Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating grad... more Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating gradient than room temperature RFQ. We plan to design a 162.5MHz SC RFQ to accelerate the 30 mA proton beams from 35 keV to 2.5 MeV, which will be used as a neutron source for BNCT and neutron imaging project. At an inter-vane voltage of 180kV, the beam dynamics design was carried out with acceptable peak surface electric field, high transmission efficiency, and relatively short cavity length.
Most of existing high-current RFQs in the world encounter the degrade of beam transmission or uns... more Most of existing high-current RFQs in the world encounter the degrade of beam transmission or unstable operation, even RF ramping can’t go up to nominal design voltage after several years or long time beam commissioning. One of the main reasons is that the irradiation damage to electrode surface, caused by beam losses, influences RF performance of RFQ cavity. This is especially serious for high-current RFQ. By simulation and irradiation experiments, proton irradiation damage to copper target has been studied. The simulation results showed that normally incident proton beams with input energy lower than 1 MeV damage the copper surface in the range of one skin depth at 162.5 MHz, which indicated that almost all the lost beams with small incident angles impact RF performance of RFQ cavity. By the irradiation experiments, the damage within 60 nm depth from surface was proved to have a greater impact on surface finish. The conclusion is that low energy beam losses also need to be kept as...
A powerful heavy ion injector SSC-linac is under constructing at IMP in Lanzhou. The continuous w... more A powerful heavy ion injector SSC-linac is under constructing at IMP in Lanzhou. The continuous wave (CW) 4-rod RFQ operating at 53.667 MHz has been developed as the low beam energy injector linac. The 40 Ar 8+ ion beam extracted from the ECR ion source was used for the RFQ commissioning. The particle energy 142.8 keV/u and the 198 ePA beam current were measured at the exit of RFQ with the 94% transmission. In this paper, the recent R&D progress of the SSCLINAC including the development of key components and the beam commissioning results are presented.
The Compact Laser Plasma Accelerator (CLAPA) has been built recently at Peking University, which ... more The Compact Laser Plasma Accelerator (CLAPA) has been built recently at Peking University, which composed of a 200TW laser acceleration platform and a beam line system. Proton with energy spread of <1%, up to 10 pC charge and different energies below 10 MeV have been produced and transported to the irradiation platform. Emittance is a critical parameter for beam transportation. The preliminary emittance measurement has been performed for CLAPA’s proton beams using the quadrupole scan technique (QST). In the experiment, the focal spot size of the proton beam was changed by scanning the current of a quadrupole triplet magnet. The result shows that the normalized emittance is smaller than 0.01 mm·mrad for 5 MeV laser driven protons, which is on the same level of the previously reported work [1].
The Beijing isotope separation online (BISOL) facility will be used to study the new physics and ... more The Beijing isotope separation online (BISOL) facility will be used to study the new physics and technologies at the limit of the nuclear stability. The post accelerator for BISOL facility aims to accelerate radioactive beams to 150 MeV/u. As an injector for the downstream superconducting linac, a 4-vane RFQ operating at 81.25 MHz is needed to accelerate high-charge-state ions such as 132Sn22+ from 3 keV/u to 500 keV/u in CW mode. We have compared two kinds of beam dynamics of BISOL RFQ with and without a Multi-Harmonic Buncher (MHB) bunching the continuous wave beam up-stream of the RFQ. The results indicate that it is possible to keep transverse emittance growth within tolerable limits while the longitudinal emittance is much smaller than the design without an external buncher. The acceleration of multi-charge beams simultaneously in the RFQ is also discussed in this paper. INTRODUCTION Peking University (PKU) and China Institute of Atomic Energy (CIAE) are jointly proposing to co...
Plasma window is one of the windowless vacuum sealing techniques which can separate high pressure... more Plasma window is one of the windowless vacuum sealing techniques which can separate high pressure cavity from a vacuum condition by plasma. In this paper the theory of establishing a high pressure gap by plasma window is concluded into three main effects. These are viscosity flow effect, thermal block effect and cooling effect. Further, a preliminary model is constructed by combining laminar flow and joule-heating equations to verify the theory. The simulation results of plasma window are also presented in the paper.
