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Misalignment sensitivity of an inclined crystal monochromator

Description: The sensitivity of a novel inclined crystal monochromator design to misalignments has been calculated, and compared to data. Rocking curve line narrowing as well as broadening can occur because the asymmetry factor of dynamical diffraction given by b=s{sub O}{center dot}n/s{sub H}{center dot}n can have an absolute value larger or smaller than unity. Here s{sub O}{center dot}n and s{sub H}{center dot}n are the direction cosines of the incident and diffracted beams, respectively, and n is the inward surface normal. An inclined double crystal monochromator which is perfectly aligned would have b = {minus}1 for both crystals, and only then would the diffraction by symmetric. We have computed b and rocking curve widths for inclination angles of 70.53{degree} and 85.00{degree}, and we compare the 70.53{degree} case to data for silicon {l brace}111{r brace} reflections using 8 KeV (CuK{alpha}{sub 1}) radiation. The 70.53{degree} case applies to (11{bar 1}) reflection from a (111) oriented crystal. We report that rotations around the reciprocal lattice vector have the expected effect on b.
Date: October 1, 1991
Creator: Macrander, A.T. & Lee, W.K.
Partner: UNT Libraries Government Documents Department

Modifications of the beam profile in the new inclined crystal geometry

Description: The new inclined crystal geometry has been successfully used in high heat load X-ray monochromator tests. The important aspect of this geometry is that from a diffraction point of view, when properly aligned, is is a symmetric Bragg reflection; i.e., b = k{sub i} . n/k{sub out}.n = {minus}1. An interesting result of this geometry is that with a single reflection from an inclined crystal, the output X-ray beam shape changes dramatically while maintaining the same beam cross section area. For example, a parallel 8 keV input X-ray beam using Si(111) reflection, with an inclination angle of 70.5{degrees}, the output beam size is compressed by about a factor of 5.4 in one direction and expanded by the same factor in the other direction. This geometry can therefore, be used to alter the source line profile of in house X-ray generators and in some cases, be used to better match the sample size and the X-ray beam. The effect of this geometry on beam profiles, beam divergences and acceptance angles will be discussed.
Date: October 1, 1991
Creator: Lee, W.K. & Macrander, A.T.
Partner: UNT Libraries Government Documents Department

APS high heat load monochromator

Description: This document contains the design specifications of the APS high heat load (HHL) monochromator and associated accessories as of February 1993. It should be noted that work is continuing on many parts of the monochromator including the mechanical design, crystal cooling designs, etc. Where appropriate, we have tried to add supporting documentation, references to published papers, and calculations from which we based our decisions. The underlying philosophy behind performance specifications of this monochromator was to fabricate a device that would be useful to as many APS users as possible, that is, the design should be as generic as possible. In other words, we believe that this design will be capable of operating on both bending magnet and ID beamlines (with the appropriate changes to the cooling and crystals) with both flat and inclined crystal geometries and with a variety of coolants. It was strongly felt that this monochromator should have good energy scanning capabilities over the classical energy range of about 4 to 20 keywith Si (111) crystals. For this reason, a design incorporating one rotation stage to drive both the first and second crystals was considered most promising. Separate rotary stages for the first and second crystals can sometimes provide more flexibility in their capacities to carry heavy loads (for heavily cooled first crystals or sagittal benders of second crystals), but their tuning capabilities were considered inferior to the single axis approach.
Date: February 1, 1993
Creator: Lee, W.K. & Mills, D.
Partner: UNT Libraries Government Documents Department

A finite element analysis of room temperature silicon crystals for the advanced photon source bending-magnet and insertion-device beams

Description: In this paper, we give the results of a series of thermal and distortion finite element analyses performed on room temperature silicon for the three standard APS sources, namely, the bending magnet, Wiggler A, and Undulator A. The modeling was performed with the silicon cooled directly with water or liquid gallium through rectangular channels.
Date: October 1, 1994
Creator: Assoufid, L.; Lee, W.K. & Mills, D.
Partner: UNT Libraries Government Documents Department

Advanced photon source undulator beamline tests of a contact-cooled silicon u-shaped monochromator

