A fully automated precise measurement system for sound velocity and internal friction in solids down to liquid helium temperatures using the vibrating reed technique

Abstract

The design and fabrication of a fully automated, computer controlled, precise measurement system for sound velocity and internal friction using the vibrating reed technique is described in detail. Relative variation of sound velocity and internal friction has been measured using automatic frequency locking. A detailed description of the apparatus is given. The associated electronics that took care of quite a few problems in getting a good lock-in condition have been highlighted. With a bath cryostat and sample insert, measurements were made down to liquid helium temperatures with a temperature control accuracy better than 10 mK. The resonance frequency and the peak amplitude were recorded as a function of temperature which in turn provided temperature variation of sound velocity and internal friction with a relative accuracy better than 1 part in 10⁴ and 1.5%, respectively. Precise nature of the results obtained using this setup is highlighted for a specimen of an amorphous alloy near it's Curie temperature.