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Heavy ion fusion 2 MV injector

Description: A heavy-ion-fusion driver-scale injector has been constructed and operated at Lawrence Berkeley Laboratory. The injector has produced 2.3 MV and 950 mA of K{sup +}, 15% above original design goals in energy and current. Normalized edge emittance of less than 1 {pi} mm-mr was measured over a broad range of parameters. The head-to-tail energy flatness is less than {+-} 0.2% over the 1 {micro}s pulse.
Date: April 1, 1995
Creator: Yu, S.; Eylon, S. & Henestroza, E.
Partner: UNT Libraries Government Documents Department

A high charge state heavy ion beam source for HIF

Description: A high current low emittance high charge state heavy ion beam source is being developed. This is designed to deliver HIF (heavy ion fusion) driver accelerator scale beam. Using high-charge-state beam in a driver accelerator for HIF may increase the acceleration efficiency, leading to a reduction in the driver accelerator size and cost. The proposed source system which consists of the gas beam electron stripper followed by a high charge state beam separator, can be added to existing single charge state, low emittance, high brightness ion sources and injectors. We shall report on the source physics design using 2D beam envelope simulations and experimental feasibility studies` results using a neutral gas stripper and a beam separator at the exit of the LBL 2 MV injector.
Date: April 1, 1995
Creator: Eylon, S. & Henestroza, E.
Partner: UNT Libraries Government Documents Department

Beam dynamics studies of the Heavy Ion Fusion Accelerator injector

Description: A driver-scale injector for the Heavy Ion Fusion Accelerator project has been built at LBL. This machine has exceeded the design goals of high voltage (> 2 MV), high current (> 0.8 A of K{sup +}) and low normalized emittance (< 1 {pi} mm-mr). The injector consists of a 750 keV diode pre-injector followed by an electrostatic quadrupole accelerator (ESQ) which provides strong (alternating gradient) focusing for the space-charge dominated beam and simultaneously accelerates the ions to 2 MeV. The fully 3-D PIC code WARP together with EGUN and POISSON were used to design the machine and analyze measurements of voltage, current and phase space distributions. A comparison between beam dynamics characteristics as measured for the injector and corresponding computer calculations will be presented.
Date: April 1, 1995
Creator: Henestroza, E.; Yu, S.S.; Eylon, S. & Grote, D.P.
Partner: UNT Libraries Government Documents Department

Ion sources for heavy ion fusion

Description: The development of ion sources for heavy ion fusion will be reported with particular emphasis on a recently built 2 MV injector. The new injector is based on an electrostatic quadrupole configuration, and has produced pulsed K{sup +} ions of 950 mA peak from a 6.7 inch curved alumino silicate source. The ion beam has reached 2.3 MV with an energy flatness of {+-}0.2% over 1 {micro}s. The measured normalized edge emittance of less than 1 {pi} mm-mr is close to the source temperature limit. The design, construction, performance, and comparisons with three-dimensional particle-in-cell simulations will be described.
Date: September 1, 1995
Creator: Yu, S.S.; Eylon, S. & Chupp, W.
Partner: UNT Libraries Government Documents Department

Low-emittance uniform density Cs sup + sources for heavy ion fusion accelerators studies

Description: Low-emittance (high-brightness) Cs{sup +} thermionic sources were developed for the heavy ion induction linac experiment MBE-4 at LBL. The MBE-4 linac accelerates four 10 mA beams from 200 ke V to 900 ke V while amplifying the current up to a factor of nine. Recent studies of the transverse beam dynamics suggested that characteristics of the injector geometry were contributing to the normalized transverse emissions growth. Phase-space and current density distribution measurements of the beam extracted from the injector revealed overfocusing of the outermost rays causing a hollow density profile. We shall report on the performance of a 5 mA scraped beam source (which eliminates the outermost beam rays in the diode) and on the design of an improved 10 mA source. The new source is based on EGUN calculations which indicated that a beam with good emissions and uniform current density could be obtained by modifying the cathode Pierce electrodes and using a spherical emitting surface. The measurements of the beam current density profile on a test stand were found to be in agreement with the numerical simulations. 3 refs., 6 figs.
Date: April 1, 1991
Creator: Eylon, S.; Henestroza, E.; Garvey, T.; Johnson, R. & Chupp, W.
Partner: UNT Libraries Government Documents Department

