Minutes of Tev Dept Meeting 07/19/02 1. Jim Steimel talked to two RF enginners from TD and will probably ask them to do measurements of the RF noise (in cooperation with John Reid) 2. Bruce reports only two stores since last mtg, both had luminosity under 20, moreover, very small lifetime (5 hrs over the first 2-4 hours of the store, lifetime improved later). The reason seems to be pbar vert emittance blowup after we initiate collisions (from sub20pi to 30-40 pi). It takes some 5-10 min to blow the beam and hours for the halo to be lost afterward. Longitudinal bunch-by-bunch damper was ON at 980 in the both stores and we did not see bunchlength blow-up since then. After total orbit smoothing this week we have two stores in the row lost due to extensive losses early on ramp. There are signs of instability which might be responsible for that. 3. Wolfram analyzed tune measurement data for two ramps with different RF frequencies and found tha while tunes vary by some 0.003-0.005, the chromaticity varies from 15 to 27 to 12. 4. Mike Martens summarized Tev orbit smoothing (at 150, ramp, squeeze): everything looks OK, except some correctors are required to run too high currents at 980 (VF49, VC49) and during squeeze steps 8-13 some correctors (VB11) have to change too rapidly and limited by slew rate. A lot of data gathered, more analysis to come. 5. Valery Balbekov decribed new observation of dancing bunches at 150 GeV (made with Ron Moore and V.Lebedev) : amplitude of long oscillations depends on bunch intensity, bunches are weakly coupled. He suggest that the phenomena is an interplay of three impedances: 1) active (resisitive) one to cause initial instability; 2) inductive to suppress Landau damping; 3) weak long lasting wake (cavity HOM?) to cause weak coupling bunch-to-bunch. Wolfram mentione dsimilar phenomena at RHIC which sometimes was suppressed by adding another RF harmonics. 6. Valery told that he needs to redo his A1/P1 line measurements because huge errors make previously collected data not believable. 7. Vladimir did fit long dependence of the transverse size of D0 luminous region (*store 1253). Beta star is about 44 cm, that is much larger than design 35cm (CDF data for anoth store suggest 41 cm). Possible explanations (mike M) - beam is not round, X waist does not coincide with Y waist, coupling. For better analysis we need separate distributions of , , - both detectors in the same store (Jean). 8. XLZhang has shown Slite beam size variation in the two recent HEP stores - it does not chage much exept 10% increase early in the store.