Vertical beam size measurement in the CESR-TA e+e- storage ring using x-rays from synchrotron radiation
Abstract
We describe the construction and operation of an X-ray beam size monitor (xBSM), a device measuring e+ and e- beam sizes in the CESR-TA storage ring using synchrotron radiation. The device can measure vertical beam sizes of 10-100μm on a turn-by-turn, bunch-by-bunch basis at e± beam energies of ~2GeV. At such beam energies the xBSM images X-rays of ɛ≈1-10keV (λ≈0.1-1nm) that emerge from a hard-bend magnet through a single- or multiple-slit (coded aperture) optical element onto an array of 32 InGaAs photodiodes with 50μm pitch. Beamlines and detectors are entirely in-vacuum, enabling single-shot beam size measurement down to below 0.1 mA (2.5×109 particles) per bunch and inter-bunch spacing of as little as 4 ns. At Eb=2.1GeV, systematic precision of ~1μm is achieved for a beam size of ~12μm; this is expected to scale as ∝1/σb and ∝1/Eb. Achieving this precision requires comprehensive alignment and calibration of the detector, optical elements, and X-ray beam. Data from the xBSM have been used to extract characteristics of beam oscillations on long and short timescales, and to make detailed studies of low-emittance tuning, intra-beam scattering, electron cloud effects, and multi-bunch instabilities.
- Publication:
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Nuclear Instruments and Methods in Physics Research A
- Pub Date:
- June 2014
- DOI:
- 10.1016/j.nima.2014.02.040
- arXiv:
- arXiv:1311.6769
- Bibcode:
- 2014NIMPA.748...96A
- Keywords:
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- Physics - Instrumentation and Detectors;
- Physics - Accelerator Physics
- E-Print:
- 35 pages, 62 figures, version published by Nuclear Instruments and Methods in Physics Research A. Nuclear Instruments &