1. JLab FEL – Opportunity for a New Generation of Ultrasensitive Trace Analyzer of Noble Gas Isotopes
Zheng-Tian Lu
Physics Division, Argonne National Laboratory
Department of Physics, University of Chicago
Supported by
Department of Energy, Office of Nuclear Physics
National Science Foundation, Earth Science Division

2. Atmospheric isotopic abundance
Nobel Gas 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
6x10-13 2

3. Radio-Krypton Dating 81Kr (t1/2 = 230kyr, I.A.= 6 x 10-13) Cosmic p, n
83Kr, 82Kr...
81Kr
Cosmic
p, n
81Kr (t1/2 = 230kyr, I.A.= 6 x 10-13)
Polar Ice as a natural archive
temperature
precipitation
gas composition
volcanic eruption
solar variability...
Number of 81Kr atoms in 1 liter of :
Air  20,000
Water  1,000
Ice  1,000

4. Accelerator Mass Spectrometry of Kr-81
W. Kutschera et al., NIM B29, 241 (1994); P. Collon et al., NIM B123, 122 (1997)
Full stripping at high energy (~ 4 GeV) for isobar separation: 81Kr36+ vs. 81Br35+.
National Superconducting Cyclotron Laboratory
Michigan State University
First 81Kr dating: groundwater in GAB
-- P. Collon et al., EPSL 182, 103 (2000)

5. Methods of Trace-Isotope Analysis at PPT Level
LLC – Low Level Decay Counting
Willard Libby, Science (1949)
AMS – Accelerator Mass Spectrometry
R. A. Muller, Science (1977)
Nelson et al., Science (1977)
Bennett et al., Science (1977)
ATTA – Atom Trap Trace Analysis
Chen et al. Science (1999)
AMS
Muller, Physics Today
ATTA

6. Laser Trapping and Cooling - a quick primer
Neutral Atom Trap
Sodium, NIST

7. 1997 Nobel Physics Laureates
Steve Chu
Claude
Cohen-Tannoudji
William Phillips
"for development of methods to cool and trap atoms with laser light"

8. Atom Trap Trace Analysis of Krypton
Ground-level
Metastable t » 40 sec
811 nm
10 eV
electron collision
Discharge
Source
Transverse
Cooling
Beam
Chopper 2D
Focusing
Zeeman Slower
MOT
CCD
Camera

9. Single Atom Detection <Single atom signal> = 1600 counts
<Background> = 340  30 counts

10. Counting 81Kr and 85Kr

11. One Million Years of Nubian Aquifer Groundwater History
Groundwater at six sites dated;
Flow direction and speed measured;
Source determined.
333±44 kyr
212±42 kyr
391±46 kyr
488±45 kyr
678±75 kyr
Uweinat
Uplift
Sturchio et al., Geophys. Res. Lett. (2004)

12. 81Kr Dating: From Dream to Practice
Polar Ice
Groundwater
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
Water or Ice
Sample Size (L)
LLC
1969
ATTA-1
1999
AMS
1997
ATTA-2
2003
ATTA-3
2011
ATTA-4
JLab FEL
Present Status of ATTA-3:
Selectivity requirement: Done;
Efficiency requirements: Practical, but far from perfection
ATTA-1: Chen et al., Science (1999)
ATTA-2: Du et al., Geophys. Res. Lett. (2003)
ATTA-3: Jiang et al., Phys. Rev. Lett. (2011)

13. ATTA-4 with JLab FEL
Optical production of Kr* via two-photon excitation:
124 nm nm
Young et al., J. Phys. B (2002)
Ding et al. RSI (2007)
5s[3/2]02
4p6
Ground
Metastable
5p[3/2]2
124 nm
5s[3/2]01
819 nm
Advantages over the existing RF discharge method:
Improve efficiency
Metastable production efficiency
Collimate atomic beam
Reduce sample loss and contamination
Proposal to determine two-photon excitation rate in Summer, 2011
Zheng-Tian Lu, William Williams (Argonne)
Charles Sukenik, Grady White (ODU)
Gwyn Williams, Michelle Shinn et al. (JLab)

14. ATTA Team Argonne Atom Trappers
Kevin Bailey
Wei Jiang
Zheng-Tian Lu
Peter Mueller
Tom O’Connor
Will Williams
Argonne Atom Trappers 14

15. Collaborators Neil C. Sturchio University of Illinois at Chicago
Andrew M. Davis University of Chicago
L. Young & R. Dunford Chemistry Division, Argonne
Shuiming Hu University of Science & Technology of China
B. Mack Kennedy Lawrence Berkeley National Lab
Roland Purtschert University of Bern
Charles Sukenik Old Dominion University