My physics research has focused on the design and development of particle accelerators and detectors, including radio-frequency quadrupole accelerators (RFQs), non-scaling fixed-field alternating-gradient accelerators (ns-FFAGs), scintillation detectors, and ion mobility spectrometry detectors (IMS). My research has particularly focused on creating automated computer models to streamline the design process. The applications of the accelerators and detectors I have worked on include cancer therapy treatment using charged particle beams, and protection from explosives and chemical and biological weapons.
I'm a Christian, a physicist, a worshipper, a gamer, a husband and a father. I am English, I have a wife and two young sons, and I enjoy reading books, playing board games, football and computer games, fixing computers and playing musical instruments. Address: 北京市海淀区成府路201号加速器楼220室
Collection of particles from a laser-driven accelerator into a conventional beamline requires car... more Collection of particles from a laser-driven accelerator into a conventional beamline requires careful manipulation of the beam to handle the wide energy spread, large angular divergence and short pulse lengths characteristic of laser-driven acceleration. Accurate simulation of the first few millimetres is crucial in order to optimise the collecting elements such as solenoids or quadrupole magnets. Experiments and simulations both show significant emittance growth in this collection region. We have developed a multi-particle beam dynamics model using impact-t that includes the characteristic exponentially-decaying laser-driven energy spectrum and accurately models the emittance growth due to the large energy spread. In this paper we present theoretical relationships between energy spread and emittance growth, and compare these with the simulated emittance growth. Results show excellent correspondence between theory and simulation. The effect is negligible for lowenergy proton accelerators, but is important for electron accelerators and for proposed high-energy laser-driven proton accelerators.
In order to implement radiotherapy based on a laser accelerator, it is necessary to precisely con... more In order to implement radiotherapy based on a laser accelerator, it is necessary to precisely control the spatial distribution and energy spectrum of the proton beams to meet the requirements of the radiation dose distribution in the three-dimensional biological target. A compact laser plasma accelerator has been built at Peking University, which can reliably generate and transport MeV-energy protons with a specified energy onto the irradiation platform. In this paper, we discuss several technologies for the accurate control of a laser-accelerated proton beam with large divergence angle and broad energy spread, including the determination of the beam source position with micron accuracy, a tuning algorithm for the transport line which we refer to as "matching-image-point two-dimensional energy analysis" to realize accurate energy selection, and the control of beam distribution uniformity. In the prototype experiment with low energy protons and 0.5-Hz irradiation rate, a tailored energy deposition is demonstrated, which shows the potential feasibility of future irradiation based on laser-accelerated proton beams.
A new laser-driven proton therapy facility is being designed by Peking University. The protons wi... more A new laser-driven proton therapy facility is being designed by Peking University. The protons will be produced by laser-plasma interaction, using a 2-PW laser to reach proton energies up to 100 MeV. We hope that the construction of this facility will promote the real-world applications of laser accelerators. Based on the experimental results and design experience of existing devices in Peking University, we propose a beam transmission system which is suitable for the beam produced by laser acceleration, and demonstrate its feasibility through theoretical simulation. It is designed with two transport lines to provide both horizontal and vertical irradiation modes. We have used a locally-achromatic design method with new canted-cosine-theta (CCT) magnets. These two measures allow us to mitigate the negative effects of large energy spread produced by laser-acceleration, and to reduce the overall weight of the vertical beamline. The beamline contains a complete energy selection system, which can reduce the energy spread of the laser-accelerated beam enough to meet the application requirements. The users can select the proton beam energy within the range 40-100 MeV, which is then transmitted through the rest of the beamline. A beam spot with diameter of less than 15 mm and energy spread of less than 5% can be provided at the horizontal and vertical irradiation targets.
High-intensity beams of composite ions are susceptible to particle interactions that do not affec... more High-intensity beams of composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Beam dynamics simulation techniques used in accelerator design do not often include these particle interactions, and so the transmission of the real beam can be significantly different from the design simulations. We have modified the IMPACT-T code to include particle interactions as part of the beam dynamics simulations, including space-charge effects and beam losses. We have carried out validation simulations of interactions in a molecular hydrogen ion beam through an existing high-intensity deuteron RFQ design, as beam commissioning is often carried out using molecular hydrogen beams, to avoid deuteron-deuteron interactions in the accelerator leading to neutron activation. The new code framework successfully models the interactions within the beam, tracks the different source and product ions through the accelerator, and calculates the collective effects such as space charge from all particles together. We also discuss other simulation codes that could be modified to include similar interaction effects, and possible applications to other types of accelerators.
