Study of scattering in a low geometry alpha counter for high precision activity measurements

Blanchis, P.

doi:10.1016/0167-5087(84)90676-8

Cited by 7 publications

(10 citation statements)

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“…The uncertainty of counting at a defined solid angle by several institutes, including IRMM (formerly CBNM) [8,9], LRL [10], NIST [11], ANL [12], CIEMAT [13,14], LNE-LNHB [15,16] and PTB [17]. New set-ups have recently been constructed in TAEK (Turkey) and NPL (UK), inspired by the IRMM model.…”

Section: Metrologiamentioning

confidence: 99%

“…The uncertainty components involved with low-geometry alpha counting have been discussed in the past [5,6,16]. It was concluded that uncertainties as low as 0.02% should be feasible.…”

Section: Metrologiamentioning

confidence: 99%

“…Measures need to be taken to avoid a non-negligible fraction of particles emitted at wide angles being counted in this manner (see section 4). The radius of the cylindrical tube can be increased, which reduces the effective solid angle of the detector for particles scattering off the wall [5,16]. A very effective measure is the installation of baffles [5,6], which are thin metallic plates with a central aperture placed in parallel with the source and detector plane, to stop particles flying towards or scattered away from the side wall (see figure 1).…”

Section: Chamber and Spacersmentioning

confidence: 99%

“…IRMM uses a segmented design with source chamber, distance tube and diaphragm fitting together on smoothly connecting flanges. The distance between diaphragm and a reference plate in the source holder can be measured directly or calculated from the sum of the heights of the individual components with an accuracy of about (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) µm. The distance seems unaffected by vacuum pumping.…”

Section: Chamber and Spacersmentioning

confidence: 99%

“…For smaller source-detector distances, the series involves the summation of huge terms with opposite sign and does not easily converge to realistic values. Sensitivity factors can be easily obtained from differentiation of equation (16). For example, defining G(k, l ,m) as the term in the summations, independent variations of the eccentricity a leads to the following uncertainty contribution to Ω S : Just as for a point source, the uncertainty due to a small horizontal shift of the source is low for a small centred source, but increases by orders of magnitude for large off-centre sources for which the solid angle varies significantly in various points of its surface.…”

Section: Homogenous Disk Sourcementioning

confidence: 99%

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The uncertainty of counting at a defined solid angle

Pommé

2015

Metrologia

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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.

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Section: Metrologiamentioning

confidence: 99%

“…The uncertainty components involved with low-geometry alpha counting have been discussed in the past [5,6,16]. It was concluded that uncertainties as low as 0.02% should be feasible.…”

Section: Metrologiamentioning

confidence: 99%