july_28_meet

IB2 Endcap Muon Chamber Meeting
Below are the minutes for the Endcap Muon Chamber Meeting. If you find errors or wish to correct them, please contact me at apollina@fnal.gov.

Attendance
L.Gutay,O.Prokofiev, A.Bujak, Y.Pishialinikov, G.Smith, R.Evans, N.Terentiev, S. Medved, G.Apollinari, N.Chester, A. Korytov (by video).

Agenda
Laslo                       R&D report on Anode Wires QC/QA tooling
Oleg                        Pros and Cons of gluing all the chambers at FNAL
Adam                      Gas Gain Variation in P2'.

R&D Report on Anode Wires QC/QA Tooling.
Laslo reported on the tooling R&D he started at Purdue to develop a QC/QA program at the timne of wire manufacturing to avoid defective wire. He described three subject he studied:

A corona discharger, where the wire is run close to some tips and a HV potential is used to prompt a corona discharge on defective wire where "flakes" or "bubbles" in the gold may be present. This kind of wire defects caused serious problems to the production of muon chamber in the D0 collaboration. As a typical background Laslo observes a current of 0.1 microA, while he believes that "flakes" gives a current twice as big (~0.2 microA). Unfortunately Laslo is limited by the absence of a good microscope, needed to correlate the electrical measurements with the presence of flakes on the wires.
Laslo then described a method based on the reflection properties of gold and tungstate to determine the absence of gold on the wire. He described how, at 620 nm, the reflectivity of gold is ~100% while the reflectivity of tungstate is only 48%, implying that a reflectometer could be used to check for absence of gold plating.
Finally Laslo presented some nice studies on the possibility of measuring the wire diameter using a diffractive method where the position of maxima and minima in the diffractive pattern allows the determination of the wire diameter.

In the discussion that followed, it was suggested that Laslo should concentrate on the first piece of tooling, since the diameter is typically controlled rather efficiently by the manufactures, while the absence of evaporated gold is deleterious only on the region of the wire which is used to solder the wire to the pads, and therefore is a negligible fraction of the total length of the wires.

Chamber Gluing at FNAL.
Oleg discussed the possibility of gluing all the anode bars and cathode bars at FNAL. For PNPI, Fermilab will prepare kits for 144 chambers (72 ME2/1 and 72 ME3/1), while the chambers for IHEP will be 288 (144 ME1/2 and 144 ME1/3). Considering the fact that the anode bar gluing is the most critical operation in the CSC production, there can be the following two scenario:

shipping of all the chamber parts from FNAL without cleaning and gluing
cleaning and gluing all panels at FNAL, dry-assembly the panels into a chamber with a frame around them and shipping as a "chamber" unit.

The discussion concentrated on the following pros and cons of gluing at FNAL:

Cons

The basic cons was cost for the extra technician power. An estimate from Oleg is an extra cost of 200k$, although such a number will be re-estimated on the production floor as soon as Glenn Smith group gets into production.

Pros

There would be more QA/QC during the assembly/gluing of the panels, avoiding the expensive possibility of having to replace defective units across the sea.
The chambers would be more protected during handling and shipping, with the possibility of re-using the boxes for the chamber shipments to CERN.
The QA on the anode bar gluing would be performed by the same group with the same methods for all the chamber production.
effective use of all the tooling at FNAL.
control on the shelf lifetime of the glue.

Gas Gain in P2'.
Adam reported on the work done together with Sergei on the analysis of the cosmic test data taken with P2' in Lab 7.
He started showing the good correlation between the cosmic muon position determined by the anode wires and the scintillator telescopes. The distribution of hits along the anode direction is clearly not-uniform, due to the discreet nature of the telescopes. However, when making a clean 4-hit coincidence in a telescope (every telescope is made out of 2 pieces of scintillator, each one read out at both extremities) the rate distribution is uniform over the 12 telescopes.
The strip (cathode) occupancy, shows a small (20%) drop on one side of the chamber, due to the non-perfect centering of the chamber under the telescopes.
Out of 1.6M trigger, Adam is able to fit 457K clean tracks with 6 clean hits. The major inefficiency is due to the presence of "bad" hits.
Adam observed the typical pedestal line shift, showing a couple of events where the shift was of the order of -15 counts.
Adam fitted the strip response to a "gatti" function, plotting the chi2 of the fit. Hacan clearly observe the bad chips in the Gasplex electronics that were already found during the calibration process.
By plotting the residuals in each plane,t he resolution goes from ~600 microns/plane for hits in the center of a trip to ~300 microns/plane for hits falling between two strips.
Finally Adam presented the landau distributions for the charge deposited on the strips, showing the typical gas gain in each plane and in each HV sector, for segmentation's of 10 strips X 1 telescope width. We observe a gas gain variation of 2 to 1 (maximum to minimum) in almost all the planes apart from plane 3. In plane 3, an HV sector shows a variation in GG of 4 to 1. Oleg confirmed that the wires in the sector have been glued in the wrong position (raised from the anode pads) by mistake. We are already aware of the problem and will fix it during production by making sure our tooling (combs used during the winding) can never allow some wires to be glued in the wrong position.

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