Target materials
The
properties
of a good target material are:
high number of polarizable nucleons compared to the total amount of nucleons
high polarization degree
short polarization build up time
long relaxation time
good polarization resistance against radiation damage
simple handling and preparation
of the target
For the dynamic nuclear polarization the materials have to be doped with free radicals. Two different ways are usual:
chemical doping (mixing with free radicals like TEMPO, Porphyrexid or Cr-V complexes)
irradiation
in an intensive
electron beam
Established
target materials are Butanol,
Ammonia, Lithium hydrides and their deuterated counterparts. A very
interesting material is HD, because of the maximal content of
polarizable nucleons. In the following pictures the different
target materials are shown: Butanol is chemically doped, Ammonia and
Li-Hydrides are doped in an intensive electron beam at the Bonn
linear accelerator:
 Butanol with Porphyrexide |
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