QUBIC is a cosmology project to study

cosmic inflation In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from seconds after the conjectured Big Bang singularity ...

by measuring the B-modes of the polarization of the

Cosmic Microwave Background In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all spac ...

(CMB), by observing the sky with a millimeter wave

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

interferometer Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...

. It uses bolometric

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

, which combines the advantages of interferometry (reduction of systematic errors) and those of the bolometer detectors (high signal sensitivity). QUBIC observes the sky at two frequencies, 150 and 220 GHz, so that it can separate the cosmological signal from foreground emission, in particular thermal

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...

emission. The QUBIC project began in 2008 with the merger of BRAIN and MBI projects. A technical demonstrator of the instrument is being manufactured and should be tested in France in 2017. On 26 October 2022 the first module should was installed and began operating in Argentina in the region of Alto Chorrillos,

Salta Salta () is the capital and largest city in the Argentine province of the same name. With a population of 618,375 according to the 2010 census, it is also the 7th most-populous city in Argentina. The city serves as the cultural and economic ce ...

province next to the Large Latin American Millimeter Array. QUBIC is an international collaboration involving universities and laboratories in Ireland, France, Italy, Argentina, the U.K. and the U.S.A.

Observing instrument

The observing instrument is a millimeter wave

contained in a

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 ...

which is cooled to 4K with pulse tube coolers, to avoid contaminating the received signal with thermal radiation. Since millimeter waves are absorbed by water vapor in the atmosphere the device must be located at high altitudes above most of the atmosphere. The first module will be installed at the Large Latin American Millimeter Array (LLAMA) site at Alto de Chorillo near

Salta, Argentina Salta () is the capital and largest city in the Argentine province of the same name. With a population of 618,375 according to the 2010 census, it is also the 7th most-populous city in Argentina. The city serves as the cultural and economic ce ...

, at an altitude of . The millimeter waves pass through a 45 cm polyethylene window in the cryostat and then through a rotating

half-wave plate A waveplate or retarder is an optical device that alters the polarization state of a light wave travelling through it. Two common types of waveplates are the ''half-wave plate'', which shifts the polarization direction of linearly polarized ligh ...

which modulates the polarization, followed by a polarizing grid which selects one of the two polarizing angles. The radiation then passes through an array of 400 microwave horns which

References

{{CMB experiments Astronomical instruments Cosmic microwave background experiments