November 10,2010 Tracking CDC/FDC
Contents
Meeting Time and Place
Wednesday November 9, 2010 at 11:00am At Jefferson Lab, the meeting will be held in F326
Connections
To connect from the outside, please use ESNET
1.) ESNET: 8542553
2.) Phone:
+1-800-377-8846 : US
+1-888-276-7715 : Canada
+1-302-709-8424 : International
then enter participant code: 77438230# (remember the "#")
Agenda
- Announcements
- FDC Update logbook
- CDC Update [1]
- Production Status of the CDC.
- High surface-resistance straws.
- CDC Prototype Studies
- Afterpulses Event pics
- Flow rate
- Fe55 peak shape
- 55Fe vs cosmics
Minutes
Participants: Curtis, Naomi, Eugene, Beni, Mark, Simon, and Lubomir.
FDC Update
Production
23 wire frames are laminated with Rohacell. All 32 will be done by Thanksgiving. 14 are back from the company after fly cut, ready for the PCB lamination. Problems: low temperatures in the off-site building, if below 60deg F we can't use the glue. There was delamination (~1-2cm diameter spots) on two of the populated PCBs and we suspect no proper heating cycle used for soldering.
Beni was working on the movement system to control the wire stringing. JLab controller doesn't work with our stepper motor and we are considering buying one.
Full-scale prototype tests
Beni: using fADC125 on the wires. Preliminary results: one can achieve ~200 microns resolution with 90/10 Ar/CO2 gas mixture. To calculate the drift time from fADC125, he has also the trigger signal connected to the input of fADC125. Noise from a discriminator card turned out to be related to a bad low voltage connector (Fernando).
CDC Update
Production status
The plastic components (feedthroughs, donuts, pinholders) have arrived and we have a group of undergrads working on checking them for size following the procedures developed for the Al components. So far they have checked 1/3 of the donuts and 1/4 of the feedthroughs, with no rejects. They have not started on the pinholders yet.
We tested our ultrasonic cleaning bath with a few of the plastic components and this was trouble free so we cleaned 100 feedthroughs and donuts.
Donuts (plastic and Al) were glued into 46 straws last week and the first row was dryfitted into the chamber last Friday - see photo on the wiki.
High-resistance straws
On Monday Kate checked the resistance along the length of the straws and found some at 400-500Ω. The expected value was 80Ω. After selecting straws from various rows in the packing crate we found that all the straws in the top bundle (where the 5 straws from the new batch of material were located) were bad, and about half of the top row in the next block. It looks like the Al coating is thinner, it appears transparent.
The straw check procedure has been modified to include a check on each straw's resistance before cutting it to size. Tim has been notified to contact Lamina about it.
We are now glueing donuts into the good straws. The large table in the cleanroom can hold 3 to 4 days' worth of straws, we are leaving them there for the donut glue to cure before glueing them into the chamber; this is due to start tomorrow. 1 packet of silver epoxy holds enough glue for about 23 donuts and the dry-fit of the first row took around 1.5h.
Prototype studies
Removing the smaller flowmeter between the gas mixer and the prototype improved the gas mix - results consistent with premixed gas were obtained after doing this. Then at lower flow rate (30 sccm + 30 sccm) and higher cylinder pressure (25psi) some repeatable but inconsistent with the previous set of results were obtained. (Naomi later phoned MKS to ask at what pressure the MFCs were calibrated (with N2), this was 15psi but apparently the supply pressure should have very little effect on the obtained flow rate... )
Some strange results where the shape of the 55Fe energy spectrum changes as the collimated source is moved across the tube were discussed. Beni suggested that O2 might be causing the signal amplitude to decrease for longer drift times. Lubomir suggested repeating with 90/10 Ar/CO2 mix.
Integrating the cosmic events over 750ns (max drift time) produced a nice histogram with a peak between the escape and full peaks from 55Fe, which is where it should be... although, the 55Fe signals were integrated over 96ns because the trigger for these is generated by the ADC.
