Beam-envelope calculations of space-charge loaded beams in MeV dc ion-implantation facilities

International Nuclear Information System (INIS)

Urbanus, W.H.; Bannenberg, J.G.; Doorn, S.; Saris, F.W.; Koudijs, R.; Dubbelman, P.; Koelewijn, W.

1989-01-01

MeV dc ion accelerators are being developed that can deliver a beam current up to several hundred micro-amperes. At the low-energy part of the accelerator, the beam transport is space-charge dominated rather than emittance dominated. A system of differential equations has been derived, based on the Kapchinski-Vladimirski equations, which describe the envelope of a space-charge loaded ion beam, taking a longitudinal electrical field in an accelerating tube into account. The equations have been used to design the accelerator of a high-current 1 MV heavy-ion implantation facility. Furthermore, the design of a 2 MV accelerator is presented, which is used for analyzing techniques such as RBS and PIXE. Both facilities are based on single-ended Van de Graaff accelerators. (orig.)

Emittance growth in displaced, space-charge-dominated beams with energy spread

International Nuclear Information System (INIS)

Barnard, J.J.; Miller, J.; Haber, I.

1993-01-01

Conversion of transverse energy associated with the coherent motion of displaced beams into thermal energy, and thus emittance growth, has been predicted theoretically by a number of authors. Here, they authors show, using 2-D particle-in-cell simulations, that emittance growth is inhibited for tune depressed beams, if the energy spread of the beam is not too large. Further, using a uniform density model to calculate the space charge field of the beam, they numerically determine the criteria for emittance growth as a function of tune depression, energy spread, and beam displacement over a wide range of parameters. A theoretical interpretation of the results is presented. This study is applicable to an inertial fusion reactor driven by a heavy ion accelerator

Angular-momentum-dominated electron beams and flat-beam generation

International Nuclear Information System (INIS)

Sun, Yin-e

2005-01-01

In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, an emittance ratio of 100 ± 5 was measured, with the smaller normalized root-mean-square emittance around 0.4 mm-mrad. Effects limiting the flat-beam emittance ratio are investigated, such as the chromatic effects in the round-to-flat beam transformer, asymmetry in the initial angular-momentum-dominated beam, and space-charge effects. The most important limiting factor turns out to be the uncorrelated emittance growth caused by space charge when the beam energy is low, for example, in the rf gun area. As a result of such emittance growth prior to the round-to-flat beam transformer, the emittance ratio achievable in simulation decreases from orders of thousands to

Angular-momentum-dominated electron beams and flat-beam generation

Energy Technology Data Exchange (ETDEWEB)

Sun, Yin-e [Univ. of Chicago, IL (United States)

2005-06-01

In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, an emittance ratio of 100 ± 5 was measured, with the smaller normalized root-mean-square emittance around 0.4 mm-mrad. Effects limiting the flat-beam emittance ratio are investigated, such as the chromatic effects in the round-to-flat beam transformer, asymmetry in the initial angular-momentum-dominated beam, and space-charge effects. The most important limiting factor turns out to be the uncorrelated emittance growth caused by space charge when the beam energy is low, for example, in the rf gun area. As a result of such emittance growth prior to the round-to-flat beam transformer, the emittance ratio achievable in simulation decreases from orders of thousands to

Space-charge compensation of highly charged ion beam from laser ion source

International Nuclear Information System (INIS)

Kondrashev, S.A.; Collier, J.; Sherwood, T.R.

1996-01-01

The problem of matching an ion beam delivered by a high-intensity ion source with an accelerator is considered. The experimental results of highly charged ion beam transport with space-charge compensation by electrons are presented. A tungsten thermionic cathode is used as a source of electrons for beam compensation. An increase of ion beam current density by a factor of 25 is obtained as a result of space-charge compensation at a distance of 3 m from the extraction system. The process of ion beam space-charge compensation, requirements for a source of electrons, and the influence of recombination losses in a space-charge-compensated ion beam are discussed. (author)

Space-charge-limit instabilities in electron beams

International Nuclear Information System (INIS)

Coutsias, E.A.; Sullivan, D.J.

1983-01-01

The method of characteristics and multiple-scaling perturbation techniques are used to study the space-charge instability of electron beams. It is found that the stable oscillating state (virtual cathode) created when the space-charge limit is exceeded is similar to a collisionless shock wave. The oscillatory solution originates at the bifurcation point of two unstable steady states. Complementary behavior (virtual anode) results when an ion beam exceeds its space-charge limit. The virtual cathode can also exist in the presence of a neutralizing heavy-ion background. The Pierce instability, where the electron and ion charge densities are equal, is a special case of this broader class. Estimates of the nonlinear growth rate of the instability at the space-charge limit are given

Low-energy beam transport using space-charge lenses

International Nuclear Information System (INIS)

Meusel, O.; Bechtold, A.; Pozimski, J.; Ratzinger, U.; Schempp, A.; Klein, H.

2005-01-01

Space-charge lenses (SCL) of the Gabor type provide strong cylinder symmetric focusing for low-energy ion beams using a confined nonneutral plasma. They need modest magnetic and electrostatic field strength and provide a short installation length when compared to conventional LEBT-lenses like quadrupoles and magnetic solenoids. The density distribution of the enclosed space charge within the Gabor lens is given by the confinement in transverse and longitudinal directions. In the case of a positive ion beam, the space charge of the confined electron cloud may cause an overcompensation of the ion beam space-charge force and consequently focuses the beam. To investigate the capabilities of an SCL double-lens system for ion beam into an RFQ, a test injector was installed at IAP and put into operation successfully. Furthermore, to study the focusing capabilities of this lens at beam energies up to 500 keV, a high-field Gabor lens was built and installed downstream of the RFQ. Experimental results of the beam injection into the RFQ are presented as well as those of these first bunched beam-focusing tests with the 110 A keV He + beam

Space charge effect in an accelerated beam

Directory of Open Access Journals (Sweden)

G. Stupakov

2008-01-01

Full Text Available It is usually assumed that the space charge effects in relativistic beams scale with the energy of the beam as γ^{-2}, where γ is the relativistic factor. We show that for a beam accelerated in the longitudinal direction there is an additional space charge effect in free space that scales as E/γ, where E is the accelerating field. This field has the same origin as the “electromagnetic mass of the electron” discussed in textbooks on electrodynamics. It keeps the balance between the kinetic energy of the beam and the energy of the electromagnetic field of the beam. We then consider the effect of this field on a beam generated in an rf gun and calculate the energy spread produced by this field in the beam.

Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

International Nuclear Information System (INIS)

Paret, Stefan

2010-01-01

A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

Transverse Schottky spectra and beam transfer functions of coasting ion beams with space charge

Energy Technology Data Exchange (ETDEWEB)

Paret, Stefan

2010-02-22

A study of the transverse dynamics of coasting ion beams with moderate space charge is presented in this work. From the dispersion relation with linear space charge, an analytic model describing the impact of space charge on transverse beam transfer functions (BTFs) and the stability limits of a beam is derived. The dielectric function obtained in this way is employed to describe the transverse Schottky spectra with linear space charge as well. The difference between the action of space charge and impedances is highlighted. The setup and the results of an experiment performed in the heavy ion synchrotron SIS-18 at GSI to detect space-charge effects at different beam intensities are explicated. The measured transverse Schottky spectra and BTFs are compared with the linear space-charge model. The stability diagrams constructed from the BTFs are presented. The space-charge parameters evaluated from the Schottky and BTF measurements are compared with estimations based on measured beam parameters. The impact of collective effects on the Schottky and BTF diagnostics is also investigated through numerical simulations. For this purpose the self-field of beams with linear and non-linear transverse density-distributions is computed on a twodimensional grid. The noise of the random particle distribution causes fluctuations of the dipole moment of the beam which produce the Schottky spectrum. BTFs are simulated by exciting the beam with transverse kicks. The simulation results are used to verify the space-charge model. (orig.)

Demonstration of cathode emittance dominated high bunch charge beams in a DC gun-based photoinjector

Energy Technology Data Exchange (ETDEWEB)

Gulliford, Colwyn, E-mail: cg248@cornell.edu; Bartnik, Adam, E-mail: acb20@cornell.edu; Bazarov, Ivan; Dunham, Bruce; Cultrera, Luca [CLASSE, Cornell University, 161 Synchrotron Drive Ithaca, New York 14853-8001 (United States)

2015-03-02

We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (≥100 pC) beams produced in the DC gun-based Cornell energy recovery linac photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittances measured at 9–9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of delivering beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs and Free Electron Lasers.

Nonlinear space charge effect of bunched beam in linac

International Nuclear Information System (INIS)

Chen Yinbao

1992-02-01

The nonlinear space charge effect due to the nonuniform particle density distribution in bunched beam of a linac is discussed. The formulae of nonlinear space charge effect and nonlinear focusing forces were derived for the bunched beam with Kapchinskij-Vladimirskij (K-V) distribution, waterbag (WB) distribution, parabolic (PA) distribution, and Gauss (GA) distribution in both of the space charge disk model and space charge cylinder model in the waveguide of a linac

The role of space charge compensation for ion beam extraction and ion beam transport (invited)

International Nuclear Information System (INIS)

Spädtke, Peter

2014-01-01

Depending on the specific type of ion source, the ion beam is extracted either from an electrode surface or from a plasma. There is always an interface between the (almost) space charge compensated ion source plasma, and the extraction region in which the full space charge is influencing the ion beam itself. After extraction, the ion beam is to be transported towards an accelerating structure in most cases. For lower intensities, this transport can be done without space charge compensation. However, if space charge is not negligible, the positive charge of the ion beam will attract electrons, which will compensate the space charge, at least partially. The final degree of Space Charge Compensation (SCC) will depend on different properties, like the ratio of generation rate of secondary particles and their loss rate, or the fact whether the ion beam is pulsed or continuous. In sections of the beam line, where the ion beam is drifting, a pure electrostatic plasma will develop, whereas in magnetic elements, these space charge compensating electrons become magnetized. The transport section will provide a series of different plasma conditions with different properties. Different measurement tools to investigate the degree of space charge compensation will be described, as well as computational methods for the simulation of ion beams with partial space charge compensation

Equivalent circuit modeling of space charge dominated magnetically insulated transmission lines

Energy Technology Data Exchange (ETDEWEB)

Hiraoka, Kazuki; Nakajima, Mitsuo; Horioka, Kazuhiko

1997-12-31

A new equivalent circuit model for space charge dominated MITLs (Magnetically Insulated Transmission Lines) was developed. MITLs under high power operation are dominated with space charge current flowing between anode and cathode. Conventional equivalent circuit model does not account for space charge effects on power flow. The model was modified to discuss the power transportation through the high power MITLs. With this model, it is possible to estimate the effects of space charge current on the power flow efficiency, without using complicated particle code simulations. (author). 3 figs., 3 refs.

Analysis of beam envelope by transverse space charge effect

International Nuclear Information System (INIS)

Toyama, Shin'ichi

1997-09-01

It is important for high current accelerators to estimate the contribution of the space charge effect to keep the beam off its beak up. The application of an envelope equation is examined in previous report in which the beam is just coasting beam (non accelerating). The analysis of space charge effect is necessary for the comparison in coming accelerator test in PNC. In order to evaluate the beam behavior in high current, the beam dynamics and beam parameters which are input to the equation for the evaluation are developed and make it ready to estimate the beam transverse dynamics by the space charge. The estimate needs to have enough accuracy for advanced code calculation. After the preparation of the analytic expression of transverse motion, the non-linear differential equation of beam dynamics is solved by a numerical method on a personal computer. The beam envelope from the equation is estimated by means of the beam emittance, current and energy. The result from the analysis shows that the transverse beam broadening is scarecely small around the beam current value of PNC design. The contribution to the beam broadening of PNC linac comes from its beam emittance. The beam broadening in 100 MeV case is almost negligible in the view of transverse space charge effect. Therefore, the electron beam is stable up to 10 A order in PNC linac design. Of course, the problem for RF supply is out of consideration here. It is important to estimate other longitudinal effect such as beam bunch effect which is lasting unevaluated. (author)

Longitudinal holes in debunched particle beams in storage rings, perpetuated by space-charge forces

Directory of Open Access Journals (Sweden)

Shane Koscielniak

2001-04-01

Full Text Available Stationary, self-consistent, and localized longitudinal density perturbations on an unbunched charged-particle beam, which are solutions of the nonlinearized Vlasov-Poisson equation, have recently received some attention. In particular, we address the case that space charge is the dominant longitudinal impedance and the storage ring operates below transition energy so that the negative mass instability is not an explanation for persistent beam structure. Under the customary assumption of a bell-shaped steady-state distribution, about which the expansion is made, the usual wave theory of Keil and Schnell for perturbations on unbunched beams predicts that self-sustaining perturbations are possible only (below transition if the impedance is inductive (or resistive or if the bell shape is inverted. Space charge gives a capacitive impedance. Nevertheless, we report numerous experimental measurements made at the CERN Proton Synchrotron Booster that plainly show the longevity of holelike structures in coasting beams. We shall also report on computer simulations of boosterlike beams that provide compelling evidence that it is space-charge force which perpetuates the holes. We shall show that the localized solitonlike structures, i.e., holes, decouple from the steady-state distribution and that they are simple solutions of the nonlinearized time-independent Vlasov equation. We have derived conditions for stationarity of holes that satisfy the requirement of self-consistency; essentially, the relation between the momentum spread and depth of the holes is given by the Hamiltonian—with the constraint that the phase-space density be high enough to support the solitons. The stationarity conditions have scaling laws similar to the Keil-Schnell criteria except that the charge and momentum spread of the hole replaces that of the beam.

Determination of charged particle beam parameters with taking into account of space charge

International Nuclear Information System (INIS)

Ishkhanov, B.S.; Poseryaev, A.V.; Shvedunov, V.I.

2005-01-01

One describes a procedure to determine the basic parameters of a paraxial axially-symmetric beam of charged particles taking account of space charge contribution. The described procedure is based on application of the general equation for beam envelope. Paper presents data on its convergence and resistance to measurement errors. The position determination error of crossover (stretching) and radius of beam in crossover is maximum 15% , while the emittance determination error depends on emittance and space charge correlation. The introduced procedure was used to determine parameters of the available electron gun 20 keV energy beam with 0.64 A current. The derived results turned to agree closely with the design parameters [ru

Course Notes: United States Particle Accelerator School Beam Physics with Intense Space-Charge

International Nuclear Information System (INIS)

Barnard, J.J.; Lund, S.M.

2008-01-01

The purpose of this course is to provide a comprehensive introduction to the physics of beams with intense space charge. This course is suitable for graduate students and researchers interested in accelerator systems that require sufficient high intensity where mutual particle interactions in the beam can no longer be neglected. This course is intended to give the student a broad overview of the dynamics of beams with strong space charge. The emphasis is on theoretical and analytical methods of describing the acceleration and transport of beams. Some aspects of numerical and experimental methods will also be covered. Students will become familiar with standard methods employed to understand the transverse and longitudinal evolution of beams with strong space charge. The material covered will provide a foundation to design practical architectures. In this course, we will introduce you to the physics of intense charged particle beams, focusing on the role of space charge. The topics include: particle equations of motion, the paraxial ray equation, and the Vlasov equation; 4-D and 2-D equilibrium distribution functions (such as the Kapchinskij-Vladimirskij, thermal equilibrium, and Neuffer distributions), reduced moment and envelope equation formulations of beam evolution; transport limits and focusing methods; the concept of emittance and the calculation of its growth from mismatches in beam envelope and from space-charge non-uniformities using system conservation constraints; the role of space-charge in producing beam halos; longitudinal space-charge effects including small amplitude and rarefaction waves; stable and unstable oscillation modes of beams (including envelope and kinetic modes); the role of space charge in the injector; and algorithms to calculate space-charge effects in particle codes. Examples of intense beams will be given primarily from the ion and proton accelerator communities with applications from, for example, heavy-ion fusion, spallation

Space Charge Correction on Emittance Measurement of Low Energy Electron Beams

Energy Technology Data Exchange (ETDEWEB)

Treado, Colleen J.; /Massachusetts U., Amherst

2012-09-07

The goal of any particle accelerator is to optimize the transport of a charged particle beam along a set path by confining the beam to a small region close to the design trajectory and directing it accurately along the beamline. To do so in the simplest fashion, accelerators use a system of magnets that exert approximately linear electromagnetic forces on the charged beam. These electromagnets bend the beam along the desired path, in the case of bending magnets, and constrain the beam to the desired area through alternating focusing and defocusing effects, in the case of quadrupole magnets. We can model the transport of such a beam through transfer matrices representing the actions of the various beamline elements. However, space charge effects, produced from self electric fields within the beam, defocus the beam and must be accounted for in the calculation of beam emittance. We present below the preliminary results of a MATLAB code built to model the transport of a charged particle beam through an accelerator and measure the emittance under the influence of space charge effects. We demonstrate the method of correctly calculating the emittance of a beam under space charge effects using a least square fit to determine the initial properties of the beam given the beam size measured at a specific point after transport.

First heavy ion beam tests with a superconducting multigap CH cavity

Science.gov (United States)

Barth, W.; Aulenbacher, K.; Basten, M.; Busch, M.; Dziuba, F.; Gettmann, V.; Heilmann, M.; Kürzeder, T.; Miski-Oglu, M.; Podlech, H.; Rubin, A.; Schnase, A.; Schwarz, M.; Yaramyshev, S.

2018-02-01

Very compact accelerating-focusing structures, as well as short focusing periods, high accelerating gradients and short drift spaces are strongly required for superconducting (sc) accelerator sections operating at low and medium energies for continuous wave (cw) heavy ion beams. To keep the GSI-super heavy element (SHE) program competitive on a high level and even beyond, a standalone sc cw linac (Helmholtz linear accelerator) in combination with the GSI high charge state injector (HLI), upgraded for cw operation, is envisaged. Recently the first linac section (financed by Helmholtz Institute Mainz (HIM) and GSI) as a demonstration of the capability of 217 MHz multigap crossbar H-mode structures (CH) has been commissioned and extensively tested with heavy ion beam from the HLI. The demonstrator setup reached acceleration of heavy ions up to the design beam energy. The required acceleration gain was achieved with heavy ion beams even above the design mass to charge ratio at high beam intensity and full beam transmission. This paper presents systematic beam measurements with varying rf amplitudes and phases of the CH cavity, as well as phase space measurements for heavy ion beams with different mass to charge ratio. The worldwide first and successful beam test with a superconducting multigap CH cavity is a milestone of the R&D work of HIM and GSI in collaboration with IAP in preparation of the HELIAC project and other cw-ion beam applications.

Space Charge Effect in the Sheet and Solid Electron Beam

Science.gov (United States)

Song, Ho Young; Kim, Hyoung Suk; Ahn, Saeyoung

1998-11-01

We analyze the space charge effect of two different types of electron beam ; sheet and solid electron beam. Electron gun simulations are carried out using shadow and control grids for high and low perveance. Rectangular and cylindrical geometries are used for sheet and solid electron beam in planar and disk type cathode. The E-gun code is used to study the limiting current and space charge loading in each geometries.

PAL-XFEL cavity beam position monitor pick-up design and beam test

Energy Technology Data Exchange (ETDEWEB)

Lee, Sojeong, E-mail: sojung8681@postech.ac.kr; Park, Young Jung; Kim, Changbum; Kim, Seung Hwan; Shin, Dong Cheol; Han, Jang-Hui; Ko, In Soo

2016-08-11

As an X-ray Free Electron Laser, PAL-XFEL is about to start beam commissioning. X-band cavity beam position monitor (BPM) is used in the PAL-XFEL undulator beam line. Prototypes of cavity BPM pick-up were designed and fabricated to test the RF characteristics. Also, the beam test of a cavity BPM pick-up was done in the Injector Test Facility (ITF). In the beam test, the raw signal properties of the cavity BPM pick-up were measured at a 200 pC bunch charge. According to the RF test and beam test results, the prototype cavity BPM pick-up design was confirmed to meet the requirements of the PAL-XFEL cavity BPM system.

Method and split cavity oscillator/modulator to generate pulsed particle beams and electromagnetic fields

Science.gov (United States)

Clark, M. Collins; Coleman, P. Dale; Marder, Barry M.

1993-01-01

A compact device called the split cavity modulator whose self-generated oscillating electromagnetic field converts a steady particle beam into a modulated particle beam. The particle beam experiences both signs of the oscillating electric field during the transit through the split cavity modulator. The modulated particle beam can then be used to generate microwaves at that frequency and through the use of extractors, high efficiency extraction of microwave power is enabled. The modulated beam and the microwave frequency can be varied by the placement of resistive wires at nodes of oscillation within the cavity. The short beam travel length through the cavity permit higher currents because both space charge and pinching limitations are reduced. The need for an applied magnetic field to control the beam has been eliminated.

A superconducting radio-frequency cavity for manipulating the phase space of pion beams at LAMPF

Energy Technology Data Exchange (ETDEWEB)

O' Donnell, J.M.; Davis, J.; DeHaven, R.A.; Gray, E.; Johnson, R.; Lomax, R.E.; McCloud, B.J.; McGill, J.A.; Morris, C.L.; Novak, J.; Rusnak, B.; Tubb, G. (Los Alamos National Lab., Los Alamos, NM (United States)); Applegate, J.M.; Averett, T.D.; Beck, J.; Ritchie, B.G. (Arizona State Univ., Tempe, AZ (United States)); Haebel, E. (CERN, Geneva (Switzerland)); Kiehlmann, D.; Klein, U.; Peniger, M.; Schaefer, P.; Vogel, H. (Siemens AG, Accelerator and Magnet Technology, Bergisch Gladbach (Germany)); Ward, H.; Moore, C.F. (Univ. of Texas, Austin, TX (United States))

1992-07-15

The SCRUNCHER is a superconducting radio-frequency cavity for manipulating the longitudinal phase space of the secondary pion beam from the low energy pion channel at LAMPF. Test results of the cavity performance and initial results from in-beam tests are presented. (orig.).

A superconducting radio-frequency cavity for manipulating the phase space of pion beams at LAMPF

Science.gov (United States)

O'Donnell, J. M.; Davis, J.; DeHaven, R. A.; Gray, E.; Johnson, R.; Lomax, R. E.; McCloud, B. J.; McGill, J. A.; Morris, C. L.; Novak, J.; Rusnak, B.; Tubb, G.; Applegate, J. M.; Averett, T. D.; Beck, J.; Ritchie, B. G.; Haebel, E.; Kiehlmann, D.; Klein, U.; Peiniger, M.; Schäfer, P.; Vogel, H.; Ward, H.; Fred Moore, C.

1992-07-01

The SCRUNCHER is a superconducting radio-frequency cavity for manipulating the longitudinal phase space of the secondary pion beam from the low energy pion channel at LAMPF. Test results of the cavity performance and initial results from in-beam tests are presented.

EBQ code: Transport of space-charge beams in axially symmetric devices

Science.gov (United States)

Paul, A. C.

1982-11-01

Such general-purpose space charge codes as EGUN, BATES, WODF, and TRANSPORT do not gracefully accommodate the simulation of relativistic space-charged beams propagating a long distance in axially symmetric devices where a high degree of cancellation has occurred between the self-magnetic and self-electric forces of the beam. The EBQ code was written specifically to follow high current beam particles where space charge is important in long distance flight in axially symmetric machines possessing external electric and magnetic field. EBQ simultaneously tracks all trajectories so as to allow procedures for charge deposition based on inter-ray separations. The orbits are treated in Cartesian geometry (position and momentum) with z as the independent variable. Poisson's equation is solved in cylindrical geometry on an orthogonal rectangular mesh. EBQ can also handle problems involving multiple ion species where the space charge from each must be included. Such problems arise in the design of ion sources where different charge and mass states are present.

EBQ code: transport of space-charge beams in axially symmetric devices

International Nuclear Information System (INIS)

Paul, A.C.

1982-11-01

Such general-purpose space charge codes as EGUN, BATES, WOLF, and TRANSPORT do not gracefully accommodate the simulation of relativistic space-charged beams propagating a long distance in axially symmetric devices where a high degree of cancellation has occurred between the self-magnetic and self-electric forces of the beam. The EBQ code was written specifically to follow high current beam particles where space charge is important in long distance flight in axially symmetric machines possessing external electric and magnetic field. EBQ simultaneously tracks all trajectories so as to allow procedures for charge deposition based on inter-ray separations. The orbits are treated in Cartesian geometry (position and momentum) with z as the independent variable. Poisson's equation is solved in cylindrical geometry on an orthogonal rectangular mesh. EBQ can also handle problems involving multiple ion species where the space charge from each must be included. Such problems arise in the design of ion sources where different charge and mass states are present

Effect of ion compensation of the beam space charge on gyrotron operation

Energy Technology Data Exchange (ETDEWEB)

Fokin, A. P.; Glyavin, M. Yu. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Nusinovich, G. S. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)

2015-04-15

In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.

A modified space charge routine for high intensity bunched beams

International Nuclear Information System (INIS)

Lapostolle, P.; Lombardi, A.M.; Tanke, E.; Valero, S.; Garnett, R.W.; Wangler, T.P.

1996-01-01

A new routine and a computer code (DYNAC) for the calculation of space charge densities in a new generation of linear accelerators for various industrial applications is presented. The new beam dynamics method used in this code, employs a set of quasi-Liouvillian equations, allowing beam dynamics computations in long and complex structures for electrons, as well as protons and ions. With this new beam dynamics method, the coordinates of particles are known at any position in the accelerating elements, allowing multistep space charge calculations. (K.A.)

Three-dimensional space charge distribution measurement in electron beam irradiated PMMA

International Nuclear Information System (INIS)

Imaizumi, Yoichi; Suzuki, Ken; Tanaka, Yasuhiro; Takada, Tatsuo

1996-01-01

The localized space charge distribution in electron beam irradiated PMMA was investigated using pulsed electroacoustic method. Using a conventional space charge measurement system, the distribution only in the depth direction (Z) can be measured assuming the charges distributed uniformly in the horizontal (X-Y) plane. However, it is difficult to measure the distribution of space charge accumulated in small area. Therefore, we have developed the new system to measure the three-dimensional space charge distribution using pulsed electroacoustic method. The system has a small electrode with a diameter of 1mm and a motor-drive X-Y stage to move the sample. Using the data measured at many points, the three-dimensional distribution were obtained. To estimate the system performance, the electron beam irradiated PMMA was used. The electron beam was irradiated from transmission electron microscope (TEM). The depth of injected electron was controlled using the various metal masks. The measurement results were compared with theoretically calculated values of electron range. (author)

Experiments on ion space-charge neutralization with pulsed electron beams

Energy Technology Data Exchange (ETDEWEB)

Herleb, U; Riege, H [CERN LHC-Division, Geneva (Switzerland)

1997-12-31

The method of space-charge neutralization of heavy ion beams with electron beam pulses generated with electron guns incorporating ferroelectric cathodes was investigated experimentally. Several experiments are described, the results of which prove that the intensity of selected ion beam parts with defined charge states generated in a laser ion source can be increased by an order of magnitude. For elevated charge states the intensity amplification is more significant and may reach a factor of 4 for highly charged ions from an Al target. (author). 7 figs., 3 -refs.

Space charge beam dynamics studies for a pulsed spallation source accelerator

Energy Technology Data Exchange (ETDEWEB)

Cho, Y.; Lessner, E.

1995-12-31

Feasibility studies for 2-GeV, 1-MW and 10-GeV, 5-MW rapid cycling synchrotrons (RCS) for spallation neutron sources have been completed. Both synchrotrons operate at a repetition rate of 30 Hz, and accelerate 1.04 {times} 10{sup 14} protons per pulse. The injection energy of the 2-GeV ring is 400 MeV, and the 10-GeV RCS accepts the beam from the 2-GeV machine. Work performed to-date includes calculation of the longitudinal space charge effects in the 400-MeV beam transfer line, and of both longitudinal and transverse space charge effects during the injection, capture and acceleration processes in the two rings. Results of space charge calculations in the rings led to proper choices of the working points and of rf voltage programs that prevents beam loss. Space charge effects in the 2-GeV synchrotron, in both transverse and longitudinal phase space, have major impact on the design due to the fact that the injection energy is 400 MeV. The design achieves the required performance while alleviating harmful effects due to space charge.

Beam emittance and the effects of the rf, space charge and wake fields: Application to the ATF photoelectron beam

International Nuclear Information System (INIS)

Parsa, Z.

1991-01-01

Laser driven photoelectron guns are of interest for use in new methods of accelerations, future development of Linear Colliders and new experiments such as Free Electron laser (IFEL). Such guns are potential source of low emittance-high current and short bunch length electron beams, where the emitted electrons are accelerated quickly to a relativistic energy by a strong rf, electric field in the cavity. We present a brief overview of the beam dynamic studies, e.g. emittance for the Brookhaven National Laboratory (BNL) ATF high brightness photocathode radio frequency gun (now in operation), and show the effects of the rf, Space Charge, and Wake fields on the photoelectrons. 4 refs., 7 figs

Space-charge limits on the transport of ion beams in a long alternating gradient system

International Nuclear Information System (INIS)

Tiefenback, M.G.

1986-11-01

We have experimentally studied the space-charge-dominated transport of ion beams in an alternating-gradient channel, without acceleration. We parameterize the focusing strength in terms of the zero-current ''betatron'' oscillation phase advance rate, σ 0 (degrees per focusing period). We have investigated the conditions for ''stability'', defined as the constancy of the total current and phase space area of the beam during transport. We find that the beam may be transported with neither loss of current nor growth in phase area if σ 0 0 . In this regime, the space-charge repulsive force can counter 98-99% of the externally applied focusing field, and the oscillation frequency of the beam particles can be depressed by self-forces to almost a factor of 10 below the zero-current value, limited only by the optical quality of our ion source. For σ 0 > 90 0 , we find that collective interactions bound the maintainable density of the beam, and we present a simple, semi-empirical characterization for stability, within our ability to distinguish the growth rate from zero in our apparatus. Our channel comprises 87 quadrupole lenses, 5 of which are used to prepare the beam for injection into the non-azimuthally-symmetric focusing channel

Minimization of power consumption during charging of superconducting accelerating cavities

Energy Technology Data Exchange (ETDEWEB)

Bhattacharyya, Anirban Krishna, E-mail: anirban.bhattacharyya@physics.uu.se; Ziemann, Volker; Ruber, Roger; Goryashko, Vitaliy

2015-11-21

The radio frequency cavities, used to accelerate charged particle beams, need to be charged to their nominal voltage after which the beam can be injected into them. The standard procedure for such cavity filling is to use a step charging profile. However, during initial stages of such a filling process a substantial amount of the total energy is wasted in reflection for superconducting cavities because of their extremely narrow bandwidth. The paper presents a novel strategy to charge cavities, which reduces total energy reflection. We use variational calculus to obtain analytical expression for the optimal charging profile. Energies, reflected and required, and generator peak power are also compared between the charging schemes and practical aspects (saturation, efficiency and gain characteristics) of power sources (tetrodes, IOTs and solid state power amplifiers) are also considered and analysed. The paper presents a methodology to successfully identify the optimal charging scheme for different power sources to minimize total energy requirement.

Minimization of power consumption during charging of superconducting accelerating cavities

International Nuclear Information System (INIS)

Bhattacharyya, Anirban Krishna; Ziemann, Volker; Ruber, Roger; Goryashko, Vitaliy

2015-01-01

The radio frequency cavities, used to accelerate charged particle beams, need to be charged to their nominal voltage after which the beam can be injected into them. The standard procedure for such cavity filling is to use a step charging profile. However, during initial stages of such a filling process a substantial amount of the total energy is wasted in reflection for superconducting cavities because of their extremely narrow bandwidth. The paper presents a novel strategy to charge cavities, which reduces total energy reflection. We use variational calculus to obtain analytical expression for the optimal charging profile. Energies, reflected and required, and generator peak power are also compared between the charging schemes and practical aspects (saturation, efficiency and gain characteristics) of power sources (tetrodes, IOTs and solid state power amplifiers) are also considered and analysed. The paper presents a methodology to successfully identify the optimal charging scheme for different power sources to minimize total energy requirement.

Space-charge dynamics of polymethylmethacrylate under electron beam irradiation

CERN Document Server

Gong, H; Ong, C K

1997-01-01

Space-charge dynamics of polymethylmethacrylate (PMMA) under electron beam irradiation has been investigated employing a scanning electron microscope. Assuming a Gaussian space-charge distribution, the distribution range (sigma) has been determined using a time-resolved current method in conjunction with a mirror image method. sigma is found to increase with irradiation time and eventually attain a stationary value. These observations have been discussed by taking into account radiation-induced conductivity and charge mobility. (author)

Beam halo in high-intensity beams

International Nuclear Information System (INIS)

Wangler, T.P.

1993-01-01

In space-charge dominated beams the nonlinear space-charge forces produce a filamentation pattern, which in projection to the 2-D phase spaces results in a 2-component beam consisting of an inner core and a diffuse outer halo. The beam-halo is of concern for a next generation of cw, high-power proton linacs that could be applied to intense neutron generators for nuclear materials processing. The author describes what has been learned about beam halo and the evolution of space-charge dominated beams using numerical simulations of initial laminar beams in uniform linear focusing channels. Initial results are presented from a study of beam entropy for an intense space-charge dominated beam

Modeling beams with elements in phase space

International Nuclear Information System (INIS)

Nelson, E.M.

1998-01-01

Conventional particle codes represent beams as a collection of macroparticles. An alternative is to represent the beam as a collection of current carrying elements in phase space. While such a representation has limitations, it may be less noisy than a macroparticle model, and it may provide insights about the transport of space charge dominated beams which would otherwise be difficult to gain from macroparticle simulations. The phase space element model of a beam is described, and progress toward an implementation and difficulties with this implementation are discussed. A simulation of an axisymmetric beam using 1d elements in phase space is demonstrated

Emittance growth due to space charge compensation and beam intensity instabilities in negative ion beams

Directory of Open Access Journals (Sweden)

C. A. Valerio-Lizarraga

2018-03-01

Full Text Available The need to extract the maximum beam intensity with low transversal emittance often comes with the drawback of operating the ion source to limits where beam current instabilities arise, such fluctuations can change the beam properties producing a mismatch in the following sections of the machine. The space charge compensation (SCC generated by the beam particles colliding with the residual gas reaches a steady state after a build-up time. This paper shows how once in the steady state, the beam ends with a transversal emittance value bigger than the case without compensation. In addition, we study how the beam intensity variation can disturb the SCC dynamics and its impact on the beam properties. The results presented in this work come from 3-D simulations using tracking codes taking into account the secondary ions to estimate the degree of the emittance growth due to space charge and SCC.

Modeling space charge in beams for heavy-ion fusion

International Nuclear Information System (INIS)

Sharp, W.M.

1995-01-01

A new analytic model is presented which accurately estimates the radially averaged axial component of the space-charge field of an axisymmetric heavy-ion beam in a cylindrical beam pipe. The model recovers details of the field near the beam ends that are overlooked by simpler models, and the results compare well to exact solutions of Poisson's equation. Field values are shown for several simple beam profiles and are compared with values obtained from simpler models

Space charge compensation on the low energy beam transport of Linac4

CERN Document Server

AUTHOR|(SzGeCERN)733270; Scrivens, Richard; Jesus Castillo, Santos

Part of the upgrade program in the injector chains of the CERN accelerator complex is the replacement of the the proton accelerator Linac2 for the brand new Linac4 which will accelerate H$^-$ and its main goal is to increase the beam intensity in the next sections of the LHC accelerator chain. The Linac4 is now under commissioning and will use several ion sources to produce high intensity unbunched H$^-$ beams with different properties, and the low energy beam transport (LEBT) is the system in charge of match all these different beams to the Radio frequency quadrupole (RFQ). The space charge forces that spread the beam ions apart of each other and cause emittance growth limits the maximum intensity that can be transported in the LEBT, but the space charge of intense unbunched ion beams can be compensated by the generated ions by the impact ionization of the residual gas, which creates a source of secondary particles inside the beam pipe. For negative ion beams, the effect of the beam electric field is to ex...

Beam self-excited rf cavity driver for a deflector or focusing system

International Nuclear Information System (INIS)

Wadlinger, E.A.

1996-01-01

A bunched beam from and accelerator can excite and power an rf cavity which then drives either a deflecting or focusing (including nonlinear focusing) rf cavity with and amplitude related to beam current. Rf power, generated when a bunched beam loses energy to an rf field when traversing an electric field that opposes the particle's motion, is used to drive a separate (or the same) cavity to either focus or deflect the beam. The deflected beam can be stopped by an apertures or directed to a different area of a target depending on beam current. The beam-generated rf power can drive a radio-frequency quadrupole (RFQ) that can change the focusing properties of a beam channel as a function of beam current (space- charge force compensation or modifying the beam distribution on a target). An rf deflector can offset a beam to a downstream sextupole, effectively producing a position-dependent quadrupole field. The combination of rf deflector plus sextupole will produce a beam current dependent quadropole-focusing force. A static quadrupole magnet plus another rf deflector can place the beam back on the optic axis. This paper describes the concept, derives the appropriate equations for system analysis, and fives examples. A variation on this theme is to use the wake field generated in an rf cavity to cause growth in the beam emittance. The beam current would then be apertured by emittance defining slits

Beam self-excited rf cavity driver for a deflector or focusing system

International Nuclear Information System (INIS)

Wadlinger, E.A.

