Pub Date : 2025-12-31DOI: 10.1016/j.nima.2025.171251
D. Ramos , X. Ledoux , L. Audouin , G. Fremont , P. Gangnant , J.C. Foy , C. Le Naour , M. Maloubier
A new experimental setup has been installed at the Time-Of-Flight area of the Neutrons For Science facility (NFS) at GANIL/SPIRAL2 for neutron beam monitoring. This setup consists of an array of Position-Sensitive Parallel-Plate Avalanche Counters (PS-PPACs) that detects both fission fragments in coincidence from secondary neutron-induced fission reactions in several U targets. The neutron energy is determined on an event-by-event basis using the Time-of-Flight method, and the reaction point within the U targets is reconstructed, enabling the measurement of the neutron beam flux and beam profile. The high transparency of the setup allows it to operate in parallel with other experiments running at NFS, thus providing an in-beam monitor of the neutron intensity. In this work, we report on the characteristics of this new setup, its operating principle, and the first results obtained using the high-intensity white-spectrum neutron beam at NFS. This beam is produced via reactions between a primary 40-MeV deuteron beam, accelerated in the SPIRAL2 LINAC, and a 8 mm-thick rotating beryllium converter target.
{"title":"A new beam monitor at NFS/SPIRAL2 based on position-sensitive PPACs detecting fission fragments from 238U(n,f)","authors":"D. Ramos , X. Ledoux , L. Audouin , G. Fremont , P. Gangnant , J.C. Foy , C. Le Naour , M. Maloubier","doi":"10.1016/j.nima.2025.171251","DOIUrl":"10.1016/j.nima.2025.171251","url":null,"abstract":"<div><div>A new experimental setup has been installed at the Time-Of-Flight area of the Neutrons For Science facility (NFS) at GANIL/SPIRAL2 for neutron beam monitoring. This setup consists of an array of Position-Sensitive Parallel-Plate Avalanche Counters (PS-PPACs) that detects both fission fragments in coincidence from secondary neutron-induced fission reactions in several <span><math><msup><mrow></mrow><mrow><mn>238</mn></mrow></msup></math></span>U targets. The neutron energy is determined on an event-by-event basis using the Time-of-Flight method, and the reaction point within the U targets is reconstructed, enabling the measurement of the neutron beam flux and beam profile. The high transparency of the setup allows it to operate in parallel with other experiments running at NFS, thus providing an in-beam monitor of the neutron intensity. In this work, we report on the characteristics of this new setup, its operating principle, and the first results obtained using the high-intensity white-spectrum neutron beam at NFS. This beam is produced via reactions between a primary 40-MeV deuteron beam, accelerated in the SPIRAL2 LINAC, and a 8 mm-thick rotating beryllium converter target.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171251"},"PeriodicalIF":1.4,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-31DOI: 10.1016/j.nima.2025.171256
Fengbo Gu , Junhui Liao , Jiangfeng Zhou , Meiyuanan Ma , Zhuo Liang , Guangpeng An , Zhaohua Peng , Jian Zheng , Lifeng Zhang , Lei Zhang , Yuanning Gao , Fabio Acerbi , Andrea Ficorella , Alberto Gola , Laura Parellada Monreal
Five FBK “NUV-HD-Cryo” SiPMs have been characterized at 7 K and 10 K, with 405 nm and 530 nm LED light, respectively. The dark count rate (DCR) was measured to be 1 Hz for the 100 mm-size SiPMs, or 0.01 Hz/mm, which is 7 orders lower than the DCR at room temperature (RT). Given the very low DCR at these cryogenic temperatures, we measured the SiPMs’ I–V curves with such a method: illuminated the SiPMs with weak light, which differs from the conventional measurements at RT. Then, we measured the photo-detection efficiency (PDE), after-pulse (AP), and cross-talk probabilities (CT) with a bias voltage ranging from overvoltage (OV) 5 to 11 V. At the OV interval (5 to 11 V), the PDE was between 20%–45%, and the AP and CT were both between 5% and 20%. With an OV higher than 10 V, the PDE would be 40%, and the AP and CT are 20%. Combining all of the measurements, we are confident that the SiPMs can be equipped as the photosensors on liquid helium detectors, including but not limited to the time projection chambers, which we have proposed in hunting for low-mass dark matter directly and beyond.
