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A method for measuring dark current electron beams in an rf linac

Description: X-ray fluorescence from thin foils inserted into the NPS linac has been used to measure the integrated electron beam intensity when the accelerator is operating with dark current. The measured x-ray flux, the known inner shell ionization cross sections and radiative transition probabilities are used to obtain measurements of dark currents of the order of 10{sup -14} amperes. The same arrangement allows continuous, in-situ energy calibration of our SiLi detector in the electromagnetic noise environment of the linac. This technique was orginally developed to perform absolute production efficiency measurements of parametric x-ray generation in the 5-50 keV range.
Date: December 31, 1993
Creator: Maruyama, X. K.; Fasanello, T.; Rietdyk, H.; Piestrup, M. A.; Rule, D. W. & Fiorito, R. B.
Partner: UNT Libraries Government Documents Department

Improved ETA-II accelerator performance

Description: Improvements have been made in the performance of the ETA-II accelerator that allow a nominal 2 kA, 6 MeV beam to be focused to a spot size less that 1 mm in diameter. The improvements include reducing the energy sweep to less than +/- 0.5 & over 40 ns of the pulse using a real time energy diagnostic and improving the magnetic tune of the accelerator to reduce the emittance to 8 cm-mrad. Finally, an automated tuning system (MAESTRO) was run to minimize the time dependent centroid motion (corkscrew) by adjusting the steering dipoles over the focusing solenoids. The corkscrew motion was reduced to less than +/- 0.5 mm at the output of the accelerator.
Date: March 22, 1999
Creator: Paul, A C; Boyd, J K; Chen, Y J; Clark, J C; Lager, D L & Weir, J T
Partner: UNT Libraries Government Documents Department

Generation of Femtosecond X-Rays by 90 degrees Compton Scattering

Description: We propose Compton scattering of a short pulse visible laser beam by a low energy (but relativistic) electron beam at a right angle for generation of femtosecond x-rays. Simple analysis to determine the qualitative and quantitative characteristics of the x-ray pulse is presented.
Date: December 1, 1992
Creator: Kim, K.-J.; Chattopadhyay, S. & Shank, C.V.
Partner: UNT Libraries Government Documents Department

Volumetric plasma source development and characterization.

Description: The development of plasma sources with densities and temperatures in the 10{sup 15}-10{sup 17} cm{sup -3} and 1-10eV ranges which are slowly varying over several hundreds of nanoseconds within several cubic centimeter volumes is of interest for applications such as intense electron beam focusing as part of the x-ray radiography program. In particular, theoretical work [1,2] suggests that replacing neutral gas in electron beam focusing cells with highly conductive, pre-ionized plasma increases the time-averaged e-beam intensity on target, resulting in brighter x-ray sources. This LDRD project was an attempt to generate such a plasma source from fine metal wires. A high voltage (20-60kV), high current (12-45kA) capacitive discharge was sent through a 100 {micro}m diameter aluminum wire forming a plasma. The plasma's expansion was measured in time and space using spectroscopic techniques. Lineshapes and intensities from various plasma species were used to determine electron and ion densities and temperatures. Electron densities from the mid-10{sup 15} to mid-10{sup 16} cm{sup -3} were generated with corresponding electron temperatures of between 1 and 10eV. These parameters were measured at distances of up to 1.85 cm from the wire surface at times in excess of 1 {micro}s from the initial wire breakdown event. In addition, a hydrocarbon plasma from surface contaminants on the wire was also measured. Control of these contaminants by judicious choice of wire material, size, and/or surface coating allows for the ability to generate plasmas with similar density and temperature to those given above, but with lower atomic masses.
Date: September 1, 2008
Creator: Crain, Marlon D. (National Security Technologies, LLC, Las Vegas, NV); Maron, Yitzhak (Weizmann Institute of Science, Rehovot, Israel); Oliver, Bryan Velten; Starbird, Robert L. (National Security Technologies, LLC, Las Vegas, NV); Johnston, Mark D.; Hahn, Kelly Denise et al.
Partner: UNT Libraries Government Documents Department

All-Optical Laser-Wakefield Electron Injector

Description: Demonstrated the principle of optical control of laser accelerators, namely, that one laser pulse could modify the properties (e.g., emittance and electron number) of an electron beam accelerated by a separate but synchronized laser pulse. Another recent highlight was that, using our new 30-fs 10-TW laser system, we accelerated with a laser accelerator an electron beam with a record low divergence (0.2 degrees). This is more than 100 times lower than the 30-degree divergence that was reported recently by a French group using a laser with similar parameters.
Date: July 1, 2003
Creator: Umstadter, Donald P.
Partner: UNT Libraries Government Documents Department

