a search for temporal and gravitational variation of in atomic dysprosium variation of constants...
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![Page 1: A Search for Temporal and Gravitational Variation of in Atomic Dysprosium Variation of Constants & Violation of Symmetries, 24 July 2010 Arman Cingöz](https://reader036.vdocuments.site/reader036/viewer/2022081519/56649d5d5503460f94a3ce96/html5/thumbnails/1.jpg)
A Search for Temporal and Gravitational Variation of in Atomic
Dysprosium
Variation of Constants & Violation of Symmetries, 24 July 2010
Arman Cingöz
JILA/NIST Boulder, CO
Partial support by:
University of Californiaat Berkeley
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CoworkersDmitry Budker, Nathan Leefer
Physics Department, University of California, Berkeley
Steve Lamoreaux Yale University
Alain Lapierre TRIUMF, Canada
A.-T. NguyenUniversity of Pittsburgh
Justin Torgerson Los Alamos National Laboratory
Valeriy Yashchuk and Sarah FerrellLawrence Berkeley National Laboratory
Collaborators
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Outline
• Overview & motivation• Nearly degenerate levels in dysprosium• Experimental technique• Variation Results/ Status Update• Laser Cooling of Dy
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Overview
• Variation of a would signify physics beyond the Standard Model and General Relativity.
• Violates Local Position Invariance (a component of Equivalence Principle), which states that results of non-gravitational experiments are independent of where and when they are performed
• WHEN: Temporal variation of fundamental constants:
V. Dzuba et. al., Phys. Rev A 68, 022506 (2003) V. Dzuba and V. V. Flambaum, Phys. Rev A 77, 012515 (2008)
• WHERE: Null gravitational redshift experiment: compare two different clocks side by side at the same location
• Recast species dependent shift in terms of gravitational variation of
V. V. Flambaum, Int. J. Mod. Phys. A22, 4937 (2007)
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Search in Atomic Dy
•Atomic dysprosium (Dy, Z=66) has two nearly degenerate levels that are highly sensitive to
A B
3 MHz – 1 GHz
transitions in 5 isotopes
(t)
d/dt ~2.0 x 1015 Hz ||Ÿ
V. Dzuba et al, Phys. Rev A 77, 012515 (2008)
Ÿ•For |/| ~ 10-15 /yr d/dt ~ 2 Hz/yr
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Self-heterodyning Optical Comparison
• Opposite parity levels can induce direct electric dipole transitions
between levels
• E ~ 3-1000 MHz can induce transitions with an rf electric field
• Direct frequency counting relaxed requirements on reference
clock [E=1 GHz requires ~10-12 for a mHz measurement (|| ~ 10-18 /yr )]
• Essentially independent of other fundamental constants
1
2
1 - 2A
B
G
Ÿ
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Statistical Sensitivity
• Transition linewidth, , is determined by the lifetime of
state A ( =7.9 s) ~20 kHz
• Counting rate ~ 109 s-1
• Statistical sensitivity:
~ /N1/2 ~ 0.6 Hz s1/2
T1/2
After 1 hour of integration time, ~10 mHz which correspondsto a sensitivity of:
|| ~ 5 x 10-18 yr-1 Ÿ
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Additional Correlations
1 + 2 insensitive to variation
A
A
B
B
Currently we monitor:3.1-MHz transition in 163Dy235-MHz transition in 162Dy
1 - 2 variation is twice as large
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Parity Nonconservation in Dy
• Degeneracy between levels A and B useful for enhancing mixing
due to the weak interactions
• Detect quantum interference beat between Stark and PNC mixing|Hw|=|2.3 ± 2.9 (stat) ± 0.7 (sys)| HzA. T. Nguyen et al., PRA 56, 3453 (1997)
• Theoretical calculations are difficult since dominant configurations
do not mix; effect due to configuration mixing and core polarizationHw=70 (40) HzV. A. Dzuba et al., PRA 50, 3812 (1994)
• Recently, improved calculations suggest Hw ~ 2-6 HzV. A. Dzuba and V. V. Flambaum, PRA 81, 052515 (2010)
• Stay tuned for CW PNC experiment with improved statistical sensitivity
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Population
833 nm
669 nm
1397 nm
3 step population scheme:
Step 1 and 2: cw laser excitation Step 3: spontaneous decay with b.r. ~30%
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Detection
RF
4829 nm
564 nm
• FM modulated rf field transfers population to state A• State A decays to the ground state in two steps• 564-nm light is detected
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First Generation Apparatus Results
(-2.4 ± 2.3) x 10-15 yr-1 A.Cingöz et al., PRL 98, 040801 (2007).