{"title":"Characterization of FBK NUV-HD-Cryo SiPMs near LHe temperature","authors":"Fengbo Gu , Junhui Liao , Jiangfeng Zhou , Meiyuanan Ma , Zhuo Liang , Guangpeng An , Zhaohua Peng , Jian Zheng , Lifeng Zhang , Lei Zhang , Yuanning Gao , Fabio Acerbi , Andrea Ficorella , Alberto Gola , Laura Parellada Monreal","doi":"10.1016/j.nima.2025.171256","DOIUrl":"10.1016/j.nima.2025.171256","url":null,"abstract":"<div><div>Five FBK “NUV-HD-Cryo” SiPMs have been characterized at 7 K and 10 K, with 405 nm and 530 nm LED light, respectively. The dark count rate (DCR) was measured to be <span><math><mo>∼</mo></math></span>1 Hz for the <span><math><mo>∼</mo></math></span>100 mm<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>-size SiPMs, or 0.01 Hz/mm<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>, which is <span><math><mo>∼</mo></math></span>7 orders lower than the DCR at room temperature (RT). Given the very low DCR at these cryogenic temperatures, we measured the SiPMs’ I–V curves with such a method: illuminated the SiPMs with weak light, which differs from the conventional measurements at RT. Then, we measured the photo-detection efficiency (PDE), after-pulse (AP), and cross-talk probabilities (CT) with a bias voltage ranging from overvoltage (OV) 5 to 11 V. At the OV interval (5 to 11 V), the PDE was between 20%–45%, and the AP and CT were both between <span><math><mo>∼</mo></math></span>5% and <span><math><mo>∼</mo></math></span>20%. With an OV higher than 10 V, the PDE would be <span><math><mo>≥</mo></math></span> 40%, and the AP and CT are <span><math><mo>∼</mo></math></span>20%. Combining all of the measurements, we are confident that the SiPMs can be equipped as the photosensors on liquid helium detectors, including but not limited to the time projection chambers, which we have proposed in hunting for low-mass dark matter directly and beyond.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171256"},"PeriodicalIF":1.4,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-30DOI: 10.1016/j.nima.2025.171264
Pengfei Zhou , Zhirong Zeng , Zheng He , Xiao Wang , Li Lin , Ming Tang , Arsen Goukassov , Fangwei Wang , Tianjiao Liang , Erxi Feng
Designing neutron guide systems for single-crystal time-of-flight spectrometers requires balancing neutron flux, divergence, and compatibility with polarization optics. We present an automated optimization framework that integrates Monte Carlo simulations, Bayesian optimization, and a back-tracing method to systematically explore guide geometries under realistic engineering constraints. Applied to the Elastic Diffuse Spectrometer at the China Spallation Neutron Source, the framework evaluated four candidate designs to maximize flux while meeting divergence limits imposed by polarization and resolution requirements. Among the Bayesian-optimized configurations, the straight–elliptic guide offered the best overall balance of flux, divergence, and polarization performance.
{"title":"Bayesian optimization of combined ballistic neutron guides for the Elastic Diffuse Scattering spectrometer at CSNS","authors":"Pengfei Zhou , Zhirong Zeng , Zheng He , Xiao Wang , Li Lin , Ming Tang , Arsen Goukassov , Fangwei Wang , Tianjiao Liang , Erxi Feng","doi":"10.1016/j.nima.2025.171264","DOIUrl":"10.1016/j.nima.2025.171264","url":null,"abstract":"<div><div>Designing neutron guide systems for single-crystal time-of-flight spectrometers requires balancing neutron flux, divergence, and compatibility with polarization optics. We present an automated optimization framework that integrates Monte Carlo simulations, Bayesian optimization, and a back-tracing method to systematically explore guide geometries under realistic engineering constraints. Applied to the Elastic Diffuse Spectrometer at the China Spallation Neutron Source, the framework evaluated four candidate designs to maximize flux while meeting divergence limits imposed by polarization and resolution requirements. Among the Bayesian-optimized configurations, the straight–elliptic guide offered the best overall balance of flux, divergence, and polarization performance.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171264"},"PeriodicalIF":1.4,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Measurements have been made of the decay heat generated within the new-style tantalum-clad ten-plate tungsten target for the First Target Station (TS-1) of the ISIS Spallation Neutron Source. The new-style target incorporates less tantalum than the old-style target, and the decay heat is correspondingly less. Measured values of decay heat agree well with values obtained from Monte Carlo calculations.
