Novel transverse emittance measurements for electron cooling characterization

Abstract

The extra low energy antiproton ring (ELENA) finished commissioning before the start of CERN’s second long shutdown in December 2018, successfully providing beams to a new experimental zone. In 2021, ELENA will begin distributing cooled 100 keV antiproton beams to all antimatter experiments. To counteract beam blowup due to deceleration, ELENA will employ the use of an electron cooler. Measurements under similar circumstances, such as at the antiproton decelerator at CERN, have shown electron cooling causing non-Gaussian beam profiles. This effect, combined with nonzero dispersion at the location of the scraper in ELENA, presents new challenges in the use of ELENA’s scraper to determine the emittance during the deceleration cycle. Two new scraper algorithms have been developed and used to show the first evidence of significant electron cooling in ELENA, at 650 and 100 keV energy plateaus. The algorithms are capable of estimating the longitudinal momentum spread of the beams and accurately determining emittances for non-Gaussian beams in dispersive regions. Additionally, utilizing combinations of measurements from opposing scraper blades, additional information on the beam’s evolution is presented, suggesting a correlation between the emittance and longitudinal momentum offset of individual particles. Finally, considerations for further studies in ELENA and similar machines are presented.