1. Application of AMS for the Analysis of
Primordial Nuclides in High Purity Copper
(A feasibility study)
G. Korschinek
N. Famulok, T. Faestermann, L. Fimiani, J.M. Gomez Guzman, K. Hain, P. Ludwig, S. Schönert

2. Motivation: Low Level Experiments
Certain dedicated experiments in modern physics require very low background
e.g. GERDA, CRESST
Passive shielding is made out of ultra-pure lead, steel or copper
But radionuclides of primordial,
cosmogenic and anthropogenic origin
Credit: MPI Heidelberg
Credit: cresst.de

3. Standard detection method: γ - Spectrometry
Activity of daughter nuclides measured by γ-spectrometry
Concentration of Th-232 and U-238 calculated assuming secular equilibrium

4. Motivation: Low Level Experiments
Many experiments in astroparticle physics require very low background
e.g. GERDA, CRESST
Passive shielding is made out of ultra-pure lead, steel or copper
But radionuclides of primordial,
cosmogenic and anthropogenic origin
Credit: MPI Heidelberg
Credit: cresst.de
Standard detection method: Gamma Spectrometry
Complementary approach: Accelerator Mass Spectrometry

5. γ – Spectrometry - accelerator mass spectrometry
Activity of daughter nuclides measured by γ-spectrometry
Concentration of Th-232 and U-238 calculated assuming secular equilibrium
is longsome to wait for the decay, Ra = Radium
Accelerator mass spectrometry (AMS)
determines directly Th-232 or U-238

6. Si surface barrier detector
AMS setup at the MLL
Si surface barrier detector
Sample
90° Injector Magnet
(1st Mass Separation)
18°Electrostatic Deflection
Carbon
Stripper
Foil
Wien
Filter
90° Analyzing Magnet
(2nd Mass Separation)
Switching Magnet
Negative
Ions
Positive
2.7m
TOF
Start −
Time-of-flight setup
(2.7m flight path)
Faraday Cup
Stop
MCP detector
Dedicated ion source for the detection of primordial nuclides in ultra-pure samples!
Ion identification:
TOF: ΔTOF ∼ 400ps
Energy signal
Cs reservoir
HV feed through
Ionizer
Sample

7. Zr transition metall, easy to process, can only be dissoluted in HF or aqua regia

8. Si surface barrier detector
AMS setup at the MLL
Si surface barrier detector
Sample
90° Injector Magnet
(1st Mass Separation)
18°Electrostatic Deflection
Carbon
Stripper
Foil
Wien
Filter
90° Analyzing Magnet
(2nd Mass Separation)
Switching Magnet
Negative
Ions
Positive
2.7m
TOF
Start −
Time-of-flight setup
(2.7m flight path)
Faraday Cup
Stop
MCP detector
Dedicated ion source for the detection of primordial nuclides in ultra-pure samples!
Ion identification:
TOF: ΔTOF ∼ 400ps
Energy signal
Cs reservoir
HV feed through
Ionizer
Sample

9. Motivation: Low Level Experiments
Many experiments in astroparticle physics require very low background
e.g. GERDA, CRESST
Passive shielding is made out of ultra-pure lead, steel or copper
But radionuclides of primordial,
cosmogenic and anthropogenic origin
Credit: MPI Heidelberg
Credit: cresst.de
Standard detection method: Gamma Spectrometry
Complementary approach: Accelerator Mass Spectrometry
No chemical treatment!
Blank level?
Extracted ion / molecule?

10. Copper Samples
Normal copper (5.6kg)
Laydown at the TUM
Physics Dep.

11. Copper Samples

12. Copper Samples

13. γ – spectrometry at the LNGS
Highly sensitive gamma spectrometry performed with GeMPI – detectors (μBq/kg range)
“Korrodin“ screws and LENS (Low Energy Neutrino Spectroscopy) copper screened by M. Laubenstein et al. 2010
Korrodin: Counts above background LENS: Upper limits
Radium, Protactinium

14. Measurement Principle
Calibration of detection system with 197Au beam
Calculation of region of interest for 232Th and 238U events

15. Measurement Principle
Calibration of detection system with 197Au beam
Calculation of Region of Interest for 232Th and 238U events
Th & U extracted as copper compounds ThCu- & UCu-
Good extraction efficiency and stable conditions

