October 14, 2010 FDC meeting
- Blue Crab status
- Frame production, lamination
- Electronics (Fernando, Chris, Roger)
- Update on PCBs
- Cathode foil procurement
- Engineering (Bill, David)
- Wire stringing: fixtures, movement system
- Full-scale prototype tests (Beni, Lubomir)
- status of gas mixture studies
- tests with fADC125
Participants: Eugene, Fernando, Bill, Chris, Roger, Casey, Mark, Glenn, and Lubomir.
- At Blue Crab now we occupy some space at the far corner not to interfere with the installation work there. We have there two granite tables and one round. Casey will order two more round tables. Need additional temporary light. AC for the whole building is coming soon. JLab internet connection and two plain phones will be installed in the office.
- Five wire frames were laminated with Rohacell rings and sent back to the company for flat cut. Last two laminated at Blue Crab. Five new frames will come soon. Two new Rohacell rings are ready.
- The first article populated PCBs will be at JLab next week. They will be checked, channel by channel, and will be ready by the end of October. Then the first PCB ring will be glued, most likely in 126. By the end of November we will have all the PCBs ready. They will be stored in F117.
- No news from the procurement about companies (other than Allflex) interested in the cathode production. The deadline was Oct.13. As Fernando promised before, he will take care of the procurement (not a sole source!) of the rigid-flex. Fernando and Roger will contact Allflex for the details of the rigid-flex production.
- Fernando submitted a PR for the mini HV cables.
- Wire stringing: the pin bars were mounted on the granite table. Almost all the parts are ready. David got the ISA-USB converter for the movement system, but has not tested yet. Bill got a PMT from Carl to be used as a sensor for automatic mapping of the wire positions. If the light on the PMT is too high, we would better use a photodiode. Fernando will help Bill with this.
- Vladimir Nelyubin checked the wire tension with the new method: measured 70g, instead of 100g used in the stringing. He will re-string the wires and repeat the measurements. Suspects friction between the wires and the rod when stringing. Concerning our procedure, he thinks for 20g tension that we will have, the pulley system will be helpful. Eugene proposed how to measure the wire-rod friction.
- Tests with 90/10 Ar/CO2 gas mixture showed that the signals are factor of 4 higher than expected. To have the same signals with this gas mixture as with 40/60 Ar/CO2 at 2225/-500V, Garfield predicted HV at 1650/-200V, instead we found 1550/-200V. To understand this, first, we wanted to make sure that the old MKS gas system is OK. Beni connected the pre-mixed bottle Ar/CO2 89.7/10.3% used for the IU chambers, to the prototype. After some tests he again put 90/10 using the MKS system what we have now. The results of this comparison will be presented on the next meeting.
- According to the literature, Garfield is not very good in predicting the gas gain by simulating the avalanche process. People normally measure the gas gain and use it in the Garfield simulations. To do this we used 55Fe source which produces a point-like known charge in the gas. We measured the output signals at the shaper-board. To calculate the gas gain one has to know also the gain of the preamp-cable-shaper system: Fernando has measured it already in one of the GlueX docs. Results of the gas gain measurements will be presented next week.
- All the above measurements were done with fADC125. The simulations/measurements will be used to find the working HV for the different gas mixtures and to estimate the ranges of the signals. Next we plan to repeat the above measurements with 40/60 Ar/CO2.