In recent years,due to the scarcity of domestic radioisotopes,the Chinese government has strongly supported the development of dedicated radioisotope production facilities.This paper presents conceptual design simulat...In recent years,due to the scarcity of domestic radioisotopes,the Chinese government has strongly supported the development of dedicated radioisotope production facilities.This paper presents conceptual design simulations of an 11 MeV,50μA,H^(-) compact superconducting cyclotron for radioisotope production.This paper focuses primarily on four aspects:magnet system design,central region configuration,beam dynamics analysis,and extraction system design.This paper outlines the cyclotron's primary parameters and key steps in the development process.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
A new 973 project was proposed by Peking University and Institute of Modern Physics of Chinese Academy of Sciences recently. The project requires a 50mA, 162.5MHz, cw mode radio frequency quadrupole （FtFO,） to accel...A new 973 project was proposed by Peking University and Institute of Modern Physics of Chinese Academy of Sciences recently. The project requires a 50mA, 162.5MHz, cw mode radio frequency quadrupole （FtFO,） to accelerate the D＋ to 1 MeV. In a high-current linear accelerator, the strong space charge effect causes the growth of envelope and emittanee along with heavy beam losses. In the beam dynamics design of this RFQ, beam envelope mismatching is discussed and a matching dynamics method is proposed to minimize the envelope and emittance growth. The influence of limiting current on the beam transmission is discussed and used in the optimization of transverse and longitudinal parameters. After the optimization, the beam transmission efficiency reaches higher than 98%.展开更多
The Peking University neutron imaging facility (PKUNIFTY), an RFQ-based neutron source, aims at developing industrial applications. During the past 3 y operation, some problems have appeared, such as RF sparking for t...The Peking University neutron imaging facility (PKUNIFTY), an RFQ-based neutron source, aims at developing industrial applications. During the past 3 y operation, some problems have appeared, such as RF sparking for the RFQ high power operation, full power level instability of RF transmitter, and the misalignment of RFQ electrodes assembling and deformation. The PKUNIFTY upgrade endeavors to adopt a modest inter-voltage beam dynamics design. The new beam dynamics design of 201.5MHz RFQ of PKUNIFTY, which accelerates 35mA of D+ from 50 keV to 2.0MeV at 10% duty factor, is performed. The averaged D+ beam will be about 3 mA. The source will deliver a fast neutron yield of 2.5x10(12) n/s via the deuteron-beryllium reaction, which is about 10 times higher than the current status.展开更多
This paper introduces the proposed insertion device(ID)scheme for the Shanghai Synchrotron Radiation Facility Upgrade.Based on this scheme,the influences of the ID radiation on the intra-beam scattering emittance and ...This paper introduces the proposed insertion device(ID)scheme for the Shanghai Synchrotron Radiation Facility Upgrade.Based on this scheme,the influences of the ID radiation on the intra-beam scattering emittance and energy spread were evaluated.Optical distortion caused by the IDs was comprehensively examined and compensated using both local and global corrections.Subsequently,a frequency map analysis method was used to identify potentially dangerous resonance lines.In addition,the dynamic aperture,energy acceptance,and Touschek lifetime were calculated after considering high-order magnetic field errors to ensure that the ID effect did not affect the operation of the storage ring.展开更多
Background A full-energy LINAC is under development at Wuhan Advanced Light Source(WALS)to provide beams for the 1.5 GeV storage ring proposed as a fourth-generation synchrotron radiation light source and a future fre...Background A full-energy LINAC is under development at Wuhan Advanced Light Source(WALS)to provide beams for the 1.5 GeV storage ring proposed as a fourth-generation synchrotron radiation light source and a future free electron laser(FEL)facility.The LINAC starts from a photoinjector that is able to produce electron beams with low emittance(<1 mm·mrad),small relative energy spread(<0.5%),and high bunch charge(~1 nC).Purpose and methods To minimize the output emittance and RMS bunch length for the purpose of improving the photoinjector brightness,the influence of different laser pulse profiles on the slice emittance is investigated,and the beam dynamics simulation is performed with non-dominated sorting genetic algorithm-II(NSGA-II)combining with ASTRA code to find the optimal solution at a bunch charge of 1 nC.Results and conclusion In this paper,the beam dynamics optimization of the photoinjector is presented in detail;the simulation results imply that the laser pulse profile with 1σtruncated Gaussian distribution in transverse and flat-top-like temporal distribution is beneficial to the improvement of beam brightness of the photoinjector,which shows an output emittance of 0.63 mm·mrad in the case of intrinsic thermal emittance of 0.43 mm·mrad.