Ieee Conference Record Abstracts 2002 Ieee International Conference on Plasma Science, 2002
Summary form only given, as follows. The Cold-Test, Large-Signal Simulation Code (CTLSS) is being... more Summary form only given, as follows. The Cold-Test, Large-Signal Simulation Code (CTLSS) is being developed to provide a 3D electromagnetic simulation tool that is designed to interoperate with large-signal codes employed in microwave and millimeter-wave vacuum electron device design. In this presentation, we describe capabilities recently introduced in CTLSS that directly support features of the large-signal simulation codes CHRISTINE ID and CHRISTINE 3D. For large signal models that operate in the frequency domain, it is necessary to specify device characteristics at selected operating frequencies. A new eigensolver capability has been developed in CTLSS to determine the eigenmode fields and related parameters (phase velocity, interaction impedances & admittances, etc.) of a dispersive periodic structure at a predetermined frequency. This contrasts with the more common approach, in which the frequency of a traveling wave is computed for a specified phase advance per period (Floquet boundary condition), and results later interpolated to the frequencies of interest. The new method reduces the total computation time required to obtain parameters for the large-signal models. The CHRISTINE 3D code simulates the large-signal characteristics of slow-wave devices using a fast, parametric model that includes a fully three-dimensional representation of both particle motion and electromagnetic fields. The traveling-wave circuit field and the RF space-charge field are treated separately, but self-consistently, and in common with many existing parametric large-signal models, the space-charge fields are computed assuming that they exist only within a cylindrical pipe at the inner radius of the circuit structures. We describe a method for correcting the space-charge field to take account of the true 3D geometry, using correction terms that are precomputed from the full circuit structure using CTLSS.
International Conference on Plasma Science (papers in summary form only received), 1995
ABSTRACT Summary form only given, as follows. The grid generator tool for MMACE connects existing... more ABSTRACT Summary form only given, as follows. The grid generator tool for MMACE connects existing grid generator technology to the research engineering framework (REF). It will read geometry from the database and allow the user interactively to construct grids which meet the needs of MMACE application tools. The initial focus is on 2-D rectangular grids for existing MMACE applications such as particle-in-cell, magnet, and gun codes. We expect to show results from the grid tool running in a work-station environment. The tool provides capabilities for automatic or user-directed identification of key points of the geometry which need to be matched to the grid. From these grid markers, and templates containing the gridding strategy, the tool generates the entire grid. When aspects of the geometry move, the grid markers move with them, thus providing automated re-gridding. Since application run times are often affected by the size of the smallest cell and the total number of grid points, the tool will track and display these. In addition, the gridding template may contain constraints on these parameters and will identify conflicts to the constraints. An application programming interface (API) is being constructed to provide easy and standardized access to the grid information model within the MMACE database. The grid tool will be built upon the API and will output the grid to the database for use by MMACE applications. The API will provide standardized facilities for applications to retrieve the grid
An important problem in the design of RF linacs is the coupling between the waveguide that feeds ... more An important problem in the design of RF linacs is the coupling between the waveguide that feeds RF power into the accelerator and the cavity through which the beam is being accelerated. The designer needs to know the coupling coefficient, the frequency shift, and the external Q due to the waveguide. In addition, the details of the field geometry in
: The material covered in this report consists of three general areas in which plasma physics pla... more : The material covered in this report consists of three general areas in which plasma physics plays a significant role in the modeling of radiation sources for the advanced simulation research program. The first is the description of a basic model for the implosion of a system of identical wires driven by a pulsed power generator. The second is a model for computing the linear ideal MHD instability growth rates for azimuthally symmetric, cylindrical Z pinch equilibria. This analyses includes both kink and sausage type perturbations of the equilibrium. The third area concerns the properties of magnetically insulated power feeds for driving imploding Z pinch loads.
This report covers the period June 1981 to June 1983, during which time investigations were condu... more This report covers the period June 1981 to June 1983, during which time investigations were conducted into several major topics concerning the behavior of an intense (multi-kiloampere) electron beam in the modified betatron electron accelerator. The modified betatron has been selected for experimental evaluation as a high-current electron accelerator. Theoretical support has been directed at identifying those phenomena which will most directly affect accelerator performance. To this end, research has been carried out in the following areas: (1) Transverse linear beam dynamics in time varying, azimuthally symmetric fields, (2) Effects of grad B theta induced drifts, (3) Orbital resonance effects due to small field errors, (4) Nonlinear effects, especially those due to non constant betatron field index, (5) Collective effects, especially the negative mass instability, and (6) Strongly focused systems.
