ycoor += (1-(upDown+1)/2)*gap;
gMC->Gspos("FSTR",j ,"FLTA",0.,ycoor, zcoor,idrotm[nrot], "ONLY");
gMC->Gspos("FSTR",j+1,"FLTA",0.,ycoor,-zcoor,idrotm[nrot+1],"ONLY");
ycoor += (1-(upDown+1)/2)*gap;
gMC->Gspos("FSTR",j ,"FLTA",0.,ycoor, zcoor,idrotm[nrot], "ONLY");
gMC->Gspos("FSTR",j+1,"FLTA",0.,ycoor,-zcoor,idrotm[nrot+1],"ONLY");