View of the apparatus at the LNL INFN lab in Legnaro
View of the prototype apparatus in the Physics Dept. of
University of Ferrara
effects in electromagnetic processes in vacuum have been sought
for many years after having been predicted by Euler and Heisenberg
their effective Lagrangian published in 1936. The only input to
calculation was the Heisenberg uncertainty principle leading to
pair creation, which allowed photons to interact with each other.
The direct measurement of this effect is yet to be seen and has
the aim of the PVLAS experiment since its beginnings. The PVLAS
experiment, financed by the Italian Istituto Nazionale di Fisica
Nucleare (INFN), is located at
Laboratori Nazionali di Legnaro of INFN (LNL), Padova, Italy (old site)
in the Physics Dept. of the Ferrara University (new site).
The LNL setup consists of a sensitive ellipsometer attempting to
small changes in the polarization state of light propagating
1 m long magnetic field region in vacuum. It is based on a high
Fabry-Perot cavity and a superconducting 5 T rotating dipole
Indeed, vacuum will become birefringent in the presence of a
magnetic field. A possible secondary effect, which could mask the
vacuum magnetic birefringence, could be due to the existence of a
light, neutral pseudoscalar/scalar particle coupling to two
the Primakoff effect.
The Ferrara prototype setup is similar, but the ellipsometer has a
horizontal axis (instead of vertical as in LNL), and the
utilizes permanent magnets.