The Directional Recoil Identification from Tracks (DRIFT) detector is a low pressure

negative ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

time projection chamber In physics, a time projection chamber (TPC) is a type of particle detector that uses a combination of electric fields and magnetic fields together with a sensitive volume of gas or liquid to perform a three-dimensional reconstruction of a particle ...

(NITPC) designed to detect

weakly interacting massive particles Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter. There exists no formal definition of a WIMP, but broadly, a WIMP is a new elementary particle which interacts via gra ...

(WIMPs) - a prime

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 ...

candidate. There are currently two DRIFT detectors in operation. DRIFT-IId, which is located 1100m underground in the Boulby Underground Laboratory at the Boulby Mine in

North Yorkshire North Yorkshire is the largest ceremonial county (lieutenancy area) in England, covering an area of . Around 40% of the county is covered by national parks, including most of the Yorkshire Dales and the North York Moors. It is one of four cou ...

, England, and DRIFT-IIe, which is located on the surface at

Occidental College Occidental College (informally Oxy) is a private liberal arts college in Los Angeles, California. Founded in 1887 as a coeducational college by clergy and members of the Presbyterian Church, it became non-sectarian in 1910. It is one of the oldes ...

Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the wor ...

. The DRIFT collaboration ultimately aims to develop and operate an underground array of DRIFT detectors for observing and reconstructing WIMP-induced nuclear recoil tracks with enough precision to provide a signature of the

dark matter halo According to modern models of physical cosmology, a dark matter halo is a basic unit of cosmological structure. It is a hypothetical region that has decoupled from cosmic expansion and contains gravitationally bound matter. A single dark matt ...

WIMP detection

There are numerous experiments worldwide attempting to detect the energy deposition that is expected to occur when a WIMP directly collides with an atom of ordinary matter. Ultra sensitive experiments are required to detect the low energy and extremely rare interaction that is predicted to occur between a WIMP and the nucleus of an atom in a target material. The DRIFT detectors vary from the majority of WIMP detectors in their use of a low pressure gas as a target material. The low pressure gas means that an interaction within the detector causes an

ionisation Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...

track of measurable length compared to the point like interactions seen in detectors with solid or liquid target materials. Such ionisation tracks can be reconstructed in three dimensions to determine not only the type of particle that caused it, but from which direction the particle came. This directional sensitivity has the potential to prove the existence of WIMPs by their distinct directional signature.

Detection technology

The DRIFT detector's target material is a 1 m³ cubical

drift chamber A wire chamber or multi-wire proportional chamber is a type of proportional counter that detects charged particles and photons and can give positional information on their trajectory, by tracking the trails of gaseous ionization. was located via ...

filled with a low pressure mixture of

carbon disulfide Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical ...

(CS₂) and

carbon tetrafluoride Tetrafluoromethane, also known as carbon tetrafluoride or R-14, is the simplest perfluorocarbon ( C F4). As its IUPAC name indicates, tetrafluoromethane is the perfluorinated counterpart to the hydrocarbon methane. It can also be classified as a h ...

(CF₄) gases (, respectively). It is predicted that WIMPs will occasionally collide with the nucleus of a sulfur or carbon atom in the carbon disulfide gas causing the nucleus to recoil. An energetic recoiling nucleus will ionise gas particles creating a path of free electrons. These free electrons readily attach to the

electronegative Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...

CS₂ molecules creating a track of ions. The gas volume is divided in half by a

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction i ...

at , which produces a static electric field that causes these negative ions to drift, whilst maintaining the track structure, to the

MWPC A wire chamber or multi-wire proportional chamber is a type of proportional counter that detects charged particles and photons and can give positional information on their trajectory, by tracking the trails of gaseous ionization. was located v ...

planes at two ends of the detector. Addition of of oxygen to the gas mixture has been the key to full fiducialisation of sensitive volume of the DRIFT detector.

Results

DRIFT-IId published Spin-dependent limits in 2012.

References

External links

DRIFT web siteDRIFT-I on display at the Science Museum, London
{{coord, 54.5534, -0.8245, region:GB, display=title Experiments for dark matter search Research institutes in North Yorkshire