Description: At the Advanced Photon Source (APS), undulator insertion devices are capable of producing x-ray beams with total power of about 5 kW and normal incidence heat fluxes of about 170 W/mm{sup 2} at 30 m from the source. On beamlines in which the first optical element is a mirror, the reflected beam from the mirror still carries considerable power and power density. Depending on its location, the monochromator downstream of the mirror might be subject to 300 W total power and 5 W/mm{sup 2} normal incidence heat flux. Thus, it is still necessary to carefully design a monochromator that provides acceptable performance under these heat loads. A contact-cooled u-shaped monochromator may be used in this case. The main feature of the u-shaped monochromator is that, by carefully selecting the geometry and cooling locations, is passively corrects for some of the thermally induced crystal distortions. We present experimental and computational results of a contact cooled u-shaped monochromator tested on an APS undulator beamline. The results are encouraging and compare favorably with liquid-gallium internally cooled crystals.
Date: September 1, 1997
Creator: Lee, W.K.; Fernandez, P.B. & Khounsary, A.
Partner: UNT Libraries Government Documents Department

High-heat-load synchrotron tests of room-temperature, silicon crystal monochromators at the CHESS F-2 wiggler station

Description: This note summarizes the results of the single crystal monochromator high-heat-load tests performed at the CHESS F-2 wiggler station. The results from two different cooling geometries are presented: (1) the ``pin-post`` crystal and (2) the ``criss-cross`` crystal. The data presented were taken in August 1993 (water-cooled pin-post) and in April 1995 (water- and gallium-cooled pin-post crystal and gallium-cooled criss-cross crystal). The motivation for trying these cooling (or heat exchanger) geometries is to improve the heat transfer efficiency over that of the conventional slotted crystals. Calculations suggest that the pin-post or the microchannel design can significantly improve the thermal performance of the crystal. The pin-post crystal used here was fabricated by Rocketdyne Albuquerque Operations. From the performance of the conventional slotted crystals, it was thought that increased turbulence in the flow pattern may also enhance the heat transfer. The criss-cross crystal was a simple attempt to achieve the increased flow turbulence. The criss-cross crystal was partly fabricated in-house (cutting, etching and polishing) and bonded by RAO. Finally, a performance comparison among all the different room temperature silicon monochromators that have been tested by the APS is presented. The data includes measurements with the slotted crystal and the core-drilled crystals. Altogether, the data presented here were taken at the CHESS F-2 wiggler station between 1991 and 1995.
Date: September 8, 1995
Creator: Lee, W.K.; Fernandez, P.B.; Graber, T. & Assoufid, L.
Partner: UNT Libraries Government Documents Department

High-heat-load studies of silicon and diamond monochromators using the APS/CHESS prototype undulator

Description: The results of the latest high-heat-load studies made on the APS/CHESS prototype undulator are summarized. Four different crystals were tested: two slotted, symmetrically cut silicon crystals and a core-drilled, asymmetrically cut silicon crystal and a diamond crystal that was jet cooled using water. The purpose of the silicon crystal tests was to reevaluate the surface power loading at which appreciable degradation of the diffraction efficiency was observed. The diamond tests, allotted only a brief period of time during the testing period, were our first attempt at using diamonds for high-heat-flux x-ray monochromators and were performed primarily to gain first-hand experience with diamond monochromators. Measurements with the silicon crystal at 5 keV reconfirmed our previous measurements of performance degradation at around 4-6 watts/mm{sup 2} using liquid gallium with slotted coolant channels. A value of only 2 watts/mm{sup 2} was observed to cause a degradation of the diffraction performance at 15 keV with the same crystals due to the increased sensitivity to strain because of the reduced Darwin widths. The performance of the asymmetric crystal, with its core-drilled coolant channels, was not found to be as good as that of the slotted crystals. This was probably due to poorer heat transfer properties of the core-drilled geometry in combination with the narrowing of the rocking curves because of the asymmetric cut. Fabrication issues for construction of the gallium-cooled crystals is also discussed. Although the diamonds were only successfully tested at low total power the results were very encouraging and motivated us to accelerate our program on the use of diamonds for high-heat-load monochromators.
Date: September 16, 1994
Creator: Mills, D.M.; Lee, W.K.; Smither, R.K. & Fernandez, P.B.
Partner: UNT Libraries Government Documents Department

