Journal of the ICRU最新文献_第9页

1. Introduction 1. 介绍

Journal of the ICRU Pub Date : 2014-04-01 DOI: 10.1093/jicru_ndw034

L. Maurice, T. Atkinson, A. Williams, J. Barker, A. Farrant

{"title":"1. Introduction","authors":"L. Maurice, T. Atkinson, A. Williams, J. Barker, A. Farrant","doi":"10.1093/jicru_ndw034","DOIUrl":"https://doi.org/10.1093/jicru_ndw034","url":null,"abstract":"Tracer testing was undertaken from sinking streams feeding the Chalk, a porous limestone aquifer characterised by frequent small-scale surface karst features. The objective was to investigate the nature and extent of sub-surface karstic development in the aquifer. Previous tracer testing has demonstrated rapid flow combined with low attenuation of tracer. In this study, at two sites rapid groundwater flow was combined with very high attenuation and at two other sites no tracer was detected at springs within the likely catchment area of the stream sinks tested, suggesting that tracer was totally attenuated along the flowpath. It is proposed that the networks beneath stream sinks in the Chalk and other mildly karstic aquifers distribute recharge into multiple enlarged fractures that divide and become smaller at each division whereas the networks around springs have a predominantly tributary topology that concentrates flow into a few relatively large cavities, a morphology with similarities to that of the early stages of karstification. Tracer attenuation is controlled by the degree to which the two networks are directly connected. In the first state, there is no direct linkage and flow between the two networks is via primary fractures in which tracer attenuation is extreme. The second state is at a percolation threshold in which a single direct link joins the two networks. A very small proportion of tracer reaches the spring rapidly but overall attenuation is very high. In the third state, the recharge and discharge networks are integrated therefore a large fraction of tracer reaches the spring and peak concentrations are relatively high. Despite the large number of stream sinks that recharge the Chalk aquifer, these results suggest that sub-surface conduit development may not always be continuous, with flow down smaller fissures and fractures causing high attenuation of solutes and particulates providing a degree of protection to groundwater outlets that is not seen in more highly karstic aquifers. Bacteriophage tracers that can be detected at very large dilutions (10) are recommended for investigating groundwater pathways where attenuation may be high.","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"7 1","pages":"5 - 7"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83692188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

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Appendix. Stopping Power and Range Tables for Charged Particles 附录带电粒子的停止功率和范围表

Journal of the ICRU Pub Date : 2014-04-01 DOI: 10.1093/jicru/ndw030

引用次数: 4

6. Photon Interaction Coefficients 6. 光子相互作用系数

Journal of the ICRU Pub Date : 2014-04-01 DOI: 10.1093/jicru_ndw035

{"title":"6. Photon Interaction Coefficients","authors":"","doi":"10.1093/jicru_ndw035","DOIUrl":"https://doi.org/10.1093/jicru_ndw035","url":null,"abstract":"As indicated in Section 2.2, the mass attenuation coefficient is given in terms of the sum of cross sections for photon interactions in the material, i.e., ðm=rÞ 1⁄4 ðNA=MAÞ P J sJ. However, for this report, the quantity of key importance for the dosimetry of ionizing radiation, particularly for primary standards, is the mass energy-transfer coefficient, ðmtr=rÞ 1⁄4 ðNA=MAÞ P J fJsJ, where fJ is the fraction of energy transferred to charged particles in the interaction of type J, and the closely related mass energy-absorption coefficient, ðmen=rÞ 1⁄4 ðmtr=rÞð1 gÞ, where g is the fraction of energy transferred to charged particles that is subsequently lost on average in radiative processes. Traditionally, the component cross sections, sJ, considered have been those for the interaction of the photon with atomic electrons and the Coulomb fields of the nucleus and atomic electrons, namely photoelectric absorption, coherent (Rayleigh) scattering, incoherent (mostly Compton) scattering, and pair production in the fields of the screened nucleus (pair) and atomic electrons (triplet). Interactions with nucleons (photonuclear cross sections) are usually not included in critically evaluated compilations. It should be noted that fJ is considered to be zero for coherent scattering, which removes consideration of coherent scattering in the calculation of mtr and men. A recent review by Pratt (2014) highlights our understanding of atomic photoeffect, Comptonscattering, and Rayleigh-scattering cross sections. He points out that, although much progress has been made in the theory and measurement of these photon-interaction cross sections, both theory and measurement still lack the accuracy to resolve discrepancies at levels of from 1 % to about 10 %. Compilations of such cross-section data are now indispensable in applications of radiation science, and figure importantly in the realization of measurement standards for ionizing radiation (see Section 3). A useful review of the history of the information used in such compilations can be found in the work of Hubbell (1969; 1999; 2006). Over more than six decades of such development, the results of theory and numerical computation have shown reasonable agreement with measured data and have largely replaced reliance on measurement as the basis for the standard reference data on photon-interaction cross sections. The work of Hubbell et al. (1975; 1979), culminating in the online database XCOM (Berger and Hubbell, 1987; Berger et al., 2010), has become a standard source of atomic cross sections for photon interactions. This Report is concerned with photon energies above about 1 keV and only with air, graphite, and liquid water; however, virtually all materials are involved in application areas of photon transport and dosimetry. Because our knowledge of the cross sections is still not complete, it appears difficult to draw unambiguous conclusions on which data to recommend. Rather, some relevant comparisons are made, and","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"14 1","pages":"49 - 69"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91254606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

