We studied the performance of a copper pickup coil for high sensitive measurements of ac magnetic fields. The coil was made of Litz wire to revent the skin effect, and was cooled at 77 K to reduce thermal noise. We first obtained an analytical expression for the coil resistance by nalyzing the eddy current loss of the coil. The analytical result explains well the measured dependences of the coil resistance on the frequency, umber of turns of the coil (N), and filament diameter of the Litz wire (df). Next, we show the design of the pickup coil. When appropriate values re selected for N and df, we can expect the magnetic field noise SB 1/2 > 10 fT/Hz1/2 for f > 1 kHz and SB =2 > 2 fT/Hz1/2 for f < 10 kHz for the ickup coil with diameter of 50 mm. The experimental results agreed with the designed values.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)