A ray-tracing study of inclined double-crystal monochromators

Description: Third generation synchrotron X-ray sources such as the Advanced Photon Source (APS) under construction at Argonne National Laboratory will place severe heat load demands on the first beamline optical element. A cooled, inclined double-crystal monochromator is one of the methods being developed at the APS to handle these high heat loads while retaining the brilliance of the source. Using a modified version of the 1989 VAX/VMS SHADOW code, the authors examine the properties of the exit beam for two inclined double-crystal monochromator geometries.
Date: December 1, 1993
Creator: Blasdell, R. C.; Macrander, A. T. & Lee, W. K.
Partner: UNT Libraries Government Documents Department

A finite element analysis of room temperature silicon crystals for the Advanced Photon Source bending-magnet and insertion-device beams

Description: The third generation of synchrotron radiation sources, such as the Advanced Photon Source (APS), will provide users with a high brilliance x-ray beam with high power and power densities. In many cases, the first optical component to intercept the x-ray beam is a silicon-crystal monochromator. Due to extreme heat loading, the photon throughput and brilliance will be severely degraded if the monochromator is not properly designed (or cooled). This document describes a series of finite element analyses performed on room temperature silicon for the three standard APS sources, namely, the bending magnet, Wiggler A, and Undulator A. The modeling is performed with the silicon cooled directly with water or liquid gallium through rectangular channels. The temperature distributions and thermally induced deformations are presented.
Date: August 1, 1994
Creator: Assoufid, L.; Lee, W. K. & Mills, D. M.
Partner: UNT Libraries Government Documents Department

Misalignment sensitivity of an inclined crystal monochromator

Description: The sensitivity of a novel inclined crystal monochromator design to misalignments has been calculated, and compared to data. Rocking curve line narrowing as well as broadening can occur because the asymmetry factor of dynamical diffraction given by b=s{sub O}{center_dot}n/s{sub H}{center_dot}n can have an absolute value larger or smaller than unity. Here s{sub O}{center_dot}n and s{sub H}{center_dot}n are the direction cosines of the incident and diffracted beams, respectively, and n is the inward surface normal. An inclined double crystal monochromator which is perfectly aligned would have b = {minus}1 for both crystals, and only then would the diffraction by symmetric. We have computed b and rocking curve widths for inclination angles of 70.53{degree} and 85.00{degree}, and we compare the 70.53{degree} case to data for silicon {l_brace}111{r_brace} reflections using 8 KeV (CuK{alpha}{sub 1}) radiation. The 70.53{degree} case applies to (11{bar 1}) reflection from a (111) oriented crystal. We report that rotations around the reciprocal lattice vector have the expected effect on b.
Date: October 1, 1991
Creator: Macrander, A. T. & Lee, W. K.
Partner: UNT Libraries Government Documents Department

Brilliance and flux reduction in imperfect inclined crystals

Description: The inclined crystal geometry has been suggested as a method of reducing the surface absorbed power density of high-heat-load monochromators for third-generation synchrotron radiation sources. Computer simulations have shown that if the crystals are perfectly aligned and have no strains then the diffraction properties of a pair of inclined crystals are very similar to a pair of conventional flat crystals with only subtle effects differentiating the two configurations. However, if the crystals are strained, these subtle differences in the behavior of inclined crystals can result in large beam divergences causing brilliance and flux losses. This manuscript elaborates on these issues and estimates potential brilliance and flux losses from strained inclined crystals at the APS.
Date: January 1, 1996
Creator: Lee, W.K.; Blasdell, R.C.; Fernandez, P.B.; Macrander, A.T. & Mills, D.M.
Partner: UNT Libraries Government Documents Department

Experimental results with cryogenically cooled, thin, silicon crystal x-ray monochromators on high-heat-flux beamlines