16. Measurement Principle
Calibration of detection system with 197Au beam
Calculation of Region of Interest for 232Th and 238U events
Th & U extracted as copper compounds ThCu- & UCu-
Good extraction efficiency and stable conditions
“Korrodin“ sample is used as standard
Unkown Th & U concentrations are determined relatively to “Korrodin“

17. Measurement Principle
Calibration of detection system with 197Au beam
Calculation of Region of Interest for 232Th and 238U events
Th & U extracted as copper compounds ThCu- & UCu-
Good extraction efficiency and stable conditions
“Korrodin“ sample is used as standard
Unkown Th & U concentrations are determined relatively to “Korrodin“
Faraday Cup 1
Cu current measured at Cup 1 to monitor performance of ion source
Th & U events normalized to this current for all samples

18. Preliminary Results

19. Preliminary Results Concentrations in μBq/kg: Thorium Korrodin
M-Copper
LENS
LNGS
945 ± 100 -
< 19
AMS
Standard
82 ± 35
59 ± 24
Uranium
Korrodin
M-Copper
LENS
LNGS
30 ± 7 -
< 16
AMS
Standard
2.1
1.0
+1.4
+1.1
-1.0
-0.8

20. Discussion and Outlook
AMS competitive with other detection methods
Much shorter measurement time and less samples mass than with gamma spectrometry
No chemical treatment required
Concentration values achieved: Uranium: ≤ 10 −14 g/g
Extension of concentration measurements

21. Thank you!
Zr transition metall, easy to process, can only be dissoluted in HF or aqua regia

23. A new Standard Sample: Blister Copper
Contaminants: Ni, Sb, Zn, As precious metals
High purity p-type
Ge detector
Th-232
8.38 ± 3.30 mBq/kg
(2.06 ± 0.81) · 10-9 g/g
± mBq/kg
(9.54 ± 5.50) · 10-9 g/g
Protaktinium, Telurium
preliminary!
Th-228 & Tl-208
Pa-234
Measured in Underground Laboratory in Garching (10 m.w.e.)

24. Zr transition metall, easy to process, can only be dissoluted in HF or aqua regia

25. Zr transition metall, easy to process, can only be dissoluted in HF or aqua regia

26. Si surface barrier detector
AMS setup at the MLL
Si surface barrier detector
Sample
90° Injector Magnet
(1st Mass Separation)
18°Electrostatic Deflection
Carbon
Stripper
Foil
Wien
Filter
90° Analyzing Magnet
(2nd Mass Separation)
Switching Magnet
Negative
Ions
Positive
2.7m
TOF
Start −
Time-of-flight setup
(2.7m flight path)
Faraday Cup
Stop
MCP detector
Dedicated ion source for the detection of primordial nuclides in ultra-pure samples!
Ion identification:
TOF: ΔTOF ∼ 400ps
Energy signal
Cs reservoir
HV feed through
Ionizer
Sample

27. Motivation: Low Level Experiments
Many experiments in astroparticle physics require very low background
e.g. GERDA, CRESST
Passive shielding is made out of ultra-pure lead, steel or copper
But radionuclides of primordial,
cosmogenic and anthropogenic origin
Credit: MPI Heidelberg
Credit: cresst.de
Standard detection method: Gamma Spectrometry

28. Natural Decay Chains
Zr transition metall, easy to process, can only be dissoluted in HF or aqua regia

29. Preliminary Results
232Th
238U
1.1
0.8 11 3

30. Discussion and Outlook
AMS competitive with other detection methods
Much shorter measurement time and samples mass than with gamma spectrometry
No chemical treatment required in contrast to NAA, ICP-MS
Very good concentration values achieved: Uranium: ≤ 10 −14 g/g
Extension of concentration measurements

31. Discussion Concentrations in μBq/kg: Thorium Korrodin M-Copper LENS
LNGS
945 ± 100 -
< 19
AMS
Standard
82 ± 35
59 ± 24
Uranium
Korrodin
M-Copper
LENS
LNGS
30 ± 7 -
< 16
AMS
Standard
2.1
1.0
+1.4
+1.1
-1.0
-0.8