The (7,7) optics at CERN PS

The PS lattice is composed by one hundred combinedfunction magnets, which set the bare tune of the machineto (Qh,Qv) = (6.25, 6.28). Low energy quadrupoles areused at injection to move the tune in a limited working pointarea. In particular the vertical tune is moved below 6.25 toavoid the structural resonance 8Qv= 50 coupled with spacecharge, which leads to strong losses. In view of the highdemands in terms of beam brightness for LIU and HL-LHCprojects, the interest of exploring different integer tune work-ing area started during last years. During 2016, for the firsttime, it has been possible to explore the (7,7) tune workingarea at injection using the auxiliary circuits of the combinedfunction magnets. A finite-element magnetic model, underdevelopment, has been used to predict the required currentsin order to get the desired optical parameters. In this pa-per we present the results and issues encountered duringthe Machine Development (MD) studies about the injectionin the (7,7) area along with optics and beam parametersmeasurements