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Proposal for a High-Brightness Pulsed Electron Source

Description: We propose a novel scheme for a high-brightness pulsedelectron source, which has the potential for many useful applications inelectron microscopy, inverse photo-emission, low energy electronscattering experiments, and electron holography. A description of theproposed scheme is presented.
Date: March 15, 2006
Creator: Zolotorev, Max; Commins, Eugene D.; Heifets, Sam & Sannibale,Fernando
Partner: UNT Libraries Government Documents Department

Particle-In-Cell/Monte Carlo Simulation of Ion Back Bombardment in Photoinjectors

Description: In this paper, we report on studies of ion back bombardment in high average current dc and rf photoinjectors using a particle-in-cell/Monte Carlo method. Using H{sub 2} ion as an example, we observed that the ion density and energy deposition on the photocathode in rf guns are order of magnitude lower than that in a dc gun. A higher rf frequency helps mitigate the ion back bombardment of the cathode in rf guns.
Date: March 2, 2009
Creator: Qiang, Ji; Corlett, John & Staples, John
Partner: UNT Libraries Government Documents Department

SPEAR III: A brighter source at SSRL

Description: By replacing the magnets and vacuum chamber for the 3 GeV SPEAR II storage ring, the natural emittance of the machine can be reduced from 130 to 18 nm-rad and the stored current can be raised from 100 to 200 mA with a 50 h lifetime. This configuration increases focused photon flux for insertion device beamlines by an order of magnitude and the photon brightness for future undulators would exceed 10{sup 18} at 5 keV. Due to a higher critical energy, the photon flux in the 20 keV range for bending magnet beamlines increases by more than two orders of magnitude. We present preliminary SPEAR III design study results and plans to implement the facility upgrade with minimal downtime for SSRL users.
Date: June 2, 1997
Creator: Hettel, R.; Boyce, R. & Brennan, S.
Partner: UNT Libraries Government Documents Department

Microwave Radiometer – 3 Channel (MWR3C) Handbook

Description: The microwave radiometer 3-channel (MWR3C) provides time-series measurements of brightness temperatures from three channels centered at 23.834, 30, and 89 GHz. These three channels are sensitive to the presence of liquid water and precipitable water vapor.
Date: May 4, 2012
Creator: Cadeddu, MP
Partner: UNT Libraries Government Documents Department

Achieving Stability Requirements for Nanoprobe and Long Beam Lines at NSLS II. A Comprehensive Study

Description: Driven by beam stability requirements at the NSLS II synchrotron, such that the desired small beam sizes and high brightness are both realized and stable, a comprehensive study has been launched seeking to provide assurances that stability at the nanometer level at critical x-ray beam-lines, is achievable, given the natural and cultural vibration environment at the selected site. The study consists of (a) an extensive investigation of the site to evaluate the existing ground vibration, in terms of amplitude, frequency content and coherence, and (b) of a numerical study of wave propagation and interaction with the infrastructure of the sensitive lines. The paper presents results from both aspects of the study.
Date: June 23, 2008
Creator: Simos,N.; Fallier, M.; Hill, J.; Berman, L.; Evans-Lutterodt, K. & Broadbent, A.
Partner: UNT Libraries Government Documents Department

FIRST EXPERIMENTAL RESULTS FROM DEGAS, THE QUANTUM LIMITED BRIGHTNESS ELECTRON SOURCE

Description: The construction of DEGAS (DEGenerate Advanced Source), a proof of principle for a quantum limited brightness electron source, has been completed at the Lawrence Berkeley National Laboratory. The commissioning and the characterization of this source, designed to generate coherent single electron 'bunches' with brightness approaching the quantum limit at a repetition rate of few MHz, has been started. In this paper the first experimental results are described.
Date: June 23, 2008
Creator: Zolotorev, Max S.; Commins, Eugene D.; Oneill, James; Sannibale, Fernando; Tremsin, Anton & Wan, Weishi
Partner: UNT Libraries Government Documents Department

Ultrabright Laser-based MeV-class Light Source

Description: We report first light from a novel, new source of 10-ps 0.776-MeV gamma-ray pulses known as T-REX (Thomson-Radiated Extreme X-rays). The MeV-class radiation produced by TREX is unique in the world with respect to its brightness, spectral purity, tunability, pulse duration and laser-like beam character. With T-REX, one can use photons to efficiently probe and excite the isotope-dependent resonant structure of atomic nucleus. This ability will be enabling to an entirely new class of isotope-specific, high resolution imaging and detection capabilities.
Date: April 2, 2008
Creator: Albert, F; Anderson, G; Anderson, S; Bayramian, A; Berry, B; Betts, S et al.
Partner: UNT Libraries Government Documents Department

ANALYSIS OF THE MAGNETIZED FRICTION FORCE.

