Imaging neutron capture cross sections: i-TED proof-of-concept and future prospects based on Machine-Learning techniques

Babiano-Suárez, V., et al.i-TED is an innovative detection system which exploits Compton imaging techniques to achieve a superior signal-to-background ratio in (n, γ) cross-section measurements using time-of-flight technique. This work presents the first experimental validation of the i-TED apparatus for high-resolution time-of-flight experiments and demonstrates for the first time the concept proposed for background rejection. To this aim, the Au(n, γ) and Fe(n, γ) reactions were studied at CERN n_TOF using an i-TED demonstrator based on three position-sensitive detectors. Two CD detectors were also used to benchmark the performance of i-TED. The i-TED prototype built for this study shows a factor of ∼ 3 higher detection sensitivity than state-of-the-art CD detectors in the 10 keV neutron-energy region of astrophysical interest. This paper explores also the perspectives of further enhancement in performance attainable with the final i-TED array consisting of twenty position-sensitive detectors and new analysis methodologies based on Machine-Learning techniques.This work has been carried out in the framework of a project funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (ERC Consolidator Grant project HYMNS, with grant agreement No. 681740). The authors acknowledge support from the Spanish Ministerio de Ciencia e Innovación under grants PID2019-104714GB-C21, FPA2017-83946-C2-1-P, FIS2015-71688-ERC, CSIC for funding PIE-201750I26, and the funding agencies of the participating institutes. We would like to thank the crew at the Electronics Laboratory of IFIC, in particular Manuel Lopez Redondo and Jorge Nácher Arándiga for their excellent and efficient work

Simultaneous neutron and gamma imaging system for real time range and dose monitoring in Hadron Therapy and nuclear security applications

GN-Vision is a novel dual γ-ray and neutron imaging system, which aims at imaging, simultaneously to the prompt gammas, the spatial origin of the slow and thermal neutron dose (<100 eV) generated during hadron therapy treatments. The proposed device can also be of interest for industrial applications as well as in nuclear security. The GN-Vision system has been designed following the technical developments of the iTED detector, an array of high efficiency Compton cameras intended for neutron-capture experiments, in which γ-ray energies span up to 5-6 MeV, similar to the energies encountered in hadron therapy. This manuscript presents the evolution of the i-TED detector towards the GN-Vision system and the first conceptual study of the simultaneous neutron and γ-ray imaging capability. Last, it reviews the status of the development and first results of the promising performance of this device for PG imaging in proton therapy, based on MC simulations

Dispositivo de detección, identificación, cuantificación y/o localización simultánea de fuentes de radiación gamma y de neutrones

Que comprende un colimador mecánico (1) que recibe partículas de una fuente emisora de radiación gamma (61) y/o de neutrones (62), un material absorbente de neutrones y prácticamente transparente a la radiación gamma; un primer detector (2) que comprende un cristal centelleador con capacidad de discriminación neutrón-gamma y un fotosensor sensible a las posiciones, acoplado al colimador mecánico (1); uno o más bloques detectores con cristales centelleadores de radiación gamma o neutrón-gamma (3) y fotosensores sensibles a las posiciones, a continuación del primer detector (2), en una cara opuesta al colimador mecánico (1); y un módulo de adquisición y procesado (4), conectado a los detectores (2, 3), siendo el dispositivo apto para utilizar en inspecciones de seguridad nuclear, seguridad portuaria, amenazas y accidentes nucleares y tratamientos de hadrón-terapia y medicina nuclear. [ES]The invention comprises a mechanical collimator (1) which receives particles from a gamma radiation source (61) and/or a neutron source (62), a neutron-absorbent material that is virtually transparent to gamma radiation; a first detector (2) that comprises a scintillation crystal with neutron-gamma discrimination capability and a position-sensitive photosensor, coupled to the mechanical collimator (1); one or more detector blocks with gamma or neutron-gamma radiation scintillation crystals (3) and position-sensitive photosensors, after the first detector (2), on a face opposite the mechanical collimator (1); and an acquisition and processing module (4) connected to the detectors (2, 3), the device being suitable for use in inspections relating to nuclear safety, port safety, nuclear threats and accidents, and hadron therapy treatments and nuclear medicine. [EN]Peer reviewedConsejo Superior de Investigaciones Científicas (CSIC), Universitat de ValènciaA1 Solicitud de patente con informe sobre el estado de la técnic