Magnets to be used for the internal quadrupoles of an interdigital H-mode drift tube linear accel... more Magnets to be used for the internal quadrupoles of an interdigital H-mode drift tube linear accelerator (IH-DTL) using KONUS beam dynamics should be both compact in size and high in focusing field gradient. Permanent magnets are an attractive solution, but then the ability to adjust the field strength is lost. We investigated two different solutions to this problem: the first using external adjustable electromagnets; the second using internal adjustable permanent magnets. The first method moves the variability out of the resonant cavity, using adjustable electromagnet quadrupole doublets before entry into the IH-DTL to compensate for the lack of internal variability. We carried out optimization simulations with custom code that ran many instances of the LORASR beam dynamics simulation software, using different values of field strength for the external doublets. By optimizing the magnet settings for different values of input current, we were able to compensate for the space-charge forces involved in accelerating a high-intensity continuous-wave (CW) deuteron beam. Second, we designed some novel adjustable permanent-magnet quadrupoles to be used inside the cavity, which combine the advantages of small cross-section and variable field gradient. This allows much more control over the beam, and even other ion species with differing charge-to-mass ratios can be accommodated within the same accelerator design. We developed two adjustable permanent-magnet designs: one with an electromagnetic component, and the other with two concentric moving rings of Halbach-array quadrupoles.
Physical Review Accelerators and Beams, Dec 22, 2017
A deuteron radio-frequency quadrupole (RFQ) is being built by the RFQ group at Peking University.... more A deuteron radio-frequency quadrupole (RFQ) is being built by the RFQ group at Peking University. It is a very compact high-current RFQ, operating at 162.5 MHz in continuous-wave mode. By optimizing the beam dynamics design, our simulations reached 98% transmission efficiency for acceleration of the 50-mA deuteron beam from 50 keV to 1 MeV, with an intervane voltage of 60 kV and a length of 1.809 m. This RFQ adopts a window-type structure, with low power consumption and sufficient mode separation, with no stabilizing rods required. Its magnetic coupling windows have been optimized by both electromagnetic simulation and the construction of an equivalent circuit model. The empirical equation based on the circuit model provides a new way to evaluate the effect of the window size on the frequency. In addition, an aluminum model of the full-length RFQ has been built and tested, and the results show good agreement with the simulations. During the tuning process, the magnetic coupling effect between quadrants was found to be unique to the window-type RFQ. We also propose a method to estimate the effects of different degrees of electric field unflatness on the beam transmission. For the cooling system design, the results of thermostructural analysis, verified by comparing results from ANSYS and CST, show that the special cooling channels provide a high cooling efficiency around the magnetic coupling windows. The maximal deformation of the structure was approximately 75 μm. The beam-loading effect caused by a high current, and the coupler design, are also discussed.
A novel design framework for Radio Frequency Quadrupoles (RFQs), developed as part of the design ... more A novel design framework for Radio Frequency Quadrupoles (RFQs), developed as part of the design of the FETS RFQ, is presented. This framework integrates several previously disparate steps in the design of RFQs, including the beam dynamics design, mechanical design, electromagnetic, thermal and mechanical modelling and beam dynamics simulations. Each stage of the design process is described in detail, including the various software options and reasons for the final software suite selected. Results are given for each of these steps, describing how each stage affects the overall design process, with an emphasis on the resulting design choices for the FETS RFQ.
The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for ... more The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.
This thesis describes a new design method for a radio frequency quadrupole (RFQ), and its applica... more This thesis describes a new design method for a radio frequency quadrupole (RFQ), and its application to the first stage of acceleration for carbon ions in the PAMELA injector. Radiotherapy is a valuable form of cancer treatment, but current methods using photons or electrons make it difficult to deliver an adequate dose to the tumour without damaging healthy surrounding tissue and organs. Charged hadron beams, such as protons and carbon, deposit most of the dose at the Bragg peak, which can be aligned with the tumour. This allows higher doses to treat the cancer while minimising damage to healthy surrounding tissue and organs. The PAMELA project (part of the BASROC consortium) aims to design new charged particle therapy (CPT) facilities using non-scaling fixed-field alternating-gradient accelerators (ns-FFAGs). This new technology offers significant advantages over both cyclotrons and synchrotrons for CPT. The injector for the PAMELA FFAG accelerator includes separate pre-acceleration chains for protons and carbon ions, culminating in a shared injection system into the first FFAG ring. Carbon ions are pre-accelerated by an RFQ and a short linear accelerator (linac). This thesis details the creation of an integrated system of software packages and custom code, which facilitates the design of RFQ vane tips, utilising computer-aided design (CAD) models for both simulation and manufacture, accurate multi-physics modelling of the electric field and particle tracking simulations. This design process is described, along with benchmark results for the Front- End Test Stand (FETS ) RFQ and application of the code in optimising a new RFQ design for PAMELA.
