A Small and Very Sensitive Titanium Pressure Gauge for 3He Melting Pressure Measurements in Magnetic Field

To measure the growth and melting mechanisms of solid 3He in magnetic field in the two magnetically ordered phases we need to measure the deviation from the equilibrium melting pressure very precisely. The measurements are in the temperature range below the Neel transition, and in a magnetic field up to 9 T. We adapted the Straty‐Adams type design of Miura et al. [Rev. Sci. Instr. 64, 3215 (1993)], who were the first to use titanium as material for the membrane. Titanium has a very high quality factor, is very suitable for use in magnetic field, and is not poisonous like beryllium. Our membrane has a diameter of 14 mm, and the overall outer diameter is 22 mm and 19 mm in height. The pressure gauge is sealed with indium, since an epoxy seal on titanium turned out to be very unreliable. The motion of the membrane is read out capacitively, and we have reached a sensitivity up to 14 pF/bar near the melting pressure.