Minutes of the 12 Dec 2008 Tevatron Dept Meeting http://indico.fnal.gov/conferenceDisplay.py?confId=2260 * Weekly Operations Summary (C-Y Tan): The Tevatron delivered 66 pb^-1 to the experiments over the past 7 days. There have been 10 stores with initial luminosities between 273 and a new record 355 ub^-1/s. Only store 6619 was aborted unintentionally when the B2 power supply safety coordinator failed. Lowering the chromaticity at LBSEQ 14 and 15 has reduced the peak losses at those steps. The D0 IP was adjusted during store 6630. An orbit bump was made to reduce the currnt in the VA47 dipole corrector. There were parasitic TEL-2 studies during several stores. There were 3 hours of crystal collimator studies at the end of store 6631. CDF's reported luminosity was abnormally high for stores 6622 and 6625; various scans (separator, alpha bump, coupling) were done to verify the Tevatron was not the problem before CDF identified the the problem as a faulty hardware channel for the luminosity detector. * Low-Beta Lattice Measurement (Alex Valishev) - Alex measured the low-beta lattice on Dec 6 with the Orbit Response Matrix method. The model returned larger beta* for D0, but the numbers didn't agree with the luminosity ratio between CDF and D0. When taking coupling into account properly, the CDF and D0 beta* agree fairly well (verified with MAD-X). Dispersion is small at both IPs. The measured D0 beta* horz and vert positions, offset by 20 cm from the IP in opposite directions, was not confirmed with alpha-bump scans. The pattern of skew-quad errors from the ORM meausurement does not seem to be real, it could be a systematic artifact that Alex is still investigating. * A150 Line OTRs (Vic Scarpine) - Vic showed showed some recent images of pbars from the OTR at location 902. (The one at 903 isn't functional presently.) Over the 45 images (5 stores) he showed, there is ~0.5 mm peak-to-peak variation in the horz centroid position, while the vert looks very stable. The beam sigmas (at that location) are ~0.65mm with variations of ~0.05mm, some of which should be real differences in pbar emittances. The OTR should be very capable of helping diagnose the source of the occasional pbar injection misteering. We will put the appropriate devices in the datalogger and SDA. * Beam-Beam Compensation with Hollow Electron Beam (Alex Valishev) - In the Tevatron, the proton transverse beam size is a ~factor 3 larger than the pbars at the collision points. Consequently, the protons suffer from the large tune spread induced from the nonlinear beam-beam force. Alex studied Ron's idea to use a hollow electron beam on the protons (hole like the "inverse" of the pbar profile) to reduce the proton tune spread. Simulations show a gaussian "hole" in the electron beam does reduce the tune spread, but the proton lifetime actually becomes worse. The beam losses were found to arise from chromatic effects - losses could be nearly eliminated with chromaticity = 0 and zero dispersion at the electron lens. Phase advance between the TEL and IP also play a role. Partial compensation may be possible with a larger hole. Effects from e-beam misalignment were not simulated. * Plans for Next Week - Continue the excellent delivery of luminosity - Abort gap cleaning with bumper (Bruce, Jim, Elmie - proton-only) - TEL-2 studies (Seva - beginning and end of HEP) - Reduce losses later in squeeze (several folks, proton-only) - Chromaticity Tracker (Tan, proton-only)