Search for the Electron Electric Dipole Moment Val Prasad Yale University Experiment: D.DeMille, D. Kawall, R.Paolino, V. Prasad F. Bay, S. Bickman, P.Hamilton, Y. Jiang, Y.Gurevich Yale University L.R.Hunter (Amherst) Theory: M. Kozlov (PNPI, St. Petersburg), D. DeMille
29
Embed
Search for the Electron Electric Dipole Moment Val Prasad Yale University Experiment: D.DeMille, D. Kawall, R.Paolino, V. Prasad F. Bay, S. Bickman, P.Hamilton,
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Search for the Electron Electric Dipole Moment
Val Prasad
Yale UniversityExperiment:
D.DeMille, D. Kawall, R.Paolino, V. Prasad
F. Bay, S. Bickman, P.Hamilton,
Y. Jiang, Y.Gurevich
Yale University
L.R.Hunter (Amherst)
Theory:
M. Kozlov (PNPI, St. Petersburg),
D. DeMille
An EDM Violates Parity and Time Reversal Symmetries and may provide evidence of
Quantum Beats• Coherent superposition of two states decaying to
the same state• Precession frequency proportional to energy
difference between states• Allows for Doppler free, very precise
spectroscopy (<1mHz)
x
y
Present Experimental Setup
Photomultiplier tube
Si gnal
Frequency
Solid quartz light pipes
DataProcessing
integral
Vacuum chamber
Fourier Transform
PbO vapor Cell
B
•A specialized oven to heat a novel vapor cell to temperatures of 700°C•The cell contains about 80cm3 of PbO vapor of natural isotopic abundance •Vacuum chamber surrounded by 3 orthogonal Helmholtz coils•Use Nd:YAG pumped dye laser at 570nm, 5-40 mJ /pulse, 1 GHz linewidth•Excite X(0)a(1) transition and detect quantum beat fluorescence signal•Analyze beat frequency•Perform reversal of E field, B field or RF transition to measure dipole induced frequency shift
PbO Vapor Cell
Main electrode
Guard ring
Sapphire window
•Re-entrant electrodes for homogeneous E field•Flat windows to reduce scattered light and birefringence•Larger volume to reduce wall quenching
Quartz Oven•Can withstand repeated thermal cycling to 800°C•~1300 W of power used•Excellent Temperature stability •wide optical access•low-inductance heater for fast switching
Magnetic Shield
Winston Cone
Quartz Oven Parts
Peripherals To EDM Experiment
Systematics Considerations
• Motional Magnetic Fields
• Magnetic Noise
• Leakage Currents
• Multi-photon ionization
• E-field gradients
• Inhomogeneities in E-field
• Stray B-fields and E-fields
B EBrf
B EBrf
B EBrfB EBrf
Ћ rf ΔEstark
Ћ rf ΔEstark
+ ΔE -doublet
E reversal
Frequency for de=0
Frequency for de≠0
Dashed-line energy levels show Zeeman shifts. Dotted-line levels show the additional linear Stark shift which would arise from a non-zero EDM.
-doublet levels = comagnetometer: Most systematics cancel in comparison
rf tuning adds NEWreversal to the EDM measurement
EDM Measurement in PbO*New mechanisms for suppressing systematics!
g-factor measurement
Results help constrain calculation of enhancement-factor
008.0857.1 : and 0.0081.860 :
gJgJ
ideal) 0g
g ( 0.002
g
g
g
g
g -doublet useful as Co-Magnetometer
To what extent is the - doublet a perfect mirror image?
1X10-27e.cm corresponds to beat frequency shift 10-25mHz
Straightforward modification to improve sensitivity to
Two photodiodes with high quantum efficiency instead of single PMTExcite from X(0)(v”=0) instead of X(0)(v”=1)Use broader band interference filtersUse isotopic enriched 208PbO…
Expect to increase the count rate by more than three orders of magnitude, and the contrast by more than a factor of two
Current Sensitivity
The necessary modifications are now underway
1X10-29e·cm corresponds to 100-240μHz T < 106s
Two orders of magnitude improvement on de in ~10days
Average for T=25s
100mHz / Hz
100mHz 120mHz
Hz Tv
Conclusions
• Many preliminary steps have been successfully demonstrated
• Improvements in excitation and detection efficiencies look promising
• Attacking a few remaining experimental issues before we take a first look at the data …………….
Density determined by collisional quenchingAdjust PbO density so excited state decay rate ~collisional quenching rate1/ a(1) ~σnv, where a(1) ~ 80 μsMeasured σ~10-14cm2 n=3x1013cm-3 P=0.3mTorr T=690oC v=3x104cm/s
Minimum cell size determined by wall quenchingv x a(1) < L L~5cm
Density and cell size determine number of molecules in usable rovibrational state
f~B/kBT~0.3cm-1/670cm-1 3x10-4
S/ N estimated from laser power, cross sectionNumber of molecules excited/pulse(100Hz) ~1010
Number of photoelectrons detected /excited molecule ~ fewx10-5
Total fluorescence rate ~ 107/secBackground from blackbody radiation comparable to fluorescence