Minutes 3-5-2007
From GlueXWiki
FDC Weekly Meeting
Date: March 5, 2007
Participants: Daniel, Tim, Fernando, Kim, Simon, Brian, Chuck, Roger
Next Meeting: Wednesday, March 14, 2007 @ 1:30 p.m.
Contents
FEA Analysis
- Tim has completed a round of finite-element analysis for the deflections to our wire frames for a number of different scenarios. These includes board 5-mm and 6-mm thick with no cut-outs for daughter board clearance and for a 6-mm board with the cut-outs included. He assumed tensions of 20 g and 130 g for the sense and field wires, respectively. The total wire load is about 32 lbs. He also included a semi-realistic overhang of the PCB on the inside perimeter to allow for the capacitors to be included on the back side of the PCB. - For the 5-mm and 6-mm thick wire frames, the deflections in the directions along the wires and perpendicular to the wires are below about 100 microns. For the 6-mm thick design with the cut-outs for clearance, the maximum deflections are below 300 microns.
Design Issues
- Based on the FEA analysis, we discussed again the basic design for the wire frame. First we will move to design a wire frame that is 6-mm thick, has the cut-outs for clearance for the daughter boards and connectors. We still need to understand the deflections that are present with the final inside perimeter overhang. The capacitors will be placed on the back side of the STB, but above the top of the solder pads. - The design of putting the cathode preamp connectors in the middle of the cathode sandwich is too technically risky and we will drop this idea. - With the 6-mm thick wire frame, we will only have to machine the G10, and the not STB PCB. Thus will we have a continuous frame for support. - Fernando has found a daughter board connector that is only 4.2 mm thick. He will pass the specs onto Tim and Chuck and they will consider this as nominal for proceeding. This new connector is wider than the previous connectors that Fernando had found, namely 1.8-in wide compared to the old number of 1.5-in wide. This new wider connector will allow for the radial length of the daughter boards to be reduced. Thus these connectors will be moved out radially, giving more room for traces and components. - The cathode design has been modified. We have decided to set the U and V stereo angles at +/- 15 deg with respect to a line perpendicular to the wire plane. The old values were +/- 45 deg. Chuck has some work to do to figure out the placement of the connectors and problems with the gas port clearance and locations. - We also plan to make the pitch of the strips in the middle of the plane smaller to be able to handle the rates. The width to modify is +/- 5 cm about the middle of the chamber. The new pitch should be 2.5 mm with a 1-mm gap. How this design modifies the design and/or channel count will be studied by Chuck. We need to optimize this. - The time line is for Chuck to finish placing the connectors after getting new dimensions for the daughter boards, and then for Kim to work to perform a realistic layout of the STBs. - DSC asked Kim to rough out the HVTB so that we can work on understanding the real estate issues and the mechanical design issues. - DSC asked if we could aim to have the STB and HVTB design complete by the end of April.
Small-Scale Prototype
- Brian has completed manufacturing the strip planes that are at 90 deg with respect to the wires. They are ready for installation now. DSC asked that Simon complete the resolution studies with the reworked grounding configuration for the chamber (done during Gerard's visit in January).
Wire Winding
- During our visit to FNAL in January, a question came up regarding the relative heights of the wires. It is acceptable to have both sense and field wires in contact with the solder pads, or do we need to raise the sense wires to be coplanar with the field wires? We need to do the calculations to address this question.
Drift Chamber Review
- The DC Review begins tomorrow. The chamber frames and cathode mockups will be brought in for show 'n tell.
Minutes prepared by Daniel. Send any comments or corrections along.