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[en] A modified technique of the self-absorption method has been developed and applied to natural mercury afterglows. A narrow light-emitting layer is produced inside an absorption tube by external pumping at the moment of measuring the afterglow. (orig.)
[en] The use in situ ion detection of alkali vapor coupled with multiphoton ionization provides a technique of highest sensitivity for the investigation of the multiphoton spectroscopy involving alkali atoms. This technique has been applied in this work to study two-photon self-absorption of the atomic lines of the cesium 62Ssub(1/2)-72Psub(1/2,3/2) doublet. The dispersion curve was obtained with a tunable dye-laser for two-photon ionization of cesium over the 4500-4600 A wavelength range as a function of vapor pressure and source intensity. The atomic lines 62Ssub(1/2)-72Psub(1/2) and 62Ssub(1/2)-72Psub(3/2) were found to be self-reversed and asymmetrically broadened towards the longer wavelength. Sensitivity was observed to be an order of magntiude in excess of that obtained from classical absorption techniques and the observation of a quadratjc dependence of the ionic signal confirmed the multiphoton nature of the detection sequence. (author)
[en] LiF-thermoluminescence dosimeters are now being widely used in various fields of personnel and biomedical dosimetry. Particularly in fast neutron dosimetry the secondary recoil protons from the surrounding hydrogeneous material possess a limited range in the TLD-chips. The same phenomenon may occur in the case of heavy charged particle, alpha or proton dosimetry. When the TLD-chip is heated the luminescence light emitted from the irradiated layer is partially absorbed in the rest of the chip. thus a correction factor should be necessary when thick TLD-chips or powdered TL-material are used. In this report the experimental value of the extinction coefficient of LiF-dosimeters (TLD-100 of Harshaw Chemical Co.) is presented. Groups of TLD-100 dosimeters (3.2 x 3.2 x 0.4 mmsup3) with four TLD-chips were irradiated with 60Co-gamma rays up to a dose level of about 1 Gy at a dose rate of 2.3 Gy/h. The irradiated chips were covered with different numbers of TLD-chips (6 x 6 x 0.9 mm3) and evaluated with DAT-1 TL-reader, developed at our institute at a heating rate of 0.46 0C/s. The extinction curve was derived from the main TL-peak height and fitted by an exponentail function of type: I = I0exp (-μx). The value of the extinction coefficient was determined to be 0.51 +- 4.5% mm-1. (Author)
[en] We present a theoretical study of CS line profiles in archetypal hot cores. We provide estimates of line fluxes from the CS(1-0) to the CS(15-14) transitions and present the temporal variation of these fluxes. We find that (1) the CS(1-0) transition is a better tracer of the Envelope of the hot core whereas the higher-J CS lines trace the ultracompact core (UCC); (2) the peak temperature of the CS transitions is a good indicator of the temperature inside the hot core; (3) in the Envelope, the older the hot core the stronger the self-absorption of CS; (4) the fractional abundance of CS is highest in the innermost parts of the UCC, confirming the CS molecule as one of the best tracers of very dense gas.
