Minutes of the Jan 20, 2006 Tevatron Dept Meeting * News (Ron) - The long shutdown will begin on Monday Feb 27, not Wednesday March 1. * Weekly Summary (Andreas) - Unfortunately, there was only one HEP store this week, and it was terminated intentionally prematurely. Store 4590 had the fifth best initial luminosity of 161 E30 cm^-2 s^-1, and the lifetime was good. However, one of the A49 vertical separator power supplies failed, bringing the beams out of collisions. The store had to be terminated in order to replace the supply. Over 3.8 pb^-1 was delivered in only 12 hrs. Shortly after initiating collisions for the subsequent HEP store, there was quench that resulted in a cryo vacuum leak in A44 and required warming up the A4 house. (See more in Dean's report.) Apparently, an incorrectly installed O-ring finally failed after many years. During the downtime, various other tasks were done, including: removal of the crystal collimator, survey level runs through the IPs, installation of tubing for a water level in C-sector, installation of an air flow sensor in the CDF shield wall and thermocouples on the D0 low-beta quad support columns, investigation of the OTR motion control, fixing the IPM electrical noise problem, replacing (saturating) mixers in the 1.7 GHz Schottky system, pulling of cables for new separator to be installed at B48. Currently, the best guess is A4 will be cold on Tuesday or Wednesday of next week. * Investigation of Quench in Store 4594 (Dean) - The quench occurred approximately 15 seconds after initiating collisions - 5 houses and the B0 and D0 low-betas quenched. Investigation showed that the T:SQD0 skew quad circuit was not turned back on after a D0 collision hall access, so the tunes were far from the desired values. Operators had not unbypassed the usual alarm list after the D0 access, so the T:SQD0 digital alarm did not post to the alarm screen. T:SQD0 only has current starting at LBSEQ 23 (late in the squeeze), and it runs at -2A for HEP, but it wasn't noticed during the dry squeeze and studies before the shot. For the HEP shot, the tunes split apart when SQD0 should have been on, and when collisions were initiated, the horz tune was above 0.59. Losses at D0 developed relatively slowly, reaching 12 Rad/s and quenching the low-beta quads. When the abort was pulled, there was a sudden loss exceeding 50 Rad/s at the detectors. It is likely that the protons had grown transversely quickly, and some of the beam missed the abort block and continued downstream and caused the higher losses. Note that scraping had not yet begun, so the collimators were still retracted. A44 was not hit with losses, but that cell quenched sympathetically with adjacent cell that did get hit with beam. We will work with the operations department to improve procedures to prevent this kind of incident from happening again. * Nonlinear Effects of the Proposed Sextupole Circuits (Alex) - Alex used the new particle tracking feature in OPTiM to investigate nonlinear effects of the proposed sextupole circuits with the 150 GeV and low-beta lattices. There seems to be little difference between the present and new conditions. Alex will give the tracking data to Yuri for additional analysis of the resonance strengths. There are no bad effects that would prevent proceeding with the plan to rearrange the sextupole circuits. * BBQ and Chromaticity Tracker (Tan) - Tan compared tune measurements with his Base Band Tune (BBQ) (horizontal pick-up only) system to the 1.7 GHz Schottky. When tunes were changed for an HEP tune mult calibration, he did see changes in the BBQ, but it disagreed with the E17 Schottky by 0.002-0.005, but part of the discrepancy may just be swapping the horz and vert tune. The first attempt to use the chromaticity tracker looked promising. Using the tune tracker excitation frequency as a carrier, the RF phase is modulated slowly (23 Hz). A VSA is used to demodulate the betatron tune, and the height of the demodulated peak is a measure of the chromaticity. Tan saw a linear relationship between the measured and expected chromaticities over a range of set chromaticities, but the slope is not quite unity. He is also chasing a factor of 2 somewhere in his calcuation. At any rate, it's a good start. * Plan for Next Week: The plan is to get the Tevatron back up and running. We don't expect any big changes in starting up with beam. We do want to parse the squeeze, especially around LBSEQ 17 and 18, since we believe we discovered a typo a feeddown setting in LBSEQ 18.