展开更多
Purpose HIRFL-CSR(Heavy Ion Research Facility in Lanzhou,Cooler Storage Ring)is a heavy-ion accelerator facility at IMP(Institute of Modern Physics,Chinese Academy of Sciences).Due to the diverse physics research requ...Purpose HIRFL-CSR(Heavy Ion Research Facility in Lanzhou,Cooler Storage Ring)is a heavy-ion accelerator facility at IMP(Institute of Modern Physics,Chinese Academy of Sciences).Due to the diverse physics research requirements,including higher beam intensity and quality,in recent years,a new high-level accelerator control system,PACS(Physics-oriented Accelerator Control System),was designed and deployed in the HIRFL-CSR facility.However,as more and more complex beam commissioning needs the cooperation of multiple beam dynamics modules,which are developed independently by different accelerator physicists,it is necessary to design a framework to integrate any new beam dynamics modules and guarantee cooperation between new and existing beam dynamics modules.Method The integrated beam dynamics framework consists of the unified dynamics interface,the general dynamics scheduler and the multi-user queue.The unified dynamics interface ensures the independence of each beam dynamics module and isolates data from each beam dynamics module.The general dynamics scheduler forms beam dynamics chains from different beam dynamics modules,simplifying beam commissioning.The multi-user queue ensures that all users can access all beam dynamics modules simultaneously.Results Various beam dynamics modules are embedded in the framework,and these modules can collaborate with each other.This significantly improves the accuracy of beam commissioning and the efficiency of software development for accelerator physicists.Conclusion With the integrated beam dynamics framework,the efficiency of beam commissioning and the performance of HIRFL-CSR are significantly improved,which shows the framework is quite powerful for developing controls of complicated beam dynamics.HIAF(High Intensity heavy-ion Accelerator Facility)and EicC(Electron-Ion Collider in China)will employ many new beam dynamics schemes and innovative technologies to reach higher intensity or higher luminosity.The framework will play a vital role in building integrated,smart control systems and pushing performance boundaries of these next-generation facilities.展开更多
We designed a 100 MeV/100 kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the basis of subcritical assembly. Beam dynamics studies have been conducted to reach the design r...We designed a 100 MeV/100 kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the basis of subcritical assembly. Beam dynamics studies have been conducted to reach the design requirements （E=100 MeV, P=100 kW, dE/E 〈1% for 99% particles）. In this paper, we will present the progress of the design and the dynamic simulation results. For high intensity and long beam pulse linear accelerators, the BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at a low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced downstream of the 1st accelerating section; the unwanted particles will be collimated there.展开更多
The energy recovery linac test facility （ERL-TF）, which is a compact ERL-FEL （free electron laser） two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of ...The energy recovery linac test facility （ERL-TF）, which is a compact ERL-FEL （free electron laser） two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector that started with a photocathode direct-current gun has been designed. In this paper, optimization of the injector beam dynamics in low-charge operation mode is performed with iterative scans using Impact-T. In addition, the dependencies between the optimized beam quality and the initial offset at cathode and element parameters are, investigated. The tolerance of alignment and rotation errors is also analyzed.展开更多
