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Fixed Mask Assembly Research for APS Insertion Devices

Description: The Fixed Mask Assembly (FMA) is the first component to interact with the photon beam. Two sets of a pair of FMA channels, vertically and horizontally disposed, contain the beam rather than define it. They are subject to very large heat fluxes during containment. In current practice, the FMA channels are made of heavy, seamless copper, have rectangular cross-sections, and are cooled internally with water. Channels are set at grazing angles ranging from 1 to 6 degrees with respect to the beam, depending on the type of insertion device. APS insertion devices will impose higher heat fluxes on FMAs. Therefore, a need exists to improve the FMA engineering, keeping in the mind the current design criteria and philosophy of FMAs. Preliminary analysis of current heat transfer practice indicates that the major resistance to heat transfer is on the coolant side. Therefore, FMA cooling would benefit from enhanced heat transfer on the coolant side. With this principle in mind, an experimental program has been undertaken to explore the feasibility of using high-performance copper tube configurations which are expected to yield heat transfer coefficients, h, '' in single phase flow systems 2 to 5() times higher than equivalent plain tubes. In this report, the experimental scope and a preliminary analysis of high-performance copper tube configurations are described.
Date: January 1990
Creator: Kuzay, Tuncer M.
Partner: UNT Libraries Government Documents Department


Description: We describe a diagnostics system developed, to measure exponential gain properties and the electron beam dynamics inside the strong focusing 4-m long undulator for the VISA (Visible to Infrared SASE Amplifier) FEL. The technical challenges included working inside the small undulator gap, optimizing the electron beam diagnostics in the high background environment of the spontaneous undulator radiation, multiplexing and transporting the photon beam. Initial results are discussed.
Date: August 13, 2000
Partner: UNT Libraries Government Documents Department

Trends and Opportunities in Light Source Development

Description: After a decade of rather quiet growth for FELs there is now a lot of activity in the light source community. This is the result of a combination of factors including successful operation of the third generation light sources, the establishment of a very productive user community at both synchrotrons and FELs, and the continuing technical improvements of accelerators and related technology which allow ever more challenging machines to be considered. There are a number of themes that carry this development including pushing wavelengths shorter, brightnesses higher, pulses shorter, increasing average power, and providing for multiple synchronized photon beams with multiple wavelengths. This talk will discuss some of the plans and proposals currently circulating and attempt to provide a glimpse into the near future of our field by illustrating the technologies that drive source development.
Date: August 1, 2001
Creator: Neil, George R.
Partner: UNT Libraries Government Documents Department


Description: We describe a diagnostics system developed, to measure exponential gain properties and the electron beam dynamics inside the strong focusing 4-m long undulator for the VISA (Visible to Infrared SASE Amplifier) FEL. The technical challenges included working inside the small undulator gap, optimizing the electron beam diagnostics in the high background environment of the spontaneous undulator radiation, multiplexing and transporting the photon beam. Initial results are discussed.
Date: August 13, 2000
Partner: UNT Libraries Government Documents Department

Entropy and emittance of particle and photon beams

Description: The emittance as the available phase space area is defined as the product of the elementary cell area {delta}{Omega} and exp(S), where S is the normalized entropy of a particle beam. The definition is based on the fact that the factor exp(S) can be interpreted as the number of the occupied cells. For particle beams, a closed expression for the emittance in terms of the phase space distribution function is obtained which is independent of {delta}{Omega}. To compute the emittance of the radiation beam, it is necessary to find the eigenvalues of the correlation operator. An explicit solution is found for the case of a partially coherent radiation beam which is a stochastic superposition of coherent Gaussian beams with a Gaussian probability distribution. Such a beam is a reasonable model for undulator radiation by beam of electrons. From the requirement that the radiation emittance reproduces the particle beam emittance in the incoherent limit, the elementary cell area {delta}{Omega} is determined unambiguously to be {lambda}, the radiation wavelength. The emittance in the incoherent limit then becomes {lambda}.
Date: April 1, 1995
Creator: Kim, K.J. & Littlejohn, R.G.
Partner: UNT Libraries Government Documents Department

