Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Ionization cooling is essential for realization of Muon Collider, muons beam based neutrino factories and other experiments involving muons. The simplest structure - absorber(s) immersed in alternating solenoidal magnetic field - provides only transverse cooling since the longitudinal motion in the most suitable momentum range (2-300MeV/c) is naturally antidamped. To overcome this difficulty it is proposed to periodically tilt solenoids so that a rotating transverse magnetic field was created. By choosing the phase advance per period above a multiple of 2pi it is possible to ensure that muons with higher momentum make a longer path in the absorber (whether distributed or localized) thus providing longitudinal damping. Basic theory of such channel and results of tracking simulations are presented.
Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Existing codes for accelerator design (e.g. MAD) are not well suited for ionization cooling channels where particles exhibit strongly dissipative and nonlinear motion. A system of Mathematica programs was developed which allows to: 1) find periodic orbit and eigenvectors of the transfer matrix around it with account of (regular part of) ionization losses and feeddown effect from nonlinear fields; 2) compute emittance growth due to scattering and straggling, find equilibrium values (if exist); 3) analyze nonlinear effects such as dependence of tunes and damping rates on the amplitudes, resonance excitation; 4) perform tracking with account of stochastic processes. Underlying theory and application to helical cooling channel are presented.
Fermilab, Batavia
Funding: Work supported by Fermilab, operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Recent advances in the HTS magnet technology and ionization cooling theory have re-launched the interest of the physics community in the realization of a high energy, high luminosity Muon Collider (MC). The large muon energy spread requires large momentum acceptance and the required luminosity calls for beta* in the mm range. To avoid luminosity degradation due to the hour-glass effect, the bunch length must be comparatively small. To keep the needed RF voltage inside feasible limits the momentum compaction factor must be as small as possible. Under these circumstances chromatic effects correction, energy acceptance, dynamic aperture and longitudinal motion stability are main issues of a MC design. In this paper we give an overview of various lattice designs toward a high luminosity, large energy acceptance MC currently under study at Fermilab.
Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Muon collider is a promising candidate for the next energy frontier machine. In order to obtain peak luminosity of the order of 1035/cm2/s in the TeV energy range the beta function at the interaction point should be smaller than 1cm. To obtain correspondingly small bunch length with a reasonable RF voltage (within 1GV) the momentum compaction factor should be smaller than 10-4 in the momentum range ~1%. The lattice design must also provide sufficient dynamic aperture for ~20 microns normalized beam emittance and minimum possible circumference. Together these requirements present a challenge which has never been met before. We offer a solution to this problem which has the following distinctive features: i) chromatic compensation achieved with sextupoles and dispersion generating dipoles placed near the IR quadrupoles (not in a special section), ii) low value of momentum compaction factor obtained by balancing positive contribution from the arcs with negative contribution from the suppressors of the generated in the IR dispersion. Theoretical aspects and various options will be discussed.