For the accelerator driven subcritical system （ADS） main linac in China, two families of superconducting elliptical radio frequency （RF） cavities will be used to accelerate the proton beam from 180 MeV to 1.5 GeV....For the accelerator driven subcritical system （ADS） main linac in China, two families of superconducting elliptical radio frequency （RF） cavities will be used to accelerate the proton beam from 180 MeV to 1.5 GeV. When the proton beam traverses in the RF cavity, the excited parasitic modes, like high order modes （HOMs） and same order modes （SOMs）, may drive the beam to become unstable and increase the cryogenic load, thus putting a limitation on the normal operation of the accelerator. In this paper, by using a numerical code SMD based on the ROOT environment, the effects of longitudinal parasitic modes on the beam dynamics for the ADS driving linac in China have been investigated systematically, while parasitic modes which increase cryogenic loss have not been included in this paper. Some conclusions concerning the beam energy ranging from 180 MeV to 1.5 GeV have been obtained.展开更多
In the SSRF Phase-II beamline project, a superconducting wiggler（SW） will be installed in the electron storage ring. It may greatly impact on the beam dynamics due to the very high magnetic field. The emittance grow...In the SSRF Phase-II beamline project, a superconducting wiggler（SW） will be installed in the electron storage ring. It may greatly impact on the beam dynamics due to the very high magnetic field. The emittance growth becomes a major problem, even after correction of the beam optics. A local achromatic lattice is studied, in order to combat the emittance growth and keep the performance of the SSRF storage ring as high as possible. Other effects of the SW are also simulated and optimized, including the beta beating, the tune shift, the dynamic aperture, and the field error effects.展开更多
During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), which started on Nov. 12, 2006 and Oct. 24, 2007, respectively, we got the luminosity one t...During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), which started on Nov. 12, 2006 and Oct. 24, 2007, respectively, we got the luminosity one tenth of its design value, provided beams to synchrotron radiation users for about 4 months, and studied beam dynamics as well. In this paper, some beam dynamics studies on the storage rings and their preliminary results are given.展开更多
The energy recovery linac test facility （ERL-TF）, a compact ERL-FEL （free electron laser） two-purpose machine, has been proposed at the Institute of High Energy Physics, Beijing. As one important component of the ...The energy recovery linac test facility （ERL-TF）, a compact ERL-FEL （free electron laser） two-purpose machine, has been proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector was designed and preliminarily optimized. In this paper an evolutionary genetic method, non-dominated sorting genetic algorithm II, is applied to optimize the injector beam dynamics, especially in the high-charge operation mode. Study shows that using an incident laser with rms transverse size of 1-1.2 ram, the normalized emittance of the electron beam can be kept below 1 mm.mrad at the end of the injector. This work, together with the previous optimization of the low-charge operation mode by using the iterative scan method, provides guidance and confidence for future construction and commissioning of the ERL-TF injector.展开更多
For the application of high intensity continuous wave （CW） proton beam acceleration, a new superconducting accelerating structure for extremely low β protons working in TE210 mode has been proposed at Peking Univer...For the application of high intensity continuous wave （CW） proton beam acceleration, a new superconducting accelerating structure for extremely low β protons working in TE210 mode has been proposed at Peking University. The cavity consists of eight electrodes and eight accelerating gaps. The cavity＇s longitudinal length is 368.5 mm, and its transverse dimension is 416 mm. The RF frequency is 162.5 MHz, and the designed proton input energy is 200 keV. A peak field optimization has been performed for the lower surface field, The accelerating gaps are adjusted by phase sweeping based on KONUS beam dynamics. The first four gaps are operated at negative synchronous RF phase to provide longitudinal focusing. The subsequent gaps are 0° sections which can minimize the transverse defocusing effect. Solenoids are placed