Continuum-continuum Autler-Townes splitting in calcium

Description: Strong-field ionization of two-electron atoms can result in scenarios in which the electron-electron correlation plays an important role. It was recently suggested that a splitting similar to the Autler-Townes effect would occur when two ionization continua are resonantly coupled in two-electron atoms. This is obviously at variance with the case of one electron atoms where coupling between continua does not induce oscillations but instead leads to exponential decay of one continuum into another. The special case considered by Grobe and Eberly is that of a strong radiation field resonantly coupling two ionic states. Formally, the states which are coupled are continuum states (two-electron states in which one electron is in a continuum state), but nevertheless the corresponding photoelectron peak is split. Physically, the reason for this is that the electron-electron interaction transfers the energy shift of the core electron to the outgoing electron and has been dubbed {open_quotes}coherence transfer{close_quotes} by Ref.
Date: October 1, 1995
Creator: Walker, B.; Sheehy, B. & Kaluza, M.
Partner: UNT Libraries Government Documents Department

Insertion Device and Beam Line Plans for the Advanced Photon Source : a Report and Recommendations by the Insertion Device and Beam Line Planning Committee

Description: In the 7-GeV Advanced Photon Source (APS) Conceptual Design Report (CDR), fifteen complete experimental beam lines were specified in order to establish a representative technical and cost base for the components involved. In order to optimize the composition of the insertion devices and the beam line, these funds are considered a ''Trust Fund.'' The present report evaluates the optimization for the distribution of these funds so that the short- and long-term research programs will be most productive, making the facility more attractive from the user's point of view. It is recommended that part of the "Trust Fund" be used for the construction of the insertion devices, the front-end components, and the first-optics, minimizing the cost to potential users of completing a beam line. In addition, the possibility of cost savings resulting from replication and standardization of high multiplicity components (such as IDs, front ends, and first-optics instrumentation) is addressed.
Date: February 1987
Creator: Boyce, R.; Hewitt, R.; Morrison, T. I.; Shenoy, G. K.; Thomlinson, W. & Viccaro, P. J.
Partner: UNT Libraries Government Documents Department

Actinic characterization of EUV bump-type phase defects

Description: Despite tremendous progress and learning with EUV lithography, quantitative experimental information about the severity of point-like phase defects remains in short supply. We present a study of measured, EUV aerial images from a series of well-characterized, open-field, bump-type programmed phase defects, created on a substrate before multilayer deposition.
Date: January 10, 2011
Creator: Goldberg, Kenneth A.; Mochi, Iacopo & Liang, Ted
Partner: UNT Libraries Government Documents Department

The Upgrade of CEBAF to 12 GeV: Physics Motivations and Technical Aspects

Description: The Continuous Electron Beam Accelerator Facility, CEBAF, makes use of electron and photon beams with an energy up to 6 GeV to investigate the electromagnetic structure of mesons, nucleons, and nuclei. We discuss the physics motivation for upgrading the facility to a maximum energy of 12 GeV and some of the key technological aspects of the upgrade.
Date: August 1, 2002
Creator: Mecking, Bernhard & Cardman, Larry
Partner: UNT Libraries Government Documents Department

A photon beam position monitor for SSRL beamline 9

Description: We present here the concept of a simple one dimensional photon beam position monitor for use with high power synchrotron radiation beams. It has micron resolution, reasonable linearity in an inexpensive design. Most important, is its insensitivity to diffusely scattered low energy radiation from components upstream of the monitor.
Date: October 1, 1995
Creator: Cerino, J.A.; Rabedeau, T. & Bowen, W.
Partner: UNT Libraries Government Documents Department

A study of heat transfer for two layered composite inclined plate crotch absorbers

Description: Since a copper plate (Z=29) absorbs most of the photon energy very near the surface, the temperature of the surface becomes very high despite of having a high thermal conductivity. On the other hand, a beryllium plate( Z=4) can diffuse the intense radiation throughout the depth of its plate by allowing photons to penetrate, but has a low thermal conductivity (about half of that of a copper). As an effort to combine both merits of Be and Cu, a Be-Cu composite absorber was developed and has been successfully used in CESR. They analyzed composite the heat transfer problem numerically for the case of a vertically located Be-Cu composite cylinder which results in symmetry with respect to the center of photon beam and allows them to consider only half a domain. In this note, an inclined absorber with two layered metal plates is considered and a full domain solution is sought to study the asymmetric heating due to the inclined photon beam penetration heating. An analytical solution for heat transfer is obtained for a full domain using the Fourier integral transformation and of particular interests are the effects of different thickness ratios of two materials and different inclination angles.
Date: November 1, 1989
Creator: Choi, M.
Partner: UNT Libraries Government Documents Department

