Bunching of elementary steps by solution flow is still not yet clarified for protein crystals. Hence, in this study, we observed elementary steps on crystal surfaces of model protein hen egg-white lysozyme （HEWL） un...Bunching of elementary steps by solution flow is still not yet clarified for protein crystals. Hence, in this study, we observed elementary steps on crystal surfaces of model protein hen egg-white lysozyme （HEWL） under forced flow conditions, by our advanced optical microscopy. We found that in the case of a HEWL solution of 99.99% purity, forced flow changed bunched steps into elementary ones （debunching） on tetragonal HEWL crystals. In contrast, in the case of a HEWL solution of 98.5% purity, forced flow significantly induced bunching of elementary steps. These results indicate that in the case of HEWL crystals, the mass transfer of impurities is more significantly enhanced by forced solution flow than that of solute HEWL molecules. We also showed that forced flow induced the incorporation of microcrystals into a mother crystal and the subsequent formation of screw dislocations and spiral growth hillocks.展开更多
The experimental result of terahertz （THz） coherent transition radiation generated from an ultrashort electron bunching beam is reported. During this experiment, the window for THz transmission from ultrahigh vacuum...The experimental result of terahertz （THz） coherent transition radiation generated from an ultrashort electron bunching beam is reported. During this experiment, the window for THz transmission from ultrahigh vacuum to free air is tested. The compact measurement system which can simultaneously test the THz wave power and frequency is built and proofed. With the help of improved Martin-Puplett interferometer and Kramers-Krong transform, the longitudinal bunch length is measured. The results show that the peak power of THz radiation wave is more than 80 kW, and its radiation frequency is from 0.1 THz to 1.5 THz.展开更多
Data collected from truck payload management systems at various surface mines shows that the payload variance is significant and must be considered in analysing the mine productivity,energy consumption,greenhouse gas ...Data collected from truck payload management systems at various surface mines shows that the payload variance is significant and must be considered in analysing the mine productivity,energy consumption,greenhouse gas emissions and associated cost.Payload variance causes significant differences in gross vehicle weights.Heavily loaded trucks travel slower up ramps than lightly loaded trucks.Faster trucks are slowed by the presence of slower trucks,resulting in‘bunching’,production losses and increasing fuel consumptions.This paper simulates the truck bunching phenomena in large surface mines to improve truck and shovel systems’efficiency and minimise fuel consumption.The study concentrated on completing a practical simulation model based on a discrete event method which is most commonly used in this field of research in other industries.The simulation model has been validated by a dataset collected from a large surface mine in Arizona state,USA.The results have shown that there is a good agreement between the actual and estimated values of investigated parameters.展开更多
This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on ...This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the AI：Ti composition with no more than 50 at.% Al. The specific contact resistance （SCR） is obtained to be as low as 2.6 × 10-6Ωcm2 for the bilayered Ti（100 nm）/Al（100 nm） contact treated with 3 rain rapid thermal annealing （RTA） at 1000 ℃. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti3SiC2 dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti3 SiC2 layer with （0001）-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing.展开更多
We report our recent progress in the design and simulation of a high-brightness S-band photo-injector with a ballistic bunching scheme aimed at driving an inverse Compton scattering(ICS)X-ray source.By adding a short ...We report our recent progress in the design and simulation of a high-brightness S-band photo-injector with a ballistic bunching scheme aimed at driving an inverse Compton scattering(ICS)X-ray source.By adding a short standing-wave buncher between the RF gun and first booster in a conventional S-band photo-injector,electron bunches with a 500 pC charge can be compressed to the sub-picosecond level with very limited input RF power and an unchanged basic layout of the photo-injector.Beam dynamics analysis indicates that fine tuning of the focusing strength of the gun and linac solenoid can well balance additional focusing provided by the standing wave buncher and generate a well-compensated transverse emittance.Thorough bunching dynamics simulations with different operating conditions of the buncher show that a buncher with more cells and a moderate gradient is suitable for simultaneously obtaining a short bunch duration and low emittance.In a typical case of a 9-cell buncher with a 38 MV/m gradient,an ultrashort bunch duration of 0.5 ps(corresponding to a compression ratio of>5)and a low emittance of<1 mm mrad can be readily obtained for a 500 pC electron pulse.This feasible ballistic bunching scheme will facilitate the implementation of an ultrashort pulse mode inverse Compton scattering X-ray source on most existing S-band photo-injectors.展开更多
We investigate the effect of the dipole–dipole interaction(DDI) on the photon statistics with two atoms trapped in an optical cavity driven by a laser field and subjected to cooperative emission. By means of the quan...We investigate the effect of the dipole–dipole interaction(DDI) on the photon statistics with two atoms trapped in an optical cavity driven by a laser field and subjected to cooperative emission. By means of the quantum trajectory analysis and the second-order correlation functions, we show that the photon statistics of the cavity transmission can be flexibly modulated by the DDI while the incoming coherent laser selectively excites the atom–cavity system’s nonlinear Jaynes–Cummings ladder of excited states. Finally, we find that the effect of the cooperatively atomic emission can also be revealed by the numerical simulations and can be explained with a simplified picture. The DDI induced nonlinearity gives rise to highly nonclassical photon emission from the cavity that is significant for quantum information processing and quantum communication.展开更多