The PAMELA project aims to design an ns-FFAG accelerator for cancer therapy using protons and car... more The PAMELA project aims to design an ns-FFAG accelerator for cancer therapy using protons and carbon ions [1]. For the injection system for carbon ions, an RFQ is one option for the first stage of acceleration. Our integrated RFQ design process [2] has been further developed using Comsol Multiphysics for electric field modelling. The design parameters for the RFQ are automatically converted to a CAD model using Autodesk Inventor, and the electric field map for this model is simulated in Comsol. Particles are then tracked through this field map using Pulsar Physics' General Particle Tracer (GPT). Our software uses Visual Basic for Applications and MATLAB to automate this process and allow for optimisation of the RFQ design parameters based on particle dynamical considerations. Possible designs for the PAMELA RFQ, including super-conducting and normal-conducting solutions, are presented and discussed, together with results of the field map simulations and particle tracking for these designs.
A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed... more A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. A novel design method, integrating the CAD and electromagnetic design of the RFQ with beam dynamics simulations, is being used to optimise the design of the RFQ. Basic RFQ parameters are produced with the RFQSIM code. A full CAD model of the RFQ vane tips is produced in Autodesk Inventor, based upon these parameters. This model is then imported into a field mapping code to produce a simulation of the electro-static field around the vane tips. This field map is then used to model the beam dynamics within the RFQ using General Particle Tracer (GPT). Previous studies have been carried out using field mapping in CST EM Studio. A more advanced technique using Comsol Multiphysics and Matlab, that more tightly integrates the CAD modelling, field mapping and beam dynamics simulations, is described. Results using this new method are presented and compared to the previous optimisation process using field maps from CST.
For the PAMELA medical non-scaling FFAG, carbon 6+ as well as proton particles are required. The ... more For the PAMELA medical non-scaling FFAG, carbon 6+ as well as proton particles are required. The general injection layout based on a cyclotron for proton and a Linac for carbon is considered. There are two options for pre-accelerating carbon ions for PAMELA, either accelerating carbon with the charge state 4+ from the ion source and stripping after the pre-accelerator or directly accelerating carbon 6+ ions all the way from the ion source. For both options solution has been investigated. Simulations of beam dynamics for both particle species are presented. The resulting schemes based on either the single turn or multiturn injection into the first FFAG ring are discussed.
The PAMELA medical FFAG complex under design in the UK, aims to operate with both proton and carb... more The PAMELA medical FFAG complex under design in the UK, aims to operate with both proton and carbon beams for hadron therapy. Medium energy beam transfer (MEBT) of PAMELA consists of the proton beam line coming out of the injector cyclotron, carbon beam transfer from the independent carbon 6+ injector Linac, switching dipole (SD) when both beam merge and transfer line toward the PAMELA NS-FFAG. The MEBT layout and design, which needs to incorporate the beam chopper for the intensity modulation, are discussed. The careful matching of optical functions between various components in the MEBT and beam dynamics simulations are presented.
The status of the PAMELA (Particle Accelerator for MEdicaL Applications) project to design an acc... more The status of the PAMELA (Particle Accelerator for MEdicaL Applications) project to design an accelerator for proton and light ion therapy using non-scaling Fixed Field Alternating Gradient (ns-FFAG) accelerators is reviewed and discussed.
The PAMELA project aims to design an FFAG accelerator for cancer therapy using protons and carbon... more The PAMELA project aims to design an FFAG accelerator for cancer therapy using protons and carbon ions. For the injection system for carbon ions, an RFQ is one option for the first stage of acceleration. An integrated RFQ design process has been developed using various software packages to take the design parameters for the RFQ, convert this automatically to a CAD model using Autodesk Inventor, and calculate the electric field map for the CAD model using CST EM STUDIO. Particles can then be tracked through this field map using Pulsar Physics' General Particle Tracer (GPT). Our software uses Visual Basic for Applications and MATLAB to automate this process and allow for optimisation of the RFQ design parameters based on particle dynamical considerations. Initial particle tracking simulations based on modifying the field map from the Front-End Test Stand (FETS) RFQ design have determined the best operating frequency for the PAMELA RFQ to be close to 200 MHz and the length approximately 2.3 m. The status of the injector design with an emphasis on the RFQ will be presented, together with the results of the particle tracking.
For the PAMELA project, the injection layout for both protons as well as carbon 6 + ions is discu... more For the PAMELA project, the injection layout for both protons as well as carbon 6 + ions is discussed. The injection system would consist of a 30 MeV cyclotron for protons and a chain of elements for carbon ions such as ECR ion source, bending magnets and focusing solenoids; RFQ, IH/CH structures and a stripping foil. The charge particle simulation for both protons and carbon ions passing through the elements has been carried out via General Particle Tracer (GPT) software.
A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed... more A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. Previous beam dynamics simulations, based on field maps produced with a field approximation code, provide a baseline for the new design. A novel design method is presented that combines the CAD and electromagnetic modelling of both the RFQ tank and the vane modulations with more sophisticated beam dynamics simulations using the General Particle Tracer code (GPT). This approach allows the full inte-gration of the optimisation of the RFQ, based on beam dynamics simulations using a 3D EM-field map of the CAD model, with the design and manufacture of the RFQ vane modulations and RFQ tank. The design process within the Autodesk Inventor CAD software is outlined and details of the EM modelling of the RFQ in CST MicroWave Studio are given. Results of beam dynamics simulations in GPT are presented and compared to previous results with field approximation codes. Finally, possible methods of manufacture based on this design process are discussed.