A proton–proton collider at center-of-mass energy of more than 70 TeV is the second stage of the ... more A proton–proton collider at center-of-mass energy of more than 70 TeV is the second stage of the CEPC-SPPC program. As proposed, the SPPC injector chain will use a 1.2 GeV p-Linac and three synchrotrons of 10 GeV p-RCS, 180 GeV MSS and 2.1 TeV SS. Peking University is responsible for the preliminary conceptual design of the room temperature part of SPPC p-Linac. This paper is focusing on the beam dynamics studies performed with respect to the 325 MHz RFQ. As the first accelerator structure after the ion source and the front-end of the whole SPPC, RFQ plays an important role in the beam initial transverse focusing and longitudinal bunching. Based on the New Four Section Procedure strategy, as well as the matched and Equipartitioning design method, a 3 MeV RFQ designed by Parmteq code will be introduced. The cavity length of RFQ is 3.6 m and the transmission efficiency is 98%. In this design scheme, the 40 mA proton beam from the 50 keV ion source is accelerated to 3 MeV in 3.8 m leng...
Cavities are widely spread inside the polyetherimide which is a super engineering plastic. As the... more Cavities are widely spread inside the polyetherimide which is a super engineering plastic. As the main source of partial discharge, they may lead to the tree-like breakdown and insulation failure of material. With the 30 MHz ultrasonic scanning microscope, the cavities of single sample and batch samples are identified and characterized. Small cavities (1-5 pixels) occupy more than 95% of all cavities for a typical sample. The mean area, total area and cavity number of each batch are closer to normal distribution. By the improved experimental system, the breakdown characteristic and insulation life of samples are tested. The cavities scanning from the front and back sides increased by 31% and 41% respectively after breakdown. The normalized insulation life is reduced by nearly 36 times as the mean cavity area increased by only 2 times.
The Peking University neutron imaging facility (PKUNIFTY), an RFQ-based neutron source, aims at d... more 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 201.5 MHz RFQ of PKUNIFTY, which accelerates 35 mA of D + from 50 keV to 2.0 MeV at 10% duty factor, is performed. The averaged D + beam will be about 3 mA. The source will deliver a fast neutron yield of 2.5×10 12 n/s via the deuteron-beryllium reaction, which is about 10 times higher than the current status.
The beam dynamic design of a 325 MHz Radio Frequency Quadrupole (RFQ) is presented in this paper.... more The beam dynamic design of a 325 MHz Radio Frequency Quadrupole (RFQ) is presented in this paper. This 4-vane RFQ will accelerate pulsed proton beam from 30 keV to 3 MeV with repetition frequency of 1 MHz. A 1 MHz chopper and a 5 MHz buncher are arranged in the Low-Energy-Beam-Transport (LEBT) to produce the injected beam. The beam length at the RFQ entrance is about 3 ns, and the energy-spread is about 10%. The code of PARMTEQM is used to simulate RFQ structure. The design should realize high transmission for very high intensity beam meanwhile low emittance growth and relatively short length should be kept.
Coded source imaging (CSI) is a possible method to solve the contradiction between neutron flux a... more Coded source imaging (CSI) is a possible method to solve the contradiction between neutron flux and L/D ratio. Peking University neutron imaging facility (PKUNIFTY) is a RFQ accelerator based facility. The CSI experiments were carried out on PKUNFTY to test the benefits that this technique might bring. The CSI technique gets more restricts on the moderator, especially the neutron distribution in the inner collimator, where the coded mask sampling the source. The effect caused by the non-uniformity of neutron distribution on the mask plane was investigated. The slope type non-uniformity should less than 20% to keep the artifact in the reconstructed image insignificant. The PKUNIFTY moderator was modified according to the above limit. The preliminary experiments shown the moderator design for coded source imaging is acceptable.
