SIMPLE (Superheated Instrument for Massive ParticLe Experiments) is an experiment search for direct evidence of
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 ...
. It is located in a 61 m
3 cavern at the 500 level of the
Laboratoire Souterrain à Bas BruitLSBB near
Apt
Apt. is an abbreviation for apartment.
Apt may also refer to:
Places
* Apt Cathedral, a former cathedral, and national monument of France, in the town of Apt in Provence
* Apt, Vaucluse, a commune of the Vaucluse département of France
* A ...
in southern
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...
. The experiment is predominantly sensitive to
spin-dependent interactions of
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 ...
(or WIMPs).
SIMPLE is an international collaboration with members from
Portugal
Portugal, officially the Portuguese Republic, In recognized minority languages of Portugal:
:* mwl, República Pertuesa is a country located on the Iberian Peninsula, in Southwestern Europe, and whose territory also includes the Macaronesian ...
,
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...
, and the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...
.
Design
The SIMPLE detector is based on
superheated droplet detectors (SDDs), a suspension of 1–2% superheated liquid C
2ClF
5 droplets (~30 μm radius) in a viscoelastic 900 ml gel matrix, which undergo transitions to the gas phase upon energy deposition by incident radiation. The
refrigerant
A refrigerant is a working fluid used in the refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulate ...
,
freon
Freon ( ) is a registered trademark of the Chemours Company and generic descriptor for a number of halocarbon products. They are stable, nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol prop ...
, is used as the active mass.
In effect, each droplet behaves as a miniature
bubble chamber. Once a
nucleation
In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that de ...
has occurred, the acoustic shock wave is picked up by microphones. Each acquired signal is then fully discriminated in terms of acoustic external noise, gel-associated noise and most recently
particle discrimination. The detectors are typically operated at ~200
kPa and ~280
K. Due to the construction technique, SSDs are almost insensitive to
background radiation
Background radiation is a measure of the level of ionizing radiation present in the environment at a particular location which is not due to deliberate introduction of radiation sources.
Background radiation originates from a variety of source ...
, and their sensitivity can be adjusted by controlling the temperature and pressure of each device.
Results
The final phase II analysis was published in Physical Review Letters in 2012.
Spin-dependeant cross section limits were set for light WIMPs.
References
The SIMPLE Phase II dark matter search (2014)Fabrication and response of high concentration SIMPLE superheated droplet detectors with different liquids (2013)Final Analysis and Results of the Phase II SIMPLE Dark Matter Search (2012)Reply to Comment on First Results of the Phase II SIMPLE Dark Matter Search (2012)Comment on First Results of the Phase II SIMPLE Dark Matter Search (2012)First Results of the Phase II SIMPLE Dark Matter Search (2010)SIMPLE dark matter search results (2005)
External links
SIMPLE experiment website
{{Dark matter
Experiments for dark matter search