1996-01-01

A bunched beam from an accelerator can excite and power an rf cavity which then drives either a deflecting or focusing (including nonlinear focusing) rf cavity with an amplitude related to beam current. Rf power, generated when a bunched beam loses energy to an rf field when traversing an electric field that opposes the particle's motion, is used to drive a separate (or the same) cavity to either focus or deflect the beam. The deflected beam can be stopped by an aperture or directed to a different area of a target depending on beam current. The beam-generated rf power can drive a radiofrequency quadrupole that can change the focusing properties of a beam channel as a function of beam current (space-charge-force compensation or modifying the beam distribution on a target). An rf deflector can offset a beam to a downstream sextupole, effectively producing a position-dependent quadrupole field. The combination of rf deflector plus sextupole will produce a beam current dependent quadrupole-focusing force. A static quadrupole magnet plus another rf deflector can place the beam back on the optic axis. This paper describes the concept, derives the appropriate equations for system analysis, and gives examples. A variation on this theme is to use the wake field generated in an rf cavity to cause growth in the beam emittance. The beam current would then be apertured by emittance defining slits. (author)

Reduction of space charge breakdown in e-beam irradiated nano/polymethyl methacrylate composites

International Nuclear Information System (INIS)

Zheng Feihu; Zhang Yewen; An Zhenlian; Dong Jianxing; Lei Qingquan

2013-01-01

Fast discharge of numerous space charges in dielectric materials can cause space charge breakdown. This letter reports the role of nanoparticles in affecting space charge breakdown of nano/polymethyl methacrylate composites. Space charge distributions in the composites, implanted by electron beam irradiation, were measured by pressure wave propagation method. The results show that the nanoparticles have significant effects on the isothermal charge decay and space charge breakdown in the nanocomposites. The resistance to space charge breakdown in the nanocomposites is attributed to the combined action of the introduction of deep trapping states and the scattering effect by the added nanoparticles.

Studies on space charge neutralization and emittance measurement of beam from microwave ion source

Energy Technology Data Exchange (ETDEWEB)

Misra, Anuraag; Goswami, A.; Sing Babu, P.; Srivastava, S.; Pandit, V. S., E-mail: pandit@vecc.gov.in, E-mail: vspandit12@gmail.com [Variable Energy Cyclotron Centre, 1-AF, Bidhannagar, Kolkata 700 064 (India)

2015-11-15

A 2.45 GHz microwave ion source together with a beam transport system has been developed at VECC to study the problems related with the injection of high current beam into a compact cyclotron. This paper presents the results of beam profile measurement of high current proton beam at different degrees of space charge neutralisation with the introduction of neon gas in the beam line using a fine leak valve. The beam profiles have been measured at different pressures in the beam line by capturing the residual gas fluorescence using a CCD camera. It has been found that with space charge compensation at the present current level (∼5 mA at 75 keV), it is possible to reduce the beam spot size by ∼34%. We have measured the variation of beam profile as a function of the current in the solenoid magnet under the neutralised condition and used these data to estimate the rms emittance of the beam. Simulations performed using equivalent Kapchinsky-Vladimirsky beam envelope equations with space charge neutralization factor are also presented to interpret the experimental results.

Space Charge Compensation in the Linac4 Low Energy Beam Transport Line with Negative Hydrogen Ions

CERN Document Server

Valerio-Lizarraga, C; Leon-Monzon, I; Lettry, J; Midttun, O; Scrivens, R

2014-01-01

The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Tranport (LEBT) using the package IBSimu1, which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H- beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

Sheet beam model for intense space charge: Application to Debye screening and the distribution of particle oscillation frequencies in a thermal equilibrium beam

Directory of Open Access Journals (Sweden)

Steven M. Lund

2011-05-01

Full Text Available A one-dimensional Vlasov-Poisson model for sheet beams is reviewed and extended to provide a simple framework for analysis of space-charge effects. Centroid and rms envelope equations including image-charge effects are derived and reasonable parameter equivalences with commonly employed 2D transverse models of unbunched beams are established. This sheet-beam model is then applied to analyze several problems of fundamental interest. A sheet-beam thermal equilibrium distribution in a continuous focusing channel is constructed and shown to have analogous properties to two- and three-dimensional thermal equilibrium models in terms of the equilibrium structure and Debye screening properties. The simpler formulation for sheet beams is exploited to explicitly calculate the distribution of particle oscillation frequencies within a thermal equilibrium beam. It is shown that as space-charge intensity increases, the frequency distribution becomes broad, suggesting that beams with strong space-charge can have improved stability relative to beams with weak space-charge.

Space Charge Effects

CERN Document Server

Ferrario, M.; Palumbo, L.

2014-12-19

The space charge forces are those generated directly by the charge distribution, with the inclusion of the image charges and currents due to the interaction of the beam with a perfectly conducting smooth pipe. Space charge forces are responsible for several unwanted phenomena related to beam dynamics, such as energy loss, shift of the synchronous phase and frequency , shift of the betatron frequencies, and instabilities. We will discuss in this lecture the main feature of space charge effects in high-energy storage rings as well as in low-energy linacs and transport lines.

Space-Charge Effect

International Nuclear Information System (INIS)

Chauvin, N

2013-01-01

First, this chapter introduces the expressions for the electric and magnetic space-charge internal fields and forces induced by high-intensity beams. Then, the root-mean-square equation with space charge is derived and discussed. In the third section, the one-dimensional Child-Langmuir law, which gives the maximum current density that can be extracted from an ion source, is exposed. Space-charge compensation can occur in the low-energy beam transport lines (located after the ion source). This phenomenon, which counteracts the spacecharge defocusing effect, is explained and its main parameters are presented. The fifth section presents an overview of the principal methods to perform beam dynamics numerical simulations. An example of a particles-in-cells code, SolMaxP, which takes into account space-charge compensation, is given. Finally, beam dynamics simulation results obtained with this code in the case of the IFMIF injector are presented. (author)

Space-Charge Effect

CERN Document Server

Chauvin, N.

2013-12-16

First, this chapter introduces the expressions for the electric and magnetic space-charge internal fields and forces induced by high-intensity beams. Then, the root-mean-square equation with space charge is derived and discussed. In the third section, the one-dimensional Child-Langmuir law, which gives the maximum current density that can be extracted from an ion source, is exposed. Space-charge compensation can occur in the low-energy beam transport lines (located after the ion source). This phenomenon, which counteracts the spacecharge defocusing effect, is explained and its main parameters are presented. The fifth section presents an overview of the principal methods to perform beam dynamics numerical simulations. An example of a particles-in-cells code, SolMaxP, which takes into account space-charge compensation, is given. Finally, beam dynamics simulation results obtained with this code in the case of the IFMIF injector are presented.

Longitudinal and transverse space charge limitations on transport of maximum power beams

International Nuclear Information System (INIS)

Khoe, T.K.; Martin, R.L.

1977-01-01

The maximum transportable beam power is a critical issue in selecting the most favorable approach to generating ignition pulses for inertial fusion with high energy accelerators. Maschke and Courant have put forward expressions for the limits on transport power for quadrupole and solenoidal channels. Included in a more general way is the self consistent effect of space charge defocusing on the power limit. The results show that no limits on transmitted power exist in principal. In general, quadrupole transport magnets appear superior to solenoids except for transport of very low energy and highly charged particles. Longitudinal space charge effects are very significant for transport of intense beams

Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions

Energy Technology Data Exchange (ETDEWEB)

Valerio-Lizarraga, Cristhian A., E-mail: cristhian.alfonso.valerio.lizarraga@cern.ch [CERN, Geneva (Switzerland); Departamento de Investigación en Física, Universidad de Sonora, Hermosillo (Mexico); Lallement, Jean-Baptiste; Lettry, Jacques; Scrivens, Richard [CERN, Geneva (Switzerland); Leon-Monzon, Ildefonso [Facultad de Ciencias Fisico-Matematicas, Universidad Autónoma de Sinaloa, Culiacan (Mexico); Midttun, Øystein [CERN, Geneva (Switzerland); University of Oslo, Oslo (Norway)

2014-02-15

The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H{sup −} beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

Aberration of a negative ion beam caused by space charge effect

International Nuclear Information System (INIS)

Miyamoto, K.; Wada, S.; Hatayama, A.

2010-01-01

Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.

Aberration of a negative ion beam caused by space charge effect

Energy Technology Data Exchange (ETDEWEB)

Miyamoto, K. [Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502 (Japan); Wada, S.; Hatayama, A. [Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

2010-02-15

Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.

Aberration of a negative ion beam caused by space charge effect.

Science.gov (United States)

Miyamoto, K; Wada, S; Hatayama, A

2010-02-01

Aberrations are inevitable when the charged particle beams are extracted, accelerated, transmitted, and focused with electrostatic and magnetic fields. In this study, we investigate the aberration of a negative ion accelerator for a neutral beam injector theoretically, especially the spherical aberration caused by the negative ion beam expansion due to the space charge effect. The negative ion current density profiles with the spherical aberration are compared with those without the spherical aberration. It is found that the negative ion current density profiles in a log scale are tailed due to the spherical aberration.

Space charge effects: tune shifts and resonances

International Nuclear Information System (INIS)

Weng, W.T.

1986-08-01

The effects of space charge and beam-beam interactions on single particle motion in the transverse degree of freedom are considered. The space charge force and the resulting incoherent tune shift are described, and examples are given from the AGS and CERN's PSB. Equations of motion are given for resonances in the presence of the space charge force, and particle behavior is examined under resonance and space charge conditions. Resonance phase space structure is described with and without space charge. Uniform and bunched beams are compared. Beam-beam forces and resonances and beam-beam detuning are described. 18 refs., 15 figs

EXPLORING TRANSVERSE BEAM STABILITY IN THE SNS IN THE PRESENCE OF SPACE CHARGE.

Energy Technology Data Exchange (ETDEWEB)

FEDOTOV,A.V.; BLASKIEWICZ,M.; WEI,J.; DANILOV,V.; HOLMES,J.; SHISHLO,A.

2002-06-03

The highest possible intensity in the machine is typically determined by the onset of coherent beam instabilities. Understanding the contribution of various effects to the damping and growth of such instabilities in the regime of strong space charge is thus of crucial importance. In this paper we explore transverse beam stability by numerical simulations using recently implemented models of transverse impedance and three-dimensional space charge. Results are discussed with application to the SNS accumulators.

Benchmarking of 3D space charge codes using direct phase space measurements from photoemission high voltage dc gun

Directory of Open Access Journals (Sweden)

Ivan V. Bazarov

2008-10-01

Full Text Available We present a comparison between space charge calculations and direct measurements of the transverse phase space of space charge dominated electron bunches from a high voltage dc photoemission gun followed by an emittance compensation solenoid magnet. The measurements were performed using a double-slit emittance measurement system over a range of bunch charge and solenoid current values. The data are compared with detailed simulations using the 3D space charge codes GPT and Parmela3D. The initial particle distributions were generated from measured transverse and temporal laser beam profiles at the photocathode. The beam brightness as a function of beam fraction is calculated for the measured phase space maps and found to approach within a factor of 2 the theoretical maximum set by the thermal energy and the accelerating field at the photocathode.

Chaotic behaviour induced by space charge

International Nuclear Information System (INIS)

Lagniel, J.M.

1994-01-01

In numerous non-linear dynamical systems studied in various disciplines (fluid dynamics, celestial mechanisms, chemistry, biology, economy, ecology...), chaotic motions are generated by the dynamics itself whereas no random force is present. This phenomenon, already studied in the particle accelerator field to understand the beam-beam effect, is also observed in numerical experiments on space-charge dominated beams. Stochasticity threshold and halo formation are discussed for a continuous focusing channel (1D beam) and for a FODO channel (2D beam) with the possibility to take into account the defocusing effects of RF gaps localized between the quadrupoles. (authors). 7 refs., 4 figs

Space-charge effects on the propagation of hollow electron beams

International Nuclear Information System (INIS)

Barroso, J.J.; Stellati, C.

1994-01-01

The dynamics of hollow electron beams with gyro motion propagating down a cylindrical drift tube is analysed on the basis of a non-adiabatic-gun-generated laminar beam. Due to the action of beam's self-space charge field, the transverse velocity spread has an oscillatory behavior along the drift tube wherein the spatial auto modulation period shortens with increasing current. Numerical simulation results indicate that even at a 10 A beam current, the resulting transverse velocity spread is still less than the spread for a zero beam current. (author). 5 refs, 3 figs

Beam transfer between the coupled cavity linac and the low energy booster synchrotron for the SSC [Superconducting Super Collider

International Nuclear Information System (INIS)

Bhandari, R.K.; Penner, S.

1990-09-01

Ion optical design of the transfer line, which will be used to inject H - beam at 600 MeV from the Coupled Cavity Linac (CCL) into the Low Energy Booster (LEB) synchrotron, is described. Space charge effects of up to 50 mA average beam current have been taken into account

Chaos in Time-Dependent Space-Charge Potentials

CERN Document Server

Betzel, Gregory T; Sideris, Ioannis V

2005-01-01

We consider a spherically symmetric, homologously breathing, space-charge-dominated beam bunch in the spirit of the particle-core model. The question we ask is: How does the time dependence influence the population of chaotic orbits? The static beam has zero chaotic orbits; the equation of particle motion is integrable up to quadrature. This is generally not true once the bunch is set into oscillation. We quantify the population of chaotic orbits as a function of space charge and oscillation amplitude (mismatch). We also apply a newly developed measure of chaos, one that distinguishes between regular, sticky, and wildly chaotic orbits, to characterize the phase space in detail. We then introduce colored noise into the system and show how its presence modifies the dynamics. One finding is that, despite the presence of a sizeable population of chaotic orbits, halo formation in the homologously breathing beam is much less prevalent than in an envelope-matched counterpart wherein an internal collective mode is ex...

On Beam Matching and the Space-Charge Effect in protoDUNE-SP

CERN Document Server

Mandalia, Jesal Paresh

2017-01-01

In this project simulations using LArSoft have been analysed in particular looking at how the space-charge effect will affect the matching of particle tracks from the beam line monitor to the TPC and the TPC's performance measuring $\\frac{dE}{dx}$ in protoDUNE-SP. The analysis here provides some preliminary calibrations for protoDUNE-SP to account for the impact the space charge effect will have. Many areas of pion cross section analysis will be affected by the space charge effect so it is vital for a calibration to be developed.

Study on discrete space charge effects in electron beams and guns

International Nuclear Information System (INIS)

Tang Tiantong

1990-01-01

The discrete space charge effects in electron beams are studied and a statistical dynamics equation of the ensemble of beam electrons is derived. An approximated analytical solution of this equation is given. This equation has been applied to beam crossover and field-emission and thermal-emission gun problems. The computer calculation results agree on the whole with those of Monte Carlo simulation and experimental data. (orig.)

Final Report for 'Design calculations for high-space-charge beam-to-RF conversion'

International Nuclear Information System (INIS)

Smithe, David N.

2008-01-01

Accelerator facility upgrades, new accelerator applications, and future design efforts are leading to novel klystron and IOT device concepts, including multiple beam, high-order mode operation, and new geometry configurations of old concepts. At the same time, a new simulation capability, based upon finite-difference 'cut-cell' boundaries, has emerged and is transforming the existing modeling and design capability with unparalleled realism, greater flexibility, and improved accuracy. This same new technology can also be brought to bear on a difficult-to-study aspect of the energy recovery linac (ERL), namely the accurate modeling of the exit beam, and design of the beam dump for optimum energy efficiency. We have developed new capability for design calculations and modeling of a broad class of devices which convert bunched beam kinetic energy to RF energy, including RF sources, as for example, klystrons, gyro-klystrons, IOT's, TWT's, and other devices in which space-charge effects are important. Recent advances in geometry representation now permits very accurate representation of the curved metallic surfaces common to RF sources, resulting in unprecedented simulation accuracy. In the Phase I work, we evaluated and demonstrated the capabilities of the new geometry representation technology as applied to modeling and design of output cavity components of klystron, IOT's, and energy recovery srf cavities. We identified and prioritized which aspects of the design study process to pursue and improve in Phase II. The development and use of the new accurate geometry modeling technology on RF sources for DOE accelerators will help spark a new generational modeling and design capability, free from many of the constraints and inaccuracy associated with the previous generation of 'stair-step' geometry modeling tools. This new capability is ultimately expected to impact all fields with high power RF sources, including DOE fusion research, communications, radar and other

Generation of initial kinetic distributions for simulation of long-pulse charged particle beams with high space-charge intensity

Directory of Open Access Journals (Sweden)

Steven M. Lund

2009-11-01

Full Text Available Self-consistent Vlasov-Poisson simulations of beams with high space-charge intensity often require specification of initial phase-space distributions that reflect properties of a beam that is well adapted to the transport channel—both in terms of low-order rms (envelope properties as well as the higher-order phase-space structure. Here, we first review broad classes of kinetic distributions commonly in use as initial Vlasov distributions in simulations of unbunched or weakly bunched beams with intense space-charge fields including the following: the Kapchinskij-Vladimirskij (KV equilibrium, continuous-focusing equilibria with specific detailed examples, and various nonequilibrium distributions, such as the semi-Gaussian distribution and distributions formed from specified functions of linear-field Courant-Snyder invariants. Important practical details necessary to specify these distributions in terms of standard accelerator inputs are presented in a unified format. Building on this presentation, a new class of approximate initial kinetic distributions are constructed using transformations that preserve linear focusing, single-particle Courant-Snyder invariants to map initial continuous-focusing equilibrium distributions to a form more appropriate for noncontinuous focusing channels. Self-consistent particle-in-cell simulations are employed to show that the approximate initial distributions generated in this manner are better adapted to the focusing channels for beams with high space-charge intensity. This improved capability enables simulations that more precisely probe intrinsic stability properties and machine performance.

Rf and space-charge induced emittances in laser-driven rf guns

International Nuclear Information System (INIS)

Kim, Kwang-Je; Chen, Yu-Jiuan.

1988-10-01

Laser-driven rf electron guns are potential sources of high-current, low-emittance, short bunch-length electron beams, which are required for many advanced accelerator applications, such as free-electron lasers and injectors for high-energy machines. In such guns the design of which was pioneered at Los Alamos National Laboratory and which is currently being developed at several other laboratories, a high-power laser beam illuminates a photo-cathode surface placed on an end wall of an rf cavity. The main advantages of this type of gun are that the time structure of the electron beam is controlled by the laser, eliminating the need for bunchers, and that the electric field in rf cavities can be made very strong, so that the effects due to space-charge repulsion can be minimized. In this paper, we present an approximate but simple analysis for the transverse and longitudinal emittances in rf guns that takes into account both the time variation of the rf field and the space-charge effect. The results are compared and found to agree well with those from simulation. 7 refs., 6 figs

PATH: a lumped-element beam-transport simulation program with space charge

International Nuclear Information System (INIS)

Farrell, J.A.

1983-01-01

PATH is a group of computer programs for simulating charged-particle beam-transport systems. It was developed for evaluating the effects of some aberrations without a time-consuming integration of trajectories through the system. The beam-transport portion of PATH is derived from the well-known program, DECAY TURTLE. PATH contains all features available in DECAY TURTLE (including the input format) plus additional features such as a more flexible random-ray generator, longitudinal phase space, some additional beamline elements, and space-charge routines. One of the programs also provides a simulation of an Alvarez linear accelerator. The programs, originally written for a CDC 7600 computer system, also are available on a VAX-VMS system. All of the programs are interactive with input prompting for ease of use

Recent status of FCI: PIC simulation of coupled-cavity structure

International Nuclear Information System (INIS)

Shintake, Tsumoru

1996-01-01

New version of FCI (Field Charge Interaction)-code simulates beam dynamics of an electron beam running in a coupled-cavity structure, such as a multi-cell output structure in a klystron amplifier, a coupled cavity TWT amplifier, a bunching structure in an electron injector and also an rf-gun with multi-cell accelerating cavity. The particle-in-cell simulation takes into account the space charge field, the beam loading effect and energy exchange with an external circuit in a self-consistent manner. (author)

Analytical treatment of the nonlinear electron cloud effect and the combined effects with beam-beam and space charge nonlinear forces in storage rings

International Nuclear Information System (INIS)

Gao Jie

2009-01-01

In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonlinear electron cloud effect combined with beam-beam and space charge effects, analytically. This analytical treatment is applied to BEPC II. The corresponding analytical expressions developed in this paper are useful both in understanding the physics behind these problems and also in making practical quick hand estimations. (author)

Long bunch trains measured using a prototype cavity beam position monitor for the Compact Linear Collider

Directory of Open Access Journals (Sweden)

F. J. Cullinan

2015-11-01

Full Text Available The Compact Linear Collider (CLIC requires beam position monitors (BPMs with 50 nm spatial resolution for alignment of the beam line elements in the main linac and beam delivery system. Furthermore, the BPMs must be able to make multiple independent measurements within a single 156 ns long bunch train. A prototype cavity BPM for CLIC has been manufactured and tested on the probe beam line at the 3rd CLIC Test Facility (CTF3 at CERN. The transverse beam position is determined from the electromagnetic resonant modes excited by the beam in the two cavities of the pickup, the position cavity and the reference cavity. The mode that is measured in each cavity resonates at 15 GHz and has a loaded quality factor that is below 200. Analytical expressions for the amplitude, phase and total energy of signals from long trains of bunches have been derived and the main conclusions are discussed. The results of the beam tests are presented. The variable gain of the receiver electronics has been characterized using beam excited signals and the form of the signals for different beam pulse lengths with the 2/3  ns bunch spacing has been observed. The sensitivity of the reference cavity signal to charge and the horizontal position signal to beam offset have been measured and are compared with theoretical predictions based on laboratory measurements of the BPM pickup and the form of the resonant cavity modes as determined by numerical simulation. Finally, the BPM was calibrated so that the beam position jitter at the BPM location could be measured. It is expected that the beam jitter scales linearly with the beam size and so the results are compared to predicted values for the latter.

Long bunch trains measured using a prototype cavity beam position monitor for the Compact Linear Collider

Science.gov (United States)

Cullinan, F. J.; Boogert, S. T.; Farabolini, W.; Lefevre, T.; Lunin, A.; Lyapin, A.; Søby, L.; Towler, J.; Wendt, M.

2015-11-01

The Compact Linear Collider (CLIC) requires beam position monitors (BPMs) with 50 nm spatial resolution for alignment of the beam line elements in the main linac and beam delivery system. Furthermore, the BPMs must be able to make multiple independent measurements within a single 156 ns long bunch train. A prototype cavity BPM for CLIC has been manufactured and tested on the probe beam line at the 3rd CLIC Test Facility (CTF3) at CERN. The transverse beam position is determined from the electromagnetic resonant modes excited by the beam in the two cavities of the pickup, the position cavity and the reference cavity. The mode that is measured in each cavity resonates at 15 GHz and has a loaded quality factor that is below 200. Analytical expressions for the amplitude, phase and total energy of signals from long trains of bunches have been derived and the main conclusions are discussed. The results of the beam tests are presented. The variable gain of the receiver electronics has been characterized using beam excited signals and the form of the signals for different beam pulse lengths with the 2 /3 ns bunch spacing has been observed. The sensitivity of the reference cavity signal to charge and the horizontal position signal to beam offset have been measured and are compared with theoretical predictions based on laboratory measurements of the BPM pickup and the form of the resonant cavity modes as determined by numerical simulation. Finally, the BPM was calibrated so that the beam position jitter at the BPM location could be measured. It is expected that the beam jitter scales linearly with the beam size and so the results are compared to predicted values for the latter.

Measurements of stability limits for a space-charge-dominated ion beam in a long A.G. transport channel

International Nuclear Information System (INIS)

Tiefenback, M.G.; Keefe, D.

1985-05-01

The Single Beam Transport Experiment at LBL consists of 82 electrostatic quadrupole lenses arranged in a FODO lattice. Five further lenses provide a matched beam from a high-current high-brightness cesium source for injection into the FODO channel. We call the transport conditions stable if both the emittance and current remain unchanged between the beginning and end of the channel, and unstable if either the emittance grows or the current decreases because of collective effects. We have explored the range of single-particle betatron phase advance per period from sigma 0 = 45 0 to 150 0 to determine the stability limits for the space-charge depressed phase advance, sigma. No lower limit for sigma (down to 7 0 ) has been found at sigma 0 = 60 0 , whereas limits have clearly been identified and mapped in the region of sigma 0 above 90 0

Aspects of space charge theory applied to dielectric under electron beam irradiation

International Nuclear Information System (INIS)

Oliveira, L.N. de.

1975-01-01

Irradiation of solid dielectric with electron beams has been used as a power full tool in investigations of charge storage and transport in such materials. Some of the results that have been obtained in this area are reviewed and the formulation of a transport equation for excess charge in irradiated insulators is dicussed. This equation is subsequently applied to various experimental set-ups. It is found that space charge effects play an essential role in the establishment of stationary currents in samples subject to quasi-penetrating electron beams. Such effects may, however, be neglected for low electron ranges. Theoretical results are in good agreement with experimental findings by Spear (1955)

Nanometer emittance ultralow charge beams from rf photoinjectors

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R. K. Li

2012-09-01

Full Text Available In this paper we discuss the generation of a new class of high brightness relativistic electron beams, characterized by ultralow charge (0.1–1 pC and ultralow normalized emittance (<50  nm. These beams are created in rf photoinjectors when the laser is focused on the cathode to very small transverse sizes (<30  μm rms. In this regime, the charge density at the cathode approaches the limit set by the extraction electric field. By shaping the laser pulse to have a cigarlike aspect ratio (the longitudinal dimension much larger than the transverse dimension and a parabolic temporal profile, the resulting space charge dominated dynamics creates a uniformly filled ellipsoidal distribution and the emittance can be nearly preserved to its thermal value. We also present a new method, based on a variation of the pepper-pot technique, for single shot measurements of the ultralow emittances for this new class of beams.

Intrinsic space charge resonances and the space charge limit

International Nuclear Information System (INIS)

Parzen, G.

1990-01-01

A study has been done of the dependence of the space charge limit on the choice of ν-values using a simulation program. This study finds a strong dependence of the space charge limit on the location of the ν-values relative to the intrinsic space charge resonances, which are driven by the space charge forces due to the beam itself. Four accelerators were studied. For some of these accelerators the study suggest that the space charge limit can be increased by about a factor of 2 proper choice of the ν-values. The lower order 1/2 and 1/4 intrinsic resonances appear to be the important resonances. There is some evidence for effects due to the 1/6 and 1/8 intrinsic resonances, particularly for larger synchrotrons. 5 figs

Improving the beam quality of rf guns by correction of rf and space-charge effects

International Nuclear Information System (INIS)

Serafini, L.

1992-01-01

In this paper we describe two possible strategies to attain ultra-low emittance electron beam generation by laser-driven RF guns. The first one is based on the exploitation of multi-mode resonant cavities to neutralize the emittance degradation induced by RF effects. Accelerating cigar-like (long and thin) electron bunches in multi-mode operated RF guns the space charge induced emittance is strongly decreased at the same time: high charged bunches, as typically requested by future TeV e - e + colliders, can be delivered by the gun at a quite low transverse emittance and good behaviour in the longitudinal phase space, so that they can be magnetically compressed to reach higher peak currents. The second strategy consists in using disk-like electron bunches, produced by very short laser pulses illuminating the photocathode. By means of an analytical study a new regime has been found, where the normalized transverse emittance scales like the inverse of the peak current, provided that the laser pulse intensity distribution is properly shaped in the transverse direction. Preliminary numerical simulations confirm the analytical predictions and show that the minimum emittance achievable is set up, in this new regime, by the wake-field interaction between the bunch and the cathode metallic wall

Study of the beam-cavity interaction in the CERN PS 10 MHz cavities and investigation of hardware solutions to reduce beam loading

CERN Document Server

AUTHOR|(CDS)2086984; Palumbo, Luigi

In the Proton Synchrotron (PS), where the LHC protons longitudinal structure (bunch spacing) is determined as the result of a sophisticated series of Radio Frequency (RF) gymnastics, collective effects were identified as a major limitation to the achievable beam current delivered to the LHC. Dedicated machine development studies pointed out the RF cavities to be one of the major source of instability in the PS. In particular, the 10 MHz RF system, responsible for beam acceleration, was identified as the most probable impedance source in the machine. The cavity impedance limits the circulating intensity in the accelerator since the beam-induced voltage could trigger longitudinal instabilities causing beam losses. For this reason the cavity impedance seen by the beam must be kept as low as possible. In the framework of the LHC Injector Upgrade (LIU) project, the present PS 10 MHz RF system requires an upgrade, in order to reach higher beam intensities and to reduce beam loading. This thesis focuses on the impro...

Optical method for mapping the transverse phase space of a charged particle beam

International Nuclear Information System (INIS)

Fiorito, R.B.; Shkvarunets, A.G.; O'Shea, P.G.

2002-01-01

We are developing an all optical method to map the transverse phase space map of a charged particle beam. Our technique employs OTR interferometry (OTRI) in combination with a scanning pinhole to make local orthogonal (x,y) divergence and trajectory angle measurements as function of position within the transverse profile of the beam. The localized data allows a reconstruction of the horizontal and vertical phase spaces of the beam. We have also demonstrated how single and multiple pinholes can in principle be used to make such measurements simultaneously

Studies of HOMs in chains of SRF cavities using state-space concatenation scheme

Energy Technology Data Exchange (ETDEWEB)

Galek, Tomasz; Heller, Johann; Flisgen, Thomas; Brackebusch, Korinna; Rienen, Ursula van [Institut fuer Allgemeine Elektrotechnik, Universitaet Rostock (Germany)

2016-07-01

The design of modern superconducting radio frequency cavities for acceleration of charged particle bunches requires intensive numerical simulations, as they typically arise as modules of several multi-cell cavities. A wide variety of parameters vital to the proper operation of accelerating cavities must be optimized and studied. One of the most important issues concerning the SRF cavities is the influence of the higher order modes on the beam quality, in this contribution. For TESLA-like structures with 1.3 GHz accelerating mode, higher order modes are calculated up to 4 GHz, the external quality factor and the shunt/geometrical impedance spectra are analyzed. To compute properties of complete RF modules the state-space concatenation scheme is used. The aspects of the concatenation scheme and its application to the bERLinPro's chain of cavities is discussed.

Phase space imaging of a beam of charged particles by frictional forces

International Nuclear Information System (INIS)

Daniel, H.

1977-01-01

In the case of frictional forces, defined by always acting opposite to the particle motion, Liouville's theorem does not apply. The effect of such forces on a beam of charged particles is calculated in closed form. Emphasis is given to the phase space imaging by a moderator. Conditions for an increase in phase space density are discussed. (Auth.)

PSR experience with beam losses, instabilities and space charge effects

International Nuclear Information System (INIS)

Macek, Robert J.

1998-01-01

Average current from the PSR has been limited to ∼70 μA at 20 Hz by beam losses of 0.4 to 0.5 μA which arise from two principal causes, production of H 0 excited states and stored-beam scattering in the stripper foil. To reduce beam losses, an upgrade from the two-step H 0 injection to direct H - injection is underway and will be completed in 1998. Peak intensity from the PSR is limited by a strong instability that available evidence indicates is the two-stream e-p instability. New evidence for the e-p hypothesis is presented. At operating intensities, the incoherent space charge tune shift depresses both horizontal and vertical tunes past the integer without additional beam loss although some intensity-dependent emittance growth is observed

A modified space charge routine for high intensity bunched beams

International Nuclear Information System (INIS)

Lapostolle, P.; Garnett, R.W.; Wangler, T.P.

1996-01-01

In 1991 a space charge calculation for bunched beam with a three-dimensional ellipsoid was proposed, replacing the usual SCHEFF routines. It removes the cylindrical symmetry required in SCHEFF and avoids the point to point interaction computation, whose number of simulation points is limited. This routine has now been improved with the introduction of two or three ellipsoids giving a good representation of the complex non-symmetrical form of the bunch (unlike the 3-d ellipsoidal assumption). The ellipsoidal density distributions are computed with a new method, avoiding the difficulty encountered near the centre (the axis in 2-d problems) by the previous method. It also provides a check of the ellipsoidal symmetry for each part of the distribution. Finally, the Fourier analysis reported in 1991 has been replaced by a very convenient Hermite expansion, which gives a simple but accurate representation of practical distributions. Comparisons with other space charge routines have been made, particularly with the ones applying other techniques such as SCHEFF. Introduced in the versatile beam dynamics code DYNAC, it should provide a good tool for the study of the various parameters responsible for the halo formation in high intensity linacs. (orig.)

Quadrupole beam-transport experiment for heavy ions under extreme space charge conditions

International Nuclear Information System (INIS)

Chupp, W.; Faltens, A.; Hartwig, E.C.

1983-03-01

A Cs ion-beam-transport experiment is in progress to study beam behavior under extreme space-charge conditions. A five-lens section matches the beam into a periodic electrostatic quadrupole FODO channel and its behavior is found to agree with predictions. With the available parameters (less than or equal to 200 keV, less than or equal to 20 mA, πepsilon/sub n/ greater than or equal to 10 - 7 π rad-m, up to 41 periods) the transverse (betatron) occillation frequency (nu) can be depressed down to one-tenth of its zero current value (nu/sub 0/), where nu/sup 2/ = nu/sub 0//sup 2/ -#betta#/sub p/ 2 /2, and #betta#/sub p/ is the beam plasma frequency. The current can be controlled by adjustment of the gun and the emittance can be controlled independently by means of a set of charged grids

Space-charge calculation for bunched beams with 3-D ellipsoidal symmetry

International Nuclear Information System (INIS)

Garnett, R.W.; Wangler, T.P.

1991-01-01

A method for calculating 3-D space-charge forces has been developed that is suitable for bunched beams of either ions or relativistic electrons. The method is based on the analytic relations between charge-density and electric fields for a distribution with 3-D ellipsoidal symmetry in real space. At each step we use a Fourier-series representation for the smooth particle-density function obtained from the distribution of the macroparticles being tracked through the elements of the system. The resulting smooth electric fields reduce the problem of noise from artificial collisions, associated with small numbers of interacting macroparticles. Example calculations will be shown for comparison with other methods. 4 refs., 2 figs., 1 tab

PSR experience with beam losses, instabilities and space charge effects

International Nuclear Information System (INIS)

Macek, R.J.

1998-01-01

Average current from the PSR has been limited to ∼70 μA at 20 Hz by beam losses of 0.4 to 0.5 μA which arise from two principal causes, production of H 0 excited states and stored-beam scattering in the stripper foil. To reduce beam losses, an upgrade from the two-step H 0 injection to direct H - injection is underway and will be completed in 1998. Peak intensity from the PSR is limited by a strong instability that available evidence indicates is the two-stream e-p instability. New evidence for the e-p hypothesis is presented. At operating intensities, the incoherent space charge tune shift depresses both horizontal and vertical tunes past the integer without additional beam loss although some intensity-dependent emittance growth is observed. copyright 1998 American Institute of Physics

Simulations and experiments of intense ion beam compression in space and time

International Nuclear Information System (INIS)

Yu, S.S.; Seidl, P.A.; Roy, P.K.; Lidia, S.M.; Coleman, J.E.; Kaganovich, I.D.; Gilson, E.P.; Welch, Dale Robert; Sefkow, Adam B.; Davidson, R.C.

2008-01-01

The Heavy Ion Fusion Science Virtual National Laboratory has achieved 60-fold longitudinal pulse compression of ion beams on the Neutralized Drift Compression Experiment (NDCX) (P. K. Roy et al., Phys. Rev. Lett. 95, 234801 (2005)). To focus a space-charge-dominated charge bunch to sufficiently high intensities for ion-beam-heated warm dense matter and inertial fusion energy studies, simultaneous transverse and longitudinal compression to a coincident focal plane is required. Optimizing the compression under the appropriate constraints can deliver higher intensity per unit length of accelerator to the target, thereby facilitating the creation of more compact and cost-effective ion beam drivers. The experiments utilized a drift region filled with high-density plasma in order to neutralize the space charge and current of an ∼300 keV K + beam and have separately achieved transverse and longitudinal focusing to a radius Z 2 MeV) ion beam user-facility for warm dense matter and inertial fusion energy-relevant target physics experiments.

Beam position diagnostics with higher order modes in third harmonic superconducting accelerating cavities

CERN Document Server

Zhang, P; Baboi, Nicoleta

2012-01-01

Higher order modes (HOM) are electromagnetic resonant fields. They can be excited by an electron beam entering an accelerating cavity, and constitute a component of the wakefield. This wakefield has the potential to dilute the beam quality and, in the worst case, result in a beam-break-up instability. It is therefore important to ensure that these fields are well suppressed by extracting energy through special couplers. In addition, the effect of the transverse wakefield can be reduced by aligning the beam on the cavity axis. This is due to their strength depending on the transverse offset of the excitation beam. For suitably small offsets the dominant components of the transverse wakefield are dipole modes, with a linear dependence on the transverse offset of the excitation bunch. This fact enables the transverse beam position inside the cavity to be determined by measuring the dipole modes extracted from the couplers, similar to a cavity beam position monitor (BPM), but requires no additional vacuum instrum...

Ion trajectories calculation in a three dimensional beam subjected to a space charge

International Nuclear Information System (INIS)

Tauth, T.

1978-04-01

Physical and geometrical conditions allowing a first approximation of necessary sizes to numerical integration of the ions movement equations subjected to electrical and magnetic crossed fields and space charge action are investigated here. To take into consideration the effect of the last one, two artifices are put forward: replacing charged particles by equivalent particles in calculating the coulomb force, electrical field calculation produced in different points situated on the beam envelope by the uniform charges distribution [fr

Space charge effects of CSR

International Nuclear Information System (INIS)

Liu Yong; Xia Jiawen; Xu Xiangyang; Lu Xiaowen; Wu Junli

2000-01-01

Cooler Storage Ring (CSR), and upgrading program planned at the Heavy Ion Research Facility in Lanzhou (HIRFL), will supply beams with higher quality and intensity. Space charge effects should be considered due to this magnitude of intensity in CSR. The concept and some phenomena of space charge effects are discussed. Space charge intensity limit and space charge tune shift of normal CSR operation are given. It is of significance for the construction and operation of the future facility

Cold-fluid theory of equilibrium and stability of a high-intensity periodically twisted ellipse-shaped charged-particle beam

Directory of Open Access Journals (Sweden)

Jing Zhou

2006-03-01

Full Text Available It is shown that there exists an exact paraxial cold-fluid equilibrium of a high-intensity, space-charge-dominated charged-particle beam with a periodically twisted elliptic cross section in a nonaxisymmetric periodic magnetic field. Generalized envelope equations, which determine the beam envelopes, ellipse orientation, density, and internal flow velocity profiles, are derived. Nonrelativistic and relativistic examples of such beam equilibria are presented. The equilibrium and stability of such beams are demonstrated by self-consistent particle-in-cell (PIC simulations.

Space-Charge-Limited Emission Models for Particle Simulation

Science.gov (United States)

Verboncoeur, J. P.; Cartwright, K. L.; Murphy, T.

