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

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

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

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

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

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

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

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

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?

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

Copper Samples

Copper Samples

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

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

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

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“

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

Preliminary Results

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

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

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

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 118.78 ± 68.50 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.)

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

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

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

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

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

Preliminary Results 232Th 238U 1.1 0.8 11 3

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

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