Control of beam intensity signal and position at NSLS X9

X-ray beam line fluctuation is a common problem at almost all synchrotron beam lines. The vertical and horizontal fluctuations are time dependent and vary in amplitude and frequency at each synchrotron. In many cases the amplitudes of the fluctuations are higher than required by users (±100 μm at the National Synchrotron Light Source). For time resolved X-ray absorption spectroscopy these kinds of amplitudes at noise frequencies are certainly out of proportion to the useful needs of synchrotrons. We have made an attempt to compensate for this noise at the experimental end of the beam line. It has been reduced to ±15 μm on monochromatic beam line X9A and white X-ray beam line X9B. Compensation is basically for low frequencies (<1 Hz) and for the slow drifts of the X-ray beam during a fill. (orig.)