The formation of macrostep during high-temperature phase of barium meta-borate （^-BaB204） single crystal growth has been investigated by both optical in-situ observation system and atomic force microscopy （AFM）. T...The formation of macrostep during high-temperature phase of barium meta-borate （^-BaB204） single crystal growth has been investigated by both optical in-situ observation system and atomic force microscopy （AFM）. The in- si$u observation results demonstrate that the critical linear size of growing facet exceeding the size that the macrostep generates is significantly anisotropic. The critical linear sizes are around 280 ~m and 620 ~m for {1010} and （T010} planes, respectively. AFM study illustrates that macrostep train with a height of 150 nm^200 nm is one typical morphological feature of the as-grown crystal surface. The riser of each macrostep consists of several straight and parallel sub-steps, indicating the occurrence of step bunching. Additionally, triangular sub-steps with heights of several nanometers on the treads of the macrosteps are found to be another typical feature of surface morphology, which implies a microscopically competitive bunching of sub-steps between various crystallographic orientations.展开更多
We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible phys...We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation,a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus,the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.展开更多
Purpose The High Energy Photon Source is a fourth-generation synchrotron radiation source being built in China.It is comprised of a storage ring,a full energy booster,a 500-MeV Linac and three transport lines.The puls...Purpose The High Energy Photon Source is a fourth-generation synchrotron radiation source being built in China.It is comprised of a storage ring,a full energy booster,a 500-MeV Linac and three transport lines.The pulse charge at the exit of the Linac is required to be up to 7 nC.Both single bunch and three bunches in a beam pulse might be needed according to the studies on instabilities of the booster and the beam dynamic of the main Linac.Methods A bunching system consisting of both sub-harmonic and fundamental frequency structures is designed to meet the requirements.To obtain high transmission efficiency and control the emittance growth,multi-objective genetic algorithm is introduced to optimize the electromagnetic parameters of these structures.Results In this paper,detailed optimization process and the final results are presented.The total transmission efficiency of the bunching system is 97%,and the transmission efficiency of the main bunch is 95%.The normalized RMS emittance of 8.5 nC included beam charge is smaller than 60 mm mrad.Conclusions The design of the bunching system is presented,and both the pulse charge and the beam emittance well meet the design requirement.展开更多
Generally, a standard bunching system is composed by an SW pre-buncher, a TW buncher and a standard accelerating section. However, there is one way to simplify the whole system to some extent by using the hybrid bunch...Generally, a standard bunching system is composed by an SW pre-buncher, a TW buncher and a standard accelerating section. However, there is one way to simplify the whole system to some extent by using the hybrid buncher, which is a combined structure of the SW pre-buncher and the TW buncher. Here the beam dynamics studies on an S-band bunching system with the hybrid buncher is presented, and simulation results show that similar beam performance can be obtained at the linac exit by using this kind of bunching system rather than the standard one. In the meantime, the structure design of the hybrid buncher is also described. Furthermore, the standard accelerating section can also be integrated with the hybrid buncher, which can further simplify the usual bunching system and lower the construction cost.展开更多
We present the analytical and simulated results of our study of the influence of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a travelling wave accelerating...We present the analytical and simulated results of our study of the influence of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a travelling wave accelerating structure as a compressor. Our study shows that the bunch compression application with low acceleration gradient is more tolerant to phase jitter and more successful in obtaining a compressed electron beam with symmetrical longitudinal distribution and low energy spread. We also present a transverse emittance compensation scheme to compensate the emittance growth caused by the increase of the space charge force in the compressing process, which is easy to adjust for different compression factors.展开更多
Bus bunching has been a persistent issue in urban bus system since it first appeared,and it remains a challenge not fully resolved.This phenomenon may reduce the operational efficiency of the urban bus system,which is...Bus bunching has been a persistent issue in urban bus system since it first appeared,and it remains a challenge not fully resolved.This phenomenon may reduce the operational efficiency of the urban bus system,which is detrimental to the operation of fast-paced public transport in cities.Fortunately,extensive research has been undertaken in the long development and optimization of the urban bus system,and many solutions have emerged so far.The purpose of this paper is to summarize the existing solutions and serve as a guide for subsequent research in this area.Upon careful examination of current findings,it is found that,based on the different optimization objects,existing solutions to the bus bunching problem can be divided into five directions,i.e.,operational strategy improvement,traffic control improvement,driver driving rules improvement,passenger habit improvement,and others.While numerous solutions to bus bunching are available,there remains a gap in research exploring the integrated application of methods from diverse directions.Furthermore,with the development of autonomous driving,it is expected that the use of modular autonomous vehicles could be the most potential solution to the issue of bus bunching in the future.展开更多