[en] The Tomographic Gamma Scanner (TGS) is a Non-Destructive Assay (NDA) instrument that combines high-resolution gamma spectroscopy with low spatial resolution three-dimensional image reconstruction in order to reduce bias and improve precision for measurements of drummed waste. The TGS technique is especially suited to measure containers with non-uniform source distributions and low-to me-dium-density heterogeneous matrices, compared with traditional NDA methods. Canberra recently built, installed, and commissioned a TGS system, intended primarily for the measurement of plutonium (Pu) bearing waste, at a European nu-clear fuel reprocessing facility. Pu assays using the TGS technique present technical challenges distinct from those typically encountered in traditional LLW applications. Among these is the need to apply corrections for self-absorption effects that occur on scales smaller than the TGS spatial resolution, and can compromise the assay result if not included in the TGS imaging methodology. We present a brief review of the Self Absorption Correction (SAC) technique, and discuss the complications involved with its application to the TGS methodology with examples from our recent experience. This work continues a Canberra history of further developing and refining a technique to solve emerging problems, having commercialized the original methodology by partnering with the research institution that pioneered it. The TGS and the SAC methodologies were originally developed by Los Alamos National Laboratory (LANL) and John Fleissner respectively, and this work illustrates how Canberra has implemented an advancement of these techniques in a new TGS system. (authors)
[en] The history of the development of the 4 π counting method is reviewed. The unique properties of the 4 π counter system are described and the criteria are specified which place disintegration rate measurements, made with the system, on an absolute basis. The types of radioactive decay process to which the method is applicable are outlined, together with the various errors to which a given measurement is liable. Departure of response probability from unity, absorption of radiation in the source-mounting system, and source self-absorption are discussed in detail. (author)
[fr]L'auteur fait l'historique des progres de la methode de comptage 4 π. Il decrit les proprietes remarquables du dispositif de comptage 4 π et precise les conditions dans lesquelles les mesures du taux de desintegration se font avec ce dispositif sur une base absolue. Il donne un apercu des types de processus de desintegration radioactive, ainsi que de diverses erreurs auxquelles est sujette une mesure donnee. Il examine en detail le cas ou la probabilite de reponse s'ecarte de l'unite, l'absorption des rayonnements dans le support de la source et l'autoabsorption de la source. (author)
[es]En la memoria el autor expone el desarrollo del metodo de recuento 4 π. Describe las caracteristicas particulares de este metodo y explica las razones por las que las mediciones de la velocidad de desintegracion efectuadas segun ese procedimiento tienen un caracter absoluto. Se indican, asimismo, los tipos de procesos de desintegracion radiactiva a los que se puede aplicar el metodo, asi como los diferentes defectos de que puede adolecer una medicion determinada. Tambien se estudia detenidamente el caso en que la probabilidad de respuesta no es igual a la unidad, la absorcion de radiaciones en el soporte de la fuente y la autoabsorcion de la misma. (author)
[ru]Daetsya obzor istorii razvitiya metoda scheta s pomoshch'yu 4 π schetchikov. Privoditsya opisanie unikal'nykh svojstv sistemy 4 π schetchikov, usta navlivayutsya kriterii, kotorye stavyat izmereniya skorosti raspada, osushchestvlyaemye dannoj sistemoj, na sovershennuyu osnovu. V obshchikh chertakh daetsya opisanie vidov protsessa radioaktivnogo raspada, ego razlichnye pogreshnosti, kotorye mogut v dannom izmerenii. Podrobno obsuzhdaetsya otklonenie veroyatnoj chuvstvitel'nost i ot edinitsy, pogloshchennie radiatsii v sisteme ustanovki istochnika i samopogloshchenie istochnika. (author)
[en] The study of cold atomic hydrogen (H I) in molecular clouds has the potential to significantly improve our understanding of the formation of molecular clouds, the atomic to molecular hydrogen conversion process, and star formation. Results from the first large survey of H I Narrow Self Absorption (HINSA) features outside of the Taurus Molecular Cloud Complex are presented. Previous hypotheses that cold atomic hydrogen represents the third largest constituent of molecular clouds are confirmed with a mean abundance of 10-2.8 in comparison with the total proton column density. HINSA features are observed in over 80% of the observed clouds, accompanied by indications that cold H I probably exists in all clouds. We find that HINSA features are observable to distances of at least 700 pc. Nine clouds have been mapped in detail revealing that HINSA abundances can vary significantly within a cloud both spatially and in an individual velocity component. Possible explanations for this phenomenon are briefly discussed.
[en] Self absorption coefficient of gamma radiation emitted by collimated cylindrical sources with a central channel is calculated. Experimental verification agrees with results
[fr]On calcule le coefficient d'autoabsorption d'un rayonnement gamma collimate emis par des sources cylindriques ayant un canal central. Une verification experimentale confirme les resultats obtenus