outside the cavity to provide transverse focusing. Numerical calculation shows that the transverse defocusing of the KONUS phase is about three times smaller than that of the conventional negative synchronous RF phase. The beam dynamics of a 10 mA CW proton beam is simulated by the TraceWin code. The simulation results show that the beam＇s transverse size is under effective control, while the increase in the longitudinal direction is slightly large. Both the TraceWin simulation and the numerical calculation show that the cavity has a relatively high effective accelerating gradient of 2.6 MV/m. On the whole, our results show that this new accelerating structure may be a possible candidate for superconducting operation at such a low energy range.展开更多
Beam dynamics and RF design have been performed of a new type trapezoidal IH-RFQ operating at 104 MHz for acceleration of 14C+ in the framework of RFQ based 14C AMS facility at Peking University. Low energy spread RFQ...Beam dynamics and RF design have been performed of a new type trapezoidal IH-RFQ operating at 104 MHz for acceleration of 14C+ in the framework of RFQ based 14C AMS facility at Peking University. Low energy spread RFQ beam dynamics design was approached by the method of internal discrete bunching. 14C+ will be accelerated from 40 keV to 500 keV with the length of about 1.1 m. The designed transmission efficiency is better than 95% and the energy spread is as low as 0.6%. Combining the beam dynamics design, a trapezoidal IH-RFQ structure was proposed, which can be cooled more easily and has better mechanical performance than traditional RFQ. Electromagnetic field distribution was simulated by using CST Microwave Studio (MWS). The specific shunt impedance and the quality factor were optimized primarily.展开更多
KONUS beam dynamics design of uranium whose current is 5.0 emA, is accelerated from injection DTL with LORASR code is presented. The 238U34＋ beam, energy of 0.35 MeV/u to output energy of 1.30 MeV/u by IH-DTL operate...KONUS beam dynamics design of uranium whose current is 5.0 emA, is accelerated from injection DTL with LORASR code is presented. The 238U34＋ beam, energy of 0.35 MeV/u to output energy of 1.30 MeV/u by IH-DTL operated at 81.25 MHz in HIAF project at IMP of CAS. It achieves a transmission efficiency of 94.95% with a cavity length of 267.8 cm. The optimization aims are the reduction of emittance growth, beam loss and project costs. Because of the requirements of CW mode operation, the designed average acceleration gradient is about 2.48 MV/m. The maximum axial field is 10.2 MV/m, meanwhile the Kilpatrick breakdown field is 10.56 MV/m at 81.25 MHz.展开更多
A 30 mA drift tube linac （DTL） accelerator has been designed using SUPERFISH code in the energy range of 3-55 MeV in the framework of the Turkish Accelerator Center （TAC） project. Optimization criteria in cavity d...A 30 mA drift tube linac （DTL） accelerator has been designed using SUPERFISH code in the energy range of 3-55 MeV in the framework of the Turkish Accelerator Center （TAC） project. Optimization criteria in cavity design are effective shunt impedance （ZTT）, transit-time factor and electrical breakdown limit. In geometrical optimization we have aimed to increase the energy gain in each RF gap of the DTL cells by maximizing the effective shunt impedance （ZTT） and the transit-time factor. Beam dynamics studies of the DTL accelerator have been performed using beam dynamics simulation codes of PATH and PARMILA. The results of both codes have been compared. In the beam dynamical studies, the rms values of beam emittance have been taken into account and a low emittance growth in both x and y directions has been attempted.展开更多
The ADS（accelerator driven subcritical system） project was proposed by the Chinese Academy of Sciences.The initial proton beams delivered from an electron cyclotron resonance ion source can be effectively accelerate...The ADS（accelerator driven subcritical system） project was proposed by the Chinese Academy of Sciences.The initial proton beams delivered from an electron cyclotron resonance ion source can be effectively accelerated by 162.5 MHz 4.2 m long room temperature radio-frequency-quadrupoles（RFQ） operating in CW mode.To test the feasibility of this physical design,a new Fortran code for RFQ beam dynamics study,which is space charge dominated,was developed.This program is based on Particle-In-Cell（PIC） technique in the time domain.Using the RFQ structure designed for the CADS project,the beam dynamics behavior is performed.The well-known simulation code TRACK is used for benchmarks.The results given by these two codes show good agreements.Numerical techniques as well as the results of beam dynamics studies are presented in this paper.展开更多
Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation（ANCF）. The int...Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation（ANCF）. The internal force of the elasto-plastic spatial thin beam element is derived under the assumption that the plastic strain of the beam element depends only on its longitudinal deformation.A new body-fixed local coordinate system is introduced into the spatial thin beam element of ANCF for efficient contact detection in the contact dynamics simulation. The linear isotropic hardening constitutive law is used to describe the elasto-plastic deformation of beam material, and the classical return mapping algorithm is adopted to evaluate the plastic strains. A multi-zone contact approach of thin beams previously proposed by the authors is also introduced to detect the multiple contact zones of beams accurately, and the penalty method is used to compute the normal contact force of thin beams in contact. Four numerical examples are given to demonstrate the applicability and effectiveness of the proposed elasto-plastic spatial thin beam element of ANCF for flexible multibody system dynamics.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
文摘In recent years,due to the scarcity of domestic radioisotopes,the Chinese government has strongly supported the development of dedicated radioisotope production facilities.This paper presents conceptual design simulations of an 11 MeV,50μA,H^(-) compact superconducting cyclotron for radioisotope production.This paper focuses primarily on four aspects:magnet system design,central region configuration,beam dynamics analysis,and extraction system design.This paper outlines the cyclotron's primary parameters and key steps in the development process.
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.
基金Supported by the National Basic Research Program of China under Grant No 2014CB845503
文摘A new 973 project was proposed by Peking University and Institute of Modern Physics of Chinese Academy of Sciences recently. The project requires a 50mA, 162.5MHz, cw mode radio frequency quadrupole （FtFO,） to accelerate the D＋ to 1 MeV. In a high-current linear accelerator, the strong space charge effect causes the growth of envelope and emittanee along with heavy beam losses. In the beam dynamics design of this RFQ, beam envelope mismatching is discussed and a matching dynamics method is proposed to minimize the envelope and emittance growth. The influence of limiting current on the beam transmission is discussed and used in the optimization of transverse and longitudinal parameters. After the optimization, the beam transmission efficiency reaches higher than 98%.
基金Supported by the National Basic Research Program of China under Grant No 2014CB845503
文摘The Peking University neutron imaging facility (PKUNIFTY), an RFQ-based neutron source, aims at developing industrial applications. During the past 3 y operation, some problems have appeared, such as RF sparking for the RFQ high power operation, full power level instability of RF transmitter, and the misalignment of RFQ electrodes assembling and deformation. The PKUNIFTY upgrade endeavors to adopt a modest inter-voltage beam dynamics design. The new beam dynamics design of 201.5MHz RFQ of PKUNIFTY, which accelerates 35mA of D+ from 50 keV to 2.0MeV at 10% duty factor, is performed. The averaged D+ beam will be about 3 mA. The source will deliver a fast neutron yield of 2.5x10(12) n/s via the deuteron-beryllium reaction, which is about 10 times higher than the current status.
文摘This paper introduces the proposed insertion device(ID)scheme for the Shanghai Synchrotron Radiation Facility Upgrade.Based on this scheme,the influences of the ID radiation on the intra-beam scattering emittance and energy spread were evaluated.Optical distortion caused by the IDs was comprehensively examined and compensated using both local and global corrections.Subsequently,a frequency map analysis method was used to identify potentially dangerous resonance lines.In addition,the dynamic aperture,energy acceptance,and Touschek lifetime were calculated after considering high-order magnetic field errors to ensure that the ID effect did not affect the operation of the storage ring.
基金supported by Science and Technology Major Project of Hubei Province in China(2021AFB001).
