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QUALITY TESTS AMS

 

The quality of our product has been tested in several ways. Precision of the first AMS spectrometer (Compact Carbon AMS ser. no. 003) was tested on modern samples in  the NEC factory and after installation in Poznań. In September 2003 we significantly reduced the background of that spectrometer. Precision of the second spectrometer (Compact Carbon AMS ser. no. 012) was tested on modern standards and on background samples after installation of the spectrometer in Poznan. We also compared results of 14C measurements performed with our two spectrometers.


  Compact Carbon AMS 003 - factory test results

Precision of our AMS machine has been tested in NEC by AMS 14C measurements of three cathodes prepared from the same sample (ANU sucrose standard). The results below show excellent reproducibility of 13C/12C and 14C/12C measurements

Cathode

Time (s)

14C counts

13C/12C

14C/12C

ANU
500
136558
1.1025e-2
1.3772e-12
ANU
500
140410
1.1019e-2
1.3791e-12
ANU
500
131027
1.1017e-2
1.3775e-12
Precision of single measurement
0.4 permil
0,1 percent



Compact Carbon AMS 003 - acceptance test results

Precision of the machine in our Laboratory has been tested by AMS 14C measurements of three cathodes prepared from the same sample (OXII standard) and provided by NEC. The results below show excellent reproducibility of 13C/12C and 14C/12C measurements

Cathode

Time (s)

14C counts 

13C/12C

14C/12C
OxII
750
177833
1.0694e-2
1.3289e-12
OxII
750
194300
1.0716e-2
1.3313e-12
OxII
750
146583
1.0694e-2
1.3346e-12
Precisin of single measurement
0.12 permil
0.28 percent



Compact Carbon AMS 003 - reduction of the machine backgroud

A simple way of background reduction in the "Compact Carbon AMS" spectrometer has been proposed by J. Southon (Irvine, California, USA). Application of this discovery in Poznań reduced our machine background by a factor of 2-3. At present, this background corresponds to a 14C age > 60000 BP

Date

Current (μA)

14C counts  (2.5 min)
14C (pMC)
Age 14C
Before modification
01-05-2003
12.8
20
0.159
51800
01-05-2003
13.0
19
0.148
52300
01-05-2003
13.2
11
0.085
56800
01-05-2003
13.7
9
0.067
58700
01-05-2003
11.3
16
0.144
52600
01-05-2003
13.8
14
0.103
55200
01-05-2003
137
18
0.133
53200
01-05-2003
13.5
11
0.083
57000
05-05-2003
12.8
17
0.135
53100
05-05-2003
13.9
8
0.059
59800
05-05-2003
14.1
13
0.093
56000
05-05-2003
13.2
19
0.146
52500
05-05-2003
13.4
13
0.098
55600
05-05-2003
10.3
10
0.098
55600
         
  After modification
24-09-2003
17.5
3
0.018
69200
24-09-2003
17.5
6
0.035
63900
24-09-2003
17.5
3
0.018
69200
03-10-2003
15.7
6
0.039
63100
03-10-2003
15.8
7
0.046
61800
03-10-2003
15.7
5
0.032
64600
20-10-2003
12.0
5
0.042
62500
27-10-2003
18.6
6
0.033
64300
30-10-2003
11.2
7
0.055
60300
06-11-2003
16.4
5
0.031
64800
17-11-2003
21.5
7
0.034
64100
23-11-2003
20.6
7
0.036
63700
26-11-2003
19.5
11
0.056
60100
15-12-2003
19.2
8
0.043
62300

The background tests were made using aliquots of 14C-free commercial graphite (Alfa-graphite), kindly supplied by the Leibniz-Labor für Altersbestimmung, Kiel, Germany.  



Compact Carbon AMS 012 - acceptance tests

Precision of the spectrometer was tested after its installation in our Laboratory, by 14C measurements on three portions of graphite prepared from the sample of modern standard (Oxalic Acid II).

Sample

Time (s)

Counts 14

13C/12C

14C/12C*
OxII
600
169078
1.1050e-2
1.4711e-12
OxII
600
172851
1.1049e-2
1.4669e-12
OxII
600
137709
1.0940e-2
1.4661e-12
Precision of single graphite measurement
0.6 per mil
0.26 percent
* - values corrected for isotopic fractionation, basing on the measured ratios 13C/12C



Compact Carbon AMS 012 - background

Background of the spectrometer was measured using commercially produced graphite (alfa-graphite). Additionally, we performed measurements on graphites prepared in the laboratory from the milligram-size samples of coal

Sample

  Time (s)

Counts 14C
14C (pMC)
Age 14C
Alfa-graphite
900
37
0.029
65400
Coal
900
213
0.175
51000
Coal
900
426
0.228
48900



Test dating - comparison of results obtained with our two spectrometers

  The tests indicated good agreement of 14C dates obtained with the two spectrometers

 
CAMS 003 (BP)
CAMS 012 (BP)
Difference
Diff./error
1
  660±25
650±24
10
0,28
2
  4525±30
4583±34
57
-1,26
3
  560±30
608±26
-48
-1,21
4
  17270±80
17292±84
-22
-0,19
5
  110±30
 149±25
-39
-0,99
6
  12020±60
11976±55
44
0,54
7
  8245±35
 8247±33
-2
-0,04
8
  -549±28
-515±26
-34
-0,89
9
  5420±40
5350±26
70
1,47
10
  5335±35
5327±26
8
0,18
11
 2715±30
2707±23
8
0,21



Our precision of 14C dating depends also on the quality of sample preparation in the Poznań Radiocarbon Laboratory

 

 

See the results of the sample preparation tests:

point2.png Preparation test results - background
point2.png Preparation test results - standard
point2.png Preparation test results - charcoal 
point2.png Preparation test results - samples of known age
point2.png Typical precision of our 14C dates
 
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