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We report on an experimental study of high-speed micro-scale liquid jets ejected into low-pressure environments, which has applications for the use of negative pressure modules in jet injector systems. The jets were impulsively started by the action of a stiff spring-piston and ejected through a narrow orifice, D_{0} ~ 100 μm, into partial vacuums ranging from atmospheric pressure down to -80 kPa. We find that due to the high exit velocity, V_{j} ~ 100 m/s, the main jet stream is largely unaffected, but we reveal some fascinating fine features during the startup phase, largely due to the presence of a small liquid volume pulled through the orifice prior to actuating the jet. In particular, as the pressure decreases, the start-up time increases and the initial spray becomes more pronounced. However, the primary outcome of this feasibility study is that use of negative pressures is viable for jet injector applications, and we hypothesize an optimal range of working pressures and configurations. 

Abstract The search for a dark photon holds considerable interest in the physics community. Such a force carrier would begin to illuminate the dark sector. Many experiments have searched for such a particle, but so far it has proven elusive. In recent years the concept of a low mass dark photon has gained popularity in the physics community. Of particular recent interest is the 8 Be and 4 He anomaly, which could be explained by a new fifth force carrier with a mass of 17 MeV/ c 2 . The proposed Darklight experiment would search for this potential low mass force carrier at ARIEL in the 10-20 MeV/ c 2 e + e − invariant mass range. This proceeding will focus on the experimental design and physics case of the Darklight experiment.