Increasing the peak brightness is beneficial to various applications of the Thomson scattering X-ray source. A higher peak brightness of the scattered X-ray pulse demands a shorter scattering electron beam realized by...Increasing the peak brightness is beneficial to various applications of the Thomson scattering X-ray source. A higher peak brightness of the scattered X-ray pulse demands a shorter scattering electron beam realized by beam compression in the electron beam-line. In this article, we study the possibility of compressing the electron beam in a typical S-band normal conducting photo-injector via ballistic bunching, through just adding a short RF linac section right behind the RF gun, so as to improve the peak brightness of the scattered x-ray pulse. Numerical optimization by ASTRA demonstrates that the peak current can increase from 50 A to 300 A for a 500 pC, 10 ps FWHM electron pulse, while normalized transverse RMS emittance and RMS energy spread increases very little. Correspondingly, the peak brightness of the Thomson scattering X-ray source is estimated to increase about three times.展开更多
In PASER （particle acceleration by stimulated emission of radiation）, in the presence of an active medium incorporated in a Penning trap, moving electrons can become bunched, and as they get enough energy, they esca...In PASER （particle acceleration by stimulated emission of radiation）, in the presence of an active medium incorporated in a Penning trap, moving electrons can become bunched, and as they get enough energy, they escape the trap forming an optical injector. These bunched electrons can enter the next PASER section filled with the same active medium to be accelerated. In this paper, electron dynamics in the presence of a gas mixture active medium incorporated in a Penning trap is analyzed by developing an idealized 1D model. We evaluate the energy exchange occurring as the train of electrons traverses into the next PASER section. The results show that the oscillating electrons can be bunched at the resonant frequency of the active medium. The influence of the trapped time and population inversion are analyzed, showing that the longer the electrons are trapped, the more energy from the medium the accelerated electrons get, and with the increase of population inversion, the decelerated electrons are virtually unchanged but the accelerated electrons more than double their peak energy values. The simulation results show that the gas active medium needs a lower population inversion to bunch the electrons compared to a solid active medium, so the experimental conditions can easily be achieved.展开更多
This study entailed the development of a high-gradient modulation of microbunching for traditional radiation frequency accelerators using a minimized system driven by a relativistic Laguerre–Gaussian(LG)laser in thre...This study entailed the development of a high-gradient modulation of microbunching for traditional radiation frequency accelerators using a minimized system driven by a relativistic Laguerre–Gaussian(LG)laser in three-dimensional particlein-cell(PIC)simulations.It was observed that the LG laser could compress the transverse dimension of the beam to within a 0.7μm radius(divergence≈4.3 mrad),which is considerably lower than the case tuned by a Gaussian laser.In addition,the electron beam could be efficiently modulated to a high degree of bunching effect(>0.5)within~21 fs(~7μm)in the longitudinal direction.Such a high-gradient density modulation driven by an LG laser for pre-bunched,low-divergence,and stable electron beams provides a potential technology for the system minimization of X-ray free-electron lasers(XFELs)and ultrashort-scale(attosecond)electron diffraction research.展开更多
The common phenomenon of uneven headway in bus service is explored based on the automatic vehicle location （AVL） data of Route 2 in Yichun City of Jiangxi province from 6：00 to 9：00 in the morning. The headway reg...The common phenomenon of uneven headway in bus service is explored based on the automatic vehicle location （AVL） data of Route 2 in Yichun City of Jiangxi province from 6：00 to 9：00 in the morning. The headway regularity of two stages 6： 00--7：00 and 7： 00--9：00 is comparatively analyzed, and it is found that both the traffic conditions and the passenger demand affect headway regularity. A bus arrival model, which assumes that the dwell time of a bus is linear in headway, is built to probe the effect of scheduled headway, and the model is simulated by Matlab. The simulation results reveal that the departure intervals and fluctuations affect headway regularity. Longer intervals and less fluctuation mean higher regularity of headway. And, the fluctuation has a more obvious influence on headway regularity than the interval. Controlling the fluctuations of scheduled headway can effectively raise the regularity of headway and improve the level of public transport service.展开更多
The use of organic fertilizers is less expensive and advantageous for both the development of the plant and the sanitation of the environment. This is why this investigation aims to promote the ash from emptying of oi...The use of organic fertilizers is less expensive and advantageous for both the development of the plant and the sanitation of the environment. This is why this investigation aims to promote the ash from emptying of oil mill boilers as a source of organic fertilization in the production of palm bunches. To do this, different doses of oil mill boiler emptying ash were tested on oil palms in production. The results showed that the oil palms responded favorably regardless of the dose of oil mill boiler emptying ash. Thus, the comparison of the different doses Tv1 (1 kg), Tv2 (1.5 kg), Tv3 (2 kg), Tv4 (3 kg), Tv5 (4 kg), Tv6 (5 kg) and Tv7 (7 kg) showed that the high doses led to an increase in the weight of the bunches. Better still, the Tv6 treatment at a dose of 5 kg/tree proved to be optimal for good production of palm bunches with a gain of 73.9% compared to the treatment without oil mill boiler emptying ash (absolute control).展开更多
Industrial linear accelerators often contain many bunches when their pulse widths are extended to microseconds.As they typically operate at low electron energies and high currents,the interactions among bunches cannot...Industrial linear accelerators often contain many bunches when their pulse widths are extended to microseconds.As they typically operate at low electron energies and high currents,the interactions among bunches cannot be neglected.In this study,an algorithm is introduced for calculating the space charge force of a train with infinite bunches.By utilizing the ring charge model and the particle-in-cell(PIC)method and combining analytical and numerical methods,the proposed algorithm efficiently calculates the space charge force of infinite bunches,enabling the accurate design of accelerator parameters and a comprehensive understanding of the space charge force.This is a significant improvement on existing simulation software such as ASTRA and PARMELA that can only handle a single bunch or a small number of bunches.The PIC algorithm is validated in long drift space transport by comparing it with existing models,such as the infinite-bunch,ASTRA single-bunch,and PARMELA several-bunch algorithms.The space charge force calculation results for the external acceleration field are also verified.The reliability of the proposed algorithm provides a foundation for the design and optimization of industrial accelerators.展开更多
