D. Reggiani, B. Blau, R. Dölling, P. Duperrex, D. Kiselev, V. Talanov, J. Welte, M. Wohlmuther
With a nominal beam power of nearly 1.4 MW, the PSI High Intensity Proton Accelerator (HIPA) is currently at the forefront of the high intensity frontier of particle accelerators. Key issues of this facility are minimization of beam losses as well as safe operation of the SINQ spallation source. Particular attention is being recently paid towards an improved understanding of the properties of the SINQ beam line by both enhancing the beam transport simulations and developing new diagnostic elements which can also, in some cases, preserve the target integrity by preventing too large beam current density, inaccurate beam steering or improper beam delivery. Moreover, part of the SINQ beam diagnostic concept is being rethought in order to include important missing devices like BPMs. On the simulation side, newly developed composite calculations involving general purpose particle transport programs like MCNPX and BDSIM will deliver insights about beam losses and transmission through collimators. All recent and planned developments of the SINQ beam line will be discussed in this contribution.
{"title":"Improving beam simulations as well as machine and target protection in the SINQ beam line at PSI-HIPA","authors":"D. Reggiani, B. Blau, R. Dölling, P. Duperrex, D. Kiselev, V. Talanov, J. Welte, M. Wohlmuther","doi":"10.3233/jnr-200162","DOIUrl":"https://doi.org/10.3233/jnr-200162","url":null,"abstract":"With a nominal beam power of nearly 1.4 MW, the PSI High Intensity Proton Accelerator (HIPA) is currently at the forefront of the high intensity frontier of particle accelerators. Key issues of this facility are minimization of beam losses as well as safe operation of the SINQ spallation source. Particular attention is being recently paid towards an improved understanding of the properties of the SINQ beam line by both enhancing the beam transport simulations and developing new diagnostic elements which can also, in some cases, preserve the target integrity by preventing too large beam current density, inaccurate beam steering or improper beam delivery. Moreover, part of the SINQ beam diagnostic concept is being rethought in order to include important missing devices like BPMs. On the simulation side, newly developed composite calculations involving general purpose particle transport programs like MCNPX and BDSIM will deliver insights about beam losses and transmission through collimators. All recent and planned developments of the SINQ beam line will be discussed in this contribution.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/jnr-200162","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46576818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Capogni, M. Capone, A. Pietropaolo, A. Fazio, G. Dellepiane, R. Falconi, A. Colangeli, S. Palomba, G. Valentini, M. Fantuzi, R. Faccini, A. Pizzuto
64Cu is an emerging radionuclide of great interest in personalized nuclear medicine. It is produced by a cyclotron via the reaction 64Ni(p,n)64Cu. This production method increased during the last decades, because small biomedical cyclotrons can be easily installed close to the nuclear medicine department of a hospital. As a matter of fact, 64Ni is a very expensive target material. For this reason, an alternative 64Cu production method was investigated at ENEA by using the quasi-monochromatic 14 MeV fusion neutron beam made available at the Frascati Neutron Generator (FNG) located at the ENEA – Frascati Research Center. In particular, two nuclear reactions were studied: 65Cu(n,2n)64Cu and 64Zn(n,p)64Cu. The radiochemical analysis of the activated samples was performed at the ENEA-NMLNWM laboratory located in ENEA-Casaccia Research Center. The activity measurements were carried out at the ENEA-INMRI, located in the ENEA-Casaccia Research Center, with high metrological level conditions and by assuring their traceability to the 64Cu primary activity standard here developed and maintained. A prediction of the 64Cu production by means of the high-brilliance 14 MeV neutron source named Sorgentina is also discussed.
