Conceptual design of the International Axion Observatory (IAXO)

Abstract

The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO will look for axions or axion-like particles (ALPs) originating in the Sun via the Primakoff conversion of the solar plasma photons. In terms of signalto-noise ratio, IAXO will be about 4-5 orders of magnitude more sensitive than CAST, currently the most powerful axion helioscope, reaching sensitivity to axion-photon couplings down to a few ×10 −12 GeV −1 and thus probing a large fraction of the currently unexplored axion and ALP parameter space. IAXO will also be sensitive to solar axions produced by mechanisms mediated by the axion-electron coupling g ae with sensitivity −for the first time− to values of g ae not previously excluded by astrophysics. With several other possible physics cases, IAXO has the potential to serve as a multi-purpose facility for generic axion and ALP research in the next decade. In this paper we present the conceptual design of IAXO, which follows the layout of an enhanced axion helioscope, based on a purpose-built 20m-long 8-coils toroidal superconducting magnet. All the eight 60cm-diameter magnet bores are equipped with focusing x-ray optics, able to focus the signal photons into ∼ 0.2 cm 2 spots that are imaged by ultra-low-background Micromegas x-ray detectors. The magnet is built into a structure with elevation and azimuth drives that will allow for solar tracking for ∼12 h each day.

Gaseous time projection chambers for rare event detection: results from the T-REX project. II. Dark matter

“…Since then, CAST has been a test bench for these developments. Currently, CAST Micromegas detectors have demonstrated the best signal-to-noise figures in the history of CAST, and are the baseline detection technology for the future International Axion Observatory (IAXO) [22,24], the next generation axion helioscope under proposal.…”

New CAST limit on the axion–photon interaction

“…Solar axion searches beyond CAST, and at the same time beyond the HB star limit as a benchmark, require a new effort on a much larger scale, for example the proposed helioscope IAXO 28 . For small masses, new regions in the g aγ -m a will be explored with the upcoming ALPS-II laser propagation experiment at DESY 47 , by higher-statistics TeV γ -ray observations, or the γ -ray signal from a future galactic supernova 40 .…”

“…These developments are also part of the activities to define the detection technologies suitable for the proposed much larger next-generation axion helioscope IAXO 28 . We here report the results of this effort in CAST.…”

Axion predictions in SO(10) × U(1)PQ models

“…Note that the region in the N DW = 3 case has been derived under the assumption that the PQ symmetry is protected by a discrete symmetry, so that Planck scale suppressed PQ violating operators are allowed at dimension 10 or higher [69]. In the last two lines the projected sensitivities of various experiments are indicated [70][71][72][73][74][75][76][77].…”

“…Furthermore, in the meV mass range of interest for the post-inflationary PQ symmetry breaking scenario, the model can be probed by the presently being build fifth force experiment ARIADNE [75] and the proposed helioscope IAXO [76], cf. figure 12.…”