The utilisation of sugar palm bunches-charcoal briquettes(SPB-CB)represents a significant advancement in biomass energy.This study aimed to analyse the properties of charcoal briquettes produced from SPB(Arenga longip...The utilisation of sugar palm bunches-charcoal briquettes(SPB-CB)represents a significant advancement in biomass energy.This study aimed to analyse the properties of charcoal briquettes produced from SPB(Arenga longipes).The experiment involved categorising the dimensions of charcoal powder into three specific particle sizes:20-40 mesh,40-60 mesh,and particles that could pass through a 60-mesh screen.The charcoal powder will be combined with tapioca as a binding agent at three specific concentrations:11%,13%,and 15%.The research findings indicate that the samples underwent 60 mesh passes achieved the maximum briquette density,with an average value of 0.58 g/cm^(3).The highest attainable compressive strength sample value was 27.52 kgf/cm^(2),which was attained by employing 60 mesh size and 15%adhesive concentration.The calorimetric investigation showed that SPB-charcoal had the highest calorific value of 25.88 MJ/kg,while the SPB-CB had a little lower caloric value of 24.64 MJ/kg.The ash content and volatile matter values showed that the briquettes with the lowest ash content had values of 10.49%and 32.65%,respectively.Furthermore,the carbon fixation values varied between 16.65%and 52.36%.Thermogravimetric analysis indicates that charcoal derived from SPB exhibits superior thermal characteristics compared to charcoal briquettes.However,thermal properties of SPB charcoal do not show significant differences when compared to charcoal briquettes that have been processed with a mesh size of 20-40 and include 11%adhesive.According to this research,it may be inferred that charcoal briquettes made from sugar palm bunches meet the requirements specified in SNI 01-6235-2000.展开更多
A super-radiant terahertz free-electron laser(THz-FEL)light source was developed for the first time in Thailand and Southeast Asia at the PBP-CMU Electron Linac Laboratory(PCELL)of Chiang Mai University.This radiation...A super-radiant terahertz free-electron laser(THz-FEL)light source was developed for the first time in Thailand and Southeast Asia at the PBP-CMU Electron Linac Laboratory(PCELL)of Chiang Mai University.This radiation source requires relatively ultrashort electron bunches to produce intense coherent THz pulses.Three electron bunch compression processes are utilized in the PCELL accelerator system comprising pre-bunch compression in an alpha magnet,velocity bunching in a radio-frequency(RF)linear accelerator(linac),and magnetic bunch compression in a 180°acromat system.Electron bunch compression in the magnetic compressor system poses considerable challenges,which are addressed through the use of three quadrupole doublets.The strengths of the quadrupole fields significantly influence the rotation of the beam line longitudinal phase space distribution along the bunch compressor.Start-to-end beam dynamics simulations using the ASTRA code were performed to optimize the electron beam properties for generating super-radiant THz-FEL radiation.The operational parameters considered in the simulations comprise the alpha magnet gradient,linac RF phase,and quadrupole field strengths.The optimization results show that 10-16MeV femtosecond electron bunches with a low energy spread(~0.2%),small normalized emittance(~15πmm·mrad),and high peak current(165-247A)can be produced by the PCELL accelerator system at the optimal parameters.A THz-FEL with sub-microjoule pulse energies can thus be obtained at the optimized electron beam parameters.The physical and conceptual design of the THz-FEL beamline were completed based on the beam dynamics simulation results.The construction and installation of this beamline are currently underway and expected to be completed by mid-2024.The commissioning of the beamline will then commence.展开更多
基金Chinese Academy of Sciences visiting professorship for senior international scientists(2013T2J0060)
文摘Bunching of elementary steps by solution flow is still not yet clarified for protein crystals. Hence, in this study, we observed elementary steps on crystal surfaces of model protein hen egg-white lysozyme （HEWL） under forced flow conditions, by our advanced optical microscopy. We found that in the case of a HEWL solution of 99.99% purity, forced flow changed bunched steps into elementary ones （debunching） on tetragonal HEWL crystals. In contrast, in the case of a HEWL solution of 98.5% purity, forced flow significantly induced bunching of elementary steps. These results indicate that in the case of HEWL crystals, the mass transfer of impurities is more significantly enhanced by forced solution flow than that of solute HEWL molecules. We also showed that forced flow induced the incorporation of microcrystals into a mother crystal and the subsequent formation of screw dislocations and spiral growth hillocks.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10905032 and 10975088)China Postdoctoral Science Foundation (Grant No.20080440031)the China Postdoctoral Special Science Foundation (Grant No.200902088)
文摘The experimental result of terahertz （THz） coherent transition radiation generated from an ultrashort electron bunching beam is reported. During this experiment, the window for THz transmission from ultrahigh vacuum to free air is tested. The compact measurement system which can simultaneously test the THz wave power and frequency is built and proofed. With the help of improved Martin-Puplett interferometer and Kramers-Krong transform, the longitudinal bunch length is measured. The results show that the peak power of THz radiation wave is more than 80 kW, and its radiation frequency is from 0.1 THz to 1.5 THz.