{"title":"64Cu production by 14 MeV neutron beam","authors":"M. Capogni, M. Capone, A. Pietropaolo, A. Fazio, G. Dellepiane, R. Falconi, A. Colangeli, S. Palomba, G. Valentini, M. Fantuzi, R. Faccini, A. Pizzuto","doi":"10.3233/jnr-190140","DOIUrl":"https://doi.org/10.3233/jnr-190140","url":null,"abstract":"64Cu is an emerging radionuclide of great interest in personalized nuclear medicine. It is produced by a cyclotron via the reaction 64Ni(p,n)64Cu. This production method increased during the last decades, because small biomedical cyclotrons can be easily installed close to the nuclear medicine department of a hospital. As a matter of fact, 64Ni is a very expensive target material. For this reason, an alternative 64Cu production method was investigated at ENEA by using the quasi-monochromatic 14 MeV fusion neutron beam made available at the Frascati Neutron Generator (FNG) located at the ENEA – Frascati Research Center. In particular, two nuclear reactions were studied: 65Cu(n,2n)64Cu and 64Zn(n,p)64Cu. The radiochemical analysis of the activated samples was performed at the ENEA-NMLNWM laboratory located in ENEA-Casaccia Research Center. The activity measurements were carried out at the ENEA-INMRI, located in the ENEA-Casaccia Research Center, with high metrological level conditions and by assuring their traceability to the 64Cu primary activity standard here developed and maintained. A prediction of the 64Cu production by means of the high-brilliance 14 MeV neutron source named Sorgentina is also discussed.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":"1 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/jnr-190140","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41432310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Lacy, A. Athanasiades, Christopher S. Martin, Richard Nguyen, Stephen Davenport, T. Lyons, Yangwei Liu
Modified boron-coated straw (BCS) detector configurations are introduced, in order to improve detection efficiency, and reduce the number of layers required to match the response of high-pressure 3He tubes, in large-scale neutron science instruments. A new 7-straw design employing thin-walled aluminum tubes facilitates operation in vacuum, and substantially reduces the scattering material by a factor of 5 compared with the flow-through design of the Multi-Grid detector. Another design introduces 18 radial walls inside each straw, coated on both sides with enriched boron carbide, to increase the coated wall perimeter 4.3 times. The so-called Pie straw offers a significant benefit in detection efficiency compared with round straws used in LoKI. An example of such a straw having 18 septa is explored in modeling and experimental studies, that can potentially reduce the number of layers needed in large-scale instruments like LoKI by a factor of 2.8. In a parallel development, a totally new configuration of boron-coated detectors is introduced, aimed to address the need for high spatial resolution, and high-rate capability in single crystal diffractometers, like MaNDi and TOPAZ at the SNS, and in neutron reflectometers. The proposed structure is a close-packed array of rectangular cells, each fabricated by wrapping copper foil having a coating of 10B4C on one side and electroplated tin on the other side, around precisely machined rectangular bars. The array is pressed together and then vacuum brazed together. The resulting structure is quite strong and precise in geometry. This so-called Microcell Straw Array can be configured with channel dimensions as small as 0.5 mm × 2.5 mm. Due to its ultra thin walls (25 μm) secondary scattering of neutrons is minimized. It is sealed inside a fully welded thin aluminum containment vessel that allows convenient operation in vacuum. A mature low power readout system capable of an estimated count rate of 22 MHz in a 15 × 15 cm2 detector is also proposed. The improvements are the result of recent advances in BCS design, spurred by the development of compact, high-sensitivity monitors for homeland security and military applications.
