The uncertainty of counting at a defined solid angle

Abstract

Specific uncertainty components of counting at a defined solid angle are discussed. It is potentially an extremely accurate technique for primary standardisation of activity of alpha emitters and low-energy x-ray emitters. Owing to its reproducibility, it is very well suited for half-life measurements. Considered sources of uncertainty are 1) source-detector geometry, 2) solid-angle calculation, 3) energy loss and self-absorption, 4) scattering, 5) detection efficiency. Other sources of uncertainty, such as source weighing, counting, dead time and decay data are common to other standardisation methods. Statistical uncertainty propagation formulas are presented for the solid angle subtended by a circular detector to radioactive sources. Computer simulations were performed to investigate aspects of particle scattering.

Evidence against solar influence on nuclear decay constants

“…The measurement techniques employed are as follows: ionisation current measurements in a re-entrant ionisation chamber (IC) or a hospital calibrator (HIC) [31,32], net area analysis of full-energy γ-ray peaks (and integral spectrum counting) by γ-ray spectrometry with a HPGe detector (HPGe) [33], particle counting in a planar silicon detector in quasi-2πconfiguration (PIPS) [34], X-ray counting at a small defined solid angle with a gas-filled proportional counter (PC) [35,36], live-timed β–γ anti-coincidence counting (LTAC) [37], triple-to-double coincidence counting with a liquid scintillation vial and three photodetectors (TDCR) [38], liquid scintillation counting (LSC) [38], particle and photon counting in a sandwich CsI (Tl) spectrometer (CsI) [39], internal gas counting (IGC) [40], and α-particle counting at a small defined solid angle with a large planar silicon detector (αDSA) [35,36]. An overview of standardisation techniques and their sources of error can be found in the special issues 44(4) and 52(3) of Metrologia [41,42] and references in [25,28].…”

Methods of targets’ characterization

“…With LGA method the uncertainties as low as 0.02 % are feasible [7,8]. As reported in [9], two different set-ups can be used according to the activity of the samples, either with a variable or a fixed source-detector distance (up to 20 cm or 1.6 m under glove box respectively) where uncertainties of 0.3-0.5 % are reached with tens of spectra acquired in about 40 hours.…”

MetroMMC: Electron-Capture Spectrometry with Cryogenic Calorimeters for Science and Technology

“…These will also be performed using MMCs but require an entirely different setup. X-ray spectrometry is a widely used technique with MMCs, but the uncertainty budgets for metrology applications require special care in the experimental preparation and characterization of the detection efficiency (see e.g., [23,24]).…”

“…Especially the edge geometry needs to be designed carefully to avoid scattered particles reaching the detector, while keeping the particle transmission through the collimator edge to a minimum. The design principles are, e.g., well described in [23]. The absorber needs to be characterized for its detection efficiency in the desired energy range, ideally both with simulations and experimentally [24].…”