Measuring Beam Sizes and Ultra-Small Electron Emittances Using an X-ray Pinhole Camera

Abstract

A very simple pinhole camera set-up has been built to diagnose the electron beam emittance of the ESRF. The pinhole is placed in the air next to an Al window. An image is obtained with a CCD camera imaging a fluorescent screen. The emittance is deduced from the size of the image. The relationship between the measured beam size and the electron beam emittance depends upon the lattice functions alpha, beta and eta, the screen resolution, pinhole size and photon beam divergence. The set-up is capable of measuring emittances as low as 5 pm rad and is presently routinely used as both an electron beam imaging device and an emittance diagnostic.

X-ray pinhole camera resolution and emittance measurement

“…In Sec. III A we apply expression (8) to the case of a slit, and we show some remarkable general results in normalized variables.…”

“…The diffraction from the square aperture is reduced to the slit aperture by calculating only one integral using expression (8) or (6). Furthermore, the results can be normalized.…”

“…To this end, we simulate convolution of an image (a Gaussian distribution with FWHM Á) with the PSF given by expression (8). Figure 8 compares the relative size of the convolved…”

Wave Optics of Synchrotron Radiation

“…To achieve this goal, we need to know all characteristics of emitted radiation, its intensity distribution, polarization and phase distribution. In particular, the synchrotron radiation wave properties play a major role in conventional diagnostics of electron beams in storage rings (Andersson et al, 2006;Elleaume et al, 1995;Fang et al, 1996;Flanagan et al, 1999;Hs & Huang, 1993;Weitkamp et al, 2001). In this case, the image of the electron beam is formed by an optical lens.…”

The Spear 3 Diagnostic Beamlines

“…Due to the relatively short pulse lengths and diffraction effects, however, the measurements can be challenging and require signal deconvolution to extract the desired information. For emittance measurements, xray pinhole cameras [4] were the instrument of choice until the emergence of the 2-slit optical interferometer [5]. Direct imaging in the visible regime is also possible with modern equipment [6].…”