Periodic Reporting for period 2 - ACCESS (Array of Cryogenic Calorimeters to Evaluate Spectral Shapes)
Berichtszeitraum: 2024-04-02 bis 2025-04-01
The search for neutrinoless double-beta decay (0νββ) is central to understanding fundamental questions in particle physics, such as the nature of neutrinos and the origin of matter-antimatter asymmetry.
Observing 0νββ would confirm that neutrinos are Majorana particles and provide insights into their absolute mass.
However, theoretical uncertainties in nuclear matrix elements hinder the precise interpretation and optimal selection of isotopes for experiments.
In this framework, the ACCESS (Array of Cryogenic Calorimeters to Evaluate Spectral Shapes) project aims to develop a novel technique for precision measurements of rare and forbidden β-decays, which can serve as an essential benchmark for nuclear physics calculations and represent a significant background in astroparticle physics experiments. ACCESS aims to operate cryogenic calorimeters based on natural and doped crystals containing β-emitting radionuclides. In this way, natural (e.g. Cd-113 and In-115) and synthetic isotopes (e.g. Tc-99) will be simultaneously measured with a common experimental technique, providing valuable data for data-driven improvements of nuclear models.
Observing 0νββ would confirm that neutrinos are Majorana particles and provide insights into their absolute mass.
However, theoretical uncertainties in nuclear matrix elements hinder the precise interpretation and optimal selection of isotopes for experiments.
In this framework, the ACCESS (Array of Cryogenic Calorimeters to Evaluate Spectral Shapes) project aims to develop a novel technique for precision measurements of rare and forbidden β-decays, which can serve as an essential benchmark for nuclear physics calculations and represent a significant background in astroparticle physics experiments. ACCESS aims to operate cryogenic calorimeters based on natural and doped crystals containing β-emitting radionuclides. In this way, natural (e.g. Cd-113 and In-115) and synthetic isotopes (e.g. Tc-99) will be simultaneously measured with a common experimental technique, providing valuable data for data-driven improvements of nuclear models.
Within the ACCESS project, the researcher consolidated his knowledge and skills in the fields of crystal production and characterization as room-temperature scintillators, material purification and screening for low-background applications, and the investigation of forbidden beta decays of specific nuclei. In particular, the researcher focused on:
- Measurement of Indium-115 beta decay with indium iodine and indium oxide cryogenic calorimeters;
- new limit on Tantalum-180m beta decay, first with gamma-spectrometry and then with a lithium tantalate cryogenic calorimeter;
- new limit on Vanadium-50 beta decay, first with gamma-spectrometry and then with a yttrium vanadate cryogenic calorimeter;
- new limit on Zirconium-96 and Zirconium-94 beta decay, first with gamma-spectrometry and then cesium-zirconium-cloride low-temperature scintillator;
- measurement of Technetium-99 beta decay using tellurium dioxide and lithium molybdate crystals operated as cryogenic calorimeters.
Within the framework of the ACCESS project, new cryogenic calorimeters based on indium oxide and indium iodide have been developed, yielding one of the most precise measurements of the Indium-115 beta decay.
On the Technetium-99 side, we measured both samples of tellurium dioxide produced by SICCAS and doped with Technetium-99 using a mass spectrometer and cryogenic detectors. However, we encountered technical problems due to the segregation of Technetium-99 in the crystal. After several attempts to optimize the procedure, we decided to develop an innovative approach to introduce Technetium-99 into a crystal, activating Technetium-99 from Molybdenum-98 in a natural lithium molybdate crystal.
The ACCESS project significantly enriched the host institution, Queen’s University, by introducing advanced expertise in cryogenic calorimetry and nuclear spectral shape measurements. The researcher contributed to the development of new experimental protocols, introduced novel simulation and data analysis tools, and initiated interdisciplinary collaborations. This two-way transfer of knowledge not only advanced the researcher’s skills but also expanded the scientific capabilities of the host institutions in a new research field.
In the final year, the research activities focused on enhancing cryogenic infrastructure, testing new detector configurations, and continuing spectral shape measurements. Several detector prototypes were installed and tested using NTD sensors. A new mechanical support for the pulse-tube was developed to mitigate vibrational noise. TES readout has been installed, but is still under testing. Transition measurements were performed on superconducting films. Crucial experimental work was conducted on a range of crystals (PbWO4, Li2MoO4, Na2Mo2O7, NaCl, and Li2WO4), including irradiated samples aimed at embedding beta-emitting isotopes (e.g. Tc-99, Cl-36) for direct measurement. Although some of these tests are still ongoing and have faced technical delays, promising preliminary results have been achieved. Monte Carlo simulations were further developed to incorporate new detector designs, thus supporting detector development and data analysis.
The main scientific achievement remains the high-precision measurement of the In-115 beta decay spectrum, which was disseminated in a widely cited PRL publication. The spectral data were shared with theoretical groups and used for model comparison studies published in Phys. Rev. C.
Throughout the three years, ACCESS results were disseminated via presentations at major international conferences (e.g. NEUTRINO, LRT, LTD, TAUP, MEDEX), publications in peer-reviewed journals, and open-access data repositories. Outreach activities included seminars for schools, public events like Pint of Science and SHARPER, and a dedicated website.
- Measurement of Indium-115 beta decay with indium iodine and indium oxide cryogenic calorimeters;
- new limit on Tantalum-180m beta decay, first with gamma-spectrometry and then with a lithium tantalate cryogenic calorimeter;
- new limit on Vanadium-50 beta decay, first with gamma-spectrometry and then with a yttrium vanadate cryogenic calorimeter;
- new limit on Zirconium-96 and Zirconium-94 beta decay, first with gamma-spectrometry and then cesium-zirconium-cloride low-temperature scintillator;
- measurement of Technetium-99 beta decay using tellurium dioxide and lithium molybdate crystals operated as cryogenic calorimeters.
