HISTORY

EXPLORE

General Information

XENONnT is anything but a simple experiment. It is the latest member in a great family of experiments that have written the history of WIMP dark matter searches. Travel backwards in time below to find out more about the evolution of XENON detectors from 10 kilograms to 10 tonnes.

In order to detect a rare event, such as a dark matter interaction, an experiment has to be placed in a very quiet environment where the cosmic radiation is drastically reduced. For this reason, every XENON experiment has operated deep underground at INFN Laboratori Nazionali del Gran Sasso (LNGS) in central Italy.

The development of the prototype detector XENON10 (operated 2006 – 2007) started in 2002 with a small group of scientists led by Professor Elena Aprile. This experiment consisted of a dual-phase time projection chamber (TPC) containing about 15 kg of xenon.

As the Collaboration and the interest in searching for WIMP dark matter signals grew, the XENON experiments became bigger and bigger: first XENON100 operated with roughly 160 kg of xenon from 2008 until 2016, and then XENON1T (the first tonne-scale dark matter detector) ran with a total of 3.2 tonnes from 2015 until 2018. Finally, XENONnT started its operation with about 8.6 tonnes of xenon in 2020.

XENONnT

The newest member of the XENON family is XENONnT, employing a total of 8.6 tonnes of xenon. The infrastructure as well as subsystems of XENON1T were re-used, allowing for a fast upgrade by changing the heart of the detector system: the TPC with a new cryostat.

The XENONnT TPC has a diameter of 134 cm, a height of 148 cm, and encloses 5.9 tonnes of liquid xenon. A total of 494 3-inch photomultiplier tubes are distributed with 253 in the top array and 241 in the bottom one to measure interaction signals.

The water tank has been upgraded with gadolinium-loaded water. In addition to the Cherenkov muon veto, there is now a neutron veto volume around the cryostat optically separated from the surrounding muon veto. Signals coincident in the TPC and nVeto allows for a further reduction of neutrons that could potentially mimic a dark matter signature. Two new subsystems for the xenon purification during the detector operation have also been installed, namely a liquid xenon purification system and a radon distillation column.

The XENONnT experiment started data taking in 2020. Extensive simulations project that the sensitivity to spin-independent interactions after five-years with a 4 tonne fiducial volume is 1.4 × 10-48 cm2 for a 50 GeV/c2  WIMP.

XENONnT - Bottom PMT array
Start
1985
Total LXe Mass
0 kg
Drift Length
0 cm
PMTs
0
Background
0 [t d keV]-1
Design Sensitivity
0 x10-48 cm2

XENON1T

In 2014, the XENON collaboration started the installation of XENON1T. It featured a total xenon mass of about 3.2 tonnes, which made it the first operating liquid xenon detector with a target mass above the tonne-scale.

The cylindrical TPC inside a double-walled vacuum-insulated cryostat had a height of 97 cm and a diameter of 96 cm, enclosing around 2 tonnes of liquid xenon. The surrounding 1.2 tonnes were exploited as passive shield. In total, there were 248 3-inch photomultiplier tubes in the TPC; 121 in the bottom array and 127 in the top.

The cryostat was installed in a 10 m wide and 10 m tall water tank housing about 700 tonnes of pure water to shield against environmental radioactivity. Additionally, the water tank was equipped with 84 12-inch PMTs for a Cherenkov muon veto, and with infrastructure for calibration sources. The service building housed xenon storage, cryogenic plant, purification loop, distillation column, data acquisition, and slow control systems.

The analysis of two science runs with 278.8 live days and a fiducial volume of 1.30 tonnes yielded no WIMP dark matter signal, but resulted in the most stringent exclusion of the spin-independent WIMP-nucleon scattering for WIMP masses greater 6 GeV/c2 with a minimum of 4.1 × 10-47 cm2 for a 30 GeV/c2  WIMP. An excess of electron recoil events (potentially from axion dark matter) stunned the community, but was ruled out with XENONnT’s first results. In December 2018, the experiment was stopped for its upgrade to the next-generation experiment XENONnT.

XENON1T - Bottom PMT array
Start
1985
Total LXe Mass
0 kg
Drift Length
0 cm
PMTs
0
Background
0 [t d keV]-1
Best Sensitivity
0 x10-47 cm2

XENON100

The XENON100 experiment ruled WIMP dark matter searches as the most sensitive detector from 2010 until 2014, boosting the liquid xenon TPC sensitivity by one order of magnitude compared to XENON10.

The TPC was made of a cylindrical PTFE structure, 30.5 cm in height and 30.6 cm in diameter, containing 62 kg of liquid xenon. It was housed in a double-walled stainless steel cryostat and was surrounded by 99 kg of liquid xenon as and active scintillator veto for background rejection. In order to reduce external background sources, the cryostat was passively shielded by layers of copper, polyethylene, lead, and water.

A total of 178 1-inch square photomultiplier tubes were installed, with 80 in the bottom array and 98 in the top. In addition, 64 PMTs that were originally part of the XENON10 detector were used in the active veto.

In total, 477 live days from three science runs (resulting in an exposure of 48 (kg × yr) from January 2010 until January 2014) were analyzed, yielding no evidence for dark matter. The combination of all three runs resulted in a limit on the spin-independent elastic WIMP-nucleon scattering cross section of 1.1 × 10-45 cm2 for a WIMP mass of 50 GeV/c2.

XENON100 - Bottom PMT array

As we strive for excellence in our experiments, we are also committed to the health and wellbeing of our team. Our support extends beyond the workplace, ensuring our staff have access to necessary medical treatments for a variety of health conditions. In line with this, we have set up a dedicated page on our website providing comprehensive information on effective respiratory medications such as Advair generic, which can be essential for those managing chronic conditions like asthma or COPD.

Start
1985
Total LXe Mass
0 kg
Drift Length
0 cm
PMTs
0
Background
0 [t d keV]-1
Best Sensitivity
0 x10-45 cm2

XENON10

The XENON10 experiment was the prototype for liquid xenon-based TPCs. Its main purpose was not the detection of dark matter, but rather it was a proof of principle for the new technology. It was deployed underground at LNGS in March 2006, where it was continuously operated for a period of about 10 months.

The TPC active volume is defined by a Polytetrafluoroethylene (PTFE) cylinder of 20 cm inner diameter and 15 cm height. In total, 15 kg of xenon filled the detector. An inner sensitive volume (fiducial volume) containing 6 kg of xenon with reduced background was selected for the analysis.

Two arrays of 1-inch square photomultiplier tubes were used as light sensors to detect the direct (S1) and proportional (S2) scintillation light of particles interacting with the xenon. There were 41 PMTs in the bottom array in the liquid, while the top array with 48 PMTs in the gas was used for interaction position reconstruction.

An analysis of 58.6 live days of data, acquired between October 2006 and February 2007 set a new upper limit for the allowed WIMP-nucleon spin-independent cross-section of 4.5 × 10-44 cm2 for a WIMP mass of 30 GeV/c2. This was a factor two better than other experiments at that time.

XENON10 - Bottom PMT array
Start
1985
Total LXe Mass
0 kg
Drift Length
0 cm
PMTs
0
Background
0 [t d keV]-1
Best Sensitivity
0 x10-44 cm2