Minutes of the Tev Dept Meeting 09/13/02

1. News, Vladimir: a) Jeff Spalding takes responsibility on Run IIb; b)
there will be internal and DoE reviews in October and that will occupy the
BD management for a while; c) CERN has started Beam-beam compensation
program with wires, the first test at the SPS with DC current demonstrated
significant tune shift and losses.

2. Vladimir presented status of the Tevatron: mean initial luminosity in
early September was <L>=22.1e30 (stores 1735-1750) that is 19% larger than
in July L=18.6, #1494-1518, (with about the same L-lifetime of 10 hrs) -
and the major reason for that is smaller beam emittance at low-beta. Tev
luminosity is consistently above record Run I luminosity (24.1 at CDF),
now the record is L=26.4e30 in store #1583. That number is within the
luminosity expectations made in July (range 26-30e30). Major reasons for
unreliable operation are hardware (kickers, RF, VFCs, raccoons, TEL) and
transverse instability. The most remarkable progress was in a) suppression
of sigma_s blowup by longitudinal damper; b) revival of the BLT system to
correct injection errors; c) tune drift studies; d) dancing bunches model;
e) TEL lifetime; + 11 more items (see the talk on Web). Major goals for
the next 2 months: a) fix A1 line; b) understand(=kill) transverse
instability +18 more items. If all that done, then expected luminosity in
early November should be about 32-40e30. The point was made that more beam
study time is needed.

3. XiaoLong summarized last week luminosity: 6 stores, all but two above
20e30; record number of antiprotons at LB N_pbar=580e9; some tendency to
better p- and L-lifetime, better emittances in the last 2 stores due to
operational BLT (inj error correction), less longitudinal pbar shaving at
980 than before.

4. CYTan and JS tested the transverse damper electronics and found that 3
micron oscillations are 20dB above the system noise. It was suggested
(McGinnis) to reduce the loop gain by 20-40 dB (just to have enough to
damp the instability) in order to reduce the beam emittance growth due to
the feeback system noise. CY also mentioned that measured betatron phase
between pick-up and kicker is different from the MAD model.

5. Jerry summarized the BLT progress: two systems were commissioned, the
McGinnis system was ready first and, after calibration during pbar only
store, was used for successful closure in the last few stores. Operation
experience says that the closure should better be made in both H and V
planes. Bunch #1 in each pbar transfer get larger kick than others at
injection--> the kicker timing to be optimized ASAP.

6. Jerry on behalf of MM also informed that tune drift compensation system
is "almost ready", but due to lack of study time some offset in summing
module was not fixed and as the result, the system was left OFF.

7. pbar only store: Vladimir was suprised to see that pbar bunch length at
injection is larger than proton one (4 ns rms) and that about 8.5% of the
beam is out of RF buckets (i.e., DC). Lifetime without protons at 150 GeV
is about 20 hrs (vs 1 hr with protons), and >160 hrs at 980 GeV (30-40 hrs
in regular stores). There is large discrepancy (25%) between beam
intensity reported by DCCT and by the narrow gate integrator, is was
observed in regular stores as well and has to be explained and fixed. Loss
of pbars on ramp was very small (2%?) comapared to 12% with p's.

8. Frank added that pbar only lifetime at 150 GeV depends on vertical
emittance (larger beam - smaller lifetime) - in agreement with known
tight vert aperture at C0. He also analyzed proton dynamics on ramp
and and has shown that longitudinal emittance never grows on the ramp - so
at 980 GeV it's either the same as at 150 Gev or smaller (i.e. there is
longitudinal shaving). Previous idea that chromatic tunespread C*dp/p is
the reason of p-losses on ramp is not supported by the pbar only store
result (see item 7), so now competing hypothesis is that bunch intensity
matters most.

9. Bela summarized decoupling studies around B0 at low-beta. Better
currents in skew-quads are found; local decoupling led to better global
decoupling (0.002 vs usual 0.003 or more). New currents will be
implemented at the end of some store and separators reoptimized (with hope
to improve beam-beam overlap at IP and, therefore, luminosity). D0 to
follow. Valery asked how they know that the correctors used are not
rolled ... Tanaji sent a convincing answer after the meeting (different
correctors used with the same result).

10. Valery sees the light at the end of the tunnel concerning injection
lines. The light is coming out of A1 line: Tev orbits are right as the
lattice model predicts (BPM errors are acceptable, scaling of the BPM data
needs to be introduced of about 0.92H and 0.95 V), while BPMs in A1 line
and MI have 3 times larger errors and measurements show that the problem
is either in A1 line or in MI extraction elements. Valery suggested that
before fixing (replacing) BPM electronic in the TEv we have to improve A1
and MI BPMs as those are more important (now).