News: HENSA++ campaign going on at Zaragoza

Barcelona, Spain (March 13, 2024)

The ENPAI research group, part of the Advanced Nuclear Technology (ANT) group at Universitat Politècnica de Catalunya (UPC), is excited to announce a two-week campaign to measure neutrons generated by cosmic rays. This innovative project utilizes the newly developed HENSA++ spectrometer, a significant advancement built by the collaborative efforts of ENPAI (UPC) and the Institute of Fundamental Physics (IFIC) of the Spanish National Research Council (CSIC).

HENSA++ detector setup

HENSA++ setup at University of Zaragoza

The HENSA++ spectrometer is a state-of-the-art neutron detection system designed for high-efficiency measurements across a wide energy range. Its versatility allows use in various settings, including outdoor field experiments. In this campaign, the spectrometer is currently being deployed near the IAXO laboratory hall in Zaragoza, Spain.

This campaign marks a collaborative effort between ENPAI (UPC) and the IAXO (Investigation of the Axial Dark Matter Experiment) team at the University of Zaragoza. The IAXO team is constructing a groundbreaking experiment to detect dark matter, the enigmatic substance composing roughly 27% of the universe. The HENSA++ campaign aims to measure the background neutron flux at the planned IAXO experiment site. This crucial data will be instrumental in both designing the IAXO experiment and optimizing its sensitivity for dark matter detection.

The campaign will consist of two key phases, each lasting one week. The first phase is currently being conducted outdoors, in close proximity to the IAXO laboratory hall (University of Zaragoza, Spain). This open-air environment allows for neutron measurement without interference from walls, roofs, or other physical structures. Following that, the second phase will take place inside the IAXO laboratory itself. Here, the researchers will study how nearby walls and structures influence the background neutron levels.

HENSA++ detector at open space of the University of Zaragoza

HENSA++ in a open field measurement (Zaragoza)

By analyzing the data collected throughout these two phases, scientists aim to gain a deeper understanding of cosmic ray neutrons and provide valuable insights to aid the IAXO team in their search for dark matter.


The ENPAI research group, within the ANT group at UPC Barcelona, is a renowned leader in the field of experimental nuclear physics, applications, and instrumentation (ENPAI). Their expertise and innovative research have been recognized in prestigious scientific publications and presentations at international conferences.

About IAXO

The IAXO experiment represents a novel endeavor in the quest to detect dark matter. This international collaboration involves scientists from Spain, Italy, and the United States, with a projected completion date of 2025.