Transverse emittance studies of an induction accelerator of heavy ions

Description: Current amplification of heavy ion beams is an integral feature of the induction linac approach to heavy ion fusion. As part of the Heavy Ion Fusion Accelerator Research program at LBL we have been studying the evolution of the transverse emittance of ion beams while they are undergoing current amplification, achieved by longitudinal bunch compression and acceleration. Experiments are conducted on MBE-4, a four beam Cs{sup +} induction linac. The space-charge dominated beams of MBE-4 are focused by electrostatic quadrupoles while they are accelerated from nominally 200 keV up to {approximately} 1 MeV by 24 accelerating gaps. Initially the beams have currents of typically 4 mA to 10 mA per beam. Early experimental results showed a growth of the normalized emittance by a factor of 2 while the beam current was amplified by up to 9 times its initial value. We will discuss the results of recent experiments in which a mild bunch length compression rate, more typical of that required by a fusion driver, has shown that the normalized emittance can be maintained at its injection value (0.03 mm-mr) during acceleration. 4 refs., 4 figs., 1 tab.
Date: April 1, 1991
Creator: Garvey, T.; Eylon, S.; Fessenden, T.J.; Hahn, K. & Henestroza, E.
Partner: UNT Libraries Government Documents Department

Electrical breakdown studies with Mycalex insulators

Description: Insulating materials such as alumina and glass-bonded mica (Mycalex) are used in accelerator systems for high voltage feedthroughs, structural supports, and barriers between high voltage insulating oil and the vacuum beam pipe in induction accelerator cells. Electric fields in the triple points should be minimized to prevent voltage breakdown. Mechanical stress can compromise seals and result in oil contamination of the insulator surface. We have tested various insulator cleaning procedures including ultrasonic cleaning with a variety of aqueous-based detergents, and manual scrubbing with various detergents. Water sheeting tests were used to determine the initial results of the cleaning methods. Ultimately, voltage breakdown tests will be used to quantify the benefits of these cleaning procedures.
Date: May 1, 2003
Creator: Waldron, W.; Greenway, W.; Eylon, S.; Henestroza, E. & Yu, S.
Partner: UNT Libraries Government Documents Department

Design and construction of the 3.2 MeV high voltage column for DARHT II

Description: A 3.2 MeV injector has been designed and built for the DARHT II Project at Los Alamos Lab. The installation of the complete injector system is nearing completion at this time. The requirements for the injector are to produce a 3.2 MeV, 2000-ampere electron pulse with a flattop width of at least 2-microseconds and emittance of less than 0.15 pi cm-rad normalized. A large high voltage column has been built and installed. The column is vertically oriented, is 4.4 meters long, 1.2 meters in diameter, and weighs 5700 kilograms. A novel method of construction has been employed which utilizes bonded Mycalex insulating rings. This paper will describe the design, construction, and testing completed during construction. Mechanical aspects of the design will be emphasized.
Date: August 20, 2000
Creator: Peters, C.; Elliott, B.; Yu, S.; Eylon, S. & Henestroza, E.
Partner: UNT Libraries Government Documents Department

Longitudinal impedance measurement of an RK-TBA induction accelerating gap

Description: Induction accelerating gap designs are being studied for Relativistic Klystron Two-Beam Accelerator (RK-TBA) applications. The accelerating gap has to satisfy the following major requirements: hold-off of the applied accelerating voltage pulse, low transverse impedance to limit beam breakup, low longitudinal impedance at the beam-modulation frequency to minimize power loss. Various gap geometries, materials and novel insulating techniques were explored to optimize the gap design. We report on the experimental effort to evaluate the rf properties of the accelerating gaps in a simple pillbox cavity structure. The experimental cavity setup was designed using the AMOS, MAFIA and URMEL numerical codes. Longitudinal impedance measurements above beam-tube cut-off frequency using a single-wire measuring system are presented.
Date: May 1, 1997
Creator: Eylon, S.; Henestroza, E.; Kim, J.-S.; Houck, T.L.; Westenskow, G.A. & Yu, S.S.
Partner: UNT Libraries Government Documents Department

Time-dependent beam focusing at the DARHT-II injector diode

Description: The injector for the second axis of the Dual-Axis Radiographic Hydrotest Facility (DARHT) is being designed and constructed at LBNL. The injector consists of a single gap diode extracting 2{micro}s, 2kA, 3.2 MeV electron beam from a 6.5 inches diameter thermionic dispenser cathode. The injector is powered through a ceramic column by a Marx generator. We also investigated the possibility of extracting a beam current of 4 kA. The focusing system for the electron beam consists of a Pierce electrostatic focusing electrode at the cathode and three solenoidal focusing magnets positioned between the anode and induction accelerator input. The off-energy components (beam-head) during the 400 ns energy rise time are overfocused, leading to beam envelope mismatch and growth resulting in the possibility of beam hitting the accelerator tube walls. The anode focusing magnets can be tuned to avoid the beam spill in the 2kA case. To allow beam-head control for the 4kA case we are considering the introduction of time-varying magnetic focusing field along the accelerator axis generated by a single-loop solenoid magnet positioned in the anode beam tube. We will present the beam-head dynamics calculations as well as the solenoid design and preliminary feasibility test results.
Date: July 30, 1999
Creator: Eylon, S.; Henestroza, E.; Fawley, W. & Yu, S.
Partner: UNT Libraries Government Documents Department

