Conceptual Design of BabyIAXO, the intermediate stage towards the International Axion Observatory

Abstract

This article describes BabyIAXO, an intermediate experimental stage of the International Axion Observatory (IAXO), proposed to be sited at DESY. IAXO is a largescale axion helioscope that will look for axions and axion-like particles (ALPs), produced in the Sun, with unprecedented sensitivity. BabyIAXO is conceived to test all IAXO subsystems (magnet, optics and detectors) at a relevant scale for the final system and thus serve as prototype for IAXO, but at the same time as a fully-fledged helioscope with relevant physics reach itself, and with potential for discovery. The BabyIAXO magnet will feature two 10 m long, 70 cm diameter bores, and will host two detection lines (optics and detector) of dimensions similar to the final ones foreseen for IAXO. BabyIAXO will detect or reject solar axions or ALPs with axion-photon couplings down to g aγ ∼ 1.5 × 10 −11 GeV −1 , and masses up to m a ∼ 0.25 eV. BabyIAXO will offer additional opportunities for axion research in view of IAXO, like the development of precision x-ray detectors to identify particular spectral features in the solar axion spectrum, and the implementation of radiofrequency-cavity-based axion dark matter setups. 7 BabyIAXO structure and drive system 58 7.1 Requirements 58 7.2 Foundations 60 7.3 Positioner: tower, head and yokes 61 7.4 Mechanical elements of the drive assemblies 63 7.5 Support frame 64 8 BabyIAXO site and infrastructure 65 8.1 Civil engineering 65 8.2 HERA South Hall 66 8.3 Data acquisition and control 67 9 Conclusions 68 10 Acknowledgements 68 * Notice, however, that the recent analysis in Ref. [48] indicates no exotic energy loss.

Stellar Evolution confronts Axion Models

“…In particular, we consider the proposed International Axion Observatory (IAXO) [111][112][113][114], and its scaled versions BabyIAXO and IAXO+. Of particular interest is BabyIAXO, a scaled down (and significantly less expensive) version of IAXO, which will likely start operations in the mid of the current decade at the Deutsches Elektronen-Synchrotron (DESY) [115,116]. The beginning of operations for IAXO are presently not known.…”

Dark matter from an even lighter QCD axion: trapped misalignment

“…Figure 8: Axion-photon coupling vs. axion mass. Axion limits readapted from [79] include: laboratory axion experiments and helioscopes (dark green) [80][81][82][83], axion DM experiments (blue) [84][85][86][87][88][89][90][91][92][93] and astrophysical bounds (green) [94][95][96][97][98]. Projected sensitivities appear in translucent colors.…”

The Spectrum of Dark Radiation as a Probe of Reheating

“…In Appendix C, we argue that, even if we can just measure the flux in two bins with a relative width of 25% corresponding to a quite moderate energy resolution, the discrimination is possible at the 2σ level with O(1000) events, possibly even significantly less if the data is used more efficiently than in our simplistic estimate. This gives us an optimistic expectation for suitable experiments such as IceCube, IAXO and DARWIN [33,[56][57][58][59][60][61][62]64] (see also [74]).…”

“…In practice, of course, the detection will depend on the type of messenger realized. While the required measurements certainly are quite challenging we can nevertheless conclude (see also Appendix C) that, given the existence of suitable messengers, future measurements at observatories such as IAXO [33,[56][57][58], IceCube [59][60][61][62][63] or DARWIN [64] may shed at least a little light on reheating.…”