Acoustic properties of an amorphous silica oscillator at mK temperatures

• Published in: Journal of low temperature physics Vol. 134; no. 1-2; pp. 407 - 412
• Main Authors: NAZARETSKI, E, MERITHEW, R. D, POHL, R. O, PARPIA, J. M
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Heidelberg Springer 2004
• Subjects: Acoustical properties of solids; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Mechanical and acoustical properties of condensed matter; Physics; Stochastic model; Inorganic compounds; Tunnel effect; Elasticity; Amorphous state; Torsional vibration; Background noise; Particle detection; Non linear oscillator; Composite materials; Acoustic properties; Gamma radiation; Silicon oxides; Application
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1023/B:JOLT.0000012587.81942.09

We have studied the acoustic behavior of an a-SiO2 composite torsional oscillator in the temperature range between 1 and 100 mK. At higher temperatures, the acoustic properties of amorphous solids are well described by the 'tunneling model'. However, below 10 mK it was found that the resonance exhibited a non-Lorentzian shape and was highly distorted by random 'noise'. We attribute this stochastic noise - 'transients' to interactions of a-SiO2 with ambient gamma quanta present in the laboratory. By shielding the cryostat with a 5 cm thick lead wall we were able to reduce the number of transients. On the other hand, a deliberately introduced 6.1(sup mu)Ci(sup 22)Na source of gamma radiation caused the opposite effect. We interpret the transients in the framework of local heating caused by the interaction between photons and amorphous SiO2 which changes the elastic properties of the oscillator. Our findings have potential applications for particle detection.