Minutes of the July 22, 2005 Tevatron Dept Meeting * Weekly summary - Vahid: Seven stores were started this week with luminosities between 56 and 106 E30 cm^-2 s^-1. Only four were terminated intentionally; one ended when the RF anode supply tripped off, one ended when the B2 VCB (vacuum circuit breaker) opened up (blown fuses in the potential transformer), and the other ended when the F4 bulk supply tripped, causing protons to hit the E03 secondary collimator and cause a quench. The lower luminosities were caused by a lack of pbars. A couple of stores had lower proton lifetimes and/or high halo losses because the horz tune landed on the 7/12 resonance - partly the consequence of having very bright (intensity/emittance) pbars from the Recycler. Tune adjustments helped the losses and lifetime, but we'll need to keep working on a better solution. There was ample time for continued studies on the 28 cm beta* and the new working point near 0.5. The CDF and D0 IPs were restored to the positions before last week's orbit smooth that caused 200-300 um shifts. The crystal collimator was adjusted so that it can hopefully reach the beam. A weak PA on RF station #2 was replaced. A HV power supply was replaced in the TEL. * AD/D0/CDF Luminosity Meeting - Vaia: Mike Syphers presented his current results of measuring beta* directly with proton-only stores. Mike gets slightly smaller beta* than the experiments report from HEP stores, but Mike proposed the difference may be caused by beam-beam effects that may distort the beta functions by ~10%. He would like to incorporate coupling and BPM non-lineratities into his analysis. Alex Valishev presented the status of the 28 cm beta* optics. (More on that below.) CDF (Chris Neu) reported improvements to the online beam width measurement algorithm that were made operational on June 30. The beam width growth is now clearly obvious from their measurements (available via ACNET). D0 (Michele Weber) reported that they are trying to understand their luminosity scaling. They continue to test new electronics for the luminosity counters that they hope to implement in August; we can expect their reported luminosity to change at that time. D0 continues to monitor their beta* offline; horz has been very stable, but the vert shows slightly more variation over time. The next AD/D0/CDF lumi meeting will take place when D0 is ready to implement the new electronics. * RF cavity dependence on temperature - Jean-Paul: Jean-Paul measured the Q and resonant frequencies (53-1200 MHz) of the spare cavity at MI-60 at T = 30, 35, 40 degC. The temperature dependence is small, especially for the lower modes. That explains behavior noted by Yuri in a previous study - changing cavity temperature did not alter the "dancing bunch" phenomenon, but moving the frequency (via VFKNOB) could stop the dancing. Jean-Paul's results are written up in AD-DOC-1897. * Integrated Luminosity vs Pbar Source - Aimin: Aimin analyzed how integrated luminosity varies as function of intensity of pbar bunches from the Recycler and the Accumulator. For the same bunch intensity *at injection into the Tevatron*, the integrated luminosity from Recycler pbars is ~18% greater than that from Accumulator pbars, thanks to the lower transverse emittance. Her analysis doesn't address effects upstream of the Tevatron, e.g. efficiencies in MI and time to stack/shoot pbars from Accumulator to Recycler. * Status of 28 cm beta* lattice - Alex: Alex had study time to test a mult built by Jerry to go from the 35 cm lattice to the 28 cm lattice. The needed horz tune changes were a little more than expected. The non-linear chromaticity, especially vertical, is larger; although the should help prevent transverse instabilities, it could limit the momentum aperture. Differential orbit measurements agree very well with the model lattice. Alex wants to try another iteration of tweaking his model to try to reduce the D0 beta* to match CDF, as well reducing dispersion' at D0. * More on 28 cm beta* measurements - Eliana compared TBT data to a MAD version of the 28 cm optics model and saw pretty good agreement. Yuri checked helix closure with beam. He saw very good agreement between the data and the model, although the helix wasn't very well closed. The smaller beta-beating of the 28 cm lattice actually will result in 10% smaller separation at the nearest parasitic crossings around D0 when implementing separator voltage changes to enforce helix closure. (Separators around D0 will run at lower voltage than now to allow 100 kV max on other separators.) * Reducing Coupling near 0.5 Working Point - Yuri: Yuri found considerable coupling from TBT measurements near the 0.5 low beta working point. He has found that the phase of SQA0 makes it ineffective in correcting the difference coupling resonance, and can work against other skew circuits for the sum resonance correction, so it is probably beneficial to run SQA0 at 0 at low beta (for the current working point, too). However, when he took TBT data SQA0 = 0 (adjusting other skew quads to decouple) near 0.5, the coupling didn't seem to decrease, at least within the resolution of the measurement. * Longitudinal Damper Status - Jim Steimel: Jim investigated what that open cable on the longitudinal damper output really does for the system. He found that the cable looks like a notch filter at 3.5 MHz. However, he doesn't fully understand why that reduces mode 0...perhaps it reduces coupling between modes. * Studies for next week: - 28 cm beta* will be the priority as Alex et al. are ready (feeddowns) - Commissioning C100 coupling measurements - Trying to keep pbar tunes constant during HEP stores - Tuning TEL for DC beam cleaning during injections - Exercising the crystal collimator - 0.5 working point studies will have lower priority until Q39S circuit can be powered up (need a new/different power supply) Minutes recorded by R. Moore