Compton Imaging and Machine-Learning techniques for an enhanced sensitivity in key stellar (n,

Neutron capture cross-section measurements are fundamental in the study of astrophysical phenomena, such as the slow neutron capture (s-) process of nucleosynthesis operating in red-giant stars. To enhance the sensitivity of such measurements we have developed the i-TED detector. i-TED is an innovative detection system which exploits the Compton imaging technique with the aim of obtaining information about the incoming direction of the detected γ-rays. The imaging capability allows one to reject a large fraction of the dominant γ-ray background, hence enhancing the (n,γ) detection sensitivity. This work summarizes the main results of the first experimental proof-of-concept of the background rejection with i-TED carried out at CERN n_TOF using an early i-TED demonstrator. Two state-of-the-art C6D6 detectors were also used to benchmark the performance of i-TED. The i-TED prototype built for this study shows a factor of ~3 higher detection sensitivity than C6D6 detectors in the ~10 keV neutron-energy range of astrophysical interest. This works also introduces the perspectives of further enhancement in performance attainable with the final i-TED array and new analysis methodologies based on Machine-Learning techniques. The latter provide higher (n,γ) detection efficiency and similar enhancement in the sensitivity than the analytical method based on the Compton scattering law. Finally, we present our proposal to use this detection system for the first time on key astrophysical (n,γ) measurements, in particular on the s-process branching-point 79Se, which is especially well suited to constrain the thermal conditions of Red Giant and Massive Stars

Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF

This article presents a few selected developments and future ideas related to the measurement of (n, γ) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with γ-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area.European Research Council 681740Ministerio de Ciencia e Innovación PID2019- 104714GBC21, FPA2017-83946-C2-1-P, FIS2015-71688-ERC, FPA2016-77689-C2-1-R, RTI2018-098117-B-C21CSIC PIE201750I26SANDA H2020-84755

New detection systems for an enhanced sensitivity in key stellar (n,γ\gamma) measurements

Neutron capture cross-section measurements are fundamental in the study of astrophysical phenomena, such as the slow neutron capture (s-) process of nucleosynthesis operating in red-giant and massive stars. However, neutron capture measurements via the time-of-flight (TOF) technique on key $s$-process nuclei are often challenging. Difficulties arise from the limited mass ($\sim$mg) available and the high sample-related background in the case of the unstable $s$-process branching points. Measurements on neutron magic nuclei, that act as $s$-process bottlenecks, are affected by low (n,$\gamma$) cross sections and a dominant neutron scattering background. Overcoming these experimental challenges requires the combination of facilities with high instantaneous flux, such as n_TOF-EAR2, with detection systems with an enhanced detection sensitivity and high counting rate capabilities. This contribution reviews some of the latest detector developments in detection systems for (n,$\gamma$) measurements at n_TOF, such as i-TED, an innovative detection system which exploits the Compton imaging technique to reduce the dominant neutron scattering background and s-TED, a highly segmented total energy detector intended for high flux facilities. The discussion will be illustrated with results of the first measurement of key the $s$-process branching-point reaction $^{79}$Se(n,$\gamma$)

Review and new concepts for neutron-capture measurements of astrophysical interest