Several hundred keV fast neutron radiography (HKFNR) can be a complementary technique to common t... more Several hundred keV fast neutron radiography (HKFNR) can be a complementary technique to common thermal neutron radiography (TNR) and several MeV fast neutron radiography (MFNR). We tested HKFNR on a 4.5 MV Van de Graaff accelerator, and the experimental results show that the spatial resolution of this technique is better than MFNR and close to TNR. Several hundred keV fast neutrons can penetrate some thermal neutron absorbers such as Cd, and it is feasible to investigate its use on some materials which are transparent to cold/thermal neutrons, such as aluminum, using this technique.
Boron Neutron Capture Therapy (BNCT) [1, 2], promises a bright prospect for future cancer treatme... more Boron Neutron Capture Therapy (BNCT) [1, 2], promises a bright prospect for future cancer treatment, in terms of effectiveness, safety and less expanse. The PKU RFQ group proposes an RFQ based neutron source for BNCT. A unique beam dynamics design of 162.5 MHz BNCTRFQ, which accelerates 20 mA of H+ from 30 keV to 2.5 MeV in CW operation, has been performed in this study. The Proton current will be about 20 mA. The source will deliver a neutron yield of 1.76 × 10 / / in the , reaction. Detailed 3D electromagnetic (EM) simulations of all components, including crosssection, tuners, pi-rods, and cut-backs, of the resonant structure are performed. The design of a coaxial type coupler is developed. Two identical RF couplers will deliver approximately 153 kW CW RF power to the RFQ cavity. RF property optimizations of the RF structures are performed with the utilization of the CST MICROWAVE STUDIO [3].
A compact remote control system with the SIMATIC S7-300 PLC is being designed for Peking Universi... more A compact remote control system with the SIMATIC S7-300 PLC is being designed for Peking University Neutron Imaging FaciliTY (PKUNIFTY). PKUNIFTY consists of a 2.45GHz ECR Deuteron ion source, LEBT, a 201.5MHz RFQ cavity, HEBT and Be target. Now PLC control system for ECR ion source and LEBT has been completed and tested. This paper will present the structure of the control system, the HMI with useful data recording system, and some measures took to improve the system safety.
High-intensity deuteron accelerators run the risk of deuteron-deuteron interactions leading to ac... more High-intensity deuteron accelerators run the risk of deuteron-deuteron interactions leading to activation. For this reason, in the commissioning phase, a molecular hydrogen ion (H²⁺) beam is often used as a model for the deuteron beam without the radiation risk. However, composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Such interactions affect the beam dynamics results, and may lead to production of secondary particles, which in high-intensity beams may cause damage to the accelerator and reduce the quality of the beam. In order to understand these effects, we have modified the IMPACT-T particle tracking code to include particle interactions during the tracking simulation through a high-intensity continuous-wave (CW) radio-frequency quadrupole (RFQ). This code is also designed to be easily extensible to other interactions, such as collisions or break-up of heavier ions. Preliminary results and...
A new 162.5 MHz RFQ has been built for a joint 973 project between Peking University (PKU) and In... more A new 162.5 MHz RFQ has been built for a joint 973 project between Peking University (PKU) and Institute of Modern Physics (IMP). It is designed to deliver 50-mA deuteron beams to 1 MeV in CW mode, with an inter-voltage of 60 kV and a length of 1.809 m. Due to its window-type structure, the RFQ has compact cross-section, sufficient mode separation and high specific shunt impedance. It consists of two segments fabricated and installed at IMP. The assembling error of the cavity is less than 0.05 mm. The RF measurements show good electrical properties of the resonant cavity with a measured unloaded quality factor equal to 96.4% of the simulated value. After tuning, we obtained the nominal frequency and field unbalance within 1.0%. Preparation of high-power test of this RFQ is underway. This paper will cover the fabrication details and RF measurements, as well as the progress of high-power test.
As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking Uni... more As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking University only achieved to separate 28.8 kPa from 360 Pa experimentally with 50 A direct current and 2.5 kW power. Based on our 10 mm diameter plasma window, we have proposed a cascaded plasma window to achieve the isolation of atmosphere and high vacuum. In this paper, a numerical 2D FLUENT-based magneto-hydrodynamic simulation on 10 mm diameter cascaded plasma window was developed. The gas inlet, arc creation and plasma expansion segments are all contained in this model. A set of parameters including pressure, temperature, velocity and current distribution were obtained and analysed. In our first simulation, the isolation of 100 kPa and 50 Pa pressure has been realised, and some interesting phenomena occurred.