为了在大型中子科学仪器中提高检测效率，减少与高压3He管响应相匹配所需的层数，介绍了改进的硼包覆吸管(BCS)探测器配置。采用薄壁铝管的新型7吸管设计便于在真空中操作，与Multi-Grid检测器的流动设计相比，散射材料大大减少了5倍。另一种设计在每根稻草内部引入18个径向壁，两面涂有富集的碳化硼，使涂覆壁周长增加4.3倍。与LoKI中使用的圆形吸管相比，所谓的Pie吸管在检测效率方面具有显著的优势。在建模和实验研究中探索了这种具有18个隔层的吸管的例子，这可能会将LoKI等大型仪器所需的层数减少2.8倍。在平行发展中，介绍了一种全新的硼涂层探测器配置，旨在满足单晶衍射仪(如SNS的MaNDi和TOPAZ)和中子反射仪对高空间分辨率和高速率能力的需求。所提出的结构是一个紧密排列的矩形电池阵列，每个电池都是通过包裹铜箔制造的，铜箔的一面是10B4C涂层，另一面是电镀锡，周围是精密加工的矩形棒。阵列被压在一起，然后真空钎焊在一起。由此产生的结构在几何上相当坚固和精确。这种所谓的微细胞吸管阵列可以配置小至0.5 mm × 2.5 mm的通道尺寸。由于它的超薄壁(25 μm)，中子的二次散射最小。它被密封在一个完全焊接的薄铝容器内，可以方便地在真空中操作。提出了一种成熟的低功耗读出系统，在15 × 15 cm2的探测器中估计计数率为22 MHz。这些改进是BCS设计最近取得进展的结果，这是由用于国土安全和军事应用的紧凑型高灵敏度监视器的发展所推动的。
{"title":"Recent improvements in straw neutron detectors for large-scale neutron science instruments","authors":"J. Lacy, A. Athanasiades, Christopher S. Martin, Richard Nguyen, Stephen Davenport, T. Lyons, Yangwei Liu","doi":"10.3233/JNR-190138","DOIUrl":"https://doi.org/10.3233/JNR-190138","url":null,"abstract":"Modified boron-coated straw (BCS) detector configurations are introduced, in order to improve detection efficiency, and reduce the number of layers required to match the response of high-pressure 3He tubes, in large-scale neutron science instruments. A new 7-straw design employing thin-walled aluminum tubes facilitates operation in vacuum, and substantially reduces the scattering material by a factor of 5 compared with the flow-through design of the Multi-Grid detector. Another design introduces 18 radial walls inside each straw, coated on both sides with enriched boron carbide, to increase the coated wall perimeter 4.3 times. The so-called Pie straw offers a significant benefit in detection efficiency compared with round straws used in LoKI. An example of such a straw having 18 septa is explored in modeling and experimental studies, that can potentially reduce the number of layers needed in large-scale instruments like LoKI by a factor of 2.8. In a parallel development, a totally new configuration of boron-coated detectors is introduced, aimed to address the need for high spatial resolution, and high-rate capability in single crystal diffractometers, like MaNDi and TOPAZ at the SNS, and in neutron reflectometers. The proposed structure is a close-packed array of rectangular cells, each fabricated by wrapping copper foil having a coating of 10B4C on one side and electroplated tin on the other side, around precisely machined rectangular bars. The array is pressed together and then vacuum brazed together. The resulting structure is quite strong and precise in geometry. This so-called Microcell Straw Array can be configured with channel dimensions as small as 0.5 mm × 2.5 mm. Due to its ultra thin walls (25 μm) secondary scattering of neutrons is minimized. It is sealed inside a fully welded thin aluminum containment vessel that allows convenient operation in vacuum. A mature low power readout system capable of an estimated count rate of 22 MHz in a 15 × 15 cm2 detector is also proposed. The improvements are the result of recent advances in BCS design, spurred by the development of compact, high-sensitivity monitors for homeland security and military applications.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":"22 1","pages":"353-369"},"PeriodicalIF":1.1,"publicationDate":"2020-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/JNR-190138","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46530146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Mastinu, D. Bisello, Rogelio Alfonso Barrera, I. Porras, G. Prete, L. Silvestrin, J. Wyss
In this contribution we describe NEPIR, the fast-neutron irradiation facility under construction at the 70 MeV cyclotron SPES facility of the INFN laboratory of Legnaro (LNL). NEPIR will be constructed in stages, according to the available funds. The initial configuration, based on a thick Be neutron production target, will be operational in 2022; it will be used for shielding studies against fast neutrons for space applications and to investigate neutron-induced Single Event Effects (SEE) in microelectronic devices and systems. In its final configuration NEPIR will have two target systems: one will deliver a Quasi Mono-energetic Neutron (QMN) beam, of general interest, with an adjustable energy peak in the 20–70 MeV range; the second target will deliver a specialized continuous energy neutron beam for studying the effects of fast neutrons produced in cosmic ray air-showers in electronic devices and systems. We review the use of NEPIR to characterize the sensitivity of electronics, describe the neutron production targets and the facility layout. In closing we describe ways, presently under investigation, to use the 15 MV XTU Tandem of LNL to produce nearly monochromatic fast neutrons that would complement the QMN system by allowing one to probe for SEE below 20 MeV.