The idea of slow-neutron capture nucleosynthesis formulated in 1957 triggered a tremendous experimental effort in different laboratories worldwide to measure the relevant nuclear physics input quantities, namely (n, γ) cross sections over the stellar temperature range (from few eV up to several hundred keV) for most of the isotopes involved from Fe up to Bi. A brief historical review focused on total energy detectors will be presented to illustrate how advances in instrumentation have led to the assessment of new aspects of s-process nucleosynthesis and to the progressive refinement of stellar models. A summary will be presented on current efforts to develop new detection concepts, such as the Total-Energy Detector with γ-ray imaging capability (i-TED). The latter is based on the simultaneous combination of Compton imaging with neutron time-of-flight (TOF) techniques, in order to achieve a superior level of sensitivity and selectivity in the measurement of stellar neutron capture rates.Consejo Europeo de Investigación (ERC). Fondo Europeo Programa de investigación e innovación Horizonte 2020 de la Unión Europea nº 681740Ministerio de Ciencia e Innovación de España-FPA2014-52823-C2-1-P y FPA2017-83946-C2-1-PConsejo de Investigaciones Científicas (CSIC)-PIE-201750I2

Imaging neutron capture cross sections: i-TED proof-of-concept and future prospects based on Machine-Learning techniques

International audiencei-TED is an innovative detection system which exploits Compton imaging techniques to achieve a superior signal-to-background ratio in ($n,\gamma$) cross-section measurements using time-of-flight technique. This work presents the first experimental validation of the i-TED apparatus for high-resolution time-of-flight experiments and demonstrates for the first time the concept proposed for background rejection. To this aim, the $^{197}$Au($n,\gamma$) and $^{56}$Fe($n, \gamma$) reactions were studied at CERN n_TOF using an i-TED demonstrator based on three position-sensitive detectors. Two C$_6$D$_6$ detectors were also used to benchmark the performance of i-TED. The i-TED prototype built for this study shows a factor of $\sim$3 higher detection sensitivity than state-of-the-art C$_6$D$_6$ detectors in the 10 keV neutron-energy region of astrophysical interest. This paper explores also the perspectives of further enhancement in performance attainable with the final i-TED array consisting of twenty position-sensitive detectors and new analysis methodologies based on Machine-Learning techniques

Study of photon strength functions of 241Pu and 245Cm from neutron capture measurements

We have measured the γ-rays following neutron capture on 240Pu and 244 Cm at the n_TOF facility at CERN with the Total Absorption Calorimeter (TAC) and with C6D6 organic scintillators. The TAC is made of 40 BaF2 crystals operating in coincidence and covering almost the entire solid angle. This allows to obtain information concerning the energy spectra and the multiplicity of the measured capture γ-ray cascades. Additional information is also obtained from the C6D6 detectors. We have analyzed the measured data in order to draw conclusions about the Photon Strength Functions (PSFs) of 241Pu and 245Cm below their neutron separation energies. The analysis has been performed by fitting the PSFs to the experimental results, using the differential evolution method, in order to find neutron capture cascades capable of reproducing at the same time a great variety of deposited energy spectra

Measurement of the 244Cm capture cross sections at both CERN n_TOF experimental areas

Accurate neutron capture cross section data for minor actinides (MAs) are required to estimate the production and transmutation rates of MAs in light water reactors with a high burnup, critical fast reactors like Gen-IV systems and other innovative reactor systems such as accelerator driven systems (ADS). Capture reactions of 244Cm open the path for the formation of heavier Cm isotopes and of heavier elements such as Bk and Cf. In addition, 244Cm shares nearly 50% of the total actinide decay heat in irradiated reactor fuels with a high burnup, even after three years of cooling. Experimental data for this isotope are very scarce due to the difficulties of providing isotopically enriched samples and because the high intrinsic activity of the samples requires the use of neutron facilities with high instantaneous flux. The only two previous experimental data sets for this neutron capture cross section have been obtained in 1969 using a nuclear explosion and, more recently, at J-PARC in 2010. The neutron capture cross sections have been measured at n_TOF with the same samples that the previous experiments in J-PARC. The samples were measured at n_TOF Experimental Area 2 (EAR-2) with three C6D6 detectors and also in Experimental Area 1 (EAR-1) with the Total Absorption Calorimeter (TAC). Preliminary results assessing the quality and limitations of these new experimental datasets are presented for the experiments in both areas. Preliminary yields of both measurements will be compared with evaluated libraries for the first time