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Experiments towards the Efficient Trapping of Francium by Seth Aubin Parity Violation in Francium Group Students: Eduardo Gomez Joshua M. Grossman Professors: Luis A. Orozco Gene D. Sprouse
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A Brief History of Francium at Stony Brook 1991-94: Construction of 1 st production and trapping apparatus. 1995: Produced and Trapped Francium in a MOT. 1996-2000: Laser spectroscopy of Francium (8S 1/2, 7P 1/2,7D 5/2,7D 3/2, hyperfine anomaly). 2000-2002: construction of new production and trapping apparatus. 10,000 atom Fr MOT
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New Apparatus for Producing and Trapping Francium Objective: Trap 10 6 Fr atoms Parity Non-Conservation experiments Nuclear Anapole measurements Strategy: Increase Production Optimize Optical Trapping efficiency Improve Neutralizer efficiency
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Schematic of New Apparatus
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Improved Production 16 O, 18 O, 19 F ~100 MeV Fr + ions Au, Pt target Improved Fr + ion extraction New target design Heated tungsten rod
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Optical Trapping Efficiency 1. Capture Velocity of MOT Idea: Accelerate MOT atoms with laser. Measure at what velocity atoms cannot be recaptured by MOT. b. Velocity Calibration: a. Description atom cloud on resonance laser push
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c. Capture Velocity (lower bound): ~18 m/s
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MOT 1 mm
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Displaced MOT (External B-field) Laser push 1 mm
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2. Number of Bounces (N bounces ) Atoms rethermalize with cell walls on each bounce. N MOT N bounces. N bounces is determined by exit holes, quality of dry-film coating. Dry-Film (SC-77) test: 780 nm laser probe Rb atomic beam shutter fast detector
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Monte-Carlo simulations decay time of 5.2 ms (~100 bounces)
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Comparison of Neutralizer Materials (at 5 KeV) ~ 300 Celsius
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Conclusion New apparatus for trapping 10 6 Fr atoms. Increased Fr production by a factor of 15. Studied neutralization process. Probes of capture velocity and coating quality. Capture velocity of at least 18 m/s. Just converted apparatus to Francium.
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