Comparing with conventional accelerator, laser plasma accelerator can generate high energy ions i... more Comparing with conventional accelerator, laser plasma accelerator can generate high energy ions in a greatly reduced scale due to its TV/m acceleration gradient. A compact laser plasma accelerator (CLAPA) has been built at Institute of Heavy Ion physics in Peking University, based on which application researches like biological irradiation, astrophysics simulation etc. will be carried on. A beamline system with multi group of quadrupoles and analyzing magnet for laser accelerated ions is proposed here. Since laser accelerated ion beams have broad energy spectrum and large angular divergence, the parameters (beam waist position in Y direction, beam line layout, drift distance, magnet angles etc.) of the beamline system is carefully designed and optimised to obtain a radially symmetric proton distribution at the irradiation platform. Requirement of energy selection and differences in focusing or defocusing in application system have great influence on evolution of proton distribution....
The project of SSC-LINAC RFQ has important progresses in the past year. The machine has been move... more The project of SSC-LINAC RFQ has important progresses in the past year. The machine has been moved to the Institute of Modern Physics in the first season of 2013. The cavity measurement including tests of RF performance and field distribution is carried out again in the laboratory. The Q0 is 6440, and the unflatness of the electric field in longitudinal is ±2.5%. The results demonstrated a good agreement with simulation. The RF and beam commissioning of the RFQ has been carried out in the first half of 2014. The duty factor rose from 5% to CW gradually. By now, the cavity has been operated with 35 kW on CW mode. The measurement of the bremsstrahlung spectrum reveals that the 35 kW power is needed to generate the 70 kV inter-vane voltage. The beam transmission efficiency and energy spread has been obtained in beam commissioning by accelerating O and Ar beams. The efficiency of Ar is as high as 94%, and the output energy is 142.78 keV/u. All the processes and results of the experiment...
Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating grad... more Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating gradient than room temperature RFQ. We plan to design a 162.5MHz SC RFQ to accelerate the 30 mA proton beams from 35 keV to 2.5 MeV, which will be used as a neutron source for BNCT and neutron imaging project. At an inter-vane voltage of 180kV, the beam dynamics design was carried out with acceptable peak surface electric field, high transmission efficiency, and relatively short cavity length.
Most of existing high-current RFQs in the world encounter the degrade of beam transmission or uns... more Most of existing high-current RFQs in the world encounter the degrade of beam transmission or unstable operation, even RF ramping can’t go up to nominal design voltage after several years or long time beam commissioning. One of the main reasons is that the irradiation damage to electrode surface, caused by beam losses, influences RF performance of RFQ cavity. This is especially serious for high-current RFQ. By simulation and irradiation experiments, proton irradiation damage to copper target has been studied. The simulation results showed that normally incident proton beams with input energy lower than 1 MeV damage the copper surface in the range of one skin depth at 162.5 MHz, which indicated that almost all the lost beams with small incident angles impact RF performance of RFQ cavity. By the irradiation experiments, the damage within 60 nm depth from surface was proved to have a greater impact on surface finish. The conclusion is that low energy beam losses also need to be kept as...
A powerful heavy ion injector SSC-linac is under constructing at IMP in Lanzhou. The continuous w... more A powerful heavy ion injector SSC-linac is under constructing at IMP in Lanzhou. The continuous wave (CW) 4-rod RFQ operating at 53.667 MHz has been developed as the low beam energy injector linac. The 40 Ar 8+ ion beam extracted from the ECR ion source was used for the RFQ commissioning. The particle energy 142.8 keV/u and the 198 ePA beam current were measured at the exit of RFQ with the 94% transmission. In this paper, the recent R&D progress of the SSCLINAC including the development of key components and the beam commissioning results are presented.