{"title":"Measurement of decay heat in ISIS new-style TS-1 target","authors":"D.J.S. Findlay, G.P. Škoro, J.P. Chapman, J.D. Moor, S.D. Gallimore","doi":"10.1016/j.nima.2025.171263","DOIUrl":"10.1016/j.nima.2025.171263","url":null,"abstract":"<div><div>Measurements have been made of the decay heat generated within the new-style tantalum-clad ten-plate tungsten target for the First Target Station (TS-1) of the ISIS Spallation Neutron Source. The new-style target incorporates less tantalum than the old-style target, and the decay heat is correspondingly less. Measured values of decay heat agree well with values obtained from Monte Carlo calculations.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1085 ","pages":"Article 171263"},"PeriodicalIF":1.4,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-30DOI: 10.1016/j.nima.2025.171259
S. Terui , T. Ishibashi , M. Shirai , X. Jin , M. Yao , K. Shibata , T. Abe , N. Akita , A. Natochii , Q. Liu
Currently, SuperKEKB faces the challenge of sudden beam loss (SBL), which occurs with almost no prior warning, and the causes of SBL are not yet fully understood. A damaged collimator has a reduced ability to suppress beam background noise (BG) compared to an undamaged collimator. When BG suppression decreases, operation must be stopped and the collimator jaw replaced. Therefore, a robust collimator head material is required. In this study, we investigated the material properties of copper-carbide graphite (CuGr) as a candidate collimator head material for SuperKEKB and future electron/positron colliders in terms of its electrical conductivity in the high-frequency region, secondary electron yield, outgassing rate owing to photon-stimulated desorption, and amount of dust generated by the ultrasonic cleaning of CuGr. The results were compared with the simulation results of the beam background with CuGr. According to the study findings, CuGr can be effectively used as the collimator head material. Its use in SuperKEKB and future ring colliders is expected to contribute to stable accelerator operation.
{"title":"Investigation of new collimator head material candidates for SuperKEKB and future electron/positron colliders","authors":"S. Terui , T. Ishibashi , M. Shirai , X. Jin , M. Yao , K. Shibata , T. Abe , N. Akita , A. Natochii , Q. Liu","doi":"10.1016/j.nima.2025.171259","DOIUrl":"10.1016/j.nima.2025.171259","url":null,"abstract":"<div><div>Currently, SuperKEKB faces the challenge of sudden beam loss (SBL), which occurs with almost no prior warning, and the causes of SBL are not yet fully understood. A damaged collimator has a reduced ability to suppress beam background noise (BG) compared to an undamaged collimator. When BG suppression decreases, operation must be stopped and the collimator jaw replaced. Therefore, a robust collimator head material is required. In this study, we investigated the material properties of copper-carbide graphite (CuGr) as a candidate collimator head material for SuperKEKB and future electron/positron colliders in terms of its electrical conductivity in the high-frequency region, secondary electron yield, outgassing rate owing to photon-stimulated desorption, and amount of dust generated by the ultrasonic cleaning of CuGr. The results were compared with the simulation results of the beam background with CuGr. According to the study findings, CuGr can be effectively used as the collimator head material. Its use in SuperKEKB and future ring colliders is expected to contribute to stable accelerator operation.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171259"},"PeriodicalIF":1.4,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a statistical method for detecting and analysing state changes in experimental measurements using the Cuscore statistic and its special case, the Centred Cuscore statistic. These statistics are designed to identify deviations in detector responses using sequential hypothesis testing relative to a defined reference state. Applications to charge-changing reaction experiments at the FRagment Separator facility at the GSI Helmholtz Centre for Heavy Ion Research, Germany, and the Second Radioactive Ion Beam Line in Lanzhou at the Institute of Modern Physics, China, demonstrate the ability of these tools to quantify state changes, identify the change point, and classify data segments based on measured states. For long-term online monitoring, we use the exponentially weighted moving average to continuously update computations, enabling the detection of successive changes. This method supports both real-time and post-experiment diagnostics and provides a robust approach for enhancing data integrity and experimental control in nuclear physics and related fields.
