ApplicationApplication ofof thethe threethree photomultiplierphotomultiplierliquidliquid spectrometerspectrometer HIDEX 300SL HIDEX 300SL

for for radiocarbonradiocarbon datingdatingMarek Krąpiec1,2, Adam Michczyński3, Adam Walanus1

1 Faculty of Geology, Geophysics and Environmental Protection, AGH-University of Science andTechnology, Al. Mickiewicza 30, 30-059 Kraków, Poland2 Laboratory of Absolute Dating, Cianowice 225, 32-043 Skała, Poland3 Gliwice Radiocarbon Laboratory, GADAM Centre of Excellence, Institute of Physics, SilesianUniversity of Technology, Krzywoustego 2, 44-100 Gliwice, Poland

adamwalanus.pl laboratorium@c14.pl www.c14.pl

50eV 156eV

14C

T1/2 = 5730 years biosphere: 226 Bq/kgC = 13 dpm/gC

-> T=25 ka -> 13*2-25/5.73 = 0.63 dpm/gC

-> counting time = 2 days -> 1800 d/gC

Poissonian error = 18001/2/1800 = 2.3%

Medieval sample: 1260-1390 AD -> 14 h -> 10000 d/gC -> 1%

0.36% -> ± 30 years

Venu

sof

Bras

sem

pouy

Two Multichannel Analysers, each with 1024 channels

• Quench correction via three methods:

1. TDCR – Triple to double coincidence ratio2. Using a known quench curve

3. An external standard (Eu-152; ~ 440 kBq)

• Alpha / Beta separation based on pulse length discrim.

• Automatic Luminescence Reduction

HIDEX 300SL

Width: 520 mm Height: 685 mmDepth: 630 mm Weight: 130 kg

Threephotomultipliertubes

TDCR Triple to double coincidence ratio

The TDCR method is an absolute activity measurement method specially developed for pure beta-and pure EC-emitters activity determination, in which the detection efficiency is calculated from a physical and statistical model of the photon distribution emitted by the scintillating source.Source: Laboratoire National Henri Becquerel

Sample - BFm =

StandardModern - B

14C dating –

relative activity measurement:

0.80

0.60

0.80

0.60

Effic

ienc

y

Effic

ienc

y

Sample - BFm =

StandardModern - BSample - B

<< 1Sample

14C dating – old samples are close to background:

2

3

Empty vial

No 14C sample

Amount of impurity (chlorophorm drops)

Stan

dard

ized

valu

eB double(cpm)

B triple

TDCR 14C

TDCR

14C

14C age calibration

S = 501% of modern 14C

<- 0 yr BP Before Present

<- 1500 yr BP

<- 3000 yr BP

30 kyr BP

14C lower (and upper) discriminationlevel, choosen to obtain good S/N ratio

(factor of merit FOM=s/b1/2, maximum determinable age),

and to obtain the correct age ->

Two samples ofslightly different purity

Standards, one pure and sixwith the quencing agent (chlorophorm) added

Model: sigmoid

Sigmoid function: y=1-1/(1+e-x)

y=b+a*(1-1/(1+exp(-(x-xH)/xd)))

a

b

Xd - slope

xH

s = linear interpolant between s1 and s2

<- 6, 4, 2, 0

Av = -0.34 ± 0.27 yr, p=0.10; StDev of norm. = 1.24 ± 0.15, p=0.055;

Shapiro Wilk normality test: p=0.25

14C

dend

ro–

14C

mea

sure

d(y

r)