A New Approach to Old Water: Atom-Trap Trace Analysis of Noble Gas - - PowerPoint PPT Presentation

A New Approach to Old Water: Atom-Trap Trace Analysis of Noble Gas Radionuclides

N.C. STURCHIO1*, R. YOKOCHI1,2, Z.-T. LU2,3, R. PURTSCHERT4

1University of Illinois at Chicago, Chicago, IL 60607, USA 2University of Chicago, Chicago, IL 60637, USA 3Argonne National Laboratory, Argonne, IL 60439, USA 4University of Bern, Switzerland

Noble gas radionuclides: Ideal tracers of residence time

85Kr 81Kr, 39Ar

Half-life (yr) Abundance

81Kr

229,000 10-12

85Kr

10.8 10-11

39Ar 296 10-15

Well-mixed

10 20 30 40 50 0.0 0.2 0.4 0.6 0.8 1.0

Isotopic Abundance Time (Years)

Solubility equilibrium

Noble Gas Radionuclides vs. Other Tracers

Half-life Atmospheric isotopic abundance Sources

85Kr

10.8 yr 2x10-11 Nuclear fuel reprocessing

39Ar

269 yr 8x10-16 Cosmic-ray induced reaction

81Kr

229,000 yr 1x10-12 Cosmic-ray induced reaction

Analytical Challenge of Noble Gas Radionuclides

Argon

How do you find 1 atom in 1015 atoms which all look very similar?

Isotope Abundance Half-Life 36 0.003336 Stable 38 0.000629 Stable 39 8.1 x 10-16 269 y 40 0.996 Stable

Example: 39Ar

The Three Methods: LLC, AMS, and ATTA

Low Level Counting (LLC) 35 meters below ground Underground laboratory in Bern, Switzerland

Detection Limit: ~4x10-17 Sample Size: ~0.3-1L STP Ar (1-3 Tons H2O) Time: 8-60 days Limiting Factors: Variation of environmental background

20 40 60 80 100 120 140 0.0 2.0x10

• 4

4.0x10

• 4

6.0x10

• 4

8.0x10

• 4

1.0x10

• 3

cpm channel no background sample

The Three Methods: LLC, AMS, and ATTA

Accelerator Mass Spectrometry (AMS)

• Ph. Collon et al. / Nucl. Instr. and Meth. In
• Phys. Res. B 223–224 (2004) 428–434

Detection Limit: ~4.3x10-17 Sample Size: ~2mL STP Ar (2L H2O) Time: ~8 hours Limiting Factors: Accelerator based Background from 39K

4p[5/2]3 4s[3/2]2 3p6 Ground-level Metastable 811 nm 11 eV electron collision Chen et al. Science 286, 1139 (1999)

• Based on Selectivity of Magneto-Optical Trap (MOT)
• Long observation time -- 100 ms
• High loading rates -- 109-1012 s-1 for 38Ar
• Narrow linewidth
• Spatial confinement -- trap size < 1 mm
• Extremely high selectivity statistics limited
• Background from scattered laser light

The Three Methods: LLC, AMS, and ATTA

Atom Trap Trace Analysis (ATTA)

Atom-Trap Trace Analysis (ATTA-2) @ 2003

10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 Efficiency 107 106 105 104 103 102 10 1

Water or Ice Sample Size (L)

Groundwater Polar Ice

LLC 1969 AMS 1997 ATTA-1 1999 ATTA-2 2003 ATTA-3 2008 (projected)

10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 Efficiency 107 106 105 104 103 102 10 1

Water or Ice Sample Size (L)

10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 Efficiency 107 106 105 104 103 102 10 1

Water or Ice Sample Size (L)

Groundwater Polar Ice

LLC 1969 AMS 1997 ATTA-1 1999 ATTA-2 2003 ATTA-3 2008 (projected)

Only 1000 liters for

81Kr in groundwater !