Photon beam polarization and non-dipolar angular distributions

Description: Angular distributions of ejecta from unoriented atoms and molecules depend upon the polarization state of the incident x-rays as well as upon the dynamics of the physical systems being studied. I recommend a simple geometrical way of looking at the polarization and its effects upon angular distributions. The polarization is represented as a vector in a parameter space that faithfully represents the polarization of the beam. The simple dependence of the angular dependence of the angular distributions on the polarization vector enables easy extraction of the dynamical information contained in those angular distributions. No new physical results emerge from this geometrical approach, but known consequences of the symmetries appear in an easily visualized form that I find pleasing and that has proved to be useful for planning experiments and for analyzing data.
Date: August 1, 1996
Creator: Peshkin, M
Partner: UNT Libraries Government Documents Department

A method for characterizing photon radiation fields

Description: Uncertainty in dosimetric and exposure rate measurements can increase in areas where multi-directional and low-energy photons (< 100 keV) exist because of variations in energy and angular measurement response. Also, accurate measurement of external exposures in spatially non-uniform fields may require multiple dosimetry. Therefore, knowledge of the photon fields in the workplace is required for full understanding of the accuracy of dosimeters and instruments, and for determining the need for multiple dosimeters. This project was designed to develop methods to characterize photon radiation fields in the workplace, and to test the methods in a plutonium facility. The photon field at selected work locations was characterized using TLDs and a collimated NaI(Tl) detector from which spatial variations in photon energy distributions were calculated from measured spectra. Laboratory results showed the accuracy and utility of the method. Field measurement results combined with observed work patterns suggested the following: (1) workers are exposed from all directions, but not isotropically, (2) photon energy distributions were directionally dependent, (3) stuffing nearby gloves into the glovebox reduced exposure rates significantly, (4) dosimeter placement on the front of the chest provided for a reasonable estimate of the average dose equivalent to workers` torsos, (5) justifiable conclusions regarding the need for multiple dosimetry can be made using this quantitative method, and (6) measurements of the exposure rates with ionization chambers pointed with open beta windows toward the glovebox provided the highest measured rates, although absolute accuracy of the field measurements still needs to be assessed.
Date: April 1, 1999
Creator: Whicker, J.J.; Hsu, H.H.; Hsieh, F.H. & Borak, T.B.
Partner: UNT Libraries Government Documents Department

The circular RFQ storage ring

Description: This paper presents a novel idea of storage ring for the accumulation of intense beams of light and heavy ions at low energy. The new concept is a natural development of the combined features used in a conventional storage ring and an ion trap, and is basically a linear RFQ bend on itself. In summary the advantages are: smaller beam dimensions, higher beam intensity, and a more compact storage device.
Date: December 31, 1998
Creator: Ruggiero, A. G.
Partner: UNT Libraries Government Documents Department

Design of a diagnostic area-type beam position monitor for x-ray beamlines at the National Synchrotron Light Source

Description: We have built a area-type beam position monitor for use as a diagnostic tool at the National Synchrotron Light Source. The device is compact and fits into a vacuum cross. We completed range and resolution tests of the device at beamline X-19A at the NSLS and concluded that such a monitor can be placed in the confines of the vacuum cross.
Date: October 1, 1996
Creator: Corridon, D.
Partner: UNT Libraries Government Documents Department

The Use of X-Ray Microbeams in Materials Science

Description: Most materials are heterogeneous on mesoscopic length scales (tenths-to-tens of microns), and materials properties depend critically on mesoscopic structures such as grain sizes, texture, and impurities. The recent availability of intense, focused x-ray microbeams at synchrotron facilities has enabled new techniques for mesoscale materials characterization. We describe instrumentation and experiments on the MHATT-CAT and UNICAT undulator beamlines at the Advanced Photon Source which use micron and submicron-size x-ray beams to investigate the grain orientation, local strain and defect content in a variety of materials of technological interest. Results from a combinatorial study on epitaxial growth of oxide films on textured metal substrates will be described to illustrate x-ray microbeam capabilities.
Date: October 13, 1998
Creator: Budai, J.D.; Chung, J.-S.; Ice, G.E.; Larson, B.C.; Lowe, W.P.; Norton, D.P. et al.
Partner: UNT Libraries Government Documents Department