基金CRC MiningThe University of Queensland for their financial support for this study
文摘Data collected from truck payload management systems at various surface mines shows that the payload variance is significant and must be considered in analysing the mine productivity,energy consumption,greenhouse gas emissions and associated cost.Payload variance causes significant differences in gross vehicle weights.Heavily loaded trucks travel slower up ramps than lightly loaded trucks.Faster trucks are slowed by the presence of slower trucks,resulting in‘bunching’,production losses and increasing fuel consumptions.This paper simulates the truck bunching phenomena in large surface mines to improve truck and shovel systems’efficiency and minimise fuel consumption.The study concentrated on completing a practical simulation model based on a discrete event method which is most commonly used in this field of research in other industries.The simulation model has been validated by a dataset collected from a large surface mine in Arizona state,USA.The results have shown that there is a good agreement between the actual and estimated values of investigated parameters.
基金supported by the Key Specific Projects of Ministry of Education of China(Grant No.625010101)the National Natural Science Foundation of China(Grant No.61234006)+2 种基金the Natural Science Foundation of Shaan Xi Province,China(Grant No.2013JQ8012)the Doctoral Fund of Ministry of Education of China(Grant No.20130203120017)the Specific Project of the Core Devices,China(Grant No.2013ZX0100100-004)
文摘This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the AI：Ti composition with no more than 50 at.% Al. The specific contact resistance （SCR） is obtained to be as low as 2.6 × 10-6Ωcm2 for the bilayered Ti（100 nm）/Al（100 nm） contact treated with 3 rain rapid thermal annealing （RTA） at 1000 ℃. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti3SiC2 dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti3 SiC2 layer with （0001）-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing.
基金supported by National Natural Science Foundation of China(NSFC)(Nos.12005211,11905210,11975218 and 11805192).
文摘We report our recent progress in the design and simulation of a high-brightness S-band photo-injector with a ballistic bunching scheme aimed at driving an inverse Compton scattering(ICS)X-ray source.By adding a short standing-wave buncher between the RF gun and first booster in a conventional S-band photo-injector,electron bunches with a 500 pC charge can be compressed to the sub-picosecond level with very limited input RF power and an unchanged basic layout of the photo-injector.Beam dynamics analysis indicates that fine tuning of the focusing strength of the gun and linac solenoid can well balance additional focusing provided by the standing wave buncher and generate a well-compensated transverse emittance.Thorough bunching dynamics simulations with different operating conditions of the buncher show that a buncher with more cells and a moderate gradient is suitable for simultaneously obtaining a short bunch duration and low emittance.In a typical case of a 9-cell buncher with a 38 MV/m gradient,an ultrashort bunch duration of 0.5 ps(corresponding to a compression ratio of>5)and a low emittance of<1 mm mrad can be readily obtained for a 500 pC electron pulse.This feasible ballistic bunching scheme will facilitate the implementation of an ultrashort pulse mode inverse Compton scattering X-ray source on most existing S-band photo-injectors.