Description: A novel, silicon crystal monochromator has been designed and tested for use on undulator and focused wiggler beamlines at third-generation synchrotron sources. The crystal utilizes a thin, partially transmitting diffracting element fabricated within a liquid-nitrogen cooled, monolithic block of silicon. This report summarizes the results from performance tests conducted at the European Synchrotron Radiation Facility (ESRF) using a focused wiggler beam and at the Advanced Photon Source (APS) on an undulator beamline. These experiments indicate that a cryogenic crystal can handle the very high power and power density x-ray beams of modem synchrotrons with sub-arcsec thermal broadening of the rocking curve. The peak power density absorbed on the surface of the crystal at the ESRF exceeded go W/mm{sup 2} with an absorbed power of 166 W, this takes into account the spreading of the beam due to the Bragg angle of 11.4{degrees}. At the APS, the peak heat flux incident on the crystal was 1.5 W/mA/mm{sup 2} with a power of 6.1 W/mA for a 2.0 H x 2.5 V mm{sup 2} beam at an undulator gap of 11.1 mm and stored current up to 96 mA.
Date: August 1, 1996
Creator: Rogers, C.S.; Mills, D.M.; Lee, W.K.; Fernandez, P.B. & Graber, T.
Partner: UNT Libraries Government Documents Department

Contact-cooled U-monochromators for high heat load x-ray beamlines

Description: This paper describes the design, expected performance, and preliminary test results of a contact-cooled monochromator for use on high heat load x-ray beamlines. The monochromator has a cross section in the shape of the letter U. This monochromator should be suitable for handing heat fluxes up to 5 W/square millimeter. As such, for the present application, it is compatible with the best internally cooled crystal monochromators. There are three key features in the design of this monochromator. First, it is contact cooled, thereby eliminating fabrication of cooling channels, bonding, and undesirable strains in the monochromator due to coolant-manifold-to-crystal-interface. Second, by illuminating the entire length of the crystal and extracting the central part of the reflected beam, sharp slope changes in the beam profile and thus slope errors are avoided. Last, by appropriate cooling of the crystal, tangential slope error can be substantially reduced.
Date: December 31, 1996
Creator: Khounsary, A.; Yun, W.; Trakhtenberg, E.; Xu, S.; Assoufid, L. & Lee, W.K.
Partner: UNT Libraries Government Documents Department

Test results of a diamond double-crystal monochromator at the advanced photon source

Description: We have tested the first diamond double-crystal monochromator at the Advanced Photon Source (APS). The monochromator consisted of two synthetic type lb (111) diamond plates in symmetric Bragg geometry. We tested two pairs of single-crystal plates: the first pair was 6 mm by 5 mm by 0.25 mm and 6 mm by 5 mm by 0.37 mm; the second set was 7 mm by 5.5 mm by 0.44 mm. The monochromator first crystal was indirectly cooled by edge contact with a water-cooled copper holder. We studied the performance of the monochromator under the high-power x-ray beam delivered by the APS undulator A. We found no indication of thermal distortions or strains even at the highest incident power (280 watts) and power density (123 W/mm{sup 2} at normal incidence). The calculated maximum power and power density absorbed by the first crystal were 37 watts and 16 W/mm{sup 2} respectively. We also compared the maximum intensity delivered by the diamond monochromator and by a silicon (111) cryogenically cooled monochromator. For energies in the range of 6 to 10 keV, the flux through the diamond monochromator was about a factor of two less than through the silicon monochromator, in good agreement with calculations. We conclude that water-cooled diamond monochromators can handle the high-power beams from the undulator beams from the undulator beamlines at the APS. As single-crystal diamond plates of larger size and better quality become available, the use of diamond monochromators will become a very attractive option.
Date: June 1, 1997
Creator: Fernandez, P.B.; Graber, T.; Krasnicki, S. & Lee, W.K.
Partner: UNT Libraries Government Documents Department

Cryogenically cooled monochromator thermal distortion predictions.

Description: Silicon crystal monochromators at cryogenic temperatures have been used with great success at third-generation synchrotrons radiation sources. At the Advanced Photon Source (APS) the unique characteristics of silicon at liquid nitrogen temperatures (77 K) have been leveraged to significantly reduce the thermally induced distortions on beamline optical components. Finite element simulations of the nonlinear (temperature-dependent material properties) thermal stress problem were performed and compared with the experimental measurements. Several critical finite element modeling considerations are discussed for their role in accurately predicting the highly coupled thermal and structural response of the optical component's surface distortion to the high thermal heat flux. Depending on the estimated convection heat transfer coefficient, the final refined finite element model's predictions correlated well with the experimental measurements.
Date: October 29, 1999
Creator: Tajiri, G.; Lee, W.-K.; Fernandez, P.; Mills, D.; Assoufid, L. & Amirouche, F.
Partner: UNT Libraries Government Documents Department