The Compact Laser Plasma Accelerator (CLAPA) has been built recently at Peking University, which ... more The Compact Laser Plasma Accelerator (CLAPA) has been built recently at Peking University, which composed of a 200TW laser acceleration platform and a beam line system. Proton with energy spread of <1%, up to 10 pC charge and different energies below 10 MeV have been produced and transported to the irradiation platform. Emittance is a critical parameter for beam transportation. The preliminary emittance measurement has been performed for CLAPA’s proton beams using the quadrupole scan technique (QST). In the experiment, the focal spot size of the proton beam was changed by scanning the current of a quadrupole triplet magnet. The result shows that the normalized emittance is smaller than 0.01 mm·mrad for 5 MeV laser driven protons, which is on the same level of the previously reported work [1].
The Beijing isotope separation online (BISOL) facility will be used to study the new physics and ... more The Beijing isotope separation online (BISOL) facility will be used to study the new physics and technologies at the limit of the nuclear stability. The post accelerator for BISOL facility aims to accelerate radioactive beams to 150 MeV/u. As an injector for the downstream superconducting linac, a 4-vane RFQ operating at 81.25 MHz is needed to accelerate high-charge-state ions such as 132Sn22+ from 3 keV/u to 500 keV/u in CW mode. We have compared two kinds of beam dynamics of BISOL RFQ with and without a Multi-Harmonic Buncher (MHB) bunching the continuous wave beam up-stream of the RFQ. The results indicate that it is possible to keep transverse emittance growth within tolerable limits while the longitudinal emittance is much smaller than the design without an external buncher. The acceleration of multi-charge beams simultaneously in the RFQ is also discussed in this paper. INTRODUCTION Peking University (PKU) and China Institute of Atomic Energy (CIAE) are jointly proposing to co...
Plasma window is one of the windowless vacuum sealing techniques which can separate high pressure... more Plasma window is one of the windowless vacuum sealing techniques which can separate high pressure cavity from a vacuum condition by plasma. In this paper the theory of establishing a high pressure gap by plasma window is concluded into three main effects. These are viscosity flow effect, thermal block effect and cooling effect. Further, a preliminary model is constructed by combining laminar flow and joule-heating equations to verify the theory. The simulation results of plasma window are also presented in the paper.
A proton–proton collider at center-of-mass energy of more than 70 TeV is the second stage of the ... more A proton–proton collider at center-of-mass energy of more than 70 TeV is the second stage of the CEPC-SPPC program. As proposed, the SPPC injector chain will use a 1.2 GeV p-Linac and three synchrotrons of 10 GeV p-RCS, 180 GeV MSS and 2.1 TeV SS. Peking University is responsible for the preliminary conceptual design of the room temperature part of SPPC p-Linac. This paper is focusing on the beam dynamics studies performed with respect to the 325 MHz RFQ. As the first accelerator structure after the ion source and the front-end of the whole SPPC, RFQ plays an important role in the beam initial transverse focusing and longitudinal bunching. Based on the New Four Section Procedure strategy, as well as the matched and Equipartitioning design method, a 3 MeV RFQ designed by Parmteq code will be introduced. The cavity length of RFQ is 3.6 m and the transmission efficiency is 98%. In this design scheme, the 40 mA proton beam from the 50 keV ion source is accelerated to 3 MeV in 3.8 m leng...
Cavities are widely spread inside the polyetherimide which is a super engineering plastic. As the... more Cavities are widely spread inside the polyetherimide which is a super engineering plastic. As the main source of partial discharge, they may lead to the tree-like breakdown and insulation failure of material. With the 30 MHz ultrasonic scanning microscope, the cavities of single sample and batch samples are identified and characterized. Small cavities (1-5 pixels) occupy more than 95% of all cavities for a typical sample. The mean area, total area and cavity number of each batch are closer to normal distribution. By the improved experimental system, the breakdown characteristic and insulation life of samples are tested. The cavities scanning from the front and back sides increased by 31% and 41% respectively after breakdown. The normalized insulation life is reduced by nearly 36 times as the mean cavity area increased by only 2 times.
