1 / 15

A Portable Ultrasensitive SERF Atomic Magnetometer for Biomagnetic Measurements

A Portable Ultrasensitive SERF Atomic Magnetometer for Biomagnetic Measurements. R Wyllie, 1 Z Li, 2 R Wakai, 3 N Proite, 1 P Cook, 1 T Walker 1. 1 – Department of Physics, UW-Madison 2 – Center for Clinical Neurosciences, UT-Houston Health Science Center

hdoris
Download Presentation

A Portable Ultrasensitive SERF Atomic Magnetometer for Biomagnetic Measurements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. A Portable Ultrasensitive SERF Atomic Magnetometer for Biomagnetic Measurements R Wyllie,1 Z Li,2 R Wakai,3 N Proite,1 P Cook,1 T Walker1 1 – Department of Physics, UW-Madison 2 – Center for Clinical Neurosciences, UT-Houston Health Science Center 3 – Department of Medical Physics, UW-Madison

  2. Requirements for Biomagnetic Measurements • Sensitivity • Bandwidth~100Hz • Portability

  3. Atomic SERF Magnetometer Note: Spin-exchange collisions do not affect G´ Romalis et. al., Nature, 422, 596, 2003

  4. Experimental Concerns • For full SERF sensitivity, precession rate<<spin relaxation rate • Magnetic shielding, careful nulling using Helmholtz coils • Noise Sources • Nonmagnetic, technical noise (e.g. vibrations, thermal fluctuations, etc.) • Johnson noise (thermal electron motion)

  5. Technical Noise from an hot air heated cell scheme

  6. Z-Mode • Goal: use lock-in technique to extract signal from nonmagnetic noise • Apply a large, oscillating ~kHz magnetic field in z-direction (along pump) • For best sensitivity, Larmor frequency~parametric frequency, sets Bz=430nT • Use lock-in detection of signal • Two detection directions • Z1, Sy signal oscillates at wz • Z2, Sx signal oscillates at 2wz • Zero transverse fields produce no signal—background free

  7. Z-Mode Results • Significantly reduces nonmagnetic noise • Retains sensitivity and bandwidth of normal SERF magnetometer operation

  8. Current Setup • Rb 87 with N2 (100T) buffer gases • Circularly polarized pump at 795nm • Linearly polarized probe at ~780nm • Cell heated to 180 C

  9. Technical Improvements • Plastic, ceramic, and Teflon parts reduce Johnson noise, improve portability • Matched resistive film heaters create little magnetic field, allow smaller apparatus, less noise (similar to Kitching et al heating scheme) • RF heating, atoms not affected by high frequency (MHz) fields • Insulation allows subject to be 1cm away from cell • Easy conversion to gradiometer with pump tube

  10. Adult MCG

  11. Acknowledgments This work funded by a grant from the NIH

  12. Collisional Mixing and Pumping

  13. Equations Limits on SS equations

  14. Notes • Sensitivity Bandwidth product independent of species except slowing down factor • Two requirements for ambient fields in SERF scheme • Spin temperature limit – Hyperfine states not well resolved, lots of collisions in this timeframe • High sensitivity limit – spin’s do not precess far before relaxing • Noise reduction using Z-mode • Current Setup • Adult MCG • Sensitivity Bandwidth product independent of species, ~1/q (slowing down factor)

  15. Extra

More Related