The QUAX proposal: a search of galactic axion with magnetic materials

Aim of the QUAX (QUaerere AXion) proposal is to exploit the interaction of cosmological axions with the spin of electrons in a magnetized sample. Their effect is equivalent to the application of an oscillating rf field with frequency and amplitude which are fixed by axion mass and coupling constant, respectively. The rf receiver module of the QUAX detector consists of magnetized samples with the Larmor resonance frequency tuned to the axion mass by a polarizing static magnetic field. The interaction of electrons with the axion-equivalent rf field produces oscillations in the total magnetization of the samples. To amplify such a tiny field, a pump field at the same frequency is applied in a direction orthogonal to the polarizing field. The induced oscillatory magnetization along the polarizing field is measured by a SQUID amplifier operated at its quantum noise level.Comment: 5 pages, Contribution for the proceedings of the TAUP2015, International Conference on Topics in Astroparticle and Underground Physics, 7-11 September 2015, Torino, Ital

Experimental perspectives in (low-energy) photon-photon scattering

The possibility of photon-photon scattering is a striking difference between classical and quantum electrodynamics. This genuinely quantum feature is made possible by the fluctuations of charged fields, and it makes quantum vacuum a nonlinear optical medium. Photon-photon scattering is thus a delicate probe into the structure of quantum electrodynamics and any departure from the expected behavior would be a powerful signal of "new physics". To date this process has never been observed – except as a radiative correction to other processes – and several experiments are trying to detect it at very low energy, in the scattering of real photons in powerful light beams off the virtual photons of intense magnetic fields. Here we briefly review the experimental state-of-the-art, with special emphasis on the PVLAS experiment, and we describe a new proposal to observe photon-photon scattering in the range 1 – 2 MeV

Cryogenic Safety - HSE seminar

The superconducting linac ALPI at INFN-LNL is composed of 20 identical cryostats housing, at a group of four (or two), 74 superconducting QWR type cavities: 58 resonators are made of copper with Nb sputtered on the internal surface and 16 are made of Nb bulk. In each cryostat is installed a 100 liter volume LHe reservoir feeding by gravity the QWR’s. The thermal shield around is cooled by GHe at 6 bar abs at 60-80 K. The linac ALPI is a post-accelerator which can receive heavy ions from either the 16 MV Tandem Van de Graaf or from the superconducting injector PIAVE. The latter is composed by an ECR source, two superconducting RFQ, and two cryostats each containg four superconducting bulk Nb QWR. The ALPI cryostats are cooled by a Helium refrigerator whose refrigerator capacity is 1200 W at 4.5 K and 3900 W additional at 60-80 K. PIAVE cryostats are cooled by a separate TCF50 helium refrigerator. The complex ALPI-PIAVE is installed in a semi-open removable concrete tunnel in the same building where the two helium refrigerators are also present. The cryogenic safety issues of the linac plus the injector will be outlined, both for the equipment and the personnel

Measuring the magnetic birefringence of vacuum: the PVLAS experiment

We describe the principle and the status of the PVLAS experiment which is presently running at the INFN section of Ferrara, Italy, to detect the magnetic birefringence of vacuum. This is related to the QED vacuum structure and can be detected by measuring the ellipticity acquired by a linearly polarized light beam propagating through a strong magnetic field. Such an effect is predicted by the Euler–Heisenberg Lagrangian. The method is also sensitive to other hypothetical physical effects such as axion-like particles and in general to any fermion/boson millicharged particle. Here we report on the construction of our apparatus based on a high finesse (> 2 · 10^5) Fabry–Perot cavity and two 0.9 m long 2.5 T permanent dipole rotating magnets, and on the measurements performed on a scaled down test setup. With the test setup we have improved by about a factor 2 the limit on the parameter A_e describing nonlinear electrodynamic effects in vacuum: A_e < 2.9 · 10^−21 T^−2 @ 95% C.L

Cryogenic Control System Migration and Developments towards the UNICOS CERN Standard at INFN

The cryogenic control systems at Laboratori Nazionali di Legnaro (LNL) are undergoing an important and radical modernization, allowing all the plants controls and supervision systems to be renewed in a homogeneous way towards the CERN-UNICOS standard. Before the UNICOS migration project started there were as many as 7 different types of PLC and 7 different types of SCADA, each one requiring its own particular programming language. In these conditions, even a simple modification and/or integration on the program or on the supervision, required the intervention of a system integrator company, specialized in its specific control system. Furthermore it implied that the operators have to be trained to learn the different types of control systems. The CERN-UNICOS invented for LHC [1] has been chosen due to its reliability and planned to run and be maintained for decades on. The complete migration is part of an agreement between CERN and INFN

Progress toward a direct experimental detection of γγ interactions

A fundamental quantum electrodynamics prediction which has so far not yet been confirmed experimentally by a direct observation in a laboratory experiment is γγ interactions. Such a direct observation requires a scenario where both the beam and the target are made of bosons, while so far experiments have exploited matter particles as beam and/or target. A consequence of the existence of γγ interactions is that vacuum features magnetic birefringence as a macroscopic property. Magnetic Birefringence of Vacuum (MBV) is due to interactions of beam photons with virtual photons of a magnetic field. These interactions are mediated by loops of electron-positron and (with extremely weaker effects) by loops of muons and loops of hadrons, and could possibly be mediated by hypothetical very light particles with a coupling to two photons. Experimentation to detect MBV not only has started much later than experiments that have provided magnificent validations of QED, like g-2 and Lamb shift, but has not yet matched the performances necessary to observe MBV. A summary of the main properties and performances of experiments aiming at MBV detection is given with focus on recent results of the PVLAS experiment. The time evolution of the missing factor which monitors the capability of an experiment to observe MBV is reported. This evolution points to MBV detection in a near future. MBV experimentation could evolve from detection to precision measurements modulo a change in scale of the experiments, if it will be possible to exploit together the peak performances achieved separately in components of different MBV experiments. Data collected with the aim of detecting MBV provide at present the best model independent limits on the coupling to two photons of (so far hypothetical) very light scalar and pseudoscalar particles

The new PVLAS apparatus for detection of magnetic birefringence of vacuum

The PVLAS experiment aims at the observation and measurement of the effect of magnetic birefringence of vacuum (MBV) predicted by Quantum Electrodynamics. We describe here the new PVLAS apparatus which is currently being setup in INFN Ferrara. The apparatus features two rotating permanent dipole magnets and an ellipsometer operating under UHV with a high finesse Fabry–Perot cavity

First run of the PVLAS experiment: Dark matter candidates production and detection

The PVLAS experiment is designed to study photon-photon interactions in the low energy region using optical techniques. In the PVLAS apparatus photons from a laser beam interact in vacuum with an external magnetic field, and the two-photon interaction results in the possible production of neutral, nearly massless, scalar/pseudoscalar particles. Evidence of particle production is extracted from the study of the light polarisation state after traversing a region where a the magnetic field is provided by a superconducting dipole magnet. Polarisation measurements are conducted using a very sensitive ellipsometer based on a high finesse (~100000), 6.4 m long, Fabry-Perot optical resonator. The PVLAS apparatus is now fully integrated and operational: the first commissioning run with a 4.0 T field has been successfully completed, the first data taking runs have been conducted, yielding a total integration time of about 20 hours, and data analysis is now in progress. We will present details from the commissioning run and preliminary results from the data runs