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| Titel |
The Problem of using Quartz as a radiation dosimeter: fundamentals of dose dependence |
| VerfasserIn |
G. E. King, A. A. Finch, R. A. J. Robinson, D. E. Hole |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028054
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| Zusammenfassung |
| Quartz is widely used as a radiation dosimeter in Quaternary geomorphological and
archaeological dating applications through Optically Stimulated Luminescence (over 1,200
journal publications since 2000). However, obtaining an accurate equivalent radiation dose
(DE) can be challenging, especially where the luminescence intensity of the quartz is dim.
The causes of variation in luminescence intensity between quartz grains of different
provenances, transport and thermal histories is unknown, however it has been suggested that
it relates to either the dosimetric history of the grain, or mechanical processes which occur in
transit.
Investigation of the fundamental properties of the luminescence of quartz, enables
investigation of dose dependent changes in luminescence intensity. A series of dose
dependence experiments were conducted using spectroscopic ionoluminescence, which
comprises the excitation of quartz with protons accelerated at 0.95 MeV. The energy
delivered to the sample throughout ion implantation is similar to that received during gamma
irradiation, and thus approximates sample radiation dosing.
A natural macro-crystal of α-quartz was investigated parallel and perpendicular to c, to
observe any orientation dependent effects, as well as a calibration quartz from the
Risø National Laboratory, Denmark, and a Scottish geomorphological sample,
prepared using standard laboratory procedures. The calibration quartz sample has
excellent luminescence intensity and is suited to analysis using the single-aliquot
regenerative dose (SAR) standard OSL protocol, the Scottish sample alternatively
has very dim luminescence and exhibits variable behaviour when analysed with
SAR.
Despite the differences between the luminescence behaviour of the samples,
all three responded to the dose dependence experiments in a similar manner. The
UV/blue emission was observed to deplete with increasing dose, whereas the red
emission, not normally analysed within OSL, exhibited increased luminescence
intensity. The data provide insights into mechanisms that control the sensitivity
of quartz to OSL. Irradiation modifies the way that energy is distributed between
the various recombination pathways, notably favouring the red over the UV/blue.
Quartz that has experienced substantial irradiation over geological time, such as
Scottish quartz derived from the granite mountains of the Grampians, will luminesce
relatively dimly in the UV/blue. The total irradiation budget of the quartz from
formation to deposition to sampling is therefore encoded in its luminescence response. |
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