2004-11-01

Space-charge-limited (SCL) emission of electrons from various materials is a common method of generating the high current beams required to drive high power microwave (HPM) sources. In the SCL emission process, sufficient space charge is extracted from a surface, often of complicated geometry, to drive the electric field normal to the surface close to zero. The emitted current is highly dominated by space charge effects as well as ambient fields near the surface. In this work, we consider computational models for the macroscopic SCL emission process including application of Gauss's law and the Child-Langmuir law for space-charge-limited emission. Models are described for ideal conductors, lossy conductors, and dielectrics. Also considered is the discretization of these models, and the implications for the emission physics. Previous work on primary and dual-cell emission models [Watrous et al., Phys. Plasmas 8, 289-296 (2001)] is reexamined, and aspects of the performance, including fidelity and noise properties, are improved. Models for one-dimensional diodes are considered, as well as multidimensional emitting surfaces, which include corners and transverse fields.

Whimsicality of multi-mode Hasegawa space-charge waves in a complex plasma containing collision-dominated electrons and streaming ions

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2017-09-01

The influence of collision-dominated electrons on multi-mode Hasegawa space-charge waves are investigated in a complex plasma containing streaming ions. The dispersion relation for the multi-mode Hasegawa space-charge wave propagating in a cylindrical waveguide filled with dusty plasma containing collision-dominated electrons and streaming ions is derived by using the fluid equations and Poisson’s equation which lead to a Bessel equation. By the boundary condition, the roots of the Bessel function would characterize the property of space-charge wave propagation. It is found that two solutions exist for wave frequency, which are affected by the radius of waveguide and the roots of the Bessel function. The damping and growing modes are found to be enhanced by an increase of the radius. However, an increase of electron collision frequency would suppress the damping and the growing modes of the propagating space-charge wave in a cylindrical waveguide plasma.

Direct convertor based upon space charge effects

International Nuclear Information System (INIS)

Gitomer, S.J.

1977-01-01

A device capable of converting directly the kinetic energy of charged particles into electrical energy is considered. The device differs from earlier ones (such as Post's periodic focus electrostatic direct convertor) in that it makes use of the space charge repulsion in a high density charged particle beam. The beam is directed into a monotonic decelerating electrostatic field of a several-stage planar-finned structure. The collector fins coincide with vacuum equipotential surfaces. Space charge blowup of the beam directs particles onto various collector fins. The energy efficiency of a 4-stage device has been determined using a numberical simulation approach. We find that efficiencies approaching 75 percent are possible. An approximate scaling law is derived for the space charge based direct converter and a comparison is made to the periodic focus direct convertor. We find the space charge based direct convertor to be superior to a number of ways

Modal description of longitudinal space-charge fields in pulse-driven free-electron devices

Directory of Open Access Journals (Sweden)

Yu. Lurie

2010-05-01

Full Text Available In pulsed-beam free-electron devices, longitudinal space-charge fields result in collective effects leading to an expansion of short electron bunches along their trajectory. This effect restricts an application of intense ultrashort electron pulses in free-electron radiation sources. A careful theoretical treatment is required in order to achieve an accurate description of the self-fields and the resulted electron beam dynamics. In this paper, longitudinal space-charge fields are considered in the framework of a three-dimensional, space-frequency approach. The model is based on the expansion of the total electromagnetic field (including self-fields in terms of transverse eigenmodes of the (cold cavity, in which the field is excited and propagates. The electromagnetic field, originally obtained in the model as a solution of the wave equation, is shown to satisfy also Gauss’s law. We applied the theory to derive an analytical expression for the longitudinal electric field of a pointlike charge, moving along a waveguide at a constant velocity. This enables consideration and study of the role played by different terms of the resulted expressions, such as components arising from forward and backward waves, propagating waves, and under cutoff frequencies, and so on. Possible simplifications in evaluation of longitudinal space-charge fields are discussed.

Superconducting rf and beam-cavity interactions

International Nuclear Information System (INIS)

Bisognano, J.J.

1987-01-01

Beam-cavity interactions can limit the beam quality and current handling capability of linear and circular accelerators. These collective effects include cumulative and regenerative transverse beam breakup (BBU) in linacs, transverse multipass beam breakup in recirculating linacs and microtrons, longitudinal and transverse coupled-bunch instabilities in storage rings, and a variety of transverse and longitudinal single-bunch phenomena (instabilities, beam breakup, and energy deposition). The superconducting radio frequency (SRF) environment has a number of features which distinguish it from room temperature configuration with regard to these beam-cavity interactions. Typically the unloaded Qs of the lower higher order modes (HOM) are at the 10 9 level and require significant damping through couplers. High gradient CW operation, which is a principal advantage of SRF, allows for better control of beam quality, which for its preservation requires added care which respect to collective phenomena. Gradients are significantly higher than those attainable with copper in CW operation but remain significantly lower than those obtainable with pulsed copper cavities. Finally, energy deposition by the beam into the cavity can occur in a cryogenic environment. In this note those characteristics of beam-cavity interactions which are of particular importance for superconducting RF cavities are highlighted. 6 refs., 4 figs

Ponderomotive enhancement of charged particle beam limiting current

International Nuclear Information System (INIS)

Grebogi, C.; Uhm, H.S.

1987-01-01

The space charge limiting current problem is investigated for a magnetized particle beam propagating in a cylindrical drift tube and in presence of a waveguide mode. It is shown that with a proper choice of a waveguide mode, the limiting current can be greatly enhanced due to ponderomotive effects. Physically, this is accomplished by using the ponderomotive energy to reduce the potential depression due to the beam's self space charge field. Formulas for the limiting current as a function of beam energy and waveguide r.f. field for solid and hollow beams are derived. It is found from these formulas that, in appropriate parameter regimes, the space charge limiting current, say, of a 250kV bem can be enhanced by 70%

Resonance behavior in the presence of space charge

International Nuclear Information System (INIS)

Month, M.; Weng, W.T.

1983-01-01

An analysis is presented of the resonance behavior of particle beams in the presence of space charge fields. Since self-consistent requirements are ignored, the results describe onset or early behavior. It is shown that in a beam of uniform current resonances excited by magnetic field errors are stabilized by the detuning effect of the self-field space charge force. This situation is changed when a radiofrequency accelerating field is applied. As beam bunching results after rf turn-on, the space charge force becomes modulated along the bunches, vanishing at the ends. At these regions of small or vanishing space charge, stabilization from non-linear detuning tends to disappear, thus leaving particles susceptible to resonance blow-up. This picture of the effect of beam bunching can be studied by considering the phase space structure for particles at different positions along the bunches. A somewhat unusual conclusion is made on the use of this analysis to model beam capture in a synchrotron at low energy

Transverse beam cavity interaction. Pt. 1

International Nuclear Information System (INIS)

Weiland, T.

1982-03-01

The transverse interaction between a bunch of charged particles and cylindrically symmetric accelerating structures is studied in three steps. The particle motion is influenced by short range forces and long range forces. The short range forces are calculated by solving Maxwell's equations in the time domain including the presence of free moving charges passing an arbitrarily shaped structure off axis. The long range forces are dominated by resonant modes in cavities. These forces are computed in frequency domain by evaluating eigenmodes and eigenfrequencies. Since only high energy particles are considered, the particle motion, which is affected by both forces, can be studied seperately using simple models and computer simulations. (orig.)

High current electron beam acceleration in dielectric-filled RF cavities

International Nuclear Information System (INIS)

Faehl, R.J.; Keinigs, R.K.

1996-01-01

The acceleration of charged particles in radio frequency (RF) cavities is a widely used mode in high energy accelerators. Advantages include very high accelerating gradients and very stable phase control. A traditional limitation for such acceleration has been their use for intense, high current beam generation. This constraint arises from the inability to store a large amount of electromagnetic energy in the cavity and from loading effects of the beam on the cavity. The authors have studied a simple modification to transcend these limitations. Following Humphries and Huang, they have conducted analytic and numerical investigations of RF accelerator cavities in which a high dielectric constant material, such as water, replaces most of the cavity volume. This raises the stored energy in a cavity of given dimensions by a factor var-epsilon/var-epsilon 0 . For a water fill, var-epsilon/var-epsilon 0 ∼ 80, depending on the frequency. This introduction of high dielectric constant material into the cavity reduces the resonant frequencies by a factor of (var-epsilon/var-epsilon 0 ) 1/2 . This reduced operating frequency mans that existing high efficiency power supplies, at lower frequencies, can be used for an accelerator

Self-consistent simulation studies of periodically focused intense charged-particle beams

International Nuclear Information System (INIS)

Chen, C.; Jameson, R.A.

1995-01-01

A self-consistent two-dimensional model is used to investigate intense charged-particle beam propagation through a periodic solenoidal focusing channel, particularly in the regime in which there is a mismatch between the beam and the focusing channel. The present self-consistent studies confirm that mismatched beams exhibit nonlinear resonances and chaotic behavior in the envelope evolution, as predicted by an earlier envelope analysis [C. Chen and R. C. Davidson, Phys. Rev. Lett. 72, 2195 (1994)]. Transient effects due to emittance growth are studied, and halo formation is investigated. The halo size is estimated. The halo characteristics for a periodic focusing channel are found to be qualitatively the same as those for a uniform focusing channel. A threshold condition is obtained numerically for halo formation in mismatched beams in a uniform focusing channel, which indicates that relative envelope mismatch must be kept well below 20% to prevent space-charge-dominated beams from developing halos

Space-charge driven emittance growth in a 3D mismatched anisotropic beam

International Nuclear Information System (INIS)

Qiang, J.; Ryne, R.D.; Hofmann, I.

2002-01-01

In this paper we present a 3D simulation study of the emittance growth in a mismatched anisotropic beam. The equipartitioning driven by a 4th order space-charge resonance can be significantly modified by the presence of mismatch oscillation and halo formation. This causes emittance growth in both the longitudinal and transverse directions which could drive the beam even further away from equipartition. The averaged emittance growth per degree freedom follows the upper bound of the 2D free energy limit plus the contributions from equipartitioning

Numerical studies of emittance exchange in 2-D charged-particle beams

International Nuclear Information System (INIS)

Guy, F.W.

1986-01-01

We describe results obtained from a two-dimensional particle-following computer code that simulates a continuous, nonrelativistic, elliptical charged-particle beam with linear continuous focusing. Emittances and focusing strengths can be different in the two transverse directions. The results can be applied, for example, for a quadrupole transport system in a smooth approximation to a real beam with unequal emittances in the two planes. The code was used to study emittance changes caused by kinetic-energy exchange between transverse directions and by shifts in charge distributions. Simulation results for space-charge-dominated beams agree well with analytic formulas. From simulation results, an empirical formula was developed for a ''partition parameter'' (the ratio of kinetic energies in the two directions) as a function of initial conditions and beamline length. Quantitative emittance changes for each transverse direction can be predicted by using this parameter. Simulation results also agree with Hofmann's generalized differential equation relating emittance and field energy

POSITION DETERMINATION OF CLOSELY SPACED BUNCHES USING CAVITY BPMs

CERN Document Server

Joshi, N; Cullinan, F; Lyapin, A

2011-01-01

Radio Frequency (RF) Cavity Beam Position Monitor (BPM) systems form a major part of precision position measurement diagnostics for linear accelerators with low emittance beams. Using cavity BPMs, a position resolution of less than 100 nm has been demonstrated in single bunch mode operation. In the case of closely spaced bunches, where the decay time of the cavity is comparable to the time separation between bunches, the BPM signal from a bunch is polluted by the signal induced by the previous bunches in the same bunch-train. This paper discusses our ongoing work to develop the methods to extract the position of closely spaced bunches using cavity BPMs. A signal subtraction code is being developed to remove the signal pollution from previous bunches and to determine the individual bunch position. Another code has been developed to simulate the BPM data for the cross check. Performance of the code is studied on the experimental and simulated data. Application of the analysis techniques to the linear colliders,...

Implementation of Space Charge Forces in BimBim

CERN Document Server

Gottlob, Emmanuel; Oeftiger, Adrian

An numerical algorithm is described for the implementation of linearised coherent space charge forces into BimBim, an eigenvalue solver for the coherent modes of oscillation of multibunch beams in the presence of beam coupling impedance, beam-beam, transverse feedback and now space charge effects. First results obtained with the model are described and compared to existing results where applicable.

Study of space--charge effect by computer

International Nuclear Information System (INIS)

Sasaki, T.

1982-01-01

The space--charge effect in high density electron beams (beam current approx.2 μA) focused by a uniform magnetic field is studied computationally. On an approximation of averaged space-- charge force, a theory of trajectory displacements of beam electrons is developed. The theory shows that the effect of the averaged space--charge force appears as a focal length stretch. The theory is confirmed not only qualitatively but also quantitatively by simulations. Empirical formulas for the trajectory displacement and the energy spread are presented. A comparison between the empirical formulas and some theoretical formulas is made, leading to a severe criticism on the theories of energy spreads

Simulations of longitudinal beam dynamics of space-charge dominated beams for heavy ion fusion

International Nuclear Information System (INIS)

Miller, D.A.C.

1994-12-01

The longitudinal instability has potentially disastrous effects on the ion beams used for heavy ion driven inertial confinement fusion. This instability is a open-quotes resistive wallclose quotes instability with the impedance coining from the induction modules in the accelerator used as a driver. This instability can greatly amplify perturbations launched from the beam head and can prevent focusing of the beam onto the small spot necessary for fusion. This instability has been studied using the WARPrz particle-in-cell code. WARPrz is a 2 1/2 dimensional electrostatic axisymmetric code. This code includes a model for the impedance of the induction modules. Simulations with resistances similar to that expected in a driver show moderate amounts of growth from the instability as a perturbation travels from beam head to tail as predicted by cold beam fluid theory. The perturbation reflects off the beam tail and decays as it travels toward the beam head. Nonlinear effects cause the perturbation to steepen during reflection. Including the capacitive component of the, module impedance. has a partially stabilizing effect on the longitudinal instability. This reduction in the growth rate is seen in both cold beam fluid theory and in simulations with WARPrz. Instability growth rates for warm beams measured from WARPrz are lower than cold beam fluid theory predicts. Longitudinal thermal spread cannot account for this decrease in the growth rate. A mechanism for coupling the transverse thermal spread to decay of the longitudinal waves is presented. The longitudinal instability is no longer a threat to the heavy ion fusion program. The simulations in this thesis have shown that the growth rate for this instability will not be as large as earlier calculations predicted

Significance of Space Charge and the Earth Magnetic Field on the Dispersive Characteristics of a Low Energy Electron Beam

CERN Document Server

Kishek, Rami A; Bernal, Santiago; Godlove, Terry; Haber, Irving; Quinn, Bryan; Reiser, Martin; Tobin, C; Walter, Mark

2005-01-01

The combination of energy spread and space charge provides a rich domain for interesting beam dynamics that are currently not well understood. The University of Maryland Electron Ring (UMER) [1] is a small scaled ring designed to probe the little-known regions of higher beam intensities using low-energy electrons. As such, design, commissioning and operation of UMER present many challenges, some quite novel. For example the UMER beam energy of 10 keV makes the beam very sensitive to the Earth magnetic field, which we can fortunately use to assist in bending the beam. This paper presents a systematic simulation study of the interaction of space charge and energy spread, with and without the earth magnetic field.

Advanced methods for the computation of particle beam transport and the computation of electromagnetic fields and beam-cavity interactions

International Nuclear Information System (INIS)

Dragt, A.J.; Gluckstern, R.L.

1992-11-01

The University of Maryland Dynamical Systems and Accelerator Theory Group carries out research in two broad areas: the computation of charged particle beam transport using Lie algebraic methods and advanced methods for the computation of electromagnetic fields and beam-cavity interactions. Important improvements in the state of the art are believed to be possible in both of these areas. In addition, applications of these methods are made to problems of current interest in accelerator physics including the theoretical performance of present and proposed high energy machines. The Lie algebraic method of computing and analyzing beam transport handles both linear and nonlinear beam elements. Tests show this method to be superior to the earlier matrix or numerical integration methods. It has wide application to many areas including accelerator physics, intense particle beams, ion microprobes, high resolution electron microscopy, and light optics. With regard to the area of electromagnetic fields and beam cavity interactions, work is carried out on the theory of beam breakup in single pulses. Work is also done on the analysis of the high frequency behavior of longitudinal and transverse coupling impedances, including the examination of methods which may be used to measure these impedances. Finally, work is performed on the electromagnetic analysis of coupled cavities and on the coupling of cavities to waveguides

Design of a multi beam klystron cavity from its single beam parameters

Energy Technology Data Exchange (ETDEWEB)

Kant, Deepender, E-mail: dkc@ceeri.ernet.in; Joshi, L. M. [CSIR-Central Electronics Engineering Research Institute, Pilani (India); Janyani, Vijay [Department of ECE, MNIT, Jaipur (India)

2016-03-09

The klystron is a well-known microwave amplifier which uses kinetic energy of an electron beam for amplification of the RF signal. There are some limitations of conventional single beam klystron such as high operating voltage, low efficiency and bulky size at higher power levels, which are very effectively handled in Multi Beam Klystron (MBK) that uses multiple low purveyance electron beams for RF interaction. Each beam propagates along its individual transit path through a resonant cavity structure. Multi-Beam klystron cavity design is a critical task due to asymmetric cavity structure and can be simulated by 3D code only. The present paper shall discuss the design of multi beam RF cavities for klystrons operating at 2856 MHz (S-band) and 5 GHz (C-band) respectively. The design approach uses some scaling laws for finding the electron beam parameters of the multi beam device from their single beam counter parts. The scaled beam parameters are then used for finding the design parameters of the multi beam cavities. Design of the desired multi beam cavity can be optimized through iterative simulations in CST Microwave Studio.

Design of a multi beam klystron cavity from its single beam parameters

International Nuclear Information System (INIS)

Kant, Deepender; Joshi, L. M.; Janyani, Vijay

2016-01-01

The klystron is a well-known microwave amplifier which uses kinetic energy of an electron beam for amplification of the RF signal. There are some limitations of conventional single beam klystron such as high operating voltage, low efficiency and bulky size at higher power levels, which are very effectively handled in Multi Beam Klystron (MBK) that uses multiple low purveyance electron beams for RF interaction. Each beam propagates along its individual transit path through a resonant cavity structure. Multi-Beam klystron cavity design is a critical task due to asymmetric cavity structure and can be simulated by 3D code only. The present paper shall discuss the design of multi beam RF cavities for klystrons operating at 2856 MHz (S-band) and 5 GHz (C-band) respectively. The design approach uses some scaling laws for finding the electron beam parameters of the multi beam device from their single beam counter parts. The scaled beam parameters are then used for finding the design parameters of the multi beam cavities. Design of the desired multi beam cavity can be optimized through iterative simulations in CST Microwave Studio.

Beam loading and cavity compensation for the ground test accelerator

International Nuclear Information System (INIS)

Jachim, S.P.; Natter, E.F.

1989-01-01

The Ground Test Accelerator (GTA) will be a heavily beam-loaded H/sup minus/ linac with tight tolerances on accelerating field parameters. The methods used in modeling the effects of beam loading in this machine are described. The response of the cavity to both beam and radio-frequency (RF) drive stimulus is derived, including the effects of cavity detuning. This derivation is not restricted to a small-signal approximation. An analytical method for synthesizing a predistortion network that decouples the amplitude and phase responses of the cavity is also outlined. Simulation of performance, including beam loading, is achieved through use of a control system analysis software package. A straightforward method is presented for extrapolating this work to model large coupled structures with closely spaced parasitic modes. Results to date have enabled the RF control system designs for GTA to be optimized and have given insight into their operation. 6 refs., 10 figs

Equilibrium phase-space distributions and space charge limits in linacs

International Nuclear Information System (INIS)

Lysenko, W.P.

1977-10-01

Limits on beam current and emittance in proton and heavy ion linear accelerators resulting from space charge forces are calculated. The method involves determining equilibrium distributions in phase space using a continuous focusing, no acceleration, model in two degrees of freedom using the coordinates r and z. A nonlinear Poisson equation must be solved numerically. This procedure is a matching between the longitudinal and transverse directions to minimize the effect of longitudinal-transverse coupling which is believed to be the main problem in emittance growth due to space charge in linacs. Limits on the Clinton P. Anderson Meson Physics Facility (LAMPF) accelerator performance are calculated as an example. The beam physics is described by a few space charge parameters so that accelerators with different physical parameters can be compared in a natural way. The main result of this parameter study is that the requirement of a high-intensity beam is best fulfilled with a low-frequency accelerator whereas the requirement of a high-brightness beam is best fulfilled with a high-frequency accelerator

Internal dynamics and emittance growth in space-charge-dominated beams

International Nuclear Information System (INIS)

Anderson, O.A.

1987-01-01

Previous analytical studies have related transverse rms emittance growth in nonuniform beams to changes in the beam density profile, but the time evolution of the process has not been analyzed. Our new approach analyzes the internal motion of the beam and from this obtains the explicit time dependence of the rms emittance. It is shown to reach its peak value explosively in about one quarter of a plasma period. The subsequent behavior depends on the uniformity of the initial density profile. We derive a uniformity criterion that determines whether or not the emittance oscillates periodically and present examples of density profiles for which the emittance returns to its initial value and then continues to oscillate. We discuss a class of continuous initial profiles that lead to discontinuous shocklike behavior (with partial irreversibility of the oscillations) and a class of segmented profiles for which the emittance jumps to its maximum value in one fourth of a plasma period and remains at that value with essentially no further change. (author)

Ion accumulation and space charge neutralization in intensive electron beams for ion sources and electron cooling

International Nuclear Information System (INIS)

Shirkov, G.D.

1996-01-01

The Electron Beam Ion Sources (EBIS), Electron Beam Ion Traps (EBIT) and electron beams for electron cooling application have the beam parameters in the same ranges of magnitudes. EBIS and EBIT produce and accumulate ions in the beam due to electron impact ionization. The cooling electron beam accumulates positive ions from the residual gas in the accelerator chamber during the cooling cycle. The space charge neutralization of cooling beam is also used to reduce the electron energy spread and enhance the cooling ability. The advanced results of experimental investigations and theoretical models of the EBIS electron beams are applied to analyze the problem of beam neutralization in the electron cooling techniques. The report presents the analysis of the most important processes connected with ion production, accumulation and losses in the intensive electron beams of ion sources and electron cooling systems for proton and ion colliders. The inelastic and elastic collision processes of charged particles in the electron beams are considered. The inelastic processes such as ionization, charge exchange and recombination change the charge states of ions and neutral atoms in the beam. The elastic Coulomb collisions change the energy of particles and cause the energy redistribution among components in the electron-ion beams. The characteristic times and specific features of ionization, beam neutralization, ion heating and loss in the ion sources and electron cooling beams are determined. The dependence of negative potential in the beam cross section on neutralization factor is studied. 17 refs., 5 figs., 1 tab

Incorporating space charge in the transverse phase-space matching and tomography at PITZ

Energy Technology Data Exchange (ETDEWEB)

Kourkafas, Georgios

2015-11-15

The ever-expanding achievements in the field of particle accelerators push their specifications to very demanding levels. The performance of many modern applications depends on their ability to be operated with high bunch charges confined in small volumes. However, the consequence of increased intensity is strong space-charge forces, which perplex the beam manipulation and undermine the beam quality. As a result, reliable methods are needed to control and measure the accelerated particles under these extraordinary conditions. The phase space tomography is a diagnostic technique which can reveal details of the transverse beam parameters for a wide range of intensities and energies, with minimal influence from the machine instabilities, in a quasi non-destructive way. The accuracy of this method relies on the precise knowledge and control of the particle dynamics under the influence of space charge in different stages of the measurement. On the one hand, the matching of the beam to the measurement's design transverse parameters requires a procedure which efficiently compensates the effects of space charge. Depending on the structure of the magnetic lattice, different aspects of these effects prevail, therefore different strategies have to be developed. On the other hand, the impact of the space-charge forces on the phase-space transformations during the data acquisition has to be included in the model which is used for the tomographic reconstruction. The aim of this thesis is to provide and test time-efficient solutions for the incorporation of space charge in the transverse beam matching and phase space tomography.

Incorporating space charge in the transverse phase-space matching and tomography at PITZ

International Nuclear Information System (INIS)

Kourkafas, Georgios

2015-11-01

The ever-expanding achievements in the field of particle accelerators push their specifications to very demanding levels. The performance of many modern applications depends on their ability to be operated with high bunch charges confined in small volumes. However, the consequence of increased intensity is strong space-charge forces, which perplex the beam manipulation and undermine the beam quality. As a result, reliable methods are needed to control and measure the accelerated particles under these extraordinary conditions. The phase space tomography is a diagnostic technique which can reveal details of the transverse beam parameters for a wide range of intensities and energies, with minimal influence from the machine instabilities, in a quasi non-destructive way. The accuracy of this method relies on the precise knowledge and control of the particle dynamics under the influence of space charge in different stages of the measurement. On the one hand, the matching of the beam to the measurement's design transverse parameters requires a procedure which efficiently compensates the effects of space charge. Depending on the structure of the magnetic lattice, different aspects of these effects prevail, therefore different strategies have to be developed. On the other hand, the impact of the space-charge forces on the phase-space transformations during the data acquisition has to be included in the model which is used for the tomographic reconstruction. The aim of this thesis is to provide and test time-efficient solutions for the incorporation of space charge in the transverse beam matching and phase space tomography.

Beam position diagnostics with higher order modes in third harmonic superconducting accelerating cavities

International Nuclear Information System (INIS)

Zhang, Pei

2013-02-01

Higher order modes (HOM) are electromagnetic resonant fields. They can be excited by an electron beam entering an accelerating cavity, and constitute a component of the wakefield. This wakefield has the potential to dilute the beam quality and, in the worst case, result in a beam-break-up instability. It is therefore important to ensure that these fields are well suppressed by extracting energy through special couplers. In addition, the effect of the transverse wakefield can be reduced by aligning the beam on the cavity axis. This is due to their strength depending on the transverse offset of the excitation beam. For suitably small offsets the dominant components of the transverse wakefield are dipole modes, with a linear dependence on the transverse offset of the excitation bunch. This fact enables the transverse beam position inside the cavity to be determined by measuring the dipole modes extracted from the couplers, similar to a cavity beam position monitor (BPM), but requires no additional vacuum instrumentation. At the FLASH facility in DESY, 1.3 GHz (known as TESLA) and 3.9 GHz (third harmonic) cavities are installed. Wakefields in 3.9 GHz cavities are significantly larger than in the 1.3 GHz cavities. It is therefore important to mitigate the adverse effects of HOMs to the beam by aligning the beam on the electric axis of the cavities. This alignment requires an accurate beam position diagnostics inside the 3.9 GHz cavities. It is this aspect that is focused on in this thesis. Although the principle of beam diagnostics with HOM has been demonstrated on 1.3 GHz cavities, the realization in 3.9 GHz cavities is considerably more challenging. This is due to the dense HOM spectrum and the relatively strong coupling of most HOMs amongst the four cavities in the third harmonic cryo-module. A comprehensive series of simulations and HOM spectra measurements have been performed in order to study the modal band structure of the 3.9 GHz cavities. The dependencies of

Beam position diagnostics with higher order modes in third harmonic superconducting accelerating cavities

Energy Technology Data Exchange (ETDEWEB)

Zhang, Pei

2013-02-15

Higher order modes (HOM) are electromagnetic resonant fields. They can be excited by an electron beam entering an accelerating cavity, and constitute a component of the wakefield. This wakefield has the potential to dilute the beam quality and, in the worst case, result in a beam-break-up instability. It is therefore important to ensure that these fields are well suppressed by extracting energy through special couplers. In addition, the effect of the transverse wakefield can be reduced by aligning the beam on the cavity axis. This is due to their strength depending on the transverse offset of the excitation beam. For suitably small offsets the dominant components of the transverse wakefield are dipole modes, with a linear dependence on the transverse offset of the excitation bunch. This fact enables the transverse beam position inside the cavity to be determined by measuring the dipole modes extracted from the couplers, similar to a cavity beam position monitor (BPM), but requires no additional vacuum instrumentation. At the FLASH facility in DESY, 1.3 GHz (known as TESLA) and 3.9 GHz (third harmonic) cavities are installed. Wakefields in 3.9 GHz cavities are significantly larger than in the 1.3 GHz cavities. It is therefore important to mitigate the adverse effects of HOMs to the beam by aligning the beam on the electric axis of the cavities. This alignment requires an accurate beam position diagnostics inside the 3.9 GHz cavities. It is this aspect that is focused on in this thesis. Although the principle of beam diagnostics with HOM has been demonstrated on 1.3 GHz cavities, the realization in 3.9 GHz cavities is considerably more challenging. This is due to the dense HOM spectrum and the relatively strong coupling of most HOMs amongst the four cavities in the third harmonic cryo-module. A comprehensive series of simulations and HOM spectra measurements have been performed in order to study the modal band structure of the 3.9 GHz cavities. The dependencies of

Longitudinal Space Charge in the SPS

CERN Document Server

Lasheen, Alexandre

2016-01-01

Longitudinal instabilities due to the SPS beam coupling impedance are a major issue for future projects and it is essential to have an accurate SPS impedance model to study them. The longitudinal space charge effect can be modelled by a pure reactive impedance and should also be included in simulations as it may have an impact at low energy. In this Note, the effect of the longitudinal space charge in the SPS is evaluated by taking into account the variation of the transverse beam size and vacuum chamber geometry along the ring. Scaling laws are used to investigate what are the most important parameters for the evaluation of the longitudinal space charge impedance.

Intra-cavity vortex beam generation

CSIR Research Space (South Africa)

Naidoo, Darryl

2011-08-01

Full Text Available at exploring the methods of generating optical vortex beams. We will discuss a typical extra-cavity approach that harnesses digital holography through the use of a SLM. We consider vortex beam generation as the fundamental mode of a monolithic microchip laser...-cavity phase diffractive elements can result in the desired mode as the fundamental mode of the cavity with pure modal quality. This approach, although very attractive is insufficient for the generation of these modes in monolithic microchip lasers. A...

Numerical Studies of Electromagnetic Instabilities in Intense Charged Particle Beams with Large Energy Anisotropy

CERN Document Server

Startsev, Edward; Lee, Wei-li

2005-01-01

In intense charged particle beams with large energy anisotropy, free energy is available to drive transverse electromagnetic Weibel-type instabilities. Such slow-wave transverse electromagnetic instabilities can be described by the so-called Darwin model, which neglects the fast-wave portion of the displacement current. The Weibel instability may also lead to an increase in the longitudinal velocity spread, which would make the focusing of the beam difficult and impose a limit on the minimum spot size achievable in heavy ion fusion experiments. This paper reports the results of recent numerical studies of the Weibel instability using the Beam Eigenmode And Spectra (bEASt) code for space-charge-dominated, low-emittance beams with large tune depression. To study the nonlinear stage of the instability, the Darwin model is being developed and incorporated into the Beam Equilibrium Stability and Transport(BEST) code.

Modeling and simulation of a proton beam space-charge neutralization

International Nuclear Information System (INIS)

Fleury, Xavier

2000-01-01

The aim of this work is to understand and to model the build-up of a plasma in the low-energy beam transport line of a proton accelerator. This plasma is generated by the beam, which ionizes the residual gas remaining in this low-energy section. By neutralizing the space-charge of the beam, the plasma modifies its transport, thus, to control the beam, it is necessary to study this phenomenon. In this work, we consider a continuous beam and we take interest in the stationary states of the plasma. We first restrict the description of the plasma to a plane perpendicular to the beam, by assuming that the beam and the plasma are longitudinally invariant. The build-up of the plasma is first described with a kinetic model where binary collisions are neglected, based on the Vlasov-Poisson system with source terms which take into account ionization. We prove mathematically that this system has no stationary solution, by using appropriate subsets of the phase-space that we call trapping-sets. Yet, measurements show that the plasma evolves towards a steady state. To account for this evolution, we modify the source terms of the model. The resulting model is solved by a particle-in-cell method, and the results are compared to the measurements. Then, we show that binary collisions between plasma electrons and beam ions or gas molecules help to maintain the equilibrium of the plasma. In the last part of the thesis, we use hydrodynamic models to investigate more easily the coupling between transversal and longitudinal effects. The preliminary study of a one-dimensional model enables to find the behaviour of the transverse potential of the plasma. Finally, a two-dimensional model of the transport of the beam when it is neutralized by the plasma is solved numerically, which shows that the longitudinal electric field should play an important role in the set-up of the equilibrium of the plasma. (author) [fr

Space-charge calculations in synchrotrons

Energy Technology Data Exchange (ETDEWEB)

Machida, S.

1993-05-01

One obvious bottleneck of achieving high luminosity in hadron colliders, such as the Superconducting Super Collider (SSC), is the beam emittance growth, due to space-charge effects in low energy injector synchrotrons. Although space-charge effects have been recognized since the alternating-gradient synchrotron was invented, and the Laslett tune shift usually calculated to quantify these effects, our understanding of the effects is limited, especially when the Laslett tune shift becomes a large fraction of the integer. Using the Simpsons tracking code, which we developed to study emittance preservation issues in proton synchrotrons, we investigated space-charge effects in the SSC Low Energy Booster (LEB). We observed detailed dependence on parameters such as beam intensity, initial emittance, injection energy, lattice function, and longitudinal motion. A summary of those findings, as well as the tracking technique we developed for the study, are presented.

Electrostatic plasma lens for focusing negatively charged particle beams.

Science.gov (United States)

Goncharov, A A; Dobrovolskiy, A M; Dunets, S M; Litovko, I V; Gushenets, V I; Oks, E M

2012-02-01

We describe the current status of ongoing research and development of the electrostatic plasma lens for focusing and manipulating intense negatively charged particle beams, electrons, and negative ions. The physical principle of this kind of plasma lens is based on magnetic isolation electrons providing creation of a dynamical positive space charge cloud in shortly restricted volume propagating beam. Here, the new results of experimental investigations and computer simulations of wide-aperture, intense electron beam focusing by plasma lens with positive space charge cloud produced due to the cylindrical anode layer accelerator creating a positive ion stream towards an axis system is presented.

A heterogeneous CPU+GPU Poisson solver for space charge calculations in beam dynamics studies

Energy Technology Data Exchange (ETDEWEB)

Zheng, Dawei; Rienen, Ursula van [University of Rostock, Institute of General Electrical Engineering (Germany)

2016-07-01

In beam dynamics studies in accelerator physics, space charge plays a central role in the low energy regime of an accelerator. Numerical space charge calculations are required, both, in the design phase and in the operation of the machines as well. Due to its efficiency, mostly the Particle-In-Cell (PIC) method is chosen for the space charge calculation. Then, the solution of Poisson's equation for the charge distribution in the rest frame is the most prominent part within the solution process. The Poisson solver directly affects the accuracy of the self-field applied on the charged particles when the equation of motion is solved in the laboratory frame. As the Poisson solver consumes the major part of the computing time in most simulations it has to be as fast as possible since it has to be carried out once per time step. In this work, we demonstrate a novel heterogeneous CPU+GPU routine for the Poisson solver. The novel solver also benefits from our new research results on the utilization of a discrete cosine transform within the classical Hockney and Eastwood's convolution routine.

Are topological charge fluctuations in QCD instanton dominated?

International Nuclear Information System (INIS)

Edwards, Robert G.; Heller, Urs M.

2002-01-01

We consider a recent proposal by Horvath et al. to address the question of whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the overlap fermions. Considering several volumes and lattice spacings, we find strong evidence for chirality of a finite density of low-lying eigenvectors of the overlap-Dirac operator in the regions where these modes are peaked. This result suggests instanton dominance of topological charge fluctuations in quenched QCD

Are Topological Charge Fluctuations in QCD Instanton Dominated?

International Nuclear Information System (INIS)

Edwards, Robert G.; Heller, Urs M.

2001-01-01

We consider a recent proposal by Horvath et al. to address the question whether topological charge fluctuations in QCD are instanton dominated via the response of fermions using lattice fermions with exact chiral symmetry, the overlap fermions. Considering several volumes and lattice spacings we find strong evidence for chirality of a finite density of low-lying eigenvectors of the overlap-Dirac operator in the regions where these modes are peaked. This result suggests instanton dominance of topological charge fluctuations in quenched QCD

Space shuttle charging or beam-plasma discharge: What can electron spectrometer observations contribute to solving the question?

International Nuclear Information System (INIS)

Watermann, J.; Wilhelm, K.; Torkar, K.M.; Riedler, W.

1988-01-01

Several cooperative plasma experiments were carried out on board Spacelab-1, the ninth payload of the Space Transportation System (STS-9). Among them, the electron spectrometer 1ES019A was designed to observe 01.-12.5 keV electron fluxes with high temporal and spatial resolution, while the SEPAC electron beam accelerator emitted electron beams with currents up to 280 mA and maximum energies of 5 keV. Since the question of orbiter charging to high voltages has controversially been discussed in several publications on STS-3 and STS-9 electron beam experiments, an attempt is made to relate information from the return electron flux observed during the SEPAC operations to the vehicle charging interpretation. A close examination reveals that most of our observations can be understood if the occurrence of a beam-plasma discharge is assumed at least for electron beam intensities above 100 mA. This would provide a substantial return current capability. High orbiter charging effects during electron beam accelerator electron emissions are consequently not supported by the observations

Beam induced rf cavity transient voltage

International Nuclear Information System (INIS)

Kramer, S.L.; Wang, J.M.

