Investigation of the Periodic Magnetic Field Modulation Inside Apertures of LHC Superconducting Dipole Models

The windings of high-field accelerator magnets are usually made of Rutherford-type superconducting cables. The magnetic field distribution along the axis of such magnets exhibits a pronounced periodic modulation with a wavelength equal to the twist pitch length of the cable used in the winding. Such an effect, resulting from quasi-persistent currents, was investigated with a Hall probe array inserted inside the aperture of 1-metre long LHC superconducting dipole models. The amplitude and the time dependence of this periodic field oscillation have been studied as a function of the transport current history. The impact on the magnet stability of the non-uniform current redistribution producing such a field modulation is discussed

Investigation of the Periodic Magnetic Field Modulation in LHC Superconducting Dipoles

The windings of high-field accelerator magnets are usually made of Rutherford-type superconducting cables. The magnetic field distribution along the axis of such magnets exhibits a periodic modulation with a wavelength equal to the twist pitch length of the cable used in the winding. This effect, resulting from quasi-persistent currents, was investigated with a Hall probes array inserted inside the aperture of the LHC superconducting dipoles, both in short models and full-scale prototypes. The amplitude and the time dependence of this periodic field oscillation have been studied as a function of the magnet current history. The origin and the impact on the LHC dipoles stability of the non-uniform current redistribution producing such a field modulation are discussed

Minicharges and Magnetic Monopoles

Minicharged particles arise naturally in extensions of the Standard Model with a kinetic mixing term between the ordinary electromagnetic U(1) and an extra "hidden sector" U(1). In this note we study the compatibility of these particles with the existence of magnetic monopoles. We find that angular momentum quantization allows only certain combinations of ordinary and hidden monopole charge. Using the example where one of the U(1)s originates from a spontaneously broken SU(2), we demonstrate that exactly the allowed types of monopoles arise as 't Hooft-Polyakov monopoles.Comment: 9 pages, 1 figur

Limits on Low Energy Photon-Photon Scattering from an Experiment on Magnetic Vacuum Birefringence

Experimental bounds on induced vacuum magnetic birefringence can be used to improve present photon-photon scattering limits in the electronvolt energy range. Measurements with the PVLAS apparatus (E. Zavattini {\it et al.}, Phys. Rev. D {\bf77} (2008) 032006) at both $\lambda = 1064$ nm and 532 nm lead to bounds on the parameter {\it A$_{e}$}, describing non linear effects in QED, of $A_{e}^{(1064)} < 6.6\cdot10^{-21}$ T$^{-2}$ @ 1064 nm and $A_{e}^{(532)} < 6.3\cdot10^{-21}$ T$^{-2}$ @ 532 nm, respectively, at 95% confidence level, compared to the predicted value of $A_{e}=1.32\cdot10^{-24}$ T$^{-2}$. The total photon-photon scattering cross section may also be expressed in terms of $A_e$, setting bounds for unpolarized light of $\sigma_{\gamma\gamma}^{(1064)} < 4.6\cdot10^{-62}$ m$^{2}$ and $\sigma_{\gamma\gamma}^{(532)} < 2.7\cdot10^{-60}$ m$^{2}$. Compared to the expected QED scattering cross section these results are a factor of $\simeq2\cdot10^{7}$ higher and represent an improvement of a factor about 500 on previous bounds based on ellipticity measurements and of a factor of about $10^{10}$ on bounds based on direct stimulated scattering measurements

Search for weakly interacting sub-eV particles with the OSQAR laser-based experiment: results and perspectives

Recent theoretical and experimental studies highlight the possibility of new fundamental particle physics beyond the Standard Model that can be probed by sub-eV energy experiments. The OSQAR photon regeneration experiment looks for "Light Shining through a Wall" (LSW) from the quantum oscillation of optical photons into "Weakly Interacting Sub-eV Particles" (WISPs), like axion or axion-like particles (ALPs), in a 9 T transverse magnetic field over the unprecedented length of $2 \times 14.3$ m. No excess of events has been detected over the background. The di-photon couplings of possible new light scalar and pseudo-scalar particles can be constrained in the massless limit to be less than $8.0\times10^{-8}$ GeV$^{-1}$. These results are very close to the most stringent laboratory constraints obtained for the coupling of ALPs to two photons. Plans for further improving the sensitivity of the OSQAR experiment are presented.Comment: 7 pages, 7 figure

STUDY OF FRINGE FIELDS EFFECTS FROM FINAL FOCUS QUADRUPOLES ON BEAM BASED MEASURED QUANTITIES

Accelerator physics needs advanced modeling and simulation techniques, in particular for beam stability studies. A deeper understanding of the effects of magnetic fields non-linearities will greatly help in the improvement of future colliders design and performance. In previous papers, a new tracking method was proposed to study the effect of the longitudinal dependency of the harmonics on the beam dynamics. In this paper, the study will focus on the effects on observable quantities in beam based measurements, for the case of HL-LHC Inner Triplet and with possible tests in LHC

Axion-like-particle search with high-intensity lasers

We study ALP-photon-conversion within strong inhomogeneous electromagnetic fields as provided by contemporary high-intensity laser systems. We observe that probe photons traversing the focal spot of a superposition of Gaussian beams of a single high-intensity laser at fundamental and frequency-doubled mode can experience a frequency shift due to their intermittent propagation as axion-like-particles. This process is strongly peaked for resonant masses on the order of the involved laser frequencies. Purely laser-based experiments in optical setups are sensitive to ALPs in the $\mathrm{eV}$ mass range and can thus complement ALP searches at dipole magnets.Comment: 25 pages, 2 figure

Axions, their Relatives and Prospects for the Future

The observation of a non-vanishing rotation of linear polarized laser light after passage through a strong magnetic field by the PVLAS collaboration has renewed the interest in light particles coupled to photons. Axions are a species of such particles that is theoretically well motivated. However, the relation between coupling and mass predicted by standard axion models conflicts with the PVLAS observation. Moreover, light particles with a coupling to photons of the strength required to explain PVLAS face trouble from astrophysical bounds. We discuss models that can avoid these bounds. Finally, we present some ideas to test these possible explanations of PVLAS experimentally.Comment: 11 pages, 4 figures. Contributed to the ``Third Symposium on Large TPCs for Low Energy Rare Event Detection'' in Paris, December 200

High magnetic fields for fundamental physics

Various fundamental-physics experiments such as measurement of the magnetic birefringence of the vacuum, searches for ultralight dark-matter particles (e.g., axions), and precision spectroscopy of complex systems (including exotic atoms containing antimatter constituents) are enabled by high-field magnets. We give an overview of current and future experiments and discuss the state-of-the-art DC- and pulsed-magnet technologies and prospects for future developments

Latest Results of the OSQAR Photon Regeneration Experiment for Axion-Like Particle Search

The OSQAR photon regeneration experiment searches for pseudoscalar and scalar axion-like particles by the method of "Light Shining Through a Wall", based on the assumption that these weakly interacting sub-eV particles couple to two photons to give rise to quantum oscillations with optical photons in strong magnetic field. No excess of events has been observed, which constrains the di-photon coupling strength of both pseudoscalar and scalar particles down to $5.7 \cdot 10^{-8}$ GeV$^{-1}$ in the massless limit. This result is the most stringent constraint on the di-photon coupling strength ever achieved in laboratory experiments.Comment: 6 pages, 5 figures. appears in Proceedings of the 10th PATRAS Workshop on Axions, WIMPs and WISPs (2014