Measurement of the ^(232)Th(n,f)cross section in the 1-200 MeV range at the CSNS Back-n

The ^(232)Th(n,f)cross section is very important in basic nuclear physics and applications based on the Th/U fuel cycle.Using the time-of-flight method and a multi-cell fast-fission ionization chamber,a novel measurement of the^(232)Th(n,f)cross sec-tion relative to^(235)U in the 1–200 MeV range was performed at the China Spallation Neutron Source Back-n white neutron source(Back-n).The fission event-neutron energy spectra of^(232)Th and^(235)U fission cells were measured in the single-bunch mode.Corrected 232Th/235U fission cross-sectional ratios were obtained,and the measurement uncertainties were 2.5–3.7%for energies in the 2–20 MeV range and 3.6–6.2%for energies in the 20–200 MeV range.The^(232)Th(n,f)cross section was obtained by introducing the standard cross section of^(235)U(n,f).The results were compared with those of previous theoreti-cal calculations,measurements,and evaluations.The measured 232Th fission cross section agreed with the main evaluation results in terms of the experimental uncertainty,and 232Th fission resonances were observed in the 1–3 MeV range.The present results provide^(232)Th(n,f)cross-sectional data for the evaluation and design of Th/U cycle nuclear systems.

Advances in nuclear detection and readout techniques

“A Craftsman Must Sharpen His Tools to Do His Job,”said Confucius.Nuclear detection and readout techniques are the foundation of particle physics,nuclear physics,and particle astrophysics to reveal the nature of the universe.Also,they are being increasingly used in other disciplines like nuclear power generation,life sciences,environmental sciences,medical sciences,etc.The article reviews the short history,recent development,and trend of nuclear detection and readout techniques,covering Semiconductor Detector,Gaseous Detector,Scintillation Detector,Cherenkov Detector,Transition Radiation Detector,and Readout Techniques.By explaining the principle and using examples,we hope to help the interested reader underst and this research field and bring exciting information to the community.

纳米钴蓝共沉淀法制备技术

以硝酸钴、硝酸铝为原料,NaOH或尿素为沉淀剂,采用共沉淀法制备纳米钴蓝。考察了Co/Al摩尔比、沉淀剂种类和煅烧温度等因素对纳米钻蓝呈色性能影响,采用包括可见光分度计等多种方法表征了纳米钴蓝的结构及形貌特征及纳米钴蓝色度值。研究结果表明:(1)煅烧温度为1000℃时,当Co/Al摩尔比从1∶3升至1∶1,钴蓝颜色从蓝色依次向蓝绿色、暗绿色转变,同时,以NaOH为沉淀剂制备的钴蓝其亮度比以尿素为沉淀剂制备的钴蓝高;(2)以NaOH为沉淀剂,Co/Al摩尔比为1∶3时,当煅烧温度为900℃,钴蓝呈蓝绿色,当煅烧温度为1000-1100℃,钴蓝呈蓝色;(3)钴蓝不同制备工艺会改变钴d电子层状态,导致钴蓝呈现不同颜色,最终优化工艺制备的纳米钴蓝粒径为45-65nm,呈尖晶石型晶体结构,色度值为CIE(35.86,-12.63,-34.83)。

Back-n white neutron source at CSNS and its applications

Back-streaming neutrons from the spallation target of the China Spallation Neutron Source(CSNS)that emit through the incoming proton channel were exploited to build a white neutron beam facility(the so-called Back-n white neutron source),which was completed in March 2018.The Back-n neutron beam is very intense,at approximately 29107 n/cm2/s at 55 m from the target,and has a nominal proton beam with a power of 100 kW in the CSNS-I phase and a kinetic energy of 1.6 GeV and a thick tungsten target in multiple slices with modest moderation from the cooling water through the slices.In addition,the excellent energy spectrum spanning from 0.5 eV to 200 MeV,and a good time resolution related tothe time-of-flight measurements make it a typical white neutron source for nuclear data measurements;its overall performance is among that of the best white neutron sources in the world.Equipped with advanced spectrometers,detectors,and application utilities,the Back-n facility can serve wide applications,with a focus on neutron-induced cross-sectional measurements.This article presents an overview of the neutron beam characteristics,the experimental setups,and the ongoing applications at Backn.