Identification of root cause of vibration of a liquid-gallium-cooled silicon monochromator and recommendations for abatement

Description: Perfect single crystals of silicon are used to monochromate the high-intensity X-ray beams in the Advanced Photon Source at Argonne National Laboratory. Depending on the crystal geometry and the insertion device, the crystal may absorb anywhere from several hundred watts to in excess of a thousand watts. To minimize the thermal distortions in the crystal, this heat must be efficiently removed. Several approaches to this problem are being developed at the APSP including the use of inclined-crystal geometries, cryogenic cooling, liquid-gallium cooling, thin crystals, and the use of diamond. Most of these approaches require coolant flow within the crystals themselves. One issue of concern is the flow-induced vibrations. Two series of tests were performed earlier for a near-prototypical gallium-cooled crystal. This LS note describes a series of tests to measure the general vibration response characteristics of a complete liquid-gallium-cooled inclined-crystal monochromator system.
Date: August 1, 1994
Creator: Chen, S.S.; Zhu, S.; Wambsganss, M.W.; Jendrzejczyk, J.A. & Lee, W.K.
Partner: UNT Libraries Government Documents Department

Smelting Associated with the Advanced Spent Fuel Conditioning Process

Description: The smelting process associated with the advanced spent fuel conditioning process (ACP) of Korea Atomic Energy Research Institute was studied by using surrogate materials. Considering the vaporization behaviors of input materials, the operation procedure of smelting was set up as (1) removal of residual salts, (2) melting of metal powder, and (3) removal of dross from a metal ingot. The behaviors of porous MgO crucible during smelting were tested and the chemical stability of MgO in the salt-being atmosphere was confirmed.
Date: October 3, 2004
Creator: Hur, J-M.; Jeong, M-S.; Lee, W-K.; Cho, S-H.; Seo, C-S. & Park, S-W.
Partner: UNT Libraries Government Documents Department

High heat load performance of an inclined crystal monochromator with liquid gallium cooling on the CHESS-ANL undulator

Description: Results for the performance of a novel double crystal monochromator subjected to high heat loads from an APS prototype undulator at the Cornell High Energy Synchrotron Source (CHESS) are presented. The monochromator was designed to achieve symmetric diffraction from asymmetric planes to spread out the beam footprint thereby lowering the incident power density. Both crystals had (111) oriented surfaces and were arranged such that the beam was diffracted from the (11{bar 1}) planes at 5 KeV. Rocking curves with minimal distortion were obtained at a ring electron current of 96 mA. This corresponded to 370 Watts total power and an peak power density of 48 Watts/mm{sup 2} normal to the incident beam. These results are compared to data obtained from the same crystals in the standard geometry (diffracting planes parallel to surface). The footprint area in the inclined case was three times that of the standard case. We also obtained rocking curve data for the {l_brace}333{r_brace} reflection at 15 KeV for both standard and inclined cases, and these data also showed a minimal distortion for the inclined case. In addition, thermal data were obtained via infrared pyrometry. Not only the diffraction data but also the thermal data revealed a dramatically improved performance for the inclined crystal case.
Date: November 1, 1991
Creator: Macrander, A. T.; Lee, W. K.; Smither, R. K.; Mills, D. M.; Rogers, S. & Khounsary, A.
Partner: UNT Libraries Government Documents Department

On the nature of bulk electrical relaxation in silicate glasses

Description: Three sodium and mixed-alkali silicate glasses were studied to separate bulk relaxation processes from those due to electrode blocking. Conductance, G, and capacitance, C, were measured as a function of frequency over a wide range of temperature. Electrode effects were separated by their dependence on the type of electrode and sample thickness. We found no evidence for a bulk relaxation loss peak but the residual bulk process took the form of the well-known universal'' behavior involving power-law dependence of both G and C, with a fractional exponent, s, close to 0.6. The corresponding relaxation time has precisely the same activation energy as the dc conductivity. By extending the measurements to low temperatures, we find that s becomes equal to unity at the lower temperatures. 12 refs., 3 figs., 1 tab.
Date: January 1, 1991
Creator: Lee, W.K.; Aronson-Unger, S.; Liu, J.F.; Nowick, A.S. (Columbia Univ., New York, NY (United States). School of Mines) & Jain, H. (Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science)
Partner: UNT Libraries Government Documents Department