The longitudinal distribution of a beam as it responds to increasing the delay of the radiation. The beam is cooled when the delay is a multiple of the radiation wavelength and heated when it is half a wavelength out of phase. The top plot shows data collected during the IOTA experiment and the bottom plot shows a recreation in elegant.

The scientific reach of a stored beam – for example, the luminosity in a collider -- is limited by deleterious effects that increase the beam’s disorder. These effects can be mitigated by “cooling” the beam, but conventional cooling is ineffective for beams with very high brightness. One approach to cooling very bright beams is “Optical Stochastic Cooling,” in which radiation from the beam is emitted and feedback onto itself in such a way that it reduces the beam’s disorder. Recently, Optical Stochastic Cooling was demonstrated for the first time at Fermilab’s IOTA ring. CBB grad student AJ Dick of NIU contributed to the system used to synchronize the emitted radiation with the beam to sub-optical wavelength precision.  He also implemented a model of OSC in the widely-used particle tracking code, elegant, and simulated IOTA's cooling in detail using this model (see figure).

 The next step is to amplify the emitted light before it rejoins the beam, and CBB’s Matt Andorf, together with colleagues at Fermilab and Argonne National Lab, have developed an initial design. In the longer term, CBB aims to demonstrate cooling on a larger scale at CESR.  A design for the beamline has been completed in BMAD, modeling is complete, and a system for stabilizing the beam developed by CBB grad student Sam Levenson is promising. 

References:

J. Jarvis, V. Lebedev, A. Romanov, D. Broemmelsiek, K. Carlson, S. Chattopadhyay, D. Edstrom, S. Nagaitsev, H. Piekarz, J. Ruan, J. Santucci, G. Stancari & A. Valishev, A. Dick, P. Piot, I. Lobach, "Experimental demonstration of optical stochastic cooling", Nature 608, 287 (2022) 10.1038/s41586-022-04969-7

M. Andorf, W. Bergman, I.  Bazarov, J.  Maxson, V. Khachatryan, D.  Rubin, and S. Wang, "Optical stochastic cooling with an arc bypass in the Cornell Electron Storage Ring", Phys. Rev. Accel. Beams 23, 102801 (2020) [Online] Available: https://doi.org/10.1103/PhysRevAccelBeams.23.102801

S. Wang, M. Andorf, I. Bazarov, W. Bergan, V. Khachatryan, J. Maxson, and D. Rubin, "Simulation of the transit-time optical stochastic cooling process in the Cornell Electron Storage Ring", Phys. Rev. Accel. Beams 24, 064001 (2021) [Online] Available: https://doi.org/10.1103/PhysRevAccelBeams.24.064001