Beam energy absolute measurement using K-edge absorption spectrometers

A method is presented of absolute energy measurement with an accuracy of ΔE ∼ 10−4E0 by direct measurement of the bend angle in a high-precision mapped magnetic dipole using two opposite-direction short (about 2 mm long) high-field-intensity magnets (Bdipole ⪡ Bshort mag) installed at each end and two K-edge absorption spectrometers. Using these spectrometers and the hard X-ray synchrotron radiation created by the short magnets, a bend angle of 4.5 arc deg for the CEBAF energy bandwidth can be measured with an accuracy of a few units of 10−6 rad, and the main source of systematic errors is the absolute measurement of the field integral.