Proton polarization in the 3He(d,p)4He reaction

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ABSTRACT

The proton polarization i n the 3 ~ e ( d , p ) 4He reaction induced by

unpolarized deuterons has been measured a t deuteron lab. energies of 2.0,2.8, 3.9 and 6IIMeV f o r 20 angles between O0 and 150' (c.m.). S t a t i s t i c a l

uncertainties are typically

+

0.01

.

The measurements were made with a proton polarimeter in which the l e f t - r i g h t asymmetry of scattering a t 60° (lab.) i n 4He is determined.

The polarimeter employs "venetian-blind" collimation of the protons by conical vanes and 75 cm2 p l a s t i c s c i n t i l l a t o r detectors. Four detectors are included f o r use i n polarization t r a n s f e r experiments. For 10.5 MeV protons and a helium pressure of 250 p . s . i . the t a r g e t thickness is 3 MeV and the efficiency per detector per unpolarized proton incident i s lo-".

For each polarimeter detector a t r i p l e coincidence w i t h a 15 ns resolving time was required w i t h two s c i n t i l l a t o r transmission detectors preceding the pol arimeter. Spectra of random coincidences were accumulated

simultaneously and subtracted. symmetries resulting from pol arimeter-target misalignment and other geometrical e f f e c t s are discussed. Al 1 resul ts quoted a r e geometric means of pairs of measurements f o r 180° rotation of the

polarimeter and a r e also arithmetic means of such measurements t o l e f t and r i g h t of the 3He target. The absolute analyzing power i s estimated by computer simulation of t r a j e c t o r i e s t o be -0.638

+

0.020 f o r protons entering a t 10.3 MeV.

The product of polarization and cross section is f i t t e d t o an expansion of f irst-order associated Legendre polynomial s using these r e s u l t s and earl i e r measurements. Only four terms a r e required except a t 6,OMeV where a f i f t h i s necessary. The energy dependence of these coefficients suggests resonances i n 5 L i a t deuteron energies of 60MeV (odd coefficients) and 7.5 MeV (even coefficients) i n agreement w i t h r e s u l t s f o r the polarized-beam analyzing powers ('1

.

Comparison of the r e s u l t s w i t h vector-polarized-beam ^(') and pol a r i zed-target analyzing powers shows no evidence f o r the postul a ted simp1 e r e l a t i o n s based on DWBA cal cul ations. Comparison of the results

w i t h recent measurements of the neutron polarization i n the mirror reaction(4) shows no s i g n i f i c a n t differences.

The theory of angular correlations in charged p a r t i c l e reactions is developed and used t o cal cul a t e outgoing nucl eon polarizations. Expressions are given f o r polarization t r a n s f e r coefficients. These coefficients are

i i i evaluated i n terms of t h e T-matrix elements f o r the interference of various channels w i t h t h e dominant S-wave, Jn =

$+

channel i n 'He(d,p)*~e

a t the 0.43 MeV resonance. Two experiments t o measure combinations of these elements a r e discussed.

(1) Gruebler, ^W. e t a l . , 1971, Nucl. Phys.

-

Al76, 631

(2) Leemann, Ch., W. Gruebler e t a l . , 1971, i n Polarization Phenomena i n Nuclear Reactions (University of Wisconsin Press), p. 548 (3) Tanifuji,M. and K. Yazaki, 1968, Prog. Theor. Phys.

-

40, 1023

(4) Mutchler, G.S., W.8. Broste and J.E. Simmons, 1971, Phys. Rev.

-

^{C3, 1031}