The Peking University neutron imaging facility (PKUNIFTY), an RFQ-based neutron source, aims at d... more 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 201.5 MHz RFQ of PKUNIFTY, which accelerates 35 mA of D + from 50 keV to 2.0 MeV at 10% duty factor, is performed. The averaged D + beam will be about 3 mA. The source will deliver a fast neutron yield of 2.5×10 12 n/s via the deuteron-beryllium reaction, which is about 10 times higher than the current status.
The beam dynamic design of a 325 MHz Radio Frequency Quadrupole (RFQ) is presented in this paper.... more The beam dynamic design of a 325 MHz Radio Frequency Quadrupole (RFQ) is presented in this paper. This 4-vane RFQ will accelerate pulsed proton beam from 30 keV to 3 MeV with repetition frequency of 1 MHz. A 1 MHz chopper and a 5 MHz buncher are arranged in the Low-Energy-Beam-Transport (LEBT) to produce the injected beam. The beam length at the RFQ entrance is about 3 ns, and the energy-spread is about 10%. The code of PARMTEQM is used to simulate RFQ structure. The design should realize high transmission for very high intensity beam meanwhile low emittance growth and relatively short length should be kept.
Coded source imaging (CSI) is a possible method to solve the contradiction between neutron flux a... more Coded source imaging (CSI) is a possible method to solve the contradiction between neutron flux and L/D ratio. Peking University neutron imaging facility (PKUNIFTY) is a RFQ accelerator based facility. The CSI experiments were carried out on PKUNFTY to test the benefits that this technique might bring. The CSI technique gets more restricts on the moderator, especially the neutron distribution in the inner collimator, where the coded mask sampling the source. The effect caused by the non-uniformity of neutron distribution on the mask plane was investigated. The slope type non-uniformity should less than 20% to keep the artifact in the reconstructed image insignificant. The PKUNIFTY moderator was modified according to the above limit. The preliminary experiments shown the moderator design for coded source imaging is acceptable.
Several hundred keV fast neutron radiography (HKFNR) can be a complementary technique to common t... more Several hundred keV fast neutron radiography (HKFNR) can be a complementary technique to common thermal neutron radiography (TNR) and several MeV fast neutron radiography (MFNR). We tested HKFNR on a 4.5 MV Van de Graaff accelerator, and the experimental results show that the spatial resolution of this technique is better than MFNR and close to TNR. Several hundred keV fast neutrons can penetrate some thermal neutron absorbers such as Cd, and it is feasible to investigate its use on some materials which are transparent to cold/thermal neutrons, such as aluminum, using this technique.
Boron Neutron Capture Therapy (BNCT) [1, 2], promises a bright prospect for future cancer treatme... more Boron Neutron Capture Therapy (BNCT) [1, 2], promises a bright prospect for future cancer treatment, in terms of effectiveness, safety and less expanse. The PKU RFQ group proposes an RFQ based neutron source for BNCT. A unique beam dynamics design of 162.5 MHz BNCTRFQ, which accelerates 20 mA of H+ from 30 keV to 2.5 MeV in CW operation, has been performed in this study. The Proton current will be about 20 mA. The source will deliver a neutron yield of 1.76 × 10 / / in the , reaction. Detailed 3D electromagnetic (EM) simulations of all components, including crosssection, tuners, pi-rods, and cut-backs, of the resonant structure are performed. The design of a coaxial type coupler is developed. Two identical RF couplers will deliver approximately 153 kW CW RF power to the RFQ cavity. RF property optimizations of the RF structures are performed with the utilization of the CST MICROWAVE STUDIO [3].
A compact remote control system with the SIMATIC S7-300 PLC is being designed for Peking Universi... more A compact remote control system with the SIMATIC S7-300 PLC is being designed for Peking University Neutron Imaging FaciliTY (PKUNIFTY). PKUNIFTY consists of a 2.45GHz ECR Deuteron ion source, LEBT, a 201.5MHz RFQ cavity, HEBT and Be target. Now PLC control system for ECR ion source and LEBT has been completed and tested. This paper will present the structure of the control system, the HMI with useful data recording system, and some measures took to improve the system safety.