{"title":"Fast neutrons at LNL Legnaro","authors":"P. Mastinu, D. Bisello, Rogelio Alfonso Barrera, I. Porras, G. Prete, L. Silvestrin, J. Wyss","doi":"10.3233/jnr-200156","DOIUrl":"https://doi.org/10.3233/jnr-200156","url":null,"abstract":"In this contribution we describe NEPIR, the fast-neutron irradiation facility under construction at the 70 MeV cyclotron SPES facility of the INFN laboratory of Legnaro (LNL). NEPIR will be constructed in stages, according to the available funds. The initial configuration, based on a thick Be neutron production target, will be operational in 2022; it will be used for shielding studies against fast neutrons for space applications and to investigate neutron-induced Single Event Effects (SEE) in microelectronic devices and systems. In its final configuration NEPIR will have two target systems: one will deliver a Quasi Mono-energetic Neutron (QMN) beam, of general interest, with an adjustable energy peak in the 20–70 MeV range; the second target will deliver a specialized continuous energy neutron beam for studying the effects of fast neutrons produced in cosmic ray air-showers in electronic devices and systems. We review the use of NEPIR to characterize the sensitivity of electronics, describe the neutron production targets and the facility layout. In closing we describe ways, presently under investigation, to use the 15 MV XTU Tandem of LNL to produce nearly monochromatic fast neutrons that would complement the QMN system by allowing one to probe for SEE below 20 MeV.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":"1 1","pages":"1-15"},"PeriodicalIF":1.1,"publicationDate":"2020-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/jnr-200156","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48696902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Hadad, D. Anderson, S. Désert, N. Hadad, S. Olsen, I. Sutton, G. Vehres, D. Adler, B. Ogg, D. Pierce
We present a summary description of the 8th annual international Design and Engineering of Neutron Instruments Meeting (DENIM) which was held in North Bethesda, MD, USA, September 17–19, 2019. DENIM VIII was organized by the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) in combination with the University of Maryland (UMD). DENIM specifically addresses the unique field of neutron instrument engineering, a subcategory of neutron scattering science. DENIM is organized by engineers for engineers who share openly about what works and what doesn’t work in the life cycle design of an instrument used to analyze materials with neutrons. DENIM is held under the patronage of the International Society of Neutron Instrument Engineers which was formed in 2017. At DENIM VIII, there were 3 keynote talks, 29 additional presentations and 13 posters (presented to the plenary in a poster slam session). Attendees toured the unique labs at NIST including the NCNR. Four parallel knowledge sharing sessions helped attendees explore mutual challenges and solutions in the areas of Instrument Installation Survey and Alignment, Electrical Grounding, Choppers and Velocity Selectors, and 3D Printing.
{"title":"8th Design and Engineering of Neutron Instruments Meeting in North Bethesda Maryland, USA 17–19 September 2019","authors":"N. Hadad, D. Anderson, S. Désert, N. Hadad, S. Olsen, I. Sutton, G. Vehres, D. Adler, B. Ogg, D. Pierce","doi":"10.3233/JNR-200174","DOIUrl":"https://doi.org/10.3233/JNR-200174","url":null,"abstract":"We present a summary description of the 8th annual international Design and Engineering of Neutron Instruments Meeting (DENIM) which was held in North Bethesda, MD, USA, September 17–19, 2019. DENIM VIII was organized by the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) in combination with the University of Maryland (UMD). DENIM specifically addresses the unique field of neutron instrument engineering, a subcategory of neutron scattering science. DENIM is organized by engineers for engineers who share openly about what works and what doesn’t work in the life cycle design of an instrument used to analyze materials with neutrons. DENIM is held under the patronage of the International Society of Neutron Instrument Engineers which was formed in 2017. At DENIM VIII, there were 3 keynote talks, 29 additional presentations and 13 posters (presented to the plenary in a poster slam session). Attendees toured the unique labs at NIST including the NCNR. Four parallel knowledge sharing sessions helped attendees explore mutual challenges and solutions in the areas of Instrument Installation Survey and Alignment, Electrical Grounding, Choppers and Velocity Selectors, and 3D Printing.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/JNR-200174","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48666146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A key element of the success of McStas is the component layer where users and developers alike are contributing to the description of new physical models and features. In McStas, components realise all physical elements of the simulated instrument from source via optics and samples to detector. In this second review paper of the McStas package, we present an overview of the component classes in McStas: sources, monitors, optics, samples, misc, and contrib. Within each component class we give thorough examples of high-quality components, including their algorithms and example use. We present two example instruments, one for a continuous source and one for a time-of-flight source, that together demonstrate the use of the main component classes. Finally, we give tips and instructions that will allow the reader to write good components and elucidate the pathway of contributing new components to McStas.