Center for beam physics 1996-1997

Description: The Center for Beam Physics (CBP) is a multidisciplinary research and development unit in the Accelerator and Fusion Research Division at the Ernest Orlando Lawrence Berkeley National Laboratory of the University of California. At the heart of the Center`s mission is the fundamental quest for mechanisms of acceleration, radiation, transport, and focusing of energy and information. Special features of the Center`s program include addressing R&D issues needing long development time and providing a platform for conception, initiation, and support of institutional projects based on beams. The Center brings to bear a significant amount of diverse, complementary, and self-sufficient expertise in accelerator physics, synchrotron radiation, advanced microwave techniques, plasma physics, optics, and lasers on the forefront R&D issues in particle and photon beam research. In addition to functioning as a clearinghouse for novel ideas and concepts and related R&D (e.g., various theoretical and experimental studies in beam physics such as nonlinear dynamics, phase space control, laser-beam-plasma interaction, free-electron lasers, optics, and instrumentation), the Center provides significant support to Laboratory facilities and initiatives. This roster and annual report provides a glimpse of the scientists, engineers, technical support, students, and administrative staff that make up the CBP`s outstanding team and gives a flavor of their multifaceted activities during 1996 and 1997.
Date: February 1, 1997
Partner: UNT Libraries Government Documents Department

The BNL AGS accelerator complex status and future plans

Description: This paper describes the present performance and capability of the BNL AGS accelerator complex and possible future intensity upgrade plans. In 1995, the AGS reached its design upgrade goal of 6.0 x 10(exp 13) ppp with the Booster. The AGS with a new fast extracted beam (FEB) system is able to perform single bunch multiple extraction at 30 Hz per AGS cycle for the g-2 experiment and for RHIC injection.
Date: May 1, 1997
Creator: Tanaka, Mitsuyoshi
Partner: UNT Libraries Government Documents Department

A photon calorimeter using lead tungstate crystals for the CEBAF HAll A Compton polarimeter

Description: A new Compton polarimeter is built on the CEBAF Hall A electron beam line. Performances of 10% resolution and 1% calibration are required for the photon calorimeter of this polarimeter. This calorimeter is built with lead tungstate scintillators coming from the CMS electromagnetic calorimeter R&amp;D. Beam tests of this detector have been made using the tagged photon beam line at MAMI, Mainz, and a resolution of 1.76%+2.75%/v+0.41%/E has been measured.
Date: May 1, 2000
Creator: Neyret, D.; Pussieux, T.; Auger, T.; Baylac, M.; Burtin, E.; Cavata, C. et al.
Partner: UNT Libraries Government Documents Department

Slow Orbit Feedback at the ALS Using Matlab

Description: The third generation Advanced Light Source (ALS) produces extremely bright and finely focused photon beams using undulatory, wigglers, and bend magnets. In order to position the photon beams accurately, a slow global orbit feedback system has been developed. The dominant causes of orbit motion at the ALS are temperature variation and insertion device motion. This type of motion can be removed using slow global orbit feedback with a data rate of a few Hertz. The remaining orbit motion in the ALS is only 1-3 micron rms. Slow orbit feedback does not require high computational throughput. At the ALS, the global orbit feedback algorithm, based on the singular valued decomposition method, is coded in MATLAB and runs on a control room workstation. Using the MATLAB environment to develop, test, and run the storage ring control algorithms has proven to be a fast and efficient way to operate the ALS.
Date: March 25, 1999
Creator: Portmann, G.
Partner: UNT Libraries Government Documents Department

Quantum fluctuations in beam dynamics.

Description: Quantum effects could become important for particle and photon beams used in high-luminosity and high brightness applications in the current and next generation accelerators and radiation sources. This paper is a review of some of these effects.
Date: June 4, 1998
Creator: Kim, K.-J.
Partner: UNT Libraries Government Documents Department

Study of Row Phase Dependent Skew Quadrupole Fields in Apple-II Type EPUs at the ALS

Description: Since about 5 years, Apple-II type Elliptically Polarizing Undulators (EPU) have been used very successfully at the ALS to generate high brightness photon beams with arbitrary polarization. However, both EPUs installed so far cause significant changes of the vertical beamsize, especially when the row phase is changed to change the polarization of the photons emitted. Detailed measurements indicate this is caused by a row phase dependent skew quadrupole term in the EPUs. Magnetic measurements revealed the same effect for the third EPU to be installed later this year. All measurements to identify and quantify the effect with beam will be presented, as well as some results of magnetic bench measurements and numeric field simulations.
Date: May 7, 2004
Creator: Steier, C.; Marks, S.; Prestemon, Soren; Robin, David; Schlueter, Ross & Wolski, Andrzej
Partner: UNT Libraries Government Documents Department