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An algorithm to calculate the beam momentum distribution from flying wire profiles

Description: Horizontal flying wire measurements give beam profiles from which information about the beam momentum distribution and betatron distribution can be extracted. When calculating these beam characteristics in the past, for the matter of simplicity, the beam has been assumed Gaussian. For beam profiles which may not be Gaussian, an algorithm to obtain the general beam momentum distribution is developed using the Fourier transform to the beam profiles. Since the profile is the convolution of the momentum distribution and the betatron distribution, using a Fourier transform method makes calculations easier. 6 figs.
Date: July 27, 1989
Creator: Wang, X.Q.
Partner: UNT Libraries Government Documents Department

Ultrafast, high precision gated integrator

Description: An ultrafast, high precision gated integrator has been developed by introducing new design approaches that overcome the problems associated with earlier gated integrator circuits. The very high speed is evidenced by the output settling time of less than 50 ns and 20 MHz input pulse rate. The very high precision is demonstrated by the total output offset error of less than 0.2mV and the output droop rate of less than 10{mu}V/{mu}s. This paper describes the theory of this new gated integrator circuit operation. The completed circuit test results are presented.
Date: January 1, 1995
Creator: Wang, X.
Partner: UNT Libraries Government Documents Department


Description: In modeling gas-liquid two-phase flows, the concept of flow regime has been used to characterize the global interfacial structure of the flows. Nearly all constitutive relations that provide closures to the interfacial transfers in two-phase flow models, such as the two-fluid model, are often flow regime dependent. Currently, the determination of the flow regimes is primarily based on flow regime maps or transition criteria, which are developed for steady-state, fully-developed flows and widely applied in nuclear reactor system safety analysis codes, such as RELAP5. As two-phase flows are observed to be dynamic in nature (fully-developed two-phase flows generally do not exist in real applications), it is of importance to model the flow regime transition dynamically for more accurate predictions of two-phase flows. The present work aims to develop a dynamic modeling strategy for determining flow regimes in gas-liquid two-phase flows through the introduction of interfacial area transport equations (IATEs) within the framework of a two-fluid model. The IATE is a transport equation that models the interfacial area concentration by considering the creation and destruction of the interfacial area, such as the fluid particle (bubble or liquid droplet) disintegration, boiling and evaporation; and fluid particle coalescence and condensation, respectively. For the flow regimes beyond bubbly flows, a two-group IATE has been proposed, in which bubbles are divided into two groups based on their size and shape (which are correlated), namely small bubbles and large bubbles. A preliminary approach to dynamically identifying the flow regimes is provided, in which discriminators are based on the predicted information, such as the void fraction and interfacial area concentration of small bubble and large bubble groups. This method is expected to be applied to computer codes to improve their predictive capabilities of gas-liquid two-phase flows, in particular for the applications in which flow regime transition occurs.
Date: September 1, 2011
Creator: Wang, X.; Sun, X. & Zhao, H.
Partner: UNT Libraries Government Documents Department

Relationship Between Heat Flows and Geological Structures in the Sichuan Basin, P.R. China

Description: Based on an extensive data collection and analysis, this research has provided reliable representations of the features of the geothermal fields, their heat flow, and relationships with geological structures in the Sichuan Basin. The isotherms below a depth of 1,000 m show high values in the Central Uplift and the Southwest Uplift, and low values in the Northwest and Southeast Depressions. These features probably indicate undulation of crystalline basement and structural depression. At depths greater than 3,000 m, the isotherms tend to become simpler and regionalized. The mean heat flow in the basin is 69.1 mW/m{sup 2}. In the Central Uplift, the Northwest Depression and the East of the basin, heat-flow values range from 58.6 to 71.2 mW/m{sup 2}, with a mean value of 66.1 mWE/m{sup 2}. In the south and southwest, it varies from 76.6 to 100.5 mW/m{sup 2}, with a mean value of 86.2 mW/m{sup 2}. High heat-flow values occur within the uplift of the crystalline basement in the southwest Sichuan, and the heat flow decreases from the south, through the central area, to the northwest.
Date: January 1, 1995
Creator: Zeng, Y.; Yu, H. & Wang, X.
Partner: UNT Libraries Government Documents Department