High brightness potassium ion gun for the HIF neutralized transport experiment (NTX)

Description: The NTX experiment at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high perveance heavy ion beams. To focus a high intensity beam to a small spot requires a high brightness beam. In the NTX experiment, a potassium ion beam of up to 400 keV and 80 mA is generated in a Pierce type diode. At the diode exit, an aperture with variable size provides the capability to vary the beam perveance and to significantly reduce the beam emittance. We shall report on the gun characterization including current density profile, phase space distributions and the control of electrons generated by the beam scraping at the aperture. Comparison with particle simulations using the EGUN code will be presented.
Date: May 1, 2003
Creator: Eylon, S.; Henestroza, E.; Roy, P.K. & Yu, S.S.
Partner: UNT Libraries Government Documents Department

Drift compression experiments on MBE-4 and related emittance growth phenomena

Description: We have recently conducted a series of experiments on the MBE-4 heavy ion accelerator in which a velocity tilt was placed on the beam in the first accelerating section beyond the injector, followed by drift compression over the remaining 11 meters. Depending upon the magnitude of the velocity tilt and the accompanying mismatch in the focusing lattice, emittance growth was observed, manifested by butterfly'' shapes in x {minus} x{prime} phase space. We discuss various analytical limits on ion beam compression and relate them to these experiments and also to a driver for a heavy ion fusion reactor. We also present numerical simulations which investigate various aspects of compression and consequent emittance growth. 2 refs., 3 figs., 1 tab.
Date: April 1, 1991
Creator: Eylon, S.; Faltens, A.; Fawley, W.; Garvey, T.; Hahn, K.; Henestroza, E. et al.
Partner: UNT Libraries Government Documents Department

Optical Faraday Cup for Heavy Ion Beams

Description: We have been using alumina scintillators for imaging beams in heavy-ion beam fusion experiments in 2 to 4 transverse dimensions [1]. The scintillator has a limited lifetime under bombardment by the heavy ion beams. As a possible replacement for the scintillator, we are studying the technique of imaging the beam on a gas cloud. A gas cloud for imaging the beam may be created on a solid hole plate placed in the path of the beam, or by a localized gas jet. It is possible to image the beam using certain fast-quenching optical lines that closely follow beam current density and are independent of gas density. We describe this technique and show preliminary experimental data. This approach has promise to be a new fast beam current diagnostic on a nanosecond time scale.
Date: June 25, 2007
Creator: Bieniosek, Frank; Bieniosek, F.M.; Eylon, S.; Roy, P.K. & Yu, S.S.
Partner: UNT Libraries Government Documents Department

Magnetic lattice for the HIF neutralized transport experiment (NTX)

Description: The NTX experiment at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high perveance heavy ion beams. A pulsed magnetic four-quadrupole transport system for a 400 keV, 80 mA space charge dominated heavy ion beam has been designed, fabricated, tested, measured, and commissioned successfully for the Neutralized Transport Experiment (NTX). We present some generalized multipole decompositions of 3-D finite element calculations, and 2-D transient finite element simulations of eddy currents in the beam tube. Beam envelope calculations along the transport line were performed using superposition of individually 3-D calculated magnetic field maps. Revised quadrupole design parameters and features, plus fabrication and testing highlights are also presented. Magnetic field measurements were made using both Hall probes (low field DC) and inductive loop coil (high field pulsed). Magnet testing consisted of repetitive full current pulsing to determine reliability.
Date: May 1, 2003
Creator: Shuman, D.; Eylon, S.; Henestroza, E.; Roy, P.K.; Waldron, W.; Yu, S.S. et al.
Partner: UNT Libraries Government Documents Department