Unusual presentation of congenital radioulnar synostosis with osteoporosis,fragility fracture and nonunion:A case report and review of literature

BACKGROUND Congenital radioulnar synostosis(CRUS)is a rare deformity of the upper extremity.It is characterized by loss of rotation of the involved forearm and functional limitations in daily activities.No studies on CRUS with osteoporosis have been reported to date,and osteoporosis is usually recognized as an important dimension of genetic disorder in children.We discuss the possible relationship among this disorder,osteoporosis and fracture nonunion,investigate the strict surgical indications and recommended treatments.CASE SUMMARY A 14-year-old male patient with bilateral CRUS with osteoporosis,fragility fracture and nonunion of fractures in ulna and radius presented our institution for further treatment,complaining of limitation in rotation.The bone mineral density of the hip and lumbar spine was 0.687 g/cm2 and 0.705 g/cm2,respectively,and the Z-score for both was-2.1,which revealed osteoporosis and a high risk of fracture.Tow serum bone turnover markers indicated an imbalance of bone metabolism.Reoperation for ulna fracture with autogenous bone grafting and a postoperative physiotherapy program were adopted rather than the separation of pathological synostosis.Radiological examination,observational posture assessment and limb function scale were evaluated before and 1 year after surgery.At 1 year,the fracture nonunion had almost recovered,forearm movement function on the fracture side was restored,and function on the healthy side was significantly improved compared with that before rehabilitation.CONCLUSION Surgical indications for CRUS vary from person to person.Surgery should not be the first choice of treatment,and physiotherapy is not inferior to surgical treatment.

无机纤维增强哥窑龙泉青瓷胎体研究

以哥窑龙泉青瓷胎体材料为基础,通过引入高强度无机纤维对其进行增强,研究对比了氧化铝纤维与莫来石纤维的加入量对哥窑龙泉青瓷胎体材料的微结构和力学性能的影响。结果表明:两种纤维均通过"拔出效应"提高哥窑胎体的抗弯强度,随着增强纤维加入量的增加,抗弯强度经历了先上升后下降的过程,烧结收缩率持续逐渐降低,在胎体中更稳定的莫来石纤维的增强效果优于氧化铝纤维,当莫来石纤维加入4%时,抗弯强度最大。

Measurement of the neutron total cross section of^(9)Be at the Back-n white neutron source of CSNS

The neutron total cross section data of^(9)Be are essential in the nuclear structure model research of light nuclei and nuclear power installations.The neutron total cross section of^(9)Be in the 0.3 eV−120 MeV energy region has been measured using time-of-flight and transmission methods with the Neutron Total Cross Sectional Spectrometer(NTOX)based on the multi-cell fast fission chamber at the China Spallation Neutron Source(CSNS)-Back-n white neutron source(Back-n).The fission count-neutron energy distributions of ^(235)U and ^(238)U without samples and with Be samples with three thicknesses were measured in the double-bunch operation mode for a beam power of 100 kW.The Bayesian method was used to eliminate the influence of the double-bunch problem on neutron measurement in the energy region above 10 keV.The neutron total cross section of^(9)Be results was consistent with ENDF/B-VIII.0 evaluation library data in the 0.3 eV−20 MeV energy region.In the energy ranges of 0.3 eV to 10 keV and 0.01 to 20 MeV,the deviations between our results and the evaluation results of ENDF/B-VIII.0 were within 2.5%and 15%,respectively.In the resonance energy region,the measured resonance energies in our experiment were 0.63,0.82,and 2.8 MeV,respectively.The results showed that the total cross section uncertainties of three Be samples were within 2.2%in the energy region below 1 MeV.The total cross section uncertainty of 30 mm Be from ^(235)U was the smallest and less than 5%in the energy region of 0.3 eV−120 MeV.The results of this experiment can provide technical support for further data analysis and related nuclear data evaluation.

Initial years'neutron-induced cross-section measurements at the CSNS Back-n white neutron source

The Back-n white neutron source(known as Back-n)is based on back-streaming neutrons from the spallation target at the China Spallation Neutron Source(CSNS).With its excellent beam properties,e.g.,a neutron flux of approximately 1.8×107 n/cm2/s at 55 m from the spallation target,energy range spanning from 0.5 eV to 200 MeV,and time-of-flight resolution of a few per thousand,along with the equipped physical spectrometers,Back-n is considered to be among the best facilities in the world for carrying out nuclear data measurements.Since its completion and commencement of operation in May 2018,five types of cross-section measurements concerning neutron capture cross-sections,fission cross-sections,total cross-sections,light charged particle emissions,in-beam gamma spectra,and more than forty nuclides have been measured.This article presents an overview of the experimental setup and result analysis on the neutron-induced cross-section measurements and gamma spectroscopy at Back-n in the initial years.