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[en] This book is a collection of contributions on the history of accelerator radiation protection by people who have worked or still work in this field at particle accelerators around the world. The radiation environment of these machines is the most complex man-made radiation field one could face. In fact, protection efforts must cover a large spectrum of particles and energies ranging from thermal, in the case of neutrons, to the primary energy of the accelerator. Therefore the correct assessment of the exposure risk for people working in such stray radiation fields is a theme of many of the articles. The editors deliberately refrained from guiding the authors' styles, so the book contains a collection of papers ranging from articles with literary ambitions to dry accounts on radiation protection efforts around a particular accelerator complex. Although this retains the originality of the individual contributions, one would have liked to see a somewhat more anecdotal/historical approach rather than concentrating on scientific depth. Considering the types and energies of the radiations involved another outstanding and reoccurring issue is the question of accelerator shielding, where correct answers require considerable experimental and calculational efforts. While no shielding (it has happened!) proved to be bad, overshielding never turned out to be a problem in view of the increase in intensities that older machines have gone on to achieve. Is this a book only for the few radiation protection specialists working in an accelerator environment? Not necessarily. The physics aspects of radiation protection (generally called health physics in the US) is always evident and makes many articles interesting to read even for the non-specialist. The editors' epilogue proudly claims that most health physicists working around accelerators regard themselves as the elite of their profession. On the other hand the statement made by one eminent colleague - ''that health physics became a little less physics and a little more metaphysics'' - cannot be ignored.
[en] The problem of creating a stray radiation grating which has as large a compartment ratio as possible, without the Bucky factor (ratio of the total incident radiation to the total radiation passing through) rising to an impermissible degree and which can be suitably made, particularly as a focussing stray radiation grating, is solved by the radiation absorbing layer being a pigment/binder layer and by the strips carrying a further layer, which is electrically conducting. (orig./HP)
[de]Die Aufgabe, einen Streustrahlenraster zu schaffen, der ein moeglichst grosses Schachtverhaeltnis aufweist ohne dass der Bucky-Faktor (Verhaeltnis der einfallenden Gesamtstrahlung zur insgesamt durchgelassenen Strahlung) unzulaessig steigt und der auf guenstige Art und Weise insbesondere auch als fokussierter Streustrahlenraster herstellbar ist, wird dadurch geloest, dass die strahlenabsorbierende Schicht eine Pigment-Bindemittel-Schicht ist und dass die Streifen eine weitere Schicht tragen, die elektrisch leitfaehig ist. (orig./HP)
[en] The practical radiologist does not have the means to obtain data for a comparison of anti-scatter grids of different design and manufacture. Therefore, attempts have been made to present in standards publications a generally approved measuring method and main parameters allowing objective comparison. The paper discusses the ICRU publication, the DIN standards 6826 and 6826/2, and the IEC standard. (DG)
[de]Der Radiologe als Anwender hat keine Moeglichkeit, durch eigene Messungen zu Daten zu gelangen, die es erlauben, Raster unterschiedlicher Bauart oder Herkunft miteinander zu vergleichen. Es wurde daher versucht, in Normen ein allgemein anerkanntes Messverfahren festzulegen, das zu Kenngroessen fuehrt, die einen objektiven Vergleich unterschiedlicher Raster ermoeglichen. Die ICRU-Norm, die DIN-Normen 6826 und 6826/2 sowie die IEC-Norm werden diskutiert. (DG)
[en] Purpose: To quantify experimentally scatter contribution to CTDI in center and peripheral holes of the body (32-cm) phantom. Methods: All experiments were performed in Service Mode of 750CT-Discovery with both tube and table were in stationary position, and with large filter and 40- mm collimation. First, transmission through acrylic was measured using acrylic rods of various lengths (1-cm to 33-cm), at 80, 120, and 140 kVp. These data were utilized to obtain dose from primary beam at different depths of acrylic. Thus, scatter-to-primary ratio (SPR) was determined for center-hole by measuring exposure with a pencil chamber. For peripheral hole SPR, dose was measured at eight different tube angles from 0° to 180°. Change in primary dose with tube angle due to both shape of bowtie filter and distance from tube was measured in air; hence, dose from primary from each of the 8 phantom measurements was determined and SPR was calculated by integrating the fitted models for primary and scatter distributions as a function of distance from