RK-TBA Studies at the RTA Test Facility

Description: Construction of a prototype RF power source based on the RK-TBA concept, called the RTA, has commenced at the Lawrence Berkeley National Laboratory. This prototype will be used to study physics, engineering, and costing issues involved in the application of the RK-TBA concept to linear colliders. The status of the prototype is presented, specifically the 1-MV, 1.2-kA induction electron gun and the pulsed power system that are in assembly. The RTA program theoretical effort, in addition to supporting the development of the prototype, has been studying optimization parameters for the application of the RK-TBA concept to higher-energy linear colliders. An overview of this work is presented. 1 fig.
Date: January 1, 1997
Creator: Lidia, S.; Anderson, D.; Eylon, S.; Reginato, L.; Vanecek, D.; Yu, S. et al.
Partner: UNT Libraries Government Documents Department

Stacked insulator induction accelerator gaps

Description: Stacked insulators, with alternating layers of insulating material and conducting film, have been shown to support high surface electrical field stresses. We have investigated the application of the stacked insulator technology to the design of induction accelerator modules for the Relativistic-Klystron Two-Beam Accelerator program. The rf properties of the accelerating gaps using stacked insulators, particularly the impedance at frequencies above the beam pipe cutoff frequency, are investigated. Low impedance is critical for Relativistic-Klystron Two-Beam Accelerator applications where a high current, bunched beam is trsnsported through many accelerating gaps. An induction accelerator module designs using a stacked insulator is presented.
Date: May 1997
Creator: Houck, T. I.; Westenskow, G. A.; Kim, J. S.; Eylon, S.; Henestroza, E.; Yu, S. S. et al.
Partner: UNT Libraries Government Documents Department

Design of a 1-MV induction injector for the Relativistic Klystron Two-Beam Accelerator

Description: A Relativistic Klystron Two-Beam Accelerator (RK-TBA) is envisioned as a rf power source upgrade of the Next Linear Collider. Construction of a prototype, called the RTA, based on the RK-TBA concept has commenced at the Lawrence Berkeley National Laboratory. This prototype will be used to study physics, engineering, and costing issues involved in the application of the RK-TBA concept to linear colliders. The first half of the injector, a 1 MeV, 1.2 kA, 300 ns induction electron gun, has been built and is presently being tested. The design of the injector cells and the pulsed power drive units are presented in this paper.
Date: May 1, 1997
Creator: Anderson, D.E.; Eylon, S.; Lidia, S.; Reginato, L.; Vanecek, D.; Yu, S. et al.
Partner: UNT Libraries Government Documents Department

Scaling the TBNLC collider design to higher frequencies

Description: The TBNLC collider design uses Relativistic Klystron Two-Beam Accelerator (RK-TBA) units as the rf power source for a NLC-type linac at 11.4 GHz. In this paper we report on a simple analysis using RK-TBA units as a rf power source for a CLIC-type linac at 30 GHz. The desired rf macropulse duration is less than 50 ns with a repetition rate of 600 Hz. We propose to use magnetic pulse compression units driving ferrite core induction cells for this system. Many elements of the TBNLC remain the same for a collider design at this higher frequency.
Date: August 16, 1996
Creator: Houck, T.L.; Westenskow, G.A.; Anderson, D.; Eylon, S.; Lidia, S.M.; Reginato, L.L. et al.
Partner: UNT Libraries Government Documents Department

Diagnostics for a 1.2 kA, 1 MeV electron induction injector

Description: We are constructing a 1.2-kA, 1-MeV, electron induction injector as part of the RTA program, a collaborative effort between LLNL and LBNL to develop relativistic klystrons for Two-Beam Accelerator applications. The RTA injector will also be used in the development of a high-gradient, low-emittance, electron source and beam diagnostics for the second axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility. The electron source will be a 3.5``-diameter, thermionic, flat-surface, m-type cathode with a maximum shroud field stress of approximately 165 kV/cm. Additional design parameters for the injector include a pulse length of over 150-ns flat top (1% energy variation), and a normalized edge emittance of less than 200 {pi}-mm-mr. Precise measurement of the beam parameters is required so that performance of the RTA injector can be confidently scaled to the 4-kA, 3-MeV, and 2-microsecond pulse parameters of the DARHT injector. Planned diagnostics include an isolated cathode with resistive divider for direct measurement of current emission, resistive wall and magnetic probe current monitors for measuring beam current and centroid position, capacitive probes for measuring A-K gap voltage, an energy spectrometer, and a pepper-pot emittance diagnostic. Details of the injector, beam line, and diagnostics are presented.
Date: May 11, 1998
Creator: Houck, T.L.; Anderson, D.E.; Eylon, S.; Henestroza, E.; Lidia, S.M.; Vanecek, D.L. et al.
Partner: UNT Libraries Government Documents Department

