Acceleration of polarized protons to 22 GeV/<i>c</i>and the measurement of spin-spin effects in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>p</mml:mi></mml:mrow><mml:mrow><mml:mi>↑</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>+<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>p</mml:mi></mml:mrow><mml:mrow><mml:mi>↑</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>→p+<i>p</i>

Accelerating polarized protons to 22 GeV/c at the Brookhaven Alternating Gradient Synchro- tron required both extensive hardware modifications and a difficult commissioning process. We had to overcome 45 strong depolarizing resonances to maintain polarization up to 22 GeV/c in this strong-focusing synchrotron. At 18.5 GeV/c we measured the analyzing power A and the spin-spin correlation parameter ${A}_{\mathrm{nn}}$ in large- ${P}_{\ensuremath{\perp}}^{2}$ proton-proton elastic scattering, using the polarized proton beam and a polarized proton target. We also obtained a high-precision measurement of A at ${P}_{\ensuremath{\perp}}^{2}$=0.3 (GeV/c${)}^{2}$ at 13.3 GeV/c. At 18.5 GeV/c we found that ${A}_{\mathrm{nn}}$=(-2\ifmmode\pm\else\textpm\fi{}16)% at ${P}_{\ensuremath{\perp}}^{2}$=4.7 (GeV/c${)}^{2}$, where it was about 60% near 12 GeV at the Argonne Zero Gradient Synchrotron. This sharp change suggests that spin-spin forces may have a strong and unexpected energy dependence at high ${P}_{\ensuremath{\perp}}^{2}$.