High-intensity deuteron accelerators run the risk of deuteron-deuteron interactions leading to ac... more High-intensity deuteron accelerators run the risk of deuteron-deuteron interactions leading to activation. For this reason, in the commissioning phase, a molecular hydrogen ion (H²⁺) beam is often used as a model for the deuteron beam without the radiation risk. However, composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Such interactions affect the beam dynamics results, and may lead to production of secondary particles, which in high-intensity beams may cause damage to the accelerator and reduce the quality of the beam. In order to understand these effects, we have modified the IMPACT-T particle tracking code to include particle interactions during the tracking simulation through a high-intensity continuous-wave (CW) radio-frequency quadrupole (RFQ). This code is also designed to be easily extensible to other interactions, such as collisions or break-up of heavier ions. Preliminary results and...
A new 162.5 MHz RFQ has been built for a joint 973 project between Peking University (PKU) and In... more A new 162.5 MHz RFQ has been built for a joint 973 project between Peking University (PKU) and Institute of Modern Physics (IMP). It is designed to deliver 50-mA deuteron beams to 1 MeV in CW mode, with an inter-voltage of 60 kV and a length of 1.809 m. Due to its window-type structure, the RFQ has compact cross-section, sufficient mode separation and high specific shunt impedance. It consists of two segments fabricated and installed at IMP. The assembling error of the cavity is less than 0.05 mm. The RF measurements show good electrical properties of the resonant cavity with a measured unloaded quality factor equal to 96.4% of the simulated value. After tuning, we obtained the nominal frequency and field unbalance within 1.0%. Preparation of high-power test of this RFQ is underway. This paper will cover the fabrication details and RF measurements, as well as the progress of high-power test.
As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking Uni... more As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking University only achieved to separate 28.8 kPa from 360 Pa experimentally with 50 A direct current and 2.5 kW power. Based on our 10 mm diameter plasma window, we have proposed a cascaded plasma window to achieve the isolation of atmosphere and high vacuum. In this paper, a numerical 2D FLUENT-based magneto-hydrodynamic simulation on 10 mm diameter cascaded plasma window was developed. The gas inlet, arc creation and plasma expansion segments are all contained in this model. A set of parameters including pressure, temperature, velocity and current distribution were obtained and analysed. In our first simulation, the isolation of 100 kPa and 50 Pa pressure has been realised, and some interesting phenomena occurred.
Comparing with conventional accelerator, laser plasma accelerator can generate high energy ions i... more Comparing with conventional accelerator, laser plasma accelerator can generate high energy ions in a greatly reduced scale due to its TV/m acceleration gradient. A compact laser plasma accelerator (CLAPA) has been built at Institute of Heavy Ion physics in Peking University, based on which application researches like biological irradiation, astrophysics simulation etc. will be carried on. A beamline system with multi group of quadrupoles and analyzing magnet for laser accelerated ions is proposed here. Since laser accelerated ion beams have broad energy spectrum and large angular divergence, the parameters (beam waist position in Y direction, beam line layout, drift distance, magnet angles etc.) of the beamline system is carefully designed and optimised to obtain a radially symmetric proton distribution at the irradiation platform. Requirement of energy selection and differences in focusing or defocusing in application system have great influence on evolution of proton distribution....
The project of SSC-LINAC RFQ has important progresses in the past year. The machine has been move... more The project of SSC-LINAC RFQ has important progresses in the past year. The machine has been moved to the Institute of Modern Physics in the first season of 2013. The cavity measurement including tests of RF performance and field distribution is carried out again in the laboratory. The Q0 is 6440, and the unflatness of the electric field in longitudinal is ±2.5%. The results demonstrated a good agreement with simulation. The RF and beam commissioning of the RFQ has been carried out in the first half of 2014. The duty factor rose from 5% to CW gradually. By now, the cavity has been operated with 35 kW on CW mode. The measurement of the bremsstrahlung spectrum reveals that the 35 kW power is needed to generate the 70 kV inter-vane voltage. The beam transmission efficiency and energy spread has been obtained in beam commissioning by accelerating O and Ar beams. The efficiency of Ar is as high as 94%, and the output energy is 142.78 keV/u. All the processes and results of the experiment...
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