Intense heavy-ion beam transport with electric and magnetic quadrupoles

Description: As part of the small induction recirculator development at LLNL, the authors are testing an injector and transport line that delivers 4 {micro}s beams of potassium with repetition rates up to 10 Hz at a nominal current of 2 mA. The normalized K-V equivalent emittance of the beams is near 0.02 {pi} mm-mrad and is mostly determined by the temperature of the source (0.1 eV). K{sup +} ions generated at 80 keV in a Pierce diode are matched to an alternating gradient transport line by seven electric quadrupoles. Two additional quads have been modified to serve as two-axis steerers. The matching section is followed by a transport section comprised of seven permanent magnet quadrupoles. Matching to this section is achieved by adjusting the voltages on the electric quadrupoles to voltages calculated by an envelope matching code. Measurements of beam envelope parameters are made at the matching section entrance and exit as well as at the end of the permanent magnet transport section. Beam current waveforms along the experiment are compared with results from a one-dimension longitudinal dynamics code. Initial experiments show particle loss occurring at the beam head as a result of overtaking. The apparatus is also being used for the development of non or minimally intercepting diagnostics for future recirculator experiments. These include capacitive monitors for determining beam line-charge density and position in the recirculator; flying wire scanners for beam position; and gated TV scanners for measuring beam profiles and emittance.
Date: August 1, 1995
Creator: Fessenden, T. J.; Barnard, J. J.; Cable, M. D.; Deadrick, F.J.; Eylon, S.; Nelson, M. B. et al.
Partner: UNT Libraries Government Documents Department

Comparison of experimental data and 3D simulations of ion beam neutralization from the neutralized transport experiment

Description: The Neutralized Transport Experiment (NTX) at Lawrence Berkeley National Laboratory has been designed to study the final focus and neutralization of high perveance ion beams for applications in heavy ion fusion (HIF) and high energy density physics (HEDP) experiments. Pre-formed plasmas in the last meter before the target of the scaled experiment provide a source of electrons which neutralize the ion current and prevent the space-charge induced spreading of the beam spot. NTX physics issues are discussed and experimental data is analyzed and compared with 3D particle-in-cell simulations. Along with detailed target images, 4D phase-space data of the NTX at the entrance of the neutralization region has been acquired. This data is used to provide a more accurate beam distribution with which to initialize the simulation. Previous treatments have used various idealized beam distributions which lack the detailed features of the experimental ion beam images. Simulation results are compared with NTX experimental measurements for 250 keV K{sup +} ion beams with dimensionless perveance of 1-7 x 10{sup -4}. In both simulation and experiment, the deduced beam charge neutralization is close to the predicted maximum value.
Date: September 22, 2004
Creator: Thoma, C.; Welch, D.R.; Yu, S.S.; Henestroza, E.; Roy, P.K.; Eylon, S. et al.
Partner: UNT Libraries Government Documents Department

Experimental investigations of plasma lens focusing and plasma channel transport of heavy ion beams

Description: Final focusing of ion beams and propagation in a reactor chamber are crucial questions for heavy ion beam driven Fusion. An alternative solution to ballistic quadrupole focusing, as it is proposed in most reactor studies today, is the utilization of the magnetic field produced by a high current plasma discharge. This plasma lens focusing concept relaxes the requirements for low emittance and energy spread of the driver beam significantly and allows to separate the issues of focusing, which can be accomplished outside the reactor chamber, and of beam transport inside the reactor. For focusing a tapered wall-stabilized discharge is proposed, a concept successfully demonstrated at GSI, Germany. For beam transport a laser pre-ionized channel can be used.
Date: April 1, 1995
Creator: Tauschwitz, T.; Yu, S.S.; Eylon, S.; Reginato, L.; Leemans, W.; Rasmussen, J.O. et al.
Partner: UNT Libraries Government Documents Department

Beam Halo formation and loss induced by image-charge effects in a small-aperture alternating-gradient focusing system

Description: Effects of image charges on beam halo formation and beam loss in small-aperture alternating-gradient focusing systems are studied analytically, computationally, and experimentally. Nonlinear image-charge fields result in chaotic particle motion and the ejection of particles from the beam core into a halo. Detailed chaotic particle motion and structure of the particle phase space is studied, and the beam loss rate is computed for a long transport channel. Image-charge effects are also studied for a short transport channel, and compared with the Neutralized Transport Experiment (NTX) at LBNL.
Date: May 1, 2003
Creator: Zhou, J.; Qian, B.L.; Chen, C.; Henestroza, E.; Eylon, S. & S., Yu
Partner: UNT Libraries Government Documents Department