Dark Matter Time Projection Chamber
Encyclopedia
The Dark Matter Time Projection Chamber (DMTPC) is an experiment for direct detection of weakly interacting massive particles (WIMPs), one of the most favored candidates for dark matter
. The experiment uses a low-pressure time projection chamber
in order to extract the original direction of potential dark matter events. The collaboration includes physicists from the Massachusetts Institute of Technology
(MIT), Boston University
(BU), and Brandeis University
. Several prototype detectors have been built and tested in laboratories at MIT and BU. The group took its first data in an underground laboratory at the Waste Isolation Pilot Plant
(WIPP) site near Carlsbad, New Mexico
in Fall, 2010.
gas. Charged particles incident on the gas are slowed and eventually stopped, leaving a trail of free electrons and ionized
molecules. The electrons are drifted by an electric field toward an amplification region. Instead of using MWPC endplates for amplification and event readout, as in the traditional TPC design, the DMTPC amplification region consists of a metal wire mesh separated from a copper anode with a high electric field between them. This creates a more uniform electric field in order to preserve the shape of the original track during amplification. The avalanche of electrons also creates a great deal of scintillation
light, which passes through the wire mesh. Some of this light is collected by a CCD camera located outside the main detector volume. This results in a a two dimensional image of the ionization signal of the track as it appeared on the amplification plane. Information about the charged particle, including its direction of motion within the detector, can be reconstructed from the CCD readout. Additional track information is obtained from readout of the charge signal on the anode plane.
The largest existing prototype detectors each have a total of 20 L of CF4 gas within the drift region, where measurable events will occur. The group also plans to eventually construct a detector with a volume of 1 m3.
. While the WIMP does not directly leave a track, the momentum transfer of the interaction causes the atom to recoil, and its ionization track, with a typical range of a few millimeters, may be detected. CF4 gas is used because the most common fluorine isotope, 19F, is believed to be an excellent target nucleus for setting spin
-dependent WIMP-nucleon
scattering. If the recoiling ion is energetic enough, the direction of the incoming WIMP may be extrapolated from the direction of the recoil.
Because of the motion of the solar system around the center of the galaxy, many physicists believe that the particles comprising the dark matter halo
will appear to originate from a particular direction in the sky roughly corresponding to the position of the constellation Cygnus
. If this is true, the DMTPC group hope to be able to use the directional track information to statistically confirm the existence of dark matter, even in the presence of non-dark matter backgrounds which are believed to have a different directional signal. Several other groups developing low pressure TPC dark matter detectors with directional sensitivity exist, including DRIFT
, NEWAGE, and MIMAC. Additionally, dark matter searches such as COUPP and NEWAGE also use fluorine as the principal target nucleus for spin-dependent interactions.
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
. The experiment uses a low-pressure time projection chamber
Time projection chamber
In physics, a time projection chamber is a particle detector invented by David R. Nygren, an American physicist, at Lawrence Berkeley Laboratory in the late 1970s...
in order to extract the original direction of potential dark matter events. The collaboration includes physicists from the Massachusetts Institute of Technology
Massachusetts Institute of Technology
The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...
(MIT), Boston University
Boston University
Boston University is a private research university located in Boston, Massachusetts. With more than 4,000 faculty members and more than 31,000 students, Boston University is one of the largest private universities in the United States and one of Boston's largest employers...
(BU), and Brandeis University
Brandeis University
Brandeis University is an American private research university with a liberal arts focus. It is located in the southwestern corner of Waltham, Massachusetts, nine miles west of Boston. The University has an enrollment of approximately 3,200 undergraduate and 2,100 graduate students. In 2011, it...
. Several prototype detectors have been built and tested in laboratories at MIT and BU. The group took its first data in an underground laboratory at the Waste Isolation Pilot Plant
Waste Isolation Pilot Plant
The Waste Isolation Pilot Plant, or WIPP, is the world's third deep geological repository licensed to permanently dispose of transuranic radioactive waste for 10,000 years that is left from the research and production of nuclear weapons...
(WIPP) site near Carlsbad, New Mexico
Carlsbad, New Mexico
Carlsbad is a city in and the county seat of Eddy County, New Mexico, in the United States. As of the 2010 census, the city population was 26,138. Carlsbad is the center of the designated micropolitan area of Carlsbad-Artesia, which has a total population of 55,435...
in Fall, 2010.
Detector Concept
The DMTPC detector consists of a TPC filled with low pressure CF4Tetrafluoromethane
Tetrafluoromethane, also known as carbon tetrafluoride, is the simplest fluorocarbon . It has a very high bond strength due to the nature of the carbon–fluorine bond. It can also be classified as a haloalkane or halomethane...
gas. Charged particles incident on the gas are slowed and eventually stopped, leaving a trail of free electrons and ionized
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...
molecules. The electrons are drifted by an electric field toward an amplification region. Instead of using MWPC endplates for amplification and event readout, as in the traditional TPC design, the DMTPC amplification region consists of a metal wire mesh separated from a copper anode with a high electric field between them. This creates a more uniform electric field in order to preserve the shape of the original track during amplification. The avalanche of electrons also creates a great deal of scintillation
Scintillation (physics)
Scintillation is a flash of light produced in a transparent material by an ionization event. See scintillator and scintillation counter for practical applications.-Overview:...
light, which passes through the wire mesh. Some of this light is collected by a CCD camera located outside the main detector volume. This results in a a two dimensional image of the ionization signal of the track as it appeared on the amplification plane. Information about the charged particle, including its direction of motion within the detector, can be reconstructed from the CCD readout. Additional track information is obtained from readout of the charge signal on the anode plane.
