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Vacuum ring exit chamber temperatures due to wiggler beam heating

Description: A study was made to determine the effects of a shift in the electron orbital plane and resulting displacement of the wiggler photon beam striking the inner surface of the existing vacuum chamber outer wall. The wiggler beam/vacuum chamber geometry is shown. 7 figures.
Date: January 1, 1984
Creator: Sharma, S. & Ulc, S.
Partner: UNT Libraries Government Documents Department

Thermal absorber for high power density photon beams

Description: The high power density of multipole wiggler radiation from the x-ray ring at the National Synchrotron Light Source at Brookhaven National Laboratory precludes the use of normal incidence water cooled masks and shutters due to high metal temperatures and resulting high stresses and/or deflections and the possibility of cooling water boiling. One way the power density can be reduced is by positioning the absorber surface at a small angle to the beam, a technique first developed by Lawrence Berkeley Laboratory. Finite element analyses results for temperatures, displacements and stresses are presented in this paper for a thermal absorber designed for ultra-high vacuum operation.
Date: January 1, 1985
Creator: Ulc, S. & Sharma, S.
Partner: UNT Libraries Government Documents Department

Thermal and structural analysis of ring components by the finite element method

Description: In a previous report, a thermal study was made in order to determine the effects of a shift in the electron vertical orbital plane, and the resulting displacement of the wiggler photon beam striking the inner surface of the vacuum chamber. Since then, due to some changes in the physical parameters of the vacuum chamber, a new design had been developed. The new geometry is quite different from the one described earlier, due primarily to an increase in the chamber vertical aperture which was opened to 23 mm. from an initial opening of 6 mm. Subsequently, a new study was conducted for this new chamber design that included a structural analysis in order to determine the stresses and deflections of the vacuum chamber due to the combined thermal and mechanical loading. It should be noted that various geometrical models were analyzed before the final geometry was decided. This report will only describe in detail the results of the thermal and structural analysis of the final geometry using the finite element code, ANSYS.
Date: January 1, 1985
Creator: Alforque, R. & Sharma, S.
Partner: UNT Libraries Government Documents Department

Mirror and grating surface figure requirements for grazing incidence synchrotron radiation beamlines: Power loading effects

Description: At present, grazing incidence mirrors are used almost exclusively as the first optical element in VUV and soft x-ray synchrotron radiation beamlines. The performance of these mirrors is determined by thermal and mechanical stress-induced figure errors as well as by figure errors remaining from the grinding and polishing process. With the advent of VUV and soft x-ray undulators and wigglers has come a new set of thermal stress problems related to both the magnitude and the spatial distribution of power from these devices. In many cases the power load on the entrance slits and gratings in these beamlines is no longer negligible. The dependence of thermally-induced front-end mirror figure errors on various storage ring and insertion device parameters (especially those at the National Synchrotron Light Source) and the effects of these figure errors on two classes of soft x-ray beamlines are presented.
Date: January 1, 1987
Creator: Hulbert, S.L. & Sharma, S.
Partner: UNT Libraries Government Documents Department

Mirror and grating surface figure requirements for grazing incidence synchrotron radiation beamlines: Power loading effects

Description: At present, grazing incidence mirrors are used almost exclusively as the first optical element in VUV and soft x-ray synchrotron radiation beam lines. The performance of these mirrors is determined by thermal and mechanical stress-induced figure errors as well as by figure errors remaining from the grinding and polishing process. With the advent of VUV and soft x-ray undulators and wigglers has come a new set of thermal stress problems related to both the magnitude and the spatial distribution of power from these devices. In many cases the power load on the entrance slits and gratings in these beamlines is no longer negligible. The dependence of thermally-induced front-end mirror figure errors on various storage ring and insertion device parameters (especially those at the NSLS) and the effects of these figure errors on a class of soft x-ray beam lines are presented. 17 refs., 5 figs., 2 tabs.
Date: October 21, 1987
Creator: Hulbert, S.L. & Sharma, S.
Partner: UNT Libraries Government Documents Department

Design of vacuum chambers downstream of NSLS x-ray ring insertion devices

Description: In an electron storage ring the maximum power deposited in the vacuum chamber walls is that produced by the electron beam as it is accelerated through the bending magnets. In the NSLS x-ray ring this power is 58 watts per linear cm of arc chamber length, or 2 kw/cm/sup 2/ taking into account the beam size. Standard water cooling techniques are adequate to protect the chambers from overheating under this range of power density. However, with the installation of wigglers and undulators, cooling of the chambers is no longer a trivial matter. Without proper interlocks and cooling, beams from these insertion devices can easily do permanent thermal damage to the chamber walls. As part of the NSLS Phase II project three insertion devices are planned for the beamlines X-1, X-17 and X-25, namely, a soft x-ray undulator, a superconducting wiggler and a hybrid wiggler. The effect of these insertion devices on the design of vacuum chambers downstream of these devices is the subject of this paper. 4 refs., 3 figs., 1 tab.
Date: January 1, 1988
Creator: Schuchman, J.C. & Sharma, S.
Partner: UNT Libraries Government Documents Department