Beam monitoring and conditioning working group 4 report

Description: The highlights of Seventh Advanced Accelerator Concepts (AAC) working group IV (Beam Monitoring, Conditioning and Control at High Frequencies and Ultrafast Timescales) are presented in this report. The talks given at the working group covered wide range of subjects of beam monitoring. They including a new technique of measuring sub- picosecond electron beam bunch length, optical stochastic cooling experiment, timing jitter measurement of photocathode injector, and proposed experiment of measuring micro-bunching of IFEL accelerator. Working group IV also carried out extensive discussion on the longitudinal and transverse emittance characterization of short (sub- picosecond) low emittance (normalized rms emittance < 1 mm-mrad) electron beam, and beam diagnostics requirements for Muon collider.
Date: January 1, 1997
Creator: Wang, X.J.
Partner: UNT Libraries Government Documents Department


Description: Workshop on Photo-injectors for Energy Recovery Linac was held at National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory (BNL) on January 22 and 23, 2001. Fifty people attended the workshop; they came from three countries, representing universities, industries and national laboratories. This is the first workshop ever held on photo-injectors for CW operation, and for the first time, both DC and RF photo-injectors were discussed at the workshop. Workshop covered almost all major issues of photo-injectors, photocathode, laser system, vacuum, DC, 433 MHz/B-factory cavities based RF gun, 1.3 GHz RF gun and beam instrumentation. High quantum efficiency and long live time photocathode is the issue discussed during the workshop. Four working group leaders have done great jobs summarizing the workshop discussion, and identifying the major issues for future R and D.
Date: January 22, 2001
Creator: WANG,X.J.
Partner: UNT Libraries Government Documents Department

High-brightness electron beam diagnostics at the ATF

Description: The Brookhaven Accelerator Test Facility (ATF) is a dedicated user facility for accelerator physicists. Its design is optimized to explore laser acceleration and coherent radiation production. To characterize the low-emittance, picoseconds long electron beam produced by the ATF`s photocathode RF gun, we have installed electron beam profile monitors for transverse emittance measurement, and developed a new technique to measure electron beam pulse length by chirping the electron beam energy. We have also developed a new technique to measure the ps slice emittance of a 10 ps long electron beam. Stripline beam position monitors were installed along the beam to monitor the electron beam position and intensity. A stripline beam position monitor was also used to monitor the timing jitter between the RF system and laser pulses. Transition radiation was used to measure electron beam energy, beam profile and electron beam bunch length.
Date: July 1, 1996
Creator: Wang, X.J. & Ben-Zvi, I.
Partner: UNT Libraries Government Documents Department

Initial diagnostics commissioning results for the Advanced Photon Source (APS)

Description: Principal diagnostics systems have been installed and nearly all have been commissioned on the subsystems of the Advanced Photon Source (APS) facility. Data have been obtained on beam position, beam profile, current, beam loss rate, and synchrotron radiation monitors on both injector rings and most recently the main 7-GeV storage ring. Results for the 150- to 450-MeV electron beams in the accumulator ring, up to 7 GeV in the injector synchrotron, and 4.5 to 7 GeV in the SR will be presented.
Date: July 1, 1995
Creator: Lumpkin, A.; Patterson, D. & Wang, X.
Partner: UNT Libraries Government Documents Department

The development of beam current monitors in the APS

Description: The Advanced Photon Source (APS) is a third-generation 7-GeV synchrotron radiation source. The precision measurement of beam current is a challenging task in high energy accelerators, such as the APS, with a wide range of beam parameters and complicated noise, radiation, and thermal environments. The beam pulses in the APS injector and storage ring have charge ranging from 50pC to 25nC with pulse durations varying from 30ps to 30ns. A total of nine non- intercepting beam current monitors have been installed in the APS facility (excluding those in the linac) for general current measurement. In addition, several independent current monitors with specially designed redundant interlock electronics are installed for personnel safety and machine protection. This paper documents the design and development of current monitors in the APS,. discusses the commissioning experience in the past year, and presents the results of recent operations.
Date: July 1, 1995
Creator: Wang, X.; Lenkszus, F. & Rotela, E.
Partner: UNT Libraries Government Documents Department