{"title":"McStas (ii): An overview of components, their use, and advice for user contributions","authors":"P. Willendrup, K. Lefmann","doi":"10.3233/JNR-200186","DOIUrl":"https://doi.org/10.3233/JNR-200186","url":null,"abstract":"A key element of the success of McStas is the component layer where users and developers alike are contributing to the description of new physical models and features. In McStas, components realise all physical elements of the simulated instrument from source via optics and samples to detector. In this second review paper of the McStas package, we present an overview of the component classes in McStas: sources, monitors, optics, samples, misc, and contrib. Within each component class we give thorough examples of high-quality components, including their algorithms and example use. We present two example instruments, one for a continuous source and one for a time-of-flight source, that together demonstrate the use of the main component classes. Finally, we give tips and instructions that will allow the reader to write good components and elucidate the pathway of contributing new components to McStas.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/JNR-200186","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45481819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present an overview of, and an introduction to, the general-purpose neutron simulation package McStas. We present the basic principles behind Monte Carlo ray-tracing simulations of neutrons performed in the package and present a few simple examples. We present the implementation of McStas, the status of the package and its use in the neutron community. Finally, we briefly discuss the planned development of the package.
{"title":"McStas (i): Introduction, use, and basic principles for ray-tracing simulations","authors":"P. Willendrup, K. Lefmann","doi":"10.3233/JNR-190108","DOIUrl":"https://doi.org/10.3233/JNR-190108","url":null,"abstract":"We present an overview of, and an introduction to, the general-purpose neutron simulation package McStas. We present the basic principles behind Monte Carlo ray-tracing simulations of neutrons performed in the package and present a few simple examples. We present the implementation of McStas, the status of the package and its use in the neutron community. Finally, we briefly discuss the planned development of the package.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":"22 1","pages":"1-16"},"PeriodicalIF":1.1,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/JNR-190108","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43561815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jakob Lassa, Magnus Egede Boggild, P. Hedegaard, K. Lefmann
It is generally known that counting statistics is not correctly described by a Gaussian approximation. Nevertheless, in neutron scattering, it is common practice to apply this approximation to the counting statistics; also at low counting numbers. We show that the application of this approximation leads to skewed results not only for low-count features, such as background level estimation, but also for its estimation at double-digit count numbers. In effect, this approximation is shown to be imprecise on all levels of count. Instead, a Multinomial approach is introduced as well as a more standard Poisson method, which we compare with the Gaussian case. These two methods originate from a proper analysis of a multi-detector setup and a standard triple axis instrument. We devise a simple mathematical procedure to produce unbiased fits using the Multinomial distribution and demonstrate this method on synthetic and actual inelastic scattering data. We find that the Multinomial method provide almost unbiased results, and in some cases outperforms the Poisson statistics. Although significantly biased, the Gaussian approach is in general more robust in cases where the fitted model is not a true representation of reality. For this reason, a proper data analysis toolbox for low-count neutron scattering should therefore contain more than one model for counting statistics.