The largest existing prototype detectors each have a total of 20 L of CF4 gas within the drift region, where measurable events will occur. The group also plans to eventually construct a detector with a volume of 1 m3.
Detection of WIMPs
In a proposed dark matter event, a WIMP enters the detector volume and interacts with one of the atoms in the CF4, typically fluorineFluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
. While the WIMP does not directly leave a track, the momentum transfer of the interaction causes the atom to recoil, and its ionization track, with a typical range of a few millimeters, may be detected. CF4 gas is used because the most common fluorine isotope, 19F, is believed to be an excellent target nucleus for setting spin
Spin (physics)
In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
-dependent WIMP-nucleon
Nucleon
In physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...
scattering. If the recoiling ion is energetic enough, the direction of the incoming WIMP may be extrapolated from the direction of the recoil.
Because of the motion of the solar system around the center of the galaxy, many physicists believe that the particles comprising the dark matter halo
Dark matter halo
A dark matter halo is a hypothetical component of a galaxy, which extends beyond the edge of the visible galaxy and dominates the total mass. Since they consist of dark matter, halos cannot be observed directly, but their existence is inferred through their effects on the motions of stars and gas...
will appear to originate from a particular direction in the sky roughly corresponding to the position of the constellation Cygnus
Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...
. If this is true, the DMTPC group hope to be able to use the directional track information to statistically confirm the existence of dark matter, even in the presence of non-dark matter backgrounds which are believed to have a different directional signal. Several other groups developing low pressure TPC dark matter detectors with directional sensitivity exist, including DRIFT
Directional Recoil Identification From Tracks
The Directional Recoil Identification From Tracks detector is a low pressure negative ion time projection chamber designed to detect weakly interacting massive particles - a prime dark matter candidate....
, NEWAGE, and MIMAC. Additionally, dark matter searches such as COUPP and NEWAGE also use fluorine as the principal target nucleus for spin-dependent interactions.
See also
- Dark MatterDark matterIn astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
- Weakly Interacting Massive Particle
- Time Projection ChamberTime projection chamberIn physics, a time projection chamber is a particle detector invented by David R. Nygren, an American physicist, at Lawrence Berkeley Laboratory in the late 1970s...
- DRIFTDirectional Recoil Identification From TracksThe Directional Recoil Identification From Tracks detector is a low pressure negative ion time projection chamber designed to detect weakly interacting massive particles - a prime dark matter candidate....
Sources
- G. Jungman et al. "Supersymmetric Dark Matter". Physics ReportsPhysics ReportsPhysics Reports is a scientific journal, a review section of Physics Letters, published by Elsevier since 1971.Physics Reports publishes literature on specialized topics on physics, which are usually shorter than a monograph, oriented to physicists in all disciplines...
. 267 (1996) 195-373. doiDigital object identifierA digital object identifier is a character string used to uniquely identify an object such as an electronic document. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found...
:10.1016/0370-1573(95)00058-5 - J. D. Lewin and P. F. Smith. "Review of mathematics, numerical factors, and corrections for dark matter experiments based on elastic nuclear recoil". Astroparticle PhysicsAstroparticle physicsAstroparticle physics, the same as particle astrophysics, is that branch of particle physics that studies elementary particles of astronomical origin, and their relation to astrophysics and cosmology. It is a relatively new field of research emerging at the intersection of particle physics,...
. 6, 87 (1996). doiDigital object identifierA digital object identifier is a character string used to uniquely identify an object such as an electronic document. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found...
:10.1016/S0927-6505(96)00047-3 - S. Ahlen et al. (2009). "The case for a directional dark matter detector and the status of current experimental efforts". International Journal of Modern Physics A. doiDigital object identifierA digital object identifier is a character string used to uniquely identify an object such as an electronic document. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found...
:10.1142/S0217751X10048172. arXivArXivThe arXiv |Chi]], χ) is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, astronomy, computer science, quantitative biology, statistics, and quantitative finance which can be accessed online. In many fields of mathematics and physics, almost all...
:0911.0323 - J. B. R. Battat et al. (2009). "DMTPC: A dark matter detector with directional sensitivity". arXivArXivThe arXiv |Chi]], χ) is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, astronomy, computer science, quantitative biology, statistics, and quantitative finance which can be accessed online. In many fields of mathematics and physics, almost all...
:0907.0675v1. - S. Ahlen et al. (2010). "First Dark Matter Search Results from a Surface Run of the 10-L DMTPC Directional Dark Matter Detector". arXivArXivThe arXiv |Chi]], χ) is an archive for electronic preprints of scientific papers in the fields of mathematics, physics, astronomy, computer science, quantitative biology, statistics, and quantitative finance which can be accessed online. In many fields of mathematics and physics, almost all...
:1006.2928v2.
External links
- DMTPC web portal
- MIT News article on DMTPC (and also the MiniCLEANSnolabSNOLAB is a Canadian underground physics laboratory at a depth of 2 km in Sudbury, Ontario in Vale's Creighton nickel mine. The original Sudbury Neutrino Observatory experiment has ended, but the facilities have been expanded into a permanent underground laboratory.SNOLAB is the world's...
experiment) - Blog entry from Scientific American about dark matter and DMTPC