High power electron beam dumps at CEBAF

Description: The CEBAF accelerator produces a very small emittance CW electron beam of up to 200 {mu}A average current. The resulting beam power, up to 1 MW at 5 GeV, and the very high beam power density, pose challenging problems for beam dump design. Two styles of high power dumps have been developed. The first, rated for 100+ kW, is used for beam tune-up and accelerator commissioning. The beam power is entirely contained in metal in this dump, minimizing the problems associated with radioactive water handling. Full power 1 MW dumps are used with the experimental halls. In these dumps, one-third of the beam power is directly absorbed in water. Both dump designs require the beam to be rastered when the smallest beam sizes are used. Design details for each of these dumps will be presented.
Date: June 1, 1997
Creator: Wiseman, M.; Sinclair, C.K.; Whitney, R. & Zarecky, M.
Partner: UNT Libraries Government Documents Department

Beam-Beam Compensation Activities at Fermilab. R&D Status.

Description: The beam-beam interaction in the Tevatron produces the betatron tune spread in each bunch and a bunch-to-bunch tune spread. The tune spread sets limits on bunch intensity and luminosity. The beam-beam e#11;ects for antiprotons are usually more severe since the proton bunch population is higher. The beam-beam e#11;ects for antiprotons can in principle be compensated with the use of an electron beam with a corresponding charge density. The status of studies of possibilities of the beam-beam compensation is reviewed in this paper.
Date: February 5, 1999
Creator: Sery, Andrey; Danilov, Slava; Finley, Dave & Shiltsev, Vladimir
Partner: UNT Libraries Government Documents Department

Pencil-like mm-size electron beams produced with linear inductive voltage adders (LIVA)

Description: This paper presents design, analysis, and first results of the high brightness electron beam experiments currently under investigation at Sandia. Anticipated beam parameters are: energy 12 MeV, current 35-40 kA, rms radius 0.5 mm, pulse duration 40 ns FWHM. The accelerator is SABRE, a pulsed LIVA modified to higher impedance, and the electron source is a magnetically immersed foilless electron diode. 20 to 30 Tesla solenoidal magnets are required to insulate the diode and contain the beam to its extremely small sized (1 mm) envelope. These experiments are designed to push the technology to produce the highest possible electron current in a submillimeter radius beam. Design, numercial simulations, and first experimental results are presented.
Date: September 1, 1996
Creator: Mazarakis, M.G.; Poukey, J.W. & Rovang, D.C.
Partner: UNT Libraries Government Documents Department

Performance of the transverse coupled-bunch feedback system in the SRRC

Description: A transverse feedback system has been implemented and commissioned in the SRRC storage ring to suppress transverse coupled-bunch oscillations of the electron beam. The system includes transverse oscillation detectors, notch filter, baseband quadrature processing circuitry, power amplifiers, and kickers. To control a large number of transverse coupled-bunch modes, the system is broad-band, bunch-by- bunch in nature. Because the system is capable of bunch-by-bunch correction, it can also be useful for suppressing instabilities introduced by ions. The sextupole strength was then reduced to improve dynamic aperture and hence lifetime of the storage ring.
Date: October 1, 1996
Creator: Hsu, K.T.; Kuo, C.C.; Kuo, C.H.; Lin, K.K.; Ueng, T.S. & Weng, W.T.
Partner: UNT Libraries Government Documents Department

Development of a high intensity EBIT for basic and applied science/011

Description: The electron-beam ion trap (EBIT) is a device for producing and studying cold, very highly charged ions of any element, up to a fully ionized U{sup 92+}. These highly charged ions occur in hot plasmas and therefore play important roles in nuclear weapons, controlled fusion, and astrophysical phenomena. The remarkable interaction of these ions with surfaces may lead to technological applications. The highly charged ions can either be studied inside the EBIT itself with measurements of their x-ray emission spectra, or the ions can be extracted from the EBIT in order to study their interaction with solid material. Both types of measurements are being pursued vigorously with the two existing low-intensity EBITs at LLNL and with similar EBITs that have been built at six other laboratories around the world since the EBIT was first developed at LLNL 10 years ago. However, all existing EBITs have approximately the same intensity as the original LLNL EBIT; that is, they all produce about the same number of very-highly-charged ions (roughly 2 x 10{sup 6} per second) and the same number of x-ray photons (roughly 10{sup 7} per second). The goal of the High-Intensity-EBIT project is to increase the x-ray emission per centimeter of length along the electron beam by a factor of 100 and to increase the ion output by a factor of 1000. This dramatic increase in intensity will enable the next generation of basic and applied experimental research in the structure of highly charged ions. For example, the precision of EBIT x-ray measurements of atomic energy levels- which is now limited by count rate-can be improved by an order of magnitude, and new applications in surface science, nanotechnology, and microscopy will be possible with the expected intense ion beams. When the high ion output is combined with the demonstrated low emittance ...
Date: February 5, 1998
Creator: Marrs, R. E.
Partner: UNT Libraries Government Documents Department

