Berlin 2005 – wissenschaftliches Programm
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MA: Magnetismus
MA 31: Magnetische Partikel/Cluster II
MA 31.9: Vortrag
Mittwoch, 9. März 2005, 13:00–13:15, TU H1012
Nature of 3He Nuclear-Spin Relaxation on Glass — •Iouri Sobolev1, Werner Heil1, Ernst Otten1, Joerg Schmiedeskamp1, Wolfgang Kilian2, Herbert Rinneberg2, Thorsten Sander-Thoemmes2, Frank Seifert2, Reinhard Kremer3, and Arndt Simon3 — 1Institut fuer Physik, Mainz — 2PTB Berlin — 3MPI fuer Festkoerperforschung , Stuttgart
Relaxation free storage and transport of hyperpolarised 3He gas is a prerequisite for its use as contrast agent in MR imaging of the human lungs. Normally the spin-polarised gas is stored in aluminosilicate glass vessels but relaxation times T1 > 100 h are demanded if one thinks of a central production facility and a distribution network of hyperpolarised gas to the clinics. The nature of 3He relaxation on glasses was investigated quantitatively and will be presented: Using iron-free aluminosilicate glass cells where paramagnetic impurities are less than 30 ppm, the main source of wall relaxation is due to ferromagnetic sites. By means of a SQUID gradiometer the T1-hysteresis of bare glass cells was studied. Furthermore, using arrays of SQUIDs, the location of ferromagentic sites within the cell wall was traced. A numerical MC-simulation of spin-relaxation of 3He atoms diffusing near ferromagnetic sites reproduces the experimental findings. Finally, the ferromagnetic-site induced wall relaxation could be eliminated by means of an appropriate degaussian procedure resulting in measured T1 relaxation times of up to 200 h.