The PAMELA (Particle Accelerator for MEdicaL Applications) project is to design an accelerator fo... more The PAMELA (Particle Accelerator for MEdicaL Applications) project is to design an accelerator for proton and light ion therapy using non-scaling Fixed Field Alternating Gradient (FFAG) accelerators, as part of the CONFORM project, which is also constructing the EMMA electron model of a non-scaling FFAG at Daresbury. This paper presents an overview of the PAMELA design, and a discussion of the design goals and the principles used to arrive at a preliminary specification of the accelerator.
Spot scanning irradiation is a novel and powerful scheme for particle therapy. The pulsed beam st... more Spot scanning irradiation is a novel and powerful scheme for particle therapy. The pulsed beam structure of FFAG (Fixed Field Alternating Gradient) accelerator is suitable for the scheme. In order to form an uniform dose distribution in a target volume, Beam intensity must be modulated in sync with beam energy modulation. The intensity modulation requires precise intensity control and constrain the bunch intensity of accelerator of pulsed beam structure. In the paper, injection related issue, that is the intensity modulation of FFAG accelerator, is discussed from the view point of spot scanning.
A detector comprising an analytical apparatus for detecting a substance of interest, and a detect... more A detector comprising an analytical apparatus for detecting a substance of interest, and a detector inlet. The detector inlet comprises a flow passage for carrying a flow of fluid, the flow passage comprising a sampling volume,and a sampling inlet adapted to collect samples of the fluid from the sampling volume as the fluid flows past the sampling inlet, and to provide the samples to the analytical apparatus, wherein the flow of fluid carries particulates. The detector inlet also comprises a flow director arranged to vary a spatial distribution of the particulates carried by the fluid to increase a relative proportion of the particulates carried past the sampling inlet along the flow passage without entering the sampling volume.
Collection of particles from a laser-driven accelerator into a conventional beamline requires car... more Collection of particles from a laser-driven accelerator into a conventional beamline requires careful manipulation of the beam to handle the wide energy spread, large angular divergence and short pulse lengths characteristic of laser-driven acceleration. Accurate simulation of the first few millimetres is crucial in order to optimise the collecting elements such as solenoids or quadrupole magnets. Experiments and simulations both show significant emittance growth in this collection region. We have developed a multi-particle beam dynamics model using impact-t that includes the characteristic exponentially-decaying laser-driven energy spectrum and accurately models the emittance growth due to the large energy spread. In this paper we present theoretical relationships between energy spread and emittance growth, and compare these with the simulated emittance growth. Results show excellent correspondence between theory and simulation. The effect is negligible for lowenergy proton accelerators, but is important for electron accelerators and for proposed high-energy laser-driven proton accelerators.
In order to implement radiotherapy based on a laser accelerator, it is necessary to precisely con... more In order to implement radiotherapy based on a laser accelerator, it is necessary to precisely control the spatial distribution and energy spectrum of the proton beams to meet the requirements of the radiation dose distribution in the three-dimensional biological target. A compact laser plasma accelerator has been built at Peking University, which can reliably generate and transport MeV-energy protons with a specified energy onto the irradiation platform. In this paper, we discuss several technologies for the accurate control of a laser-accelerated proton beam with large divergence angle and broad energy spread, including the determination of the beam source position with micron accuracy, a tuning algorithm for the transport line which we refer to as "matching-image-point two-dimensional energy analysis" to realize accurate energy selection, and the control of beam distribution uniformity. In the prototype experiment with low energy protons and 0.5-Hz irradiation rate, a tailored energy deposition is demonstrated, which shows the potential feasibility of future irradiation based on laser-accelerated proton beams.
A new laser-driven proton therapy facility is being designed by Peking University. The protons wi... more A new laser-driven proton therapy facility is being designed by Peking University. The protons will be produced by laser-plasma interaction, using a 2-PW laser to reach proton energies up to 100 MeV. We hope that the construction of this facility will promote the real-world applications of laser accelerators. Based on the experimental results and design experience of existing devices in Peking University, we propose a beam transmission system which is suitable for the beam produced by laser acceleration, and demonstrate its feasibility through theoretical simulation. It is designed with two transport lines to provide both horizontal and vertical irradiation modes. We have used a locally-achromatic design method with new canted-cosine-theta (CCT) magnets. These two measures allow us to mitigate the negative effects of large energy spread produced by laser-acceleration, and to reduce the overall weight of the vertical beamline. The beamline contains a complete energy selection system, which can reduce the energy spread of the laser-accelerated beam enough to meet the application requirements. The users can select the proton beam energy within the range 40-100 MeV, which is then transmitted through the rest of the beamline. A beam spot with diameter of less than 15 mm and energy spread of less than 5% can be provided at the horizontal and vertical irradiation targets.