Nonlinear failure analysis of a reinforced concrete containment under internal pressure

Description: A detailed nonlinear finite element model is used to investigate the failure response of the Indian Point containment building under severe accident pressures. Refined material models are used to describe the complex stress-strain behavior of the liner and rebar steels, the plain concrete and the reinforced concrete. Structural geometry of the containment is idealized by eight layers of axisymmetric finite elements through the wall thickness in order to closely model the actual placement of the rebars. Soil stiffness under the containment base mat is modeled by a series of nonlinear spring elements. Numerical results presented in the paper describe cracking and plastic deformation (in compression) of the concrete, yielding of the liner and rebar steels and eventual loss of the load carrying capacity of the containment. The results are compared with available data from the previous studies for this containment. 8 references, 9 figures.
Date: January 1, 1984
Creator: Sharma, S.; Wang, Y.K. & Reich, M.
Partner: UNT Libraries Government Documents Department

Investigation of passive vibration damping methods for the Advanced Photon Source storage ring girders.

Description: Beam stability is a major concern for the operation of the APS. One of the many contributing factors to electron-beam instability is mechanical vibration of the accelerator components especially the focusing magnets. The electron beam should be stable to 5% of its rms size to maintain the specified photon beam stability. The APS uses steel girders to support the conventional magnets and vacuum chambers in the storage ring (SR). Three pedestal and jack assemblies support the girders. Damping pads are presently installed between the pedestals and the jacks. These damping pads have been shown to be very effective in reducing the fundamental girder-vibration mode. The horizontal vibration levels of the SR quadrupole magnets are presently within specification at between two and four times the ground motion, i.e., 50-100 nm rms (4-50 Hz). Future improvements to the APS beam quality would require a further reduction in girder vibration. Several options for reducing the vibration of the girders and magnets are discussed, and the measurement results are presented.
Date: September 11, 2002
Creator: Sharma, S. & Doose, C.
Partner: UNT Libraries Government Documents Department

High heat-load absorbers for the APS storage ring

Description: The power density of the dipole x-rays in the 7-GeV APS storage ring is 261 watts/mrad at 300 mA of beam current. An array of absorbers is used in the ring to shield its vacuum chambers and diagnostics components in the path of these intense x-rays. This paper describes some of the unique absorber designs that were developed to handle the requirements of high power density and UHV compatibility with no water-to-vacuum joints.
Date: July 21, 2000
Creator: Sharma, S.; Rotela, E. & Barcikowski, A.
Partner: UNT Libraries Government Documents Department

Influence of processing variables on the structure and properties of ZnO films

Description: Zinc oxide films of high optical quality have been deposited onto both silica and silicon substrates using reactive sputtering, pulsed laser deposition, and an aqueous solution based technique. Films have been characterized with respect to crystalline phase and phase stability, surface morphology, and optical response by means of X-ray diffraction, Raman Spectroscopy, Atomic Force Microscopy, optical transmission and ellipsometry measurements. All films studied were of the wurtzite phase, fine-grained, and exhibited varying degrees of c-axis orientation with respect to the substrate normal depending upon deposition conditions. Films showed some degree of residual tensile stress which was inferred from the E{sub 2} Raman line shift relative to the single crystal frequency. The wurtzite phase was found to be stable to temperatures near 800{degrees}C, but at higher temperatures, reaction with silica led to evolution of Zn{sub 2}SiO{sub 4} at the interface. Variations in Raman line intensities upon post deposition annealing has been correlated with oxidation of excess zinc in the lattice.
Date: April 1, 1995
Creator: Exarhos, G.J. & Sharma, S.K.
Partner: UNT Libraries Government Documents Department

Passive vibration damping of the APS machine components

Description: The accelerator and beamline components of the APS have stringent vibration criteria in order to meet the beam stability requirements. For instance, the vibration amplitude of the storage ring quadrupoles is restricted to 0.11 {mu}m (rms) over a frequency range of 4--50 Hz. Damping pads, consisting of thin viscoelastic f`ilms sandwiched between stainless steel plates, have been designed for passive vibration damping. Results presented in this paper show that the damping pads under the storage ring girder-magnet assemblies reduced the vibration amplification factor Q from over 100 to 8. The broad band rms motion of the magnets was reduced by a factor of 2.5 to 3. Preliminary results for a monochromator housing show a potential use of such damping pads for vibration control of beamline components. Radiation and creep effects on the damping pads` performance are considered.
Date: December 31, 1995
Creator: Mangra, D.; Sharma, S. & Jendrzejczyk, J.
Partner: UNT Libraries Government Documents Department

