Detector design

miniBELEN-10A: A Reconfigurable Neutron Counter for Alpha-Induced Reactions

miniBELEN-10A: A Reconfigurable Neutron Counter for Alpha-Induced Reactions with Remarkable Consistency with data

Neutrons play a critical role in various scientific fields, including nuclear astrophysics, underground physics, and nuclear technologies. However, much of the existing data on how alpha particles induce neutron emission – (alpha, n) reactions – is outdated, incomplete, or lacks precision. The MANY (Measurement of Alpha Neutron Yields) collaboration aims to address this gap by developing advanced neutron detection systems.


miniBELEN-10A, is a novel neutron counter designed for the MANY project. It builds upon previous BELEN-type detectors, offering a groundbreaking advantage: reconfigurable design. This allows us to adapt the detector to various experimental needs. Instead of being limited to a single configuration, miniBELEN-10A offers the flexibility of multiple tools in one.

Most importantly, miniBELEN-10A boasts a "flat" efficiency – it can detect neutrons with nearly equal effectiveness across a broad energy range (up to 8 MeV). This flat efficiency is crucial for obtaining accurate measurements of neutron yields from (alpha, n) reactions.

How it Works:

miniBELEN-10A utilizes a key component to achieve its flat efficiency: strategically placed cadmium inserts. By carefully positioning the cadmium within the detector, neutrons of specific energies are absorbed, and the flatness of the energy response is improved.

At the heart of miniBELEN-10A lie ten helium-3 detectors, embedded within a high-density polyethylene (HDPE) moderator. The moderator slows down neutrons, making them easier to be detected with helium-3 proportional counters.

The Power of Reconfiguration:

The true strength of miniBELEN-10A lies in its reconfigurable design. The HDPE moderator, comprised of smaller blocks, can be disassembled and reassembled in different configurations. This allows us to tailor the detector's response to the specific requirements of any given experiment.

Testing and Validation:

The critical test for miniBELEN-10A came in the form of measuring the well-established neutron yields produced by the reaction between alpha particles and aluminum-27 – 27Al(alpha, n)30P) –. This is a well-known reaction in the scientific community, providing a benchmark for the detector's accuracy. miniBELEN-10A's measurements closely matched the data from previous experiments, demonstrating exceptional agreement within the margin of uncertainty. This successful validation confirms the detector's ability to deliver reliable and consistent results for studying (alpha, n) reactions.

key Takeaways:

  • miniBELEN-10A is a versatile and efficient neutron counter for studying (alpha, n) reactions, featuring a crucial flat efficiency achieved through the use of cadmium inserts. This flat efficiency is essential for accurate yield measurements.
  • Its reconfigurable design with ten helium-3 detectors makes it a valuable tool for the MANY project, allowing for adaptation to diverse experimental requirements. miniBELEN-10A essentially provides multiple detectors in one, offering a significant advantage for researchers.
  • The remarkable agreement between miniBELEN-10A's data and previous results on the 27Al(alpha, n)30P reaction highlights its exceptional performance and strengthens confidence in its future applications.

 Future Implications:

miniBELEN-10A paves the way for more precise measurements of (alpha, n) reactions, leading to a deeper understanding of various nuclear processes. This knowledge can benefit diverse fields, from astrophysics to nuclear technology development.

Further information:

- miniBELEN: a modular neutron counter for (alpha, n) reactions, N. Mont et al.

- Commissioning of miniBELEN-10A, a moderated neutron counter with a flat efficiency for thick-target neutron yields measurements, N. Mont et al.

Beta-delayed Neutrons. The BELEN Detector

Unveiling the Secrets of Exotic Nuclei: Radioactive isotope facilities play a crucial role in exploring the properties of exotic nuclei, particularly those rich in neutrons. However, venturing into this neutron-rich territory presents a unique challenge  beta-delayed neutrons.

Beta-delayed neutrons and their significance:

As the neutron-richness increases, the neutron separation energy (Sn) decreases, leading to a new decay mechanism: beta-delayed neutron emission.

These "beta-delayed neutrons" (βn) are crucial for:

  • Nuclear structure: βn emission probability (Pn) helps understand the daughter nucleus's level structure and β-strength distribution, and also helps determine the parent nucleus's half-life.
  • Nuclear astrophysics: Accurate knowledge of βn emitters is essential for improving models of r-process nucleosynthesis, responsible for creating half of the stable elements beyond iron.
  • Nuclear reactor applications: βn's longer response time helps maintain a controlled, subcritical state in fission reactors.

Enter BELEN: Pioneering Neutron Detection

The BELEN (BEta-deLayEd Neutron detector) is a detector designed to measure beta-delayed neutron emission probabilities of nuclei of interest in nuclear technology and physics.