The combination of a bumpy torus field and a conventional betatron field leads to an interesting ... more The combination of a bumpy torus field and a conventional betatron field leads to an interesting strongly focused, high-current accelerator configuration. The question of orbital stability of a test particle in such a device is discussed, and it is shown that the alternating gradient focusing in this accelerator can easily lead to greater than 20% bandwidth in allowed mismatch between the vertical magnetic field and the average beam particle energy.
The development of electron-positron linear colliders in the TeV energy range will be facilitated... more The development of electron-positron linear colliders in the TeV energy range will be facilitated by the development of high-power rf sources at frequencies above 2856 MHz. Present S-band technology, represented by the SLC, would require a length in excess of 50 km per linac to accelerate particles to energies above 1 TeV. By raising the rf driving frequency, the rf breakdown limit is increased, thereby allowing the length of the accelerators to be reduced. Currently available rf power sources set the realizable gradient limit in an rf linac at frequencies above S-band. This paper presents a model for the frequency scaling of linear colliders, with luminosity scaled in proportion to the square of the center-of-mass energy. Since wakefield effects are the dominant deleterious effect, a separate single-bunch simulation model is described which calculates the evolution of the beam bunch with specified wakefields, including the effects of using programmed phase positioning and Landau da...
Relativistic, cylindrical, rigid-rotor equilibria for electrons are developed in the beam frame, ... more Relativistic, cylindrical, rigid-rotor equilibria for electrons are developed in the beam frame, and the corresponding laboratory frame equilibria are obtained by Lorentz transformation. Limitations of the two-mass approximation are thus illuminated. A toroidal equilibrium is developed that is based on the two-mass approximation and expansion in terms of the ratio of minor to major radius. The toroidal equilibrium is shown to have no unstable kink-modes or no Kruskal-Shafranov current limit as in a Tokamak. Small variations in the toroidal magnetic field around the torus result in trapped electrons if they are injected with sufficient transverse energy. The presence of both trapped and untrapped electrons leads to two-stream instabilities. Some comparisons are made with HIPAC experiments and the recent torus experiments at MLI.
The grid generator tool for MMACE connects existing grid generator technology to the Research Eng... more The grid generator tool for MMACE connects existing grid generator technology to the Research Engineering Framework (REF). It will read geometry from the database and allow the user interactively to construct grids which meet the needs of MMACE application tools. The initial focus is on 2-D rectangular grids for existing MMACE applications such as particle-in-cell, magnet, and gun codes. The authors expect to show results from the grid tool running in a work-station environment. The tool provides capabilities for automatic or user-directed identification of key points of the geometry which need to be matched to the grid. From these grid markers, and templates containing the gridding strategy, the tool generates the entire grid. When aspects of the geometry move, the grid markers move with them, thus providing automated re-gridding. Since application run times are often affected by the size of the smallest cell and the total number of grid points, the tool will track and display thes...
This review of e+e− linear colliders Is for the most part tutorial, but It will also present some... more This review of e+e− linear colliders Is for the most part tutorial, but It will also present some new results that are summarized in Section 1 and discussed in more detail in Sections 4 and 5. The paper is restricted to colliders with SLAC-type linac structures. The scaling with frequency in the range from 8 to 20 GHz is studied for a 500 GeV on 500 GeV accelerator system of fixed length (2 × 3 km) and luminosity L = 1033 cm−2s−1, as presently being considered at Stanford. Two scenarios, one which is limited by beamstrahlung where the number of particles per bunch, N, is approximately constant and one in which N is proportional to wavelength λ, are investigated. While the peak rf power requirement for each feed decreases with frequency identically in both cases, average ac power decreases with ω in the first case but increases in the second. Gyroklystron design parameters are presented that would meet the peak power requirements in X-band.
Summary form only given, as follows. The ARGUS-ESP code has been used to calculate electromagneti... more Summary form only given, as follows. The ARGUS-ESP code has been used to calculate electromagnetic vacuum eigenmodes, including dispersion diagrams, for both standing-wave and traveling-wave devices. Slow-wave structures, as used in microwave devices, are readily modeled with this code. ARGUS-ESP gives the designer the ability to do numerical cold testing. ARGUS is a fully 3D electromagnetic suite of codes that share a common framework. This common framework, across several methods of solution, gives ARGUS the ability to model complex structures in various ways. The suite includes electromagnetic eigenmode (ESP), time-domain, and single-frequency (or driven-frequency) models, as well as electrostatic models. Additionally, particle-in-cell (PIC) models are included in both time-domain and equilibrium (gun) modes. For this presentation, the ARGUS electromagnetic eigenmode solver, ESP, is featured. This solver gives the user the capability to calculate cavity modes for general, arbitra...
IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science. 26th IEEE International Conference (Cat. No.99CH36297), 2000
ABSTRACT Summary form only given, as follows. The cold-test and large-signal simulator (CTLSS) co... more ABSTRACT Summary form only given, as follows. The cold-test and large-signal simulator (CTLSS) code is a three-dimensional simulation tool developed specifically for the modeling of vacuum electron devices. It is a three-dimensional resonant electromagnetic frequency-domain code coupled to the CHRISTINE large-signal model. This paper will describe new results in the application of CTLSS to design calculations for slow-wave devices. Current directions for CTLSS development will also be described. Simulations of helix TWTs are presented that demonstrate a methodology consisting of using CHRTSTINE for parametric optimization, followed by CTLSS cold-test calculations of the CHRISTINE optimum to capture the effects of real geometry and real materials on the dispersion and impedance of the helix device with support rods. As a final step, CHRISTINE is exercised using the cold-test parameters from CTLSS to compute the consequences of materials and geometry for device performance
ARGUS is an integrated, 3-D, volumetric simulation model for systems involving electric and magne... more ARGUS is an integrated, 3-D, volumetric simulation model for systems involving electric and magnetic fields and charged particles, including materials embedded in the simulation region. The code offers the capability to carry out time domain and frequency domain electromagnetic simulations of complex physical systems. ARGUS offers a boolean solid model structure input capability that can include essentially arbitrary structures on
Proceedings of the 1989 IEEE Particle Accelerator Conference, . 'Accelerator Science and Technology, 1989
Argus is a system of three-dimensional codes which share the same utilities for structure input a... more Argus is a system of three-dimensional codes which share the same utilities for structure input and grid generation, memory management, data handling, and diagnostics. The field module of Argus can solve for electrostatic fields or for the complete electromagnetic fields in either the frequency or time domain. This module can be used as a stand-alone code for impedance and other
Ieee Conference Record Abstracts 2002 Ieee International Conference on Plasma Science, 2002
Summary form only given, as follows. The Cold-Test, Large-Signal Simulation Code (CTLSS) is being... more Summary form only given, as follows. The Cold-Test, Large-Signal Simulation Code (CTLSS) is being developed to provide a 3D electromagnetic simulation tool that is designed to interoperate with large-signal codes employed in microwave and millimeter-wave vacuum electron device design. In this presentation, we describe capabilities recently introduced in CTLSS that directly support features of the large-signal simulation codes CHRISTINE ID and CHRISTINE 3D. For large signal models that operate in the frequency domain, it is necessary to specify device characteristics at selected operating frequencies. A new eigensolver capability has been developed in CTLSS to determine the eigenmode fields and related parameters (phase velocity, interaction impedances & admittances, etc.) of a dispersive periodic structure at a predetermined frequency. This contrasts with the more common approach, in which the frequency of a traveling wave is computed for a specified phase advance per period (Floquet boundary condition), and results later interpolated to the frequencies of interest. The new method reduces the total computation time required to obtain parameters for the large-signal models. The CHRISTINE 3D code simulates the large-signal characteristics of slow-wave devices using a fast, parametric model that includes a fully three-dimensional representation of both particle motion and electromagnetic fields. The traveling-wave circuit field and the RF space-charge field are treated separately, but self-consistently, and in common with many existing parametric large-signal models, the space-charge fields are computed assuming that they exist only within a cylindrical pipe at the inner radius of the circuit structures. We describe a method for correcting the space-charge field to take account of the true 3D geometry, using correction terms that are precomputed from the full circuit structure using CTLSS.
