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Thursday, November 15, 2012

Paul Berceau

High Magnetic Fields National Laboratory
Toulouse, France

Quantum Vacuum Magnetic Birefringence

Abstract: In this talk I will present a magneto-optics experiment dealing with the behavior of polarized light propagating in transverse magnetic fields. The BMV (Biréfringence Magnétique du Vide) experiment is an ambitious project whose goal is to check in the laboratory the predictions for vacuum energy in quantum electrodynamics. This theory predicts that vacuum, in the presence of a transverse magnetic field, behaves as a birefringent medium. And the measurement of the value of this birefringence is a real challenge: Δn_b = 4 x 10^-24 for an applied magnetic field of 1T.

The experiment consists in measuring the ellipticity ψ acquired by an incident linearly polarized laser beam, after propagation inside an optical cavity of finesse F and in the presence of a strong magnetic field B. One can show that this ellipticity is given by:

where λ is the light wavelength, L_B is the length of the magnetic region and θ is the angle between the incident light polarization and the magnetic field.

I will first describe our experimental setup based on intense pulsed magnetic fields and a sensitive optical apparatus, mainly consisting of a very high finesse cavity, for the detection of effects induced by this field on the laser polarization.

I will then present the calibration of this setup by the measurement of gases magnetic birefringence's, before giving our first limits on vacuum magnetic birefringence. I will finally discuss the necessary improvements to reach our final goal.

Bio: Not Available

Time: 2:00pm – 3:30pm

Location: Physics and Astrophysics Conference Room 102/103

Light refreshments available 4:00pm; Presentation begiins 4:15pm

Open to All