Minutes of the 08/16/02 Tev Dept Meeting


1. Vic Scarpine has outlined BLT issues/plans: a) old Rf modules are
ringing  --> protons affect readings during pbar injection;
b) 53 Mhz integrators are supposed to fix that but it did not happen in
store #1661; d) by some reason the first 16 turns are not seen well why
1024 turn data look believable; c) they just need more time (more
injections) to identify the problem with 53 MHz integrators. [to be given
next week]

2. Peter Garbincius reviewed status of the C0 Lambertson replacement
project (see details in home.fnal.gov/~peterg/c0_lambertson_replacement):
MI dipoles are picked, found 0.9" disrepancy between length of the
Lambertsons in the lattice files and recent survey, horz sagitta of the MI
dipoles found to be a non-issue (Syphers, Ohnuma, Peter G.), the shunt current
value recalculated on basis of magn meas results and found to be some 232 A
instead of previous Bruce's value of 153A (Bruce used design MI magnet
parameters. Isssues: a) we need to tune/adjust shunt current during ramp;
b) specify tolerances on the shunt current setting/stability [I have some
estimates done by T.sen and myself for Bruce]; c) how will we bake the
pipe, MI magnets were not designed for that.

3. XL reported in general good week - 6 stores, Lumi between 13 and 22.5,
in the last 3 stores p-lifetime has become better than last week (>170 hrs
vs 30-40 hrs) - it's not clear why; in 1663 we had significant increase of
pbar emittance between 150 and low-beta -?, BLT situation does not allow
to close injection orbits well - that may be the reason of somewhat worse
pbar emittances recently (most remarkable - store 1661 with record number
of pbars -550 at low-beta, but poor emittances). Proton parameters are more
or less stable, instability is suppressed --> we will increase N_p in the
following stores.

4. CYTan and Jim S had all parts of the transverse bunch-by-bunch
horz damper ready and maesured beam response with 36 bunches. That info
needs to be processed, delays calculated, one more shift is needed
to perform similar measurements with digital notch filter, then they will
adjust delays/phases and will close the loop. Techs are working on parts
for the vertical damper. Jim is ready to purchase PAmps for injection
dampers.

5. Vladimir summarized observations of the transverse instability made by
him/XL/Peter I and Tan: bunch blowups are different for different bunches
[--> we really need bunch-by-bunch damper], sometimes Schottky power varies
periodically with 10's of seconds period [similar to what Yuri observed 2
weeks ago], at 150 GeV it was found that with very high N_p=250 e9
one can start from C_h=C_v=8, reduce C_h to 1, reduce C_v to 2.5 before
the instability occurs ; that is consistent with 1990's measurements by
Goderre, Peggs, et.al. Peter Ivanov suggest to explore other WP for better
coherent and incoherent stability [got time next week]

6. Ron Moore has made a nice new tool - Tev Array Display. Use it in MCR!

7. Valery Balbekov presented results of his dancing bunch modelling which
are close to observations: bunches do oscillate forever, independently
with weak coupling. Model is improved (does not have artificial positive
feedback) and contains only inductive impedance plus RF cavity impedance
at main 53MHz. [next week Ron will provide large file with
digitized 30 dancing uncoalesced bunches over long time]

8. Mike Martens has made orbit bumps at D0 and made them happy. He sees
some 0.5 mm orbit drifts since last smoothing - will fix that next week.

9. Tanaji did increase p-pbar vert-separation in the short arc (B0 to D0)
by 8/15% and observed significant (>40%) luminosity lifetime improvement.
We will incorporate that (8%) increase in sep-voltage this weekend [Dean].
We will do End of Store studies with larger hor sepration as well.

10. Steve Pordes performed measurement of p-emittance ofter 50 flies and
found 2 pi growth. Mike Syphers estimates of the emittance growth are
consistent with that. Harry, Aimin and Stephen did orbit bumps at C11
(SyncLite location) and found that current pbar lite calibration is wrong
by almost fator of 2, and previous (2 week ago) calibration was correct.
That disagrees with simple optics calculations of Alan Hahn.

11. Vladimir shown tune scans of p-losses when TEl acts on one p-bunch -
resonances are seen clearly, variation of losses vs tunes is huge 1kHz to
50 kHz , or lifetime from 500 hrs to 10 hrs. All (me + Tanaji +Peter)
agreed that similar tune scan has to be done during p-pbar store [next
week end of store, 4 hrs].

11. Alvin considered losses in store #1661 and concluded that his
previous calibration of RF bucket losses (store #1613) is incorrect by
factor of 4 (what has changed?). This is the only type of losses
which incraese with the time in store. P-losses at the beginning of the
store are several time larger than vacuum losses - not clear why excactly.
Alvin asked for 2-3 hrs of uncoalseced beam at 980 Gev to measure average
Tev vacuum. [SLite should be ready first - to see emittance growth]