Minutes of the March 14, 2008 Tevatron Dept Meeting

http://indico.fnal.gov/conferenceDisplay.py?confId=1628

* News (Jerry Annala) - "Cities of the Underworld - Chicago" will air Monday 
March 17 at 9:00 PM on the History channel.  The Tevatron and Numi should make an appearance.

The Lab is considering moving this summer's shutdown to March of 
2009.  We need to consider what this means, and plan what work we 
could do in a 1 week type shutdown if this comes up instead of a 
long shutdown.

We should continue the process of scheduling our furloughs for the 
next two month period beginning the first full week of April.  
Fill out the request form and turn in to department head.

Bruce will be covering the coordinator position for Andreas from 4 days 
beginning Monday 3/17.

* Weekly Summary (Andreas Jansson) - In the past week, there have been 
9 stores in the Tevatron with initial luminosities between 58 and 275 
e30.  Of those stores, only two terminated abnormally.  Over the course 
of the week, there was problem with the BLT front end locking up, the 
controls for the D17 collimator misbehaving, and with the A4 cold 
compressor.  One store ended when T:SF power supply failed.  It was 
noticed that the orbit continues to change for up to a couple seconds 
after low beta is reached, and this could be causing some problems 
with our orbit smoothing.  Also, the horizontal collision point at 
D0 has been moving and is nearly out of tolerance.

Studies completed last week include commissioning of at upgraded 
orbit stabiliztion program, and actual orbit smoothing between 
stores.  Changes instituted include setting the injection error 
for Pbar steering to zero, and doubling the length of time the 
Pbar Jacker (PBJ) is on.

* Orbit Stabilization Status (Dean Still) - The program Vahid wrote in 
2005 has run well since he left the lab, but we began having problems 
recently when CDF began having HVAC problems.  Investigation lead to 
several issues that have been (or are being addressed).  Initial 
improvements were made just by changing the set of correctors and 
BPMs used by the program.  Major program restructuring was done leaving 
the actual correction algorithms alone.  Changes include control of 
the program via state devices, and adding states (low beta, collisions, and 
end of store) where actual orbit corrections can be made (not just 
stabilization).  Much of the control of stabiliztion process was removed 
from the applications, and only one instance of the process should now 
be allowed to correct the orbit at a given time.  Much documentation 
of the process was added and linked to TEVATRON HOME -> Projects -> 
Smoothing. (http://www-bdnew.fnal.gov/tevatron/projects/smoothing/index_smoothing.htm)
There are still some improvements to be made, but the process is once 
again doing a good job of controlling the orbits.

* Chromaticity Tracker (CY tan) - Problems with the Chromaticity 
tracker were thought to result from the stucture on the raw Schottky 
signals.  A High Pass Filter was used to clean up this signal.  The raw 
Schottky signal looked to be much improved, but the tracker still +/- 
1 unit of fluctuation on the Chromaticity signal.  It as discovered that 
frequencies in the Schottky signals coming from coupling from the other 
transverse plane, and from the lognitudinal plane.  Using many signal 
generators on the bench allowed Tan to reproduce the types of signal 
that caused the chromaticity tracker to have problems.  He was able to 
use a commutating filter (very narrow band filter that tracks the main 
betatron frequency) allowed the chromaticity traker to work great on the 
bench.  Work still needs to be done to take this improvement to the 
Tevatron and waiting for technician time is part of the process.  The plan 
is to concentrate on making this tracker work at 150 GeV first.

* Differential Coupling at Collisions (Alex Valishev) - If the Proton 
collision orbit is decoupled, the Pbar orbit minimum tune split is 
between .01 and .012.  No setting of feeddowns have be found to reduce this 
problem.  There is a source of differential coupling at B0 that is 
cancelled at D0 on the Proton helix.  On the Pbar helix, however, there is 
a huge source of differential coupling at D0.  The cause would seem to be 
nonlinearities in the Low Beta Quadrupoles, but the size of the 
nonlinearities along with the differential orbit errors would have to be 
large.  It is not yet known if this combination of errors is realistic.  
Yuri suggest better helix closure should address this cause.  A Pbar only 
store may be needed to look at the closure of the Pbar helix.  Other studies 
may include AC excitiation of individual Low Beta quad to look at orbit 
excitations downstream.  Optimum SQD0 settings vs closed orbit bumps in the 
Low Beta Quads may also be valueable.  AC diple studies may also be requested 
for this investigation.

* Plan for upcoming week

	- Integrate Luminosity
	- Use Proton only stores where impact is low to continue commissioning
			orbit stabilization improvements
	- Investigate orbit movement at end of squeeze
	- Differential coupling studies if analysis determines that they 
			would be beneficial