Highly sensitive experiment to detect dark matter
The Netherlands helped build the most sensitive dark matter detector ever
An international collaboration of scientists, with UvA professor Patrick Decowski and his team, inaugurated the new XENON1T experiment in the underground Gran Sasso laboratory in Italy. It is designed to search with an unprecedented sensitivity for dark matter, one of the main ingredients of the universe.
The Universe consists of five times more dark matter than the ordinary matter we are familiar with, made up of atoms and molecules. Nonetheless, this mysterious dark matter has still not been detected directly. For decades, laboratory-based experiments have searched for it. Dark matter has so far only been detected indirectly, via gravity interactions that govern the motion of astrophysical objects.
Scientists expect that dark matter consists of a new, stable elementary particle that has thus far escaped detection. “We expect that every second about one hundred thousand dark matter particles pass through an area the size of a thumbnail,” says Patrick Decowski, programme leader of the Dark Matter research group at Nikhef, the National institute for subatomic physics in Amsterdam. “The fact that we haven’t detected them yet, tells us that the probability that the particles collide with atoms in our detector is very small and that we need more sensitive experiments to uncover them. XENON1T is such an experiment.”
Laboratory 1400 meters underground
XENON1T is located in the Laboratori Nazionali del Gran Sasso in Italy, one of the largest underground laboratories in the world. “We perform our experiment in a water tank, 1400 meter underground, because we want to detect only dark matter, and filter out all other types of radiation. The massive layer of rock and the water shield off the sensitive equipment,” according to Decowski.
It took 20 research groups from 10 countries five years to complete the experiment. As soon as XENON1T is fully operational, it will take about a week for the experiment to become the most sensitive dark matter experiment in the world. With a total mass of 3500 kg it is the third generation of instruments in the XENON project that started 15 years ago. XENON1T is named after the noble gas xenon, with which the detector is filled. A collision of dark matter with xenon results in a tiny flash of light. 248 extremely sensitive light sensors will be searching for such flashes. The first results are expected early 2016.
Research group Dark Matter
Patrick Decowski is professor at the UvA Institute of Physics and programme leader of the Dark Matter research group at Nikhef, The National institute for subatomic physics. The Dutch Nikhef team, which also includes Auke-Pieter Colijn and Frank Linde, was responsible for, among other aspects, the vibration-free suspension of the xenon vessel, as well as the data acquisition and data analysis software. Decowski has a prominent role in the GRAPPA (GRavitation and AstroParticle Physics in Amsterdam) center of excellence which is also a research priority area of the UvA.