We are very glad to announce that two NEXT papers have been published in two Physical Review Journals by the American Physical Society. You can click on the links attached below to check them out.

- “Neutral Bremsstrahlung Emission in Xenon Unveiled” appeared in Physical Review X at the beginning of April: https://journals.aps.org/prx/abstract/10.1103/PhysRevX.12.021005

- “Measurement of the 136-Xe two-neutrino double beta decay half-life via direct background subtraction in NEXT” was published in Physical Review C around the middle of May: https://journals.aps.org/prc/abstract/10.1103/PhysRevC.105.055501

If you are interested in more NEXT publications, go to section DOCUMENTS!

We are really glad to announce that Francesc Monrabal, our NEXT colleague, has just been awarded the prestigious Starting Grant by the European Research Council (ERC).

For those who don’t know, the ERC -the premier European funding organization for vanguard research- awards the most promising early-career researchers with ERC Starting Grants so as to develop and launch their own projects. This grant is absolutely esteemed, seeing that only less than 10% of the candidates end up obtaining the €1.5 million help.

The honouree Francesc Monrabal, long-time NEXT collaborator and already an expert on gaseous TPCs, will be able to set up and develop the GanESS project, which stands for Gaseous detector for Neutrino physics at the ESS. It is meant to exploit coherent elastic neutrino-nucleus scatterings to detect neutrinos and explore physics beyond Standard Model. The main advantage of this technique, in comparison with the rest of usual neutrino-detection experiments, is that very large detectors with tons of active materials are not required.

Francesc working on the NEXT-White TPC, at the LSC. Photo: Javier Larrea

The final stage of the experiment is planned to be constructed in Lund (Sweden) so as to use the upcoming European Spallation Source (ESS), which will be located at the same place. The detector concept will correspond to a Time Projection Chamber (TPC) filled with 20 kg of xenon gas, analogous to the NEXT’s technology, that will allow detecting more than 7,000 events per year. The operation of this detector is expected to start in 2026. Until then, construction and operation of smaller prototypes will comprise the first stage within the experiment program, with the aim of testing and studying the detector technology.

In these last days of 2021, it is pretty common to look back upon the past year and consider all the endeavors we have made. For us, it has been a really remarkable year: it has meant the farewell of our large-scale operative detector NEXT-White, but also we have achieved superb progress within the NEXT program in terms of the MC & software development, NEXT-100 construction, and R&D for the next-generation detectors.

However, we aren’t fully pleased yet: we believe that the upcoming 2022 year will be an even more special one for us. It will comprise a crucial landmark in the schedule of the NEXT experiment, since we expect the NEXT-100 detector to be taking data by the end of the year! We have been looking forward to that moment for a long time, so we also hope that during 2022 some of your dreams come true too!

Merry Christmas & Happy Hanukkah!

The year 2021 is about to come to an end, and we want to publish a new post, since it has meant a significant milestone inside the NEXT programme: the end of the NEXT-White (NEW) detector operation.

This detector implemented the second phase of the NEXT programme. Being a ∼1:2 scale model of NEXT-100, NEW was the largest high pressure xenon (HPXe) gas Time Projection Chamber (TPC) using electroluminescent (EL) amplification in the world. It was located at Laboratorio Subterráneo de Canfranc (LSC), Huesca, under Tobazo Mountain in order to reduce the external backgrounds.

It was conceived to validate the HPXe-EL technology in a large-scale radiopure detector. In particular, the main tasks considered were: (1) the assessment of the robustness and reliability of the technological solutions, (2) the demonstration of the excellent energy resolution and signal over background discrimination expected, (3) the characterization of the backgrounds affecting the experiment (validation of background model) and (4) the two-neutrino double beta decay half-life measurement for 136-Xe.

Around 2013-2014 came up the idea of having this prototype of the NEXT-100 detector to achieve the multiple goals commented just above. During 2014, some components of NEW started to be developed and constructed. At the beginning of 2015, the lead castle and the seismic platform were already builded and placed at the LSC. The energy plane, tracking plane and field cage were installed one year later, when the electronics and gas systems were completed as well. It was mid-2016 and we were ready to switch it on!

NEXT-White construction.

Operation

In November 2016, the official operation campaign of NEW started with Run-I, a short engineering run that took one month approximately. After that, the first physics results appeared within the Run-II period, taken from March 2017 to November of the same year. This run was basically intended to understand the performance of the detector and to study the calibration strategy that would be followed, as well as to check the excellent energy resolution expected. The characterization of the radon-induced backgrounds affecting NEXT was also performed.

Run-III and Run-IV periods were not useful in terms of the analysis. The first one corresponded to a very short Run (around 3 months, starting on December 2017) full of problems that did not allow the data-taking, while Run-IV -intended to measure the radiogenic backgrounds, from August 2018 to December 2018- found out some reducible background sources that were masking the energy spectrum. Thanks to the later one, a Radon Abatement System started to be used, and an inner lead castle was placed around the TPC (and inside the other lead structure).

At the beginning of 2019, the data-taking period devoted to the 2vββ measurement started. From that point on up to mid-2020, the extensive low-background Run-V was taken with 136-Xe-enriched xenon inside the chamber. After that, the Run-VI —with 136-Xe-depleted xenon— took place from October 2020 to June 2021.

Data exposure evolution during the final data-taking period.

It has been some months since the data-taking of NEW stopped, and we can ensure that —after a lot of hard work and patience— all the proposed goals have been fulfilled successfully!

Finally, we would like to take the opportunity to remember our friend and collaborator James White, who was one of the key scientists of the NEXT collaboration. This detector was named after him, and we hope and believe he would be proud of the results obtained with it.

James in the lab.