{"title":"Identification and online monitoring of experimental measurement states via Cuscore statistic","authors":"Jichao Zhang , Baohua Sun , Isao Tanihata , Zilun Shen","doi":"10.1016/j.nima.2025.171267","DOIUrl":"10.1016/j.nima.2025.171267","url":null,"abstract":"<div><div>We present a statistical method for detecting and analysing state changes in experimental measurements using the Cuscore statistic and its special case, the Centred Cuscore statistic. These statistics are designed to identify deviations in detector responses using sequential hypothesis testing relative to a defined reference state. Applications to charge-changing reaction experiments at the FRagment Separator facility at the GSI Helmholtz Centre for Heavy Ion Research, Germany, and the Second Radioactive Ion Beam Line in Lanzhou at the Institute of Modern Physics, China, demonstrate the ability of these tools to quantify state changes, identify the change point, and classify data segments based on measured states. For long-term online monitoring, we use the exponentially weighted moving average to continuously update computations, enabling the detection of successive changes. This method supports both real-time and post-experiment diagnostics and provides a robust approach for enhancing data integrity and experimental control in nuclear physics and related fields.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171267"},"PeriodicalIF":1.4,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-29DOI: 10.1016/j.nima.2025.171266
Eric Laloy, Md Moudud Hasan, Bart Rogiers, Wouter Broeckx, Arne Vandenbrande, An Bielen
This work introduces a novel Bayesian approach for interpreting total gamma clearance monitoring data. The approach integrates spatial and spectral information from the measurements with a surrogate efficiency model, all within a Bayesian inference framework, to estimate the spatial activity distribution across 15 subvolumes inside a 200-liter waste drum. When the / ratio is not known a priori, it can be jointly estimated alongside other variables of interest. Virtual and real mock-up experiments demonstrate that the method accurately identifies high-activity subvolumes and reconstructs the relative spatial activity distribution. Moreover, with reliable background count estimates, the total drum activity can be determined with a relative error below 10%. Tests on two real low-level waste drums, validated against HPGe-based gamma spectrometry, confirm a maximum relative error of 10%. Regarding inference of the / ratio, the approach correctly detects drums containing only but underestimates the fraction when is present. Our proposed approach has also some practical limitations, mainly its reliance on prior knowledge of the drum’s filling level being close to 100% and, to a lesser extent, its underlying assumption of a constant density across the drum. Future work will aim to solve that issue by incorporating filling degree into the surrogate efficiency model.