文摘Background A full-energy LINAC is under development at Wuhan Advanced Light Source(WALS)to provide beams for the 1.5 GeV storage ring proposed as a fourth-generation synchrotron radiation light source and a future free electron laser(FEL)facility.The LINAC starts from a photoinjector that is able to produce electron beams with low emittance(<1 mm·mrad),small relative energy spread(<0.5%),and high bunch charge(~1 nC).Purpose and methods To minimize the output emittance and RMS bunch length for the purpose of improving the photoinjector brightness,the influence of different laser pulse profiles on the slice emittance is investigated,and the beam dynamics simulation is performed with non-dominated sorting genetic algorithm-II(NSGA-II)combining with ASTRA code to find the optimal solution at a bunch charge of 1 nC.Results and conclusion In this paper,the beam dynamics optimization of the photoinjector is presented in detail;the simulation results imply that the laser pulse profile with 1σtruncated Gaussian distribution in transverse and flat-top-like temporal distribution is beneficial to the improvement of beam brightness of the photoinjector,which shows an output emittance of 0.63 mm·mrad in the case of intrinsic thermal emittance of 0.43 mm·mrad.
基金support from the National Key R&D Program of China(Grant No.2019YFA0405400)the support from Young Elite Scientists Sponsorship Program by CAST(Grant No.2023QNRC001)the support from the National Natural Science Foundation of China(Grant No.12105332).
文摘Purpose HIRFL-CSR(Heavy Ion Research Facility in Lanzhou,Cooler Storage Ring)is a heavy-ion accelerator facility at IMP(Institute of Modern Physics,Chinese Academy of Sciences).Due to the diverse physics research requirements,including higher beam intensity and quality,in recent years,a new high-level accelerator control system,PACS(Physics-oriented Accelerator Control System),was designed and deployed in the HIRFL-CSR facility.However,as more and more complex beam commissioning needs the cooperation of multiple beam dynamics modules,which are developed independently by different accelerator physicists,it is necessary to design a framework to integrate any new beam dynamics modules and guarantee cooperation between new and existing beam dynamics modules.Method The integrated beam dynamics framework consists of the unified dynamics interface,the general dynamics scheduler and the multi-user queue.The unified dynamics interface ensures the independence of each beam dynamics module and isolates data from each beam dynamics module.The general dynamics scheduler forms beam dynamics chains from different beam dynamics modules,simplifying beam commissioning.The multi-user queue ensures that all users can access all beam dynamics modules simultaneously.Results Various beam dynamics modules are embedded in the framework,and these modules can collaborate with each other.This significantly improves the accuracy of beam commissioning and the efficiency of software development for accelerator physicists.Conclusion With the integrated beam dynamics framework,the efficiency of beam commissioning and the performance of HIRFL-CSR are significantly improved,which shows the framework is quite powerful for developing controls of complicated beam dynamics.HIAF(High Intensity heavy-ion Accelerator Facility)and EicC(Electron-Ion Collider in China)will employ many new beam dynamics schemes and innovative technologies to reach higher intensity or higher luminosity.The framework will play a vital role in building integrated,smart control systems and pushing performance boundaries of these next-generation facilities.
文摘We designed a 100 MeV/100 kW electron linear accelerator for NSC KIPT, which will be used to drive a neutron source on the basis of subcritical assembly. Beam dynamics studies have been conducted to reach the design requirements （E=100 MeV, P=100 kW, dE/E 〈1% for 99% particles）. In this paper, we will present the progress of the design and the dynamic simulation results. For high intensity and long beam pulse linear accelerators, the BBU effect is one big issue; special care has been taken in the accelerating structure design. To satisfy the energy spread requirement at the linac exit, the particles with large energy difference from the synchronous particle should be eliminated at a low energy stage to ease the design of the collimation system and radiation shielding. A dispersion free chicane with 4 bending magnets is introduced downstream of the 1st accelerating section; the unwanted particles will be collimated there.
文摘The energy recovery linac test facility （ERL-TF）, which is a compact ERL-FEL （free electron laser） two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector that started with a photocathode direct-current gun has been designed. In this paper, optimization of the injector beam dynamics in low-charge operation mode is performed with iterative scans using Impact-T. In addition, the dependencies between the optimized beam quality and the initial offset at cathode and element parameters are, investigated. The tolerance of alignment and rotation errors is also analyzed.
