An elliptical Gaussian wave formalism model of a charged-particle beam is proposed by analogy with an elliptical Gaussian light beam. In the paraxial approximation, the charged-particle beam can be described as a whol...An elliptical Gaussian wave formalism model of a charged-particle beam is proposed by analogy with an elliptical Gaussian light beam. In the paraxial approximation, the charged-particle beam can be described as a whole by a complex radius of curvature in the real space domains. Therefore, the propagation and transform of charged-particle beam passing through a first-order optical system is represented by the ABCD-like law. As an example of the application of this model, the relation between the beam waist and the minimum beam spot at a fixed target is discussed. The result, well matches that from conventional phase space model, and proves that the Gaussian wave formalism model is highly effective and reasonable.展开更多
An aerosol electrical mobility spectrum analyzer(AEMSA),developed at Hanyang University,was employed to investigate the particle charge characteristics in the Antarctic and Arctic regions.The particle charge character...An aerosol electrical mobility spectrum analyzer(AEMSA),developed at Hanyang University,was employed to investigate the particle charge characteristics in the Antarctic and Arctic regions.The particle charge characteristics in these areas were compared with the charging state in Ansan,South Korea,located in the midlatitude,where artificial factors,such as human activity,urbanization,and traffic,might result in a higher total concentration.Furthermore,in Ansan,South Korea,the charged-particle polarity ratio was very stable and was close to 1.However,notably different particle charge characteristics were obtained in the Antarctic and Arctic regions.The imbalance between the numbers of positively and negatively charged particles was evident,resulting in more positive charges on the atmospheric particles.On average,the positively charged particle concentrations in the Antarctic and Arctic areas were 1.4 and 2.8 times higher,respectively,compared with the negatively charged particles.The developed AEMSA system and the findings of this study provide useful information on the characteristics of atmospheric aerosols in the Antarctic and Arctic regions and can be further utilized to study particle formation mechanisms.展开更多
The Neutralized Drift Compression Experiment-II(NDCX-II)is an induction linac that generates intense pulses of 1.2 MeV helium ions for heating matter to extreme conditions.Here,we present recent results on optimizing ...The Neutralized Drift Compression Experiment-II(NDCX-II)is an induction linac that generates intense pulses of 1.2 MeV helium ions for heating matter to extreme conditions.Here,we present recent results on optimizing beam transport.The NDCX-II beamline includes a 1-m-long drift section downstream of the last transport solenoid,which is filled with charge-neutralizing plasma that enables rapid longitudinal compression of an intense ion beam against space-charge forces.The transport section on NDCX-II consists of 28 solenoids.Finding optimal field settings for a group of solenoids requires knowledge of the envelope parameters of the beam.Imaging the beam on the scintillator gives the radius of the beam,but the envelope angle is not measured directly.We demonstrate how the parameters of the beam envelope(radius,envelop angle,and emittance)can be reconstructed from a series of images taken by varying the B-field strengths of a solenoid upstream of the scintillator.We use this technique to evaluate emittance at several points in the NDCX-II beamline and for optimizing the trajectory of the beam at the entry of the plasma-filled drift section.展开更多
Irradiation protection of the nonlinear optical devices used in the spacecraft and next generation active laser system must be solved. The first problem was to find the irradiation damage mechanism of the nonlinear ma...Irradiation protection of the nonlinear optical devices used in the spacecraft and next generation active laser system must be solved. The first problem was to find the irradiation damage mechanism of the nonlinear materials. In this paper the irradiation electronic field originating from high speed charged particle beams was discussed. The calculating model of the electronic field, based on the relativistic mechanics and electro-magnetic theory, was founded. The common characters of the irradiation electronic field were predicted and the fields of α ray and β ray were calculated by means of our model. The simulating results showed that the intensity of the electric field increased with the energy or the intensity of the beam. The results also showed that the field change trend of α ray and β ray was similar, but the field value was quite different. When the beam intensity I = 100 μA and the beam energy εm = 500 Mev, the electronic field values were about 3.5 × 107 v/m for α ray and 2.4 × 1011 v/m for β ray.展开更多
The energy-momentum distributions of Einstein's simplest static geometrical model for an isotropic and homogeneous universe are evaluated. For this purpose, Einstein, Bergmann-Thomson, Landau-Lifshitz (LL), Moller ...The energy-momentum distributions of Einstein's simplest static geometrical model for an isotropic and homogeneous universe are evaluated. For this purpose, Einstein, Bergmann-Thomson, Landau-Lifshitz (LL), Moller and Papapetrou energy-momentum complexes are used in general relativity. While Einstein and Bergmann-Thomson complexes give exactly the same results, LL and Papapetrou energy-momentum complexes do not provide the same energy densities. The Moller energy-momentum density is found to be zero everywhere in Einstein's universe. Also, several spacetimes are the limiting cases considered here.展开更多
In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever mo...In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.展开更多
Using a Langevin model, we calculate post-saddle proton and α-particle multiplicities as a function of the post-saddle dissipation strength (β) for the heavy systems 234Cf, 240Cf, 246Cf and 240U. We find that, wit...Using a Langevin model, we calculate post-saddle proton and α-particle multiplicities as a function of the post-saddle dissipation strength (β) for the heavy systems 234Cf, 240Cf, 246Cf and 240U. We find that, with increasing isospin of the system, the sensitivity of post-saddle light charged-particle multiplicities to β decreases considerably and, moreover, for 240U the charged-particle multiplicities are no longer sensitive to β. These results suggest that in order to determine the post-saddle friction strength more accurately by measuring the multiplicities of pre-scission protons and α particles, it is best to populate those heavy compound systems with low isospin.展开更多
文摘An elliptical Gaussian wave formalism model of a charged-particle beam is proposed by analogy with an elliptical Gaussian light beam. In the paraxial approximation, the charged-particle beam can be described as a whole by a complex radius of curvature in the real space domains. Therefore, the propagation and transform of charged-particle beam passing through a first-order optical system is represented by the ABCD-like law. As an example of the application of this model, the relation between the beam waist and the minimum beam spot at a fixed target is discussed. The result, well matches that from conventional phase space model, and proves that the Gaussian wave formalism model is highly effective and reasonable.