k=(-8.7 ± 6.6) x 10-6 S. Ferrell et al., PRA 76, 062104 (2007)
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2nd Generation Apparatus
Differentially pumped chambers
1. Oven chamber2. Gate valve3. Interaction
chamber
2
3
A C
D
F
E
G
1
B
A. Dy effusive ovenB. CollimatorC. Laser access portD. Two-layer magnetic shieldE. 4 Optical collection
systemF. PMT viewportG. Rf electrodes
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Current Status• Operational for the past two years
• Collisional shifts reduced to ~ 10 mHz
• Shifts due to rf inhomogeneities
consistent with 0 at the 10 mHz level
• However there were unexpected
problems:
• DC Stark shifts due to stray
charge accumulation: problem
mostly for 3.1 MHz transition
• Zeeman shifts:
/B=gABomFmax~2 kHz/1mG
(-0.8 ± 2.1) x 10-15 yr-1.
• Zeeman shifts under control at the ~0.1
Hz level
• Stray electric fields mostly stabilized but
need further investigation
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Future: Residual Amplitude Modulation
• RAM on top of FM creates asymmetric sideband amplitudes which leads to apparent shift of zero crossing for 1st harmonic
• Due to the large linewidth, RAM is a serious problem
~450 Hz/% RAM
• Measured value in our system ~1 x 10-4 4 Hz shifts
•Various ways to control:• Choose proper phase angle•Active stabilization
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Laser Cooling of Dy
• Increase beam brightness
• A better control of beam density
Study self collisions
Reduce systematics due to
spatial inhomogeneities
•A strong cycling transition exists
421 nm ( = 4.6 ns)
• However, many decay channels
• Calculations suggested B.R. of <10-4
V. A. Dzuba and V. V. Flambaum, PRA 81, 052515 (2010)
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Laser Cooling of Dy
• 421 nm source: 1cm PPKTP in a bow tie cavity
90 mW out with 335 mW IR, 27% c.e.
• Transverse cooling experiment:
• 3 cm interaction region: ~5000 cycles
• Probe velocity distribution w/ 658 nm transition 658 nm
421 nm
• Limit on branching ratio: < 5 x 10-4
• More stringent limit from MOT experiment in Urbana-Champaign: 7 x 10-6
M. Lu et al., PRL 104, 063001 (2010)N. Leefer et al., PRA 81, 043427 (2010)
Rec. vel. 0.6 cm/sDoppler limit 20 cm/sDoppler temp. 0.8 mK
•Fit to Voigt Profile:
• Gaussian width of 0.8(5) MHz
• Lorentzian width of 4.2 (7) MHz
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Conclusion• The nearly degenerate levels in dysprosium are highly sensitive to variation. Direct frequency counting techniques allow for measurements without state-of-the-art atomic clocks.
• First generation apparatus sensitivity is ~10-15 yr-1
• Second generation apparatus sensitivity is expected to be ~10 -17 yr-1. Actual data taking will commence soon.
• Transverse cooling of Dy to the Doppler limit has been demonstrated for all isotopes with large abundance.• XUV Frequency Combs: Monday Poster Session (Mo 89)
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A.- T. Nguyen et al. PRA Phys. Rev. A 69, 022105 (2004)
Systematic Effects
• However, it is not the size but the stability of these effects that is important
preliminary analysis showed that systematic effects may be controlled to
a level corresponding to |/| ~ 5 x 10-18 /yr.
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Search in Atomic Dy
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Lock-in Detection Technique
• rf field is frequency modulated at 10 kHz with a modulation index of 1• Reduces asymmetries in the line shape caused by drifts (laser and atomic beam fluctuations)• Currently use the ratio of these two harmonics
Second HarmonicFirst Harmonic
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Laser Cooling of Dy
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Stray B-fields• If unresolved Zeeman sublevels are:
sym. populated leads to broadening , but no shifts
asym. populated leads to broadening and shifts
/B=gABomFmax~2 kHz/1mG
• Nominal config.: linearly polarized pop. beams aligned state; no shifts
• Systematic due to: spatially varying stress-induced birefringence on optics.
run-to-run variations due to laser pointing variations.
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Standing Wave Small radiative losses
(closed wave guide) Impedance matched Transparent to light Transparent to the
atomic beam Homogeneous electric
field (no phase shifts) Broadband: 3 MHz
to 1 GHz
RF Interaction Region
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RF Interaction Region