Nonlinear finite-element analysis of a reinforced-concrete Mark III containment under pressure and gravity loads. [BWR]

Description: An analysis of a Mark III reactor containment vessel subjected to a uniformly increasing internal pressure and gravity loads is carried out in order to ascertain the load carrying capacity of the structure under hydrogen burn. The analysis is conducted by using a nonlinear finite element model that includes nonlinearities in the strain-displacement relations as well as in the material constitutive equations. In this analysis, the nonlinear behavior of the liner and reinforcement steels is described by a von Mises elastic-plastic model with isotropic hardening. A recently developed elastic-plastic-fracture model that includes both the cracking and crushing limit states is used for the plain concrete. Consistent smearing and de-smearing procedures are then used to represent the composite material properties of the reinforced concrete by an anisotropic and locally homogeneous continuum. Results pertaining to the critical regions of the containment where cracking of the concrete, yielding of the reinforcement bars, and substantial straining of the liner take place are discussed.
Date: January 1, 1983
Creator: Sharma, S.; Reich, M.; Shteyngart, S. & Chang, T.Y.
Partner: UNT Libraries Government Documents Department

Thermal effects and mirror surface figure requirements for a diagnostic beamline at the Advanced Light Source

Description: An imaging beamline based on a Kirkpatrick-Baez mirror configuration has been designed to image the electron beam in the ALS storage ring, to measure its size and shape. The electron beam emittance will be small ({epsilon}h = 3.4 {times} 10{sup {minus}9} m rad) and the quality of the image is extremely sensitive to surface figure distortion of the mirrors. Thermal distortions and surface temperatures have been calculated for radiatively cooled mirrors of various materials in a search for a simple design which avoids water cooling. The choice of mirror material and the thermal and mechanical design is discussed. 6 refs.
Date: October 28, 1991
Creator: Warwick, T. & Sharma, S.
Partner: UNT Libraries Government Documents Department

End-to-End Network QoS via Scheduling of Flexible Resource Reservation Requests

Description: Modern data-intensive applications move vast amounts of data between multiple locations around the world. To enable predictable and reliable data transfer, next generation networks allow such applications to reserve network resources for exclusive use. In this paper, we solve an important problem (called SMR3) to accommodate multiple and concurrent network reservation requests between a pair of end-sites. Given the varying availability of bandwidth within the network, our goal is to accommodate as many reservation requests as possible while minimizing the total time needed to complete the data transfers. We first prove that SMR3 is an NP-hard problem. Then we solve it by developing a polynomial-time heuristic, called RRA. The RRA algorithm hinges on an efficient mechanism to accommodate large number of requests by minimizing the bandwidth wastage. Finally, via numerical results, we show that RRA constructs schedules that accommodate significantly larger number of requests compared to other, seemingly efficient, heuristics.
Date: November 14, 2011
Creator: Sharma, S.; Katramatos, D. & Yu, D.
Partner: UNT Libraries Government Documents Department

An evaluation of enhanced cooling techniques for high-heat load absorbers.

Description: Many components of the storage ring and front ends in the third generation of light sources are subjected to high heat loads from intense x-rays. Temperature rises and thermal stresses in these components must be kept within acceptable limits of critical heat flux and low-cycle fatigue failure. One of the design solutions is to improve heat transfer to the cooling water either by increasing water velocity in the cooling channels or by using inserts, such as porous media, twisted tapes and wire springs. In this paper we present experimental and analytical results to compare various enhanced cooling techniques for conditions specific to heating from an x-ray fan.
Date: October 28, 2002
Creator: Sharma, S.; Doose, C.; Rotela, E. & Barickowski, A.
Partner: UNT Libraries Government Documents Department

Design and analysis of a Be window for the APS diagnostics undulator beamline

Description: The design of a beryllium (Be) window for use under the extremely high heat load of an undulator beam is one of the challenges for third-generation synchrotron radiation beamlines. A novel design of a Be window is presented for the Advanced Photon Source (APS) diagnostics undulator beamline, whose beam has a peak power density of 150 W/mm{sup 2} (7 GeV/100 mA stored beam). The window has a double concave profile with a thickness of 0.5 mm at the center and is brazed to a water-cooled oxygen-free, high-conductivity (OFHC) copper manifold. Finite-element thermal analysis of the Be window is also presented.
Date: June 1, 1997
Creator: Sheng, I.C.; Yang, B.X. & Sharma, S.
Partner: UNT Libraries Government Documents Department

