This thesis consists of a study of the magnetic field diffusion equation and magnetic equilibrium... more This thesis consists of a study of the magnetic field diffusion equation and magnetic equilibrium reconstructions using the transport analysis code TRANSP and the free-boundary equilibrium code EFIT in the JET tokamak. TRANSP uses the magnetic field diffusion equation to calculate the evolution of the current profile. The thesis includes a description of the TRANSP code, with emphasis on the implementation of current diffusion. The pitch angle predicted by TRANSP is compared with motional Stark effect (MSE) polarimetry data. The accuracy of the TRANSP predictions depends on the validity of the resistivity model employed. The comparison is carried out on a large range of pulses, including cases of current hole plasmas (i.e. plasmas with a region of close to zero current density around the magnetic axis). In particular, the evolution of the pitch angle as the current hole contracts is investigated. The TRANSP output is also compared to Faraday rotation polarimetry, MHD and surface vol...
K. Peach#, J. Cobb, SL Sheehy, H. Witte, T. Yokoi, JAI, Oxford, UK, R. Fenning, A. Khan, Brunel U... more K. Peach#, J. Cobb, SL Sheehy, H. Witte, T. Yokoi, JAI, Oxford, UK, R. Fenning, A. Khan, Brunel University, UK, R. Seviour, Cockcroft Institute, Lancaster University, UK, C. Johnstone, Fermilab, Batavia, Illinois, USA, M. Hill, B. Jones, B. Vojnovic, Gray Institute, Oxford, UK, M. Aslaninejad, M. Easton, Imperial College, London, UK, J. Pasternak, Jürgen Klaus Pozimski, Imperial College, London and STFC RAL, UK, Carl Beard, N. Bliss, T. Jones, P. McIntosh, S. Pattalwar, SL Smith, J. Strachan, S. Tzenov, STFC ... Daresbury, UK, TR Edgecock, ISK ...
The large variation in betatron tune over the energy range of the EMMA non-scaling FFAG, and the ... more The large variation in betatron tune over the energy range of the EMMA non-scaling FFAG, and the rapidity of the acceleration, result in novel features in the properties of orbit distortion. The crossing of many integer tune resonances is achieved through fast crossing. It is clear that standard harmonic correction is not applicable since the phase advance between lattice elements varies with momentum. Two correction methods that reduce orbit distortion due to transverse magnet misalignments are presented - local correction of the error sources and optimisation of the injection coordinates and corrector magnet strengths.
High power driver rings are examined, using new FFAG designs, based on cells of five, scalin... more High power driver rings are examined, using new FFAG designs, based on cells of five, scaling symmetrical pumplet magnets. Apertures are minimized by using large, betatron phase shifts per cell, typically μh ~ 280° and μv ~ 130°. Key aspects are the lengths of the long straight sections, particularly IF Hˉ charge exchange injection is required. Rings are considered for ISIS upgrades and Neutrino Factory proton and muon drivers. both with and without insertions.
Nonscaling FFAG is required for the muon acceleration in the Neutrino Factory, which b... more Nonscaling FFAG is required for the muon acceleration in the Neutrino Factory, which baseline design is under investigation in the International Design Study (IDS-NF). In order to inject/extract the muon beam with a very large emittance, several strong kickers with a very large aperture are required distributed in many lattice cells. Once the sufficient orbit separation is obtained by the kickers, the final degree of separation from the lattice is made by the septum, which needs to be superconducting. The geometry of the symmetric solutions allowing to inject/extract both signs of muons is presented. The preliminary design of the kicker and septum magnets is given.
Non-scaling FFAG rings have been proposed for muon acceleration in a neutrino factory. In order t... more Non-scaling FFAG rings have been proposed for muon acceleration in a neutrino factory. In order to achieve small orbit excursion and small time of flight variation, lattices with a very compact cell structure and short straight sections are required. The resulting geometry places very challenging constraints on the injection/extraction systems. The feasibility of injection/extraction is discussed and various implementations focusing on minimization of kicker/septum strength are presented. The injection and extraction systems in the nonscaling FFAG for muon acceleration in a neutrino factory were studied in the ring based on FODO lattice. The vertical direction was found to be preferential for both injection and extraction, which allows for lower kicker strengths and facilitates the distribution of kickers due to a lower phase advance per cell in comparison with the horizontal plane. It is possible to design mirror-symmetric schemes in which the kickers can be reused for both signs o...
