Propagating Ultrasound in Oscillating Quantum Solid 4HeHarry Kojima, Rutgers University New Brunswick, DMR 1005325 • Goal: To understand mechanical response of quantum solid 4He below 1 K. How does the torsional oscillation response depend on the dislocation defects present in solid 4He? • Idea: Use ultrasound propagation as a non-destructive tool to characterize solid 4He samples in situ and simultaneously measure the torsional oscillation of the solid 4He sample. Fig. 1. Exposed schematic view of ultrasound system mounted into torsional oscillator. (a)torsion rod, (b) 10 MHz quartz transducers, (c)sample chamber, (d)electrical contacts, (e)electrode for torsional oscillation, (f)mounting flange, (g)transducer electrical leads, (h)sample fill tube Fig. 2 Preliminary results: Fig. 2 shows preliminary data from 1009 Hz torsional oscillator. Panel (a) shows the expected “supersolid” effect due to possible decrease in moment of inertia below 150 mK. Panels (b) and (c) show the simultaneously measured changes in the ultrasound velocity and attenuation, respectively. The acoustic data above 100 mK can be described in terms of dislocation line motion. New acoustic anomalies appear below 100 mK. Possible relationship between the anomalies and the torsional oscillator frequency shift is under investigation.
Propagating Ultrasound in Oscillating Quantum Solid 4HeHarry Kojima, Rutgers University New Brunswick, DMR 1005325 ParthJariwala (senior engineering major) and Rebecca Cebulka (junior physics major) collaborated to design and construct a triple compound oscillator for studying frequency dependent response of solid 4He to torsional oscillation. Rebecca received a departmental summer internship award to continue her work on the triple compound oscillator. Michelle Goffreda (high school student) is participating in research during the 2012 summer. ParthJariwala, third from right below, is demonstrating low temperature effects at the Rutgers Open House Day. Rebecca Cebulka, center above, explains her work to a graduate student and Jennifer Yu (former research participant in the PI’s lab) at the Rutgers University Aresty Undergraduate Research Symposium.