A high-precision cryogenically-cooled crystal monochromator for the APS diagnostics beamline

Description: A high-precision cryogenically-cooled crystal monochromator has been developed for the APS diagnostics beamline. The design permits simultaneous measurements of the particle beam size and divergence. It provides for a large rotation angle, {minus}15{degree} to 180{degree}, with a resolution of 0.0005{degree}. The roll angle of the crystal can be adjusted by up to {+-}3{degree} with a resolution of 0.0001{degree}. A vertical translational stage, with a stroke of {+-}25 mm and resolution of 8 {micro}m, is provided to enable using different parts of the same crystal or to retract the crystal from the beam path. The modular design will allow optimization of cooling schemes to minimize thermal distortions of the crystal under high heat loads.
Date: July 24, 2000
Creator: Rotela, E.; Yang, B.; Sharma, s. & Barcikowski, A.
Partner: UNT Libraries Government Documents Department

Thermomechanical analysis of a compact-design high heat load crotch absorber

Description: The Advanced Photon Source (APS) is a third-generation synchrotron facility built to generate extremely powerful x-rays. x-ray absorbers in the APS dipole vacuum chambers, known as crotch absorbers, are subjected to a very high power density of 750 Watt/mm{sup 2} at 300 mA of beam current. In the compact design of the APS crotch absorbers, this high heat load is handled by a combination of optimized geometry, fins for power dispersion and cooling efficiency, and a material with high fatigue strength (Glidcop). The basic design and the results of detailed thermomechanical finite element analysis are presented in this paper.
Date: July 1, 1995
Creator: Sheng, I.C.; Sharma, S.; Rotela, R. & Howell, J.
Partner: UNT Libraries Government Documents Department

Storage ring injection area upgrade at the Advanced Photon Source (APS).

Description: Recent machine studies at the Advanced Photon Source (APS) showed that at a beam current of about 140 mA, the storage ring (SR) injection-area components experienced unacceptable elevated temperatures. Heating of these components is related to several factors, namely: aperture discontinuity, poor contact between the rf fingers and the solid sleeve liner, inadequate x-ray shielding, and nonuniform conductive coating on the kicker ceramic chambers. To address these deficiencies, we have developed design upgrades for the injection-area kicker magnets, vacuum chambers, transition absorbers, and bellows-liner assemblies. In this paper, we discuss important features of the new designs and their impact on machine operation at high beam current.
Date: September 17, 2002
Creator: Morrison, L. H.; Givens, M. & Sharma, S.
Partner: UNT Libraries Government Documents Department

Design of a high-precision tunable double crystal monochromator

Description: The design of high-precision tunable double crystal monochromator is described. Each crystal of the monochromator can be aligned independently by a double-axis gimbal mechanism providing rotations about two perpendicular axes. Two orthogonal linear actuators operate the gimbal mechanism via a connecting bar. The exit beam height is controlled by separate linear actuators that change the distance between the crystals along the beam axis. Vertical separation between the crystals may also be adjusted. Thermal deformations are minimized in this compact UHV compatible design by water cooling of the first crystal. 7 refs.
Date: February 1, 1992
Creator: Shleifer, M.; Sharma, S.; Rotela, E. & Brite, C.
Partner: UNT Libraries Government Documents Department

Mechanical design of SXLS (Superconducting X-ray Lithography Source) radio-frequency cavity

Description: This paper presents the mechanical design of a Radio-Frequency (RF) cavity to be used on a compact storage ring for Superconducting X-ray Lithography Source (SXLS). Various design features of this cavity are discussed, including basic geometrical configuration, structural design, initial and operational tuning, vacuum multipactoring, power window, and damping of higher order modes. A second application of this cavity design for beam life extension in an existing storage ring is also described. 2 refs., 6 figs.
Date: January 1, 1989
Creator: Mortazavi, P.; Sharma, S.; Keane, J. & Thomas, M.
Partner: UNT Libraries Government Documents Department

Adaptive optics for high power beam lines using diamond crystal monochromators

Description: Preserving the high source brightness of the third generation of synchrotron radiation facilities will require that thermal and pressure deformations of the monochromator crystals be maintained within a few arc- seconds. Recent experiments at the National Synchrotron Light Source (NSLS) have demonstrated the potential of adaptive crystal optics to cope with high power densities. In this technique the crystals deformations are minimized both by an efficient water-jet cooling and by externally applied pressure loads. Thermal deformation can be reduced further with diamond crystals because of their high thermal conductivity and low coefficient of thermal expansion. In this paper we describe the results achieved by optimization of adaptive crystal optics for diamond crystals.
Date: December 31, 1992
Creator: Sharma, S.; Berman, L. E.; Hastings, J. B. & Hart, M.
Partner: UNT Libraries Government Documents Department