Mini-Meeting #1 =============== Follow-up mini-meeting on Ladder Testing during Barrel Construction ------------------------------------------------------------------- This afternoon, we had a small meeting to discuss two issues: #1. maximum cable length of the HDI #2. routing of the HDI cables out of the box to the Port Cards. People present: Steve Blusk Jean Slaughter Mary Bishai Greg Derylo Chuck Grimm (for part of it) ================================================================ Issue #1: Jean and Mary showed some displays of L1A before and after going through 2 HDI's which are connected by a "breakout board". The layout is: PC - HDI----------- Breakout Board - HDI --------------64 pin ---chip card | | | | | | Berg Solder Berg Solder connection connection PC is connected to a HDI via a Berg connector. This HDI is soldered to a Breakout Board. The signals are routed to a Berg connector on the breakout board. A HDI is connected to the Breakout Board by a Berg connector, and the HDI is soldered to an adapter card with a 64 pin connector. Then the chip card is plugged into the 64 pin connector. The L1A signal looked pretty good for this configuration. The DAQ seems to work fine also, so they claim that 40 cm should be OK for HDI length. They are going to investigate what is the maxium length at which the signals become too skewed or degraded to be acceptable. ====================================================================== Issue #2: We had a long discussion on whether the PC's should be INSIDE or OUTSIDE the dry box. There are several precursory points to be made here: 1. We install 6 ladders. This means 12 HDI's. So to test all 6 ladders, we need at least 3 PC's, but probably 4 (2 on each side of the barrel). 2. If we use only 1 PC on each side, it will take 2 shots to test all the hybrids. 3. Tests should probably be cumulative. That is, we test all ladders up to and including the ones just installed. Here are some of the issues having to do with having the PCs INSIDE or OUTSIDE the drybox. *OUTSIDE* PROs: Can route all the HDI+extension_HDI outside the box. So, after installing, for example, layer 3, we can test all the other layers without having to open the drybox. If we have to open the drybox to swap the ladders under test, then the drybox will need to be dried out again. That may take some time. CONs: The cabling issue of how to constrain all these long cables during ladder installation and barrel rotation is going to be very messy. Each HDI could have a 1 meter cable hanging from it which needs to be strain relieved and mounted somewhere which will not interfere with the ladder installation. OPEN QUESTIONS: a) Is ~1 meter of HDI length acceptable? b) Can all the 1 m long cables be dressed in a satisfactory way so not to interfere with ladder installation? *INSIDE* PROs: Short HDI cable lengths. No new additional problems with dressing/constraining the cables, beyond what we had before. CONs: Need to open up box each time we want to test a new set of 3 (or 6) ladders. So, for cumulative testing, we need to open up the box each time we want to test a new set of 3 (or 6) ladders. Each time the box is opened, it has to be dried out. (i.e. RH < 5-10% ? or so) OPEN QUESTIONS: a) How long does it take to dry out the drybox? * In this scenario, we would have, say 2, PC's with 5 "pigtails" hanging off. These pigtails are the necessary extension to reach any of the HDI cables on the ladders. In this case, we do not need to have extension cables for all the ladders, it is the pair of PC's which have the extensions. Of course, there is a pair of PCs on each side of the barrel. The pigtail would have an ELCO male on one side to connect to the PC and a female ELCO on the other to connect to the HDI cables. The female side should probably also have a small G-10/PC board which makes it easier to make the male-to-female connection. * Greg had some thoughts on where we might mount the PC's He pointed out that the cooling of the PC's should be thermally isolated from the alignment features of the fixture. ================================================================== If it does not take too long (say less than 10 minutes), our small group favored having the PC's inside the box. Steve intends to measure how long it takes to dry out the drybox at the cooling teststand. Jean and Mary are going to continue to look into cable length issues. What is the max. length before we hit the brick wall?