High-intensity beams of composite ions are susceptible to particle interactions that do not affec... more High-intensity beams of composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Beam dynamics simulation techniques used in accelerator design do not often include these particle interactions, and so the transmission of the real beam can be significantly different from the design simulations. We have modified the IMPACT-T code to include particle interactions as part of the beam dynamics simulations, including space-charge effects and beam losses. We have carried out validation simulations of interactions in a molecular hydrogen ion beam through an existing high-intensity deuteron RFQ design, as beam commissioning is often carried out using molecular hydrogen beams, to avoid deuteron-deuteron interactions in the accelerator leading to neutron activation. The new code framework successfully models the interactions within the beam, tracks the different source and product ions through the accelerator, and calculates the collective effects such as space charge from all particles together. We also discuss other simulation codes that could be modified to include similar interaction effects, and possible applications to other types of accelerators.
Magnets to be used for the internal quadrupoles of an interdigital H-mode drift tube linear accel... more Magnets to be used for the internal quadrupoles of an interdigital H-mode drift tube linear accelerator (IH-DTL) using KONUS beam dynamics should be both compact in size and high in focusing field gradient. Permanent magnets are an attractive solution, but then the ability to adjust the field strength is lost. We investigated two different solutions to this problem: the first using external adjustable electromagnets; the second using internal adjustable permanent magnets. The first method moves the variability out of the resonant cavity, using adjustable electromagnet quadrupole doublets before entry into the IH-DTL to compensate for the lack of internal variability. We carried out optimization simulations with custom code that ran many instances of the LORASR beam dynamics simulation software, using different values of field strength for the external doublets. By optimizing the magnet settings for different values of input current, we were able to compensate for the space-charge forces involved in accelerating a high-intensity continuous-wave (CW) deuteron beam. Second, we designed some novel adjustable permanent-magnet quadrupoles to be used inside the cavity, which combine the advantages of small cross-section and variable field gradient. This allows much more control over the beam, and even other ion species with differing charge-to-mass ratios can be accommodated within the same accelerator design. We developed two adjustable permanent-magnet designs: one with an electromagnetic component, and the other with two concentric moving rings of Halbach-array quadrupoles.
Physical Review Accelerators and Beams, Dec 22, 2017
A deuteron radio-frequency quadrupole (RFQ) is being built by the RFQ group at Peking University.... more A deuteron radio-frequency quadrupole (RFQ) is being built by the RFQ group at Peking University. It is a very compact high-current RFQ, operating at 162.5 MHz in continuous-wave mode. By optimizing the beam dynamics design, our simulations reached 98% transmission efficiency for acceleration of the 50-mA deuteron beam from 50 keV to 1 MeV, with an intervane voltage of 60 kV and a length of 1.809 m. This RFQ adopts a window-type structure, with low power consumption and sufficient mode separation, with no stabilizing rods required. Its magnetic coupling windows have been optimized by both electromagnetic simulation and the construction of an equivalent circuit model. The empirical equation based on the circuit model provides a new way to evaluate the effect of the window size on the frequency. In addition, an aluminum model of the full-length RFQ has been built and tested, and the results show good agreement with the simulations. During the tuning process, the magnetic coupling effect between quadrants was found to be unique to the window-type RFQ. We also propose a method to estimate the effects of different degrees of electric field unflatness on the beam transmission. For the cooling system design, the results of thermostructural analysis, verified by comparing results from ANSYS and CST, show that the special cooling channels provide a high cooling efficiency around the magnetic coupling windows. The maximal deformation of the structure was approximately 75 μm. The beam-loading effect caused by a high current, and the coupler design, are also discussed.
A novel design framework for Radio Frequency Quadrupoles (RFQs), developed as part of the design ... more A novel design framework for Radio Frequency Quadrupoles (RFQs), developed as part of the design of the FETS RFQ, is presented. This framework integrates several previously disparate steps in the design of RFQs, including the beam dynamics design, mechanical design, electromagnetic, thermal and mechanical modelling and beam dynamics simulations. Each stage of the design process is described in detail, including the various software options and reasons for the final software suite selected. Results are given for each of these steps, describing how each stage affects the overall design process, with an emphasis on the resulting design choices for the FETS RFQ.
The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for ... more The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.
