"Working conditions - Tl-authentication"

Tl-systems:
Littlemore - TL 711;
Littlemore-Elsec TL-7188; Daybreak OSL
2 Daybreak TL 1150; 1 Daybreak 1100
Alpha-Counter Littlemore 7286
2 Alpha- and Beta Multiple Sample Irradiater
Littlemore and Daybreak

Filter:
Corning 7-59 / 5-60 ; Schott BG-39

ß-Source
Sr 90 40 mCi 101,623 cGy /min 01.01.1992
a-Source
CM-244 Curium 0,5 mCi

Working method:
Fine grain sedimentation following treatment in diluted hydrochloric acid.
Grain size fraction following repeated sedimentation 2-10/10-50 micro m.
Measurements are carried out in an ultra- pure nitrogen atmosphere of at
least 4.6 N2 following a previous vacuum of 0,150 mbar.
Regeneration and addition method. (Pre-dose technique )

Result:
Provides a statement on the last time of firing. The age specification
contained in the Tl expertise refers to the so-called "firing age" of the
sample(s) (minerals), i.e. to the time at which they were last heated to a
temperature of over 500 degrees C , and mentions the place on the object
from which the sample (s) was / were taken .Tl measurements to specify
age can be falsified if objects have been subjected to high X and Y radiation
doses or neutron bombardment. X-radiation , for example during the course
of baggage controls , is no significance. ( Error factor under 0,1 % )
The TL-Report do not provide on the investigation of polymers
(synthetic and natural resins) of all kinds.

Sampling:
Samples are taken using a carbide drill (diameter 1,4 -2mm) at
low speed following previous removal of the surface. Samples must be taken
not under a strong incidence of light .As a rule, two samples are taken from
each test specimen , which are subjected to two seperate Tl analyses, in
each case specifying the drilling position.
The sample quantities are minimal (50 - 200 mg). If major restoration work
is discovered in one of the objects to be tested , the Tl expertise carries the
appropriate reference.

Photos:
The laboratory requires two photos for the compilation of a Tl expertise .
The laboratory guarantees strict confidentiality in the processing of
Tl-analyses and the compilation of Tl expertises . Expertises are printed out
with out specifying the name of the commissioning party.