1998-10-01

The authors calculate the transient voltage induced in a radio frequency cavity by the injection of a relativistic bunched beam into a circular accelerator. A simplified model of the beam induced voltage, using a single tone current signal, is generated and compared with the voltage induced by a more realistic model of a point-like bunched beam. The high Q limit of the bunched beam model is shown to be related simply to the simplified model. Both models are shown to induce voltages at the resonant frequency ω r of the cavity and at an integer multiple of the bunch revolution frequency (i.e. the accelerating frequency for powered cavity operation) hω ο . The presence of two nearby frequencies in the cavity leads to a modulation of the carrier wave exp(hω ο t). A special emphasis is placed in this paper on studying the modulation function. These models prove useful for computing the transient voltage induced in superconducting rf cavities, which was the motivation behind this research. The modulation of the transient cavity voltage discussed in this paper is the physical basis of the recently observed and explained new kinds of longitudinal rigid dipole mode which differs from the conventional Robinson mode

Measurement of extent of intense ion beam charge neutralization

Energy Technology Data Exchange (ETDEWEB)

Engelko, V [Efremov Institute of Electrophysical Apparatus, St. Petersburg (Russian Federation); Giese, H; Schalk, S [Forschungszentrum Karlsruhe (Germany). INR

1997-12-31

Various diagnostic tools were employed to study and optimize the extent of space charge neutralization in the pulsed intense proton beam facility PROFA, comprising Langmuir probes, capacitive probes, and a novel type of the three electrode collector. The latter does not only allow us to measure ion and electron beam current densities in a high magnetic field environment, but also to deduce the density spectrum of the beam electrons. Appropriate operating conditions were identified to attain a complete space charge neutralisation. (author). 5 figs., 4 refs.

3D Simulations of Space Charge Effects in Particle Beams

Energy Technology Data Exchange (ETDEWEB)

Adelmann, A

2002-10-01

For the first time, it is possible to calculate the complicated three-dimensional proton accelerator structures at the Paul Scherrer Institut (PSI). Under consideration are external and self effects, arising from guiding and space-charge forces. This thesis has as its theme the design, implementation and validation of a tracking program for charged particles in accelerator structures. This work form part of the discipline of Computational Science and Engineering (CSE), more specifically in computational accelerator modelling. The physical model is based on the collisionless Vlasov-Maxwell theory, justified by the low density ({approx} 10{sup 9} protons/cm{sup 3}) of the beam and of the residual gas. The probability of large angle scattering between the protons and the residual gas is then sufficiently low, as can be estimated by considering the mean free path and the total distance a particle travels in the accelerator structure. (author)

3D Simulations of Space Charge Effects in Particle Beams

International Nuclear Information System (INIS)

Adelmann, A.

2002-10-01

For the first time, it is possible to calculate the complicated three-dimensional proton accelerator structures at the Paul Scherrer Institut (PSI). Under consideration are external and self effects, arising from guiding and space-charge forces. This thesis has as its theme the design, implementation and validation of a tracking program for charged particles in accelerator structures. This work form part of the discipline of Computational Science and Engineering (CSE), more specifically in computational accelerator modelling. The physical model is based on the collisionless Vlasov-Maxwell theory, justified by the low density (∼ 10 9 protons/cm 3 ) of the beam and of the residual gas. The probability of large angle scattering between the protons and the residual gas is then sufficiently low, as can be estimated by considering the mean free path and the total distance a particle travels in the accelerator structure. (author)

Numerical computation of space-charge fields of electron bunches in a beam pipe of elliptical shape

Energy Technology Data Exchange (ETDEWEB)

Markovik, A.

2005-09-28

This work deals in particularly with 3D numerical simulations of space-charge fields from electron bunches in a beam pipe with elliptical cross-section. To obtain the space-charge fields it is necessary to calculate the Poisson equation with given boundary condition and space charge distribution. The discretization of the Poisson equation by the method of finite differences on a Cartesian grid, as well as setting up the coefficient matrix A for the elliptical domain are explained in the section 2. In the section 3 the properties of the coefficient matrix and possible numerical algorithms suitable for solving non-symmetrical linear systems of equations are introduced. In the following section 4, the applied solver algorithms are investigated by numerical tests with right hand side function for which the analytical solution is known. (orig.)

Numerical computation of space-charge fields of electron bunches in a beam pipe of elliptical shape

International Nuclear Information System (INIS)

Markovik, A.

2005-01-01

This work deals in particularly with 3D numerical simulations of space-charge fields from electron bunches in a beam pipe with elliptical cross-section. To obtain the space-charge fields it is necessary to calculate the Poisson equation with given boundary condition and space charge distribution. The discretization of the Poisson equation by the method of finite differences on a Cartesian grid, as well as setting up the coefficient matrix A for the elliptical domain are explained in the section 2. In the section 3 the properties of the coefficient matrix and possible numerical algorithms suitable for solving non-symmetrical linear systems of equations are introduced. In the following section 4, the applied solver algorithms are investigated by numerical tests with right hand side function for which the analytical solution is known. (orig.)

Electron beam interaction with space plasmas.

Science.gov (United States)

Krafft, C.; Bolokitin, A. S.

1999-12-01

Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification.

Stability analysis of Hasegawa space-charge waves in a plasma waveguide with collisional ion beam

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2017-12-01

The dispersion relation for the Hasegawa space-charge wave propagating in a cylindrical waveguide dusty plasma containing collision-dominated ion stream is derived by using the fluid equations and the Poisson equation which lead to a Bessel equation. The solution of Bessel equation is null at the boundary and then the roots of the Bessel function would characterize the property of space-charge wave propagation. We have found that the Hasegawa space-charge wave can be excited for a large axial wave number. The growth rate of excitation increases as the order of the roots of the Bessel function increases. The growth rate decreases with an increase of the radius of cylindrical waveguide as well as with an increase of the collision frequency. We found that the disturbance of wave can be damped only for small wave numbers.

Kinetic equilibrium of space charge dominated beams in a misaligned quadrupole focusing channel

International Nuclear Information System (INIS)

Goswami, A.; Sing Babu, P.; Pandit, V. S.

2013-01-01

The dynamics of intense beam propagation through the misaligned quadrupole focusing channel has been studied in a self-consistent manner using nonlinear Vlasov-Maxwell equations. The equations of motion of the beam centroid have been developed and found to be independent of any specific beam distribution. A Vlasov equilibrium distribution and beam envelope equations have been obtained, which provide us a theoretical tool to investigate the dynamics of intense beam propagating in a misaligned quadrupole focusing channel. It is shown that the displaced quadrupoles only cause the centroid of the beam to wander off axis. The beam envelope around the centroid obeys the familiar Kapchinskij-Vladimirskij envelope equation that is independent of the centroid motion. However, the rotation of the quadrupole about its optical axis affects the beam envelope and causes an increase in the projected emittances in the two transverse planes due to the inter-plane coupling

Focused transport of intense charged particle beams. Final technical report FY/93

International Nuclear Information System (INIS)

1997-01-01

Many recent developments in accelerator technology have increased the need for a better understanding of the physics of intense-beam transport. Of particular interest to the work described here is the appearance, as beam intensities are increased, of a class of nonlinear phenomena which involve the collective interaction of the beam particles. Beam intensity, used as a measure of the importance of space-charge collective behavior, depends on the ratio of current to emittance. The nonlinear beam dynamics, and any resulting emittance growth, which are characteristic of the intense-beam regime, can therefore occur even at low currents in any accelerator system with sufficiently high intensity, especially in the low beta section. Furthermore, since emittance of a beam is difficult to reduce, the ultimate achievement of necessary beam luminosities requires the consideration of possible causes of longitudinal and transverse emittance growth at every stage of the beam lifetime. The research program described here has addressed the fundamental physics which comes into play during the transport, acceleration and focusing of intense beams. Because of the long term and ongoing nature of the research program discussed here, this report is divided into two sections. The first section constitutes a long term revue of the accomplishments which have resulted from the research effort reported, especially in pioneering the use of particle-in-cell (PIC) computer simulation techniques for simulation of the dynamics of space-charge-dominated beams in particle accelerators. The following section emphasizes, in more detail, the accomplishments of the FY 92/93 period immediately prior to the termination of this particular avenue of support. 41 refs

Fast Poisson Solvers for Self-Consistent Beam-Beam and Space-Charge Field Computation in Multiparticle Tracking Simulations

CERN Document Server

Florio, Adrien; Pieloni, Tatiana; CERN. Geneva. ATS Department

2015-01-01

We present two different approaches to solve the 2-dimensional electrostatic problem with open boundary conditions to be used in fast tracking codes for beam-beam and space charge simulations in high energy accelerators. We compare a fast multipoles method with a hybrid Poisson solver based on the fast Fourier transform and finite differences in polar coordinates. We show that the latter outperforms the first in terms of execution time and precision, allowing for a reduction of the noise in the tracking simulation. Furthermore the new algorithm is shown to scale linearly on parallel architectures with shared memory. We conclude by effectively replacing the HFMM by the new Poisson solver in the COMBI code.

Space charge effects in proton linear accelerators

International Nuclear Information System (INIS)

Prome, Michel

1971-01-01

Space charge difficulties are relatively well known because of the inconveniences they cause, but the physical mechanisms by which they operate are obscure; an attempt was made to explain some of these mechanisms. The method chosen involves a numerical simulation of the beam; computer programs describing beam dynamics with space charge are presented; they are used to check results obtained elsewhere. A series of experiments was performed demonstrating that coupling phenomena produce an equalization of r. m. s. velocities in the 3 directions; new quantity (sort of hyper-emittance) is introduced: its growth between the input and output of a given linac is proportional to the beam intensity. (author) [fr

A Method to Overcome Space Charge at Injection

International Nuclear Information System (INIS)

Ya. Derbenev

2005-01-01

The transverse space charge forces in a high current, low energy beam can be reduced by mean of a large increase of the beam's transverse sizes while maintaining the beam area in the 4D phase space. This can be achieved by transforming the beam area in phase space of each of two normal 2D transverse (either plane or circular) modes from a spot shape into a narrow ring of a large amplitude, but homogeneous in phase. Such a transformation results from the beam evolution in the island of a dipole resonance when the amplitude width of the island shrinks adiabatically. After stacking (by using stripping foils or cooling) the beam in such a state and accelerating to energies sufficiently high that the space charge becomes insignificant, the beam then can be returned back to a normal spot shape by applying the reverse transformation. An arrangement that can provide such beam gymnastics along a transport line after a linac and before a booster and/or in a ring with circulating beam will be described and numerical estimates will be presented. Other potential applications of the method will be briefly discussed

Beam tests and operation of superconducting cavities

International Nuclear Information System (INIS)

Akai, Kazunori

1990-01-01

Beam tests and operation of superconducting cavities conducted since the third workshop on RF superconductivity (Argonne, Sep. 1987) are reported in this paper. The paper is concerned particularly with electron machines. Storage and acceleration of the beam are discussed, focusing on the CERN test in SPS, the DESY test in PETRA, the superconducting injector at Darmstadt, and the KEK beam tests in T-AR. Then, long-term performance of the cavity in the ring is discussed focusing on Eacc (max) and O-value, environmental conditions, and operational experience in T-MR. RF controllability is addressed, centering on the Robinson stability, cavity tuning loop, quench detection and interlocks, recovery procedure, field calibration, and phase adjustment. Higher order modes are also discussed. Superconducting cavities have been operated successfully in accelerators. It has been confirmed that the superconducting cavities can be used stably for experimental use. For more than 5000 hours the cavities have indicated no essential degradation of the cavity performance. The study of long-term performance should be continued in longer range of period. (N.K.)

A prototype cavity beam position monitor for the CLIC Main Beam

CERN Document Server

Cullinany , F; Joshi, N; Lyapin, A; Bastard, D; Calvo, E; Chritin, N; Guillot-Vignot, F; Lefevre, T; Søby, L; Wendt, M; Lunin, A; Yakovlev, V P; Smith, S

2012-01-01

The Compact Linear Collider (CLIC) places unprecedented demands on its diagnostics systems. A large number of cavity beam position monitors (BPMs) throughout the main linac and beam delivery system (BDS) must routinely perform with 50 nm spatial resolution. Multiple position measurements within a single 156 ns bunch train are also required. A prototype low-Q cavity beam position monitor has been designed and built to be tested on the CLIC Test Facility (CTF3) probe beam. This paper presents the latest measurements of the prototype cavity BPM and the design and simulation of the radio frequency (RF) signal processing electronics with regards to the final performance. Installation of the BPM in the CTF3 probe beamline is also discussed.

Space charge and magnet error simulations for the SNS accumulator ring

International Nuclear Information System (INIS)

Beebe-Wang, J.; Fedotov, A.V.; Wei, J.; Machida, S.

2000-01-01

The effects of space charge forces and magnet errors in the beam of the Spallation Neutron Source (SNS) accumulator ring are investigated. In this paper, the focus is on the emittance growth and halo/tail formation in the beam due to space charge with and without magnet errors. The beam properties of different particle distributions resulting from various injection painting schemes are investigated. Different working points in the design of SNS accumulator ring lattice are compared. The simulations in close-to-resonance condition in the presence of space charge and magnet errors are presented. (author)

Experimental Results from a Microwave Cavity Beam Position Monitor

International Nuclear Information System (INIS)

Balakin, V.; Bazhan, A.; Lunev, P.; Solyak, N.; Vogel, V.; Zhogolev, P.; Lisitsyn, A.; Yakimenko, V.

1999-01-01

Future Linear Colliders have hard requirements for the beam transverse position stability in the accelerator. A beam Position Monitor (BPM) with the resolution better than 0.1 micron in the single bunch regime is needed to control the stability of the beam position along the linac. Proposed BPM is based on the measurement of the asymmetrical mode excited by single bunch in the cavity. Four stages of signal processing (space-, time-, frequency- and phase-filtering providing the required signal-to-noise ratio) are used to obtain extremely high resolution. The measurement set-up was designed by BINP and installed at ATF/BNL to test experimentally this concept. The set-up includes three two-coordinates BPM's at the frequency of 13.566 GHz, and reference intensity/phase cavity. BPM's were mounted on support table. The two-coordinates movers allow to move and align BPM's along the straight line, using the signals from the beam. The position of each monitor is controlled by the sensors with the accuracy 0.03 micron. The information from three monitors allows to exclude angle and position jitter of the beam and measure BPM resolution. In the experiments the resolution of about 0.15 micron for 0.25 nC beam intensity was obtained, that is close to the value required

Space Charge Mitigation by Hollow Bunches

CERN Multimedia

Oeftiger, AO

2014-01-01

To satisfy the requirements of the HL-LHC (High Luminosity Large Hadron Collider), the LHC injector chain will need to supply a higher brightness, i.e. deliver the same transverse beam emittances \\epsilon_{x,y} while providing a higher intensity N. However, a larger number of particles per bunch enhances space charge effects. One approach to mitigate the impact of space charge is to change the longitudinal phase space distribution: hollow bunches feature a depleted bunch centre and a densely populated periphery. Thus, the spatial line density maximum is depressed which ultimately decreases the tune spread imposed by space charge. Therefore, a higher intensity can be accepted while keeping the same overall space charge tune shift. 3 different methods to create hollow bunches in the PSBooster are simulated.

Pressurized rf cavities in ionizing beams

Directory of Open Access Journals (Sweden)

B. Freemire

2016-06-01

Full Text Available A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SF_{6} and O_{2} were measured.

Microscopic kinetic analysis of space-charge induced optical microbunching in a relativistic electron beam

Directory of Open Access Journals (Sweden)

Agostino Marinelli

2010-11-01

Full Text Available Longitudinal space-charge forces from density fluctuations generated by shot noise can be a major source of microbunching instability in relativistic high brightness electron beams. The gain in microbunching due to this effect is broadband, extending at least up to optical frequencies, where the induced structure on the beam distribution gives rise to effects such as coherent optical transition radiation. In the high-frequency regime, theoretical and computational analyses of microbunching formation require a full three-dimensional treatment. In this paper we address the problem of space-charge induced optical microbunching formation in the high-frequency limit when transverse thermal motion due to finite emittance is included for the first time. We derive an analytical description of this process based on the beam’s plasma dielectric function. We discuss the effect of transverse temperature on the angular distribution of microbunching gain and its connection to the physics of Landau damping in longitudinal plasma oscillations. Application of the theory to a relevant experimental scenario is discussed. The analytical results obtained are then compared to the predictions arising from high resolution three-dimensional molecular dynamics simulations.

Simulation of space charge effects in a synchrotron

International Nuclear Information System (INIS)

Machida, Shinji; Ikegami, Masanori

1998-01-01

We have studied space charge effects in a synchrotron with multi-particle tracking in 2-D and 3-D configuration space (4-D and 6-D phase space, respectively). First, we will describe the modelling of space charge fields in the simulation and a procedure of tracking. Several ways of presenting tracking results will be also mentioned. Secondly, it is discussed as a demonstration of the simulation study that coherent modes of a beam play a major role in beam stability and intensity limit. The incoherent tune in a resonance condition should be replaced by the coherent tune. Finally, we consider the coherent motion of a beam core as a driving force of halo formation. The mechanism is familiar in linac, and we apply it in a synchrotron

SRF cavity alignment detection method using beam-induced HOM with curved beam orbit

Science.gov (United States)

Hattori, Ayaka; Hayano, Hitoshi

2017-09-01

We have developed a method to obtain mechanical centers of nine cell superconducting radio frequency (SRF) cavities from localized dipole modes, that is one of the higher order modes (HOM) induced by low-energy beams. It is to be noted that low-energy beams, which are used as alignment probes, are easy to bend in fringe fields of accelerator cavities. The estimation of the beam passing orbit is important because only information about the beam positions measured by beam position monitors outside the cavities is available. In this case, the alignment information about the cavities can be obtained by optimizing the parameters of the acceleration components over the beam orbit simulation to consistently represent the position of the beam position monitors measured at every beam sweep. We discuss details of the orbit estimation method, and estimate the mechanical center of the localized modes through experiments performed at the STF accelerator. The mechanical center is determined as (x , y) =(0 . 44 ± 0 . 56 mm , - 1 . 95 ± 0 . 40 mm) . We also discuss the error and the applicable range of this method.

Beam-width spreading of vortex beams in free space

Science.gov (United States)

Wang, Weiwei; Li, Jinhong; Duan, Meiling

2018-01-01

Based on the extended Huygens-Fresnel principle and the definition of second-order moments of the Wigner distribution function, the analytical expression for the beam-width spreading of Gaussian Schell-model (GSM) vortex beams in free space are derived, and used to study the influence of beam parameters on the beam-width spreading of GSM vortex beams. With the increment of the propagation distance, the beam-width spreading of GSM vortex beams will increase; the bigger the topological charge, spatial correlation length, wavelength and waist width are, the smaller the beam-width spreading is.

Instability during bunch shortening of an electron-cooled beam

Directory of Open Access Journals (Sweden)

M. Takanaka

2003-10-01

Full Text Available Bunch shortening causes an electron-cooled beam to be space charge dominated at low energies. Instability during the bunch shortening has been studied using a particle-tracking program where the 3D space-charge field due to the beam is calculated with a simplifying model.

Charged corpuscular beam detector

Energy Technology Data Exchange (ETDEWEB)

Hikawa, H; Nishikawa, Y

1970-09-29

The present invention relates to a charged particle beam detector which prevents transient phenomena disturbing the path and focusing of a charged particle beam travelling through a mounted axle. The present invention provides a charged particle beam detector capable of decreasing its reaction to the charge in energy of the charged particle beam even if the relative angle between the mounted axle and the scanner is unstable. The detector is characterized by mounting electrically conductive metal pieces of high melting point onto the face of a stepped, heat-resistant electric insulating material such that the pieces partially overlap each other and individually provide electric signals, whereby the detector is no longer affected by the beam. The thickness of the metal piece is selected so that an eddy current is not induced therein by an incident beam, thus the incident beam is not affected. The detector is capable of detecting a misaligned beam since the metal pieces partially overlap each other.

Beam-Beam Simulation of Crab Cavity White Noise for LHC Upgrade

CERN Document Server

Qiang, J; Pieloni, Tatiana; Ohmi, Kazuhito

2015-01-01

High luminosity LHC upgrade will improve the luminosity of the current LHC operation by an order of magnitude. Crab cavity as a critical component for compensating luminosity loss from large crossing angle collision and also providing luminosity leveling for the LHC upgrade is being actively pursued. In this paper, we will report on the study of potential effects of the crab cavity white noise errors on the beam luminosity lifetime based on strong-strong beam-beam simulations.

Space charge tracking code for a synchrotron accelerator

Energy Technology Data Exchange (ETDEWEB)

Ottinger, M.B.; Tajima, T. [Univ. of Texas, Austin, TX (United States); Hiramoto, K. [Hitachi Ltd., Hitachi, Ibaraki (Japan). Hitachi Research Lab.

1997-06-01

An algorithm has been developed to compute particle tracking, including self-consistent space charge effects for synchrotron accelerators. In low-energy synchrotrons space charge plays a central role in enhancing emittance of the beam. The space charge effects are modeled by mutually interacting (through the Coulombic force) N cylindrical particles (2-{1/2}-dimensional dynamics) whose axis is in the direction of the equilibrium particle flow. On the other hand, their interaction with synchrotron lattice magnets is treated with the thin-lens approximation and in a fully 3-dimensional way. Since the existing method to treat space charge fully self-consistently involved 3-D space charge effect computation, the present method allows far more realistic physical parameters and runs in far shorter time (about 1/20). Some examples on space charge induced instabilities are presented.

Self-excitation of space charge waves

DEFF Research Database (Denmark)

Lyuksyutov, Sergei; Buchhave, Preben; Vasnetsov, Mikhail

1997-01-01

We report a direct observation of space charge waves in photorefractive crystals with point group 23 (sillenites) based on their penetration into an area with uniform light illumination. It is shown experimentally that the quality factor of the waves increases substantially with respect to what c...... current theory predicts [B. Sturman el al., Appl. Phys. A 55, 235 (1992)]. This results in the appearance of strong spontaneous beams caused by space charge wave self-excitation....

Klystron - Space-charge limited flow, guns, Perveance

International Nuclear Information System (INIS)

Isagawa, S.

1999-01-01

This paper treats Thermionic emission, Cathode as an e - emitter, Space-charge limited effect and 3/2 power law, Perveance, Beam spread due to space charge, Pierce guns, Magnetically immersed guns, Method of gun design including simulations, and Examples, mainly treating E3786, which attendees will operate above 1 MW-CW in a practical exercise course at KEK. (author). 74 refs

Electron beam interaction with space plasmas

International Nuclear Information System (INIS)

Krafft, C.; Volokitin, A.S.

1999-01-01

Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification. Recently, theoretical studies of the nonlinear evolution of a thin monoenergetic electron beam injected in a magnetized plasma and interacting with a whistler wave packet have led to new results. The influence of an effective dissipation process connected with whistler wave field leakage out of the beam volume to infinity (that is, effective radiation outside the beam) on the nonlinear evolution of beam electrons distribution in phase space has been studied under conditions relevant to active space experiments and related laboratory modelling. The beam-waves system's evolution reveals the formation of stable nonlinear structures continuously decelerated due to the effective friction imposed by the strongly dissipated waves. The nonlinear interaction between the electron bunches and the wave packet are discussed in terms of dynamic energy exchange, particle trapping, slowing down of the beam, wave dissipation and quasi-linear diffusion. (author)

Phase space model for transmission of light beam

International Nuclear Information System (INIS)

Fu Shinian

1989-01-01

Based on Fermat's principle of ray optics, the Hamiltonian of an optical ray is derived by comparison with classical mechanics. A phase space model of light beam is proposed, assuming that the light beam, regarded as a group of rays, can be described by an ellipse in the μ-phase space. Therefore, the transmission of light beam is represented by the phase space matrix transformation. By means of this non-wave formulation, the same results are obtained as those from wave equation such as Kogelnik's ABCD law. As an example of the application on this model, the matching problem of optical cavity is solved

Divergence in intense ion beams caused by incomplete charge neutralization

International Nuclear Information System (INIS)

Olson, C.L.; Poukey, J.W.

1993-01-01

Space charge neutralization for light ion fusion (LIF) ion beam transport is usually assumed to be perfect in the open-quotes charge-neutralclose quotes region of the diode and in the gas transport cell. However, small charge clumps in the beam will not be totally charge-neutralized, and the residual net space charge may contribute to the beam microdivergence θ μ . If the net potential of the clump is limited only by electron trapping, the minimum potential will be eφ ∼ 1/2 m e v i 2 where m e is the electron mass and v i is the ion velocity. For proton beams this leads to θ μ ∼ (m e /M p ) 1/2 ∼ 23 mrad, where M p is the proton rest mass. For non-protonic beams, different results occur. The mechanism predicts (1) no dependence of θ μ on diode voltage, (2) non-protonic θ μ greater than proton θ μ for proton-contaminated beams, and (3) axial energy spread Δε parallel /ε parallel ∼ ±2 θ μ , which are all consistent with present data. Results of analytic studies and computer simulations of this mechanism are presented. Plasma shielding reduces the effects of this mechanism but collisions and magnetic fields reduce the plasma shielding effects. 2-D PIC MAGIC simulations show that this mechanism contributes to θ μ both in the open-quotes charge-neutralclose quotes region and in the gas transport region. It is concluded that this mechanism is especially important in the open-quotes charge-neutralclose quotes region

Space Charge Effects for the ERL Prototype Injector Line at Daresbury Laboratory

CERN Document Server

Muratori, Bruno; Owen, Hywel; de Loos, Marieke; van der Geer, Bas

2005-01-01

Daresbury Laboratory is currently building an Energy Recovery Linac Prototype (ERLP) that will operate at a beam energy of 35 MeV. In this paper we examine the space charge effects on the beam dynamics in the ERLP injector line. A Gaussian particle distribution is tracked with GPT (General Particle Tracer) through the injection line to the main linac to calculate the effect of 3Dspace charge in the dipoles. The nominal beam energy in the injection line is 8.3 MeV and the bunch charge 80 pC. The effects of space charge on the transverse and longitudinal emittance are studied for various electron beam parameter settings.

Stochastic-hydrodynamic model of halo formation in charged particle beams

Directory of Open Access Journals (Sweden)

Nicola Cufaro Petroni

2003-03-01

Full Text Available The formation of the beam halo in charged particle accelerators is studied in the framework of a stochastic-hydrodynamic model for the collective motion of the particle beam. In such a stochastic-hydrodynamic theory the density and the phase of the charged beam obey a set of coupled nonlinear hydrodynamic equations with explicit time-reversal invariance. This leads to a linearized theory that describes the collective dynamics of the beam in terms of a classical Schrödinger equation. Taking into account space-charge effects, we derive a set of coupled nonlinear hydrodynamic equations. These equations define a collective dynamics of self-interacting systems much in the same spirit as in the Gross-Pitaevskii and Landau-Ginzburg theories of the collective dynamics for interacting quantum many-body systems. Self-consistent solutions of the dynamical equations lead to quasistationary beam configurations with enhanced transverse dispersion and transverse emittance growth. In the limit of a frozen space-charge core it is then possible to determine and study the properties of stationary, stable core-plus-halo beam distributions. In this scheme the possible reproduction of the halo after its elimination is a consequence of the stationarity of the transverse distribution which plays the role of an attractor for every other distribution.

Extraction design and low energy beam transport optimization of space charge dominated multispecies ion beam sources

International Nuclear Information System (INIS)

Delferriere, O.; De Menezes, D.

2004-01-01

In all accelerator projects, the low energy part of the accelerator has to be carefully optimized to match the beam characteristic requirements of the higher energy parts. Since 1994 with the beginning of the Injector of Protons for High Intensity (IPHI) project and Source of Light Ions with High Intensities (SILHI) electron cyclotron resonance (ECR) ion source development at CEA/Saclay, we are using a set of two-dimensional (2D) codes for extraction system optimization (AXCEL, OPERA-2D) and beam transport (MULTIPART). The 95 keV SILHI extraction system optimization has largely increased the extracted current, and improved the beam line transmission. From these good results, a 130 mA D + extraction system for the International Fusion Material Irradiation Facility project has been designed in the same way as SILHI one. We are also now involved in the SPIRAL 2 project for the building of a 40 keV D + ECR ion source, continuously tunable from 0.1 to 5 mA, for which a special four-electrode extraction system has been studied. In this article we will describe the 2D design process and present the different extraction geometries and beam characteristics. Simulation results of SILHI H + beam emittance will be compared with experimental measurements

High current beam transport with multiple beam arrays

International Nuclear Information System (INIS)

Kim, C.H.

1985-05-01

Highlights of recent experimental and theoretical research progress on the high current beam transport of single and multiple beams by the Heavy Ion Fusion Accelerator Research (HIFAR) group at the Lawrence Berkeley Laboratory (LBL) are presented. In the single beam transport experiment (SBTE), stability boundaries and the emittance growth of a space charge dominated beam in a long quadrupole transport channel were measured and compared with theory and computer simulations. Also, a multiple beam ion induction linac (MBE-4) is being constructed at LBL which will permit study of multiple beam transport arrays, and acceleration and bunch length compression of individually focused beamlets. Various design considerations of MBE-4 regarding scaling laws, nonlinear effects, misalignments, and transverse and longitudinal space charge effects are summarized. Some aspects of longitudinal beam dynamics including schemes to generate the accelerating voltage waveforms and to amplify beam current are also discussed

A modified space charge routine for LINAC beam dynamics codes

International Nuclear Information System (INIS)

Valero, S.; Lapostolle, P.; Lombardi, A.M.; Tanke, E.; Warner, D.

1994-01-01

In 1991 a space charge calculation for bunched beams with three-dimensional ellipsoidal symmetry was proposed for the PARMILA code, replacing the usual SCHEFF routines: it removes the cylindrical symmetry needed for the Fast Fourier Transform method and avoids the point to point interaction computation, where the number of simulation points is limited. This routine has now been improved with the introduction of two (or more) ellipsoids, giving a good representation of actual, pear-shaped bunches (unlike the 3-D ellipsoidal assumption). The ellipsoidal density distributions are computed with a new method, avoiding the difficulty caused by statistical effects, encountered near the centre (the axis in 2-D problems) by the previous method. It also provides a check of the ellipsoidal symmetry for each part of the distribution. Finally, the Fourier analysis reported in 1991 has been replaced by a very convenient Hermite expansion, which gives a simple but accurate representation of practical distributions. Introduced in the new, versatile beam dynamics code, DYNAC, it should provide a good tool for the study of the effects of the various parameters responsible for the halo formation in high intensity linacs. (authors). 11 refs

Space-charge-dominated beam dynamics simulations using the massively parallel processors (MPPs) of the Cray T3D

International Nuclear Information System (INIS)

Liu, H.

1996-01-01

Computer simulations using the multi-particle code PARMELA with a three-dimensional point-by-point space charge algorithm have turned out to be very helpful in supporting injector commissioning and operations at Thomas Jefferson National Accelerator Facility (Jefferson Lab, formerly called CEBAF). However, this algorithm, which defines a typical N 2 problem in CPU time scaling, is very time-consuming when N, the number of macro-particles, is large. Therefore, it is attractive to use massively parallel processors (MPPs) to speed up the simulations. Motivated by this, the authors modified the space charge subroutine for using the MPPs of the Cray T3D. The techniques used to parallelize and optimize the code on the T3D are discussed in this paper. The performance of the code on the T3D is examined in comparison with a Parallel Vector Processing supercomputer of the Cray C90 and an HP 735/15 high-end workstation

On the stability of radiation-pressure-dominated cavities

Science.gov (United States)

Kuiper, R.; Klahr, H.; Beuther, H.; Henning, Th.

2012-01-01

Context. When massive stars exert a radiation pressure onto their environment that is higher than their gravitational attraction (super-Eddington condition), they launch a radiation-pressure-driven outflow, which creates cleared cavities. These cavities should prevent any further accretion onto the star from the direction of the bubble, although it has been claimed that a radiative Rayleigh-Taylor instability should lead to the collapse of the outflow cavity and foster the growth of massive stars. Aims: We investigate the stability of idealized radiation-pressure-dominated cavities, focusing on its dependence on the radiation transport approach used in numerical simulations for the stellar radiation feedback. Methods: We compare two different methods for stellar radiation feedback: gray flux-limited diffusion (FLD) and ray-tracing (RT). Both methods are implemented in our self-gravity radiation hydrodynamics simulations for various initial density structures of the collapsing clouds, eventually forming massive stars. We also derive simple analytical models to support our findings. Results: Both methods lead to the launch of a radiation-pressure-dominated outflow cavity. However, only the FLD cases lead to prominent instability in the cavity shell. The RT cases do not show such instability; once the outflow has started, it precedes continuously. The FLD cases display extended epochs of marginal Eddington equilibrium in the cavity shell, making them prone to the radiative Rayleigh-Taylor instability. In the RT cases, the radiation pressure exceeds gravity by 1-2 orders of magnitude. The radiative Rayleigh-Taylor instability is then consequently suppressed. It is a fundamental property of the gray FLD method to neglect the stellar radiation temperature at the location of absorption and thus to underestimate the opacity at the location of the cavity shell. Conclusions: Treating the stellar irradiation in the gray FLD approximation underestimates the radiative forces

Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam

Energy Technology Data Exchange (ETDEWEB)

Thangaraj, J.; Ruan, J.; Johnson, A.S.; Thurman-Keup, R.; Lumpkin, A.H.; Santucci, J.; Sun, Y.-E; Maxwell, T.; Edwards, H.; /Fermilab

2012-05-01

Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.

Space-Charge Experiments at the CERN Proton Synchrotron

CERN Document Server

Franchetti, Giuliano; Hofmann, I; Martini, M; Métral, E; Qiang, J; Ryne, D; Steerenberg, R; CFA Beam Dynamics Workshop “High Intensity and Brightness Hadron Beams”

2005-01-01

Benchmarking of the simulation codes used for the design of the next generation of high beam power accelerators is of paramount importance due to the very demanding requirements on the level of beam losses. This is usually accomplished by comparing simulation results against available theories, and more importantly, against experimental observations. To this aim, a number of well-defined test cases, obtained by accurate measurements made in existing machines, are of great interest. Such measurements have been made in the CERN Proton Synchrotron to probe three space-charge effects: (i) transverse emittance blow-up due to space-charge induced crossing of the integer or half-integer stop-band, (ii) space-charge and octupole driven resonance trapping, and (iii) intensity-dependent emittance transfer between the two transverse planes. The last mechanism is discussed in detail in this paper and compared to simulation predictions.

Charge neutralization of small ion beam clumps

Energy Technology Data Exchange (ETDEWEB)

Welch, D R [Mission Research Corp., Albuquerque, NM (United States); Olson, C L; Hanson, D L [Sandia National Labs., Albuquerque, NM (United States)

1997-12-31

The mega-ampere currents associated with light ion fusion (LIF) require excellent charge neutralization to prevent divergence growth. As the size and space-charge potential of a beam clump or `beamlet` become small (submillimeter size and kilovolt potentials), the neutralization becomes increasingly difficult. Linear theory predicts that plasma electrons cannot neutralize potentials < {phi}{sub crit} = (1/2)m{sub e}v{sub i}{sup 2}/e, where m{sub e} is the electron mass and v{sub i} is the ion beam velocity. A non-uniform beam would, therefore, have regions with potentials sufficient to add divergence to beam clumps. The neutralization of small beamlets produced on the SABLE accelerator and in numerical simulation has supported the theory, showing a plateau in divergence growths as the potential in the beamlet exceeds {phi}{sub crit}. (author). 1 tab., 2 figs., 4 refs.

High-order space charge effects using automatic differentiation

International Nuclear Information System (INIS)

Reusch, Michael F.; Bruhwiler, David L.

1997-01-01

The Northrop Grumman Topkark code has been upgraded to Fortran 90, making use of operator overloading, so the same code can be used to either track an array of particles or construct a Taylor map representation of the accelerator lattice. We review beam optics and beam dynamics simulations conducted with TOPKARK in the past and we present a new method for modeling space charge forces to high-order with automatic differentiation. This method generates an accurate, high-order, 6-D Taylor map of the phase space variable trajectories for a bunched, high-current beam. The spatial distribution is modeled as the product of a Taylor Series times a Gaussian. The variables in the argument of the Gaussian are normalized to the respective second moments of the distribution. This form allows for accurate representation of a wide range of realistic distributions, including any asymmetries, and allows for rapid calculation of the space charge fields with free space boundary conditions. An example problem is presented to illustrate our approach

Development of an S-band cavity-type beam position monitor for a high power THz free-electron laser

Energy Technology Data Exchange (ETDEWEB)

Noh, Seon Yeong; Kim, Eun-San, E-mail: eskim1@knu.ac.kr; Hwang, Ji-Gwang; Heo, A.; Won, Jang Si [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Vinokurov, Nikolay A.; Jeong, Young UK, E-mail: yujung@kaeri.re.kr; Hee Park, Seong; Jang, Kyu-Ha [WCI Center for Quantum-Beam-based Radiation Research, Korea Atomic Energy Research Institute, 989-111 Daedeok-Daero, Yuseong-gu, Daejeon (Korea, Republic of)

2015-01-15

A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultra-short pulsed electron Linac system at the Korea Atomic Energy Research Institute (KAERI). Compared with other types of BPMs, the cavity-type BPM has higher sensitivity and faster response time even at low charge levels. When electron beam passes through the cavity-type BPM, it excites the dipole mode of the cavity of which amplitude depends linearly on the beam offset from the center of the cavity. Signals from the BPM were measured as a function of the beam offset by using an oscilloscope. The microtron accelerator for the KAERI THz FEL produces the electron beam with an energy of 6.5 MeV and pulse length of 5 μs with a micropulse of 10-20 ps at the frequency of 2.801 GHz. The macropulse beam current is 40 mA. Because the microtron provides multi-bunch system, output signal would be the superposition of each single bunch. So high output signal can be obtained from superposition of each single bunch. The designed position resolution of the cavity-type BPM in multi-bunch is submicron. Our cavity-type BPM is made of aluminum and vacuum can be maintained by indium sealing without brazing process, resulting in easy modification and cost saving. The resonance frequency of the cavity-type BPM is 2.803 GHz and the cavity-type BPM dimensions are 200 × 220 mm (length × height) with a pipe diameter of 38 mm. The measured position sensitivity was 6.19 (mV/mm)/mA and the measured isolation between the X and Y axis was −39 dB. By measuring the thermal noise of system, position resolution of the cavity-type BPM was estimated to be less than 1 μm. In this article, we present the test results of the S-band cavity-type BPM and prove the feasibility of the beam position measurement with high resolution using this device.

