High Energy and Nuclear Physics

Neutrino Factory/Muon Collider Target
R. Samulyak, J. Glimm, J. Du



In order to understand the fundamental structure of matter and energy, an advance in the energy frontier of particle accelerators is required. Advances in high-energy particle physics are paced by advances in accelerator facilities. The aim of the multi-institutional research group Neutrino Factory/Muon Collider Collaboration is to explore the feasibility of a high-energy, high-luminosity muon-muon collider and a neutrino factory. For more information, visit the Neutrino Factory/Muon Collider Collaboration home page (http://www.cap.bnl.gov/mumu). However, several challenging technological problems remain to be solved in the collider design in order to achieve potential advantages of greatly increased particle energies over traditional electron-positron machines (linear colliders). One of the most important problems is to create an effective target able to generate high-flux muon beams. The need to operate high atomic number material targets in particle accelerators that will be able to withstand intense thermal shock has led to the exploration of free liquid jets as potential target candidates for the proposed Muon Collider. The target will contain a series of mercury jet pulses of about 1 cm in diameter and 30 cm in length. Each pulse will be shot at a velocity of 30 m/s into a 20 Tesla magnetic field at a small angle to the axis of the magnetic field. When the jet reaches the center of the magnet it will be hit with a 2 ns proton pulse. Every proton pulse will deposit about 100 J/g of energy in the mercury.

Numerical simulations of hydro and MHD processes in the target can reduce the amount of costly experiments and help to optimize target parameters. Such simulations present a challenging problem of computational science. They require mathematical modeling of complex flows undergoing phase transitions (cavitation) and numerical methods for solving MHD equations in complex geometries. Our numerical studies have been performed using FronTier-MHD, a magnetohydrodynamic extension of the front tracking hydro code FronTier. Numerical simulations of the Neutrino Factory/Muon Collider target have already achieved important results. In our previous works, we addressed problems of the interaction of mercury jet with proton pulses, the evolution of Richtmyer-Meshkov instabilities on the jet surface and the jet breakup, stabilizing effect of the magnetic field, and cavitation on mercury caused by strong rarefaction waves. Simulations agreed with experiments carried out at BNL’s Alternating Gradient Synchrotron and at CERN.

We have demonstrated that at the design parameters, the distortion of the jet entering a non-uniform magnetic field is significant, and that reduces the effective cross-section of the interaction with the proton pulse (Figure 2). The study has led to the change of design parameters of the future experiment MERIT. Current work is focused on large-scale 3D MHD simulations of the mercury jet interaction with proton pulses.
 

a)                                                               b) Figure 1. Mercury jet evolution in magnetic fields ranging from 0 to 20 Tesla. a) Evolution of the mercury jet radius. b) Average density profile in the jet cross-section at 130 microseconds.

 

Figure 2. Aspect ratio of the cross-section of the mercury jet entering a 15 Tesla solenoid at three different angles with respect to the solenoid axis. Zero of the longitudinal coordinate corresponds to the center of the 1 meter long solenoid. The jet nozzle is placed inside the solenoid at l = -40 cm in coordinate system.

References

• [1]  Lu, R., Samulyak, R., Prykarpatskyy, Y., Glimm, J., Xu, Z., and Kim, M.N. Comparison of heterogeneous and homogenized numerical models of cavitation. Int. J. Multiscale Comp. Eng. 4(3) (2006).
• [2]  Samulyak, R., Du, J., Glimm, J., and Xu, Z. A numerical algorithm for MHD of free surface flows at low magnetic Reynolds numbers. J. Comp. Phys. Submitted, 2006.
• [3]  Samulyak, R., and Prykarpatskyy, Y. Richtmyer-Meshkov instability in liquid metal flows: influence of cavitation and magnetic fields. Mathematics and Computers in Simulations 65: 431-446 (2004).

Last Modified: January 31, 2008
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