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Efficient production of pions can be achieved by colliding an intense proton beam with a high-Z target. The disruption of targets from their interaction with an intense proton beam needs to be carefully investigated for optimum design of high-power targets. In this work, experiments have been carried out on mercury (Hg) jets as targets, with a focus on the interaction of the jet with an intense proton beam in the presence of an external magnetic field. The primary diagnostics in the experiment employed the technique of back-illuminated laser shadow photography to ``freeze" 
the transient events, with several high speed cameras used to record the images. The performance of the optical 
diagnostic system is presented.

A magnetic field in a mercury jet flow causes induced currents, which produce distortions of the mercury jet. The effects of the Lorentz force induced by the magnetic field and the role of joule damping were investigated for the present problem.

Statistical and qualitative analysis of the data from image processing is presented, as are experimental studies of Hg jet distortion and the dynamic of Hg flow in the magnetic field. It was observed from the experiments that the imposition of a magnetic field suppressed and stabilized the fluctuating motion in the jet when the flow was turbulent and the magnetic Reynolds number was approximately 0.26. Parallel numerical Monte Carlo simulations of energy deposition by proton beams in a similar system are being carried out elsewhere by collaborators on the project. Data on jet shape, trajectory, and proton beam spot size obtained from the present experiments have been incorporated into simulation models. Results on jet disruption, filament velocity, and energy deposition on the Hg target are reported in this work for proton beam intensities up to 30 $\times$ 10$^{12}$ protons per pulse and magnetic field intensities up to 15~T. The feasibility of utilizing a Hg jet as a high-Z target for future particle acceleration is discussed.

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