This paper describes the setting up of ray-tracing tools and premilinary beam dynamics studies co... more This paper describes the setting up of ray-tracing tools and premilinary beam dynamics studies concerning the electron model 3-5.4463 MeV of a non-linear, non-scaling proton driver FFAG 3-10 GeV.
A novel nonlinear, nonscaling FFAG ring has been designed for proton and ion acceleration [1]. It... more A novel nonlinear, nonscaling FFAG ring has been designed for proton and ion acceleration [1]. It can be used for proton and carbon therapy as well as a proton driver for various facilities such as a high intensity neutrino factory. The machine has novel features including variable energy extraction and a high repetition rate of about 1 kHz. Taking as an example the PAMELA proton ring, under study at the John Adams Institute in Oxford, we present results of an error study. A calculation of alignment tolerance is made, in which the effects of translational misalignments of the triplet magnets are included. The effect of misalignments on the dynamic aperture of the machine is investigated.
Monitoring the muon beam properties in the final stage of the Neutrino Factory (the Decay Ring) i... more Monitoring the muon beam properties in the final stage of the Neutrino Factory (the Decay Ring) is important for the understanding of the beam itself and a crucial piece of information for the downstream physics. The main topics to be assessed are: knowledge of the muon beam energy and polarization, divergence of the beam and beam current. In the framework of the International Design Study for the Neutrino Factory (IDS-NF) a racetrack model Decay Ring based on G4Beamline has been produced to simulate elec-trons from muon decays and the measurement of the beam energy distribution via the spin precession technique. The use of other codes, like Zgoubi, to generate a realistic beam including effects like spin polarization, are considered. A general discussion on future work is presented.
Fixed field alternating gradient (FFAG) accelerators hold a lot of promise for high power operati... more Fixed field alternating gradient (FFAG) accelerators hold a lot of promise for high power operation due to their high repetition rate and strong focusing optics. However, to date these machines have not been operated with high intensity beams. Since November 2013 an experimental collaboration has been underway to characterise the 150 MeV proton FFAG at KURRI, Japan. Here we report on the results of characterisation experiments and discuss plans for further experiments in the high intensity regime.
The Hamiltonian governing the dynamics in a Linear Paul Trap (LPT) is identical in form to that o... more The Hamiltonian governing the dynamics in a Linear Paul Trap (LPT) is identical in form to that of a beam in a focusing channel. This similarity, together with the LPT’s flexibility, compactness and low cost, make it a useful tool for the study of a wide range of accelerator physics topics. Existing work has focused on high intensity collective effects as well as, more recently, the study of integer resonance crossing in the low intensity regime. A natural extension of this work is to investigate space-charge effects of intense beams in more realistic lattices to directly inform accelerator design and development. For this purpose we propose to construct a modified Paul Trap specifically for these studies. Among other features, it is envisaged that this new LPT should be able to model non-linear elements and a wider range of lattice configurations. This work will be undertaken in collaboration with Hiroshimi University.
EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory ... more EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory in the UK and will be the first non-scaling FFAG ever constructed. The purpose of EMMA is to study beam dynamics in such an accelerator. The EMMA orbit correction scheme must deal with two characteristics of a non-scaling FFAG: i.e. the lack of a well defined reference orbit and the variation with momentum of the phase advance. In this study we present a novel orbit correction scheme that avoids the former problem by instead aiming to maximise both the symmetry of the orbit and the physical aperture of the beam. The latter problem is dealt with by optimising the corrector strengths over the energy range.
For over a decade, Linear Paul Traps (LPT) have been used in the study of accelerator beam dynami... more For over a decade, Linear Paul Traps (LPT) have been used in the study of accelerator beam dynamics. LPT studies exploit the similarity of the Hamiltonian with that of a beam in a quadrupole channel while having advantages in the flexibility of parameter choice, compactness and low cost. In collaboration with Hiroshima University, LPT research planned at STFC Rutherford Appleton Laboratory (RAL) in the UK aims to investigate a range of topics including resonance crossing, halo formation, long-term stability studies and space charge effects. Initially, a conventional quadrupole-based LPT will be built at RAL and used for a variety of experiments. In parallel, a design for a more advanced LPT that incorporates higher order multipoles will be pursued and later constructed. This multipole trap will allow non-linear lattice elements to be simulated and so broaden considerably the range of experiments that can be conducted. These will include the investigation of resonance crossing in non...