Development of an S-band cavity-type beam position monitor for a high power THz free-electron laser

Science.gov (United States)

Noh, Seon Yeong; Kim, Eun-San; Hwang, Ji-Gwang; Heo, A.; won Jang, Si; Vinokurov, Nikolay A.; Jeong, Young UK; Hee Park, Seong; Jang, Kyu-Ha

2015-01-01

A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultra-short pulsed electron Linac system at the Korea Atomic Energy Research Institute (KAERI). Compared with other types of BPMs, the cavity-type BPM has higher sensitivity and faster response time even at low charge levels. When electron beam passes through the cavity-type BPM, it excites the dipole mode of the cavity of which amplitude depends linearly on the beam offset from the center of the cavity. Signals from the BPM were measured as a function of the beam offset by using an oscilloscope. The microtron accelerator for the KAERI THz FEL produces the electron beam with an energy of 6.5 MeV and pulse length of 5 μs with a micropulse of 10-20 ps at the frequency of 2.801 GHz. The macropulse beam current is 40 mA. Because the microtron provides multi-bunch system, output signal would be the superposition of each single bunch. So high output signal can be obtained from superposition of each single bunch. The designed position resolution of the cavity-type BPM in multi-bunch is submicron. Our cavity-type BPM is made of aluminum and vacuum can be maintained by indium sealing without brazing process, resulting in easy modification and cost saving. The resonance frequency of the cavity-type BPM is 2.803 GHz and the cavity-type BPM dimensions are 200 × 220 mm (length × height) with a pipe diameter of 38 mm. The measured position sensitivity was 6.19 (mV/mm)/mA and the measured isolation between the X and Y axis was -39 dB. By measuring the thermal noise of system, position resolution of the cavity-type BPM was estimated to be less than 1 μm. In this article, we present the test results of the S-band cavity-type BPM and prove the feasibility of the beam position measurement with high resolution using this device.

Effect of beam arrangement on oral cavity dose in external beam radiotherapy of nasopharyngeal carcinoma

International Nuclear Information System (INIS)

Wu, Vincent W.C.; Yang Zhining; Zhang Wuzhe; Wu Lili; Lin Zhixiong

2012-01-01

This study compared the oral cavity dose between the routine 7-beam intensity-modulated radiotherapy (IMRT) beam arrangement and 2 other 7-beam IMRT with the conventional radiotherapy beam arrangements in the treatment of nasopharyngeal carcinoma (NPC). Ten NPC patients treated by the 7-beam routine IMRT technique (IMRT-7R) between April 2009 and June 2009 were recruited. Using the same computed tomography data, target information, and dose constraints for all the contoured structures, 2 IMRT plans with alternative beam arrangements (IMRT-7M and IMRT-7P) by avoiding the anterior facial beam and 1 conventional radiotherapy plan (CONRT) were computed using the Pinnacle treatment planning system. Dose-volume histograms were generated for the planning target volumes (PTVs) and oral cavity from which the dose parameters and the conformity index of the PTV were recorded for dosimetric comparisons among the plans with different beam arrangements. The dose distributions to the PTVs were similar among the 3 IMRT beam arrangements, whereas the differences were significant between IMRT-7R and CONRT plans. For the oral cavity dose, the 3 IMRT beam arrangements did not show significant difference. Compared with IMRT-7R, CONRT plan showed a significantly lower mean dose, V30 and V-40, whereas the V-60 was significantly higher. The 2 suggested alternative beam arrangements did not significantly reduce the oral cavity dose. The impact of varying the beam angles in IMRT of NPC did not give noticeable effect on the target and oral cavity. Compared with IMRT, the 2-D conventional radiotherapy irradiated a greater high-dose volume in the oral cavity.

Electron cooling of a bunched ion beam in a storage ring

Science.gov (United States)

Zhao, He; Mao, Lijun; Yang, Jiancheng; Xia, Jiawen; Yang, Xiaodong; Li, Jie; Tang, Meitang; Shen, Guodong; Ma, Xiaoming; Wu, Bo; Wang, Geng; Ruan, Shuang; Wang, Kedong; Dong, Ziqiang

2018-02-01

A combination of electron cooling and rf system is an effective method to compress the beam bunch length in storage rings. A simulation code based on multiparticle tracking was developed to calculate the bunched ion beam cooling process, in which the electron cooling, intrabeam scattering (IBS), ion beam space-charge field, transverse and synchrotron motion are considered. Meanwhile, bunched ion beam cooling experiments have been carried out in the main cooling storage ring (CSRm) of the Heavy Ion Research Facility in Lanzhou, to investigate the minimum bunch length obtained by the cooling method, and study the dependence of the minimum bunch length on beam and machine parameters. The experiments show comparable results to those from simulation. Based on these simulations and experiments, we established an analytical model to describe the limitation of the bunch length of the cooled ion beam. It is observed that the IBS effect is dominant for low intensity beams, and the space-charge effect is much more important for high intensity beams. Moreover, the particles will not be bunched for much higher intensity beam. The experimental results in CSRm show a good agreement with the analytical model in the IBS dominated regime. The simulation work offers us comparable results to those from the analytical model both in IBS dominated and space-charge dominated regimes.

Kiloamp high-brightness beams

International Nuclear Information System (INIS)

Caporaso, G.J.

1987-01-01

Brightness preservation of high-current relativistic electron beams under two different types of transport is discussed. Recent progress in improving the brightness of laser-guided beams in the Advanced Test Accelerator is reviewed. A strategy for the preservation of the brightness of space-charge-dominated beams in a solenoidal transport system is presented

Beam extraction dynamics at the space-charge-limit of the high brightness E-XFEL electron source at DESY-PITZ

Energy Technology Data Exchange (ETDEWEB)

Chen, Ye; Gjonaj, Erion; Weiland, Thomas [TEMF, Technische Universitaet Darmstadt, Schlossgartenstrasse 8, 64289 Darmstadt (Germany)

2015-07-01

The physics of the photoemission, as one of the key issues for successful operation of linac based free-electron lasers like the European X-ray Free Electron Laser (E-XFEL) and the Free-electron Laser in Hamburg (FLASH), is playing an increasingly important role in the high brightness DESY-PITZ electron source. We study photoemission physics and discuss full three-dimensional numerical modeling of the electron bunch emission. The beam extraction dynamics at the photocathode has been investigated through the 3D fully electromagnetic (EM) Particle-in-Cell (PIC) solver of CST Particle Studio under the assumption of the photoemission source operating at or close to its space charge limit. PIC simulation results have shown good agreements with measurements on total emitted bunch charge for distinct experimental parameters. Further comparisons showed a general failure for the conventional Poisson solver based tracking algorithm to correctly predict the beam dynamics at the space charge limit. It is furthermore found, that fully EM PIC simulations are also consistent with a simple emission model based on the multidimensional Child-Langmuir law.

Space Charge Effects and Advanced Modelling for CERN Low Energy Machines

CERN Document Server

AUTHOR|(CDS)2088716; Rumolo, Giovanni

The strong space charge regime of future operation of CERN’s circular particle accelerators is investigated and mitigation strategies are developed in the framework of the present thesis. The intensity upgrade of the injector chain of Large Hadron Collider (LHC) prepares the particle accelerators to meet the requirements of the High-Luminosity LHC project. Producing the specified characteristics of the future LHC beams imperatively relies on injecting brighter bunches into the Proton Synchrotron Booster (PSB), the downstream Proton Synchrotron (PS) and eventually the Super Proton Synchrotron (SPS). The increased brightness, i.e. bunch intensity per transverse emittance, entails stronger beam self-fields which can lead to harmful interaction with betatron resonances. Possible beam emittance growth and losses as a consequence thereof threaten to degrade the beam brightness. These space charge effects are partly mitigated by the upgrade of the PSB and PS injection energies. Nevertheless, the space charge tune ...

Analytical & Experimental Study of Radio Frequency Cavity Beam Profile Monitor

Energy Technology Data Exchange (ETDEWEB)

Balcazar, Mario D. [Fermilab; Yonehara, Katsuya [Fermilab

2017-10-22

The purpose of this analytical and experimental study is multifold: 1) To explore a new, radiation-robust, hadron beam profile monitor for intense neutrino beam applications; 2) To test, demonstrate, and develop a novel gas-filled Radio-Frequency (RF) cavity to use in this monitoring system. Within this context, the first section of the study analyzes the beam distribution across the hadron monitor as well as the ion-production rate inside the RF cavity. Furthermore a more effecient pixel configuration across the hadron monitor is proposed to provide higher sensitivity to changes in beam displacement. Finally, the results of a benchtop test of the tunable quality factor RF cavity will be presented. The proposed hadron monitor configuration consists of a circular array of RF cavities located at a radial distance of 7cm { corresponding to the standard deviation of the beam due to scatering { and a gas-filled RF cavity with a quality factor in the range 400 - 800.

Effect of the space-charge force on tracking at low energy

International Nuclear Information System (INIS)

Furman, M.A.

1987-01-01

The authors present tracking results for the SSC's Low Energy Booster at injection energy, including the effect of the space-charge force. The bunches are assumed to be gaussian with elliptical cross-section. Magnet errors and sextupoles are not included, but an RF cavity is. The authors compare the phase space with and without synchrotron oscillations, with and without space-charge. The effective emittance is not significantly altered. They also present results on tune shifts with amplitude

Analysis of ultra-relativistic charged particle beam and stretched wire measurement interactions with cylindrically symmetric structures

International Nuclear Information System (INIS)

Deibele, C.E.

1996-01-01

The beam impedance and wakefield are quantities which describe the stability of charged particles in their trajectory within an accelerator. The stretched wire measurement technique is a method which estimates the beam impedance and wakefield. Definitions for the beam impedance, the wakefield, and the stretched wire measurement are presented. A pillbox resonator with circular beampipes is studied for its relatively simple profile and mode structure. Theoretical predictions and measurement data are presented for the interaction of various charged particle beams and center conductor geometries between the cavity and beampipe. Time domain predictions for the stretched wire measurement and wakefield are presented and are shown to be a linear interaction

Automatic Phase Calibration for RF Cavities using Beam-Loading Signals

Energy Technology Data Exchange (ETDEWEB)

Edelen, J. P. [Fermilab; Chase, B. E. [Fermilab

2017-10-01

Precise calibration of the cavity phase signals is necessary for the operation of any particle accelerator. For many systems this requires human in the loop adjustments based on measurements of the beam parameters downstream. Some recent work has developed a scheme for the calibration of the cavity phase using beam measurements and beam-loading however this scheme is still a multi-step process that requires heavy automation or human in the loop. In this paper we analyze a new scheme that uses only RF signals reacting to beam-loading to calculate the phase of the beam relative to the cavity. This technique could be used in slow control loops to provide real-time adjustment of the cavity phase calibration without human intervention thereby increasing the stability and reliability of the accelerator.

Dynamics of ion beam charge neutralization by ferroelectric plasma sources

Energy Technology Data Exchange (ETDEWEB)

Stepanov, Anton D.; Gilson, Erik P.; Grisham, Larry R.; Kaganovich, Igor D.; Davidson, Ronald C. [Princeton Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)

2016-04-15

Ferroelectric Plasma Sources (FEPSs) can generate plasma that provides effective space-charge neutralization of intense high-perveance ion beams, as has been demonstrated on the Neutralized Drift Compression Experiment NDCX-I and NDCX-II. This article presents experimental results on charge neutralization of a high-perveance 38 keV Ar{sup +} beam by a plasma produced in a FEPS discharge. By comparing the measured beam radius with the envelope model for space-charge expansion, it is shown that a charge neutralization fraction of 98% is attainable with sufficiently dense FEPS plasma. The transverse electrostatic potential of the ion beam is reduced from 15 V before neutralization to 0.3 V, implying that the energy of the neutralizing electrons is below 0.3 eV. Measurements of the time-evolution of beam radius show that near-complete charge neutralization is established ∼5 μs after the driving pulse is applied to the FEPS and can last for 35 μs. It is argued that the duration of neutralization is much longer than a reasonable lifetime of the plasma produced in the sub-μs surface discharge. Measurements of current flow in the driving circuit of the FEPS show the existence of electron emission into vacuum, which lasts for tens of μs after the high voltage pulse is applied. It is argued that the beam is neutralized by the plasma produced by this process and not by a surface discharge plasma that is produced at the instant the high-voltage pulse is applied.

Space charge effect in the spiral inflector

International Nuclear Information System (INIS)

Toprek, Dragan

2000-01-01

This paper presents the analytical and numerical theory of the space charge effects in the beam in the spiral inflector. It considers a simplified model of a 'straight' cylindrical beam by using a uniform particle distribution. Numerical results represented in this paper are obtained by using a modified version of the program CASINO

Space-Charge Effects in a Gas Detector

Energy Technology Data Exchange (ETDEWEB)

Ryutov, D.D.

2010-12-03

Discussion of space-charge effects in a photoluminescence cell that will be used as a nondisruptive total energy monitor at the LCLS facility is presented. Regimes where primary photoelectrons will be confined within the X-ray beam aperture are identified. Effects of the space-charge on the further evolution of the electron and ion populations are discussed. Parameters of the afterglow plasma are evaluated. Conditions under which the detector output will be proportional to the pulse energy are defined.

On some practical consideration of the electron beam breakup transit time oscillator

International Nuclear Information System (INIS)

Kwan, T.J.T.

1992-01-01

The electron beam breakup transit time oscillator (BTO) makes use of the interaction between an electron beam and the azimuthally azimuthally asymmetric transverse magnetic mode (TM 110 ) of a cavity to facilitate the exchange of energy between them. Linear theory has shown a large growth rate in the regime where space-charge effects can be ignored. In this study, we have investigated the non-ideal elements in the BTO and evaluated their effects accordingly. The practical issues under consideration are electron beam quality, energy, and space-charge potential. Our calculations indicate only a modest unfavorable scalings with respect to these parameters

Intra-cavity decomposition of a dual-directional laser beam

CSIR Research Space (South Africa)

Naidoo, Darryl

2011-01-01

Full Text Available A method of decomposing a dual-directional laser beam into a forward propagating field and a backward propagating field for an apertured plano-concave cavity is presented. An intra-cavity aperture is a simple method of laser beam shaping as higher...

High-order space charge effects using automatic differentiation

International Nuclear Information System (INIS)

Reusch, M.F.; Bruhwiler, D.L.; Computer Accelerator Physics Conference Williamsburg, Virginia 1996)

1997-01-01

The Northrop Grumman Topkark code has been upgraded to Fortran 90, making use of operator overloading, so the same code can be used to either track an array of particles or construct a Taylor map representation of the accelerator lattice. We review beam optics and beam dynamics simulations conducted with TOPKARK in the past and we present a new method for modeling space charge forces to high-order with automatic differentiation. This method generates an accurate, high-order, 6-D Taylor map of the phase space variable trajectories for a bunched, high-current beam. The spatial distribution is modeled as the product of a Taylor Series times a Gaussian. The variables in the argument of the Gaussian are normalized to the respective second moments of the distribution. This form allows for accurate representation of a wide range of realistic distributions, including any asymmetries, and allows for rapid calculation of the space charge fields with free space boundary conditions. An example problem is presented to illustrate our approach. copyright 1997 American Institute of Physics

Anisotropy-Driven Instability in Intense Charged Particle Beams

CERN Document Server

Startsev, Edward; Qin, Hong

2005-01-01

In electrically neutral plasmas with strongly anisotropic distribution functions, free energy is available to drive different collective instabilities such as the electrostatic Harris instability and the transverse electromagnetic Weibel instability. Such anisotropies develop naturally in particle accelerators and may lead to a detoriation of beam quality. We have generalized the analysis of the classical Harris and Weibel instabilities to the case of a one-component intense charged particle beam with anisotropic temperature including the important effects of finite transverse geometry and beam space-charge. For a long costing beam, the delta-f particle-in-cell code BEST and the eighenmode code bEASt have been used to determine detailed 3D stability properties over a wide range of temperature anisotropy and beam intensity. A theoretical model is developed which describes the essential features of the linear stage of these instabilities. Both, the simulations and analytical theory, clearly show that moderately...

DART: a simulation code for charged particle beams

International Nuclear Information System (INIS)

White, R.C.; Barr, W.L.; Moir, R.W.

1988-01-01

This paper presents a recently modified verion of the 2-D DART code designed to simulate the behavior of a beam of charged particles whose paths are affected by electric and magnetic fields. This code was originally used to design laboratory-scale and full-scale beam direct converters. Since then, its utility has been expanded to allow more general applications. The simulation technique includes space charge, secondary electron effects, and neutral gas ionization. Calculations of electrode placement and energy conversion efficiency are described. Basic operation procedures are given including sample input files and output. 7 refs., 18 figs

Development of a high-resolution cavity-beam position monitor

Directory of Open Access Journals (Sweden)

Yoichi Inoue

2008-06-01

Full Text Available We have developed a high-resolution cavity-beam position monitor (BPM to be used at the focal point of the ATF2, which is a test beam line that is now being built to demonstrate stable orbit control at ∼nanometer resolution. The design of the cavity structure was optimized for the Accelerator Test Facility (ATF beam in various ways. For example, the cavity has a rectangular shape in order to isolate two dipole modes in orthogonal directions, and a relatively thin gap that is less sensitive to trajectory inclination. A two stage homodyne mixer with highly sensitive electronics and phase-sensitive detection was also developed. Two BPM blocks, each containing two cavity BPMs, were installed in the existing ATF beam line using a rigid support frame. After testing the basic characteristics, we measured the resolution using three BPMs. The system demonstrated 8.7 nm position resolution over a dynamic range of 5  μm.

Development of a high-resolution cavity-beam position monitor

Science.gov (United States)

Inoue, Yoichi; Hayano, Hitoshi; Honda, Yosuke; Takatomi, Toshikazu; Tauchi, Toshiaki; Urakawa, Junji; Komamiya, Sachio; Nakamura, Tomoya; Sanuki, Tomoyuki; Kim, Eun-San; Shin, Seung-Hwan; Vogel, Vladimir

2008-06-01

We have developed a high-resolution cavity-beam position monitor (BPM) to be used at the focal point of the ATF2, which is a test beam line that is now being built to demonstrate stable orbit control at ˜nanometer resolution. The design of the cavity structure was optimized for the Accelerator Test Facility (ATF) beam in various ways. For example, the cavity has a rectangular shape in order to isolate two dipole modes in orthogonal directions, and a relatively thin gap that is less sensitive to trajectory inclination. A two stage homodyne mixer with highly sensitive electronics and phase-sensitive detection was also developed. Two BPM blocks, each containing two cavity BPMs, were installed in the existing ATF beam line using a rigid support frame. After testing the basic characteristics, we measured the resolution using three BPMs. The system demonstrated 8.7 nm position resolution over a dynamic range of 5μm.

DART: A simulation code for charged particle beams

International Nuclear Information System (INIS)

White, R.C.; Barr, W.L.; Moir, R.W.

1989-01-01

This paper presents a recently modified version of the 2-D code, DART, which can simulate the behavior of a beam of charged particles whose trajectories are determined by electric and magnetic fields. This code was originally used to design laboratory-scale and full-scale beam direct converters. Since then, its utility has been expanded to allow more general applications. The simulation includes space charge, secondary electrons, and the ionization of neutral gas. A beam can contain up to nine superimposed beamlets of different energy and species. The calculation of energy conversion efficiency and the method of specifying the electrode geometry are described. Basic procedures for using the code are given, and sample input and output fields are shown. 7 refs., 18 figs

Minimization of the emittance growth of multi-charge particle beams in the charge stripping section of RAON

Energy Technology Data Exchange (ETDEWEB)

Hwang, Ji-Gwang [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Eun-San, E-mail: eskim1@knu.ac.kr [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Hye-Jin, E-mail: hjkim87@ibs.re.kr [Rare Isotope Science Project, Institute for Basic Science, Jeonmin-dong, Yuseong-gu, Daejeon (Korea, Republic of); Jeon, Dong-O [Rare Isotope Science Project, Institute for Basic Science, Jeonmin-dong, Yuseong-gu, Daejeon (Korea, Republic of)

2014-12-11

The charge stripping section of the Rare isotope Accelerator Of Newness (RAON), which is one of the critical components to achieve a high power of 400 kW with a short lianc, is a source of transverse emittance growth. The dominant effects are the angular straggling in the charge stripper required to increase the charge state of the beam and chromatic aberrations in the dispersive section required to separate the selected ion beam from the various ion beams produced in the stripper. Since the main source of transverse emittance growth in the stripper is the angular straggling, it can be compensated for by changing the angle of the phase ellipse. Therefore the emittance growth is minimized by optimizing the Twiss parameters at the stripper. The emittance growth in the charge selection section is also minimized by the correction of high-order aberrations using six sextupole magnets. In this paper, we present a method to minimize the transverse emittance growth in the stripper by changing the Twiss parameters and in the charge selection section by using sextupole magnets.

The Effects of Space-Charge on the Dynamics of the Ion Booster in the Jefferson Lab EIC (JLEIC)

Energy Technology Data Exchange (ETDEWEB)

Bogacz, Alex [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Nissen, Edward [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

2017-05-01

Optimization of the booster synchrotron design to operate in the extreme space-charge dominated regime is proposed. This study is motivated by the ultra-high luminosity promised by the JLEIC accelerator complex, which poses several beam dynamics and lattice design challenges for its individual components. We examine the effects of space charge on the dynamics of the booster synchrotron for the proposed JLEIC electron ion collider. This booster will inject and accumulate protons and heavy ions at an energy of 280 MeV and then engage in a process of acceleration and electron cooling to bring it to its extraction energy of 8 GeV. This would then be sent into the ion collider ring part of JLEIC. In order to examine the effects of space charge on the dynamics of this process we use the software SYNERGIA.

Deflecting cavity for beam diagnostics at Cornell ERL injector

International Nuclear Information System (INIS)

Belomestnykh, Sergey; Bazarov, Ivan; Shemelin, Valery; Sikora, John; Smolenski, Karl; Veshcherevich, Vadim

2010-01-01

A single-cell, 1300-MHz, TM110-like mode vertically deflecting cavity is designed and built for beam slice emittance measurements, and to study the temporal response of negative electron affinity photocathodes in the ERL injector at Cornell University. We describe the cavity shape optimization procedure, RF and mechanical design, its performance with beam.

On the physics of electron beams in space plasmas

International Nuclear Information System (INIS)

Krafft, C.; Volokitin, A.

2002-01-01

This paper discusses the main physical processes related to the injection, the propagation and the radiation of electron beams in space plasmas as the Earth's ionosphere. The physical mechanisms are shortly explained and illustrated with several examples of experimental results provided by various space missions. In a first part, we discuss important physical processes connected with the response of the ambient space plasma to the beam injection, and in particular, with the mechanisms of electric charge neutralization of the electron beam and of the payload carrying the injector, with the widely studied phenomenon of beam-plasma discharge as well as with the physical features of the spatio-temporal evolution and the dynamic structure of the beam in its interaction with the plasma and the emitted waves. In a second part, the main processes governing the wave emission by electron beams in space are examined; in particular, we focus on the physical linear and nonlinear mechanisms involved in the generation, the stabilization and the saturation of the electromagnetic waves excited by the beams in wide frequency ranges. and the radiation of electron beams in space plasmas as the Earth's ionosphere. The physical mechanisms are shortly explained and illustrated with several examples of experimental results provided by various space missions. In a first part, we discuss important physical processes connected with the response of the ambient space plasma to the beam injection, and in particular, with the mechanisms of electric charge neutralization of the electron beam and of the payload carrying the injector, with the widely studied phenomenon of beam-plasma discharge as well as with the physical features of the spatio-temporal evolution and the dynamic structure of the beam in its interaction with the plasma and the emitted waves. In a second part, the main processes governing the wave emission by electron beams in space are examined; in particular, we focus on the

Benchmark of Space Charge Simulations and Comparison with Experimental Results for High Intensity, Low Energy Accelerators

CERN Document Server

Cousineau, Sarah M

2005-01-01

Space charge effects are a major contributor to beam halo and emittance growth leading to beam loss in high intensity, low energy accelerators. As future accelerators strive towards unprecedented levels of beam intensity and beam loss control, a more comprehensive understanding of space charge effects is required. A wealth of simulation tools have been developed for modeling beams in linacs and rings, and with the growing availability of high-speed computing systems, computationally expensive problems that were inconceivable a decade ago are now being handled with relative ease. This has opened the field for realistic simulations of space charge effects, including detailed benchmarks with experimental data. A great deal of effort is being focused in this direction, and several recent benchmark studies have produced remarkably successful results. This paper reviews the achievements in space charge benchmarking in the last few years, and discusses the challenges that remain.

Interaction of IREB with a cavity

International Nuclear Information System (INIS)

Sawhney, R.; Mishra, Mamta; Purkayastha, A.D.; Rambabu, P.; Maheshwari, K.P.

1991-01-01

The propagation of an intense pulsed relativistic electron beam (IREB) through a cavity resonator is considered. The cavity gets shock excited. The electromagnetic fields so generated interact with the beam in such a way that the energy is transferred from the front of the beam to the back. As a result the beams gets energized but shortened in time. Analysis for the chosen dominant mode of the cavity viz. TMsub(010) is carried out. The induced electric field excited is calculated and the accelerating potential is estimated. The results are compared with the recent-experiments. (author). 5 refs., 1 fig

Higher order mode spectra and the dependence of localized dipole modes on the transverse beam position in third harmonic superconducting cavities at FLASH

Energy Technology Data Exchange (ETDEWEB)

Zhang, Pei [Manchester Univ. (United Kingdom); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Baboi, Nicoleta [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Jones, Roger M. [The Cockcroft Institute, Daresbury (United Kingdom)

2012-06-15

An electron beam entering an accelerating cavity excites a wakefield. This wakefield can be decomposed into a series of multi-poles or modes. The dominant component of the transverse wakefield is dipole. This report summarizes the higher order mode (HOM) signals of the third harmonic cavities of FLASH measured at various stages: transmission measurements in the single cavity test stand at Fermilab, at CMTB (Cryo- Module Test Bench) and at FLASH, and beam-excited measurements at FLASH. Modes in the first two dipole bands and the fifth dipole band have been identified using a global Lorentzian fit technique. The beam-pipe modes at approximately 4 GHz and some modes in the fifth dipole band have been observed as localized modes, while the first two dipole bands, containing some strong coupling cavity modes, propagate. This report also presents the dependence of the localized dipole modes on the transverse beam position. Linear dependence for various modes has been observed. This makes them suitable for beam position diagnostics. These modes, together with some propagating, strong coupling modes, have been considered in the design of a dedicated electronics for beam diagnostics with HOMs for the third harmonic cavities.

Deflection system for charged-particle beam

Energy Technology Data Exchange (ETDEWEB)

Bates, T

1982-01-13

A system is described for achromatically deflecting a beam of charged particles without producing net divergence of the beam comprising three successive magnetic deflection means which deflect the beam alternately in opposite directions; the first and second deflect by angles of less than 50/sup 0/ and the third by an angle of at least 90/sup 0/. Particles with different respective energies are transversely spaced as they enter the third deflection means, but emerge completely superimposed in both position and direction and may be brought to a focus in each of two mutually perpendicular planes, a short distance thereafter. Such a system may be particularly compact, especially in the direction in which the beam leaves the system. It is suitable for deflecting a beam of electrons from a linear accelerator so producing a vertical beam of electron (or with an X-ray target, of X-rays) which can be rotated about a horizontal patient for radiation therapy.

Cavity Cooling a Single Charged Levitated Nanosphere

Science.gov (United States)

Millen, J.; Fonseca, P. Z. G.; Mavrogordatos, T.; Monteiro, T. S.; Barker, P. F.

2015-03-01

Optomechanical cavity cooling of levitated objects offers the possibility for laboratory investigation of the macroscopic quantum behavior of systems that are largely decoupled from their environment. However, experimental progress has been hindered by particle loss mechanisms, which have prevented levitation and cavity cooling in a vacuum. We overcome this problem with a new type of hybrid electro-optical trap formed from a Paul trap within a single-mode optical cavity. We demonstrate a factor of 100 cavity cooling of 400 nm diameter silica spheres trapped in vacuum. This paves the way for ground-state cooling in a smaller, higher finesse cavity, as we show that a novel feature of the hybrid trap is that the optomechanical cooling becomes actively driven by the Paul trap, even for singly charged nanospheres.

Space-charge effects of the proportional counters in a multiple-ionization chamber

International Nuclear Information System (INIS)

Mang, M.

1993-01-01

At the ALADIN spectrometer of the GSI in october 1991 for the first time the new multiple ionization chamber was applied, in the two anode planes of which are additional multiwire-proportional counters. The proportional counters are required in order to make the detection of light fragments (Z 4 gold projectiles per second by these positive space charges the homogeneous electric field of the MUSIC is disturbed. This effect is especially strong in the beam plane. As consequence of the space charge additionally electrons are focused on the proportional counter so that their amplitudes in dependence on the beam intensity increase up to the 2.5-fold. Furthermore the y coordinate is falsified, because the electrons are diverted to the medium plane. On the measurement of the x coordinate this diversion has with maximally 0.1% only a small influence. These space-charge effects can be qualitatively described by a schematic model, which assumes a stationary positive space charge. Additionally for the proportional counters, which are not in the beam plane, their resolution was determined. In these counters the space-charge effects are small, because essentially fewer particles are registrated than in the medium MWPC's. By this charges of fragments with Z<10 could be separated. The charge resolution amounted at lithium 0.8 charge units. The position resolution of the proportional counters in y direction was determined to less than 8 mm. The detection probability of the fragments amounts for lithium 90% and from boron all fragments are detected

CAVITY BEAM POSITION MONITOR SYSTEM FOR ATF2

CERN Document Server

Boogert, S T; Cullinan, F; Joshi, N; Lyapin, A; Aryshev, A; Honda, Y; Naito, T; Terunuma, N; Urakara, J; Heo, A; Kim, E-S; Kim, Y I; McCormick, D; Frisch, J; Nelson, J; Smith, T; White, G R

2011-01-01

The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 41 high resolution C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitisers. In addition 4 high resolution BPMs have been recently installed at the interaction point, we briefly describe the first operational experience of these cavities in the ATF2 beam-line. The current status of the overall BPM system is also described, with a focus on operational techniques and performance.

Moment approach to charged particle beam dynamics

International Nuclear Information System (INIS)

Channell, P.J.

1983-01-01

We have derived the hierarchy of moment equations that describes the dynamics of charged-particle beams in linear accelerators and can truncate the hierarchy at any level either by discarding higher moments or by a cumulant expansion discarding only correlation functions. We have developed a procedure for relating the density expansion linearly to the moments to any order. The relation of space-charge fields to the density has been derived; and an accurate, systematic, and computationally convenient expansion of the resultant integrals has been developed

Ferroelectric plasma source for heavy ion beam space charge neutralization

International Nuclear Information System (INIS)

Efthimion, Philip C.; Gilson, Erik P.; Davidson, Ronald C.; Grisham, Larry; Grant Logan, B.; Seidl, Peter A.; Waldron, William; Yu, Simon S.

2007-01-01

Plasmas are a source of unbound electrons for charge neutralizing intense heavy ion beams to allow them to focus to a small spot size and compress their axial pulse length. The plasma source should be able to operate at low neutral pressures and without strong externally applied electric or magnetic fields. To produce 1 m-long plasma columns, sources based upon ferroelectric ceramics with large dielectric coefficients are being developed. The sources utilize the ferroelectric ceramic BaTiO 3 to form metal plasma. The drift tube inner surface of the Neutralized Drift Compression Experiment (NDCX) will be covered with ceramic material, and high voltage (∼7 kV) will be applied between the drift tube and the front surface of the ceramics. A prototype ferroelectric source, 20 cm in length, has produced plasma densities of 5x10 11 cm -3 . It was integrated into the Neutralized Transport Experiment (NTX), and successfully charge neutralized the K + ion beam. A 1 m-long source comprised of five 20-cm-long sources has been tested. Simply connecting the five sources in parallel to a single pulse forming network power supply yielded non-uniform performance due to the time-dependent nature of the load that each of the five plasma sources experiences. Other circuit combinations have been considered, including powering each source by its own supply. The 1-m-long source has now been successfully characterized, producing relatively uniform plasma over the 1 m length of the source in the mid-10 10 cm -3 density range. This source will be integrated into the NDCX device for charge neutralization and beam compression experiments

Cavity design and beam simulations for the APS rf gun

International Nuclear Information System (INIS)

Borland, M.

1991-01-01

An earlier note discussed the preliminary design of the 1-1/2 cell RF cavity for the APS RF gun. This note describes the final design, including cavity properties and simulation results from the program rf gun. The basic idea for the new design was that the successful SSRL design could be improved upon by reducing fields that had nonlinear dependence on radius. As discussed previously, this would reduce the emittance and produce tighter momentum and time distributions. In addition, it was desirable to increase the fields in the first half-cell relative to the fields in the second half-cell, in order to allow more rapid initial acceleration, which would reduce the effects of space charge. Both of these goals were accomplished in the new design

Space charge effects in a bending magnet system

International Nuclear Information System (INIS)

Lee, E.P.; Close, E.; Smith, L.

1987-03-01

In order to examine problems and phenomena associated with space charge in a beam bending system, the beam dynamics code HICURB has been written. Its principal features include momentum variations, vertical and horizontal envelope dynamics coupled to the off-axis centroid, curvature effect on fields, and images. Preliminary results for an achromatic lattice configuration are presented

Space charge effects in a bending magnet system

International Nuclear Information System (INIS)

Lee, E.P.; Close, E.; Smith, L.

1987-01-01

In order to examine problems and phenomena associated with space charge in a beam bending system, the beam dynamics code HICURB has been written. Its principal features include momentum variations, vertical and horizontal envelope dynamics coupled to the off-axis centroid, curvature effect on fields, and images. Preliminary results for an achromatic lattice configuration are presented

CALIBRATION ERRORS IN THE CAVITY BEAM POSITION MONITOR SYSTEM AT THE ATF2

CERN Document Server

Cullinan, F; Joshi, N; Lyapin, A

2011-01-01

It has been shown at the Accelerator Test Facility at KEK, that it is possible to run a system of 37 cavity beam position monitors (BPMs) and achieve high working resolution. However, stability of the calibration constants (position scale and radio frequency (RF) phase) over a three/four week running period is yet to be demonstrated. During the calibration procedure, random beam jitter gives rise to a statistical error in the position scale and slow orbit drift in position and tilt causes systematic errors in both the position scale and RF phase. These errors are dominant and have been evaluated for each BPM. The results are compared with the errors expected after a tested method of beam jitter subtraction has been applied.

Polarization of electron-beam irradiated LDPE films: contribution to charge generation and transport

Science.gov (United States)

Banda, M. E.; Griseri, V.; Teyssèdre, G.; Le Roy, S.

2018-04-01

Electron-beam irradiation is an alternative way to generate charges in insulating materials, at controlled position and quantity, in order to monitor their behaviour in regard to transport phenomena under the space charge induced electric field or external field applied. In this study, low density polyethylene (LDPE) films were irradiated by a 80 keV electron-beam with a flux of 1 nA cm‑2 during 10 min in an irradiation chamber under vacuum conditions, and were then characterized outside the chamber using three experimental methods. The electrical behaviour of the irradiated material was assessed by space charge measurements using the pulsed electro-acoustic (PEA) method under dc stress. The influence of the applied electric field polarity and amplitude has been tested in order to better understand the charge behaviour after electron-beam irradiation. Fourier transform infra-red spectroscopy (FTIR) and photoluminescence (PL) measurements were performed to evaluate the impact of the electron beam irradiation, i.e. deposited charges and energy, on the chemical structure of the irradiated samples. The present results show that the electrical behaviour in LDPE after irradiation is mostly driven by charges, i.e. by physical process functions of the electric field, and that changes in the chemical structure seems to be mild.

WAVEGUIDE COUPLER KICK TO BEAM BUNCH AND CURRENT DEPENDENCY ON SRF CAVITIES

International Nuclear Information System (INIS)

Genfa Wu; Haipeng Wang; Charles Reece; Robert Rimmer

2008-01-01

JLAB SRF cavities employ waveguide type fundamental power couplers (FPC). The FPC design for the 7-cell upgrade cavities was optimized to minimize the dipole field kick. For continuous wave (CW) operation, the forwarding RF power will be at different magnitude to drive the different beam current and cavity gradient. This introduces some deviation from optimized FPC field for varying beam loading. This article analyzes the beam behavior both in centroid kick and head-tail kick under different beam loading conditions

SNS accumulator ring design and space charge considerations

International Nuclear Information System (INIS)

Weng, W.T.

1998-01-01

The goal of the proposed Spallation Neutron Source (SNS) is to provide a short pulse proton beam of about 0.5micros with average beam power of 1MW. To achieve such purpose, a proton storage ring operated at 60Hz with 1 x 10 14 protons per pulse at 1GeV is required. The Accumulator Ring (AR) receives 1msec long H - beam bunches of 28mA from a 1GeV linac. Scope and design performance goals of the AR are presented. About 1,200 turns of charge exchange injection is needed to accumulate 1mA in the ring. After a brief description of the lattice design and machine performance parameters, space charge related issues, such as: tune shifts, stopband corrections, halo generation and beam collimation etc. is discussed

Mode stability analysis in the beam—wave interaction process for a three-gap Hughes-type coupled cavity chain

International Nuclear Information System (INIS)

Luo Ji-Run; Zhu Min; Guo Wei; Cui Jian

2013-01-01

Based on space-charge wave theory, the formulae of the beam—wave coupling coefficient and the beam-loaded conductance are given for the beam—wave interaction in an N-gap Hughes-type coupled cavity chain. The ratio of the non-beam-loaded quality factor of the coupled cavity chain to the beam quality factor is used to determine the stability of the beam—wave interaction. As an example, the stabilities of the beam—wave interaction in a three-gap Hughes-type coupled cavity chain are discussed with the formulae and the CST code for the operations of the 2π, π, and π/2 modes, respectively. The results show that stable operation of the 2π, π, and π/2 modes may all be realized in an extended-interaction klystron with the three-gap Hughes-type coupled cavity chain

Space-charge effects on bunching of electrons in the CEBAF injector

International Nuclear Information System (INIS)

Liu, H.