International Conference on Plasma Science (papers in summary form only received), 1995
ABSTRACT Summary form only given, as follows. The grid generator tool for MMACE connects existing... more ABSTRACT Summary form only given, as follows. The grid generator tool for MMACE connects existing grid generator technology to the research engineering framework (REF). It will read geometry from the database and allow the user interactively to construct grids which meet the needs of MMACE application tools. The initial focus is on 2-D rectangular grids for existing MMACE applications such as particle-in-cell, magnet, and gun codes. We expect to show results from the grid tool running in a work-station environment. The tool provides capabilities for automatic or user-directed identification of key points of the geometry which need to be matched to the grid. From these grid markers, and templates containing the gridding strategy, the tool generates the entire grid. When aspects of the geometry move, the grid markers move with them, thus providing automated re-gridding. Since application run times are often affected by the size of the smallest cell and the total number of grid points, the tool will track and display these. In addition, the gridding template may contain constraints on these parameters and will identify conflicts to the constraints. An application programming interface (API) is being constructed to provide easy and standardized access to the grid information model within the MMACE database. The grid tool will be built upon the API and will output the grid to the database for use by MMACE applications. The API will provide standardized facilities for applications to retrieve the grid
An important problem in the design of RF linacs is the coupling between the waveguide that feeds ... more An important problem in the design of RF linacs is the coupling between the waveguide that feeds RF power into the accelerator and the cavity through which the beam is being accelerated. The designer needs to know the coupling coefficient, the frequency shift, and the external Q due to the waveguide. In addition, the details of the field geometry in
: The material covered in this report consists of three general areas in which plasma physics pla... more : The material covered in this report consists of three general areas in which plasma physics plays a significant role in the modeling of radiation sources for the advanced simulation research program. The first is the description of a basic model for the implosion of a system of identical wires driven by a pulsed power generator. The second is a model for computing the linear ideal MHD instability growth rates for azimuthally symmetric, cylindrical Z pinch equilibria. This analyses includes both kink and sausage type perturbations of the equilibrium. The third area concerns the properties of magnetically insulated power feeds for driving imploding Z pinch loads.
This report covers the period June 1981 to June 1983, during which time investigations were condu... more This report covers the period June 1981 to June 1983, during which time investigations were conducted into several major topics concerning the behavior of an intense (multi-kiloampere) electron beam in the modified betatron electron accelerator. The modified betatron has been selected for experimental evaluation as a high-current electron accelerator. Theoretical support has been directed at identifying those phenomena which will most directly affect accelerator performance. To this end, research has been carried out in the following areas: (1) Transverse linear beam dynamics in time varying, azimuthally symmetric fields, (2) Effects of grad B theta induced drifts, (3) Orbital resonance effects due to small field errors, (4) Nonlinear effects, especially those due to non constant betatron field index, (5) Collective effects, especially the negative mass instability, and (6) Strongly focused systems.
The combination of a bumpy torus field and a conventional betatron field leads to an interesting ... more The combination of a bumpy torus field and a conventional betatron field leads to an interesting strongly focused, high-current accelerator configuration. The question of orbital stability of a test particle in such a device is discussed, and it is shown that the alternating gradient focusing in this accelerator can easily lead to greater than 20% bandwidth in allowed mismatch between the vertical magnetic field and the average beam particle energy.
The development of electron-positron linear colliders in the TeV energy range will be facilitated... more The development of electron-positron linear colliders in the TeV energy range will be facilitated by the development of high-power rf sources at frequencies above 2856 MHz. Present S-band technology, represented by the SLC, would require a length in excess of 50 km per linac to accelerate particles to energies above 1 TeV. By raising the rf driving frequency, the rf breakdown limit is increased, thereby allowing the length of the accelerators to be reduced. Currently available rf power sources set the realizable gradient limit in an rf linac at frequencies above S-band. This paper presents a model for the frequency scaling of linear colliders, with luminosity scaled in proportion to the square of the center-of-mass energy. Since wakefield effects are the dominant deleterious effect, a separate single-bunch simulation model is described which calculates the evolution of the beam bunch with specified wakefields, including the effects of using programmed phase positioning and Landau da...
Relativistic, cylindrical, rigid-rotor equilibria for electrons are developed in the beam frame, ... more Relativistic, cylindrical, rigid-rotor equilibria for electrons are developed in the beam frame, and the corresponding laboratory frame equilibria are obtained by Lorentz transformation. Limitations of the two-mass approximation are thus illuminated. A toroidal equilibrium is developed that is based on the two-mass approximation and expansion in terms of the ratio of minor to major radius. The toroidal equilibrium is shown to have no unstable kink-modes or no Kruskal-Shafranov current limit as in a Tokamak. Small variations in the toroidal magnetic field around the torus result in trapped electrons if they are injected with sufficient transverse energy. The presence of both trapped and untrapped electrons leads to two-stream instabilities. Some comparisons are made with HIPAC experiments and the recent torus experiments at MLI.
