High-heat-load synchrotron tests of room-temperature, silicon crystal monochromators at the CHESS F-2 wiggler station (original) (raw)
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Review of Scientific Instruments, 1996
A newly designed, cryogenically cooled, thin Si crystal monochromator was tested at the European Synchrotron Radiation Facility (ESRF) beamline BL3. It exhibited less than 1 arcsec of thermal strain up to a maximum incident power of 186 W and average power density of 521 W/mm2. Data were collected for the thin (0.7 mm) portion of the crystal and for the thick (≳25 mm) part. Rocking curves were measured as a function of incident power. With a low power beam, the Si(333) rocking curve at 30 keV for the thin and thick sections was <1 arcsec FWHM at room temperature. The rocking curve of the thin section increased to 2.0 arcsec when cooled to 78 K, while the thick part was unaffected by the reduction in temperature. The rocking curve of the thin section broadened to 2.5 arcsec FWHM and that of the thick section broadened to 1.7 arcsec at the highest incident power. The proven range of performance for this monochromator has been extended to the power density, but not the absorbed powe...
The article describes the results of Finite Element Analysis (FEA) of the first Si monochromator crystal distortions due to Synchrotron Radiation (SR) heat load and consequent analysis of the influence of the distortions on a double crystal monochromator performance. Efficiencies of two different cooling schemes are compared. A thin plate of Si crystal is lying on copper cooling support in both cases. There are microchannels inside the cooling support. In the first model the direction of the microchannels is parallel to the diffraction plane. In the second model the direction of the microchannels is perpendicular to the diffraction plane or in other words, it is a conventional cooling scheme. It is shown that the temperature field along the crystal volume is more uniform and more symmetrical in the first model than in the second (conventional) one. #
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992
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Journal of Physics: Conference Series, 2013
High-heat-load studies on Si double crystal monochromator that is internally cooled with liquid nitrogen flow were performed as APS-Upgrade planned to increase ring current to 150 mA. The monochromator consists of two separated Si crystals with diffraction surfaces oriented along (111), diffracting vertically to produce a fixed 35 mm beam offset. Rocking curves were measured for the beam footprint on the first crystal lying both above and away from cooling channels. The beam was produced by two collinear APS undulators type A, each 2.4 m long with 3.3 cm period. Most of the data were obtained for a monochromator set to Bragg diffract at 8 keV for the Si (111) reflection. Through the use of aluminium filters between two sequential ion chambers, we also measured the Si (333) reflection diffracting at 24 keV. We measured the FWHM of rocking curves with either one or both undulators tuned so that the energy of the 1 st harmonic matched the Si (111) Bragg energy. Our results show sensitivity to the distance between the beam footprint above and away from cooling channels under high power conditions.
Journal of Synchrotron Radiation, 2000
The successful use of cryogenically cooled silicon monochromators at third-generation synchrotron facilities is well documented. At the Advanced Photon Source (APS) it has been shown that, at 100 mA operation with the standard APS undulator A, the cryogenically cooled silicon monochromator performs very well with minimal (< 2 arcsec) or no observable thermal distortions. However, to date there has not been any systematic experimental study on the performance limits of this approach. This paper presents experimental results on the performance limits of these directly cooled crystals. The results show that if the beam is limited to the size of the radiation central cone then, at the APS, the crystal will still perform well at twice the present 100 mA single 2.4 m-long 3.3 cm-period undulator heat load. However, the performance would degrade rapidly if a much larger incident white-beam size is utilized.
Cryogenically cooled monochromator thermal distortion predictions
AIP Conference Proceedings, 2000
Silicon crystal monochromators at cryogenic temperatures have been used with great success at third-generation synchrotrons radiation sources.l' 2 At the Advanced Photon Source (AI%) the unique chmacteristics 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 nonlhear (temperature-dependent material properties) thermal stress problem were performed and compared with the expetiental 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 finzd refined finite element model's predictions correlated well with the experimental measurements.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1994
A water-cooled monochromator with micro-cooling channels has been tested on a wiggler beamline at the European Synchrotron Radiation Facility. The device consists of a thin silicon wafer bonded to the grooved surface of a thick block of silicon. At low total power (330 W) and high power density (1 .7 W/mm 2) the broadening of the Si 333 rocking curve at 21 keV was less than 1 arc sec when compared with the width at 1 mA. At high total power (1 .4 kW) and low power density (0 .5 W/mm2) the broadening of the 111 reflection at 13 keV was approximately 2.5 arc sec with respect to the low heat-load case .
SPIE Proceedings, 1996
The submitted manuscript has been created by the University of Chicago as Operator of Argonne National Laboratory ("Argonne") under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said artkle to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
Journal of Synchrotron Radiation, 2001
The results of high-heat-load tests of indirectly cryogenically cooled silicon monochromators are presented. The measurements show that, provided that the total power absorbed by the crystal is less than $150 W, indirect cryogenically cooled silicon monochromators will perform well, with thermalinduced slope errors of less than 2 arcsec. At the Advanced Photon Source, this corresponds to the undulator closed-gap (11 mm) condition at 100 mA with white-beam slit sizes slightly larger than the full width at half-maximum of the radiation central cones. The dependence of the slope errors on the thermomechanical properties of silicon are discussed and clearly demonstrated.
A Thermal Exploration of Different Monochromator Crystal Designs
2017
Eight potential monochromator crystal designs were subjected to a combination of three different beam powers on two different footprints. The temperature and thermal deformation were determined for each. It was found that thermal deformation of the lattice is negligible compared to the surface curvature, and that while the thinnest crystal wafer showed the smallest temperature increase, crystals cooled from the bottom alone demonstrated a far more uniform thermal deformation and a larger radius of curvature.