Yesterday was a very long but extremely exciting time in the lab. Hamed has spend the past few days chasing electrical noise and bringing down the background of our piezoelectric sensor. Eventually, Hamed managed to bring the background noise level to about 0.2 V at a 60 dB amplification with a +/- 4V full scale – an excellent value giving us hope to record very small events occurring in our sample. Of course more problems came when we started pressurizing and heating the sample due to A/C and higher frequency noises introduced by the silicon controlled rectifier which is at the core of our heating system. However, both of these noises are at low frequencies and extremely reproducible and therefore were filtered out with a high-pass filter somewhat compromising our detection capabilities. At last, nothing stood in the way of recording about 65 beautiful acoustic emissions during axial compression of Black Hills Quartzite deformed at 1GPa confining pressure and 100˚C. Now the next steps will be further lowering the electrical noise in our system to detect more events, introducing more sensors into the loading column and slowly ramping up the temperature of our experiments – many more exciting nights ahead!