The grid generator tool for MMACE connects existing grid generator technology to the Research Eng... more The grid generator tool for MMACE connects existing grid generator technology to the Research Engineering Framework (REF). It will read geometry from the database and allow the user interactively to construct grids which meet the needs of MMACE application tools. The initial focus is on 2-D rectangular grids for existing MMACE applications such as particle-in-cell, magnet, and gun codes. The authors expect to show results from the grid tool running in a work-station environment. The tool provides capabilities for automatic or user-directed identification of key points of the geometry which need to be matched to the grid. From these grid markers, and templates containing the gridding strategy, the tool generates the entire grid. When aspects of the geometry move, the grid markers move with them, thus providing automated re-gridding. Since application run times are often affected by the size of the smallest cell and the total number of grid points, the tool will track and display thes...
This review of e+e− linear colliders Is for the most part tutorial, but It will also present some... more This review of e+e− linear colliders Is for the most part tutorial, but It will also present some new results that are summarized in Section 1 and discussed in more detail in Sections 4 and 5. The paper is restricted to colliders with SLAC-type linac structures. The scaling with frequency in the range from 8 to 20 GHz is studied for a 500 GeV on 500 GeV accelerator system of fixed length (2 × 3 km) and luminosity L = 1033 cm−2s−1, as presently being considered at Stanford. Two scenarios, one which is limited by beamstrahlung where the number of particles per bunch, N, is approximately constant and one in which N is proportional to wavelength λ, are investigated. While the peak rf power requirement for each feed decreases with frequency identically in both cases, average ac power decreases with ω in the first case but increases in the second. Gyroklystron design parameters are presented that would meet the peak power requirements in X-band.
Summary form only given, as follows. The ARGUS-ESP code has been used to calculate electromagneti... more Summary form only given, as follows. The ARGUS-ESP code has been used to calculate electromagnetic vacuum eigenmodes, including dispersion diagrams, for both standing-wave and traveling-wave devices. Slow-wave structures, as used in microwave devices, are readily modeled with this code. ARGUS-ESP gives the designer the ability to do numerical cold testing. ARGUS is a fully 3D electromagnetic suite of codes that share a common framework. This common framework, across several methods of solution, gives ARGUS the ability to model complex structures in various ways. The suite includes electromagnetic eigenmode (ESP), time-domain, and single-frequency (or driven-frequency) models, as well as electrostatic models. Additionally, particle-in-cell (PIC) models are included in both time-domain and equilibrium (gun) modes. For this presentation, the ARGUS electromagnetic eigenmode solver, ESP, is featured. This solver gives the user the capability to calculate cavity modes for general, arbitra...
IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science. 26th IEEE International Conference (Cat. No.99CH36297), 2000
ABSTRACT Summary form only given, as follows. The cold-test and large-signal simulator (CTLSS) co... more ABSTRACT Summary form only given, as follows. The cold-test and large-signal simulator (CTLSS) code is a three-dimensional simulation tool developed specifically for the modeling of vacuum electron devices. It is a three-dimensional resonant electromagnetic frequency-domain code coupled to the CHRISTINE large-signal model. This paper will describe new results in the application of CTLSS to design calculations for slow-wave devices. Current directions for CTLSS development will also be described. Simulations of helix TWTs are presented that demonstrate a methodology consisting of using CHRTSTINE for parametric optimization, followed by CTLSS cold-test calculations of the CHRISTINE optimum to capture the effects of real geometry and real materials on the dispersion and impedance of the helix device with support rods. As a final step, CHRISTINE is exercised using the cold-test parameters from CTLSS to compute the consequences of materials and geometry for device performance
ARGUS is an integrated, 3-D, volumetric simulation model for systems involving electric and magne... more ARGUS is an integrated, 3-D, volumetric simulation model for systems involving electric and magnetic fields and charged particles, including materials embedded in the simulation region. The code offers the capability to carry out time domain and frequency domain electromagnetic simulations of complex physical systems. ARGUS offers a boolean solid model structure input capability that can include essentially arbitrary structures on
Proceedings of the 1989 IEEE Particle Accelerator Conference, . 'Accelerator Science and Technology, 1989
Argus is a system of three-dimensional codes which share the same utilities for structure input a... more Argus is a system of three-dimensional codes which share the same utilities for structure input and grid generation, memory management, data handling, and diagnostics. The field module of Argus can solve for electrostatic fields or for the complete electromagnetic fields in either the frequency or time domain. This module can be used as a stand-alone code for impedance and other
Uploads
Papers by A. Mondelli