This thesis consists of a study of the magnetic field diffusion equation and magnetic equilibrium... more This thesis consists of a study of the magnetic field diffusion equation and magnetic equilibrium reconstructions using the transport analysis code TRANSP and the free-boundary equilibrium code EFIT in the JET tokamak. TRANSP uses the magnetic field diffusion equation to calculate the evolution of the current profile. The thesis includes a description of the TRANSP code, with emphasis on the implementation of current diffusion. The pitch angle predicted by TRANSP is compared with motional Stark effect (MSE) polarimetry data. The accuracy of the TRANSP predictions depends on the validity of the resistivity model employed. The comparison is carried out on a large range of pulses, including cases of current hole plasmas (i.e. plasmas with a region of close to zero current density around the magnetic axis). In particular, the evolution of the pitch angle as the current hole contracts is investigated. The TRANSP output is also compared to Faraday rotation polarimetry, MHD and surface vol...
K. Peach#, J. Cobb, SL Sheehy, H. Witte, T. Yokoi, JAI, Oxford, UK, R. Fenning, A. Khan, Brunel U... more K. Peach#, J. Cobb, SL Sheehy, H. Witte, T. Yokoi, JAI, Oxford, UK, R. Fenning, A. Khan, Brunel University, UK, R. Seviour, Cockcroft Institute, Lancaster University, UK, C. Johnstone, Fermilab, Batavia, Illinois, USA, M. Hill, B. Jones, B. Vojnovic, Gray Institute, Oxford, UK, M. Aslaninejad, M. Easton, Imperial College, London, UK, J. Pasternak, Jürgen Klaus Pozimski, Imperial College, London and STFC RAL, UK, Carl Beard, N. Bliss, T. Jones, P. McIntosh, S. Pattalwar, SL Smith, J. Strachan, S. Tzenov, STFC ... Daresbury, UK, TR Edgecock, ISK ...
The large variation in betatron tune over the energy range of the EMMA non-scaling FFAG, and the ... more The large variation in betatron tune over the energy range of the EMMA non-scaling FFAG, and the rapidity of the acceleration, result in novel features in the properties of orbit distortion. The crossing of many integer tune resonances is achieved through fast crossing. It is clear that standard harmonic correction is not applicable since the phase advance between lattice elements varies with momentum. Two correction methods that reduce orbit distortion due to transverse magnet misalignments are presented - local correction of the error sources and optimisation of the injection coordinates and corrector magnet strengths.
High power driver rings are examined, using new FFAG designs, based on cells of five, scalin... more High power driver rings are examined, using new FFAG designs, based on cells of five, scaling symmetrical pumplet magnets. Apertures are minimized by using large, betatron phase shifts per cell, typically μh ~ 280° and μv ~ 130°. Key aspects are the lengths of the long straight sections, particularly IF Hˉ charge exchange injection is required. Rings are considered for ISIS upgrades and Neutrino Factory proton and muon drivers. both with and without insertions.
Nonscaling FFAG is required for the muon acceleration in the Neutrino Factory, which b... more Nonscaling FFAG is required for the muon acceleration in the Neutrino Factory, which baseline design is under investigation in the International Design Study (IDS-NF). In order to inject/extract the muon beam with a very large emittance, several strong kickers with a very large aperture are required distributed in many lattice cells. Once the sufficient orbit separation is obtained by the kickers, the final degree of separation from the lattice is made by the septum, which needs to be superconducting. The geometry of the symmetric solutions allowing to inject/extract both signs of muons is presented. The preliminary design of the kicker and septum magnets is given.
Non-scaling FFAG rings have been proposed for muon acceleration in a neutrino factory. In order t... more Non-scaling FFAG rings have been proposed for muon acceleration in a neutrino factory. In order to achieve small orbit excursion and small time of flight variation, lattices with a very compact cell structure and short straight sections are required. The resulting geometry places very challenging constraints on the injection/extraction systems. The feasibility of injection/extraction is discussed and various implementations focusing on minimization of kicker/septum strength are presented. The injection and extraction systems in the nonscaling FFAG for muon acceleration in a neutrino factory were studied in the ring based on FODO lattice. The vertical direction was found to be preferential for both injection and extraction, which allows for lower kicker strengths and facilitates the distribution of kickers due to a lower phase advance per cell in comparison with the horizontal plane. It is possible to design mirror-symmetric schemes in which the kickers can be reused for both signs o...
