The LaBr3(Ce)detector has attracted much attention in recent years because of its superior characteristics compared with other scintillating materials in terms of resolution and efficiency.However,it has a relatively ...The LaBr3(Ce)detector has attracted much attention in recent years because of its superior characteristics compared with other scintillating materials in terms of resolution and efficiency.However,it has a relatively high intrinsic background radiation because of the naturally occurring radioisotopes in lanthanum,actinium,and their daughter nuclei.This limits its applications in low-counting rate experiments.In this study,we identified the radioactive isotopes in theφ3"x 3"Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system.Moreover,we carried out a Geant4 simulation of the experimental spectra to evaluate the activities of the main internal radiation components.The total activity of the background radiation of B380 is determined to be 1.523(34)Bq/cm^3.The main sources include 138La at 1.428(34)Bq/cm^3,207Tl at 0.0135(13)Bq/cm^3,211Bi at 0.0136(15)Bq/cm^3,215Po at 0.0135(3)Bq/cm^3,219Rn at 0.0125(12)Bq/cm^3,223Fr at 0.0019(11)Bq/cm^3,223Ra at 0.0127(10)Bq/cm^3,227Th at 0.0158(22)Bq/cm^3,and 227Ac at 0.0135(13)Bq/cm^3.Of these,the activities of 207Tl,211Po,215Po,223Fr,and 227Ac are deduced for the first time from the secular equilibrium established in the decay chain of 227Ac.展开更多
A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of ...A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10^-13/s at 5 MHz, and the self-calibration resolution can achieve 10^-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10^-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.展开更多
When there eaist many light elements in a sample or the sample is thick, a reliable (d,p) reaction analysis cannot be often obtained due to the interference of particle groupscorresponding to different elements and ev...When there eaist many light elements in a sample or the sample is thick, a reliable (d,p) reaction analysis cannot be often obtained due to the interference of particle groupscorresponding to different elements and even different energy levels of an element. Therefore,(d,pγ) coincidence technique is tried. By measuring a charged particle(proton) group in coincidence with its accompanying gamma rays, the background can be greatly suppressed andthe interference can be effectively eliminated.展开更多
We analyze the spin coincidence experiment considered by Bell in the derivation of Bells theorem. We solve the equation of motion for the spin system with a spin Hamiltonian, Hz, where the magnetic field is only in th...We analyze the spin coincidence experiment considered by Bell in the derivation of Bells theorem. We solve the equation of motion for the spin system with a spin Hamiltonian, Hz, where the magnetic field is only in the z-direction. For the specific case of the coincidence experiment where the two magnets have the same orientation the Hamiltonian Hz commutes with the total spin Iz, which thus emerges as a constant of the motion. Bells argument is then that an observation of spin up at one magnet A necessarily implies spin down at the other B. For an isolated spin system A-B with classical translational degrees of freedom and an initial spin singlet state there is no force on the spin particles A and B. The spins are fully entangled but none of the spin particles A or B are deflected by the Stern-Gerlach magnets. This result is not compatible with Bells assumption that spin 1/2 particles are deected in a Stern-Gerlach device. Assuming a more realistic Hamiltonian Hz + Hx including a gradient in x direction the total Iz is not conserved and fully entanglement is not expected in this case. The conclusion is that Bells theorem is not applicable to spin coincidence measurement originally discussed by Bell.展开更多
Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics es...Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE （China Institute of Atomic Energy）.展开更多
基金This work was supported by the National Key R&D program of China(No.2016YFA0400504)by the National Natural Science Foundation of China(Nos.U1832211,U1867210,11922501,11961141004,11575018,11790322,and U1932209).
文摘The LaBr3(Ce)detector has attracted much attention in recent years because of its superior characteristics compared with other scintillating materials in terms of resolution and efficiency.However,it has a relatively high intrinsic background radiation because of the naturally occurring radioisotopes in lanthanum,actinium,and their daughter nuclei.This limits its applications in low-counting rate experiments.In this study,we identified the radioactive isotopes in theφ3"x 3"Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system.Moreover,we carried out a Geant4 simulation of the experimental spectra to evaluate the activities of the main internal radiation components.The total activity of the background radiation of B380 is determined to be 1.523(34)Bq/cm^3.The main sources include 138La at 1.428(34)Bq/cm^3,207Tl at 0.0135(13)Bq/cm^3,211Bi at 0.0136(15)Bq/cm^3,215Po at 0.0135(3)Bq/cm^3,219Rn at 0.0125(12)Bq/cm^3,223Fr at 0.0019(11)Bq/cm^3,223Ra at 0.0127(10)Bq/cm^3,227Th at 0.0158(22)Bq/cm^3,and 227Ac at 0.0135(13)Bq/cm^3.Of these,the activities of 207Tl,211Po,215Po,223Fr,and 227Ac are deduced for the first time from the secular equilibrium established in the decay chain of 227Ac.
基金supported by the National Natural Science Foundation of China (Grant Nos.60772135 and 10978017)the Open Fund of Key Laboratory of Precision Navigation and Technology,National Time Service Center,Chinese Academy of Sciences (Grant No.2009PNTT10)the Fundamental Research Funds for the Central Universities,China (Grant No.JY10000905015)
文摘A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10^-13/s at 5 MHz, and the self-calibration resolution can achieve 10^-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10^-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.
文摘When there eaist many light elements in a sample or the sample is thick, a reliable (d,p) reaction analysis cannot be often obtained due to the interference of particle groupscorresponding to different elements and even different energy levels of an element. Therefore,(d,pγ) coincidence technique is tried. By measuring a charged particle(proton) group in coincidence with its accompanying gamma rays, the background can be greatly suppressed andthe interference can be effectively eliminated.
文摘We analyze the spin coincidence experiment considered by Bell in the derivation of Bells theorem. We solve the equation of motion for the spin system with a spin Hamiltonian, Hz, where the magnetic field is only in the z-direction. For the specific case of the coincidence experiment where the two magnets have the same orientation the Hamiltonian Hz commutes with the total spin Iz, which thus emerges as a constant of the motion. Bells argument is then that an observation of spin up at one magnet A necessarily implies spin down at the other B. For an isolated spin system A-B with classical translational degrees of freedom and an initial spin singlet state there is no force on the spin particles A and B. The spins are fully entangled but none of the spin particles A or B are deflected by the Stern-Gerlach magnets. This result is not compatible with Bells assumption that spin 1/2 particles are deected in a Stern-Gerlach device. Assuming a more realistic Hamiltonian Hz + Hx including a gradient in x direction the total Iz is not conserved and fully entanglement is not expected in this case. The conclusion is that Bells theorem is not applicable to spin coincidence measurement originally discussed by Bell.
基金Supported by State Key Development Program for Basic Research of China (2009GB107001, 2008CB717803, 2007CB209903)Research Fund for Doctoral Program of Higher Education of China (200610011023)
文摘Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE （China Institute of Atomic Energy）.