基金supported by the National Natural Science Foundation of China(Grant Nos.11305037,11347114,and 11374054)the Natural Science Foundation of Fujian Province,China(Grant No.2013J01012)
文摘We investigate the effect of the dipole–dipole interaction(DDI) on the photon statistics with two atoms trapped in an optical cavity driven by a laser field and subjected to cooperative emission. By means of the quantum trajectory analysis and the second-order correlation functions, we show that the photon statistics of the cavity transmission can be flexibly modulated by the DDI while the incoming coherent laser selectively excites the atom–cavity system’s nonlinear Jaynes–Cummings ladder of excited states. Finally, we find that the effect of the cooperatively atomic emission can also be revealed by the numerical simulations and can be explained with a simplified picture. The DDI induced nonlinearity gives rise to highly nonclassical photon emission from the cavity that is significant for quantum information processing and quantum communication.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 50802105)
文摘The formation of macrostep during high-temperature phase of barium meta-borate （^-BaB204） single crystal growth has been investigated by both optical in-situ observation system and atomic force microscopy （AFM）. The in- si$u observation results demonstrate that the critical linear size of growing facet exceeding the size that the macrostep generates is significantly anisotropic. The critical linear sizes are around 280 ~m and 620 ~m for {1010} and （T010} planes, respectively. AFM study illustrates that macrostep train with a height of 150 nm^200 nm is one typical morphological feature of the as-grown crystal surface. The riser of each macrostep consists of several straight and parallel sub-steps, indicating the occurrence of step bunching. Additionally, triangular sub-steps with heights of several nanometers on the treads of the macrosteps are found to be another typical feature of surface morphology, which implies a microscopically competitive bunching of sub-steps between various crystallographic orientations.
基金Supported by the National Basic Research Program of China (Grant No. 2006CB921106)the National Natural Science Foundation of China (Grant No. 10874098)the ECIST-FET Project EuroSQUIP, the Swiss SNF, and the NCCR Nanoscience
文摘We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation,a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus,the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.
基金supported by National Natural Science Foundation of China under Grants(11705214,11675174)Youth Innovation Promotion Asso-ciation CAS(2019016)
文摘Purpose The High Energy Photon Source is a fourth-generation synchrotron radiation source being built in China.It is comprised of a storage ring,a full energy booster,a 500-MeV Linac and three transport lines.The pulse charge at the exit of the Linac is required to be up to 7 nC.Both single bunch and three bunches in a beam pulse might be needed according to the studies on instabilities of the booster and the beam dynamic of the main Linac.Methods A bunching system consisting of both sub-harmonic and fundamental frequency structures is designed to meet the requirements.To obtain high transmission efficiency and control the emittance growth,multi-objective genetic algorithm is introduced to optimize the electromagnetic parameters of these structures.Results In this paper,detailed optimization process and the final results are presented.The total transmission efficiency of the bunching system is 97%,and the transmission efficiency of the main bunch is 95%.The normalized RMS emittance of 8.5 nC included beam charge is smaller than 60 mm mrad.Conclusions The design of the bunching system is presented,and both the pulse charge and the beam emittance well meet the design requirement.
基金Supported by National Natural Science Foundation of China(11275222)
文摘Generally, a standard bunching system is composed by an SW pre-buncher, a TW buncher and a standard accelerating section. However, there is one way to simplify the whole system to some extent by using the hybrid buncher, which is a combined structure of the SW pre-buncher and the TW buncher. Here the beam dynamics studies on an S-band bunching system with the hybrid buncher is presented, and simulation results show that similar beam performance can be obtained at the linac exit by using this kind of bunching system rather than the standard one. In the meantime, the structure design of the hybrid buncher is also described. Furthermore, the standard accelerating section can also be integrated with the hybrid buncher, which can further simplify the usual bunching system and lower the construction cost.
基金Supported by National Natural Sciences Foundation of China(11205152,11375199)Fundamental Research Funds for the Central Universities(WK2310000042)Major State Basic Research Development Program of China(2011CB808301)
文摘We present the analytical and simulated results of our study of the influence of the acceleration gradient in the velocity bunching process, which is a bunch compression scheme that uses a travelling wave accelerating structure as a compressor. Our study shows that the bunch compression application with low acceleration gradient is more tolerant to phase jitter and more successful in obtaining a compressed electron beam with symmetrical longitudinal distribution and low energy spread. We also present a transverse emittance compensation scheme to compensate the emittance growth caused by the increase of the space charge force in the compressing process, which is easy to adjust for different compression factors.
基金sponsored by State Key Laboratory of Intelligent Green Vehicle and Mobility under Project No.KFY2421,China.
文摘Bus bunching has been a persistent issue in urban bus system since it first appeared,and it remains a challenge not fully resolved.This phenomenon may reduce the operational efficiency of the urban bus system,which is detrimental to the operation of fast-paced public transport in cities.Fortunately,extensive research has been undertaken in the long development and optimization of the urban bus system,and many solutions have emerged so far.The purpose of this paper is to summarize the existing solutions and serve as a guide for subsequent research in this area.Upon careful examination of current findings,it is found that,based on the different optimization objects,existing solutions to the bus bunching problem can be divided into five directions,i.e.,operational strategy improvement,traffic control improvement,driver driving rules improvement,passenger habit improvement,and others.While numerous solutions to bus bunching are available,there remains a gap in research exploring the integrated application of methods from diverse directions.Furthermore,with the development of autonomous driving,it is expected that the use of modular autonomous vehicles could be the most potential solution to the issue of bus bunching in the future.
