Marcello Celasco

Crackling noise peaks as signature of avalanche correlation

Until now, all existing theories failed to explain peaks in the power noise spectra. Here we focus on the role of correlation among avalanches as the main source of the noise peaks observed. The present theory is based on first principles statistics of elementary events clustered in time-amplitude correlated avalanches. A noise spectral power master equation suitable to explain any peaked noise spectra is analytically achieved. Excellent agreement with our noise experiments in superconductors and with recent experiments in Escherichia coli, in single DNA molecule, and in single electron tunneling is reported.

Correlated avalanches in Transition Edge Sensor noise power spectra

The peaked structures of the excess noise observed in many superconducting transition edge sensors are analyzed in both the normalized resistance and the frequency domains. In the framework of our dynamical percolation model we find high amplitude noise peaks in the low normalized resistance range (0.2 approximately) and of much lower amplitude in the high normalized resistance range (0.8), but no peaks are obtained in the power noise spectra in the very wide frequency range explored. The excess noise peaks experimentally explored are accounted for quantitatively by our statistical model of correlated avalanches. Our preliminary experimental noise results on a Ir thin film sensor are compared with literature results.

Study of dendritic avalanches by current noise measurements in High Tc Superconductors

Spectral noise power measurements are reported in a bulk YBa2Cu3O7−δ superconductor at 4.2 K to investigate the flux vortex avalanche processes originated from thermomagnetic instabilities in an applied magnetic field up to 600 mT and in feeding current close to the critical value. 1/fγ behavior is shown at frequencies below 10 Hz, γ values range from 0.7 to 1.7. A sharp peak is observed in applied field and from these results we have obtained a cutoff frequency around 20 Hz for Lorentzian shape knee from which we estimate a mean number of 500 vortices and a mean velocity of about 20 cm/s for the average avalanche.

A Study of the Excess Noise of Ir Transition Edge Sensors in the Frame of Statistical Models

Experiments on superconducting transition properties and power noise density experiments are performed in Ir-based transition edge sensors samples prepared by magnetron sputtering and by laser ablation techniques. The experimental temperature dependence of the resistive-superconducting transitions are compared and analyzed in terms of percolating models. Broad excess noise peak of low amplitude is detected close to the superconductive state and explained by the correlated avalanche theory.

AVALANCHE CORRELATION IN POWER SPECTRA WITH WIDE PEAKS

The occurrence of wide peaks in the frequency range spanning fifteen decades from mHz to above THz was reported in the power spectra of many natural systems. Mostly, these spectral peaks appear superimposed to the 1/f noise. Actually, two different types of spectral peaks were picked out: a first type characterized by wide peaks and high 1/f slope of the overall spectral behavior, the second one by narrow peaks spanning less than one frequency decade and low slopes. Here we highlight the role of correlation among avalanches as the main source of the wide noise peaks observed. The present theory is based on first principle statistics of elementary events clustered in time-amplitude correlated avalanches. A spectral power master equation suitable to explain peaked noise spectra arising from avalanche correlations is achieved analytically. Excellent agreement with our experiments in superconductors and many other observations in biological and natural systems are reported. Our statistical model shows that avalanche correlation gives wide peaks in the power spectrum superimposed to the 1/f behavior with high slope, a typical signature of avalanche processes.

A phenomenological explanation of TES excess noise

The evidence of excess noise in the power spectrum of many natural systems that span over the mHz to the THz, such as biological system, superconductors at dendritic regime, Barkhausen noise of magnetic system and plasma emission from nanometric transistors, was observed and related to a class of statistical models of correlated processes. Intrinsic or induced fluctuations of the elementary processes taking place in transport phenomena couple each other giving rise to time-amplitude correlated avalanches. TES sensors for X-ray microcalorimeters have shown a clear evidence that this excess noise has typical spectral behavior spanning from 100 Hz to 10 kHz. We present an analysis of the excess noise using this statistical avalanche model of TES operating on Si substrate and suspended SiN membrane.

Avalanche correlation in power spectra

Outstanding topic on noise phenomena is the occurrence of peaks in the wide frequency range from mHz to above MHz in the power spectra of many natural systems. Recently, the challenging interest has oriented to focus the spectral peaks superimposed to the 1/f noise. Until now, all existing theories failed to explain peaked spectra. Here we highlight the role of correlation among avalanches as the main source of the noise peaks observed. The present theory is based on first principle statistics of elementary events clustered in time-amplitude correlated avalanches. A spectral power master equation suitable to explain peaked noise spectra arising from avalanche correlations is achieved analytically. Excellent agreement with our experiments in superconductors and with experiments in Escherichia coli, in single DNA molecule and in single electron tunneling is reported. Our statistical model shows that avalanche correlation gives wide peaks in the power spectrum superimposed to the 1/f behavior with high slope, a typical signature of avalanche processes.