Description: A comprehensive examination of theoretical models for the friction force, in use by the electron cooling community, was performed. Here, they present their insights about the models gained as a result of comparison between the friction force formulas and direct numerical simulations, as well as studies of the cooling process as a whole.
Date: May 29, 2006
Creator: FEDOTOV, A.V.; BRUHWILER, D.L. & SIDORIN, A.O.
Partner: UNT Libraries Government Documents Department

The polarized SRF gun experiment

Description: An experiment is under way to prove the feasibility of a super-conducting RF gun for the production of polarized electrons. We report on the progress of the experiment and on simulations predicting the possibility of success.
Date: October 1, 2008
Creator: Kewisch,J.; Ben-Zvi, I.; Rao, T.; Burrill, A.; Pate, D.; Todd, R. et al.
Partner: UNT Libraries Government Documents Department

What ignites optical jets?

Description: The properties of radio galaxies and quasars with and without optical or X-ray jets are compared. The majority of jets from which high-frequency emission has been detected so far (13 with optical emission, 11 with X-rays, 13 with both) are associated with the most powerful radio sources at any given redshift. It is found that optical/X-ray jet sources are more strongly beamed than the average population of extragalactic radio sources. This suggests that the detection or non-detection of optical emission from jets has so far been dominated by surface brightness selection effects, not by jet physics. It implies that optical jets are much more common than is currently appreciated.
Date: December 23, 2002
Creator: Jester, Sebastian
Partner: UNT Libraries Government Documents Department

ADVANCED DIAGNOSTICS FOR DEVELOPING HIGH-BRIGHTNESS ELECTRON BEAMS.

Description: The production of high-brightness particle beams calls for the development of advanced beam diagnostics. High brightness beams, meaning beams with a high density in phase space, are important for many applications, such as short-wavelength Free-Electron Lasers and advanced accelerator systems. A diagnostic that provides detailed information on the density distribution of the electron bunch in multi-dimensional phase-space is an essential tool for obtaining small emittance at a high charge. This diagnostic system has been developed at Brookhaven National Laboratory. One component of the system is the measurement of a slice emittance which provides a measurement of transverse beam properties (such as emittance) as a function of the longitudinal position. Changing the laser pulse profile of a photocathode RF gun has been suggested as one way to achieve non-linear emittance compensation and improve the brightness and that can be diagnosed by the slice emittance system. The other element of the diagnostic is the tomographic reconstruction of the transverse phase. In our work we give special attention to the accuracy of the phase space reconstruction and present an analysis using a transport line with nine focusing magnets and techniques to control the optical functions and phases. This high precision phase space tomography together with the ability to modify the radial charge distribution of the electron beam presents an opportunity to improve the emittance and apply non-linear radial emittance corrections. Combining the slice emittance and tomography diagnostics leads to an unprecedented visualization of phase space distributions in 5 dimensional phase-space and an opportunity to perform high-order emittance corrections. This should lead to great improvements in the beam brightness.
Date: November 24, 1998
Creator: BEN-ZVI,I.
Partner: UNT Libraries Government Documents Department

Beam lifetime and beam brightness in ALS

Description: Beam lifetime in ALS is dominated by the Touschek scattering. Measurements of lifetime in single-bunch mode with estimates of bunch dimensions obtained from undulator radiation data are consistent with expectations (t=1.8 hours at 1.25 mA per bunch). However, the lifetime is significantly longer in multi-bunch mode (t=ll hours at 400 mA per 320 bunches). This discrepancy has been traced to an increase in the momentum spread and bunch length in the beam caused by longitudinal coupled-bunch motions driven by higher-order modes in the rf cavities. The increased momentum spread leads to a significant degradation in the undulator spectral performance. Feedback stabilization of the coupled-bunch motion improves the spectral characteristics of the undulator beam at the expense of beam lifetime. We observe an increase of {approximately}200% in beam lifetime by operating at the betatron coupling resonance.
Date: April 1, 1995
Creator: Kim, C.; Jackson, A. & Warwick, A.
Partner: UNT Libraries Government Documents Department