ATTA-1: Chen et al., Science (1999) ATTA-2: Du et al., Geophys. Res. Lett. (2003)

5p[5/2]3 5s[3/2]2 4p6 Ground-level Kr atom Metastable t40 sec 811 nm 10 eV electron collision Kr atom excitation and trapping scheme (Chen et al., SCIENCE, 1999)

• 1000
• 800
• 600
• 400
• 200

200 0.0 0.1 0.2 0.3

84Kr 81Kr 85Kr 86Kr 82Kr 78Kr 80Kr 83Kr

Trap Fluo. (arb. unit)

0.0 0.2 0.4 0.6 0.8 1.0

83Kr

Trap Fluo.(arb. units)

• 150
• 120
• 90
• 60
• 30

30 60 90 5 10 15 20 25 30 35

(0.5 hrs.)

85Kr

81Kr (3 hrs.)

Atom Counts Frequency Offset (MHz)

Counting 81Kr and 85Kr with ATTA

0.0 0.5 1.0 1.5 2.0 2.5 5 10 15 20 25 Background One Atom 81Kr

Photon Scattering Rate (kHz) Time (sec)

1 2 3 4 5 5 10 15 20 81Kr

Photon Scatt. Rate (kHz) Time (min.)

5 10 15 20 25 5 10 15 20 25 One Atom Background 83Kr

Fluorescence (kHz) Time (sec)

Single Atom Detection!

First application of ATTA in hydrology: Nubian Aquifer, Egypt (2003)

50 100 150 500 1000 1500 2000

81

Kr age (kyr)

36

Cl/Cl (x 10

• 15

)

Bauti 1 Sherka 36 Baris(Aden) El Zayat 12 Farafra 6 Gum Horia

First application of ATTA in hydrology: Nubian Aquifer, Egypt (2003)

(Sturchio et al., GRL, 2004; Patterson et al., G3, 2005)

10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 Efficiency 107 106 105 104 103 102 10 1

Water or Ice Sample Size (L)

Groundwater Polar Ice

LLC 1969 AMS 1997 ATTA-1 1999 ATTA-2 2003 ATTA-3 2008 (projected)

10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 Efficiency 107 106 105 104 103 102 10 1

Water or Ice Sample Size (L)

10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 Efficiency 107 106 105 104 103 102 10 1

Water or Ice Sample Size (L)

Groundwater Polar Ice

LLC 1969 AMS 1997 ATTA-1 1999 ATTA-2 2003 ATTA-3 2008 (projected)

We’re there!!!

What’s new?

ATTA-3!!!

1 2 3 4 5 6 7 8 9 10 1 10 100 1000 1 10 100 1000

85Kr measured (dpm/cc Kr) 85Kr Mixed (dpm/cc Kr)

for 81Kr:

Discharge Source Transverse Cooling Beam Chopper 2D Focusing Zeeman Slower MOT CCD Camera

Loading Rate Improvements in ATTA-3

Atomic Beam Stage ATTA II ATTA III Enhancement  LN2 pre-cooling N.A. x 2 x 2  Transverse Cooling 70 x 140 x 2  Sidebands in T.C. N.A. x 3 x 3  2D-MOT N.A. x 3 x 3  New Zeeman Slower x1000 x 3000 x 3  More Trapping Power N.A. x 1.5 x 1.5

x 160

0.5mm 0.5mm

What else is new? 39Ar atom counting!!!

Single Atom Counting of 39Ar

I.A. = 0.064%

Experiment 1: Frequency Switching Results

Laser Detuning Expect to See 39Ar ? Measured (in 57 hrs)

• 20 MHz

No

• 6 MHz

Yes 12 +10 MHz No

1

Experiment 2: 39Ar in air and groundwater

Jiang et al., PRL 106, 103001 (2011) atmospheric Ar groundwater Ar

Summary

• ATTA-3: enhancement of efficiency by a factor of 160
• Reduced sample size requirement (10-100 L of H2O)
• Faster counting times
• Improved precision (better than +/- 5%)
• First 39Ar measurement of Ar from groundwater
• The next generation ATTA is here, opening opportunities for new

and exciting applications (to be presented in future talks)