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Front matter 前页

Journal of the ICRU Pub Date : 2014-04-01

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7. Impact of Recommendations 7.建议的影响

Journal of the ICRU Pub Date : 2014-04-01 DOI: 10.1093/jicru/ndw033

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6. Photon Interaction Coefficients 6.光子相互作用系数

Journal of the ICRU Pub Date : 2014-04-01 DOI: 10.1093/jicru/ndw035

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7. Impact of Recommendations 7. 建议的影响

Journal of the ICRU Pub Date : 2014-04-01 DOI: 10.1093/jicru_ndw033

{"title":"7. Impact of Recommendations","authors":"","doi":"10.1093/jicru_ndw033","DOIUrl":"https://doi.org/10.1093/jicru_ndw033","url":null,"abstract":"This Report has reviewed relevant data and has recommended values of quantities that play an important role in radiation dosimetry, especially those needed in measurement standards. This Section considers some of the implications of the recommended changes for dosimetric measurements and on calculations made in the fields of radiation medicine, industry, and other applications, including radiation research. Recommended values and uncertainties are given for Wair, the average energy required to produce an ion pair, the heat defect of liquid water, hW, and the radiation chemical yield for the Fricke dosimeter, G(Fe3þ). A new value is also recommended for the product, Wair sg,air, for Co g rays. The humidity correction, kh, for air-filled ionization chambers is reviewed, but no changes are recommended. However, it is noted that, for high precision, the variation of kh with relative humidity or, more properly, with the partial pressure of water vapor, should be considered. Data for the heat defect of graphite are reviewed, but no definitive conclusions could be reached and more study is recommended. The value of Wair for electrons is left unchanged at 33.97 eV, but its standard uncertainty has been increased from 0.05 eV (0.15 %) to 0.12 eV (0.35 %). This will have an impact on the uncertainty of airkerma standards based on free-air chambers and will for many standards become the dominant component. The available data for Wair indicate that it can be considered constant at high energies. However, for electron energies below about 10 keV, Wair cannot be considered constant. Furthermore, as was pointed out in Section 5.5, when the air kerma is obtained from a charge measurement, a correction should be applied for the charge of the initial electrons set in motion by the photons. The combined correction for these last two effects (see Table 5.7) can be significant for low-energy photons (up to 0.7 %) and could give rise to changes in primary standards. Recommendations have been made for the mean excitation energies for air, graphite, and liquid water as well as for the graphite density to use when evaluating the density effect (2.265 g cm). From these recommendations, tables of the stopping powers for electrons, protons, alpha particles, and carbon ions have been generated (see the Appendix). For air, no change in the value of the mean excitation energy is recommended, i.e., Iair 1⁄4 85.7 eV but now with an uncertainty of 1.2 eV (1.4 %); stopping power values for all particles thus remain unaltered, except for carbon ions, for which an Iair value of 82.8 eV was implicitly used in ICRU Report 73 (2005). For electrons in graphite, the change in the electronic stopping powers relative to those given in ICRU Report 37 (1987a) is shown in Fig. 7.1. The value of Ig has increased from 78 eV to 81 eV, and the standard uncertainty has decreased from 4 eV to 1.8 eV. The increase in the mean excitation energy and the change in the density used to evaluate the densi","PeriodicalId":91344,"journal":{"name":"Journal of the ICRU","volume":"15 1","pages":"71 - 77"},"PeriodicalIF":0.0,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87583848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

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Report 90. 90年的报告。

Journal of the ICRU Pub Date : 2014-01-01 DOI: 10.1093/jicru/ndw043

引用次数: 32

2. Prevention, Diagnosis, Prognosis, Treatment, and Outcome 2.预防、诊断、预后、治疗和结果

Journal of the ICRU Pub Date : 2013-04-01 DOI: 10.1093/jicru/ndw005

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5. Tumor and Target Volumes and Adaptive Radiotherapy 5.肿瘤和靶体积与适应性放射治疗

Journal of the ICRU Pub Date : 2013-04-01 DOI: 10.1093/jicru/ndw017

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