• J.P. Alexander, C.J. Conolly, E. Fontes, W.H. Hopkins, B. Kreis, H. Liu, A. Lyndaker, M.A. Palmer, D.P. Peterson, P. Revesz, J.J. Savino, R.D. Seeley
  CLASSE, Ithaca, New York
• J.W. Flanagan
  KEK, Ibaraki

Funding: NSF

We report on the performance goals and design of the CESRTA x-ray beam size monitor (xBSM). The xBSM resolution must be sufficient to measure vertical beam sizes under 20um. The xBSM images 2–4keV synchrotron radiation photons onto one-dimensional photodiode array. Instrumentation in the dedicated x-ray beam line includes upstream interchangeable optics elements (slits, coded apertures, and Fresnel zone plates), a monochrometer and the InGaAs photodiode detector. To provide sufficient x-ray flux in 2 GeV operation, the beam line is evacuated, with only a thin diamond window isolating the detector vacuum from the damping ring. The readout is a beam-synchronized FADC that is sufficient to measure consecutive bunches independently in a 4ns bunch spacing configuration.

• J.P. Alexander, W.H. Hopkins, B. Kreis, H. Liu, D.P. Peterson
  CLASSE, Ithaca, New York
• J.W. Flanagan
  KEK, Ibaraki

Funding: NSF

Engineering data sets were collected with the CESRTA x-ray beam size monitor (xBSM) during November 2008 and January 2009 runs. We report on the performance of the InGaAs photodiode array detector, including time response and signal-to-noise. We report on the observed measurement resolution for changes in the damping ring vertical beam size using the interchangeable optics elements: slits, coded apertures, and a Fresnel zone plates. Observed resolutions are compared to predictions based on characteristics of the optics elements.

• J.W. Flanagan, H. Fukuma, S. Hiramatsu, H. Ikeda, K. Kanazawa, T.M. Mitsuhashi, J. Urakawa
  KEK, Ibaraki
• J.P. Alexander, W.H. Hopkins, B. Kreis, M.A. Palmer, D.P. Peterson
  CLASSE, Ithaca, New York
• G.S. Varner
  UH, Honolulu, HI

Funding: Work supported in part by the US-Japan Cooperation Program

We are working on the development of a high-speed x-ray beam profile monitor for high-resolution and fast response for beam profile measurements to be used at CesrTA and SuperKEKB*. The optics for the monitor are based on a technique borrowed from x-ray astronomy, coded-aperture imaging, which should permit broad-spectrum, low-distortion measurements to maximize the observable photon flux per bunch. Coupled with a high-speed digitizer system, the goal is to make turn-by-turn, bunch-by-bunch beam profile measurements. Following initial tests with a low-resolution mask at large beam sizes (vertical size ~200 um), a high-resolution mask has been made for use with low-emittance beams (vertical size ~10 um) at CesrTA. The first performance results of the high-resolution mask on the low-emittance CesrTA beam are presented.

*J.W. Flanagan et al., Proc. EPAC08, Genoa, {10}29 (2008).