The design of Optical Stochastic Cooling for IOTA

Abstract

The paper presents a journal version of the Design Report on the Optical Stochastic Cooling experiment to be carried out at IOTA ring in Fermilab later this year. It discusses the theory which experiment is based on, beam parameters, major requirements to the storage ring systems and technical details of the experiment implementation.

"Colliders or Bust"

“…Schematic of the bunched beam stochastic cooling system at RHIC, consisting of "pickups" and "kickers" -and the fibre-optic and microwave links between these two; the 70 GHz microwave links for the longitudinal system are sent on received on the surface, while the fibre-optics links for transverse cooling are integrated in the tunnel 9 (left); comparison of RHIC luminosity as a function of time in the store, without cooling (red), with only longitudinal cooling (brown), 2-D cooling (green), and 3-D cooling (blue). 10 It is exciting that an OSC test has now been set up at FNAL's IOTA facility, 15 and that, here, with an electron beam, 3-dimensional OSC has been demonstrated for the first time in 2021 16,17 (see Fig. 4) -almost 30 years after the initial proposals.…”

Experimental demonstration of optical stochastic cooling

“…momentum spread and r.m.s. transverse emittance (absent OSC) is termed the cooling range, and all particles within this range are effectively damped by OSC 9 . Detuning the optical delay by half a wavelength inverts the cooling and heating zones (Fig.…”

“…In this configuration, the small-amplitude motion becomes unstable, and the particles are antidamped to large amplitudes determined by the balance of the OSC heating and SR damping. The cooling rate and the cooling ranges described here are the essential figures of merit for OSC ( Methods ) 9 .…”

“…Lastly, the short wavelength of the radiation places stringent requirements on the alignment of the optical system and on the synchronization and stability of the bypass timing. For efficient OSC, the PU radiation and beam trajectory in the KU should be aligned to better than about 100 μm and about 100 μrad in transverse position and angle, respectively, and the bypass timing should be synchronized and stable at the subfemtosecond level 9 .…”

“…First proposed nearly 30 years ago, optical stochastic cooling (OSC) replaces the conventional microwave elements of SC with optical-frequency analogues and is, in principle, compatible with any species of charged-particle beam 7 , 8 . Here we describe a demonstration of OSC in a proof-of-principle experiment at the Fermi National Accelerator Laboratory’s Integrable Optics Test Accelerator 9 , 10 . The experiment used 100-MeV electrons and a non-amplified configuration of OSC with a radiation wavelength of 950 nm, and achieved strong, simultaneous cooling of the beam in all degrees of freedom.…”