基金Supported by National Natural Science Foundation of China(11127507,11375097,11375098)National Basic Research Program of China(973 Program)(2011CB808302)
文摘Increasing the peak brightness is beneficial to various applications of the Thomson scattering X-ray source. A higher peak brightness of the scattered X-ray pulse demands a shorter scattering electron beam realized by beam compression in the electron beam-line. In this article, we study the possibility of compressing the electron beam in a typical S-band normal conducting photo-injector via ballistic bunching, through just adding a short RF linac section right behind the RF gun, so as to improve the peak brightness of the scattered x-ray pulse. Numerical optimization by ASTRA demonstrates that the peak current can increase from 50 A to 300 A for a 500 pC, 10 ps FWHM electron pulse, while normalized transverse RMS emittance and RMS energy spread increases very little. Correspondingly, the peak brightness of the Thomson scattering X-ray source is estimated to increase about three times.
基金Supported by National Natural Science Foundation of China(10675116)Major State Basic Research Development Programme of China(2011CB808301)
文摘In PASER （particle acceleration by stimulated emission of radiation）, in the presence of an active medium incorporated in a Penning trap, moving electrons can become bunched, and as they get enough energy, they escape the trap forming an optical injector. These bunched electrons can enter the next PASER section filled with the same active medium to be accelerated. In this paper, electron dynamics in the presence of a gas mixture active medium incorporated in a Penning trap is analyzed by developing an idealized 1D model. We evaluate the energy exchange occurring as the train of electrons traverses into the next PASER section. The results show that the oscillating electrons can be bunched at the resonant frequency of the active medium. The influence of the trapped time and population inversion are analyzed, showing that the longer the electrons are trapped, the more energy from the medium the accelerated electrons get, and with the increase of population inversion, the decelerated electrons are virtually unchanged but the accelerated electrons more than double their peak energy values. The simulation results show that the gas active medium needs a lower population inversion to bunch the electrons compared to a solid active medium, so the experimental conditions can easily be achieved.
基金supported by the National Natural Science Foundation of China(No.12075306)the Natural Science Foundation of Shanghai(No.22ZR1470900)Key Research Programs in Frontier Science(No.ZDBS-LY-SLH006)。
文摘This study entailed the development of a high-gradient modulation of microbunching for traditional radiation frequency accelerators using a minimized system driven by a relativistic Laguerre–Gaussian(LG)laser in three-dimensional particlein-cell(PIC)simulations.It was observed that the LG laser could compress the transverse dimension of the beam to within a 0.7μm radius(divergence≈4.3 mrad),which is considerably lower than the case tuned by a Gaussian laser.In addition,the electron beam could be efficiently modulated to a high degree of bunching effect(>0.5)within~21 fs(~7μm)in the longitudinal direction.Such a high-gradient density modulation driven by an LG laser for pre-bunched,low-divergence,and stable electron beams provides a potential technology for the system minimization of X-ray free-electron lasers(XFELs)and ultrashort-scale(attosecond)electron diffraction research.
基金The National Basic Research Program of China(973 Program)(No.2012CB725402)the National Natural Science Foundation of China(No.50978057)Program of Scientific Innovation Research of College Graduate in Jiangsu Province(No.CXLX12_0108)
文摘The common phenomenon of uneven headway in bus service is explored based on the automatic vehicle location （AVL） data of Route 2 in Yichun City of Jiangxi province from 6：00 to 9：00 in the morning. The headway regularity of two stages 6： 00--7：00 and 7： 00--9：00 is comparatively analyzed, and it is found that both the traffic conditions and the passenger demand affect headway regularity. A bus arrival model, which assumes that the dwell time of a bus is linear in headway, is built to probe the effect of scheduled headway, and the model is simulated by Matlab. The simulation results reveal that the departure intervals and fluctuations affect headway regularity. Longer intervals and less fluctuation mean higher regularity of headway. And, the fluctuation has a more obvious influence on headway regularity than the interval. Controlling the fluctuations of scheduled headway can effectively raise the regularity of headway and improve the level of public transport service.
文摘The use of organic fertilizers is less expensive and advantageous for both the development of the plant and the sanitation of the environment. This is why this investigation aims to promote the ash from emptying of oil mill boilers as a source of organic fertilization in the production of palm bunches. To do this, different doses of oil mill boiler emptying ash were tested on oil palms in production. The results showed that the oil palms responded favorably regardless of the dose of oil mill boiler emptying ash. Thus, the comparison of the different doses Tv1 (1 kg), Tv2 (1.5 kg), Tv3 (2 kg), Tv4 (3 kg), Tv5 (4 kg), Tv6 (5 kg) and Tv7 (7 kg) showed that the high doses led to an increase in the weight of the bunches. Better still, the Tv6 treatment at a dose of 5 kg/tree proved to be optimal for good production of palm bunches with a gain of 73.9% compared to the treatment without oil mill boiler emptying ash (absolute control).
