Author Archives: Rafael Lang

XMASS Members join XENON

XENON1T is the largest and most sensitive WIMP dark matter detector to date, recording scientific data in the Italian Laboratori Nazionali del Gran Sasso (LNGS). Our collaboration recently grew larger again and now has more than 160 members from 27 institutions. As of December 1st, 2017, key members of the Japanese XMASS collaboration have officially joined XENON and will contribute to the realization of the upcoming XENONnT.

Participants of our collaboration meeting early 2018 in Florence, including our newest colleagues from the Japanese XMASS collaboration.

XMASS is a single-phase liquid xenon experiment in the Kamioka mine, the Japanese underground laboratory hosting the Nobel-prize winning SuperKamiokande experiment. Researchers come from the University of Tokyo (groups of Prof. Shigetaka Moriyama and Prof. Kai Martens), Nagoya University (group of Prof. Yoshitaka Itow) and Kobe University (group of Prof. Kentaro Miuchi). XMASS will continue to record data until the end of this year, in line with the planned start of XENONnT.

XENONnT is an upgrade phase to the currently running XENON1T experiment. With a target mass three times larger than XENON1T, and a considerably reduced background, XENONnT will explore WIMP-nucleon interactions with a ten-fold higher sensitivity than XENON1T. The Japanese groups bring expertise in LXe detector technologies and low background experiments relevant to the XENON Dark Matter program. We are excited about our newest collaborators from Japan as we continue to move forward with the XENON program at LNGS.

Water Tank Filling

We started to fill the water tank:

In this view from the top, the cryostat with the actual detector is visible on the left. Photomultiplier tubes of the water Cherenkov muon veto are seen at the bottom and side of the water tank, to the right of the image.

In this view from the top, the cryostat with the actual detector is visible on the left. Photomultiplier tubes of the water Cherenkov muon veto are seen at the bottom and side of the water tank, to the right of the image.

The water acts as a passive shielding against external radioactivity. In addition, using the photomultipliers that can be seen towards the right of the picture, the water acts as an active muon detector. Muons may induce events in the xenon detector that may mimic dark matter signals. We therefore turn a blind eye (“veto”) for a short time whenever a muon travels through the water tank.

XENON1T First Light

Today XENON1T has seen its first light:

firstlightThis is literally the first event recorded by the detector in that is is a single photon that was detected by one of the photomultipliers and recorded by the whole XENON1T data acquisition setup. What you can see from the picture is that our noise is indeed very low compared to the smallest possible signal – that of a single photon! And this is even without any fine-tuning of our electronics yet.

The detector is still empty and we are checking the photomultipliers one by one before making first background measurements. Filling with liquid xenon will happen as soon as those tests are concluded successfully.

Gran Sasso Lab on Google Street View

The Gran Sasso laboratory that hosts the XENON1T experiment is the largest underground laboratory in the world. More than a dozen different experiments make use of the low background from cosmic radiation that you get when you go more than a mile deep underground. You can virtually walk around the lab using the Street View from Google Maps.

The lab also offers public tours, just get in touch with them directly if you want to walk around in person.

Farewell to ICARUS

The ICARUS experiment just left Hall B at the Gran Sasso underground laboratory in Italy for its journey to CERN in Switzerland. We had designed the XENON1T water tank a bit smaller than originally planned to allow ICARUS to move past. Everything went smoothly, but it was a tight fit…

ICARUS moving

Part of the ICARUS experiment is hanging from the large crane in Hall B of the Gran Sasso underground lab, tightly squeezing past the XENON1T water tank on its way to CERN.

We wish our colleagues all the best with the future of their experiment. Read the full story of this move at

Nitrogen Tanks Installed

We use liquid and gaseous nitrogen for a variety of things: Liquid nitrogen is used to initially liquefy the xenon and to keep the xenon cold in case of power failures. Gaseous nitrogen is mainly used as a blanket on top of the water inside the muon veto in order to keep radioactive radon gas out. Our two nitrogen storage tanks have been delivered, installed, and tested:

Nitrogen Tanks

Dr. Marcello Messina (from Columbia University) and Dr. Domenico Franco (from Zürich University) underground in front of the two XENON nitrogen storage tanks.


Cryogenic Pipe Installed

The XENON1T detector sits in the center of a large water tank. All the signal and high voltage cables, pipes for liquid and gaseous xenon, vacuum piping and various other lines get there via one large pipe.

Installation of the cryogenic pipe inside the XENON1T water tank, July 2014

Installation of the cryogenic pipe inside the XENON1T water tank, July 2014

We have just finished the installation of this pipe. It’s actually a quite fascinating piece of engineering. In it, there are all the signal and high voltage cables for the photomultiplier tubes. There are pipes to recirculate the xenon for purification in the adjacent building, which are themselves inside a vacuum-insulated pipe that in turn runs inside this pipe. The large diameter pipe is also used to evacuate the cryostat, as well as the heat insulation of the cryostat. And it holds a bunch of extra cables and wires for various other sensors. So, it’s really much more than just a pipe. It’s the lifeline to the detector. And it’s pretty cramped:

Cable bunches

These are the signal wires, bunched together into a single pipe inside the cryogenic pipe. They are PTFE-insulated, low-radioactivity wires with custom-made connectors.