基金supported by the research fund of Hanyang University(HY-2019-P).
文摘An aerosol electrical mobility spectrum analyzer(AEMSA),developed at Hanyang University,was employed to investigate the particle charge characteristics in the Antarctic and Arctic regions.The particle charge characteristics in these areas were compared with the charging state in Ansan,South Korea,located in the midlatitude,where artificial factors,such as human activity,urbanization,and traffic,might result in a higher total concentration.Furthermore,in Ansan,South Korea,the charged-particle polarity ratio was very stable and was close to 1.However,notably different particle charge characteristics were obtained in the Antarctic and Arctic regions.The imbalance between the numbers of positively and negatively charged particles was evident,resulting in more positive charges on the atmospheric particles.On average,the positively charged particle concentrations in the Antarctic and Arctic areas were 1.4 and 2.8 times higher,respectively,compared with the negatively charged particles.The developed AEMSA system and the findings of this study provide useful information on the characteristics of atmospheric aerosols in the Antarctic and Arctic regions and can be further utilized to study particle formation mechanisms.
基金This work is supported by the Office of Science of the US DOE under contracts DE-AC0205CH11231,DE-AC52-07NA27344,and DE-AC02-09CH11466.
文摘The Neutralized Drift Compression Experiment-II(NDCX-II)is an induction linac that generates intense pulses of 1.2 MeV helium ions for heating matter to extreme conditions.Here,we present recent results on optimizing beam transport.The NDCX-II beamline includes a 1-m-long drift section downstream of the last transport solenoid,which is filled with charge-neutralizing plasma that enables rapid longitudinal compression of an intense ion beam against space-charge forces.The transport section on NDCX-II consists of 28 solenoids.Finding optimal field settings for a group of solenoids requires knowledge of the envelope parameters of the beam.Imaging the beam on the scintillator gives the radius of the beam,but the envelope angle is not measured directly.We demonstrate how the parameters of the beam envelope(radius,envelop angle,and emittance)can be reconstructed from a series of images taken by varying the B-field strengths of a solenoid upstream of the scintillator.We use this technique to evaluate emittance at several points in the NDCX-II beamline and for optimizing the trajectory of the beam at the entry of the plasma-filled drift section.
文摘Irradiation protection of the nonlinear optical devices used in the spacecraft and next generation active laser system must be solved. The first problem was to find the irradiation damage mechanism of the nonlinear materials. In this paper the irradiation electronic field originating from high speed charged particle beams was discussed. The calculating model of the electronic field, based on the relativistic mechanics and electro-magnetic theory, was founded. The common characters of the irradiation electronic field were predicted and the fields of α ray and β ray were calculated by means of our model. The simulating results showed that the intensity of the electric field increased with the energy or the intensity of the beam. The results also showed that the field change trend of α ray and β ray was similar, but the field value was quite different. When the beam intensity I = 100 μA and the beam energy εm = 500 Mev, the electronic field values were about 3.5 × 107 v/m for α ray and 2.4 × 1011 v/m for β ray.
文摘The energy-momentum distributions of Einstein's simplest static geometrical model for an isotropic and homogeneous universe are evaluated. For this purpose, Einstein, Bergmann-Thomson, Landau-Lifshitz (LL), Moller and Papapetrou energy-momentum complexes are used in general relativity. While Einstein and Bergmann-Thomson complexes give exactly the same results, LL and Papapetrou energy-momentum complexes do not provide the same energy densities. The Moller energy-momentum density is found to be zero everywhere in Einstein's universe. Also, several spacetimes are the limiting cases considered here.
基金the Ministry of Science and Technology of China(No.2016YFA0400302)the National Natural Sciences Foundation of China(Nos.11775142 and U1965201)the Chinese Academy of Sciences Center for Excellence in Particle Physics(CCEPP).
文摘In experiments searching for rare signals,background events from the detector itself are some of the major factors limiting search sensitivity.Screening for ultra-low radioactive detector materials is becoming ever more essential.We propose to develop a gaseous time projection chamber(TPC)with a Micromegas readout for radio screening.The TPC records three-dimensional trajectories of charged particles emitted from a flat sample placed in the active volume of the detector.The detector can distinguish the origin of an event and identify the particle types with information from trajectories,which significantly increases the screening sensitivity.For a particles from the sample surface,we observe that our proposed detector can reach a sensitivity higher than 100 l Bq m-2 within two days.
基金Supported by National Nature Science Foundation of China (10405007)Scientific Research Foundation of the Ministry of Education of China for Returned Overseas Scholars
文摘Using a Langevin model, we calculate post-saddle proton and α-particle multiplicities as a function of the post-saddle dissipation strength (β) for the heavy systems 234Cf, 240Cf, 246Cf and 240U. We find that, with increasing isospin of the system, the sensitivity of post-saddle light charged-particle multiplicities to β decreases considerably and, moreover, for 240U the charged-particle multiplicities are no longer sensitive to β. These results suggest that in order to determine the post-saddle friction strength more accurately by measuring the multiplicities of pre-scission protons and α particles, it is best to populate those heavy compound systems with low isospin.