Author: Stancari, G.
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MOP09 HL-LHC Beam Dynamics with Hollow Electron Lenses 59
  • P.D. Hermes, R. Bruce, R. De Maria, M. Giovannozzi, A. Mereghetti, D. Mirarchi, S. Redaelli
    CERN, Geneva, Switzerland
  • G. Stancari
    Fermilab, Batavia, Illinois, USA
  Each of the two proton beams in the High-Luminosity Large Hadron Collider (HL-LHC) will carry a total energy of 720 MJ. One concern for machine protection is the energy stored in the transverse beam tails, estimated to potentially reach up to 5% of the total stored energy. Several failure scenarios could drive these tails into the collimators, potentially causing damage and therefore severely affecting operational efficiency. Hollow Electron Lenses (HEL) were integrated in the HL-LHC baseline to mitigate this risk by depleting the tails in a controlled way. A hollow-shaped electron beam runs co-axially to the hadron beam over about 3 m, such that halo particles at large amplitudes become unstable, while core particles ideally remain undisturbed. Residual fields from e-beam asymmetries can, however, induce emittance growth of the beam core. Various options for the pulsing of the HEL are considered and are compared using two figures of merit: halo depletion efficiency and core emittance growth. This contribution presents simulations for these two effects with different HEL pulsing modes using the final HL-LHC optics, that was optimized at the location of the lenses.  
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About • Received ※ 06 October 2021 — Revised ※ 02 November 2021 — Accepted ※ 22 November 2021 — Issue date ※ 19 January 2022
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Experimental Demonstration of Optical Stochastic Cooling  
  • J.D. Jarvis, D.R. Broemmelsiek, K. Carlson, D.R. Edstrom, D. Franck, V.A. Lebedev, S. Nagaitsev, O. Obrycki, H. Piekarz, A.L. Romanov, J. Ruan, J.K. Santucci, G. Stancari, A. Valishev
    Fermilab, Batavia, Illinois, USA
  • S. Chattopadhyay, A.J. Dick, P. Piot
    Northern Illinois University, DeKalb, Illinois, USA
  • I. Lobach
    University of Chicago, Chicago, Illinois, USA
  Funding: Fermi National Accelerator Laboratory is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Simon van der Meer’s Stochastic Cooling (SC) was vital in the discovery of the W and Z bosons in 1983 as it enabled sufficient accumulation of antiprotons and delivery of the required beam quality*. This execution of the innovative SC concept promptly earned van der Meer a share of the 1984 Nobel Prize in Physics. A terahertz-bandwidth extension of SC was proposed in 1993 by Mikhailichenko and Zolotorev**. This Optical Stochastic Cooling (OSC) used visible or infrared light rather than microwaves and was extended shortly after by Zolotorev and Zholents to the so-called transit-time method of OSC***. The world’s first experimental demonstration of OSC has just concluded at Fermilab’s Integrable Optics Test Accelerator (IOTA) ring. In this presentation, we will describe the OSC concept, the IOTA ring and OSC apparatus and then present the first experimental results for cooling and heating in one, two and three dimensions. We will also describe experimental studies of a single electron interacting with itself via the OSC physics.
* S. van der Meer, CERN-ISR-PO-72-31 (1972)
** A.A.Mikhailichkenko, M.S. Zolotorev, Phys. Rev. Lett. 71 (25), p. 4146 (1993)
*** M. S. Zolotorev, A. A. Zholents, Phys. Rev. E 50 (4), p. 3087 (1994)
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