This thesis describes a new design method for a radio frequency quadrupole (RFQ), and its applica... more This thesis describes a new design method for a radio frequency quadrupole (RFQ), and its application to the first stage of acceleration for carbon ions in the PAMELA injector. Radiotherapy is a valuable form of cancer treatment, but current methods using photons or electrons make it difficult to deliver an adequate dose to the tumour without damaging healthy surrounding tissue and organs. Charged hadron beams, such as protons and carbon, deposit most of the dose at the Bragg peak, which can be aligned with the tumour. This allows higher doses to treat the cancer while minimising damage to healthy surrounding tissue and organs. The PAMELA project (part of the BASROC consortium) aims to design new charged particle therapy (CPT) facilities using non-scaling fixed-field alternating-gradient accelerators (ns-FFAGs). This new technology offers significant advantages over both cyclotrons and synchrotrons for CPT. The injector for the PAMELA FFAG accelerator includes separate pre-acceleration chains for protons and carbon ions, culminating in a shared injection system into the first FFAG ring. Carbon ions are pre-accelerated by an RFQ and a short linear accelerator (linac). This thesis details the creation of an integrated system of software packages and custom code, which facilitates the design of RFQ vane tips, utilising computer-aided design (CAD) models for both simulation and manufacture, accurate multi-physics modelling of the electric field and particle tracking simulations. This design process is described, along with benchmark results for the Front- End Test Stand (FETS ) RFQ and application of the code in optimising a new RFQ design for PAMELA.
The PAMELA project aims to design an ns-FFAG accelerator for cancer therapy using protons and car... more The PAMELA project aims to design an ns-FFAG accelerator for cancer therapy using protons and carbon ions [1]. For the injection system for carbon ions, an RFQ is one option for the first stage of acceleration. Our integrated RFQ design process [2] has been further developed using Comsol Multiphysics for electric field modelling. The design parameters for the RFQ are automatically converted to a CAD model using Autodesk Inventor, and the electric field map for this model is simulated in Comsol. Particles are then tracked through this field map using Pulsar Physics' General Particle Tracer (GPT). Our software uses Visual Basic for Applications and MATLAB to automate this process and allow for optimisation of the RFQ design parameters based on particle dynamical considerations. Possible designs for the PAMELA RFQ, including super-conducting and normal-conducting solutions, are presented and discussed, together with results of the field map simulations and particle tracking for these designs.
A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed... more A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. A novel design method, integrating the CAD and electromagnetic design of the RFQ with beam dynamics simulations, is being used to optimise the design of the RFQ. Basic RFQ parameters are produced with the RFQSIM code. A full CAD model of the RFQ vane tips is produced in Autodesk Inventor, based upon these parameters. This model is then imported into a field mapping code to produce a simulation of the electro-static field around the vane tips. This field map is then used to model the beam dynamics within the RFQ using General Particle Tracer (GPT). Previous studies have been carried out using field mapping in CST EM Studio. A more advanced technique using Comsol Multiphysics and Matlab, that more tightly integrates the CAD modelling, field mapping and beam dynamics simulations, is described. Results using this new method are presented and compared to the previous optimisation process using field maps from CST.
For the PAMELA medical non-scaling FFAG, carbon 6+ as well as proton particles are required. The ... more For the PAMELA medical non-scaling FFAG, carbon 6+ as well as proton particles are required. The general injection layout based on a cyclotron for proton and a Linac for carbon is considered. There are two options for pre-accelerating carbon ions for PAMELA, either accelerating carbon with the charge state 4+ from the ion source and stripping after the pre-accelerator or directly accelerating carbon 6+ ions all the way from the ion source. For both options solution has been investigated. Simulations of beam dynamics for both particle species are presented. The resulting schemes based on either the single turn or multiturn injection into the first FFAG ring are discussed.
The PAMELA medical FFAG complex under design in the UK, aims to operate with both proton and carb... more The PAMELA medical FFAG complex under design in the UK, aims to operate with both proton and carbon beams for hadron therapy. Medium energy beam transfer (MEBT) of PAMELA consists of the proton beam line coming out of the injector cyclotron, carbon beam transfer from the independent carbon 6+ injector Linac, switching dipole (SD) when both beam merge and transfer line toward the PAMELA NS-FFAG. The MEBT layout and design, which needs to incorporate the beam chopper for the intensity modulation, are discussed. The careful matching of optical functions between various components in the MEBT and beam dynamics simulations are presented.
The status of the PAMELA (Particle Accelerator for MEdicaL Applications) project to design an acc... more The status of the PAMELA (Particle Accelerator for MEdicaL Applications) project to design an accelerator for proton and light ion therapy using non-scaling Fixed Field Alternating Gradient (ns-FFAG) accelerators is reviewed and discussed.
The PAMELA project aims to design an FFAG accelerator for cancer therapy using protons and carbon... more The PAMELA project aims to design an FFAG accelerator for cancer therapy using protons and carbon ions. For the injection system for carbon ions, an RFQ is one option for the first stage of acceleration. An integrated RFQ design process has been developed using various software packages to take the design parameters for the RFQ, convert this automatically to a CAD model using Autodesk Inventor, and calculate the electric field map for the CAD model using CST EM STUDIO. Particles can then be tracked through this field map using Pulsar Physics' General Particle Tracer (GPT). Our software uses Visual Basic for Applications and MATLAB to automate this process and allow for optimisation of the RFQ design parameters based on particle dynamical considerations. Initial particle tracking simulations based on modifying the field map from the Front-End Test Stand (FETS) RFQ design have determined the best operating frequency for the PAMELA RFQ to be close to 200 MHz and the length approximately 2.3 m. The status of the injector design with an emphasis on the RFQ will be presented, together with the results of the particle tracking.
