The NH material will be available from the SMC 1996 run but the
LiD
material has to be purchased and prepared for the dynamic nuclear polarization
process.
The paramagnetic centres needed for the polarization are created in these
materials
by irradiation with an electron beam. The ammonia for SMC has been
irradiated with the 20 MeV linac at Bonn and the same will be done with
LiD. For this a bigger irradiation cryostat has to be built.
The paramagnetic
centres in NH
decay during a long-term storage in liquid nitrogen. To
overcome this the material can be stored in liquid helium or re-irradiated
before its use. Negotiations with CERN (M. Rieubland) are needed to find the
most cost-effective solution.
Sources for purchasing of LiD are France, Russia or United States.
Because of
the strategic nature of
LiD contacts from CERN management as well as from
the German authorities are needed in order to import the material to Germany
(where the preparation will be made) and later to CERN for the
COMPASS experiment.
Test irradiations and polarization tests with small samples will be done at
Bonn before preparing all the LiD material.
Table 3.6:
Schedule for the target material preparation.