Within the framework of the ACCESS project, new cryogenic calorimeters based on indium oxide and indium iodide have been developed, yielding one of the most precise measurements of the Indium-115 beta decay.
On the Technetium-99 side, we measured both samples of tellurium dioxide produced by SICCAS and doped with Technetium-99 using a mass spectrometer and cryogenic detectors. However, we encountered technical problems due to the segregation of Technetium-99 in the crystal. After several attempts to optimize the procedure, we decided to develop an innovative approach to introduce Technetium-99 into a crystal, activating Technetium-99 from Molybdenum-98 in a natural lithium molybdate crystal.
The ACCESS project significantly enriched the host institution, Queen’s University, by introducing advanced expertise in cryogenic calorimetry and nuclear spectral shape measurements. The researcher contributed to the development of new experimental protocols, introduced novel simulation and data analysis tools, and initiated interdisciplinary collaborations. This two-way transfer of knowledge not only advanced the researcher’s skills but also expanded the scientific capabilities of the host institutions in a new research field.
In the final year, the research activities focused on enhancing cryogenic infrastructure, testing new detector configurations, and continuing spectral shape measurements. Several detector prototypes were installed and tested using NTD sensors. A new mechanical support for the pulse-tube was developed to mitigate vibrational noise. TES readout has been installed, but is still under testing. Transition measurements were performed on superconducting films. Crucial experimental work was conducted on a range of crystals (PbWO4, Li2MoO4, Na2Mo2O7, NaCl, and Li2WO4), including irradiated samples aimed at embedding beta-emitting isotopes (e.g. Tc-99, Cl-36) for direct measurement. Although some of these tests are still ongoing and have faced technical delays, promising preliminary results have been achieved. Monte Carlo simulations were further developed to incorporate new detector designs, thus supporting detector development and data analysis.
The main scientific achievement remains the high-precision measurement of the In-115 beta decay spectrum, which was disseminated in a widely cited PRL publication. The spectral data were shared with theoretical groups and used for model comparison studies published in Phys. Rev. C.
Throughout the three years, ACCESS results were disseminated via presentations at major international conferences (e.g. NEUTRINO, LRT, LTD, TAUP, MEDEX), publications in peer-reviewed journals, and open-access data repositories. Outreach activities included seminars for schools, public events like Pint of Science and SHARPER, and a dedicated website.
The ACCESS project has made significant strides in advancing the state of the art, as evidenced by the following key research outputs:
1) First Measurement of the Indium Oxide Crystal as a Cryogenic Calorimeter
2) Design Study of Indium Iodide Cryogenic Calorimeters
3) Measurement of Indium-115 Decay with Indium Iodine Low-Temperature Calorimeters
Over the last year, significant efforts have been dedicated to pursuing the key objectives of the ACCESS project. While considerable progress has been made, the goals have only been partially achieved. In particular, work on measuring Technetium-99 forbidden beta decay and developing a TES-based low-temperature calorimeter has yielded promising preliminary results; however, further research is needed to achieve the intended outcomes fully.
Given the scientific interest and the encouraging findings obtained so far, these research activities will continue beyond the official end of the ACCESS project, supported by new funding sources.
The project's impact extends beyond the scientific community, encompassing socio-economic and wider societal implications.
The data and findings from this project have already garnered significant interest in the scientific community. The research outputs have been utilized by two separate and independent groups, indicating the high relevance and applicability of the results. This collaboration and data sharing highlight the project's contribution to advancing scientific knowledge and fostering research synergy.
The advancements in cryogenic calorimetry can lead to the development of more sensitive and accurate detection technologies. These technologies have potential applications in various sectors, including nuclear medicine, environmental monitoring, and food safety (Project BeSAFE - Beta Spectroscopy for Agriculture, Food, and Environment). The improved detection capabilities can drive innovation, leading to economic growth and the creation of new job opportunities.
1) First Measurement of the Indium Oxide Crystal as a Cryogenic Calorimeter
2) Design Study of Indium Iodide Cryogenic Calorimeters
3) Measurement of Indium-115 Decay with Indium Iodine Low-Temperature Calorimeters
Over the last year, significant efforts have been dedicated to pursuing the key objectives of the ACCESS project. While considerable progress has been made, the goals have only been partially achieved. In particular, work on measuring Technetium-99 forbidden beta decay and developing a TES-based low-temperature calorimeter has yielded promising preliminary results; however, further research is needed to achieve the intended outcomes fully.
Given the scientific interest and the encouraging findings obtained so far, these research activities will continue beyond the official end of the ACCESS project, supported by new funding sources.
The project's impact extends beyond the scientific community, encompassing socio-economic and wider societal implications.
The data and findings from this project have already garnered significant interest in the scientific community. The research outputs have been utilized by two separate and independent groups, indicating the high relevance and applicability of the results. This collaboration and data sharing highlight the project's contribution to advancing scientific knowledge and fostering research synergy.
The advancements in cryogenic calorimetry can lead to the development of more sensitive and accurate detection technologies. These technologies have potential applications in various sectors, including nuclear medicine, environmental monitoring, and food safety (Project BeSAFE - Beta Spectroscopy for Agriculture, Food, and Environment). The improved detection capabilities can drive innovation, leading to economic growth and the creation of new job opportunities.