Search

Laser-induced fluorescence (LIF) is an established noninvasive measurement method to determine temperature distributions and local gas concentrations in combustion processes with high spatial and temporal resolution. This work presents high-precision LIF spectra of acetone and other tracers at ambient conditions. By using a large UV-sensitive sCMOS camera instead of an image intensified camera, many issues like nonlinearity, varying sensitivity, vignetting, limited resolution etc. could be minimized or eliminated. Particular care was taken to remove residual stray light and to calibrate the spectra with metrological traceability to the International System of Units SI. [ABSTRACT FROM AUTHOR]

Experimental investigation of a partially premixed flame stabilized in a combination of bluff body and swirling flowfields is reported. Simultaneous measurement of 2D fuel distribution (Acetone-PLIF) and flame structure (OH-PLIF) are performed with varying thermal power. Two flame stabilization modes – swirl influenced conical shaped, and, bluff-body influenced toroidally shaped – are observed in OH chemiluminescence measurements. Upstream propagation of the flame with decreasing global equivalence ratios is noticed, with the flame being transferred from the swirl-influenced to the bluff body influenced flowfields. The average flame stabilization location in both modes is found to be approximately close to the stoichiometric surface with the flame base oriented toward the inner shear layer. The degree of fuel/air mixing calculated from Acetone PLIF images by determining the unmixedness shows that the stabilization locations overlap with regions of perfect mixing. The swirl-influenced flames are stabilized at the farthest distance from the burner exit, with the flame base closer to the stoichiometric surface, whereas the bluff body influenced flames oriented along the stoichiometric surface in the inner shear layer. [ABSTRACT FROM AUTHOR]

In beta dosimetry, the absorbed dose rate changes rapidly with the depth in a given medium. Its knowledge is essential for the full characterisation of the beta reference fields and the evaluation of the response of beta detectors.This work presents a general formalism for the precise determination of beta depth–dose curves by means of ionisation chamber measurements. An extrapolation chamber is not required. The formalism is appropriate for the determination of the full range depth–dose curve of up to 10 mm depth and more, when all electrons are stopped. Particular care was taken for the determination of the correction factors for the ISO 6980 reference fields, which are the most common beta reference fields. The formalism is proved experimentally: The depth–dose curves of all beta sources available at the Physikalisch-Technische Bundesanstalt (PTB) were determined and compared with the curves published in ISO 6980, yielding an excellent agreement.The presented formalism reflects the state-of-the-art of depth–dose measurements at the PTB. [ABSTRACT FROM AUTHOR]

The most common reference fields in beta dosimetry are the ISO 6980 series 1 radiation fields produced by the beta secondary standard BSS2 and its predecessor BSS. These reference fields require sealed beta radiation sources (147Pm, 85Kr or 90Sr/90Y) in combination with a source-specific beam-flattening filter, and are defined only at a given distance from the source. Every radiation sources shipped with the BSS2 is sold with a calibration certificate of the Physikalisch-Technische Bundesanstalt. The calibration workflow also comprises regular depth–dose measurements.This work publishes complete depth–dose curves of the series 1 sources 147Pm, 85Kr and 90Sr/90Y in ICRU tissue up to a depth of 11 mm,when all electrons are stopped. For this purpose, the individual depth–dose curves of all BSS2 sources calibrated so far have been determined, i.e. the complete datasets of all BSS2 beta sources have been re-evaluated. It includes 191 depth–dose curves of 116 different sources comprising more than 2200 data points in total. Appropriate analytical representations of the nuclide-specific depth–dose curves are provided for the first time. [ABSTRACT FROM AUTHOR]

The international standard ISO 4037-3:1999 recommends a cylindrical polymethyl methacrylate rod phantom of 300 mm length and 19 mm diameter for the calibration of extremity dosemeters worn on the finger. No tolerances are stated. This paper investigates the influence of the actual rod phantom dimensions on the calibration results of finger dosemeters. For this purpose, thermoluminescence detectors were attached to rod phantoms of different size and irradiated at the PTB reference X-ray fields. Rod phantoms with a diameter of (19±1) mm and a length of at least 100 mm can be considered to be equivalent for the calibration of finger dosemeters, since the variation in the calibration results is below the significance level of 1 %. The decrease in the response towards the edge of the phantom is negligible as long as the distance from the nearest edge exceeds 10 mm. [ABSTRACT FROM AUTHOR]