基金supported by the National Key Research and Development Program(No.2022YFC2402300)。
文摘Industrial linear accelerators often contain many bunches when their pulse widths are extended to microseconds.As they typically operate at low electron energies and high currents,the interactions among bunches cannot be neglected.In this study,an algorithm is introduced for calculating the space charge force of a train with infinite bunches.By utilizing the ring charge model and the particle-in-cell(PIC)method and combining analytical and numerical methods,the proposed algorithm efficiently calculates the space charge force of infinite bunches,enabling the accurate design of accelerator parameters and a comprehensive understanding of the space charge force.This is a significant improvement on existing simulation software such as ASTRA and PARMELA that can only handle a single bunch or a small number of bunches.The PIC algorithm is validated in long drift space transport by comparing it with existing models,such as the infinite-bunch,ASTRA single-bunch,and PARMELA several-bunch algorithms.The space charge force calculation results for the external acceleration field are also verified.The reliability of the proposed algorithm provides a foundation for the design and optimization of industrial accelerators.
基金funded by the Regular Fundamental Research Grant of the Directorate of Research,Technology,and Community Service,Ministry of Education,Culture,Research,and Technology,Republic of Indonesia No.093/E5/PG.02.00.PL/2024Research Institution of Universitas Sumatera Utara No.1/UN5.4.10S/PPM/KPDRTPM/2024supported by the project“Development,Exploitation Properties and Application of Eco-Friendly Wood-Based Composites from Alternative Lignocellulosic Raw Materials”,Project No.HN C--1290/19.10.2023,carried out at the University of Forestry,Sofia,Bulgaria.
文摘The utilisation of sugar palm bunches-charcoal briquettes(SPB-CB)represents a significant advancement in biomass energy.This study aimed to analyse the properties of charcoal briquettes produced from SPB(Arenga longipes).The experiment involved categorising the dimensions of charcoal powder into three specific particle sizes:20-40 mesh,40-60 mesh,and particles that could pass through a 60-mesh screen.The charcoal powder will be combined with tapioca as a binding agent at three specific concentrations:11%,13%,and 15%.The research findings indicate that the samples underwent 60 mesh passes achieved the maximum briquette density,with an average value of 0.58 g/cm^(3).The highest attainable compressive strength sample value was 27.52 kgf/cm^(2),which was attained by employing 60 mesh size and 15%adhesive concentration.The calorimetric investigation showed that SPB-charcoal had the highest calorific value of 25.88 MJ/kg,while the SPB-CB had a little lower caloric value of 24.64 MJ/kg.The ash content and volatile matter values showed that the briquettes with the lowest ash content had values of 10.49%and 32.65%,respectively.Furthermore,the carbon fixation values varied between 16.65%and 52.36%.Thermogravimetric analysis indicates that charcoal derived from SPB exhibits superior thermal characteristics compared to charcoal briquettes.However,thermal properties of SPB charcoal do not show significant differences when compared to charcoal briquettes that have been processed with a mesh size of 20-40 and include 11%adhesive.According to this research,it may be inferred that charcoal briquettes made from sugar palm bunches meet the requirements specified in SNI 01-6235-2000.
基金support from the NSRF via the Program Management Unit for Human Resources&Institutional Development,Research,and Innovation(No.B05F650022),as well as from Chiang Mai University.
文摘A super-radiant terahertz free-electron laser(THz-FEL)light source was developed for the first time in Thailand and Southeast Asia at the PBP-CMU Electron Linac Laboratory(PCELL)of Chiang Mai University.This radiation source requires relatively ultrashort electron bunches to produce intense coherent THz pulses.Three electron bunch compression processes are utilized in the PCELL accelerator system comprising pre-bunch compression in an alpha magnet,velocity bunching in a radio-frequency(RF)linear accelerator(linac),and magnetic bunch compression in a 180°acromat system.Electron bunch compression in the magnetic compressor system poses considerable challenges,which are addressed through the use of three quadrupole doublets.The strengths of the quadrupole fields significantly influence the rotation of the beam line longitudinal phase space distribution along the bunch compressor.Start-to-end beam dynamics simulations using the ASTRA code were performed to optimize the electron beam properties for generating super-radiant THz-FEL radiation.The operational parameters considered in the simulations comprise the alpha magnet gradient,linac RF phase,and quadrupole field strengths.The optimization results show that 10-16MeV femtosecond electron bunches with a low energy spread(~0.2%),small normalized emittance(~15πmm·mrad),and high peak current(165-247A)can be produced by the PCELL accelerator system at the optimal parameters.A THz-FEL with sub-microjoule pulse energies can thus be obtained at the optimized electron beam parameters.The physical and conceptual design of the THz-FEL beamline were completed based on the beam dynamics simulation results.The construction and installation of this beamline are currently underway and expected to be completed by mid-2024.The commissioning of the beamline will then commence.