{"title":"Bayesian inference for total gamma clearance monitors: Accounting for both spatial and spectral information","authors":"Eric Laloy, Md Moudud Hasan, Bart Rogiers, Wouter Broeckx, Arne Vandenbrande, An Bielen","doi":"10.1016/j.nima.2025.171266","DOIUrl":"10.1016/j.nima.2025.171266","url":null,"abstract":"<div><div>This work introduces a novel Bayesian approach for interpreting total gamma clearance monitoring data. The approach integrates spatial and spectral information from the measurements with a surrogate efficiency model, all within a Bayesian inference framework, to estimate the spatial activity distribution across 15 subvolumes inside a 200-liter waste drum. When the <span><math><mrow><msup><mrow></mrow><mrow><mi>60</mi></mrow></msup><mtext>Co</mtext></mrow></math></span>/<span><math><mrow><msup><mrow></mrow><mrow><mi>137</mi></mrow></msup><mtext>Cs</mtext></mrow></math></span> ratio is not known a priori, it can be jointly estimated alongside other variables of interest. Virtual and real mock-up experiments demonstrate that the method accurately identifies high-activity subvolumes and reconstructs the relative spatial activity distribution. Moreover, with reliable background count estimates, the total drum activity can be determined with a relative error below 10%. Tests on two real low-level waste drums, validated against HPGe-based gamma spectrometry, confirm a maximum relative error of 10%. Regarding inference of the <span><math><mrow><msup><mrow></mrow><mrow><mi>60</mi></mrow></msup><mtext>Co</mtext></mrow></math></span>/<span><math><mrow><msup><mrow></mrow><mrow><mi>137</mi></mrow></msup><mtext>Cs</mtext></mrow></math></span> ratio, the approach correctly detects drums containing only <span><math><mrow><msup><mrow></mrow><mrow><mi>137</mi></mrow></msup><mtext>Cs</mtext></mrow></math></span> but underestimates the <span><math><mrow><msup><mrow></mrow><mrow><mi>60</mi></mrow></msup><mtext>Co</mtext></mrow></math></span> fraction when <span><math><mrow><msup><mrow></mrow><mrow><mi>60</mi></mrow></msup><mtext>Co</mtext></mrow></math></span> is present. Our proposed approach has also some practical limitations, mainly its reliance on prior knowledge of the drum’s filling level being close to 100% and, to a lesser extent, its underlying assumption of a constant density across the drum. Future work will aim to solve that issue by incorporating filling degree into the surrogate efficiency model.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171266"},"PeriodicalIF":1.4,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145924696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-27DOI: 10.1016/j.nima.2025.171261
Ippei Yamada, Kunihiro Kojima, Motoki Chimura
A non-invasive beam profile monitor is indispensable for stable operation of a high-intensity particle accelerator. Two types based on beam-gas interaction have been developed at many institutes: the residual gas type and the gas injection type. The gas injection method enables a high-speed or accurate profile measurements due to the high secondary particle yield, in contrast to the residual gas type. However, gas injection may affect the beam quality, and a quantitative evaluation of non-invasiveness is essential. Charge exchange and phase-space distribution change of a negative hydrogen ion (H) beam induced by beam-gas interaction were quantified. The charge exchange was assessed through measurement of the beam current reduction, and the beam loss linearly increased with the injected gas flux, as consistent with the charge-exchange cross-section within a possible error range. Phase-space distributions with and without gas injection were measured, and the emittance reduced by about 5%, rather than increased due to scattering, when the beam line pressure was raised from 10−6 Pa to 10−3 Pa. An analytical approach and a particle-in-cell simulation revealed that the mitigation of the H beam’s space charge by ions generated in the beam-gas interaction induced the emittance reduction: a space-charge neutralization/compensation effect. In addition to the emittance reduction, the beam envelope exhibited a non-negligible lens effect due to the neutralization, and we devised a correction term including no arbitrariness under steady state of the neutralization.