Simple design, high efficiency: BELEN consists of a set of rings made of thermal neutron detectors (He-3) embedded in a high-density polyethylene (moderator) matrix. This design offers high detection efficiency within a predefined neutron energy range.

A legacy of success: The BELEN concept has been used in numerous experiments at leading facilities like GSI (Germany) and IGISOL (Finland). Different versions, optimized for specific energy ranges, have been developed by UPC and the Experimental Nuclear Physics group of IFIC. These versions, utilize a digital electronic trigger-less data acquisition system (Gasific) for accurate measurements.

BELEN-20 neutron detector at IGISOL facility (University Jyväskylä, Finland)

BELEN-48 detector at Jyvaskyla (Finland)

BELEN-48 neutron detector at IGISOL facility (University Jyväskylä, Finland)

 Computer running Gasific. Data acquisition system

DAQ using Gasific (IFIC, Valencia)

BRIKEN: The World's Most Efficient Neutron Detector Array

Building upon BELEN's success, BRIKEN (BELEN for RIKEN) stands as the world's most efficient neutron detector array. This innovation boasts 140 He-3 tubes strategically arranged in a seven "pseudo-ring" geometry. BRIKEN has been instrumental in a long-lasting experimental campaign at RIKEN (2016-2021) and can even, to some extent, measure neutron energy spectra, a capability absent in previous BELEN iterations.

BRIKEN geometry

BRIKEN detector geometry

BRIKEN detector at RIKEN facilities (Japan)

 BRIKEN and AIDA detectors at RIKEN Japan

BRIKEN and AIDA detectors at RIKEN(Japan)

The future: With the BELEN concept, we continue to push the boundaries of nuclear science, unveiling the secrets of exotic nuclei and contributing to advancements in nuclear structure, astrophysics, and reactor technology. While each BELEN ring can be approximated as a Bonner sphere, further development is ongoing to extract neutron energy information through advanced unfolding techniques.


Unveiling HENSA and NESTA: Powerful Tools for Precision Neutron Detection

HENSA: High-Efficiency Neutron Hunter

HENSA, the High Efficiency Neutron Spectrometry Array, is a cutting-edge detector system born from a collaborative effort of eight leading research institutions. This innovative technology offers exceptional energy resolution, ranging from meV to GeV, making it ideal for studies in low-radioactivity environments like underground laboratories and cosmic-ray investigations.

Understanding the Neutron Challenge

Ever-present neutrons, hailing from cosmic rays and natural radioactivity, bombard our world. This constant barrage forms a background radiation that poses a three-fold challenge:

  • Scientific Interference: Neutrons can disrupt sensitive experiments, hindering our quest for knowledge in fields like astrophysics and dark matter research.
  • Microelectronic Threats: In delicate electronic devices, neutron interactions can induce errors, potentially leading to malfunctions.
  • Environmental Radiation: Neutrons contribute to the natural radiation dose we receive, and understanding their presence is crucial for environmental safety assessments.

HENSA's strength lies in its ability to precisely measure this neutron flux. By dissecting this radiation, researchers can not only identify its sources but also assess their impact on various scientific endeavors and technological applications.

Diverse Applications of HENSA

  • Environmental Monitoring: HENSA safeguards public health by assessing radioactivity levels in the surrounding environment.
  • Cosmic Ray Studies: It unveils the secrets of cosmic rays and space weather events, improving our understanding of their influence on Earth.
  • Microelectronics Protection: HENSA helps identify and mitigate potential threats from neutron-induced errors in electronic devices, ensuring their reliability.
  • Underground Research: By effectively characterizing the neutron background in underground facilities, HENSA empowers sensitive experiments in neutrino, dark matter, and nuclear astrophysics, paving the way for groundbreaking discoveries.

Neutron Spectrometry Array located at the tunnel of LSC (Canfranc, Huesca)

HENSA's Superiority: Beyond Detection

Unlike traditional detectors, HENSA offers both high-efficiency neutron detection and detailed energy information. This enhanced sensitivity translates to several crucial advantages:

  • Improved Background Characterization: HENSA precisely dissects the neutron background in underground labs, allowing researchers quantify the effect of neutrons produced by surrounding materials in their low-background experiments.
  • Enhanced Experiment Precision: HENSA's superior resolution minimizes background noise, leading to more accurate and reliable results in sensitive experiments searching for rare phenomena like neutrinos and dark matter.

HENSA in Action: Mapping the Neutron Landscape

The first HENSA campaigns have yielded valuable data. They successfully measured neutron fields within the LSC underground laboratory and mapped cosmic-ray neutron flux across various locations in Spain. This information provides crucial insights into the impact of neutrons on different experiments and geographical regions.

