Minutes of the 25 Oct 02 Tevatron Dept Meeting 1) News by Vladimir. Ray Stefanski will lead an effort to survey and align the Tevatron components. He will act as an interface between Tevatron Dept, Deputy Division Head, and Survey Personnel. The RF&I Dept is being split into two separate departments. Ralph Pasquinelli will lead the RF part, and Bob Webber will head the I part. Members of the Director's Review committee were pleased with the progress of accelerator complex performance since January and with our planning for FY03. They believe we can readily achieve our goal of 200 pb^-1 delivered luminosity for FY03. The DOE Review comes to town next week 28-31 Oct. 2) Dean reviewed our less than stellar week delivering luminosity. We had one good store (~35 e30 peak lumi), a shutdown and its associated problems coming back up, one poor store (~15 e30 peak lumi), and a couple of lost stores caused by quenches at A11 early in the squeeze. The differential coupling was improved, and the vertical at flattop was raised; this work helped reduce losses at A11. It was also noticed that the pbar cogging at flattop causes a few spikes of beam loss at A11, but this was *not* the reason for the quenches. 3) Bruce reported on a second meeting with Argonne vacuum experts and some studies which were performed. The Argonne people recommended doubling the number of ion pumps in the Tev, and to use differential diode ion pumps to improve pumping of noble gases. The Argonne group is willing to continue to give advice, but they will not make any specific designs of vacuum systems. Bruce conducted an experiment in which he turned off all of the cold section ion pumps during an HEP store. There was no effect on luminosity, losses, or emittance growth rates. It was noted that the cold vacuum at D1 and D2 is relatively bad. Bruce will study the warm sections next. Bruce also outlined shutdown work which should help vacuum in the Tev. * new H degassed beam pipe and bakeout associated with - C0 lambertson replacement (MI dipoles retrofitted with heaters) - B48 abort kickers - new Schottky installation @ E17 * new 200 L/s ion pumps @ F0 lambertsons (currently 30 L/s) to better match the conductance of the beam pipe (~200 L/s) Vladimir and Bruce discussed recently observed behavior in cold ion guages. First, there is a strange 30 min oscillation in the reported pressure (amplitude is ~50% of the average reading of 1-3 10^-11 torr). Second, the pressure readings differ by ~factor 2 between 150 GeV and 980 GeV. The effect is likely caused by magnetic field differences between the two energies, and not caused by synchrotron radiation. 4) Jim Steimel summarized progress on Technical Division help in looking for sources of RF noise which might cause DC beam generation at 980 GeV. One person is studying mechanical issues, the other electronic. Current focus is determining if an observed mode at 37 Hz (happens to be the synchrotron oscillation frequency at 980 GeV) arises in the RF drive or the cavity itself. 5) Ron reported on status of studying/installing a small (~0.5m) collimator at A 48 that, according to simulation, could reduce losses of protons at B0 by roughly an order of magnitude. There are two problems: 1) there isn't enough space to install such a device (only few inches at most), 2) simulation of secondary particles coming from such a collimator is halted due to a software bug. Qualitatively, background from that collimator would negatively affect operation of the CDF Roman Pots. A quantitative analysis awaits the simulation. CDF (at least the pot proponents) would likely not want to sacrifice the diffractive physics for that new collimator. CDF will proceed adding steel shielding around the low beta quads in the collision hall during the next long shutdown. The halo task force has asked the experiments to describe how the beam halo background impacts detector operation and physics analyses. We expect feedback in 2-3 weeks. We will use that information to evaluate the need for future improvements in beam halo reduction. 6) Jim summarized recent transverse damper operation. The vertical damper has been commissioned. The horizontal damper had a problem with its autozero circuit which required a local reset. Both dampers are being used for HEP shots at 150 GeV only. Beam lifetimes do benefit while damper is on, but when the dampers are turned prior to ramping, there is a rapid beam loss roughly equal to the loss seen prior to damper usage. using the dampers on the ramp is complicated by the lack of a phase-lock loop, but we will likely try it anyway to see the effect. 7) Ron presented continuing work on longitudinal proton oscillations at injection. Based on a suggestion from Vladimir, Ron showed the how the sigma (from a Gaussian fit of the Mountain Range waveform data) of the bunch length varies versus turn number in the Tev. Although oscillations aren't obvious from the fitted mean position, the sigmas clearly show an oscillation which gets damped. The beam isn't terribly Gaussian at injection, but the sigma varies by a few hundred nanoseconds because of the "nipple" which oscillates back and forth in the profile. Ron also showed data which resolves a bunch length disrecpancy between the Main Injector and the Tevatron. The MI typically reports coalesced proton bunch length RMS between 2.8 and 3.0 ns using the MI SBD. The Tev SBD usually reports sigmas between 3.7 and 4.5 ns. Using raw data from the MI SBD at extraction and the Tev mountain range at injection, a comparison was made between an RMS calculation and sigma from a Gaussian fit. The RMS calculation for the MI and Tev raw data agreed; the Gaussian sigma calculations also agreed. So, there is no longitudinal bunch length blow-up between MI and Tev; the measured lengths agree when you compare the results from the same algorithms. The RMS and Gaussian sigma don't agree well because the bunches are not Gaussian (after coalescing at 150 Gev). The relevant parties will meet and discuss modifying SBD algorithms; making both RMS and Gaussian calculations sounds like a good option. 8) Xiaolong described a recent attempt to try to see pbar tunes with the Schottky detector during an HEP store. They tried tickling the pbar bunches to look for a tune line on the pbar Schottky signal. No line popped up, all you could see ws the response from the protons. The Schottky will be tuned up to look for pbars, and they'll try again. 9) Paul Lebrun showed the result of an analysis of pbar bunch lifetime at 150 GeV. Vladimir had noticed fitting the pbar intensity to e^(-sqrt(t/tau)) actually fit the data well for one store. Paul tried this for all 36 pbar bunches over several stores. Amazingly, that function describes the pbar lifetime pretty consistently. There is no correlation between the "sqrt lifetime" and bunch length. We'll work on understanding the physics behind such lifetime behavior. 10) Peter Ivanov described recent progress in making a head-tail monitor using the stripline pickup. They injected a single coalesced proton bunches at different chromaticities; Peter showed great pictures of the growth of the instability as chromaticity was lowered. He also demonstrated how the chromaticity can be measured using this data. Perhaps we can use this method to make online measurements of chromaticity with coalesced beam! Peter also estimated the Tev transverse impedance based on the head/tail instability growth rate. He measurement of 3.2 Mohm/m is close to the expected 2.0 Mohm/m, although a difference in the expected/observed bunch length was not taken into account. It is clear that this configuration can detect oscillations of ~1 mm amplitude...it is not clear if it can see much smaller oscillations ~50 um which could be generated by gently tickling the beam while try to measure tunes.