This paper describes the setting up of ray-tracing tools and premilinary beam dynamics studies co... more This paper describes the setting up of ray-tracing tools and premilinary beam dynamics studies concerning the electron model 3-5.4463 MeV of a non-linear, non-scaling proton driver FFAG 3-10 GeV.
A novel nonlinear, nonscaling FFAG ring has been designed for proton and ion acceleration [1]. It... more A novel nonlinear, nonscaling FFAG ring has been designed for proton and ion acceleration [1]. It can be used for proton and carbon therapy as well as a proton driver for various facilities such as a high intensity neutrino factory. The machine has novel features including variable energy extraction and a high repetition rate of about 1 kHz. Taking as an example the PAMELA proton ring, under study at the John Adams Institute in Oxford, we present results of an error study. A calculation of alignment tolerance is made, in which the effects of translational misalignments of the triplet magnets are included. The effect of misalignments on the dynamic aperture of the machine is investigated.
Monitoring the muon beam properties in the final stage of the Neutrino Factory (the Decay Ring) i... more Monitoring the muon beam properties in the final stage of the Neutrino Factory (the Decay Ring) is important for the understanding of the beam itself and a crucial piece of information for the downstream physics. The main topics to be assessed are: knowledge of the muon beam energy and polarization, divergence of the beam and beam current. In the framework of the International Design Study for the Neutrino Factory (IDS-NF) a racetrack model Decay Ring based on G4Beamline has been produced to simulate elec-trons from muon decays and the measurement of the beam energy distribution via the spin precession technique. The use of other codes, like Zgoubi, to generate a realistic beam including effects like spin polarization, are considered. A general discussion on future work is presented.
Fixed field alternating gradient (FFAG) accelerators hold a lot of promise for high power operati... more Fixed field alternating gradient (FFAG) accelerators hold a lot of promise for high power operation due to their high repetition rate and strong focusing optics. However, to date these machines have not been operated with high intensity beams. Since November 2013 an experimental collaboration has been underway to characterise the 150 MeV proton FFAG at KURRI, Japan. Here we report on the results of characterisation experiments and discuss plans for further experiments in the high intensity regime.
The Hamiltonian governing the dynamics in a Linear Paul Trap (LPT) is identical in form to that o... more The Hamiltonian governing the dynamics in a Linear Paul Trap (LPT) is identical in form to that of a beam in a focusing channel. This similarity, together with the LPT’s flexibility, compactness and low cost, make it a useful tool for the study of a wide range of accelerator physics topics. Existing work has focused on high intensity collective effects as well as, more recently, the study of integer resonance crossing in the low intensity regime. A natural extension of this work is to investigate space-charge effects of intense beams in more realistic lattices to directly inform accelerator design and development. For this purpose we propose to construct a modified Paul Trap specifically for these studies. Among other features, it is envisaged that this new LPT should be able to model non-linear elements and a wider range of lattice configurations. This work will be undertaken in collaboration with Hiroshimi University.
EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory ... more EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory in the UK and will be the first non-scaling FFAG ever constructed. The purpose of EMMA is to study beam dynamics in such an accelerator. The EMMA orbit correction scheme must deal with two characteristics of a non-scaling FFAG: i.e. the lack of a well defined reference orbit and the variation with momentum of the phase advance. In this study we present a novel orbit correction scheme that avoids the former problem by instead aiming to maximise both the symmetry of the orbit and the physical aperture of the beam. The latter problem is dealt with by optimising the corrector strengths over the energy range.
For over a decade, Linear Paul Traps (LPT) have been used in the study of accelerator beam dynami... more For over a decade, Linear Paul Traps (LPT) have been used in the study of accelerator beam dynamics. LPT studies exploit the similarity of the Hamiltonian with that of a beam in a quadrupole channel while having advantages in the flexibility of parameter choice, compactness and low cost. In collaboration with Hiroshima University, LPT research planned at STFC Rutherford Appleton Laboratory (RAL) in the UK aims to investigate a range of topics including resonance crossing, halo formation, long-term stability studies and space charge effects. Initially, a conventional quadrupole-based LPT will be built at RAL and used for a variety of experiments. In parallel, a design for a more advanced LPT that incorporates higher order multipoles will be pursued and later constructed. This multipole trap will allow non-linear lattice elements to be simulated and so broaden considerably the range of experiments that can be conducted. These will include the investigation of resonance crossing in non...
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Papers by David J Kelliher