Nuclear Physics AS67 (1994) 655-662 North-Holland zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA NUCLEAR PHYSICS A An absolute standard for 6Li vector analyzing powers * A.J. Mendez, P.V. Green, K.W. Kemper, P.L. Kerr, E.G. Myers, E.L. Reber, B.G. Schmidt Received 9 June 1993 (Revised 21 July 1993) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Abstract Reactions with the spin structure 1’ + 0” --+ O+ +O- have properties which allow an absolute determination of 1 iTI, I via measurement of two of the tensor analyzing powers. Vector analyzing powers of the ‘2C(6ti, cxs)r4N reaction are deduced to accuracies of about 6% from measurements of the tensor analyzing powers Tao and Tr, at I& = 33 MeV. The vector analyzing power in 6ci+4He elastic scattering is measured at I&,,= 6.2 MeV and t?,_,.= 1.50”, establishing a secondary standard convenient for fast monitoring of “Li vector polarization. I. Introduction Determination of the polarization of accelerated nuclear beams has been the subject of much discussion, e.g., see refs. [l-41, since the measurement of analyzing powers of a nuclear reaction requires the knowledge of the polarization of the beam initiating the reaction. Although the on target polarization is often inferred from the operation of the polarized ion source [5,6] and beam transport system 171, a more direct way of obtaining the polarization is to measure it using a nuclear reaction of known analyzing powers, preferabIy one in which the analyzing powers can be calculated from first principles, such as conse~ation of angular momentum and parity. Reactions of the spin-parity structure l++ 0+-t O++ O+ are the only known examples of this type. Unfortunately, the vector analyzing power is identi- cally zero for this spin structure, as is 7’*r, and therefore these reactions can give no information about the vector polarization of the beam. Further, as a conse- quence of the nuclear forces involved, these reactions have prohibitively smah cross sections [3]. However, it has been shown [1,31 that in reactions of the spin-parity structure l++ Of-+ O+t O- the four possible analyzing powers (iTI,, T,,, zyxwvutsrqponmlkjihgfe Tzl, T22) are re- * Work supported by the National Science Foundation and the State of Florida. 0375-9474/94/$07.00 0 1994 - Elsevier Science B.V. All rights reserved &SD1 0375-9474(93IE0427-A