文摘For the accelerator driven subcritical system （ADS） main linac in China, two families of superconducting elliptical radio frequency （RF） cavities will be used to accelerate the proton beam from 180 MeV to 1.5 GeV. When the proton beam traverses in the RF cavity, the excited parasitic modes, like high order modes （HOMs） and same order modes （SOMs）, may drive the beam to become unstable and increase the cryogenic load, thus putting a limitation on the normal operation of the accelerator. In this paper, by using a numerical code SMD based on the ROOT environment, the effects of longitudinal parasitic modes on the beam dynamics for the ADS driving linac in China have been investigated systematically, while parasitic modes which increase cryogenic loss have not been included in this paper. Some conclusions concerning the beam energy ranging from 180 MeV to 1.5 GeV have been obtained.
基金Supported by National Natural Science Foundation of China(11105214)
文摘In the SSRF Phase-II beamline project, a superconducting wiggler（SW） will be installed in the electron storage ring. It may greatly impact on the beam dynamics due to the very high magnetic field. The emittance growth becomes a major problem, even after correction of the beam optics. A local achromatic lattice is studied, in order to combat the emittance growth and keep the performance of the SSRF storage ring as high as possible. Other effects of the SW are also simulated and optimized, including the beta beating, the tune shift, the dynamic aperture, and the field error effects.
基金Supported by National Natural Sciences Foundation of China (10725525)
文摘During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider (BEPCⅡ), which started on Nov. 12, 2006 and Oct. 24, 2007, respectively, we got the luminosity one tenth of its design value, provided beams to synchrotron radiation users for about 4 months, and studied beam dynamics as well. In this paper, some beam dynamics studies on the storage rings and their preliminary results are given.
文摘The energy recovery linac test facility （ERL-TF）, a compact ERL-FEL （free electron laser） two-purpose machine, has been proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector was designed and preliminarily optimized. In this paper an evolutionary genetic method, non-dominated sorting genetic algorithm II, is applied to optimize the injector beam dynamics, especially in the high-charge operation mode. Study shows that using an incident laser with rms transverse size of 1-1.2 ram, the normalized emittance of the electron beam can be kept below 1 mm.mrad at the end of the injector. This work, together with the previous optimization of the low-charge operation mode by using the iterative scan method, provides guidance and confidence for future construction and commissioning of the ERL-TF injector.
基金Supported by Major Research Plan of National Natural Science Foundation of China(91026001)
文摘For the application of high intensity continuous wave （CW） proton beam acceleration, a new superconducting accelerating structure for extremely low β protons working in TE210 mode has been proposed at Peking University. The cavity consists of eight electrodes and eight accelerating gaps. The cavity＇s longitudinal length is 368.5 mm, and its transverse dimension is 416 mm. The RF frequency is 162.5 MHz, and the designed proton input energy is 200 keV. A peak field optimization has been performed for the lower surface field, The accelerating gaps are adjusted by phase sweeping based on KONUS beam dynamics. The first four gaps are operated at negative synchronous RF phase to provide longitudinal focusing. The subsequent gaps are 0° sections which can minimize the transverse defocusing effect. Solenoids are placed outside the cavity to provide transverse focusing. Numerical calculation shows that the transverse defocusing of the KONUS phase is about three times smaller than that of the conventional negative synchronous RF phase. The beam dynamics of a 10 mA CW proton beam is simulated by the TraceWin code. The simulation results show that the beam＇s transverse size is under effective control, while the increase in the longitudinal direction is slightly large. Both the TraceWin simulation and the numerical calculation show that the cavity has a relatively high effective accelerating gradient of 2.6 MV/m. On the whole, our results show that this new accelerating structure may be a possible candidate for superconducting operation at such a low energy range.