For the PAMELA project, the injection layout for both protons as well as carbon 6 + ions is discu... more For the PAMELA project, the injection layout for both protons as well as carbon 6 + ions is discussed. The injection system would consist of a 30 MeV cyclotron for protons and a chain of elements for carbon ions such as ECR ion source, bending magnets and focusing solenoids; RFQ, IH/CH structures and a stripping foil. The charge particle simulation for both protons and carbon ions passing through the elements has been carried out via General Particle Tracer (GPT) software.
A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed... more A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. Previous beam dynamics simulations, based on field maps produced with a field approximation code, provide a baseline for the new design. A novel design method is presented that combines the CAD and electromagnetic modelling of both the RFQ tank and the vane modulations with more sophisticated beam dynamics simulations using the General Particle Tracer code (GPT). This approach allows the full inte-gration of the optimisation of the RFQ, based on beam dynamics simulations using a 3D EM-field map of the CAD model, with the design and manufacture of the RFQ vane modulations and RFQ tank. The design process within the Autodesk Inventor CAD software is outlined and details of the EM modelling of the RFQ in CST MicroWave Studio are given. Results of beam dynamics simulations in GPT are presented and compared to previous results with field approximation codes. Finally, possible methods of manufacture based on this design process are discussed.
The PAMELA (Particle Accelerator for MEdicaL Applications) project is to design an accelerator fo... more The PAMELA (Particle Accelerator for MEdicaL Applications) project is to design an accelerator for proton and light ion therapy using non-scaling Fixed Field Alternating Gradient (FFAG) accelerators, as part of the CONFORM project, which is also constructing the EMMA electron model of a non-scaling FFAG at Daresbury. This paper presents an overview of the PAMELA design, and a discussion of the design goals and the principles used to arrive at a preliminary specification of the accelerator.
Spot scanning irradiation is a novel and powerful scheme for particle therapy. The pulsed beam st... more Spot scanning irradiation is a novel and powerful scheme for particle therapy. The pulsed beam structure of FFAG (Fixed Field Alternating Gradient) accelerator is suitable for the scheme. In order to form an uniform dose distribution in a target volume, Beam intensity must be modulated in sync with beam energy modulation. The intensity modulation requires precise intensity control and constrain the bunch intensity of accelerator of pulsed beam structure. In the paper, injection related issue, that is the intensity modulation of FFAG accelerator, is discussed from the view point of spot scanning.
A detector comprising an analytical apparatus for detecting a substance of interest, and a detect... more A detector comprising an analytical apparatus for detecting a substance of interest, and a detector inlet. The detector inlet comprises a flow passage for carrying a flow of fluid, the flow passage comprising a sampling volume,and a sampling inlet adapted to collect samples of the fluid from the sampling volume as the fluid flows past the sampling inlet, and to provide the samples to the analytical apparatus, wherein the flow of fluid carries particulates. The detector inlet also comprises a flow director arranged to vary a spatial distribution of the particulates carried by the fluid to increase a relative proportion of the particulates carried past the sampling inlet along the flow passage without entering the sampling volume.
Systems and techniques for cleaning a corona discharge point are described. A controller (150) ca... more Systems and techniques for cleaning a corona discharge point are described. A controller (150) can be operatively coupled to a corona discharge point (108) to control the operation of the corona discharge point (1089. The controller (150) and the corona discharge point (108) can be included with, for example, an ion mobility spectrometry (IMS) system (100). The controller (150) can be used to operate the corona discharge point (108) at an operating voltage for a first time interval, with or without an additional higher pulse voltage, to produce a corona discharge, and to operate the corona discharge point (108) at a cleaning voltage greater than the operating voltage for a second time interval subsequent to the first time interval to produce a corona discharge. The effectiveness of the corona discharge point (108) can be monitored by, for instance, measuring a voltage necessary to produce a corona discharge at the corona discharge point (108), measuring a current produced at the corona discharge point (108) from a corona discharge, and so forth.
The PAMELA project aims to design an FFAG accelera-tor for cancer therapy using protons and carbo... more The PAMELA project aims to design an FFAG accelera-tor for cancer therapy using protons and carbon ions. For the injection system for carbon ions, an RFQ is one op-tion for the first stage of acceleration. An integrated RFQ design process has been developed using various ...
The PAMELA project aims to design an FFAG accelera-tor for cancer therapy using protons and carbo... more The PAMELA project aims to design an FFAG accelera-tor for cancer therapy using protons and carbon ions. For the injection system for carbon ions, an RFQ is one op-tion for the first stage of acceleration. An integrated RFQ design process has been developed using various ...
The status of PAMELA (Particle Accelerator for MEdicaL Applications) ¿ an accelerator for proton ... more The status of PAMELA (Particle Accelerator for MEdicaL Applications) ¿ an accelerator for proton and light ion therapy using a non-scaling FFAG (ns-FFAG) accelerator ¿ is reviewed and discussed.