Quantum Monte Carlo calculation of the properties of atomic carbon and diamond

Description: A new method of calculating total energies of solids using non-local pseudopotentials in conjunction with the variational quantum Monte Carlo approach is presented. By using pseudopotentials, the large fluctuations of the energies in the core region of the atoms which occur in quantum Monte Carlo all-electron schemes are avoided. The method is applied to calculate the cohesive energy and structural properties of diamond and the first ionization energy and electron affinity of the carbon atom. Results are in excellent agreement with experiment. 8 refs., 1 fig., 2 tabs.
Date: June 1, 1988
Creator: Fahy, S.; Wang, X.W. & Louie, S.G.
Partner: UNT Libraries Government Documents Department

Motion control of the accumulator flying wires

Description: Flying wire systems for the Fermilab Accumulator are being constructed in order to measure the transverse beam profiles during stacking. Each device passes a 25 micron carbon filament through the beam transversely at a constant velocity of 10 m/s. Collisions between the beam particles and the wire produce secondary particle cascades, which in turn produce photons in a scintillator. A photomultiplier tube is used to measure the light intensity while the wire position is determined by an optical encoder. There are six Accumulator flying wire systems. Four of them are to be used in normal stacking operation: two horizontal and two vertical flying wires are in the AP40 high dispersion section, covering the core orbit and the extraction orbit respectively. The other two horizontal wires are for measuring the momentum distribution of the beam on the central orbit at the Accumulator transition energy. At the AP40 high dispersion region a wire covers the central orbit, the other is in the AP30 low dispersion section. The operation and control of the flying wire system is discussed in this paper. 11 figs.
Date: April 23, 1990
Creator: Wang, X.Q.
Partner: UNT Libraries Government Documents Department

Numerical Model for Conduction-Cooled Current Lead Heat Loads

Description: Current leads are utilized to deliver electrical power from a room temperature junction mounted on the vacuum vessel to a superconducting magnet located within the vacuum space of a cryostat. There are many types of current leads used at laboratories throughout the world; however, conduction-cooled current leads are often chosen for their simplicity and reliability. Conduction-cooled leads have the advantage of using common materials, have no superconducting/normal state transition, and have no boil-off vapor to collect. This paper presents a numerical model for conduction-cooled current lead heat loads. This model takes into account varying material and fluid thermal properties, varying thicknesses along the length of the lead, heat transfer in the circumferential and longitudinal directions, electrical power dissipation, and the effect of thermal intercepts. The model is validated by comparing the numerical model results to ideal cases where analytical equations are valid. In addition, the XFEL (X-Ray Free Electron Laser) prototype current leads are modeled and compared to the experimental results from testing at DESY's XFEL Magnet Test Stand (XMTS) and Cryomodule Test Bench (CMTB).
Date: June 10, 2011
Creator: White, M. J.; Wang, X. L. & Brueck, H. D.
Partner: UNT Libraries Government Documents Department

Modeling and Control System Design for an Integrated Solar Generation and Energy Storage System with a Ride-Through Capability: Preprint

Description: This paper presents a generic approach for PV panel modeling. Data for this modeling can be easily obtained from manufacturer datasheet, which provides a convenient way for the researchers and engineers to investigate the PV integration issues. A two-stage power conversion system (PCS) is adopted in this paper for the PV generation system and a Battery Energy Storage System (BESS) can be connected to the dc-link through a bi-directional dc/dc converter. In this way, the BESS can provide some ancillary services which may be required in the high penetration PV generation scenario. In this paper, the fault ride-through (FRT) capability is specifically focused. The integrated BESS and PV generation system together with the associated control systems is modeled in PSCAD and Matlab platforms and the effectiveness of the controller is validated by the simulation results.
Date: September 1, 2012
Creator: Wang, X.; Yue, M. & Muljadi, E.
Partner: UNT Libraries Government Documents Department


Description: Brookhaven National Laboratory's Accelerator Test Facility (ATF) has embarked on a complete upgrade of its decade old computer system. The planned improvements affect every major component: processors (Intel Pentium replaces VAXes), operating system (Linux/Real-Time Linux supplants OpenVMS), and data acquisition equipment (fast Ethernet equipment replaces CAMAC serial highway.) This paper summarizes the strategies and progress of the upgrade along with plans for future expansion.
Date: June 18, 2001
Partner: UNT Libraries Government Documents Department

