A6.3 - Magnetic relaxation imaging with a fluxgate sensor scanner
- Event
- SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg - Band
- Proceedings SENSOR 2009, Volume II
- Chapter
- A6 - Magnetic Sensors I
- Author(s)
- D. Ruehmer, E. Heim, A. Hirsch, R. Piel, T. Wawrzik, F. Ludwig, M. Schilling - Technische Universität Braunschweig, Braunschweig, Deutschland
- Pages
- 29 - 33
- DOI
- 10.5162/sensor09/v2/a6.3
- ISBN
- 978-3-9810993-5-5
- Price
- free
Abstract
Fluxgate sensors are among the most sensitive low noise sensors for the magnetic flux density B. We have developed a fluxgate scanner for the 2-dimensional magnetic relaxation imaging of magnetic nanoparticle distributions. In magnetorelaxometry (MRX), the magnetic moments of superparamagnetic nanoparticles are first aligned by an external magnetic field of the order of a few mT, and after switching off the magnetic field the decay of the net magnetic signal is measured. In our setup, we employ a cylindrical wire-wound coil for the magnetization and racetrack fluxgates with a high permeability tape core for the detection. The fluxgate sensor with its electronics is mounted on a stand above the sample to be magnetically imaged. An x-y-table shifts the sample by maximum 200 mm in x-direction and 180 mm in y-direction with a resolution of 100 μm in both directions while typical scan steps are 1mm. The vertical distance of the sensor to the sample amounts to approx. 100 μm. In each point we measure the relaxation of magnetization of the sample to be tested repeatedly, and by displaying the resulting averaged change in magnetization we improve the signal-to-noise ratio. To increase the spatial resolution, data are deconvolved with a point-spread function, estimated from measurements on a pointshaped nanoparticle sample.