The Superconducting Toroid for the New International AXion Observatory (IAXO)

Abstract

Abstract-IAXO, the new International AXion Observatory, will feature the most ambitious detector for solar axions to date. Axions are hypothetical particles which were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. This detector aims at achieving a sensitivity to the coupling between axions and photons of one order of magnitude beyond the limits of the current detector, the CERN Axion Solar Telescope (CAST). IAXO is equivalent to combining roughly 20000 CAST detectors into a single apparatus. The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions to detectable X-ray photons. Inspired by the ATLAS barrel and end-cap toroids, a large superconducting toroid is being designed. The toroid comprises eight, one meter wide and twenty one meters long racetrack coils. The assembled toroid is sized 5.2 m in diameter and 25 m in length and its mass is about 250 tons. The useful field in the bores is 2.5 T while the peak magnetic field in the windings is 5.4 T. At the operational current of 12 kA the stored energy is 500 MJ. The racetrack type of coils are wound with a reinforced Aluminum stabilized NbTi/Cu cable and are conduction cooled. The coils optimization is shortly described as well as new concepts for cryostat, cold mass, supporting structure and the sun tracking system. Materials selection and sizing, conductor, thermal loads, the cryogenics system and the electrical system are described. Lastly, quench simulations are reported to demonstrate the system's safe quench protection scheme.

Axion Searches at the LHC: FASER as a Light Shining through Walls Experiment

“…2 alongside existing constraints. In the left panel, we show the broad picture including all existing constraints on axions arising from helioscopes [70][71][72][73], haloscopes and LSW experiments [99][100][101][102][103][104] (red); astrophysics 2 [36, 107-141] (green); cosmology [37,142] (blue); and accelerator experiments [31,[143][144][145][146][147][148][149][150][151][152][153][154][155][156][157] (gray). The projected sensitivity for searches at FASER and future experiments at the FPF is indicated by the blue solid lines.…”

New cosmological bounds on hot relics: Axions $\&$ Neutrinos

“…We quote our most restrictive bounds (Planck + BAO), together with the constraint obtained with Planck data only (both at 95% CL). We also show current and future limits expected from different experiments: CAST [26], IAXO [27,28], ORGAN [29], MADMAX [30], Plasma Haloscope [31], ADMX [32,33] and BRASS [89].…”

“…The most elegant solution at present to the strong CP problem in Quantum Chromodynamics (QCD) would require the Lagrangian of the Standard Model of elementary particles to be invariant under an additional global U (1) PQ (Peccei-Quinn) symmetry, spontaneously broken at some energy scale f a [1][2][3][4][5][6][7][8][9][10][11][12][13][14], with an associated Pseudo Nambu Goldestone Boson (PNGB), the so-called axion [7][8][9][10][11][15][16][17][18][19][20]. A strong experimental effort has been devoted in different fields to search for axions [21][22][23][24][25][26][27][28][29][30][31][32][33]. If these elusive particles exist, they can be copiously produced via both thermal and non-thermal processes in the early universe.…”

Solar Production of Ultralight Bosons

“…The key piece of IAXO is a 25 m long magnet with a 2.5 T (5.1 T) average (peak) field. For the first time, a helioscope will use a toroidal multibore configuration [60] with 8 coils of 70 cm diameter each and a total diameter of 5.1 m resulting in an intense [39] field over a large conversion volume. The magnet figure of merit f M alone provides a 300× improvement over CAST.…”