Lena/Nov 2016
November 2016
BACK/NEXT
11/02/2016
Magnetic connectors
It seems like many parts of our magnetometer setup are actually very magnetic. That includes the BNC cables, banana plugs and the circuit boards.
The circuit boards from OSH Park were plated with Ni, and that caused problems.
Replacement non-magnetic connectors:
- BNC plug http://www.mouser.com/ProductDetail/Amphenol-RF/112710/?qs=sPbJEtTr5b45g4lDF9tMFw%3D%3D
- BNC jack http://www.mouser.com/ProductDetail/Amphenol-RF/112740-13/?qs=ZnztrWCQEtE9xZQYo%2FWsjg%3D%3D
- Banana plug http://www.mouser.com/ProductDetail/Pomona-Electronics/3276/?qs=sGAEpiMZZMvdy8WAlGWLcPkjJE6AhYLi
- Banana jack (except the nut) http://www.mouser.com/ProductDetail/Johnson-Cinch-Connectivity-Solutions/108-0903-001/?qs=sGAEpiMZZMuIC3ROaEqRYUclhTyEUpND
- Pin headers http://www.mouser.com/ProductDetail/Molex/22-28-4363/?qs=sGAEpiMZZMs%252bGHln7q6pm%252bS0pk2Wo0XxTAhHStsXU8w%3d
11/07/2016
Pump modulation and noise
We are trying to verify whether the drifts in the pump laser are the reason why our measured magnetic field noise is so large. We have really low probe noise, around 1 fT/sqrt(Hz), and the measured magnetic field noise was consistently higher than 10 fT/sqrt(Hz), especially at the frequency below 10-20 Hz in WIMR. The SQUID measurements suggest that it should be ~5 fT/sqrt(Hz).
We modulated the pump current, which modulated both optical frequency and power at 10 Hz. The change in frequency was ~1 GHz, and the change in power was ~0.02%. It produced a 1.5 pT peak in the magnetic signal. That's 1.5 fT per 1 Mhz, or 20 ppm of optical power change.