1997-01-01

The main injector for the 4 GeV CEBAF accelerator at Thomas Jefferson national accelerator facility was designed to deliver simultaneously three CW electron beams for nuclear physics research. The maximum design current for a single beam from the injector is 100 μA, or 0.2 pC per microbunch at a repetition rate of 499 MHz. It was found through computer simulation that space charge even at a subpicocoulomb level can spoil the bunching of electrons significantly, and some unexpected phenomena observed experimentally could be explained accordingly. This problem arises because of the low-momentum tilt allowed for bunching to preserve low-momentum spread. In this paper, we analyze in detail the space-charge effects on bunching of electrons with the CEBAF injector as an example. Conditions for effective matching of longitudinal phase space in the presence of space charge are discussed. (orig.)

Beam dynamics aspects of crab cavities in the CERN Large Hadron Collider

CERN Document Server

Sun, Y P; Barranco, J; Tomás, R; Weiler, T; Zimmermann, F; Calaga, R; Morita, A

2009-01-01

Modern colliders bring into collision a large number of bunches to achieve a high luminosity. The long-range beam-beam effects arising from parasitic encounters at such colliders are mitigated by introducing a crossing angle. Under these conditions, crab cavities (CC) can be used to restore effective head-on collisions and thereby to increase the geometric luminosity. Such crab cavities have been proposed for both linear and circular colliders. The crab cavities are rf cavities operated in a transverse dipole mode, which imparts on the beam particles a transverse kick that varies with the longitudinal position along the bunch. The use of crab cavities in the Large Hadron Collider (LHC) may not only raise the luminosity, but it could also complicate the beam dynamics, e.g., crab cavities might not only cancel synchrobetatron resonances excited by the crossing angle but they could also excite new ones, they could reduce the dynamic aperture for off-momentum particles, they could influence the aperture and orbit...

Submacropulse electron-beam dynamics correlated with higher-order modes in Tesla-type superconducting rf cavities

Directory of Open Access Journals (Sweden)

A. H. Lumpkin

2018-06-01

Full Text Available We report the direct observations of submacropulse beam centroid oscillations correlated with higher order modes (HOMs which were generated by off-axis electron beam steering in TESLA-type superconducting rf cavities. The experiments were performed at the Fermilab Accelerator Science and Technology (FAST facility using its unique configuration of a photocathode rf gun injecting beam into two separated nine-cell cavities in series with corrector magnets and beam position monitors (BPMs located before, between, and after them. Oscillations of ∼100  kHz in the vertical plane and ∼380  kHz in the horizontal plane with up to 600-μm amplitudes were observed in a 3-MHz micropulse repetition rate beam with charges of 100, 300, 500, and 1000  pC/b. However, the effects were much reduced at 100  pC/b. The measurements were based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch array data, imaging cameras, and a framing camera. Calculations reproduced the oscillation frequencies of the phenomena in the vertical case. In principle, these fundamental results may be scaled to cryomodule configurations of major accelerator facilities.

Transient behaviour of a ``beam loaded`` prebuncher cavity and linac structure

Energy Technology Data Exchange (ETDEWEB)

Messina, Giovanni; Picardi, Luigi; Ronsivalle, Concetta; Vignati, Angelo [ENEA, Centro Ricerche Frascati, Rome (Italy)

1997-03-01

They present the evaluation of the effect of the beam loading on the time response of a 3 GHz prebuncher cavity to the generator and to an input 120 deg chopped electron beam for two different cavity materials. The lumped-element representation of the cavity as a parallel RLC circuit is used which allows to compute also the sensitivity of the prebuncher voltage amplitude and phase with respect to beam current fluctuations. The analysis has been extended to the transient behaviour of a linac positioned after the prebuncher cavity. The consequences of the computation results on the application of a chopper-prebuncher system in a linac devoted to the MUH FEL experiment are discussed.

Cavity beam position monitor system for the Accelerator Test Facility 2

Science.gov (United States)

Kim, Y. I.; Ainsworth, R.; Aryshev, A.; Boogert, S. T.; Boorman, G.; Frisch, J.; Heo, A.; Honda, Y.; Hwang, W. H.; Huang, J. Y.; Kim, E.-S.; Kim, S. H.; Lyapin, A.; Naito, T.; May, J.; McCormick, D.; Mellor, R. E.; Molloy, S.; Nelson, J.; Park, S. J.; Park, Y. J.; Ross, M.; Shin, S.; Swinson, C.; Smith, T.; Terunuma, N.; Tauchi, T.; Urakawa, J.; White, G. R.

2012-04-01

The Accelerator Test Facility 2 (ATF2) is a scaled demonstrator system for final focus beam lines of linear high energy colliders. This paper describes the high resolution cavity beam position monitor (BPM) system, which is a part of the ATF2 diagnostics. Two types of cavity BPMs are used, C-band operating at 6.423 GHz, and S-band at 2.888 GHz with an increased beam aperture. The cavities, electronics, and digital processing are described. The resolution of the C-band system with attenuators was determined to be approximately 250 nm and 1μm for the S-band system. Without attenuation the best recorded C-band cavity resolution was 27 nm.

Progress on the Design of a Perpendicularly Biased 2nd Harmonic Cavity for the Fermilab Booster

Energy Technology Data Exchange (ETDEWEB)

Madrak, R. L. [Fermilab; Dey, J. E. [Fermilab; Duel, K. L. [Fermilab; Kuharik, J. C. [Fermilab; Pellico, W. A. [Fermilab; Reid, J. S. [Fermilab; Romanov, G. [Fermilab; Slabough, M. [Fermilab; Sun, D. [Fermilab; Tan, C. Y. [Fermilab; Terechkine, I. [Fermilab

2016-10-01

perpendicularly biased 2nd harmonic cavity is being designed and built for the Fermilab Booster. Its purpose is to flatten the bucket at injection and thus change the longitudinal beam distribution to decrease space charge effects. It can also help at extraction. The cavity frequency range is 76 – 106 MHz. The power amplifier will be built using the Y567B tetrode, which is also used for the fundamental mode cavities in the Fermilab Booster. We discuss recent progress on the cavity, the biasing solenoid design and plans for testing the tuner's garnet material

Space charge and wake field analysis for a high brightness electron source

International Nuclear Information System (INIS)

Parsa, Z.

1991-01-01

We present a brief overview of the formalism used, and some simulation results for transverse and longitudinal motion of a bunch of particles moving through a cavity (e.g., the Brookhaven National Laboratory high brightness photocathode gun), including effects of the accelerating field, space charge forces (e.g., arising from the interaction of the cavity surface and the self field of the bunch). 3 refs., 12 figs

Multiple beam envelope equations for electron injectors using a bunch segmentation model

Directory of Open Access Journals (Sweden)

A. Mizuno

2012-06-01

Full Text Available A new semianalytical method of investigating the beam dynamics for electron injectors was developed. In this method, a short bunched electron beam is assumed to be an ensemble of several segmentation pieces in both the longitudinal and the transverse directions. The trajectory of each electron in the segmentation pieces is solved by the beam envelope equations while taking into account the space charge fields produced by all the pieces, the electromagnetic fields of an rf cavity, and the image charge fields at a cathode surface. The shape of the entire bunch is consequently calculated, and thus the emittances can be obtained from weighted mean values of the solutions for the obtained electron trajectories. The advantage of this method is its unique assumption for the beam parameters. We assume that each segmentation slice is not warped in the calculations. Although if the beam energy is low and the charge density is large, this condition is not satisfied, in practice, this condition is usually satisfied. We have performed beam dynamics calculations to obtain traces in free space and in the BNL-type rf gun cavity by comparing the analytical solutions with those obtained by simulation. In most cases, the emittances obtained by the simulation become closer to those obtained analytically with increasing the number of particles used in the simulation. Therefore, the analytically obtained emittances are expected to coincide with converged values obtained by the simulation. The applicable range of the analytical method for the BNL-type rf gun cavity is under 0.5 nC per bunch. This range is often used in recently built x-ray free electron laser facilities.

Space-charge limits in linear accelerators

International Nuclear Information System (INIS)

Wangler, T.P.

1980-12-01

This report presents equations that allow an approximate evaluation of the limiting beam current for a large class of radio-frequency linear accelerators, which use quadrupole strong focusing. Included are the Alvarez, the Wideroe, and the radio-frequency quadrupole linacs. The limiting-current formulas are presented for both the longitudinal and the transverse degrees of freedom by assuming that the average space-charge force in the beam bunch arises from a uniformly distributed charge within an azimuthally symmetric three-dimensional ellipsoid. The Mathieu equation is obtained as an approximate, but general, form for the transverse equation of motion. The smooth-approximation method is used to obtain a solution and an expression for the transverse current limit. The form of the current-limit formulas for different linac constraints is discussed

LONGITUDINAL MISMATCH IN SCL AS A SOURCE OF BEAM HALO.

Energy Technology Data Exchange (ETDEWEB)

RUGGIERO,A.G.

2003-06-19

An advantage of a proton Super-conducting Linac (SCL) is that RF cavities can be operated independently, allowing easier beam transport: and acceleration. But cavities are to be separated by drifts long enough to avoid they couple to each other. Moreover, cavities are placed in cryostats that include inactive insertions for cold-warm transitions; and interspersed are warm insertions for magnets and other devices. The SCL is then an alternating sequence of accelerating elements and drifts. No periodicity is present, and the longitudinal motion is not adiabatic. This has the consequence that the beam bunch ellipse will tumble, dilute and create a halo in the momentum plane because of inherent nonlinearities. When this is coupled to longitudinal space-charge forces, it may cause beam loss with latent activation of the accelerator components.

SNS accumulator ring design and space charge considerations

Energy Technology Data Exchange (ETDEWEB)

Weng, W.T.

1998-08-01

The goal of the proposed Spallation Neutron Source (SNS) is to provide a short pulse proton beam of about 0.5 {micro}s with average beam power of 1 MW. To achieve such purpose, a proton storage ring operated at 60 Hz with 1 {times} 10{sup 14} protons per pulse at 1 GeV is required. The Accumulator Ring (AR) receives 1 msec long H{sup {minus}} beam bunches of 28 mA from a 1 GeV linac. Scope and design performance goals of the AR are presented. About 1,200 turns of charge exchange injection is needed to accumulate 1 mA in the ring. After a brief description of the lattice design and machine performance parameters, space charge related issues, such as: tune shifts, stopband corrections, halo generatino and beam collimation etc. is discussed.

SNS ACCUMULATOR RING DESIGN AND SPACE CHARGE CONSIDERATIONS

Energy Technology Data Exchange (ETDEWEB)

WENG,W.T.

1998-05-04

The goal of the proposed Spallation Neutron Source (SNS) is to provide a short pulse proton beam of about 0.5{micro}s with average beam power of 1MW. To achieve such purpose, a proton storage ring operated at 60Hz with 1 x 10{sup 14} protons per pulse at 1GeV is required. The Accumulator Ring (AR) receives 1msec long H{sup {minus}} beam bunches of 28mA from a 1GeV linac. Scope and design performance goals of the AR are presented. About 1,200 turns of charge exchange injection is needed to accumulate 1mA in the ring. After a brief description of the lattice design and machine performance parameters, space charge related issues, such as: tune shifts, stopband corrections, halo generation and beam collimation etc. is discussed.

Cancellation of the centrifugal space-charge force

International Nuclear Information System (INIS)

Lee, E.P.

1990-01-01

The transverse dynamics of high-energy electrons confined in curved geometry are examined, including the effects of space-charge-induced fields. Attention is restricted to the centrifugal-space-charge force, which is the result of noncancellation of beam-induced transverse electric and magnetic fields in the curved geometry. This force is shown to be nearly cancelled in the evaluation of the horizontal tune and chromaticity by another, often overlooked term in the equation of motion. The additional term is the consequence of oscillations of the kinetic energy, which accompany betatron oscillations in the beam-induced electric potential. In curved geometry this term is of first order in the amplitude of the radial oscillation. A highly simplified system model is employed so that physical effects appear in as clear a form as possible. We assume azimuthal and median plane symmetry, static fields, and ultrarelativistic particle velocity (1/γ 2 ->0). (author) 9 refs

Space charge physics for particle accelerators

CERN Document Server

Hofmann, Ingo

2017-01-01

Understanding and controlling the physics of space charge effects in linear and circular proton and ion accelerators are essential to their operation, and to future high-intensity facilities. This book presents the status quo of this field from a theoretical perspective, compares analytical approaches with multi-particle computer simulations and – where available – with experiments. It discusses fundamental concepts of phase space motion, matched beams and modes of perturbation, along with mathematical models of analysis – from envelope to Vlasov-Poisson equations. The main emphasis is on providing a systematic description of incoherent and coherent resonance phenomena; parametric instabilities and sum modes; mismatch and halo; error driven resonances; and emittance exchange due to anisotropy, as well as the role of Landau damping. Their distinctive features are elaborated in the context of numerous sample simulations, and their potential impacts on beam quality degradation and beam loss are discussed....

Cavity beam position monitor system for the Accelerator Test Facility 2

Directory of Open Access Journals (Sweden)

Y. I. Kim

2012-04-01

Full Text Available The Accelerator Test Facility 2 (ATF2 is a scaled demonstrator system for final focus beam lines of linear high energy colliders. This paper describes the high resolution cavity beam position monitor (BPM system, which is a part of the ATF2 diagnostics. Two types of cavity BPMs are used, C-band operating at 6.423 GHz, and S-band at 2.888 GHz with an increased beam aperture. The cavities, electronics, and digital processing are described. The resolution of the C-band system with attenuators was determined to be approximately 250 nm and 1  μm for the S-band system. Without attenuation the best recorded C-band cavity resolution was 27 nm.

Method for varying the diameter of a beam of charged particles

International Nuclear Information System (INIS)

Ko, W.C.; Sawatzky, E.

1977-01-01

In the bombardment of targets with beams of charged particles, a method is described for varying and controlling the diameter of such beams by passing the beam through an envelope of conductive material. The envelope is spaced from and coaxial with the beam. A selected dc potential is applied to the envelope, and the beam diameter is controlled by changing this applied potential in a direction away from ground potential to increase the beam diameter or by changing the potential in a direction toward ground potential to decrease said beam diameter

Intra-cavity metamorphosis of a Gaussian beam to flat-top distribution

CSIR Research Space (South Africa)

Naidoo, Darryl

2014-02-01

Full Text Available We explore an intra-cavity beam shaping approach to generate a Gaussian distribution by the metamorphosis of a Gaussian beam into a flat-top distribution on opposing mirrors. The concept is tested external to the cavity through the use of two...

The space charge effects on the slow extraction process

International Nuclear Information System (INIS)

Ohmori, Chihiro.

1992-06-01

The calculation of the slow extraction which includes the space charge effects has been performed for the Compressor/Stretcher Ring (CSR) of the proposed Japanese Hadron Project. We have investigated the slow extraction of 1 GeV proton beam with an average current of 100μA. Calculation shows not only the emittance growth of the extracted beam but also decrease of the extraction efficiency and discontinuity of beam spill. (author)

Intra–cavity flat–top beam generation

CSIR Research Space (South Africa)

Litvin, IA

2009-08-01

Full Text Available In this paper the authors present the analytical and numerical analyses of two new resonator systems for generating flat–top–like beams. Both approaches lead to closed form expressions for the required cavity optics, but differ substantially...

Performance of a reentrant cavity beam position monitor

Directory of Open Access Journals (Sweden)

Claire Simon

2008-08-01

Full Text Available The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs. In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryomodule, work at cryogenic temperature in a clean environment. It has achieved a resolution better than 10  μm and has the possibility to perform bunch to bunch measurements for the x-ray free electron laser (X-FEL and the International Linear Collider (ILC. Its other features are a small size of the rf cavity, a large aperture (78 mm, and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH, at Deutsches Elektronen-Synchrotron (DESY and demonstrated its operation at cryogenic temperature inside a cryomodule. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately 4  μm over a dynamic range ±5  mm in single bunch.

Performance of a reentrant cavity beam position monitor

International Nuclear Information System (INIS)

Simon, C.; Luong, M.; Chel, S.; Napoly, O.; Novo, J.; Roudier, D.; Rouviere, N.; Baboi, N.; Mildner, N.; Nolle, D.

2008-01-01

The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs). In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryo-module, work at cryogenic temperature in a clean environment. It has achieved a resolution better than 10 μm and has the possibility to perform bunch to bunch measurements for the X-ray free electron laser (X-FEL) and the International Linear Collider (ILC). Its other features are a small size of the rf cavity, a large aperture (78 mm), and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH), at Deutsches Elektronen-Synchrotron (DESY) and demonstrated its operation at cryogenic temperature inside a cryo-module. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately 4 μm over a dynamic range ± 5 mm in single bunch. (authors)

Performance of a reentrant cavity beam position monitor

Science.gov (United States)

Simon, Claire; Luong, Michel; Chel, Stéphane; Napoly, Olivier; Novo, Jorge; Roudier, Dominique; Rouvière, Nelly; Baboi, Nicoleta; Mildner, Nils; Nölle, Dirk

2008-08-01

The beam-based alignment and feedback systems, essential operations for the future colliders, require high resolution beam position monitors (BPMs). In the framework of the European CARE/SRF program, a reentrant cavity BPM with its associated electronics was developed by the CEA/DSM/Irfu in collaboration with DESY. The design, the fabrication, and the beam test of this monitor are detailed within this paper. This BPM is designed to be inserted in a cryomodule, work at cryogenic temperature in a clean environment. It has achieved a resolution better than 10μm and has the possibility to perform bunch to bunch measurements for the x-ray free electron laser (X-FEL) and the International Linear Collider (ILC). Its other features are a small size of the rf cavity, a large aperture (78 mm), and an excellent linearity. A first prototype of a reentrant cavity BPM was installed in the free electron laser in Hamburg (FLASH), at Deutsches Elektronen-Synchrotron (DESY) and demonstrated its operation at cryogenic temperature inside a cryomodule. The second, installed, also, in the FLASH linac to be tested with beam, measured a resolution of approximately 4μm over a dynamic range ±5mm in single bunch.

Absolute beam-charge measurement for single-bunch electron beams

International Nuclear Information System (INIS)

Suwada, Tsuyoshi; Ohsawa, Satoshi; Furukawa, Kazuro; Akasaka, Nobumasa

2000-01-01

The absolute beam charge of a single-bunch electron beam with a pulse width of 10 ps and that of a short-pulsed electron beam with a pulse width of 1 ns were measured with a Faraday cup in a beam test for the KEK B-Factory (KEKB) injector linac. It is strongly desired to obtain a precise beam-injection rate to the KEKB rings, and to estimate the amount of beam loss. A wall-current monitor was also recalibrated within an error of ±2%. This report describes the new results for an absolute beam-charge measurement for single-bunch and short-pulsed electron beams, and recalibration of the wall-current monitors in detail. (author)

The influence of spherical cavity surface charge distribution on the sequence of partial discharge events

International Nuclear Information System (INIS)

Illias, Hazlee A; Chen, George; Lewin, Paul L

2011-01-01

In this work, a model representing partial discharge (PD) behaviour of a spherical cavity within a homogeneous dielectric material has been developed to study the influence of cavity surface charge distribution on the electric field distribution in both the cavity and the material itself. The charge accumulation on the cavity surface after a PD event and charge movement along the cavity wall under the influence of electric field magnitude and direction has been found to affect the electric field distribution in the whole cavity and in the material. This in turn affects the likelihood of any subsequent PD activity in the cavity and the whole sequence of PD events. The model parameters influencing cavity surface charge distribution can be readily identified; they are the cavity surface conductivity, the inception field and the extinction field. Comparison of measurement and simulation results has been undertaken to validate the model.

The influence of spherical cavity surface charge distribution on the sequence of partial discharge events

Energy Technology Data Exchange (ETDEWEB)

Illias, Hazlee A [Department of Electrical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Chen, George; Lewin, Paul L, E-mail: h.illias@um.edu.my [Tony Davies High Voltage Laboratory, School of Electronics and Computer Science, University of Southampton, Southampton, SO17 1BJ (United Kingdom)

2011-06-22

In this work, a model representing partial discharge (PD) behaviour of a spherical cavity within a homogeneous dielectric material has been developed to study the influence of cavity surface charge distribution on the electric field distribution in both the cavity and the material itself. The charge accumulation on the cavity surface after a PD event and charge movement along the cavity wall under the influence of electric field magnitude and direction has been found to affect the electric field distribution in the whole cavity and in the material. This in turn affects the likelihood of any subsequent PD activity in the cavity and the whole sequence of PD events. The model parameters influencing cavity surface charge distribution can be readily identified; they are the cavity surface conductivity, the inception field and the extinction field. Comparison of measurement and simulation results has been undertaken to validate the model.

THI: goal reached with a carbon beam, and some results of beam tests and theoretical studies related to longitudinal space charge effects

International Nuclear Information System (INIS)

Anon.

1999-01-01

During the first semester of this year, two tests were devoted to high intensity beams: 1) trying to reach the ultimate goal with a carbon beam and 2) going further into the study of perturbing phenomena. A 1.3 x 10 13 pps 13 C beam was successfully extracted from SSC2 and sustained for 13 hours with an excellent stability. Then, the current was increased to 2 x 10 13 pps with no major problem. Therefore, it is possible from now on to bombard the 2 kW target which is prepared for the production of helium isotopes and subsequent acceleration in the new cyclotron CIME. Both experimental and simulation studies were carried in parallel, in the frame of the last year expertise, in order to get a better knowledge and control of the effect of longitudinal space charge forces. It appears that these effects affect the beam width mostly in SSC2, while a discrepancy between computer simulations and measurements seems to show up concerning the effect of neighbouring bunches. (author)

Injection space charge: enlargements of flux density functioning point choice

International Nuclear Information System (INIS)

Ropert, A.

In Saturne, injection consists of a synchrobetatron filling of the chamber, with the goal of providing a beam with the following characteristics circulating in the machine: horizontal flux density 90 πmm mrd, vertical flux density 210 πmm mrd, dispersion in moments +- 7 x 10 -3 , and number of particles 2 x 10 12 . The determination of the principal injection parameters was made by means of GOC calculation programs. The goal of this study is to show a certain number of phenomena induced by the forces due to space charge and left suspended up to this point: variations in the intensity injectable into the machine extension of the beam occupation zone in the ν/sub x'/ ν/sub z/ diagram, and turn-turn interactions. The effects of the space charge lead to a deterioration of the injected beam for certain functioning points leading to the selection of a zone in the ν/sub x'/ ν/sub z/ diagram that is particularly suitable for beam injection

Installation and Characterization of Charged Particle Sources for Space Environmental Effects Testing

Science.gov (United States)

Skevington, Jennifer L.

2010-01-01

Charged particle sources are integral devices used by Marshall Space Flight Center s Environmental Effects Branch (EM50) in order to simulate space environments for accurate testing of materials and systems. By using these sources inside custom vacuum systems, materials can be tested to determine charging and discharging properties as well as resistance to sputter damage. This knowledge can enable scientists and engineers to choose proper materials that will not fail in harsh space environments. This paper combines the steps utilized to build a low energy electron gun (The "Skevington 3000") as well as the methods used to characterize the output of both the Skevington 3000 and a manufactured Xenon ion source. Such characterizations include beam flux, beam uniformity, and beam energy. Both sources were deemed suitable for simulating environments in future testing.

Improvement of the Longitudinal Beam Dynamics Tuning Procedure for the MSU RIA Driver Linac

CERN Document Server

Doleans, Marc; Grimm, Terry L; Marti, Felix; Wu, Xiaoyu; York, Richard

2005-01-01

The Rare Isotope Accelerator (RIA) driver linac will use a superconducting, cw linac with independently phased superconducting radio frequency cavities for acceleration and, for the heavier ions, utilize beams of multiple-charge-states (multi-q). Given the acceleration of multi-q beams and a stringent beam loss requirement in the RIA driver linac, a new beam envelope code capable of simulating nonlinearities of the multi-q beam envelopes in the longitudinal phase space was developed. Using optimization routines, the code is able to maximize the linearity of the longitudinal phase space motion and thereby minimizing beam loss by finding values for the amplitude and phase of the cavities for a given accelerating lattice. Relative motion of the multi-q beams is also taken into account so that superposition of the beam centroids and matching of their Twiss parameters are automatically controlled. As a result, the linac tuning procedure has been simplified and the longitudinal lattice performance has been improved...

Emittance growth caused by nonuniform charge distribution of bunched beam in linac

International Nuclear Information System (INIS)

Chen Yinbao; Zhang Zhenhai

1993-09-01

The nonlinear space charge effect of bunched beam in linac is one of the important reasons that induces the emittance growth because of the conversion of the field energy to kinetic energy. The authors have worked out the internal field energies associated with some nonuniform space change distributions of a bunched beam, such as Gaussian distribution, waterbag distribution and parabolic distribution. And the emittance growths caused by these nonuniformities are obtained

Aberrations due to solenoid focusing of a multiply charged high-current ion beam

CERN Document Server

Grégoire, G; Lisi, N; Schnuriger, J C; Scrivens, R; Tambini, J

2000-01-01

At the output of a laser ion source, a high current of highly charged ions with a large range of charge states is available. The focusing of such a beam by magnetic elements causes a nonlinear space-charge field to develop which can induce large aberrations and emittance growth in the beam. Simulation of the beam from the CERN laser ion source will be presented for an ideal magnetic and electrostatic system using a radially symmetric model. In addition, the three dimensional software KOBRA3 is used for the simulation of the solenoid line. The results of these simulations will be compared with experiments performed on the CERN laser ion source with solenoids (resulting in a hollow beam) and a series of gridded electrostatic lenses. (5 refs).

Electromagnetic excitation of a generic cavity with a variable e-beam pulse

International Nuclear Information System (INIS)

Fleetwood, R.; Kerris, K.; Merkel, G.; Roberts, H.; Smith, M.

1987-01-01

Relativistic electron-beam nose-erosion techniques have been employed to produce an electron beam with variable pulse shape and bremsstrahlung capability (''dial a pulse''). This capability has been employed to excite a large number of electromagnetic fields inside a canonical cavity. Electron-beam and bremsstrahlung pulse-shape parameters have been varied to produce changes in the electromagnetic cavity response. For example, generic cavity test parameters such as displacement currents or conduction currents can be emphasized or de-emphasized. A theoretical interpretation of these electromagnetic excitations is presented

Nonlinear Charge and Current Neutralization of an Ion Beam Pulse in a Pre-formed Plasma

International Nuclear Information System (INIS)

Kaganovich, Igor D.; Shvets, Gennady; Startsev, Edward; Davidson, Ronald C.

2001-01-01

The propagation of a high-current finite-length ion beam in a cold pre-formed plasma is investigated. The outcome of the calculation is the quantitative prediction of the degree of charge and current neutralization of the ion beam pulse by the background plasma. The electric magnetic fields generated by the ion beam are studied analytically for the nonlinear case where the plasma density is comparable in size with the beam density. Particle-in-cell simulations and fluid calculations of current and charge neutralization have been performed for parameters relevant to heavy ion fusion assuming long, dense beams with el >> V(subscript b)/omega(subscript b), where V(subscript b) is the beam velocity and omega subscript b is the electron plasma frequency evaluated with the ion beam density. An important conclusion is that for long, nonrelativistic ion beams, charge neutralization is, for all practical purposes, complete even for very tenuous background plasmas. As a result, the self-magnetic force dominates the electric force and the beam ions are always pinched during beam propagation in a background plasma

Nonlinear Charge and Current Neutralization of an Ion Beam Pulse in a Pre-formed Plasma

Energy Technology Data Exchange (ETDEWEB)

Igor D. Kaganovich; Gennady Shvets; Edward Startsev; Ronald C. Davidson

2001-01-30

The propagation of a high-current finite-length ion beam in a cold pre-formed plasma is investigated. The outcome of the calculation is the quantitative prediction of the degree of charge and current neutralization of the ion beam pulse by the background plasma. The electric magnetic fields generated by the ion beam are studied analytically for the nonlinear case where the plasma density is comparable in size with the beam density. Particle-in-cell simulations and fluid calculations of current and charge neutralization have been performed for parameters relevant to heavy ion fusion assuming long, dense beams with el >> V(subscript b)/omega(subscript b), where V(subscript b) is the beam velocity and omega subscript b is the electron plasma frequency evaluated with the ion beam density. An important conclusion is that for long, nonrelativistic ion beams, charge neutralization is, for all practical purposes, complete even for very tenuous background plasmas. As a result, the self-magnetic force dominates the electric force and the beam ions are always pinched during beam propagation in a background plasma.

Structure resonances due to space charge in periodic focusing channels

Science.gov (United States)

Li, Chao; Jameson, R. A.

2018-02-01

The Vlasov-Poisson model is one of the most effective methods to study the space charge dominated beam evolution self-consistently in a periodic focusing channel. Since the approach to get the solution with this model is not trivial, previous studies are limited in degenerated conditions, either in smoothed channel (constant focusing) [I. Hofmann, Phys. Rev. E 57, 4713 (1998)] or in alternating gradient focusing channel with equal initial beam emittance condition in the degrees of freedom [I. Hofmann et al., Part. Accel. 13, 145 (1983); Chao Li et al., THOBA02, IPAC2016]. To establish a basis, we intentionally limit this article to the study of the pure transverse periodic focusing lattice with arbitrary initial beam condition, and the same lattice structure in both degrees of freedom, but with possibility of different focusing strengths. This will show the extension of the existing work. The full Hamiltonian is invoked for a pure transverse focusing lattice in various initial beam conditions, revealing different mode structure and additional modes beyond those of the degenerated cases. Application of the extended method to realistic lattices (including longitudinal accelerating elements) and further details will then reveal many new insights, and will be presented in later work.

Numerical investigation of space charge electric field for a sheet ...

Indian Academy of Sciences (India)

One of the problems in scaling high power vacuum and plasma microwave sources to higher frequencies is the need to transport beams with higher space charge density, since the radio frequency circuit transverse dimensions tend to decrease with wavelength. The use of sheet electron beams can alleviate this difficulty ...

On Start to End Simulation and Modeling Issues of the Megawatt Proton Beam Facility at PSI

CERN Document Server

Adelmann, Andreas; Fitze, Hansruedi; Geus, Roman; Humbel, Martin; Stingelin, Lukas

2005-01-01

At the Paul Scherrer Institut (PSI) we routinely extract a one megawatt (CW) proton beam out of our 590 MeV Ring Cyclotron. In the frame of the ongoing upgrade program, large scale simulations have been undertaken in order to provide a sound basis to assess the behaviour of very intense beams in cyclotrons. The challenges and attempts towards massive parallel three dimensional start-to- end simulations will be discussed. The used state of the art numerical tools (mapping techniques, time integration, parallel FFT and finite element based multigrid Poisson solver) and their parallel implementation will be discussed. Results will be presented in the area of: space charge dominated beam transport including neighbouring turns, eigenmode analysis to obtain accurate electromagnetic fields in large the rf cavities and higher order mode interaction between the electromagnetic fields and the particle beam. For the problems investigated so far a good agreement between theory i.e. calculations and measurements is obtain...

Plural three-wave resonances of space charge wave harmonics in transit section of klystron-type two-stream FEL with helical electron beam

DEFF Research Database (Denmark)

Lysenko, Alexander; Volk, Iurii; Serozhko, Anastasia

2017-01-01

We have carried out the research of plural three-wave resonances of space charge wave (SCW) harmonics in the transit section of the klystron type two-stream superheterodyne free-electron laser (TSFEL) with helical electron beam in cubic non-linear approximation. We have found out that two...

Halo and space charge issues in the SNS Ring

International Nuclear Information System (INIS)

Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.

2000-01-01

The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring

Halo and space charge issues in the SNS Ring

Energy Technology Data Exchange (ETDEWEB)

Fedotov, A.V.; Abell, D.T.; Beebe-Wang, J.; Lee, Y.Y.; Malitsky, N.; Wei, J.; Gluckstern, R.L.

2000-06-30

The latest designs for high-intensity proton rings require minimizing beam-induced radioactivation of the vacuum chamber. Although the tune depression in the ring is much smaller than in high-intensity linacs, space-charge contributions to halo formation and, hence, beam loss may be significant. This paper reviews our current understanding of halo formation issues for the Spallation Neutron Source (SNS) accumulator ring.

Analysis of a high brightness photo electron beam with self field and wake field effects

International Nuclear Information System (INIS)

Parsa, Z.

1991-01-01

High brightness sources are the basic ingredients in the new accelerator developments such as Free-Electron Laser experiments. The effects of the interactions between the highly charged particles and the fields in the accelerating structure, e.g. R.F., Space charge and Wake fields can be detrimental to the beam and the experiments. We present and discuss the formulation used, some simulation and results for the Brookhaven National Laboratory high brightness beam that illustrates effects of the accelerating field, space charge forces (e.g. due to self field of the bunch), and the wake field (e.g. arising from the interaction of the cavity surface and the self field of the bunch)

Measurement of beam phase at FLASH using HOMs in accelerating cavities

CERN Document Server

Shi, Lianliang; Jones, Roger M; Joshi, Nirav

2017-01-01

The beam phase relative to the accelerating field is of vital importance for the quality of photon beams produced in modern Free Electron Lasers based on superconducting cavities. Normally, the phase is determined by detecting the transient field induced by the beam. In this way the phase of each cavity is checked and adjusted typically every few months. In this paper, we present an on-line method of beam phase determination, based on higher order modes (HOMs) excited in the 2nd monopole band by the beam inside these cavities. A circuit model of this HOM band is also presented. Various effects on the resolution have been studied. The results indicate that the resolution is strongly dependent on the signal to noise ratio and the sampling rate. Preliminary experimental results, based on a broadband setup, reveal a resolution of ca. 0.1° RMS. These are in good agreement with simulation results. The work will pave the way for a dedicated system of beam phase monitoring, which is under development for the Europea...

Simulation of the plasma meniscus with and without space charge using triode extraction system

International Nuclear Information System (INIS)

Rahman, M.M.Abdel; El-Khabeary, H.

2009-01-01

In this work, simulation of the singly charged argon ion trajectories for a variable plasma meniscus is studied with and without space charge for the triode extraction system by using SIMION 3D (Simulation of Ion Optics in Three Dimensions) version 7 personal computer program. The influence of acceleration voltage applied to the acceleration electrode of the triode extraction system on the shape of the plasma meniscus has been determined. The plasma electrode is set at +5000 volt and the acceleration voltage applied to the acceleration electrode is varied from -5000 volt to +5000 volt. In the most of the concave and convex plasma shapes, ion beam emittance can be calculated by using separate standard deviations of positions and elevations angles. Ion beam emittance as a function of the curvature of the plasma meniscus for different plasma shapes ( flat, concave and convex ) without space charge at acceleration voltage varied from -5000 volt to +5000 volt applied to the acceleration electrode of the triode extraction system has been investigated. The influence of the extraction gap on ion beam emittance for a plasma concave shape of 3.75 mm without space charge at acceleration voltage, V acc = -2000 volt applied to the acceleration electrode of the triode extraction system has been determined. Also the influence of space charge on ion beam emittance for variable plasma meniscus at acceleration voltage, V acc = -2000 volt applied to the acceleration electrode of the triode extraction system has been studied. (author)

Tunable cavity resonator including a plurality of MEMS beams

Science.gov (United States)

Peroulis, Dimitrios; Fruehling, Adam; Small, Joshua Azariah; Liu, Xiaoguang; Irshad, Wasim; Arif, Muhammad Shoaib

2015-10-20

A tunable cavity resonator includes a substrate, a cap structure, and a tuning assembly. The cap structure extends from the substrate, and at least one of the substrate and the cap structure defines a resonator cavity. The tuning assembly is positioned at least partially within the resonator cavity. The tuning assembly includes a plurality of fixed-fixed MEMS beams configured for controllable movement relative to the substrate between an activated position and a deactivated position in order to tune a resonant frequency of the tunable cavity resonator.

High-flux cold rubidium atomic beam for strongly-coupled cavity QED

Energy Technology Data Exchange (ETDEWEB)

Roy, Basudev [Indian Institute of Science Education and Research, Kolkata (India); University of Maryland, MD (United States); Scholten, Michael [University of Maryland, MD (United States)

2012-08-15

This paper presents a setup capable of producing a high-flux continuous beam of cold rubidium atoms for cavity quantum electrodynamics experiments in the region of strong coupling. A 2D{sup +} magneto-optical trap (MOT), loaded with rubidium getters in a dry-film-coated vapor cell, fed a secondary moving-molasses MOT (MM-MOT) at a rate greater than 2 x 10{sup 10} atoms/s. The MM-MOT provided a continuous beam with a tunable velocity. This beam was then directed through the waist of a cavity with a length of 280 μm, resulting in a vacuum Rabi splitting of more than ±10 MHz. The presence of a sufficient number of atoms in the cavity mode also enabled splitting in the polarization perpendicular to the input. The cavity was in the strong coupling region, with an atom-photon dipole coupling coefficient g of 7 MHz, a cavity mode decay rate κ of 3 MHz, and a spontaneous emission decay rate γ of 6 MHz.

Beam orbit control in TESLA superconducting cavities from dipole mode measurements

International Nuclear Information System (INIS)

Paparella, R.

2006-09-01

The knowledge of the electromagnetic interaction between a beam and the surrounding vacuum chamber is necessary in order to optimize the accelerator performance in terms of stored current. Many instability phenomena may occur in the machine because of the fields produced by the beam and acting back on itself. Basically, these fields, wake-fields, produce an extra voltage, affecting the longitudinal dynamics, and a transverse kick which deflects the beam. In this thesis we present the results of theoretical and experimental investigations to demonstrate the possibility of using the dipolar wake fields of the superconducting accelerating to measure the beam transverse position. After an introduction to the ILC project and to the TESLA technology, of superconducting RF cavities, we will approach the problem from an analytical point of view in chapter 2. The expression of the wake fields in a cylindrical cavity will be investigated and the electromagnetic field modes derived from Maxwell equations in an original way. Graphical solutions of a Matlab program simulating the fields due to a particle passing through a pill-box cavity along a generic path will be shown. The interaction of the beam with higher order modes (HOM) in the TESLA cavities has been studied in the past at the TESLA Test Facility (TTF) in order to determine whether the modes with the highest loss factor are sufficiently damped. Starting from the results obtained before 2003, HOM signals has been better observed and examined in order to use dipole modes to find the electric center of each cavity in the first TTF accelerating module. The results presented in chapter 3 will show that by monitoring the HOM signal amplitude for two polarizations of a dipole mode, one can measure electrical center of the modes with a resolution of 50 μm. Moreover, a misalignment of the first TTF module with respect to the gun axis has been predicted using cavity dipole modes. Alternatives to this method are described in

Laboratory Experiments Enabling Electron Beam use in Tenuous Space Plasmas

Science.gov (United States)

Miars, G.; Leon, O.; Gilchrist, B. E.; Delzanno, G. L.; Castello, F. L.; Borovsky, J.