Summary of the ECLOUD'04 Workshop

Description: The 31st ICFA Advanced Beam Dynamics Workshop on Electron-Cloud Effects ''ECLOUD'04'' was held April 19-23, 2004 at Napa, CA, USA. A broad range of current topics in this field were illuminated by 53 talks in 7 sessions plus 6 session summaries at the final summary session. These covered a variety of experimental methods and results, along with progress on understanding of the topic obtained from simulations and analytic theory, and evaluations of the effectiveness of various methods/mechanisms for mitigation of the adverse impact on accelerator performance. In addition, a panel discussion was held on ''Future Needs and Future Directions''. A summary of progress on the major themes covered at ECLOUD'04 is presented.
Date: November 30, 2004
Creator: Macek, R. & Furman, M.
Partner: UNT Libraries Government Documents Department

ADDITIONAL QUADRUPOLES AT CENTER OF LONG STRAIGHTS IN THE NSLS-II LATTICE

Description: The NSLS-II storage ring lattice is comprised of 30 DBA cells arranged in 15 superperiods. There are 15 long straight sections (9.3m) for injection, RF and insertion devices and 15 shorter straights (6.6m) for insertion devices. In the baseline lattice, the short straights have small horizontal and vertical beta functions but the long straights have large horizontal beta function optimized for injection. In this paper, we explore the possibility of installing additional quadrupoles at the center of selected long straight sections in order to provide two low-beta source locations for undulators in the same straight. The required modification to the linear lattice is discussed as well as the preservation of adequate dynamic aperture required for good injection efficiency and adequate Touschek lifetime. This paper discusses the possibility of producing two low-beta source locations for optimum brightness of undulators in the long straights of NSLS-II lattice by installing additional quadrupoles at the center. The linear optics is optimized to satisfy the requirements of lattice function and properties. Nonlinear optimization for a lattice with working point at (37.16, 17.22) is performed. Considering the magnets misalignment errors and physical apertures, we calculate the frequency maps and plot the tune footprint. The results show that the modified high-low beta function lattice can achieve a modest dynamic aperture in this preliminary study. Further work will continue to expand the dynamic aperture to meet the requirement of good injection efficiency and sufficient Touschek lifetime.
Date: March 28, 2011
Creator: Lin, F.; Bengtsson, J.; Guo, W.; Krinsky, S.; Li, Y. & Yang, L.
Partner: UNT Libraries Government Documents Department

Sliding Mode Pulsed Averaging IC Drivers for High Brightness Light Emitting Diodes

Description: This project developed new Light Emitting Diode (LED) driver ICs associated with specific (uniquely operated) switching power supplies that optimize performance for High Brightness LEDs (HB-LEDs). The drivers utilize a digital control core with a newly developed nonlinear, hysteretic/sliding mode controller with mixed-signal processing. The drivers are flexible enough to allow both traditional microprocessor interface as well as other options such as “on the fly” adjustment of color and brightness. Some other unique features of the newly developed drivers include • AC Power Factor Correction; • High power efficiency; • Substantially fewer external components should be required, leading to substantial reduction of Bill of Materials (BOM). Thus, the LED drivers developed in this research : optimize LED performance by increasing power efficiency and power factor. Perhaps more remarkably, the LED drivers provide this improved performance at substantially reduced costs compared to the present LED power electronic driver circuits. Since one of the barriers to market penetration for HB-LEDs (in particular “white” light LEDs) is cost/lumen, this research makes important contributions in helping the advancement of SSL consumer acceptance and usage.
Date: August 17, 2006
Creator: Dr. Anatoly Shteynberg, PhD
Partner: UNT Libraries Government Documents Department

