fluorescence yields for Ti, V, Fe, Co, Ni, Cu and Zn. We use the experimental facility SOLEX, a tunable monochromatic X-ray source combined with an energy-dispersive high-purity germanium detector. The results are compared with theoretical values as well as with other experimental data and show a relatively good agreement. However, the derived K-jump-ratios appear larger than those widely used in the XCOM database. The Kα and Kβ fluorescence yields and the corresponding relative emission rates Kβ/Kα are also derived, which was made possible by the use of energy-dispersive detectors with good spectral resolution.

X-ray mass attenuation coefficients and imaginary components of the atomic form factor of zinc over the energy range of 7.2–15.2 keV

The x-ray mass attenuation coefficients of zinc are measured in a high-accuracy experiment between 7.2 and 15.2 keV with an absolute accuracy of 0.044% and 0.197%. This is the most accurate determination of any attenuation coefficient on a bending-magnet beamline and reduces the absolute uncertainty by a factor of 3 compared to earlier work by advances in integrated column density determination and the full-foil mapping technique described herein. We define a relative accuracy of $0.006%$, which is not the same as either the precision or the absolute accuracy. Relative accuracy is the appropriate parameter for standard implementation of analysis of near-edge spectra. Values of the imaginary components $f\ensuremath{''}$ of the x-ray form factor of zinc are derived. Observed differences between the measured mass attenuation coefficients and various theoretical calculations reach a maximum of about 5% at the absorption edge and up to 2% further than 1 keV away from the edge. The measurements invite improvements in the theoretical calculations of mass attenuation coefficients of zinc.

An improvement to the full-foil mapping technique for high accuracy measurement of X-ray mass attenuation coefficients

The limiting uncertainty in recent high accuracy measurements of the mass attenuation coefficient is the measurement of the integrated column density. An improvement in the design of the absorption foil holder is described which reduces the integrated column density uncertainty. The new design allows the edges of the foil to be more accurately mapped by the X-ray beam by reducing the largest source of uncertainty in the foil mapping: the uncertainty in the points along the foil edge. The method is shown to reduce the uncertainty in measurements of the mass attenuation coefficient of zinc foils. The reduced uncertainty in the full-foil mapping will allow the X-ray Extended Range Technique (XERT) to be applied to small non-metallic absorption foils more accurately.

Mass attenuation coefficients of X-rays in different medicinal plants

The mass attenuation coefficients of specific parts of several plants, (fruits, leaves, stem and seeds) often used as medicines in the Indian herbal system, have been measured employing NaI (TI)) detector. The electronic setup used is a NaI (TI) detector, which is coupled to MCA for analysis of the spectrum. A source of 241Am is used to get X-rays in the energy range 8–32 keV from Cu, Rb, Mo, Ag and Ba targets. In the present study, the measured mass attenuation coefficient of Ocimum sanctum, Catharanthus roseus, Trigonella foenum- graecum, Azadirachta indica, Aegle marmelos, Zingiber officinalis, Emblica officinalis, Anacardium occidentale, Momordica charantia and Syzygium cumini show a linear relation with the energy.

Mass attenuation coefficients of natural Rhizophora spp. wood for X-rays in the 15.77-25.27 keV range

The mass attenuation coefficients (mu/rho) of Rhizophora spp. were determined for photons in the energy range of 15.77-25.27 keV. This was carried out by studying the attenuation of X-ray fluorescent photons from zirconium, molybdenum, palladium, silver, indium and tin targets. The results were compared with theoretical values for average breast tissues in young-age, middle-age and old-age groups calculated using photon cross section database (XCOM), the well-known code for calculating attenuation coefficients and interaction cross-sections. The measured mass attenuation coefficients were found to be very close to the calculated XCOM values in breasts of young-age group.

Measurement of mass attenuation co-efficient of Zaria soil using gamma ray transmission method

Measurement of mass attenuation co-efficient of Zaria soil using gamma ray transmission method

Mass attenuation coefficient of chromium and manganese compounds around absorption edge

The total mass attenuation coefficient for Potassium dichromate, Potassium chromate and Manganese acetate compounds are measured at different photon energies 5.895, 6.404, 6.490, 7.058, 8.041 and 14.390 keV using Fe-55, Co-57 and 241Am source with Copper target, radioactive sources. The photon intensity is analyzed using a high resolution HPGe detector system coupled to MCA under good geometrical arrangement. The obtained values of mass attenuation coefficient values are compared with theoretical values. This study suggests that measured mass attenuation coefficient values at and near absorption edges differ from the theoretical value by about 5-28%.

An LIII (2P3/2) subshell absorption jump ratio and jump factor for bismuth

In this paper, we report on measurement of the first experimental LIII (2P3/2) subshell absorption jump ratio and jump factor value which were derived from new mass attenuation coefficients measured at the upper and lower energy branches of the LIII absorption edge using an energy dispersive x-ray fluorescence (EDXRF) spectrometer for bismuth. The measurements of mass attenuation coefficients, at 36 energies from 10.010 to 17.478 keV, were done in a transmission geometry utilizing the Ki (i = α, α1,2, β, β1,2) and Li (i = α, β, β1,2, γ, γ1, l) x-rays from different secondary source targets excited by the 59.543 keV γ-photons from an 241Am annular source and detected by an ultra-LEGe solid-state detector with a resolution of 0.15 keV at 5.9 keV. The results have been compared with theoretical values.

Effective atomic numbers and electron densities of CuGaSe2 semiconductor in the energy range 6–511 keV

AbstractThe effective atomic numbers and electron densities of the CuGaSe2 semiconductor were calculated at 29 different energies from 6.9 to 511.0 keV by using the measured mass attenuation coefficients. Also, the mass attenuation coefficients for Cu, Ga, and Se elements were obtained at this energy range. The samples were irradiated using Cd‐109, Co‐57, Ba‐133, and Na‐22 radioactive sources. The x‐ray energies were obtained using secondary targets. The gamma and x‐rays were counted by an Ultra‐LEGe detector with a resolution of 0.55 at 122.0 keV. The mass attenuation coefficients were compared with theoretical ones obtained using the XCOM program. Copyright © 2008 John Wiley & Sons, Ltd.