2017-12-01

A mission concept is under development which involves firing a spacecraft-mounted electron beam from Earth's magnetosphere to connect distant magnetic field lines in real time. To prevent excessive spacecraft charging and consequent beam return, the spacecraft must be neutralized in the tenuous plasma environment of the magnetosphere. Particle-In-Cell (PIC) simulations suggest neutralization can be accomplished by emitting a neutral plasma with the electron beam. Interpretation of these simulations also led to an ion emission model in which ion current is emitted from a quasi-neutral plasma as defined by the space charge limit [1,2]. Experiments were performed at the University of Michigan's Plasmadynamics and Electric Propulsion Laboratory (PEPL) to help validate the ion emission model. A hollow cathode plasma contactor was used as a representative spacecraft and charged with respect to the chamber walls to examine the effect of spacecraft charging on ion emission. Retarding Potential Analyzer (RPA) measurements were performed to understand ion flow velocity as this parameter relates directly to the expected space charge limit. Planar probe measurements were also made to identify where ion emission primarily occurred and to determine emission current density levels. Evidence of collisions within the plasma (particularly charge exchange collisions) and a simple model predicting emitted ion velocities are presented. While a detailed validation of the ion emission model and of the simulation tools used in [1,2] is ongoing, these measurements add to the physical understanding of ion emission as it may occur in the magnetosphere. 1. G.L. Delzanno, J.E. Borovsky, M.F. Thomsen, J.D. Moulton, and E.A. MacDonald, J. Geophys. Res. Space Physics 120, 3647, 2015. 2. G.L. Delzanno, J.E. Borovsky, M.F. Thomsen, and J.D. Moulton, J. Geophys. Res. Space Physics 120, 3588, 2015. ________________________________ * This work is supported by Los Alamos National Laboratory.

Electron beams and applications

International Nuclear Information System (INIS)

Haouat, G.; Couillaud, C.

1998-01-01

Studies of the physical properties of the ELSA-linac electron beam are presented. They include measurements of the characteristic beam parameter and analyzes of the beam transport using simulation codes. The aim of these studies is to determine the best conditions for production of intense and very short electron bunches and to optimize the transport of space-charge dominated beams. Precise knowledge of the transport dynamics allows to produce beams with the required characteristics for light production in Free-Electron Laser (FEL), and to give a good description of energy-transfer phenomena between electrons and photons in the wriggler. The particular features of ELSA authorize studies of high-intensity, high-brightness beam properties, especially the halo surrounding the dense core of the electron bunches, which is formed by the space charge effects. It is also shown that the ELSA facility is well suited for the fabrication of very short γ and X-rays sources for applied research in nuclear and plasma physics, or for time response studies of fast detectors. (author)

Composite optical vortices in noncollinear Laguerre–Gaussian beams and their propagation in free space

International Nuclear Information System (INIS)

Chen Ke; Liu Pusheng; Lü Baida

2008-01-01

Taking two Laguerre—Gaussian beams with topological charge l = ± 1 as an example, this paper studies the composite optical vortices formed by two noncollinear Laguerre—Gaussian beams with different phases, amplitudes, waist widths, off-axis distances, and their propagation in free space. It is shown by detailed numerical illustrative examples that the number and location of composite vortices at the waist plane are variable by varying the relative phase β, amplitude ratio η, waist width ratio ζ, or off-axis distance ratio μ. The net topological charge l net is not always equal to the sum l sum of charges of the two component beams. The motion, creation and annihilation of composite vortices take place in the free-space propagation, and the net charge during the propagation remains unchanged and equals to the net charge at the waist plane

Electron-beam direct drive for rf accelerator cavities

International Nuclear Information System (INIS)

Nahemow, M.D.; Humphries, S. Jr.

1987-01-01

This paper describes a Program to Demonstrate Electron-Beam Direct Drive for Radio Frequency (RF) Linear Accelerators at the Westinghouse R and D Center. The experimental program was undertaken using an existing electron beam facility at the Westinghouse R and C Center to demonstrate the potential of the Direct Drive RF Cavities for High Power Beams concept discussed as part of a program to develop a viable alternate concept for driving RF linear accelerators

A feasibility study of space-charge neutralized ion induction linacs: Final report

International Nuclear Information System (INIS)

Slutz, S.A.; Primm, P.; Renk, T.; Johnson, D.J.

1997-03-01

Applications for high current (> 1 kA) ion beams are increasing. They include hardening of material surfaces, transmutation of radioactive waste, cancer treatment, and possibly driving fusion reactions to create energy. The space-charge of ions limits the current that can be accelerated in a conventional ion linear accelerator (linac). Furthermore, the accelerating electric field must be kept low enough to avoid the generation and acceleration of counter-streaming electrons. These limitations have resulted in ion accelerator designs that employ long beam lines and would be expensive to build. Space-charge neutralization and magnetic insulation of the acceleration gaps could substantially reduce these two limitations, but at the expense of increasing the complexity of the beam physics. We present theory and experiments to determine the degree of charge-neutralization that can be achieved in various environments found in ion accelerators. Our results suggest that, for high current applications, space-charge neutralization could be used to improve on the conventional ion accelerator technology. There are two basic magnetic field geometries that can be used to insulate the accelerating gaps, a radial field or a cusp field. We will present studies related to both of these geometries. We shall also present numerical simulations of open-quotes multicuspclose quotes accelerator that would deliver potassium ions at 400 MeV with a total beam power of approximately 40 TW. Such an accelerator could be used to drive fusion

Simulation of a cascaded longitudinal space charge amplifier for coherent radiation generation

Energy Technology Data Exchange (ETDEWEB)

Halavanau, A., E-mail: aliaksei.halavanau@gmail.com [Department of Physics and Northern Illinois, Center for Accelerator & Detector Development, Northern Illinois University, DeKalb, IL 60115 (United States); Accelerator Physics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Piot, P. [Department of Physics and Northern Illinois, Center for Accelerator & Detector Development, Northern Illinois University, DeKalb, IL 60115 (United States); Accelerator Physics Center, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)

2016-05-21

Longitudinal space charge (LSC) effects are generally considered as harmful in free-electron lasers as they can seed unfavorable energy modulations that can result in density modulations with associated emittance dilution. This “micro-bunching instabilities” is naturally broadband and could possibly support the generation of coherent radiation over a broad region of the spectrum. Therefore there has been an increasing interest in devising accelerator beam lines capable of controlling LSC induced density modulations. In the present paper we refine these previous investigations by combining a grid-less space charge algorithm with the popular particle-tracking program ELEGANT. This high-fidelity model of the space charge is used to benchmark conventional LSC models. We finally employ the developed model to investigate the performance of a cascaded LSC amplifier using beam parameters comparable to the ones achievable at Fermilab Accelerator Science & Technology (FAST) facility currently under commissioning at Fermilab.

Three-dimensional space charge calculation method

International Nuclear Information System (INIS)

Lysenko, W.P.; Wadlinger, E.A.

1981-01-01

A method is presented for calculating space-charge forces suitable for use in a particle tracing code. Poisson's equation is solved in three dimensions with boundary conditions specified on an arbitrary surface by using a weighted residual method. Using a discrete particle distribution as our source input, examples are shown of off-axis, bunched beams of noncircular crosssection in radio-frequency quadrupole (RFQ) and drift-tube linac geometries

Design Considerations of a Novel Two-Beam Accelerator

Science.gov (United States)

Luginsland, John William

This thesis reports the design study of a new type of charged particle accelerator called the Twobetron. The accelerator consists of two beams of electrons traveling through a series of pillbox cavities. The power of a high current annular beam excites an electromagnetic mode in the cavities, which, in turn, drives a low current on-axis pencil beam to high energy. We focus on the design considerations that would make use of existing pulsed power systems, for a proof-of-principle experiment. Potential applications of this new device include radiotherapy, materials processing, and high energy accelerators. The first phase of the research involves analytic description of the accelerating process. This reveals the problem of phase slippage. Derbenev's proposed cure of beam radius modulation is analyzed. Further studies include the effect of initial phase and secondary beam loading. Scaling laws to characterize the Twobetron's performance are derived. Computer simulation is performed to produce a self-consistent analysis of the dynamics of the space charge and its interaction with the accelerator structure. Particle -in-cell simulations answer several questions concerning beam stability, cavity modes, and the nature of the structure. Specifically, current modulation on the primary beam is preserved in the simulations. However, these simulations also revealed that mode competition and significant cavity coupling are serious issues that need to be addressed. Also considered is non-axisymmetric instability on the driver beam of the Twobetron, in particular, the beam breakup instability (BBU), which is known to pose a serious threat to linear accelerators in general. We extend the classical analysis of BBU to annular beams. The effect of higher order non-axisymmetric modes is also examined. It is shown that annular beams are more stable than pencil beams to BBU in general. Our analysis also reveals that the rf magnetic field is more important than the rf electric field in

A self-consistent nonlinear theory of resistive-wall instability in a relativistic electron beam

International Nuclear Information System (INIS)

Uhm, H.S.

1994-01-01

A self-consistent nonlinear theory of resistive-wall instability is developed for a relativistic electron beam propagating through a grounded cylindrical resistive tube. The theory is based on the assumption that the frequency of the resistive-wall instability is lower than the cutoff frequency of the waveguide. The theory is concentrated on study of the beam current modulation directly related to the resistive-wall klystron, in which a relativistic electron beam is modulated at the first cavity and propagates downstream through the resistive wall. Because of the self-excitation of the space charge waves by the resistive-wall instability, a highly nonlinear current modulation of the electron beam is accomplished as the beam propagates downstream. A partial integrodifferential equation is obtained in terms of the initial energy modulation (ε), the self-field effects (h), and the resistive-wall effects (κ). Analytically investigating the partial integrodifferential equation, a scaling law of the propagation distance z m at which the maximum current modulation occurs is obtained. It is found in general that the self-field effects dominate over the resistive-wall effects at the beginning of the propagation. As the beam propagates farther downstream, the resistive-wall effects dominate. Because of a relatively large growth rate of the instability, the required tube length of the klystron is short for most applications

Sub-micron resolution rf cavity beam position monitor system at the SACLA XFEL facility

Science.gov (United States)

Maesaka, H.; Ego, H.; Inoue, S.; Matsubara, S.; Ohshima, T.; Shintake, T.; Otake, Y.

2012-12-01

We have developed and constructed a C-band (4.760 GHz) rf cavity beam position monitor (RF-BPM) system for the XFEL facility at SPring-8, SACLA. The demanded position resolution of the RF-BPM is less than 1 μm, because an electron beam and x-rays must be overlapped within 4 μm precision in the undulator section for sufficient FEL interaction between the electrons and x-rays. In total, 57 RF-BPMs, including IQ demodulators and high-speed waveform digitizers for signal processing, were produced and installed into SACLA. We evaluated the position resolutions of 20 RF-BPMs in the undulator section by using a 7 GeV electron beam having a 0.1 nC bunch charge. The position resolution was measured to be less than 0.6 μm, which was sufficient for the XFEL lasing in the wavelength region of 0.1 nm, or shorter.

Development of an S-band cavity Beam Position Monitor for ATF2

Science.gov (United States)

Heo, A.; Kim, E.-S.; Kim, H.; Son, D.; Honda, Y.; Tauchi, T.

2013-04-01

We have developed an S-band cavity Beam Position Monitor (BPM) in order to measure the position of an electron beam in the final focus area at ATF2, which is the test facility for the final focus design for the International Linear Collider (ILC). The lattice of the ILC Beam Delivery System (BDS) has been modified, requiring a larger physical aperture of 40 mm in the final focus area. The beam orbit measurement in this area is now covered with high resolution S-Band cavity BPMs. In this paper we summarize the design of the cavity BPM and the first experimental results. The calibration slopes were measured as 0.87 counts/μm in the x-coordinate direction and 1.16 counts/μm in the y-coordinate direction.

Telescope-based cavity for negative ion beam neutralization in future fusion reactors.

Science.gov (United States)

Fiorucci, Donatella; Hreibi, Ali; Chaibi, Walid

2018-03-01

In future fusion reactors, heating system efficiency is of the utmost importance. Photo-neutralization substantially increases the neutral beam injector (NBI) efficiency with respect to the foreseen system in the International Thermonuclear Experimental Reactor (ITER) based on a gaseous target. In this paper, we propose a telescope-based configuration to be used in the NBI photo-neutralizer cavity of the demonstration power plant (DEMO) project. This configuration greatly reduces the total length of the cavity, which likely solves overcrowding issues in a fusion reactor environment. Brought to a tabletop experiment, this cavity configuration is tested: a 4 mm beam width is obtained within a ≃1.5  m length cavity. The equivalent cavity g factor is measured to be 0.038(3), thus confirming the cavity stability.

Charge breeding of intense radioactive beams

CERN Document Server

Kester, O

2001-01-01

The efficient transformation of radioactive beams by charge breeding devices will critically influence the lay-out of the post accelerator of presently built first generation radioactive ion beam (RIB) facilities as well as new second generation facilities. The size of the post-accelerator needed to bring the unstable nuclei to the energies required to study nuclear reactions depends on the charge state of the radioactive ions. The capability to raise that charge state from 1+ to n+, where n may correspond to a charge-to- mass ratio of 0.15 or higher, will therefore produce an enormous reduction in cost as well as the possibility to accelerate heavier masses. Thus the efficiency of the charge breeding scheme in comparison to the stripping scheme will be explored in the frame of the EU-network charge breeding. The two possible charge breeding schemes using either an Electron Beam Ion Source (EBIS) or an Electron Cyclotron Resonance Ion Source (ECRIS), the demands to the sources and the present status of existi...

Refined Calculation of Beam Dynamics During UMER Injection

CERN Document Server

Bai, Gang; Godlove, Terry; Haber, Irving; Kishek, Rami A; Quinn, Bryan; Reiser, Martin; Thangaraj, Jayakar C T; Walter, Mark

2005-01-01

The University of Maryland Electron Ring (UMER) is built as a low-cost testbed for intense beam physics for benefit of larger ion accelerators. The beam intensity is designed to be variable, spanning the entire range from low current operation to highly space-charge-dominated transport. The ring has recently been closed and multi-turn commissioning has begun. Although we have conducted many experiments at high space charge during UMER construction, lower-current beams have become quite useful in this commissioning stage for assisting us with beam steering, measurement of phase advance, etc. One of the biggest challenges of multi-turn operation of UMER is correctly operating the Y-shaped injection section, hence called the Y-section, which is specially designed for UMER multi-turn operation. It is a challenge because the system requires several quadrupoles and dipoles in a very stringent space, resulting in mechanical, electrical, and beam control complexities. This paper presents a simulation study of the bea...

Non-destructive splitter of twisted light based on modes splitting in a ring cavity.

Science.gov (United States)

Li, Yan; Zhou, Zhi-Yuan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can

2016-02-08

Efficiently discriminating beams carrying different orbital angular momentum (OAM) is of fundamental importance for various applications including high capacity optical communication and quantum information processing. We design and experimentally verify a distinguished method for effectively splitting different OAM-carried beams by introducing Dove prisms in a ring cavity. Because of rotational symmetry broken of two OAM-carried beams with opposite topological charges, their transmission spectra will split. When mode and impedance matches between the cavity and one OAM-carried beam are achieved, this beam will transmit through the cavity and other beam will be reflected, both beams keep their spatial shapes. In this case, the cavity acts like a polarized beam splitter. Besides, the transmitting beam can be selected at your will, the splitting efficiency can reach unity if the cavity is lossless and it completely matches the beam. Furthermore, beams carry multi-OAMs can also be split by cascading ring cavities.

Space charge models and PATH

International Nuclear Information System (INIS)

Wald, H.B.

1990-01-01

The 'PATH' codes are used to design magnetic optics subsystems for neutral particle beam systems. They include a 2-1/2D and three 3-D space charge models, two of which have recently been added. This paper describes the 3-D models and reports on preliminary benchmark studies in which these models are checked for stability as the cloud size is varied and for consistency with each other. Differences between the models are investigated and the computer time requirements for running these models are established

Simulation of the Plasma Meniscus with and without Space Charge using Triode Extraction System

International Nuclear Information System (INIS)

Abdel Rahman, M.M.; EI-Khabeary, H.

2007-01-01

In this work simulation of the singly charged argon ion trajectories for a variable plasma meniscus is studied with and without space charge for the triode extraction system by using SIMION 3D (Simulation of Ion Optics in Three Dimensions) version 7 personal computer program. Tbe influence of acceleration voltage applied to tbe acceleration electrode of the triode extraction system on the shape of the plasma meniscus has been determined. The plasma electrode is set at +5000 volt and the acceleration voltage applied to the acceleration electrode is varied from -5000 volt to +5000 volt. In the most of the concave and convex plasma shapes ion beam emittance can be calculated by using separate standard deviations of positions and elevations angles. Ion beam emittance as a function of the curvature of the plasma meniscus for different plasma shapes ( flat concave and convex ) without space change at acceleration voltage varied from -5000 volt to +5000 volt applied to the acceleration electrode of the triode extraction system has been investigated. Tbe influence of the extraction gap on ion beam emittance for a plasma concave shape of 3.75 mm without space charge at acceleration voltage, V a cc = -2000 volt applied to the acceleration electrode of the triode extraction system has been determined. Also the influence of space charge on ion beam emittance for variable plasma meniscus at acceleration voltage, V a cc = - 2000 volt applied to the acceleration electrode of. the triode extraction system has been studied

Beam dynamic simulations of the CLIC crab cavity and implications on the BDS

Energy Technology Data Exchange (ETDEWEB)

Shinton, I.R.R., E-mail: ian.shinton@stfc.ac.uk [School of Physics and Astronomy, University of Manchester, Manchester (United Kingdom); Cockcroft Institute of Accelerator Science and Technology, Daresbury (United Kingdom); Burt, G. [Engineering Department, Lancaster University, Lancaster (United Kingdom); Cockcroft Institute of Accelerator Science and Technology, Daresbury (United Kingdom); Glasman, C.J.; Jones, R.M. [School of Physics and Astronomy, University of Manchester, Manchester (United Kingdom); Cockcroft Institute of Accelerator Science and Technology, Daresbury (United Kingdom); Wolski, A. [Department of Physics, University of Liverpool, Liverpool (United Kingdom); Cockcroft Institute of Accelerator Science and Technology, Daresbury (United Kingdom)

2011-11-21

The Compact Linear Collider (CLIC) is a proposed electron positron linear collider design aiming to achieve a centre of mass energy of up to 3 TeV. The main accelerating structures in CLIC operate at an X-band frequency of 11.994 GHz with an accelerating gradient of 100 MV/m. The present design requires the beams to collide at a small crossing angle of 10 mrad per line giving a resultant overall crossing angle of 20 mrad. Transverse deflecting cavities, referred to as 'Crab cavities', are installed in the beam delivery system (BDS) of linear collider designs in order to ensure the final luminosity at the interaction point (IP) is comparable to that in a head on collision. We utilise the beam tracking code PLACET combined with the beam-beam code GUINEA-PIG to calculate the resulting luminosity at the IP. We follow a similar tuning procedure to that used for the design of the ILC crab cavities and anitcrab cavities. However an unexpected loss in luminosity of 10% was observed for the 20 mrad design was observed. It was discovered that the action of the crab cavities can affect the geometric aberrations resulting from the sextupoles used to correct chromatic effects in the beam delivery system. This has direct consequences regarding the design of the present CLIC BDS.

Nonlinear delta f Simulations of Collective Effects in Intense Charged Particle Beams

CERN Document Server

Hong Qi

2003-01-01

A nonlinear delta(f) particle simulation method based on the Vlasov-Maxwell equations has been recently developed to study collective processes in high-intensity beams, where space-charge and magnetic self-field effects play a critical role in determining the nonlinear beam dynamics. Implemented in the Beam Equilibrium, Stability and Transport (BEST) code [H. Qin, R.C. Davidson, and W.W. Lee, Physical Review -- Special Topics on Accelerator and Beams 3 (2000) 084401; 3 (2000) 109901.], the nonlinear delta(f) method provides a low-noise and self-consistent tool for simulating collective interactions and nonlinear dynamics of high-intensity beams in modern and next-generation accelerators and storage rings, such as the Spallation Neutron Source and heavy ion fusion drivers. A wide range of linear eigenmodes of high-intensity charged-particle beams can be systematically studied using the BEST code. Simulation results for the electron-proton two-stream instability in the Proton Storage Ring experiment [R. Macek, ...

Transverse Space-Charge Field-Induced Plasma Dynamics for Ultraintense Electron-Beam Characterization

Directory of Open Access Journals (Sweden)

R. Tarkeshian

2018-05-01

Full Text Available Similarly to laser or x-ray beams, the interaction of sufficiently intense particle beams with neutral gases will result in the creation of plasma. In contrast to photon-based ionization, the strong unipolar field of a particle beam can generate a plasma where the electron population receives a large initial momentum kick and escapes, leaving behind unshielded ions. Measuring the properties of the ensuing Coulomb exploding ions—such as their kinetic energy distribution, yield, and spatial distribution—can provide information about the peak electric fields that are achieved in the electron beams. Particle-in-cell simulations and analytical models are presented for high-brightness electron beams of a few femtoseconds or even hundreds of attoseconds, and transverse beam sizes on the micron scale, as generated by today’s free electron lasers. Different density regimes for the utilization as a potential diagnostics are explored, and the fundamental differences in plasma dynamical behavior for e-beam or photon-based ionization are highlighted. By measuring the dynamics of field-induced ions for different gas and beam densities, a lower bound on the beam charge density can be obtained in a single shot and in a noninvasive way. The exponential dependency of the ionization yield on the beam properties can provide unprecedented spatial and temporal resolution, at the submicrometer and subfemtosecond scales, respectively, offering a practical and powerful approach to characterizing beams from accelerators at the frontiers of performance.

Damping of coherent oscillations in intense ion beams

International Nuclear Information System (INIS)

Karpov, Ivan

2017-01-01

Transverse decoherence of a displaced ion bunch is an important phenomenon in synchrotrons and storage rings. An offset can be caused by an injection error after the bunch-to-bucket transfer between synchrotrons or by an externally generated kick. Decoherence results in a transverse emittance blowup, which can cause particle losses and a beam quality degradation. To prevent the beam blowup, a transverse feedback system (TFS) can be used. The damping time should be shorter than the characteristic decoherence time, which can be strongly affected by the interplay of different intensity effects (e.g., space charge and impedances). This thesis describes the development of the analytical models that explain decoherence and emittance growth with chromaticity, space charge, and image charges within the first synchrotron period. The pulsed response function including intensity effects was derived from the model for beam transfer functions. For a coasting beam, the two- dimensional model shows that space charge slows down and above intensity threshold suppresses decoherence. These predictions were confirmed by particle tracking simulations with self-consistent space charge fields. Additionally, halo buildup and losses during decoherence were observed in simulations. These effects were successfully interpreted using a non self-consistent particle-core model. The two-dimensional model was extended to the bunched beams. The simulation results reproduce the analytical predictions. The intensity threshold of decoherence suppression is higher in comparison to a coasting beam, image charges can restore decoherence. In the present work dedicated experiments were performed in the SIS18 synchrotron at GSI Darmstadt and the results were compared with simulations and analytical predictions. The contribution of nonlinearities and image charges is negligible while chromaticity and space charge dominate decoherence. To study the damping efficiency of TFS, a comprehensive TFS module was

Damping of coherent oscillations in intense ion beams

Energy Technology Data Exchange (ETDEWEB)

Karpov, Ivan

2017-02-06

Transverse decoherence of a displaced ion bunch is an important phenomenon in synchrotrons and storage rings. An offset can be caused by an injection error after the bunch-to-bucket transfer between synchrotrons or by an externally generated kick. Decoherence results in a transverse emittance blowup, which can cause particle losses and a beam quality degradation. To prevent the beam blowup, a transverse feedback system (TFS) can be used. The damping time should be shorter than the characteristic decoherence time, which can be strongly affected by the interplay of different intensity effects (e.g., space charge and impedances). This thesis describes the development of the analytical models that explain decoherence and emittance growth with chromaticity, space charge, and image charges within the first synchrotron period. The pulsed response function including intensity effects was derived from the model for beam transfer functions. For a coasting beam, the two- dimensional model shows that space charge slows down and above intensity threshold suppresses decoherence. These predictions were confirmed by particle tracking simulations with self-consistent space charge fields. Additionally, halo buildup and losses during decoherence were observed in simulations. These effects were successfully interpreted using a non self-consistent particle-core model. The two-dimensional model was extended to the bunched beams. The simulation results reproduce the analytical predictions. The intensity threshold of decoherence suppression is higher in comparison to a coasting beam, image charges can restore decoherence. In the present work dedicated experiments were performed in the SIS18 synchrotron at GSI Darmstadt and the results were compared with simulations and analytical predictions. The contribution of nonlinearities and image charges is negligible while chromaticity and space charge dominate decoherence. To study the damping efficiency of TFS, a comprehensive TFS module was

MEASUREMENT OF HIGH Q RF CAVITY IMPEDANCE WITH BEAM

International Nuclear Information System (INIS)

Limborg, Cecile

2003-01-01

An inexpensive method to measure, with beam, the Rs and Q of narrow-band high order resonances in RF cavities was developed on SPEAR. The two main results of this study are: (1) an improved operational stability of SPEAR; and (2) the decision to keep the present cavities for the proposed SPEAR upgrade. SPEAR3 will be run initially at 200 mA, twice the present current. Just beyond the current threshold, and before step loss, there is a regime in which the beam performs large amplitude, low frequency oscillations. Detailed measurements were performed to characterize the frequency, amplitude, growth and damping time of these relaxation oscillations

Parametric Landau damping of space charge modes

Energy Technology Data Exchange (ETDEWEB)

Macridin, Alexandru [Fermilab; Burov, Alexey [Fermilab; Stern, Eric [Fermilab; Amundson, James [Fermilab; Spentzouris, Panagiotis [Fermilab

2016-09-23

Landau damping is the mechanism of plasma and beam stabilization; it arises through energy transfer from collective modes to the incoherent motion of resonant particles. Normally this resonance requires the resonant particle's frequency to match the collective mode frequency. We have identified an important new damping mechanism, parametric Landau damping, which is driven by the modulation of the mode-particle interaction. This opens new possibilities for stability control through manipulation of both particle and mode-particle coupling spectra. We demonstrate the existence of parametric Landau damping in a simulation of transverse coherent modes of bunched accelerator beams with space charge.

New Spectral Method for Halo Particle Definition in Intense Mis-matched Beams

Energy Technology Data Exchange (ETDEWEB)

Dorf, Mikhail A.; Davidson, Ronald C.; Startsev, Edward A.

2011-04-27

An advanced spectral analysis of a mis-matched charged particle beam propagating through a periodic focusing transport lattice is utilized in particle-in-cell (PIC) simulations. It is found that the betatron frequency distribution function of a mismatched space-charge-dominated beam has a bump-on-tail structure attributed to the beam halo particles. Based on this observation, a new spectral method for halo particle definition is proposed that provides the opportunity to carry out a quantitative analysis of halo particle production by a beam mismatch. In addition, it is shown that the spectral analysis of the mismatch relaxation process provides important insights into the emittance growth attributed to the halo formation and the core relaxation processes. Finally, the spectral method is applied to the problem of space-charge transport limits.

A novel technique for tuning of co-axial cavity of multi-beam klystron

Energy Technology Data Exchange (ETDEWEB)

Saha, Sukalyan, E-mail: sstechno18@gmail.com; Bandyopadhyay, Ayan Kumar; Pal, Debashis; Kant, Deepender; Joshi, Lalit Mohan; Kumar, Bijendra; Meena, Rakesh; Rawat, Vikram [Microwave Tubes Division, CSIR-CEERI, Pilani, Rajasthan-333031 (India)

2016-03-09

Multi-beam Klystrons (MBKs) have gained wide acceptances in the research sector for its inherent advantages. But developing a robust tuning technique for an MBK cavity of coaxial type has still remained a challenge as these designs are very prone to suffer from asymmetric field distribution with inductive tuning of the cavity. Such asymmetry leads to inhomogeneous beam-wave interaction, an undesirable phenomenon. Described herein is a new type of coaxial cavity that has the ability to suppress the asymmetry, thereby allowing tuning of the cavity with a single tuning post.

Particle acceleration and wave emissions associated with the formation of auroral cavities and enhancements

International Nuclear Information System (INIS)

Winglee, R.M.; Pritchett, P.L.; Dusenbery, P.B.

1988-01-01

Observations from DE 1 and electrostatic particle simulations are combined in an effort to provide a unified model for (nightside) auroral particle acceleration and wave emissions and their association with plasma cavities and enhancements. The observations show that enhanced electron precipitation during inverted-V events is associated with broadband electrostatic bursts (BEB), increased upward field-aligned currents, and density enhancements. These regions are flanked by return current regions where the density is depleted (i.e., by plasma cavities). Perpendicular acceleration of ambient plasma ions can occur in both upward and return current regions. It is shown through the simulations that these processes are integrally related and are not independent of each other. The free energy for the auroral particle acceleration can be provided by energetic ion beams in the plasma sheet boundary layer with nonzero perpendicular energy. The perpendicular energy allows charge separation between the beam ions and costreaming electrons to occur. The resultant space charge fields accelerate electrons on the same field lines as the costreaming electrons downward toward the ionosphere, without the beam ions actually propagating down to auroral altitudes. Ambient plasma electrons on adjacent field lines are accelerated upward, forming a return current

Plasma-induced evolution behavior of space-charge-limited current for multiple-needle cathodes

International Nuclear Information System (INIS)

Li Limin; Liu Lie; Zhang Jun; Wen Jianchun; Liu Yonggui; Wan Hong

2009-01-01

Properties of the plasma and beam flow produced by tufted carbon fiber cathodes in a diode powered by a ∼500 kV, ∼400 ns pulse are investigated. Under electric fields of 230-260 kV cm -1 , the electron current density was in the range 210-280 A cm -2 , and particularly at the diode gap of 20 mm, a maximum beam power density of about 120 MW cm -2 was obtained. It was found that space-charge-limited current exhibited an evolution behavior as the accelerating pulse proceeded. There exists a direct relation between the movement of plasma within the diode and the evolution of space-charge-limited current. Initially in the accelerating pulse, the application of strong electric fields caused the emission sites to explode, forming cathode flares or plasma spots, and in this stage the space-charge-limited current was approximately described by a multiple-needle cathode model. As the pulse proceeded, these plasma spots merged and expanded towards the anode, thus increasing the emission area and shortening the diode gap, and the corresponding space-charge-limited current followed a planar cathode model. Finally, the space-charge-limited current is developed from a unipolar flow into a bipolar flow as a result of the appearance of anode plasma. In spite of the nonuniform distribution of cathode plasma, the cross-sectional uniformity of the extracted electron beam is satisfactory. The plasma expansion within the diode is found to be a major factor in the diode perveance growth and instability. These results show that these types of cathodes can offer promising applications for high-power microwave tubes.

Beam losses due to abrupt crab cavity failures in the LHC

International Nuclear Information System (INIS)

Baer, T.; Barranco, J.; Calaga, R.; Tomas, R.; Wenninger, B.; Yee, B.; Zimmermann, F.

2011-01-01

A major concern for the implementation of crab crossing in a future High-Luminosity LHC (HL-LHC) is machine protection in an event of a fast crab-cavity failure. Certain types of abrupt crab-cavity amplitude and phase changes are simulated to characterize the effect of failures on the beam and the resulting particle-loss signatures. The time-dependent beam loss distributions around the ring and particle trajectories obtained from the simulations allow for a first assessment of the resulting beam impact on LHC collimators and on sensitive components around the ring. Results for the nominal LHC lattice is presented.

Space charge effects and coherent stability limits in barrier buckets

Directory of Open Access Journals (Sweden)

Oliver Boine-Frankenheim

2003-03-01

Full Text Available A large-scale Vlasov simulation study of the microwave instability below transition energy in a beam confined between two barrier pulses is performed. Starting from a matched distribution function for the confined ion beam including the space charge impedance the stability threshold in the longitudinal impedance plane is obtained. A simple stability criterium is found to be in good agreement with the simulation results.

Compensating microphonics in SRF cavities to ensure beam stability for future free electron lasers

Energy Technology Data Exchange (ETDEWEB)

Neumann, Axel

2008-07-21

In seeded High-Gain-Harmonic-Generation free electron lasers or energy recovery linear accelerators the requirements for the bunch-to-bunch timing and energy jitter of the beam are in the femtosecond and per mill regime. This implies the ability to control the cavity radiofrequency (RF) field to an accuracy of 0.02 in phase and up to 1.10{sup -4} in amplitude. For the planned BESSY-FEL it is envisaged to operate 144 superconducting 1.3 GHz cavities of the 2.3 GeV driver linac in continuous wave mode and at a low beam current. The cavity resonance comprises a very narrow bandwidth of the order of tens of Hertz. Such cavities have been characterized under accelerator like conditions in the HoBiCaT test facility. It was possible to measure the error sources affecting the field stability in continuous wave (CW) operation. Microphonics, the main error source for a mechanical detuning of the cavities, lead to an average fluctuation of the cavity resonance of 1-5 Hz rms. Furthermore, the static and dynamic Lorentz force detuning and the helium pressure dependance of the cavity resonance have been measured. Single cavity RF control and linac bunch-to-bunch longitudinal phase space modeling containing the measured properties showed, that it is advisable to find means to minimize the microphonics detuning by mechanical tuning. Thus, several fast tuning systems have been tested for CW operation. These tuners consist of a motor driven lever for slow and coarse tuning and a piezo that is integrated into the tuner support for fast and fine tuning. Regarding the analysis of the detuning spectrum an adaptive feedforward method based on the least-mean-square filter algorithm has been developed for fast cavity tuning. A detuning compensation between a factor of two and up to a factor of seven has been achieved. Modeling the complete system including the fast tuning scheme, showed that the requirements of the BESSY-FEL are attainable. (orig.)

Compensating microphonics in SRF cavities to ensure beam stability for future free electron lasers

International Nuclear Information System (INIS)

Neumann, Axel

2008-01-01

In seeded High-Gain-Harmonic-Generation free electron lasers or energy recovery linear accelerators the requirements for the bunch-to-bunch timing and energy jitter of the beam are in the femtosecond and per mill regime. This implies the ability to control the cavity radiofrequency (RF) field to an accuracy of 0.02 in phase and up to 1.10 -4 in amplitude. For the planned BESSY-FEL it is envisaged to operate 144 superconducting 1.3 GHz cavities of the 2.3 GeV driver linac in continuous wave mode and at a low beam current. The cavity resonance comprises a very narrow bandwidth of the order of tens of Hertz. Such cavities have been characterized under accelerator like conditions in the HoBiCaT test facility. It was possible to measure the error sources affecting the field stability in continuous wave (CW) operation. Microphonics, the main error source for a mechanical detuning of the cavities, lead to an average fluctuation of the cavity resonance of 1-5 Hz rms. Furthermore, the static and dynamic Lorentz force detuning and the helium pressure dependance of the cavity resonance have been measured. Single cavity RF control and linac bunch-to-bunch longitudinal phase space modeling containing the measured properties showed, that it is advisable to find means to minimize the microphonics detuning by mechanical tuning. Thus, several fast tuning systems have been tested for CW operation. These tuners consist of a motor driven lever for slow and coarse tuning and a piezo that is integrated into the tuner support for fast and fine tuning. Regarding the analysis of the detuning spectrum an adaptive feedforward method based on the least-mean-square filter algorithm has been developed for fast cavity tuning. A detuning compensation between a factor of two and up to a factor of seven has been achieved. Modeling the complete system including the fast tuning scheme, showed that the requirements of the BESSY-FEL are attainable. (orig.)

Effect of scalar field mass on gravitating charged scalar solitons and black holes in a cavity

Energy Technology Data Exchange (ETDEWEB)

Ponglertsakul, Supakchai, E-mail: supakchai.p@gmail.com; Winstanley, Elizabeth, E-mail: E.Winstanley@sheffield.ac.uk

2017-01-10

We study soliton and black hole solutions of Einstein charged scalar field theory in cavity. We examine the effect of introducing a scalar field mass on static, spherically symmetric solutions of the field equations. We focus particularly on the spaces of soliton and black hole solutions, as well as studying their stability under linear, spherically symmetric perturbations of the metric, electromagnetic field, and scalar field.

Quantum mechanics of charged particle beam optics

CERN Document Server

Khan, Sameen Ahmed

2018-01-01

Theory of charged particle beam optics is basic to the design and working of charged particle beam devices from electron microscopes to accelerator machines. Traditionally, the optical elements of the devices are designed and operated based on classical mechanics and classical electromagnetism, and only certain specific quantum mechanical aspects are dealt with separately using quantum theory. This book provides a systematic approach to quantum theory of charged particle beam optics, particularly in the high energy cases such as accelerators or high energy electron microscopy.

Test measurement of a new TESLA cavity beam position monitor at the ELBE linac

International Nuclear Information System (INIS)

Sargsyan, V.; Schreiber, H.J.; Evtushenko, P.; Schurig, R.

2004-01-01

A new type of a cavity BPM proposed for beam position determination along the TESLA linac was tested at the accelerator ELBE in Rossendorf / Dresden. Measurements using an improved BPM (large and stable cross-talk isolation, significantly less energy dissipation, a novel LO signal generation) were performed in single- and multi-bunch regimes. Agreement with expectations was found. The low bunch charge available allowed for preliminary measurements on sensitivity and position resolution, which extrapolated to TESLA would ful l the demands for precise bunch-to-bunch position determination. Possible improvements, in particular on the signal processing scheme, are also discussed. (orig.)

