The International Axion Observatory (IAXO) is a next-generation

axion An axion () is a hypothetical elementary particle postulated by the Peccei–Quinn theory in 1977 to resolve the strong CP problem in quantum chromodynamics (QCD). If axions exist and have low mass within a specific range, they are of interes ...

helioscope A helioscope is an instrument used in observing the sun and sunspots. The helioscope was first used by Benedetto Castelli (1578-1643) and refined by Galileo (1564–1642). The method involves projecting an image of the sun onto a white sheet of pa ...

for the search of solar axions and axion-like particles. It is the follow-up of the CERN Axion Solar Telescope (CAST), which has been operating since 2003. The IAXO will be set up by implementing the helioscope concept used in the CAST experiment to its largest possible size. The Letter of Intent for International Axion Observatory was submitted to the

CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...

SPS committee in August 2013. IAXO formally founded in July 2017 and received an advanced grant from the

European Research Council The European Research Council (ERC) is a public body for funding of scientific and technological research conducted within the European Union (EU). Established by the European Commission in 2007, the ERC is composed of an independent Scientific ...

in October 2018. The near-term goal of the collaboration is to build a scaled-down prototype version of the experiment, called Baby-IAXO, which is under discussion for a possible location at DESY, Germany.

Baby IAXO

Baby IAXO is a prototype, scaled-down version of all the subsystems of the IAXO. The prototype is a testing version and will serve as an intermediate step to explore further possible improvements to the real IAXO. Baby IAXO would be set up in

Hamburg (male), (female) en, Hamburger(s), Hamburgian(s) , timezone1 = Central (CET) , utc_offset1 = +1 , timezone1_DST = Central (CEST) , utc_offset1_DST = +2 , postal ...

Germany Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...

by the CERN and DESY collaboration. CERN would be responsible for giving in the design reports of prototype

magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...

s and

cryostat A cryostat (from ''cryo'' meaning cold and ''stat'' meaning stable) is a device used to maintain low cryogenic temperatures of samples or devices mounted within the cryostat. Low temperatures may be maintained within a cryostat by using various ...

, and DESY would design and construct the movable platform along with the other infrastructure. The data taking by Baby IAXO is scheduled to start in 2025, and consecutively IAXO will be operational from 2028.

Physics potential

IAXO will primarily be hunting the solar axions, along with the potential to observe the

Quantum chromodynamics In theoretical physics, quantum chromodynamics (QCD) is the theory of the strong interaction between quarks mediated by gluons. Quarks are fundamental particles that make up composite hadrons such as the proton, neutron and pion. QCD is a type ...

(QCD) axion in the mass range of 1meV to 1eV. It is also expected to be capable of discovering axion-like particles (known as the ALPs) coupled either with

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they always ...

s or electrons. The QCD-axions and the ALPs are predicted to have quite similar properties, and hence the IAXO whose primary goal is to observe the solar axions and photon-coupled ALPs will also be able to detect the QCD axions and ALPs from different unexplored astrophysical axion sources. It, therefore, has the potential to solve both the strong CP problem and the dark matter problem, which depends on the discovery of the axion particles. The IAXO is believed to be the most ambitious experiment among the current-day experiment set-ups to observe the hypothetical axions. It could also be later implemented to test models of hypothesized hidden photons or

chameleons Chameleons or chamaeleons (family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 202 species described as of June 2015. The members of this family are best known for their distinct range of colors, bein ...

Experimental setup

The IAXO will be primarily based on an improved helioscope, with a

signal to noise ratio In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

of five orders of magnitude higher compared to current-day detectors. The crossectional area of the magnet equipped with an X-ray focus optics is meant to increase this signal to background ratio. When the solar axions come in contact with the magnetic crosssection, they are converted into

s through the

Primakoff effect In particle physics, the Primakoff effect, named after Henry Primakoff, is the resonant production of neutral pseudoscalar mesons by high-energy photons interacting with an atomic nucleus. It can be viewed as the reverse process of the Particle d ...

. These photons would then be detected by X-ray detectors placed on the telescope. This implies that a larger magnetic cross-section will lead to a more intense signal. The magnetic subsystem will also be equipped with a mechanical system allowing it to follow the sun consistently throughout the day, leading to enhanced exposure. The IAXO subsystems comprising magnets, optics, and detectors are planned to be fully optimized for solar axion detectors. The sensitivity of the axion-photon coupling measurement in IAXO would be 1-1.5 order of magnitude higher than that achieved by previous detectors such as CAST. The central magnetic systems will have a large

superconducting magnet A superconducting magnet is an electromagnet made from coils of superconducting wire. They must be cooled to cryogenic temperatures during operation. In its superconducting state the wire has no electrical resistance and therefore can conduct mu ...

, configured in a toroidal multibore manner, in order to generate a strong magnetic field over a larger volume. It will be a 25 long magnet, 5.3 m diameter toroid composed of 8 different coils. This configuration is calculated to generate a 2.5 Tesla magnetic field within a 600 mm diameter. The said magnetic subsystem is inspired by the

ATLAS experiment ATLAS is the largest general-purpose particle detector experiment at the Large Hadron Collider (LHC), a particle accelerator at CERN (the European Organization for Nuclear Research) in Switzerland. The experiment is designed to take advantage ...

. IAXO optics will be inspired by NASA's NuStar X-ray satellite.

Sources accessible to IAXO

Any particle found by IAXO will be at the least a sub-dominant component of the

Dark Matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not ab ...

. The observatory would be capable of observing from a wide range of sources given below. #

Axions # Dark matter Axions # Solar axions # Axions from astrophysical cooling anomalies such as

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

cooling,

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...

cooling,

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

s, supergiant stars powered by

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

External links

International Axion Observatory Website

References