Find in Library

Observations of optical synchrotron radiation emitted over millions of passes from a few electrons circulating in the particle accumulator ring at the Advanced Photon Source were performed with a digital CMOS camera and a synchroscan streak camera operating at 117.3 MHz. Discrete changes of integrated counts in the CMOS image region of interest are ascribed to single electron steps in a 10-s sensor integration time. Circulations of a single electron at 375 and at 425 MeV were demonstrated in the 12-bit digital CMOS camera images. The streak camera operating at the 12th harmonic of the fundamental revolution frequency at 9.77 MHz was used to measure the bunch length from 0.5-nC circulating charge down to tens of electrons or <10  aC. The measurements were performed with ∼8-ps temporal resolution uniquely at such ultralow charges. These results also serve as a proof-of-principle longitudinal profile diagnostic for the predicted effects of optical stochastic cooling at low charge in commissioning experiments at the Fermilab Integrable Optics Test Accelerator ring.