``Electron Lens`` to Compensate Bunch-to-Bunch Tune Spread in TEV33

Description: In this article we discuss an electron beam lens for compensation of bunch-to-bunch tune spread in the Tevatron antiproton beam. Time-modulated current of an electron beam can produce defocusing forces necessary to compensate effects caused by parasitic beam-beam interactions with proton beam. We estimate maim parameters of the electron beam and consider resulting beam footprint. Emittance growth rate due to the electron current fluctuations is discussed.
Date: October 1, 1997
Creator: Shiltsev, V.
Partner: UNT Libraries Government Documents Department

Automated path length and M{sub 56} measurements at Jefferson Lab

Description: Accurate measurement of path length and path length changes versus momentum (M{sub 56}) are critical for maintaining minimum beam energy spread in the CEBAF (Continuous Electron Beam Accelerator Facility) accelerator at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). The relative path length for each circuit of the beam (1,256m) must be equal within 1.5 degrees of 1497 MHz RF phase. A relative path length measurement is made by measuring the relative phases of RF signals from a cavity that is separately excited for each pass of a 4.2 {micro}s pulsed beam. This method distinguishes the path length to less than 0.5 path length error. The development of a VME based automated measurement system for path length and M{sub 56} has contributed to faster machine setup time and has the potential for use as a feedback parameter for automated control.
Date: August 1, 1997
Creator: Hardy, D.; Tang, J.; Legg, R.; Tiefenback, M.; Crofford, M. & Krafft, G.A.
Partner: UNT Libraries Government Documents Department

An insertion to eliminate horizontal temperature of high energy electron beam

Description: High energy electron cooling with a circulated electron bunch could significantly increase the luminosity of hadron colliders. One of the significant obstacles is high horizontal temperature of electron bunches, suppressing dramatically calculated cooling rates. Recently, a transformation of betatron coordinates and angles for elimination of the radial temperature was found. In our paper, we present a simple scheme to make up this transformation by thin quadruples, drifts and a solenoid.
Date: March 16, 1998
Creator: Burov, A.V. & Danilov, V.V.
Partner: UNT Libraries Government Documents Department

Transmission line analysis of beam deflection in a BPM stripline kicker

Description: In the usual treatment of impedances of beamline structures the electromagnetic response is computed under the assumption that the source charge trajectory is parallel to the propagation axis and is unaffected by the wake of the structure. For high energy beams of relatively low current this is generally a valid assumption. Under certain conditions the assumption of a parallel source charge trajectory is no longer valid and the effects of the changing trajectory must be included in the analysis. Here the usual transmission line analysis that has been applied to BPM type transverse kickers is extended to include the self-consistent motion of the beam in the structure.
Date: May 1, 1997
Creator: Caporaso, G.J.; Chen, Yu Ju & Poole, B.
Partner: UNT Libraries Government Documents Department

Fixed-Target Electron Accelerators

Description: A tremendous amount of scientific insight has been garnered over the past half-century by using particle accelerators to study physical systems of sub-atomic dimensions. These giant instruments begin with particles at rest, then greatly increase their energy of motion, forming a narrow trajectory or beam of particles. In fixed-target accelerators, the particle beam impacts upon a stationary sample or target which contains or produces the sub-atomic system being studied. This is in distinction to colliders, where two beams are produced and are steered into each other so that their constituent particles can collide. The acceleration process always relies on the particle being accelerated having an electric charge; however, both the details of producing the beam and the classes of scientific investigations possible vary widely with the specific type of particle being accelerated. This article discusses fixed-target accelerators which produce beams of electrons, the lightest charged particle. As detailed in the report, the beam energy has a close connection with the size of the physical system studied. Here a useful unit of energy is a GeV, i.e., a giga electron-volt. (ne GeV, the energy an electron would have if accelerated through a billion volts, is equal to 1.6 x 10{sup -10} joules.) To study systems on a distance scale much smaller than an atomic nucleus requires beam energies ranging from a few GeV up to hundreds of GeV and more.
Date: November 2001
Creator: Brooks, William K.
Partner: UNT Libraries Government Documents Department