Good Morning- As of this morning Tank 1's array is undergoing a final leak check in a helium bath. If it looks stable after an hour, the conflat flanges joints will be removed and then the array will be prepped to go back into the tank. Pumpdown out in the aisle will likely begin before the end of the day so that an RGA with the tank warm can be done tomorrow. Since the RGA requires vacuum of 10-7 or better, ion pump jumpers are being fashioned. Plans are also being made to thermally cycle the tank to ln2 temperatures and back and look at each tank with the RGA to ensure no cold leaks. The cryo dept. is in the loop as to what is required for the tanks to be thermally cycled. There are 2 or 3 bad thermocouples on tank 1 that are in the process of being repaired, too. Tank 4 is also about to undergo a final leak check. It is possible that the slight leak being seen is helium seeping through the 'o' rings on the connections between the array and the leak detector. At present, plumbing is being replaced (externally) to remove that source of doubt. Tank 4 will likely get buttoned up later today, too. Leak detection on both tanks is beiong done on the most sensitive (-10) scale. Its my bet that with the RGA/thermal testing that should be done, re-connecting the cryo amp boxes and testing, doing final tank close-ups, rolling them in, aligning, prepping, etc. that a bake of the area will start Monday at the soonest. We should stay in supervised access in the Rings until the bake out begins. Regards, Elvin ------------------------------------------------------------------------- Summary of E835 meeting 3/23/2000 Present: Luppi, Kasper, Rosen, Roethel, Joffe, Graham, Seo, Gollwitzer, Legger, Obertino, Negrini, Baldini, Stancari (M), Stancari (G), Garzoglio, Boca, Rumerio, Pordes Immediate: Beams Division Head has reissued policy on 2 person rule. We will post it in counting room. Tunnels require 2 people in good contact. Accumulator Vacuum Status: Leaks may (or may not) be all found. (Leak checking is at 10^-10 range). Tanks will be put under vacuum and nitrogen line cooled and pressurized in next days. Baking may start Monday. Supervised Access probably through the weekend. Presentations/Announcements: Luminosity Monitor: Dave Joffe said he has rewritten the instructions for looking after the Luminosity Monitor system and will put copies in the binder and attached to the Luminosity monitor Rack. Willi showed a set of plots on the stability of the luminosity monitors (left and right) over a 36 hour run. The centroids of the ADC spectra are stable to better than 0.25% (estimate of scribe from plot shown). The width of the signal is also very stable. The center (movable) detector was at a smaller angle (1.7 degrees) than the side monitors (3.5 degrees) and as a result suffered from a larger background. Dave has moved the center detector to a larger angle, ~3.5 degrees - to be checked when the beam returns. Energy Scale of Neutral Trigger: Jason showed plots of the turn-on points (energy equivalents) of the minbias signals before and after the CCAL high voltage changes. While the "after" plot has some anomalies (due to the problems with some 20 CCAL blocks) the effective threshold has indeed moved down by a good 10%. Jason also showed plots of the energy distributions from the ETOT lo triggers before and after the high-voltage change. Looking at the highest bin in these distributions, (which are a convolution of a turn-on and a steeply falling energy distribution), the effective threshold here has been reduced by about 14% - the peak bin was 5.4 GeV and after the change was 4.7 GeV. Jason proposes to raise the thresholds appropriately - (see later remark from Stephen). Life in FCAL-2000. Mat showed some plots of the performance of FCAL-2000. He looks for the photon in J/psi gamma decays at the chi-2 and chi-1 in the central and the forward calorimeter on events which fit the psi-gamma hypothesis on the basis of the observed psi. The fit tells him where the photon should be and its energy and he looks for such a cluster. He showed plots with 230 such events in the CCAL and 34 in the FCAL at the chi-1 and 170 - 10 at the chi-2. Plots of (E(fit)-E(found))/E(fit) were centered at 0 for both calorimeters with a number of events near 1. Mat showed the location of all events in the FCAL - to see if the events near 1 were in a particular region or near a boundary. With present statistics, they seemed not to be in any particular place. As a further check of the calibration, Mat has taken (psi + 4 photon) events where at least three of the photons are in the CCAL. He takes those events which fit psi pi-0 (+2 photons) where the most forward photon is ignored when constructing the pi-0 and then plots the invariant mass of the forward photon with the other unpaired photon. The most forward photon can be either in the FCAL or in the CCAL. A clear pi-0 signal is seen for both cases. Stephen asked usual questions about how often in the chi's he found the photon when it was predicted to be in the FCAL. There was also some issue about the FCAL cluster position calculation which Mat will look into. Sci-Fi Status: Wander reported that he has identified the QPA02 as the source of the random noise in the system and that he has not seen any specific feature in this noise such as 60 Hz or any other frequency. He has looked at channels with broader than average pedestals and they do not look qualitatively different. He has taken pedestal data and concludes that setting the pedestals at 4 sigma would be OK. Luppi mentioned that the Sci-Fi people are considering different algorithms (eg fixed amount above pedestal, 4 sigma, different for different types of cassettes). Changing Things: Stephen would like to insist that any changes (eg 4 sigma on Sci-Fi pedestals, energy threshold changes, major global voltages etc) only be implemented once we have re-established running conditions. This will allow us to understand the effect of the deliberate changes and to realize if there are unexpected changes when we turn on. Plots on Web: Stephen repeated the plea he made in his e-mail re making plots available to the Web. Gabriele is setting something up. Michelle suggested that a link be put in the minutes for plots referred to therein. If Stephen could do that, he would love to (he says now).