{"title":"Non-invasiveness evaluation of gas-sheet beam profile monitor: Observation of emittance reduction due to space-charge neutralization","authors":"Ippei Yamada, Kunihiro Kojima, Motoki Chimura","doi":"10.1016/j.nima.2025.171261","DOIUrl":"10.1016/j.nima.2025.171261","url":null,"abstract":"<div><div>A non-invasive beam profile monitor is indispensable for stable operation of a high-intensity particle accelerator. Two types based on beam-gas interaction have been developed at many institutes: the residual gas type and the gas injection type. The gas injection method enables a high-speed or accurate profile measurements due to the high secondary particle yield, in contrast to the residual gas type. However, gas injection may affect the beam quality, and a quantitative evaluation of non-invasiveness is essential. Charge exchange and phase-space distribution change of a negative hydrogen ion (H<span><math><msup><mrow></mrow><mrow><mo>−</mo></mrow></msup></math></span>) beam induced by beam-gas interaction were quantified. The charge exchange was assessed through measurement of the beam current reduction, and the beam loss linearly increased with the injected gas flux, as consistent with the charge-exchange cross-section within a possible error range. Phase-space distributions with and without gas injection were measured, and the emittance reduced by about 5%, rather than increased due to scattering, when the beam line pressure was raised from 10<sup>−6</sup> Pa to 10<sup>−3</sup> Pa. An analytical approach and a particle-in-cell simulation revealed that the mitigation of the H<span><math><msup><mrow></mrow><mrow><mo>−</mo></mrow></msup></math></span> beam’s space charge by ions generated in the beam-gas interaction induced the emittance reduction: a space-charge neutralization/compensation effect. In addition to the emittance reduction, the beam envelope exhibited a non-negligible lens effect due to the neutralization, and we devised a correction term including no arbitrariness under steady state of the neutralization.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171261"},"PeriodicalIF":1.4,"publicationDate":"2025-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-27DOI: 10.1016/j.nima.2025.171262
L. Gioacchini , A. Lega , R. Nicolaidis , F. Nozzoli
<div><div>Lutetium–yttrium oxyorthosilicate (LYSO) crystals are widely recognized as fast scintillators, valued for their high light output and robust mechanical properties, which make them well suited for high-energy physics and space applications despite their intrinsic radioactivity. Although the non-proportional light response of LYSO scintillators has been extensively studied, discrepancies remain among published measurements of the light-yield quenching at high ionization densities with different charged particles. We report a measurement of the light response of a LYSO scintillator to stopping <span><math><mi>α</mi></math></span> particles emitted by a <sup>241</sup>Am source performed in the laboratories of the University of Trento. A quenching factor, L/E <span><math><mo>=</mo></math></span> 0.075<span><math><mrow><mspace></mspace><mo>±</mo><mspace></mspace><mn>0</mn><mo>.</mo><mn>006</mn></mrow></math></span>, for <span><math><mrow><mn>3</mn><mo>.</mo><mn>7</mn><mspace></mspace><mspace></mspace><mi>MeV</mi></mrow></math></span> <span><math><mi>α</mi></math></span> particles has been inferred, in agreement with previous results obtained with He ions.</div><div>The time distribution of the scintillation decay has also been investigated, confirming the presence of two exponential components in the decay tail: <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mtext>fast</mtext></mrow></msub><mo>=</mo><mn>23</mn><mo>.</mo><mn>3</mn><mspace></mspace><mo>±</mo><mspace></mspace><mn>0</mn><mo>.</mo><msup><mrow><mn>7</mn></mrow><mrow><mrow><mo>(</mo><mtext>stat.</mtext><mo>)</mo></mrow></mrow></msup><mo>±</mo><mn>0</mn><mo>.</mo><msup><mrow><mn>8</mn></mrow><mrow><mrow><mo>(</mo><mtext>syst.</mtext><mo>)</mo></mrow></mrow></msup><mspace></mspace><mspace></mspace><mi>ns</mi></mrow></math></span> and <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mtext>slow</mtext></mrow></msub><mo>=</mo><mn>43</mn><mo>.</mo><mn>9</mn><mspace></mspace><mo>±</mo><mspace></mspace><mn>0</mn><mo>.</mo><msup><mrow><mn>5</mn></mrow><mrow><mrow><mo>(</mo><mtext>stat.