Spin control and structure of weak nucleon currents in A=8, 12, 20 and 41

The beta-ray angular distributions from purely spin aligned B-12 and N-12 w ere precisely remeasured using a further refined spin-manipulation techniqu e. We determined the amount of a G-parity violating induced tensor form fac tor in a weak axial vector current as 2M f(T)/f(A) = +0.22 +/- 0.05 (stat.) +/- 0.15 (syst.) +/- 0.05 (theor.). The result is consistent with the theo retical prediction in the framework of which induced tensor form factor is proportional to u- and d-quark mass difference. To study the G-parity viola tion in weak nucleon current systematically, we have started to measure the alignment correlation terms of Li-8, B-8, F-20 and Sc-41.