  Measurements of polarized electron-nucleon scattering can be realized at the
TESLA linear collider facility with projected luminosities that are about two
orders of magnitude higher than those expected of other experiments at
comparable energies. Longitudinally polarized electrons, accelerated as a small
fraction of the total current in the e+ arm of TESLA, can be directed onto a
solid state target that may be either longitudinally or transversely polarized.
A large variety of polarized parton distribution and fragmentation functions
can be determined with unprecedented accuracy, many of them for the first time.
A main goal of the experiment is the precise measurement of the x- and
Q^2-dependence of the experimentally totally unknown quark transversity
distributions that will complete the information on the nucleon's quark spin
structure as relevant for high energy processes. Comparing their Q^2-evolution
to that of the corresponding helicity distributions constitutes an important
precision test of the predictive power of QCD in the spin sector. Measuring
transversity distributions and tensor charges allows access to the hitherto
unmeasured chirally odd operators in QCD which are of great importance to
understand the role of chiral symmetry. The possibilities of using unpolarized
targets and of experiments with a real photon beam turn TESLA-N into a
versatile next-generation facility at the intersection of particle and nuclear
physics.
