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.
Highlights
It is essential during the commissioning and operation of any modern accelerator facility to measure and track the emittance of the propagating beams
In the antiproton decelerator (AD) [1,2] and the newly commissioned extra low energy antiproton ring (ELENA) [3,4,5], antiproton beams experience an adiabatic blowup of emittance during deceleration, which must be monitored and counteracted before extraction to experiments
The simulation comparison highlights an asymmetry in the noncooling cumulative density function (CDF), a characteristic observed previously when exploring the effects of a correlation between emittance and longitudinal momentum offset [12], which is investigated
Summary
It is essential during the commissioning and operation of any modern accelerator facility to measure and track the emittance of the propagating beams. If the scraper blade moves slowly enough, the corresponding shower intensity is proportional to the maximum oscillation amplitude density of the particles at the position of the scraper blade. In the AD system, the CDF is used to obtain an estimate for the distance between the region containing 95% of the beam and beam core (0% intensity in CDF), σ95 This quantity is converted to the 95% emittance with ε95 1⁄4 σ295=β, where β is the transverse beta function at the scraper corresponding to the scraping direction, x or y. Non-Gaussian transverse beam distributions resulting from deceleration and electron cooling present further challenges in extracting accurate emittance estimates from obtained signals. The two-scan algorithm provides an insight into a correlation between the emittance and momentum offset of beam particles
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