A cryogenic magnetic current sensor has been constructed and tested for operation and sensitivity in the ac regime. The sensor is based on a ferromagnetic-core current transformer,coupled to a superconducting-quantum-interference- device (SQUID) current detector. The SQUID electronics provides a voltage output that can be coupled to room temperature signal recovery electronics, such as a lock-in amplifier. Working in liquid helium (4.2 K) the sensor transresistance is about 1.8 Mohm in the audio frequency range; the equivalent input current noise of the sensor, at the frequency of 1 kHz, is a few pAHz−1/2 per unit primary winding turn. A major contribution to the detector noise is the thermal noise of the ferromagnetic core; however, an important excess noise contribution at low frequency is also present. The experiment is intended as a feasibility test towards the realization of high-sensitivity electromagnetic devices, such as current comparators, to be employed in primary current and impedance metrology setups working in the audio frequency range.
A magnetic current sensor with SQUID readout / Callegaro, Luca; Trinchera, BRUNO OTTAVIO; Roncaglione Tet, L.. - (2014), pp. 98-102. (Intervento presentato al convegno 20th IMEKO TC-4 International Symposium tenutosi a Benevento, Italy nel 15-17 September 2014).
A magnetic current sensor with SQUID readout
CALLEGARO, LUCA;TRINCHERA, BRUNO OTTAVIO;
2014
Abstract
A cryogenic magnetic current sensor has been constructed and tested for operation and sensitivity in the ac regime. The sensor is based on a ferromagnetic-core current transformer,coupled to a superconducting-quantum-interference- device (SQUID) current detector. The SQUID electronics provides a voltage output that can be coupled to room temperature signal recovery electronics, such as a lock-in amplifier. Working in liquid helium (4.2 K) the sensor transresistance is about 1.8 Mohm in the audio frequency range; the equivalent input current noise of the sensor, at the frequency of 1 kHz, is a few pAHz−1/2 per unit primary winding turn. A major contribution to the detector noise is the thermal noise of the ferromagnetic core; however, an important excess noise contribution at low frequency is also present. The experiment is intended as a feasibility test towards the realization of high-sensitivity electromagnetic devices, such as current comparators, to be employed in primary current and impedance metrology setups working in the audio frequency range.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
