TY - JOUR
T1 - Large-area low-noise seven-channel dc SQUID magnetometer for brain research
AU - Knuutila, Jukka
AU - Ahlfors, Seppo
AU - Ahonen, Antti
AU - Hällström, Jari
AU - Kajola, Matti
AU - Lounasmaa, Olli V.
AU - Vilkman, Visa
AU - Tesche, Claudia
PY - 1987
Y1 - 1987
N2 - The design, construction, and performance of a new high-sensitivity dc SQUID magnetometer, covering a circular area of 93-mm diameter, is described. The device, now used routinely in our brain research, comprises seven asymmetric first-order gradiometers, located on a spherical surface of 125-mm radius and with the symmetry axis tilted 30° with respect to the vertical. The pickup coil diameter is 20 mm, and the channels are separated by 36.5 mm from each other in a hexagonal array. The overall field sensitivity of the system, measured inside our magnetically shielded room, is 5 fT/√Hz, mainly limited by the thermal noise in the radiation shields of the Dewar. The optimization of the coil configuration and the measurement system is discussed in detail, and a system to determine automatically the position and orientation of the Dewar with respect to certain fixed points on the subject's head is described. Finally, some examples of measurements carried out with the new device are given.
AB - The design, construction, and performance of a new high-sensitivity dc SQUID magnetometer, covering a circular area of 93-mm diameter, is described. The device, now used routinely in our brain research, comprises seven asymmetric first-order gradiometers, located on a spherical surface of 125-mm radius and with the symmetry axis tilted 30° with respect to the vertical. The pickup coil diameter is 20 mm, and the channels are separated by 36.5 mm from each other in a hexagonal array. The overall field sensitivity of the system, measured inside our magnetically shielded room, is 5 fT/√Hz, mainly limited by the thermal noise in the radiation shields of the Dewar. The optimization of the coil configuration and the measurement system is discussed in detail, and a system to determine automatically the position and orientation of the Dewar with respect to certain fixed points on the subject's head is described. Finally, some examples of measurements carried out with the new device are given.
UR - http://www.scopus.com/inward/record.url?scp=0011323372&partnerID=8YFLogxK
U2 - 10.1063/1.1139478
DO - 10.1063/1.1139478
M3 - Article
AN - SCOPUS:0011323372
SN - 0034-6748
VL - 58
SP - 2145
EP - 2156
JO - Review of Scientific Instruments
JF - Review of Scientific Instruments
IS - 11
ER -