Convective Heating of the LIFE Engine Target During Injection

Description: Target survival in the hostile, high temperature xenon environment of the proposed Laser Inertial Fusion Energy (LIFE) engine is critical. This work focuses on the flow properties and convective heat load imposed upon the surface of the indirect drive target while traveling through the xenon gas. While this rarefied flow is traditionally characterized as being within the continuum regime, it is approaching transition where conventional CFD codes reach their bounds of operation. Thus ANSYS, specifically the Navier-Stokes module CFX, will be used in parallel with direct simulation Monte Carlo code DS2V and analytically and empirically derived expressions for heat transfer to the hohlraum for validation. Comparison of the viscous and thermal boundary layers of ANSYS and DS2V were shown to be nearly identical, with the surface heat flux varying less than 8% on average. From the results herein, external baffles have been shown to reduce this heat transfer to the sensitive laser entrance hole (LEH) windows and optimize target survival independent of other reactor parameters.
Date: October 24, 2011
Creator: Holdener, D S; Tillack, M S & Wang, X R
Partner: UNT Libraries Government Documents Department


Description: Oxide nanosystems play a key role as components of catalysts used for the production of H{sub 2} via the steam reforming or the partial oxidation of hydrocarbons, and for the water-gas shift reaction. The behavior seen for Cu-ceria and Au-ceria WGS catalysts indicates that the oxide is much more than a simple support. The special chemical properties of the oxide nanoparticles (defect rich, high mobility of oxygen) favor interactions with the reactants or other catalyst components. More in-situ characterization and mechanistic studies are necessary for the optimization of these nanocatalysts. The use of oxide nanomaterials for the fabrication of PEMFCs and SOFCs can lead to devices with a high practical impact. One objective is to build electrodes with low cost conducting oxide nanoarrays. The electron and oxygen-ion conducting capabilities of many oxides improve when going from the bulk to the nanoscale. Furthermore, one can get a more homogeneous surface morphology and an increase of the effective reaction area. Much more fundamental and practical research needs to be done in this area.
Date: June 30, 2006
Creator: Wang, X. & Rodriguez, J. A.
Partner: UNT Libraries Government Documents Department

Longitudinal Coherence Preservation and Chirp Evolution in a High Gain Laser Seeded Free Electron Laser Amplifier

Description: In this letter we examine the start-up of a high gain free electron laser in which a frequency-chirped coherent seed laser pulse interacts with a relativistic electron beam. A Green function formalism is used to evaluate the initial value problem. We have fully characterized the startup and evolution through the exponential growth regime. We obtain explicit expressions for the pulse duration, bandwidth and chirp of the amplified light and show that the FEL light remains fully longitudinally coherent.
Date: June 7, 2006
Creator: Murphy, J. B.; Wu, Juhao; Wang, X. J. & Watanabe, T.
Partner: UNT Libraries Government Documents Department

Experimental characterization of ATF beam position monitor

Description: Performance of the stripline beam position monitor (BPM) at Brookhaven Accelerator Test Facility (ATF) was experimentally characterized. The design of the BPM and its local receive were discussed briefly. The dynamic range of the BPM was measured from a few pC to an 0.5 nC charge without saturation. The resolution of the BPM was measured to be 150 {micro}m for a 200 pC charge electron bunch. The BPM sum signal was also used to investigate the timing jitter between the RF gun driving laser system and the ATF linac RF system, the sensitivity for timing jitter measurement was measured to be 6m V/ps.
Date: September 1, 1996
Creator: Wang, X.J.; Ben-Zvi, I. & Segalov, Z.
Partner: UNT Libraries Government Documents Department

Emittance studies of the BNL/SLAC/UCLA 1.6 cell photocathode rf gun

Description: The symmetrized 1.6 cell S-band photocathode gun developed by the BNL/SLAC/UCLA collaboration is in operation at the Brookhaven Accelerator Test Facility (ATF). A novel emittance compensation solenoid magnet has also been designed, built and is in operation at the ATF. These two subsystems form an emittance compensated photoinjector used for beam dynamics, advanced acceleration and free electron laser experiments at the ATF. The highest acceleration field achieved on the copper cathode is 150 MV/m, and the guns normal operating field is 130 MV/m. The maximum rf pulse length is 3 {micro}s. The transverse emittance of the photoelectron beam were measured for various injection parameters. The 1 nC emittance results are presented along with electron bunch length measurements that indicated that at above the 400 pC, space charge bunch lengthening is occurring. The thermal emittance, {epsilon}{sub o}, of the copper cathode has been measured.
Date: July 1997
Creator: Palmer, D. T.; Miller, R. H. & Wang, X. J.
Partner: UNT Libraries Government Documents Department