| Zugriffsnummer | 20884 |
| Dokumenttyp | Zeitschriftenartikel |
| Sprache | Englisch |
| Titel | Nuclear magnetic precession measured with SQUIDS |
| Autor(in); Institution |
Burghoff, Martin; 8.2, Biosignale, PTB-Berlin
|
| Quelle/Jahr | Pomiary, automatyka, kontrola: 53 (2007), 9, 17 - 20 |
| ISSN | 0032-4110 |
| Verlag | Warszawa: Wyd. Czasopism Techn. NOT |
| Freie Schlagworte | SQUID ; nuclear magnetic precession ; low magnetic field |
| Zusammenfassung | We have developed a superconducting quantum interference devices (SQUID) sys-tem measuring nuclear magnetic precession at very low magnetic fields with a spectral resolution beyond the natural line width of liquids. A coil system applies a magnetic polarization field and a perpendicular static detection field to the sample. The detection system for the very weak magnetic field generated by the precessing nuclei consists of LTc-SQUID sensors in a liquid helium cryostat. We measured the 1H precession signal of benzene, distilled water and chloroform samples at various detection fields. With our set-up, broad band detection of the nuclear magnetic resonance of the investigated liquids with a very high resolution is possible. Benzene showed the narrowest natural resonance line width of 0.12 Hz followed by chloroform of about 0.17 Hz. The observed line widths increased linearly with the detection field with a slope independent of the investigated sample. This increase is attributed to the inhomogeneity of the detection field, rather than to intrinsic prope-ties of the investigated liquids, and thus describes the properties of our measurement system. Reliable low field NMR and MRI depend strongly on field homogeneity of the detection field coils and the residual field inside the magnetically shielded room. At such low fields, high demands on the absolute homogeneity of the static field correspond to very moderate requirements on its relative homogeneity. Reduction of these system parameters and its influence is the prerequisite for a good frequency and spatial re-solution. Here, we investigated our SQUID measurement system and estimated all main system parameters at very low fields below a microtesla. |