The PAMELA medical FFAG complex under design in the UK, aims to operate with both proton and carb... more The PAMELA medical FFAG complex under design in the UK, aims to operate with both proton and carbon beams for hadron therapy. Medium energy beam transfer(MEBT) of PAMELA consists of the proton beam line coming out of the injector cyclotron, carbon beam transfer from the independent carbon 6+ injector linac, switching dipole when both beam merge and transfer line toward the PAMELA NS-FFAG. The MEBT layout and design, which needs to incorporate the beam chopper for the intensity modulation are discussed. The careful matching of optical functions between various components in the MEBT and beam dynamics simulations are presented.
For the PAMELA medical non-scaling FFAG, carbon 6+ as well as proton particles are required. The ... more For the PAMELA medical non-scaling FFAG, carbon 6+ as well as proton particles are required. The general injection layout based on a cyclotron for proton and a Linac for carbon is considered. There are two options for pre-accelerating carbon ions for PAMELA, either accelerating carbon with the charge state 4+ from the ion source and stripping after the pre-accelerator or directly accelerating carbon 6+ ions all the way from the ion source. For both options solution has been investigated. Simulations of beam dynamics for both particle species are presented. The resulting schemes based on either the single turn or multiturn injection into the first FFAG ring are discussed.
A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed... more A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. A novel design method, integrating the CAD and electromagnetic design of the RFQ with beam dynamics simulations, is being used to optimise the design of the RFQ. Basic RFQ parameters are produced with the RFQSIM code. A full CAD model of the RFQ vane tips is produced in Autodesk Inventor, based upon these parameters. This model is then imported into a field mapping code to produce a simulation of the electrostatic field around the vane tips. This field map is then used to model the beam dynamics within the RFQ using General Particle Tracer (GPT). Previous studies have been carried out using field mapping in CST EM Studio. A more advanced technique using Comsol Multiphysics and Matlab, that more tightly integrates the CAD modelling, field mapping and beam dynamics simulations, is described. Results using this new method are presented ...
The PAMELA (Particle Accelerator for MEdicaL Applications) project aims to design an ns-FFAG acce... more The PAMELA (Particle Accelerator for MEdicaL Applications) project aims to design an ns-FFAG accelerator for cancer therapy using protons and carbon ions. For the injection system for carbon ions, an RFQ is one option for the first stage of acceleration. Our integrated RFQ design process* has been developed further using Comsol Multiphysics for electric field modelling. The design parameters for the RFQ are automatically converted to a CAD model using Autodesk Inventor, and the electric field map for this model is simulated in Comsol. Particles can then be tracked through this field map using Pulsar Physics' General Particle Tracer (GPT). Our software uses Visual Basic for Applications and MATLAB to automate this process and allow for optimisation of the RFQ design parameters based on particle dynamical considerations. Possible designs for the PAMELA RFQ, including super-conducting and normal-conducting solutions, will be presented and discussed, together with results of the fie...
This thesis describes a new design method for a radio frequency quadrupole (RFQ), and its applica... more This thesis describes a new design method for a radio frequency quadrupole (RFQ), and its application to the first stage of acceleration for carbon ions in the PAMELA injector. Radiotherapy is a valuable form of cancer treatment, but current methods using photons or electrons make it difficult to deliver an adequate dose to the tumour without damaging healthy surrounding tissue and organs. Charged hadron beams, such as protons and carbon, deposit most of the dose at the Bragg peak, which can be aligned with the tumour. This allows higher doses to treat the cancer while minimising damage to healthy surrounding tissue and organs. The PAMELA project (part of the BASROC consortium) aims to design new charged particle therapy (CPT) facilities using non-scaling fixed-field alternating-gradient accelerators (ns-FFAGs). This new technology offers significant advantages over both cyclotrons and synchrotrons for CPT. The injector for the PAMELA FFAG accelerator includes separate pre-accelerat...
Abstract Collection of particles from a laser-driven accelerator into a conventional beamline req... more Abstract Collection of particles from a laser-driven accelerator into a conventional beamline requires careful manipulation of the beam to handle the wide energy spread, large angular divergence and short pulse lengths characteristic of laser-driven acceleration. Accurate simulation of the first few millimetres is crucial in order to optimise the collecting elements such as solenoids or quadrupole magnets. Experiments and simulations both show significant emittance growth in this collection region. We have developed a multi-particle beam dynamics model using impact-t that includes the characteristic exponentially-decaying laser-driven energy spectrum and accurately models the emittance growth due to the large energy spread. In this paper we present theoretical relationships between energy spread and emittance growth, and compare these with the simulated emittance growth. Results show excellent correspondence between theory and simulation. The effect is negligible for low-energy proton accelerators, but is important for electron accelerators and for proposed high-energy laser-driven proton accelerators.
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