An Ultra-Bright Pulsed Electron Beam with Low Longitudinal Emittance

Description: Most existing electron sources extract electrons from conductors. Since the actual temperature inside the conductor is much less than the Fermi temperature of the conduction electrons, the electron degeneracy ({delta}{sub f}) is close to 1, the maximum allowed by the Pauli exclusion principle. However, during extraction several factors conspire together to reduce {delta}{sub f} many orders of magnitude, limiting the achieved values to approx 10{sup -5}. A new concept is described for building a novel electron source designed to produce a pulsed beam with {delta}{sub f} approx 2 10{sup -3} and longitudinal emittance four orders of magnitude smaller than currently achieved values. This high brightness, low longitudinal emittance regime enables a wide range of novel applications that utilize angstrom-scale spatial resolution and eV-scale energy resolution. The current state of a proof-of-principle experiment conducted at LBNL is also described.
Date: May 1, 2005
Creator: Zolotorev, Max; Commins, Eugene D.; Denes, P.; Heifets, Samuel; Hussain, Zahid; Lebedev, Gennnadi V. et al.
Partner: UNT Libraries Government Documents Department

Automatic segmentation of histological structures in normal and neoplastic mammary gland tissue sections

Description: In this paper we present a scheme for real time segmentation of histological structures in microscopic images of normal and neoplastic mammary gland sections. Paraffin embedded or frozen tissue blocks are sliced, and sections are stained with hematoxylin and eosin (H&E). The sections are then imaged using conventional bright field microscopy. The background of the images is corrected by arithmetic manipulation using a ''phantom.'' Then we use the fast marching method with a speed function that depends on the brightness gradient of the image to obtain a preliminary approximation to the boundaries of the structures of interest within a region of interest (ROI) of the entire section manually selected by the user. We use the result of the fast marching method as the initial condition for the level set motion equation. We run this last method for a few steps and obtain the final result of the segmentation. These results can be connected from section to section to build a three-dimensional reconstruction of the entire tissue block that we are studying.
Date: January 18, 2003
Creator: Fernandez-Gonzalez, Rodrigo; Deschamps, Thomas; Idica, Adam K.; Malladi, Ravi & Ortiz de Solorzano, Carlos
Partner: UNT Libraries Government Documents Department

LOW HORIZONTAL BETA FUNCTION IN LONG STRAIGHTS OF THE NSLS-II LATTICE

Description: The NSLS-II storage ring lattice is comprised of 30 DBA cells arranged in 15 superperiods. There are 15 long straight sections (9.3m) for injection, RF and insertion devices and 15 short straights (6.6m) for insertion devices. In the baseline lattice, the short straights have small horizontal and vertical beta functions but the long straights have large horizontal beta function optimized for injection. In this paper, we explore the possibility of maintaining three long straights with large horizontal beta function while providing the other 12 long straights with smaller horizontal beta function to optimize the brightness of insertion devices. Our study considers the possible linear lattice solutions as well as characterizing the nonlinear dynamics. Results are reported on optimization of dynamic aperture required for good injection efficiency and adequate Touschek lifetime. This paper discusses dynamic aperture optimization for the NSLS-II lattice with alternate high and low horizontal beta function in the long straights, which is proposed for the optimization of the brightness of insertion devices. The linear optics is optimized to meet the requirements of lattice function and source properties. Nonlinear optimization for a lattice with working point at (37.18, 16.2) is performed. Considering the realistic magnets errors and physical apertures, we calculate the frequency maps and plot the tune footprint. The results show that the lattice with high-low beta function has adequate dynamic aperture for good injection efficiency and sufficient Touschek lifetime.
Date: March 28, 2011
Creator: Fanglei, L.; Bengtsson, J.; Guo, W.; Krinsky, S.; Li, Y. & Yang, L.
Partner: UNT Libraries Government Documents Department

Theory and proposal for a quantum-degenerate electron source

Description: We propose a pulsed electron source capable of a 6Dbrightness orders-of-magnitude greater than that of existing sources. Itcould deliver average current up to 0.5 pA and achieve an emittanceapproaching the quantum limit of one Compton wavelength in each spatialdimension. It could be employed to advantage in electron microscopy,inverse photo-emission, precision low-energy scattering experiments, andelectron holography. This source could make possible pump-probeexperiments with Angstrom spatial and sub-picosecond time resolution.Here we describe basic concepts of the source, including analysis of mainissues that must be addressed for its successful construction andoperation. We have begun an experiment to demonstrate its essentialfeatures.
Date: September 11, 2006
Creator: Zolotorev, Max; Commins, Eugene D. & Fernando, Sannibale
Partner: UNT Libraries Government Documents Department