I. Giomataris

An improved limit on the axion–photon coupling from the CAST experiment

We have searched for solar axions or similar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup with improved conditions in all detectors. From the absence of excess X-rays when the magnet was pointing to the Sun, we set an upper limit on the axion-photon coupling of 8.8 x 10^{-11} GeV^{-1} at 95% CL for m_a<~ 0.02 eV. This result is the best experimental limit over a broad range of axion masses and for m_a<~ 0.02 eV also supersedes the previous limit derived from energy-loss arguments on globular-cluster stars.

Towards a new generation axion helioscope

We study the feasibility of a new generation axion helioscope, the most ambitious and promising detector of solar axions to date. We show that large improvements in magnetic field volume, x-ray focusing optics and detector backgrounds are possible beyond those achieved in the CERN Axion Solar Telescope (CAST). For hadronic models, a sensitivity to the axion-photon coupling of gaγ few × 10−12 GeV−1 is conceivable, 1–1.5 orders of magnitude beyond the CAST sensitivity. If axions also couple to electrons, the Sun produces a larger flux for the same value of the Peccei-Quinn scale, allowing one to probe a broader class of models. Except for the axion dark matter searches, this experiment will be the most sensitive axion search ever, reaching or surpassing the stringent bounds from SN1987A and possibly testing the axion interpretation of anomalous white-dwarf cooling that predicts ma of a few meV. Beyond axions, this new instrument will probe entirely unexplored ranges of parameters for a large variety of axion-like particles (ALPs) and other novel excitations at the low-energy frontier of elementary particle physics.

New CAST limit on the axion–photon interaction

During 2003--2015, the CERN Axion Solar Telescope (CAST) has searched for

Experimental studies of a micromegas neutron detector

a\to\gamma

A novel large-volume spherical detector with proportional amplification read-out

conversion in the 9 T magnetic field of a refurbished LHC test magnet that can be directed toward the Sun. In its final phase of solar axion searches (2013--2015), CAST has returned to evacuated magnet pipes, which is optimal for small axion masses. The absence of a significant signal above background provides a world leading limit of

Micromegas detector developments for Dark Matter directional detection with MIMAC

g_{a\gamma} < 0.66 \times 10^{-10} {\rm GeV}^{-1}

Characterization of microbulk detectors in argon- and neon-based mixtures

(95% C.L.) on the axion-photon coupling strength for

The NEXT experiment

m_a \lesssim 0.02

Electron drift velocity measurements at high electric fields

eV. Compared with the first vacuum phase (2003--2004), the sensitivity was vastly increased with low-background x-ray detectors and a new x-ray telescope. These innovations also serve as pathfinders for a possible next-generation axion helioscope.

Micromegas operation in high pressure xenon: charge and scintillation readout

Abstract A Micromegas detector to be used as a neutron beam profiler has been tested in the CENBG neutron beam. Two thin solid targets ( 6 Li and 10 B) have been used as neutron converters. We report results on the detection efficiency and spatial resolution of the detector.