文摘Beam dynamics and RF design have been performed of a new type trapezoidal IH-RFQ operating at 104 MHz for acceleration of 14C+ in the framework of RFQ based 14C AMS facility at Peking University. Low energy spread RFQ beam dynamics design was approached by the method of internal discrete bunching. 14C+ will be accelerated from 40 keV to 500 keV with the length of about 1.1 m. The designed transmission efficiency is better than 95% and the energy spread is as low as 0.6%. Combining the beam dynamics design, a trapezoidal IH-RFQ structure was proposed, which can be cooled more easily and has better mechanical performance than traditional RFQ. Electromagnetic field distribution was simulated by using CST Microwave Studio (MWS). The specific shunt impedance and the quality factor were optimized primarily.
文摘KONUS beam dynamics design of uranium whose current is 5.0 emA, is accelerated from injection DTL with LORASR code is presented. The 238U34＋ beam, energy of 0.35 MeV/u to output energy of 1.30 MeV/u by IH-DTL operated at 81.25 MHz in HIAF project at IMP of CAS. It achieves a transmission efficiency of 94.95% with a cavity length of 267.8 cm. The optimization aims are the reduction of emittance growth, beam loss and project costs. Because of the requirements of CW mode operation, the designed average acceleration gradient is about 2.48 MV/m. The maximum axial field is 10.2 MV/m, meanwhile the Kilpatrick breakdown field is 10.56 MV/m at 81.25 MHz.
基金Supported by Turkish State Planning Organization (DPT) (DPT-2006K120470)
文摘A 30 mA drift tube linac （DTL） accelerator has been designed using SUPERFISH code in the energy range of 3-55 MeV in the framework of the Turkish Accelerator Center （TAC） project. Optimization criteria in cavity design are effective shunt impedance （ZTT）, transit-time factor and electrical breakdown limit. In geometrical optimization we have aimed to increase the energy gain in each RF gap of the DTL cells by maximizing the effective shunt impedance （ZTT） and the transit-time factor. Beam dynamics studies of the DTL accelerator have been performed using beam dynamics simulation codes of PATH and PARMILA. The results of both codes have been compared. In the beam dynamical studies, the rms values of beam emittance have been taken into account and a low emittance growth in both x and y directions has been attempted.
基金Supported by National Natural Science Foundation of China(11079001,91026001)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA03030100)
文摘The ADS（accelerator driven subcritical system） project was proposed by the Chinese Academy of Sciences.The initial proton beams delivered from an electron cyclotron resonance ion source can be effectively accelerated by 162.5 MHz 4.2 m long room temperature radio-frequency-quadrupoles（RFQ） operating in CW mode.To test the feasibility of this physical design,a new Fortran code for RFQ beam dynamics study,which is space charge dominated,was developed.This program is based on Particle-In-Cell（PIC） technique in the time domain.Using the RFQ structure designed for the CADS project,the beam dynamics behavior is performed.The well-known simulation code TRACK is used for benchmarks.The results given by these two codes show good agreements.Numerical techniques as well as the results of beam dynamics studies are presented in this paper.
基金supported in part by the National Natural Science Foundation of China (Grants 11290151 and 11221202)supported in part by the Beijing Higher Education Young Elite Teacher Project (Grant YETP1201)
文摘Under the frame of multibody dynamics, the contact dynamics of elasto-plastic spatial thin beams is numerically studied by using the spatial thin beam elements of absolute nodal coordinate formulation（ANCF）. The internal force of the elasto-plastic spatial thin beam element is derived under the assumption that the plastic strain of the beam element depends only on its longitudinal deformation.A new body-fixed local coordinate system is introduced into the spatial thin beam element of ANCF for efficient contact detection in the contact dynamics simulation. The linear isotropic hardening constitutive law is used to describe the elasto-plastic deformation of beam material, and the classical return mapping algorithm is adopted to evaluate the plastic strains. A multi-zone contact approach of thin beams previously proposed by the authors is also introduced to detect the multiple contact zones of beams accurately, and the penalty method is used to compute the normal contact force of thin beams in contact. Four numerical examples are given to demonstrate the applicability and effectiveness of the proposed elasto-plastic spatial thin beam element of ANCF for flexible multibody system dynamics.
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.
