Lena/TODO

General thoughts

General thoughts/questions

• Try mixed buffer gas cells, with Ne or He instead of most of N2, only have ~10-30 Torr of N2 for quenching It barely matters at the temperatures we use, because we are limited by alkali-alkali spin-destruction collisions anyway. OTS coating seems to be the way to go
• Optical fibers to carry the light back from the cell, to not deal with the photodiodes being close to the sensors
• Have a gradiometer within the same buffer gas cell
• Measure somehow the coating shift for m≠0. It hasn't been done before.
• Try Mx magnetometer in cells with a little bit of quenching gas, will the performance at T≈40°C be any better?
• We don't seem to correct for the distortions made by low-pass filtering due to the magnetometer cell? Replaced the filter,
• We measure the optical rotation to minimize the probe noise. When we measure the field in the main direction of SERF, the prob noise we measure increases when the photodiode becomes misbalanced. We could fix this by adding an additional channel to measure the total probe power.

Companies that make cells

• Precision Glassblowing
• Opthos
• Triad

Companies that make PCBs

• First sensor
• Gold Phoenix PCB

Cell making patent holders

What are the other cell sources? Vitaly Shutov gave me a list of all cell-related patents, because maybe the patent holders make and sell them File:Cell patents.zip (Page 2 also contains atomic-clock-related patents). Patent holders:

Companies

Honeywell

Epson

Seiko

Ricoh

RIRV

Sarnoff

Symmetricom

People

Kitching John, Hollberg Leo, Liew Li Anne, Knappe Svenja, Moreland John, Velichanski Volodja, Robinson Hugh

Lipp Steven, Abeles Joseph, Braun Alan, McBride Sterling, Riganati John, Whaley Ralph, Zanzucchi Peter

Lal Amit, Radhakrishnan Shankar

Riley William, Lutwak Robert

Sync pumped magnetometers for fMCG?

Bison's magnetometer

That's the magnetometer described in G. Bison's thesis.

Magnetometer 1

http://arxiv.org/abs/physics/0406157

Achieved about 60 fT/sqrt(Hz) probe-limited sensitivity, and measured ~300 fT/sqrt(Hz) in Cs cells at 40°C in magnetic shielding in 2 μT field (7kHz). Bandwidth was ~140 Hz, minimal distance between sensors was 3cm.

What can be improved:

1. Coating instead of bare cell with buffer gas
2. Pump and probe should be separate lasers
3. Measure probe polarization rotation instead of power modulation
4. Use synchronous pumping instead of rf coils?
5. Something to improve the bandwidth?

Magnetometer 2

http://link.springer.com/article/10.1007/s00340-003-1120-z

Gradiometer with 4cm distance between the cells. Cells are 20x20mm buffer gas with Cs at 30°C. The gradiometer sensitivity was 2pT/sqrt(Hz) in a partially shielded room (8mm aluminium shielding).

Magnetometer 3

Cs, D1 pump/probe, B = 5 μT (17.5 kHz), intrinsic sensitivity of 100 fT/sqrt(Hz)

(there are several more magnetometers with similar configuration and performance)