Sparking limits, cavity loading, and beam breakup instability associated with high-current rf linacs

International Nuclear Information System (INIS)

Faehl, R.J.; Lemons, D.S.; Thode, L.E.

1982-01-01

The limitations on high-current rf linacs due to gap sparking, cavity loading, and the beam breakup instability are studied. It appears possible to achieve cavity accelerating gradients as high as 35 MV/m without sparking. Furthermore, a linear analysis, as well as self-consistent particle simulations of a multipulsed 10 kA beam, indicated that only a negligible small fraction of energy is radiated into nonfundamental cavity modes. Finally, the beam breakup instability is analyzed and found to be able to magnify initial radial perturbations by a factor of no more than about 20 during the beam transit time through a 1 GeV accelerator

Design study of longitudinal dynamics of the drive beam in 1 TeV relativistic klystron two-beam accelerator

International Nuclear Information System (INIS)

Li, H.; Yu, S.S.; Sessler, A.M.

1994-10-01

In this paper the authors present a design study on the longitudinal dynamics of a relativistic klystron two-beam accelerator (RK-TBA) scheme which has been proposed as a power source candidate for a 1 TeV next linear collider (NLC). They address the issue of maintaining stable power output at desired level for a 300-m long TBA with 150 extraction cavities and present their simulation results to demonstrate that it can be achieved by inductively detuning the extraction cavities to counter the space charge debunching effect on the drive beam. They then carry out simulation study to show that the beam bunches desired by the RK-TBA can be efficiently obtained by first chopping an initially uniform beam of low energy into a train of beam bunches with modest longitudinal dimension and then using the open-quotes adiabatic captureclose quotes scheme to bunch and accelerate these beam bunches into tight bunches at the operating energy of the drive beam. The authors have also examined the open-quotes after burnerclose quotes scheme which is implemented in their RK-TBA design for efficiency enhancement

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

Energy Technology Data Exchange (ETDEWEB)

Teng, J.; Gu, Y.Q., E-mail: tengjian@mail.ustc.edu.cn; Zhu, B.; Hong, W.; Zhao, Z.Q.; Zhou, W.M.; Cao, L.F.

2013-11-21

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator.

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

Science.gov (United States)

Teng, J.; Gu, Y. Q.; Zhu, B.; Hong, W.; Zhao, Z. Q.; Zhou, W. M.; Cao, L. F.

2013-11-01

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator.

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

International Nuclear Information System (INIS)

Teng, J.; Gu, Y.Q.; Zhu, B.; Hong, W.; Zhao, Z.Q.; Zhou, W.M.; Cao, L.F.

2013-01-01

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator

Emittance growth and halo formation in charge-dominated beams

Energy Technology Data Exchange (ETDEWEB)

Bondarev, B.I.; Durkin, A.P.; Murin, B.P. [Moscow Radiotechnical Institute (Russian Federation)] [and others

1995-10-01

The optimization of high-current high-energy linacs against the low beam loss requirement is not straightforward or well-codified. Outlying particle losses at the 10{sup {minus}5} up to 10{sup {minus}8} level might have only a small effect on the rms properties of the beam, and thus the total beam size must be constantly kept under observation. RMS-physics has gained wide-spread acceptance as a necessary design tool, but its sufficiency is an issue for ATW/ABC accelerators.

Investigations on the transverse phase space at a photo injector for minimized emittance

Energy Technology Data Exchange (ETDEWEB)

Miltchev, V.

2006-08-15

Radio frequency photoinjectors are electron sources able to generate beams of extremely high brightness, which are applicable to linac driven Free Electron Lasers (FEL). Because of the high phase space density, the dynamics of the electron beam is dominated by space charge interactions between the particles. This thesis studies the transverse phase space of space charge dominated electron beams produced by the Photo Injector Test Facility in Zeuthen (PITZ). The operation conditions for minimizing the transverse emittance are studied experimentally, theoretically and in simulations. The influence of the longitudinal profile of the driving UV laser pulse on the transverse emittance is investigated. Emphasis is placed on the experimental study of the emittance as a function of different machine parameters like the laser beam spot size, the amplitude of the focusing magnetic field, the rf phase and the electron bunch charge. First investigations on the thermal emittance for Cs{sub 2}Te photocathodes under rf operating conditions are presented. Measurements of the thermal emittance scaling with the photocathode laser spot size are analyzed. The significance of the applied rf field in the emittance formation process is discussed. (orig.)

Investigations on the transverse phase space at a photo injector for minimized emittance

International Nuclear Information System (INIS)

Miltchev, V.

2006-08-01

Radio frequency photoinjectors are electron sources able to generate beams of extremely high brightness, which are applicable to linac driven Free Electron Lasers (FEL). Because of the high phase space density, the dynamics of the electron beam is dominated by space charge interactions between the particles. This thesis studies the transverse phase space of space charge dominated electron beams produced by the Photo Injector Test Facility in Zeuthen (PITZ). The operation conditions for minimizing the transverse emittance are studied experimentally, theoretically and in simulations. The influence of the longitudinal profile of the driving UV laser pulse on the transverse emittance is investigated. Emphasis is placed on the experimental study of the emittance as a function of different machine parameters like the laser beam spot size, the amplitude of the focusing magnetic field, the rf phase and the electron bunch charge. First investigations on the thermal emittance for Cs 2 Te photocathodes under rf operating conditions are presented. Measurements of the thermal emittance scaling with the photocathode laser spot size are analyzed. The significance of the applied rf field in the emittance formation process is discussed. (orig.)

Design of inductively detuned RF extraction cavities for the Relativistic Klystron Two Beam Accelerator

International Nuclear Information System (INIS)

Henestroza, E.; Yu, S.S.; Li, H.

1995-04-01

An inductively detuned traveling wave cavity for the Relativistic Klystron Two Beam Accelerator expected to extract high RF power at 11. 424 GHz for the 1 TeV Center of Mass Next Linear Collider has been designed. Longitudinal beam dynamics studies led to the following requirements on cavity design: (a) Extraction of 360 MW of RF power with RF component of the current being 1.15 kAmps at 11.424 GHz, (b) Inductively detuned traveling wave cavity with wave phase velocity equal to 4/3 the speed of light, (c) Output cavity with appropriate Q ext and eigenfrequency for proper matching. Furthermore, transverse beam dynamics require low shunt impedances to avoid the beam break-up instability. We describe the design effort to meet these criteria based on frequency-domain and time-domain computations using 2D- and 3D- electromagnetic codes

Space-charge-mediated anomalous ferroelectric switching in P(VDF-TrEE) polymer films

KAUST Repository

Hu, Weijin

2014-11-12

We report on the switching dynamics of P(VDF-TrEE) copolymer devices and the realization of additional substable ferroelectric states via modulation of the coupling between polarizations and space charges. The space-charge-limited current is revealed to be the dominant leakage mechanism in such organic ferroelectric devices, and electrostatic interactions due to space charges lead to the emergence of anomalous ferroelectric loops. The reliable control of ferroelectric switching in P(VDF-TrEE) copolymers opens doors toward engineering advanced organic memories with tailored switching characteristics.

Broad-band beam buncher

International Nuclear Information System (INIS)

Goldberg, D.A.; Flood, W.S.; Arthur, A.A.; Voelker, F.

1986-01-01

This patent describes a broad-band beam buncher. This beam buncher consists of: a housing adapted to be eacuated, an electron gun in the housing for producing a beam of electrons, buncher means in the housing forming a buncher cavity which has an entrance opening for receiving the electron beam and an exit opening through which the electron beam passes out of the buncher cavity, a drift tube electrode in the buncher cavity and disposed between the entrance opening and the exit opening with first and second gaps between the drift tube electrode and the entrance and exit openings, the drift tube electrode which has a first drift space through which the electron beam passes in traveling between the entrance and exit openings, modulating means for supplying an ultrahigh frequeny modulating signal to the drift tube electrode for producing velocity modulation of the electrons in the electron beam as the electrons pass through the buncher cavity and the drift tube electrode between the entrance opening and the exit opening, drift space means in the housing forming a second drift space for receiving the velocity modulated electron beam from the exit opening, the velocity modulated electron beam being bunched as it passes along the second drift space, the drift space means has a discharge opening through which the electron beam is discharged from the second drift space after being bunched therein, the modulating means containing a signal source for producing an ultrahigh frequency signal, a transmission line connected between the signal source and the drift tube electrode, and terminating means connected to the drift tube electrode for terminating the transmission line in approximately its characteristic impedance to afford a broad response band with minimum 6 variations therein

Discrete space charge affected field emission: Flat and hemisphere emitters

Energy Technology Data Exchange (ETDEWEB)

Jensen, Kevin L., E-mail: kevin.jensen@nrl.navy.mil [Code 6854, Naval Research Laboratory, Washington, DC 20375 (United States); Shiffler, Donald A.; Tang, Wilkin [Air Force Research Laboratory, Kirtland AFB, New Mexico 87117 (United States); Rittersdorf, Ian M. [Code 6770, Naval Research Laboratory, Washington, DC 20375 (United States); Lebowitz, Joel L. [Department of Mathematics and Department of Physics, Rutgers University, Piscataway, New Jersey 08854-8019 (United States); Harris, John R. [U.S. Navy Reserve, New Orleans, Louisiana 70143 (United States); Lau, Y. Y. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Petillo, John J. [Leidos, Billerica, Massachusetts 01821 (United States); Luginsland, John W. [Physics and Electronics Directorate, AFOSR, Arlington, Virginia 22203 (United States)

2015-05-21

Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surface roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.

Implementation of intra-cavity beam shaping technique to enhance pump efficiency

CSIR Research Space (South Africa)

Litvin, IA

2012-02-01

Full Text Available In this work the author proposes an implementation of a new intra-cavity beam shaping technique to vary the intensity distribution of the fundamental mode in a resonator cavity while maintaining a constant intensity distribution at the output...

CAVITY BEAM POSITION MONITOR SYSTEM FOR ATF2

CERN Document Server

Boogert, S T; Boorman, G; Molloy, S; Ross, M; Aryshev, A; Honda, Y; Terunuma, N; Urakawa, J; Kim, E S; Kim, Y I; Heo, A E; Lyapin, A; Swinson, C J; Frisch, J; McCormick, D M; Nelson, J; Smith, T; White, G R

2010-01-01

The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a future high energy lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (CBPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance.

Adaptive Beam Loading Compensation in Room Temperature Bunching Cavities

Energy Technology Data Exchange (ETDEWEB)

Edelen, J. P. [Fermilab; Chase, B. E. [Fermilab; Cullerton, E. [Fermilab; Varghese, P. [Fermilab

2017-10-01

In this paper we present the design, simulation, and proof of principle results of an optimization based adaptive feedforward algorithm for beam-loading compensation in a high impedance room temperature cavity. We begin with an overview of prior developments in beam loading compensation. Then we discuss different techniques for adaptive beam loading compensation and why the use of Newton?s Method is of interest for this application. This is followed by simulation and initial experimental results of this method.

Charge reconstruction of the DAMPE Silicon-Tungsten Tracker: A preliminary study with ion beams

Science.gov (United States)

Qiao, Rui; Peng, Wen-Xi; Guo, Dong-Ya; Zhao, Hao; Wang, Huan-Yu; Gong, Ke; Zhang, Fei; Wu, Xin; Azzarello, Phillip; Tykhonov, Andrii; Asfandiyarov, Ruslan; Gallo, Valentina; Ambrosi, Giovanni

2018-04-01

The DArk Matter Particle Explorer (DAMPE) is one of the four satellites within Strategic Pioneer Research Program in Space Science of the Chinese Academy of Science (CAS). DAMPE can detect electrons, photons in a wide energy range (5 GeV to 10 TeV) and ions up to iron (100 GeV to 100 TeV). The silicon-Tungsten Tracker (STK) is one of the four subdetectors in DAMPE, providing photon-electron conversion, track reconstruction and charge identification for ions. An ion beam test was carried out in CERN with 60 GeV/u Lead primary beams. Charge reconstruction and charge resolution of the STK detectors were investigated.

arXiv Charge reconstruction study of the DAMPE Silicon-Tungsten Tracker with ion beams

CERN Document Server

Qiao, Rui; Guo, Dong-Ya; Zhao, Hao; Wang, Huan-Yu; Gong, Ke; Zhang, Fei; Wu, Xin; Azzarello, Phillip; Tykhonov, Andrii; Asfandiyarov, Ruslan; Gallo, Valentina; Ambrosi, Giovanni; Mazziotta, Nicola; De Mitri, Ivan

The DArk Matter Particle Explorer (DAMPE) is one of the four satellites within Strategic Pioneer Research Program in Space Science of the Chinese Academy of Science (CAS). DAMPE can detect electrons, photons in a wide energy range (5 GeV to 10 TeV) and ions up to iron (100GeV to 100 TeV). Silicon-Tungsten Tracker (STK) is one of the four subdetectors in DAMPE, providing photon-electron conversion, track reconstruction and charge identification for ions. Ion beam test was carried out in CERN with 60GeV/u Lead primary beams. Charge reconstruction and charge resolution of STK detectors were investigated.

Recent Progress on the Marylie/Impact Beam Dynamics Code

International Nuclear Information System (INIS)

Ryne, R.D.; Qiang, J.; Bethel, E.W.; Pogorelov, I.; Shalf, J.; Siegerist, C.; Venturini, M.; Dragt, A.J.; Adelmann, A.; Abell, D.; Amundson, J.; Spentzouris, P.; Neri, F.; Walstrom, P.; Mottershead, C.T.; Samulyak, R.

2006-01-01

MARYLIE/IMPACT (ML/I) is a hybrid code that combines the beam optics capabilities of MARYLIE with the parallel Particle-In-Cell capabilities of IMPACT. In addition to combining the capabilities of these codes, ML/I has a number of powerful features, including a choice of Poisson solvers, a fifth-order rf cavity model, multiple reference particles for rf cavities, a library of soft-edge magnet models, representation of magnet systems in terms of coil stacks with possibly overlapping fields, and wakefield effects. The code allows for map production, map analysis, particle tracking, and 3D envelope tracking, all within a single, coherent user environment. ML/I has a front end that can read both MARYLIE input and MAD lattice descriptions. The code can model beams with or without acceleration, and with or without space charge. Developed under a US DOE Scientific Discovery through Advanced Computing (SciDAC) project, ML/I is well suited to large-scale modeling, simulations having been performed with up to 100M macroparticles. The code inherits the powerful fitting and optimizing capabilities of MARYLIE augmented for the new features of ML/I. The combination of soft-edge magnet models, high-order capability, space charge effects, and fitting/optimization capabilities, make ML/I a powerful code for a wide range of beam optics design problems. This paper provides a description of the code and its unique capabilities

Electron beam charge state amplifier (EBQA)--a conceptual evaluation

International Nuclear Information System (INIS)

Dooling, J. C.

1998-01-01

A concept is presented for stripping low-energy, radioactive ions from 1+ to higher charge states. Referred to as an Electron Beam Charge State Amplifier (EBQA), this device accepts a continuous beam of singly-charged, radioactive ions and passes them through a high-density electron beam confined by a solenoidal magnetic field. Singly-charged ions may be extracted from standard Isotope-Separator-Online (ISOL) sources. An EBQA is potentially useful for increasing the charge state of ions prior to injection into post-acceleration stages at ISOL radioactive beam facilities. The stripping efficiency from q=1+ to 2+ (η 12 ) is evaluated as a function of electron beam radius at constant current with solenoid field, injected ion energy, and ion beam emittance used as parameters. Assuming a 5 keV, 1 A electron beam, η 12 = 0.38 for 0.1 keV, 132 Xe ions passing through an 8 Tesla solenoid, 1 m in length. Multi-pass configurations to achieve 3+ or 4+ charge states are also conceivable. The calculated efficiencies depend inversely on the initial ion beam emittances. The use of a helium-buffer-gas, ion-guide stage to improve the brightness of the 1+ beams [1] may enhance the performance of an EBQA

Resolution of a High Performance Cavity Beam Position Monitor System

International Nuclear Information System (INIS)

Walston, S.; Chung, C.; Fitsos, P.; Gronberg, J.; Ross, M.; Khainovski, O.; Kolomensky, Y.; Loscutoff, P.; Slater, M.; Thomson, M.; Ward, D.; Boogert, S.; Vogel, V.; Meller, R.; Lyapin, A.; Malton, S.; Miller, D.; Frisch, J.; Hinton, S.; May, J.; McCormick, D.; Smith, S.; Smith, T.; White, G.; Orimoto, T.; Hayano, H.; Honda, Y.; Terunuma, N.; Urakawa, J.

2005-01-01

International Linear Collider (ILC) interaction region beam sizes and component position stability requirements will be as small as a few nanometers. It is important to the ILC design effort to demonstrate that these tolerances can be achieved - ideally using beam-based stability measurements. It has been estimated that RF cavity beam position monitors (BPMs) could provide position measurement resolutions of less than one nanometer and could form the basis of the desired beam-based stability measurement. We have developed a high resolution RF cavity BPM system. A triplet of these BPMs has been installed in the extraction line of the KEK Accelerator Test Facility (ATF) for testing with its ultra-low emittance beam. A metrology system for the three BPMs was recently installed. This system employed optical encoders to measure each BPM's position and orientation relative to a zero-coefficient of thermal expansion carbon fiber frame and has demonstrated that the three BPMs behave as a rigid-body to less than 5 nm. To date, we have demonstrated a BPM resolution of less than 20 nm over a dynamic range of +/- 20 microns

ECR plasma source for heavy ion beam charge neutralization

Science.gov (United States)

Efthimion, Philip C.; Gilson, Erik; Grisham, Larry; Kolchin, Pavel; Davidson, Ronald C.; Yu, Simon; Logan, B. Grant

2003-01-01

Highly ionized plasmas are being considered as a medium for charge neutralizing heavy ion beams in order to focus beyond the space-charge limit. Calculations suggest that plasma at a density of 1 100 times the ion beam density and at a length [similar]0.1 2 m would be suitable for achieving a high level of charge neutralization. An Electron Cyclotron Resonance (ECR) source has been built at the Princeton Plasma Physics Laboratory (PPPL) to support a joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 1 10 gauss. The goal is to operate the source at pressures [similar]10[minus sign]6 Torr at full ionization. The initial operation of the source has been at pressures of 10[minus sign]4 10[minus sign]1 Torr. Electron densities in the range of 108 to 1011 cm[minus sign]3 have been achieved. Low-pressure operation is important to reduce ion beam ionization. A cusp magnetic field has been installed to improve radial confinement and reduce the field strength on the beam axis. In addition, axial confinement is believed to be important to achieve lower-pressure operation. To further improve breakdown at low pressure, a weak electron source will be placed near the end of the ECR source. This article also describes the wave damping mechanisms. At moderate pressures (> 1 mTorr), the wave damping is collisional, and at low pressures (< 1 mTorr) there is a distinct electron cyclotron resonance.

The dispersion relation of charge and current compensated relativistic electron beam-plasma system

International Nuclear Information System (INIS)

Vrba, P.; Schroetter, J.; Jarosova, P.; Koerbel, S.

1978-01-01

The unstable regions of relativistic electron beam-plasma system were determined by analysing the general dispersion relation numerically. The external parameters were varied to ensure more effective instability excitations. The full charge- and current compensation presumptions lead to the new synchronism predictions. The slow space charge wave and slow cyclotron wave of the return current are synchronous with the plasma ion wave. (author)

Interaction between beam control and rf feedback loops for high Q cavities an heavy beam loading. Revision A

International Nuclear Information System (INIS)

Mestha, L.K.; Kwan, C.M.; Yeung, K.S.

1994-04-01

An open-loop state space model of all the major low-level rf feedback control loops is derived. The model has control and state variables for fast-cycling machines to apply modern multivariable feedback techniques. A condition is derived to know when exactly we can cross the boundaries between time-varying and time-invariant approaches for a fast-cycling machine like the Low Energy Booster (LEB). The conditions are dependent on the Q of the cavity and the rate at which the frequency changes with time. Apart from capturing the time-variant characteristics, the errors in the magnetic field are accounted in the model to study the effects on synchronization with the Medium Energy Booster (MEB). The control model is useful to study the effects on beam control due to heavy beam loading at high intensities, voltage transients just after injection especially due to time-varying voltages, instability thresholds created by the cavity tuning feedback system, cross coupling between feedback loops with and without direct rf feedback etc. As a special case we have shown that the model agrees with the well known Pedersen model derived for the CERN PS booster. As an application of the model we undertook a detailed study of the cross coupling between the loops by considering all of them at once for varying time, Q and beam intensities. A discussion of the method to identify the coupling is shown. At the end a summary of the identified loop interactions is presented

Experimental study of the transport limits of intense heavy ion beams in the HCX

International Nuclear Information System (INIS)

Prost, L.R.; Bieniosek, F.M.; Celata, C.M.; Dugan, C.C.; Faltens, A.; Seidl, P.A.; Waldron, W.L.; Cohen, R.; Friedman, A.; Kireeff Covo, M.; Lund, S.M.; Molvik, A.W.; Haber, I.

2004-01-01

The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program to explore heavy-ion beam transport at a scale representative of the low-energy end of an induction linac driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge-dominated heavy-ion beams at high space-charge intensity (line charge density up to ∼ 0.2 (micro)C/m) over long pulse durations (4 (micro)s) in alternating gradient focusing lattices of electrostatic or magnetic quadrupoles. The experiment also contributes to the practical baseline knowledge of intense beam manipulations necessary for the design, construction and operation of a heavy ion driver for inertial fusion. This experiment is testing transport issues resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and beam steering, matching, image charges, halo, electron cloud effects, and longitudinal bunch control. We first present the results for a coasting 1 MeV K + ion beam transported through the first ten electrostatic transport quadrupoles, measured with optical beam-imaging and double-slit phase-space diagnostics. This includes studies at two different radial fill factors (60% and 80%), for which the beam transverse distribution was characterized in detail. Additionally, beam energy measurements will be shown. We then discuss the first results of beam transport through four pulsed room-temperature magnetic quadrupoles (located downstream of the electrostatic quadrupoles), where the beam dynamics become more sensitive to the presence of secondary electrons

SLC injector simulation and tuning for high charge transport

International Nuclear Information System (INIS)

Yeremian, A.D.; Miller, R.H.; Clendenin, J.E.; Early, R.A.; Ross, M.C.; Turner, J.L.; Wang, J.W.

1992-01-01

We have simulated the SLC injector from the thermionic gun through the first accelerating section and used the resulting parameters to tune the injector for optimum performance and high charge transport. Simulations are conducted using PARMELA, a three-dimensional space-charge model. The magnetic field profile due to the existing magnetic optics is calculated using POISSON, while SUPERFISH is used to calculate the space harmonics of the various bunchers and the accelerator cavities. The initial beam conditions in the PARMELA code are derived from the EGUN model of the gun. The resulting injector parameters from the PARMELA simulation are used to prescribe experimental settings of the injector components. The experimental results are in agreement with the results of the integrated injector model. (Author) 5 figs., 7 refs

High Pressure, High Gradient RF Cavities for Muon Beam Cooling

CERN Document Server

Johnson, R P

2004-01-01

High intensity, low emittance muon beams are needed for new applications such as muon colliders and neutrino factories based on muon storage rings. Ionization cooling, where muon energy is lost in a low-Z absorber and only the longitudinal component is regenerated using RF cavities, is presently the only known cooling technique that is fast enough to be effective in the short muon lifetime. RF cavities filled with high-pressure hydrogen gas bring two advantages to the ionization technique: the energy absorption and energy regeneration happen simultaneously rather than sequentially, and higher RF gradients and better cavity breakdown behavior are possible than in vacuum due to the Paschen effect. These advantages and some disadvantages and risks will be discussed along with a description of the present and desired RF R&D efforts needed to make accelerators and colliders based on muon beams less futuristic.

Ion beam neutralization with ferroelectrically generated electron beams

Energy Technology Data Exchange (ETDEWEB)

Herleb, U; Riege, H [European Organization for Nuclear Research, Geneva (Switzerland). LHC Division

1997-12-31

A technique for ion beam space-charge neutralization with pulsed electron beams is described. The intensity of multiply-charged ions produced with a laser ion source can be enhanced or decreased separately with electron beam trains of MHz repetition rate. These are generated with ferroelectric cathodes, which are pulsed in synchronization with the laser ion source. The pulsed electron beams guide the ion beam in a similar way to the alternating gradient focusing of charged particle beams in circular accelerators such as synchrotrons. This new neutralization technology overcomes the Langmuir-Child space-charge limit and may in future allow ion beam currents to be transported with intensities by orders of magnitude higher than those which can be accelerated today in a single vacuum tube. (author). 6 figs., 10 refs.

A multigrid based 3D space-charge routine in the tracking code GPT

NARCIS (Netherlands)

Pöplau, G.; Rienen, van U.; Loos, de M.J.; Geer, van der S.B.; Berz, M.; Makino, K.

2005-01-01

Fast calculation of3D non-linear space-charge fields is essential for the simulation ofhigh-brightness charged particle beams. We report on our development of a new 3D spacecharge routine in the General Particle Tracer (GPT) code. The model is based on a nonequidistant multigrid Poisson solver that

Linear beam dynamics and ampere class superconducting RF cavities at RHIC

Science.gov (United States)

Calaga, Rama R.

The Relativistic Heavy Ion Collider (RHIC) is a hadron collider designed to collide a range of ions from protons to gold. RHIC operations began in 2000 and has successfully completed five physics runs with several species including gold, deuteron, copper, and polarized protons. Linear optics and coupling are fundamental issues affecting the collider performance. Measurement and correction of optics and coupling are important to maximize the luminosity and sustain stable operation. A numerical approach, first developed at SLAC, was implemented to measure linear optics from coherent betatron oscillations generated by ac dipoles and recorded at multiple beam position monitors (BPMs) distributed around the collider. The approach is extended to a fully coupled 2D case and equivalence relationships between Hamiltonian and matrix formalisms are derived. Detailed measurements of the transverse coupling terms are carried out at RHIC and correction strategies are applied to compensate coupling both locally and globally. A statistical approach to determine BPM reliability and performance over the past three runs and future improvements also discussed. Aiming at a ten-fold increase in the average heavy-ion luminosity, electron cooling is the enabling technology for the next luminosity upgrade (RHIC II). Cooling gold ion beams at 100 GeV/nucleon requires an electron beam of approximately 54 MeV and a high average current in the range of 50-200 mA. All existing e-Coolers are based on low energy DC accelerators. The only viable option to generate high current, high energy, low emittance CW electron beam is through a superconducting energy-recovery linac (SC-ERL). In this option, an electron beam from a superconducting injector gun is accelerated using a high gradient (˜ 20 MV/m) superconducting RF (SRF) cavity. The electrons are returned back to the cavity with a 180° phase shift to recover the energy back into the cavity before being dumped. A design and development of a half

Acoustic energy harvesting by piezoelectric curved beams in the cavity of a sonic crystal

International Nuclear Information System (INIS)

Wang, Wei-Chung; Wu, Liang-Yu; Chen, Lien-Wen; Liu, Chia-Ming

2010-01-01

Acoustic energy harvesting by piezoelectric curved beams in the cavity of a sonic crystal is investigated. A resonant cavity of the sonic crystal is used to localize the acoustic wave as the acoustic waves are incident into the sonic crystal at the resonant frequency. The piezoelectric curved beam is placed in the resonant cavity and vibrated by the acoustic wave. The energy harvesting can be achieved as the acoustic waves are incident at the resonant frequency. A model for energy harvesting of the piezoelectric curved beam is also developed to predict the output voltage and power of the energy harvesting. The experimental results are compared with the theoretical

Space charge effects and aberrations on electron pulse compression in a spherical electrostatic capacitor.

Science.gov (United States)

Yu, Lei; Li, Haibo; Wan, Weishi; Wei, Zheng; Grzelakowski, Krzysztof P; Tromp, Rudolf M; Tang, Wen-Xin

2017-12-01

The effects of space charge, aberrations and relativity on temporal compression are investigated for a compact spherical electrostatic capacitor (α-SDA). By employing the three-dimensional (3D) field simulation and the 3D space charge model based on numerical General Particle Tracer and SIMION, we map the compression efficiency for a wide range of initial beam size and single-pulse electron number and determine the optimum conditions of electron pulses for the most effective compression. The results demonstrate that both space charge effects and aberrations prevent the compression of electron pulses into the sub-ps region if the electron number and the beam size are not properly optimized. Our results suggest that α-SDA is an effective compression approach for electron pulses under the optimum conditions. It may serve as a potential key component in designing future time-resolved electron sources for electron diffraction and spectroscopy experiments. Copyright © 2017 Elsevier B.V. All rights reserved.

Study of nonlinear interaction between bunched beam and intermediate cavities in a relativistic klystron amplifier

Energy Technology Data Exchange (ETDEWEB)

Wu, Y. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China); Science and Technology on High Power Microwave Laboratory, Mianyang 621900 (China); Xu, Z.; Li, Z. H. [Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China); Tang, C. X. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2012-07-15

In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.

Study of nonlinear interaction between bunched beam and intermediate cavities in a relativistic klystron amplifier

Science.gov (United States)

Wu, Y.; Xu, Z.; Li, Z. H.; Tang, C. X.

2012-07-01

In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.

Space-Charge Simulation of Integrable Rapid Cycling Synchrotron

Energy Technology Data Exchange (ETDEWEB)

Eldred, Jeffery [Fermilab; Valishev, Alexander [Fermilab

2017-05-01

Integrable optics is an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use a Synergia space-charge simulation to investigate the application of integrable optics to a high-intensity hadron ring that could replace the Fermilab Booster. We find that incorporating integrability into the design suppresses the beam halo generated by a mismatched KV beam. Our integrable rapid cycling synchrotron (iRCS) design includes other features of modern ring design such as low momentum compaction factor and harmonically canceling sextupoles. Experimental tests of high-intensity beams in integrable lattices will take place over the next several years at the Fermilab Integrable Optics Test Accelerator (IOTA) and the University of Maryland Electron Ring (UMER).

Eccentric superconducting rf cavity separator structure

International Nuclear Information System (INIS)

Aggus, J.R.; Giordano, S.T.; Halama, H.J.

1976-01-01

An accelerator apparatus is described having an eccentric-shaped, iris-loaded deflecting cavity for an rf separator for a high energy high momentum, charged particle accelerator beam. In one embodiment, the deflector is superconducting, and the apparatus of this invention provides simplified machining and electron beam welding techniques. Model tests have shown that the electrical characteristics provide the desired mode splitting without adverse effects

Pbar Beam Stacking in the Recycler by Longitudinal Phase-space Coating

Energy Technology Data Exchange (ETDEWEB)

Bhat, C. M. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

2013-08-06

Barrier rf buckets have brought about new challenges in longitudinal beam dynamics of charged particle beams in synchrotrons and at the same time led to many new remarkable prospects in beam handling. In this paper, I describe a novel beam stacking scheme for synchrotrons using barrier buckets without any emittance dilution to the beam. First I discuss the general principle of the method, called longitudinal phase-space coating. Multi-particle beam dynamics simulations of the scheme applied to the Recycler, convincingly validates the concepts and feasibility of the method. Then I demonstrate the technique experimentally in the Recycler and also use it in operation. A spin-off of this scheme is its usefulness in mapping the incoherent synchrotron tune spectrum of the beam particles in barrier buckets and producing a clean hollow beam in longitudinal phase space. Both of which are described here in detail with illustrations. The beam stacking scheme presented here is the first of its kind.

Beam dynamics of mixed high intensity highly charged ion Beams in the Q/A selector

Energy Technology Data Exchange (ETDEWEB)

Zhang, X.H., E-mail: zhangxiaohu@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Yuan, Y.J.; Yin, X.J.; Qian, C.; Sun, L.T. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Du, H.; Li, Z.S.; Qiao, J.; Wang, K.D. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao, H.W.; Xia, J.W. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2017-06-11

Electron cyclotron resonance (ECR) ion sources are widely used in heavy ion accelerators for their advantages in producing high quality intense beams of highly charged ions. However, it exists challenges in the design of the Q/A selection systems for mixed high intensity ion beams to reach sufficient Q/A resolution while controlling the beam emittance growth. Moreover, as the emittance of beam from ECR ion sources is coupled, the matching of phase space to post accelerator, for a wide range of ion beam species with different intensities, should be carefully studied. In this paper, the simulation and experimental results of the Q/A selection system at the LECR4 platform are shown. The formation of hollow cross section heavy ion beam at the end of the Q/A selector is revealed. A reasonable interpretation has been proposed, a modified design of the Q/A selection system has been committed for HIRFL-SSC linac injector. The features of the new design including beam simulations and experiment results are also presented.

Space charge dynamic of irradiated cyanate ester/epoxy at cryogenic temperatures

Science.gov (United States)

Wang, Shaohe; Tu, Youping; Fan, Linzhen; Yi, Chengqian; Wu, Zhixiong; Li, Laifeng

2018-03-01

Glass fibre reinforced polymers (GFRPs) have been widely used as one of the main electrical insulating structures for superconducting magnets. A new type of GFRP insulation material using cyanate ester/epoxy resin as a matrix was developed in this study, and the samples were irradiated by Co-60 for 1 MGy and 5 MGy dose. Space charge distributed within the sample were tested using the pulsed electroacoustic method, and charge concentration was found at the interfaces between glass fibre and epoxy resin. Thermally stimulated current (TSC) and dc conduction current were also tested to evaluate the irradiation effect. It was supposed that charge mobility and density were suppressed at the beginning due to the crosslinking reaction, and for a higher irradiation dose, molecular chain degradation dominated and led to more sever space charge accumulation at interfaces which enhance the internal electric field higher than the external field, and transition field for conduction current was also decreased by irradiation. Space charge dynamic at cryogenic temperature was revealed by conduction current and TSC, and space charge injection was observed for the irradiated samples at 225 K, which was more obvious for the irradiated samples.

Generation of angular-momentum-dominated electron beams from a photoinjector

International Nuclear Information System (INIS)

Sun, Yin-E.; Piot, Philippe; Kim, Kwang-Je; Barov, Nikolas; Lidia, Steven; Santucci, James; Tikhoplav, Rodion; Wennerberg, Jason

2004-01-01

Various projects under study require an angular-momentum-dominated electron beam generated by a photoinjector. Some of the proposals directly use the angular-momentum-dominated beams (e.g. electron cooling of heavy ions), while others require the beam to be transformed into a flat beam (e.g. possible electron injectors for light sources and linear colliders). In this paper, we report our experimental study of an angular-momentum-dominated beam produced in a photoinjector, addressing the dependencies of angular momentum on initial conditions. We also briefly discuss the removal of angular momentum. The results of the experiment, carried out at the Fermilab/NICADD Photoinjector Laboratory, are found to be in good agreement with theoretical and numerical models

Severe signal loss in diamond beam loss monitors in high particle rate environments by charge trapping in radiation-induced defects

CERN Document Server

Kassel, Florian; Dabrowski, Anne; de Boer, Wim

2016-01-01

The beam condition monitoring leakage (BCML) system is a beam monitoring device in the compact muon solenoid (CMS) experiment at the large hadron collider (LHC). As detectors 32 poly-crystalline (pCVD) diamond sensors are positioned in rings around the beam pipe. Here, high particle rates occur from the colliding beams scattering particles outside the beam pipe. These particles cause defects, which act as traps for the ionization, thus reducing the charge collection efficiency (CCE). However, the loss in CCE was much more severe than expected from low rate laboratory measurements and simulations, especially in single-crystalline (sCVD) diamonds, which have a low initial concentration of defects. The reason why in real experiments the CCE is much worse than in laboratory experiments is related to the ionization rate. At high particle rates the trapping rate of the ionization is so high compared with the detrapping rate, that space charge builds up. This space charge reduces locally the internal electric field,...

Simulation of oscillatory processes in a beam-plasma system with a virtual cathode in gas-filled interaction space

International Nuclear Information System (INIS)

Filatov, R. A.; Hramov, A. E.

2011-01-01

Physical processes occurring in an intense electron beam with a virtual cathode in an interaction space filled with neutral gas are studied in a two-dimensional model. A mathematical model is proposed for investigating complicated self-consistent processes of neutral gas ionization by the beam electrons and the dynamics of an electron beam and heavy positive ions in the common space charge field with allowance for the two-dimensional motion of charged particles. Three characteristic dynamic regimes of the system are revealed: complete suppression of oscillations of the virtual cathode as a result of neutralizing its space charge by positive ions; the pulsed generation regime, in which the ions dynamics repeatedly suppresses and restores the virtual cathode oscillations; and the continuous generation regime with an anomalously high level of noisy oscillations.

A study of beam position diagnostics using beam-excited dipole modes in third harmonic superconducting accelerating cavities at a free-electron laser

Energy Technology Data Exchange (ETDEWEB)

Zhang Pei [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg (Germany); Baboi, Nicoleta [Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg (Germany); Jones, Roger M.; Shinton, Ian R. R. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Cockcroft Institute, Cheshire WA4 4AD (United Kingdom); Flisgen, Thomas; Glock, Hans-Walter [Institut fuer Allgemeine Elektrotechnik, Universitaet Rostock, 18051 Rostock (Germany)

2012-08-15

We investigate the feasibility of beam position diagnostics using higher order mode (HOM) signals excited by an electron beam in the third harmonic 3.9 GHz superconducting accelerating cavities at FLASH. After careful theoretical and experimental assessment of the HOM spectrum, three modal choices have been narrowed down to fulfill different diagnostics requirements. These are localized dipole beam-pipe modes, trapped cavity modes from the fifth dipole band, and propagating modes from the first two dipole bands. These modes are treated with various data analysis techniques: modal identification, direct linear regression (DLR), and singular value decomposition (SVD). Promising options for beam diagnostics are found from all three modal choices. This constitutes the first prediction, subsequently confirmed by experiments, of trapped HOMs in third harmonic cavities, and also the first direct comparison of DLR and SVD in the analysis of HOM-based beam diagnostics.

A study of beam position diagnostics using beam-excited dipole modes in third harmonic superconducting accelerating cavities at a free-electron laser

CERN Document Server

Zhang, P; Jones, R M; Shinton, I R R; Flisgen, T; Glock, H W

2012-01-01