</mtext><mo>)</mo></mrow></mrow></msup><mspace></mspace><mo>±</mo><mspace></mspace><mn>2</mn><mo>.</mo><msup><mrow><mn>3</mn></mrow><mrow><mrow><mo>(</mo><mtext>syst.</mtext><mo>)</mo></mrow></mrow></msup><mspace></mspace><mspace></mspace><mi>ns</mi></mrow></math></span>. The current measurement revealed that <span><math><mi>α</mi></math></span> scintillation pulses are faster than <span><math><mrow><mi>β</mi><mo>/</mo><mi>γ</mi></mrow></math></span> ones. This behavior is quantitatively parameterized by a difference in the amplitude of the two scintillation components: <span><math><mrow><msubsup><mrow><mi>A</mi></mrow><mrow><mtext>slow</mtext></mrow><mrow><mi>α</mi></mrow></msubsup><mo>=</mo><mrow><mo>(</mo><mn>48</mn><mo>.</mo><mn>7</mn><mspace></mspace><mo>±</mo><mspace></mspace><mn>3</mn><mo>.</mo><msup><mrow><mn>3</mn></mrow><mrow><mrow><mo>(</mo><mtext>stat.</mtext><mo>)</mo></mrow></mrow></ms
{"title":"Characterization of the light response of LYSO scintillator to α particles","authors":"L. Gioacchini , A. Lega , R. Nicolaidis , F. Nozzoli","doi":"10.1016/j.nima.2025.171262","DOIUrl":"10.1016/j.nima.2025.171262","url":null,"abstract":"<div><div>Lutetium–yttrium oxyorthosilicate (LYSO) crystals are widely recognized as fast scintillators, valued for their high light output and robust mechanical properties, which make them well suited for high-energy physics and space applications despite their intrinsic radioactivity. Although the non-proportional light response of LYSO scintillators has been extensively studied, discrepancies remain among published measurements of the light-yield quenching at high ionization densities with different charged particles. We report a measurement of the light response of a LYSO scintillator to stopping <span><math><mi>α</mi></math></span> particles emitted by a <sup>241</sup>Am source performed in the laboratories of the University of Trento. A quenching factor, L/E <span><math><mo>=</mo></math></span> 0.075<span><math><mrow><mspace></mspace><mo>±</mo><mspace></mspace><mn>0</mn><mo>.</mo><mn>006</mn></mrow></math></span>, for <span><math><mrow><mn>3</mn><mo>.</mo><mn>7</mn><mspace></mspace><mspace></mspace><mi>MeV</mi></mrow></math></span> <span><math><mi>α</mi></math></span> particles has been inferred, in agreement with previous results obtained with He ions.</div><div>The time distribution of the scintillation decay has also been investigated, confirming the presence of two exponential components in the decay tail: <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mtext>fast</mtext></mrow></msub><mo>=</mo><mn>23</mn><mo>.</mo><mn>3</mn><mspace></mspace><mo>±</mo><mspace></mspace><mn>0</mn><mo>.</mo><msup><mrow><mn>7</mn></mrow><mrow><mrow><mo>(</mo><mtext>stat.</mtext><mo>)</mo></mrow></mrow></msup><mo>±</mo><mn>0</mn><mo>.</mo><msup><mrow><mn>8</mn></mrow><mrow><mrow><mo>(</mo><mtext>syst.</mtext><mo>)</mo></mrow></mrow></msup><mspace></mspace><mspace></mspace><mi>ns</mi></mrow></math></span> and <span><math><mrow><msub><mrow><mi>τ</mi></mrow><mrow><mtext>slow</mtext></mrow></msub><mo>=</mo><mn>43</mn><mo>.</mo><mn>9</mn><mspace></mspace><mo>±</mo><mspace></mspace><mn>0</mn><mo>.</mo><msup><mrow><mn>5</mn></mrow><mrow><mrow><mo>(</mo><mtext>stat.</mtext><mo>)</mo></mrow></mrow></msup><mspace></mspace><mo>±</mo><mspace></mspace><mn>2</mn><mo>.</mo><msup><mrow><mn>3</mn></mrow><mrow><mrow><mo>(</mo><mtext>syst.</mtext><mo>)</mo></mrow></mrow></msup><mspace></mspace><mspace></mspace><mi>ns</mi></mrow></math></span>. The current measurement revealed that <span><math><mi>α</mi></math></span> scintillation pulses are faster than <span><math><mrow><mi>β</mi><mo>/</mo><mi>γ</mi></mrow></math></span> ones. This behavior is quantitatively parameterized by a difference in the amplitude of the two scintillation components: <span><math><mrow><msubsup><mrow><mi>A</mi></mrow><mrow><mtext>slow</mtext></mrow><mrow><mi>α</mi></mrow></msubsup><mo>=</mo><mrow><mo>(</mo><mn>48</mn><mo>.</mo><mn>7</mn><mspace></mspace><mo>±</mo><mspace></mspace><mn>3</mn><mo>.</mo><msup><mrow><mn>3</mn></mrow><mrow><mrow><mo>(</mo><mtext>stat.</mtext><mo>)</mo></mrow></mrow></ms","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1084 ","pages":"Article 171262"},"PeriodicalIF":1.4,"publicationDate":"2025-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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