| Paper | Title | Page |
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| TUCLA02 | Recent Progress in X-Ray Emittance Diagnostics at SPring-8 | 283 |
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Synchrotron radiation in the X-ray range is suitable for non-destructive diagnostics of beam emittance *. Both direct imaging and interferometric techniques can resolve the micrometer-order transverse beam size. The beam emittance is obtained from the measured beam size with the knowledge of the betatron and dispersion functions and the beam energy spread. At the SPring-8 storage ring, we have recently developed two X-ray instruments for emittance diagnostics. The one for a bending magnet source is the X-ray pinhole camera which directly images the beam profile. A pinhole in the atmosphere is composed of combined narrow X-Y slits made of tungsten. A scintillator crystal is used to convert the X-ray beam image to a visible image. The spatial resolution is about 7 micrometers. It is operated for continuous emittance diagnostics and coupling correction of user operation of SPring-8. The other for an undulator source is the X-ray Fresnel diffractometry monitor **. Monochromatic X-rays are cut out by a single slit, and the vertical beam size is deduced from the depth of the central dip in a double-lobed diffraction pattern. Resolving beam size less than 5 micrometers is feasible.
* S. Takano, IPAC2010 WEZMH01, p2392. (2010) ** M. Masaki et al., Phys. Rev. ST Accel. Beams 18, 042802 (2015). |
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Slides TUCLA02 [6.314 MB] | |
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| TUPB020 | Long-Term Stability of the Beam Position Monitors at SPring-8 | 359 |
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At the SPring-8 storage ring, the renewal of BPM electronics in 2006 has improved orbit feedback resolution *. However, a stability issue of the whole BPM system, including the buttons, the cables and the electronics, remains to be settled for long-term stability of the beam orbit. The BPM in the present SPring-8 has gain imbalances among 4 electrode channels, which result in large offsets (~1 mm). The imbalances are routinely corrected in accordance with a beam-based measurement **. But, the offset error increases close to 100 um during the operation, because of the imbalance fluctuations. Major origin of the imbalances is standing waves caused by reflections in BPM cables. As a countermeasure for the imbalance issue, isolators to mitigate the standing waves were equipped. They significantly reduced the imbalances, but not sufficient to completely suppress the imbalance fluctuations. The requirement of stability for the BPM system for the upgrade plan of SPring-8 is going to be more stringent. We started extensive survey to find the sources of fluctuations of the gain imbalances in order to achieve long-term stability of the BPM system applicable to the planned SPring-8 upgrade.
* S. Sasaki, T. Fujita et al., Proc. of the DIAPC 2007, Venice, Italy, (2007) p. 114 ** M. Masaki et al., Proc. of the 11th Symp. on Accel. Sci. and Technol., (1997), p.83. |
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