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in subjects: "Beam Emittance"  
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Scaling of current density, total current, emittance, and brightness for hydrogen negative ion sources

Description: The atomic and molecular processes that play a principal role in negative ion formation in a hydrogen negative ion discharge are discussed. The collisions of energetic electrons with gas molecules within the discharge lead to vibrationally excited molecules. Thermal electrons in turn attach to these excited molecules and generate negative ions via the dissociative attachment process. A system geometry chosen to optimize these collision processes is discussed that consists of a high-power discha… more
Date: July 10, 1986
Creator: Hiskes, J.R.
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Partner: UNT Libraries Government Documents Department
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Disruption and luminosity of flat beams

Description: It has been suggested (ref.1) that high energy linear colliders might operate with non-round beam profiles, i.e. with different sigma/sub x/ and sigma/sub y/, described by an aspect ratio R = sigma/sub y/sigma/sub x/. The advantage of flat beams is the expectation, that ''beamstrahlung'', i.e., beam-beam synchrotron radiation is reduced with increasing R. The reason for this reduction comes from the fact that for constant bunch area and therefore constant luminosity the mean physical distance b… more
Date: June 10, 1985
Creator: Hollebeek, R. & Minten, A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Characterization of the plasma-switch interaction in the LBL HIF ion source

Description: A new way to characterize the performance of the LBL HIF ion source has been found. In the LBL source, ions are drawn from an arc-generated plasma reservoir in which the electrons are confined by a negative-biased switch'' mesh. Stagnation of the plasma is prevented by absorption of the excess ion flow on this mesh. The ion beam is generated by an external negative voltage that provides Child-Langmuir extraction of the ions through the switch mesh. We elucidate the physics requirements of the s… more
Date: December 10, 1990
Creator: Hewett, D.W. (Lawrence Livermore National Lab., CA (USA)) & Rutkowski, H.L. (Lawrence Berkeley Lab., CA (USA))
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Partner: UNT Libraries Government Documents Department
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Injection of large transverse emittance EBIS beams in booster

Description: During the commissioning of EBIS beams in Booster in November 2010 and in April, May and June 2011, it was found that the transverse emittances of the EBIS beams just upstream of Booster were much larger than expected. Beam emittances of 11{pi} mm milliradians had been expected, but numbers 3 to 4 times larger were measured. Here and throughout this note the beam emittance, {pi}{epsilon}{sub 0}, is taken to be the area of the smallest ellipse that contains 95% of the beam. We call this smallest… more
Date: October 10, 2011
Creator: Gardner, C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Correction of longitudinal errors in accelerators for heavy-ion fusion

Description: Longitudinal space-charge waves develop on heavy-ion inertial-fusion pulse from initial mismatches or from inappropriately timed or shaped accelerating voltages. Without correction, waves moving backward along the beam can grow due to the interaction with their resistively retarded image fields, eventually degrading the longitudinal emittance. A simple correction algorithm is presented here that uses a time-dependent axial electric field to reverse the direction of backward-moving waves. The im… more
Date: June 10, 1993
Creator: Sharp, W. M.; Callahan, D. A.; Barnard, J. J.; Langdon, A. B. & Fessenden, T. J.
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Partner: UNT Libraries Government Documents Department
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2-MV electrostatic quadrupole injector for heavy-ion fusion

Description: High current and low emittance are principal requirements for heavy-ion injection into a linac driver for inertial fusion energy. An electrostatic quadrupole (ESQ) injector is capable of providing these high charge density and low emittance beams. We have modified the existing 2-MV Injector to reduce beam emittance and to double the pulse length. We characterize the beam delivered by the modified injector to the High Current Transport Experiment (HCX) and the effects of finite rise time of the … more
Date: November 10, 2004
Creator: Bieniosek, F. M.; Celata, C. M.; Henestroza, E.; Kwan, J. W.; Prost, L. & Seidl, P. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Recent Flash X-Ray Injector Modeling

Description: The injector of the Flash X-Ray (FXR) accelerator has a significantly larger than expected beam emittance. A computer modeling effort involving three different injector design codes was undertaken to characterize the FXR injector and determine the cause of the large emittance. There were some variations between the codes, but in general the simulations were consistent and pointed towards a much smaller normalized, rms emittance (36 cm-mr) than what was measured (193 cm-mr) at the exit of the in… more
Date: November 10, 2004
Creator: Houck, T.; Blackfield, D.; Burke, J.; Chen, Y.; Javedani, J. & Paul, A. C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Physics Design Considerations for Diagnostic X Electron Beam Transport System

Description: The Diagnostic X (D-X) beamlines will transport the DARHT-II beam from the end of the accelerator to the Diagnostic X firing point providing four lines of sight for x-ray radiography. The design goal for the Diagnostic X beamline is to deliver four x-ray pulses with the DARHT-II dose format and time integrated spot size on each line of sight. The D-X beamline's final focus should be compatible with a range of first conjugates from 1 m-5 m. Furthermore, the D-X beamline operational parameters an… more
Date: April 10, 2000
Creator: Chen, Y. J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Overview of Virtual National Labratory Objectives, Plans, and Projects

Description: Significant experimental and theoretical progress has been made in the U.S. heavy ion fusion program on high-current sources, transport, and focusing. Currents over 200 mA have been transported through a matching section and 10 half-lattice periods with electric quadrupoles. An experiment shows control of high beam current with an aperture, while avoiding secondary electrons. New theory and simulations of the neutralization of intense beam space charge with plasma in various focusing chamber co… more
Date: May 10, 2004
Creator: Logan, B.; Celata, C.; Kwan, J.; Lee, E.; Leitner, M.; Seidl, P. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Demonstration of ultraviolet lasing with a low energy electron beam

Description: We report on the design details of the first ultraviolet (UV) free-electron laser (FEL) oscillator driven by low-energy electrons from a radio-frequency linear accelerator. In our experiment we used a high-current, high brightness electon beam in combination with a wiggler of novel design to produce an FEL that lased at wavelengths from 369--380 nm using 45.9--45.2 MeV electrons. In addition we performed a proof-of principle experiment that demonstrated the first ever photolithography on a phot… more
Date: August 10, 1993
Creator: O`Shea, P. G.; Bender, S. C. & Byrd, D. A.
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Partner: UNT Libraries Government Documents Department
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Optimization of Beam Injection into the First Accelerating Module at TTF With Cavity Dipole Mode Signals

Description: The TESLA Test Facility (TTF) is a user facility for intense VUV-FEL light. The facility is densely equipped with diagnostics, essential in obtaining the necessary beam parameters, in particular the low emittance. However there is no dedicated component for alignment of the beam in the accelerating modules, each containing eight superconducting cavities. Large beam offsets can lead to an increase of the beam emittance. The centering of the beam in these modules is therefore important, mostly at… more
Date: April 10, 2006
Creator: Baboi, N.; Kreps, G.; Schlarb, H.; Wendt, M.; Frisch, J.; McCormick, D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Emittance measurements at the A0 photo-injector

Description: The A0 photo-injector produces electron bunches of 1--14 nC charge with an energy of 18 MeV. Detailed measurements and optimization of emittance have been carried out for a number of gun and laser operating conditions, beam line optics conditions, and at a number of beam line locations. Results are compared with the predictions of simulations using HOMDYN.
Date: October 10, 2000
Creator: Carneiro, Jean-Paul
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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