Abstract. Top-off operations is a quasi-continuous injection mode that increases the flux and brightness of a synchrotron source and improves thermal stability of optical components by maintaining a constant current in the storage ring. Although the increased and constant flux is advantageous for FTIR measurements, the frequent injections (about one every 30 seconds in the ALS case) introduce artifacts into the spectrum by creating spikes in the interferogram data. These spikes are caused by brief beam motion during the injection event. Here, we describe our efforts to minimize the effects of top-off generated interferogram spikes on several FTIR spectrometers. They include using a fast feedback mirror system to correct for beam motion and a gating signal to inhibit interferogram collection during a top-off injection.

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