tube. Also, scatter contribution from different segments of phantom to center-hole dose was measured using a custom-built acrylic phantom, which had similar SPR at the center-hole to that of standard body phantom. Results: After correcting for stray radiation (off-focus, scatter from collimators, etc.) for primary measurements, preliminary results of SPRs in center-hole dose of the body phantom for 80, 120, and 140 kVp were 6.8, 6.2, and 6.0, respectively, and for peripheral hole were 1.45, 1.44, and 1.39. Forward-scatter and backscatter contributions to center dose, at any point during tube rotation, were respectively, 62% and 38% with 80 kVp, and 60% and 40% with 120 and 140 kVp. Conclusion: SPR in both center and peripheral holes of body CTDI phantom was determined experimentally. Also, distribution of contributing scatter to center hole was estimated
[en] The efficiency of electron cyclotron heating is determined by the microwave absorption of the plasma. Good microwave absorption is also crucial for the machine safety. In this paper we present a method of evaluating the microwave absorption coefficient from stray radiation measurements. The discussed method is computationally simple and can be applied potentially in real time. Evolution of the second harmonic extraordinary mode (X2) microwave absorption coefficient in Wendelstein 7-X during the start-up phase is presented, as well as an estimate of the absorption coefficient for the second harmonic ordinary mode (O2) wave. (paper)
[en] A scatter correction algorithm for digitally acquired radiographs (SCADAR) is presented. SCADAR requires the acquisition of two digital images, taken at different object-to-detector distances. These two images are digitally magnification compensated, and subtracted. The primary component in the resulting difference image delta is mathematically eliminated, and hence the delta image is used as a measure of the local contribution of scattered radiation. A gray scale transformation is used to transform the delta image to a scattered component image, which is then smoothed by Fourier filtering, using a matched filter to increase the signal-to-noise ratio. The smoothed scatter image is then subtracted from its corresponding original image, resulting in the corrected SCADAR image. Implementation of SCADAR can result in a large increase in image contrast, and a significant reduction in shading due to scattered radiation effects. The mathematical derivation of the algorithm is developed, and experimental verification is given for some of the principles used. Using experimental images acquired from scattering phantoms, the results of SCADAR on various image parameters such as contrast and detail signal-to-noise ratio are discussed
[en] Investigated is the problem on application of gamma-gamma logging results to determine the diameter of boreholes within 4-40 cm range. Considered is the experimental dependence of the flux value of stray gamma radiation on the borehole diameter for inversioned probes. Shown is a principal applicability of gamma-gamma logging results to contactless cavernometry of boreholes
[en] The present state of knowledge on the influence of stray radiation on image quality and its physical description and quantification is summarized. Experimental results on the influence of physical parameters on the fraction of scattered radiation and the effect of scatter reduction by air gap technique and secondary radiation grids are committed. Open theoretical and practical problems and the limitations of common methods of scatter reduction are pointed out. (author)
[en] Here we report the first measurements of the power levels of stray radiation in the vacuum vessel of Wendelstein 7-X using absolutely calibrated sniffer probes. The absolute calibration is achieved by using calibrated sources of stray radiation and the implicit measurement of the quality factor of the Wendelstein 7-X empty vacuum vessel. Normalized absolute calibration coefficients agree with the cross-calibration coefficients that are obtained by the direct measurements, indicating that the measured absolute calibration coefficients and stray radiation levels in the vessel are valid. Close to the launcher, the stray radiation in the empty vessel reaches power levels up to 340 kW/m"2 per MW injected beam power. Furthest away from the launcher, i.e., half a toroidal turn, still 90 kW/m"2 per MW injected beam power is measured.
[en] The origin and propagation of straylight in monochromators is investigated and an expression is derived for the ratio of the straylight and the effective spectral intensity within the exit slit. This expression, for a prescribed resolution and speed, permits to select the design involving the minimum of straylight which can be attained. (orig.)
[de]Die Entstehung und Ausbreitung des Streulichts in Monochromatoren wird untersucht und ein Ausdruck fuer sein Verhaeltnis zum Nutzlicht im Austrittsspalt abgeleitet; dieser Ausdruck gestattet es, die streulichtaermste Bauart bei vorgegebener Aufloesung und Lichtstaerke auszuwaehlen. (orig.)