Neutron Spectrometry Array at Astun, Huesca (2100 m)

Neutron Spectrometry Array at ETSEIB, Barcelona (120 m)

Neutron Spectrometry Array at LSC facilities (Canfranc, Huesca)

NESTA: HENSA's Agile Sibling

NESTA, the Nested Neutron Spectrometry Array, is a portable version of HENSA designed for the fast-paced environment of accelerator facilities. Optimized for the n_TOF facility at CERN, NESTA inherits several key features from HENSA:

  • High-Energy Sensitivity: NESTA boasts a broad energy range similar to HENSA, ensuring comprehensive neutron detection.
  • Modular Design: Its flexible configuration allows for easy adaptation to diverse experimental needs, maximizing its utility.
  • Pulsed Neutron Expertise: NESTA effectively tackles the challenge of characterizing pulsed neutron backgrounds commonly encountered in accelerator facilities.

High Density Polyethylene matrix for NESTA

NESTA, high-density polyethylene matrix for n_TOF-CERN

The Future of Neutron Detection

HENSA and NESTA represent a significant leap forward in neutron detection technology. Their ability to provide detailed spectral information and operate in various environments makes them invaluable tools for researchers across a wide range of scientific disciplines. These powerful tools are poised to revolutionize our understanding of neutrons and their influence on our world, opening doors to groundbreaking discoveries in the years to come.

Neutron dosimeters

Unveiling LINrem: A Revolutionary Neutron Dosimeter for the Future

The Challenge: Precisely Measuring High-Energy and Pulsed Neutrons

Neutrons can significantly contribute to the total radiation dose received by individuals in various settings, including workplaces, medical facilities, and the general public. Accurately detecting neutrons, particularly those with high energy and encountered in pulsed fields, is crucial for ensuring proper radiation protection. However, current commercially available solutions often have limitations:

  • Dated technology: Combining sensor technology from the 1960s with readout systems from the 1990s.
  • Limited portability: Weighing 9-18 kg per unit, hindering flexibility.
  • Poor response for high-energy neutrons (above 20 MeV) and pulsed fields: Less reliable in environments with these specific neutron characteristics.
  • Unsuitable for complex fields: Struggle to accurately measure intricate pulsed or quasi-continuous neutron fields.

Our Response: The LINrem Project

Our research group is addressing these challenges by developing the LINrem neutron counter, a next-generation dosimeter designed to overcome the limitations of existing solutions, particularly regarding portability and measurement accuracy. LINrem specifically focuses on improving measurement accuracy for three critical aspects:

  • Weight reduction: Essential for enabling portability in locations with difficult access and facilitating neutron dose mapping in standard rooms.
  • High-energy neutrons: Crucial for fields like particle therapy, where high-energy neutrons can be present.
  • Pulsed neutron fields: Encountered in facilities using particle accelerators, such as synchrotrons and cyclotrons, and increasingly relevant due to their growing application in various research and technological domains.

LINrem's Cutting-Edge Technology:

  • Modern design: Utilizing computer-assisted optimization for the detection module.
  • Novel acquisition technology: Implementing a new approach to handle complex radiation fields, including pulsed fields.
  • Digitalization: Employing digital electronics and applications for acquisition and readout.

LINrem dosimeter version 3

Light weight LINrem dosimeter (v3)

Extended LINrem dosimeter version 3

Extended energy LINrem dosimeter (v3)

LINrem's Achievements and Advantages:

  • Demonstrator prototypes: Successfully developed and tested in relevant environments, including those generating pulsed neutron fields.
  • Excellent agreement with benchmark calculations: Demonstrating the accuracy of LINrem's response in both high-energy and pulsed fields.
  • Out-of-field neutron measurements: Successfully achieved in proton therapy settings using the LINremext1 prototype, showcasing its ability to handle complex pulsed fields encountered in such environments.
  • Dose measurement results: Demonstrating reliable H*(10) dose measurements, even for both high-energy neutrons and those present in pulsed fields.
  • Transferable to users: LINrem prototypes are nearing a stage where they can be readily adopted by users for applications involving pulsed neutron fields.

 LinREM dosimeter at a therapy facility

LINrem dosimeter at a proton therapy facility

The Future of LINrem:

We are actively working on further advancements:

  • Integration: Combining electronics, data acquisition systems, and front-end elements into a single, portable module suitable for both continuous and pulsed fields.
  • Adaptation to new standards: Modifying the LINdos detector design to comply with the latest ICRU95 recommendations.
  • SINERGY4HT project: Developing a combined system for in-vivo diagnosis in hadron therapy, simultaneously measuring neutrons and prompt gamma rays, with an emphasis on its potential application in pulsed beam environments.

The LINrem project holds immense potential for revolutionizing neutron dosimetry, with a specific focus on overcoming challenges related to both high-energy and pulsed neutron fields. By offering a cutting-edge, portable, and accurate approach, LINrem paves the way for enhanced radiation protection in various fields, ultimately contributing to a safer and healthier future.