{"title":"Multinomial, Poisson and Gaussian statistics in count data analysis","authors":"Jakob Lassa, Magnus Egede Boggild, P. Hedegaard, K. Lefmann","doi":"10.3233/jnr-190145","DOIUrl":"https://doi.org/10.3233/jnr-190145","url":null,"abstract":"It is generally known that counting statistics is not correctly described by a Gaussian approximation. Nevertheless, in neutron scattering, it is common practice to apply this approximation to the counting statistics; also at low counting numbers. We show that the application of this approximation leads to skewed results not only for low-count features, such as background level estimation, but also for its estimation at double-digit count numbers. In effect, this approximation is shown to be imprecise on all levels of count. Instead, a Multinomial approach is introduced as well as a more standard Poisson method, which we compare with the Gaussian case. These two methods originate from a proper analysis of a multi-detector setup and a standard triple axis instrument. We devise a simple mathematical procedure to produce unbiased fits using the Multinomial distribution and demonstrate this method on synthetic and actual inelastic scattering data. We find that the Multinomial method provide almost unbiased results, and in some cases outperforms the Poisson statistics. Although significantly biased, the Gaussian approach is in general more robust in cases where the fitted model is not a true representation of reality. For this reason, a proper data analysis toolbox for low-count neutron scattering should therefore contain more than one model for counting statistics.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/jnr-190145","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46429080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jurrian Bakker, Adam L. Washington, S. Parnell, A. A. van Well, C. Pappas, W. Bouwman
SESANS data analysis has been implemented in the SasView software package, allowing SESANS experiments to be analyzed using a numerical Hankel transformation of isotropic small-angle scattering (SAS) models. The error of the numerical approximation is three orders of magnitude below typical experimental errors. All advanced data fitting features of SasView (multi-model fitting, batch fitting, and simultaneous/constrained fitting) are now also available for SESANS and this is demonstrated by examples of fitting SAS models to SESANS measurements.
{"title":"Analysis of SESANS data by numerical Hankel transform implementation in SasView","authors":"Jurrian Bakker, Adam L. Washington, S. Parnell, A. A. van Well, C. Pappas, W. Bouwman","doi":"10.3233/jnr-200154","DOIUrl":"https://doi.org/10.3233/jnr-200154","url":null,"abstract":"SESANS data analysis has been implemented in the SasView software package, allowing SESANS experiments to be analyzed using a numerical Hankel transformation of isotropic small-angle scattering (SAS) models. The error of the numerical approximation is three orders of magnitude below typical experimental errors. All advanced data fitting features of SasView (multi-model fitting, batch fitting, and simultaneous/constrained fitting) are now also available for SESANS and this is demonstrated by examples of fitting SAS models to SESANS measurements.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/jnr-200154","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42445738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Kajimoto, M. Nakamura, K. Iida, K. Kamazawa, K. Ikeuchi, Y. Inamura, M. Ishikado
The elastic energy resolution, integrated intensity, and peak intensity of the direct-geometry neutron chopper spectrometer 4SEASONS at Japan Proton Accelerator Research Complex (J-PARC) were re-investigated. This was done with respect to the incident energy and the rotation speed of the Fermi chopper using incoherent scattering of vanadium and simple analytical formulas. The model calculations reproduced the observed values satisfactorily. The present work should be useful for estimating in instrument performance in experiments.
{"title":"Energy resolution and neutron flux of the 4SEASONS spectrometer revisited","authors":"R. Kajimoto, M. Nakamura, K. Iida, K. Kamazawa, K. Ikeuchi, Y. Inamura, M. Ishikado","doi":"10.3233/jnr-200146","DOIUrl":"https://doi.org/10.3233/jnr-200146","url":null,"abstract":"The elastic energy resolution, integrated intensity, and peak intensity of the direct-geometry neutron chopper spectrometer 4SEASONS at Japan Proton Accelerator Research Complex (J-PARC) were re-investigated. This was done with respect to the incident energy and the rotation speed of the Fermi chopper using incoherent scattering of vanadium and simple analytical formulas. The model calculations reproduced the observed values satisfactorily. The present work should be useful for estimating in instrument performance in experiments.","PeriodicalId":44708,"journal":{"name":"Journal of Neutron Research","volume":" ","pages":""},"PeriodicalIF":1.1,"publicationDate":"2020-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3233/jnr-200146","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47432669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：