Difference between revisions of "Minutes-9-8-2011"
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*One wire was broken at the standard place, between the pad and the epoxy. Casey fixed it already. Beni asked if this is a "standard place", how we can mitigate the problem. Dave: before soldering we started putting additional epoxy at that place that reduced the number of broken wires, so after that this is the first wire that we found broken. Beni and Bill discussed if this was caused by a frame deformation. | *One wire was broken at the standard place, between the pad and the epoxy. Casey fixed it already. Beni asked if this is a "standard place", how we can mitigate the problem. Dave: before soldering we started putting additional epoxy at that place that reduced the number of broken wires, so after that this is the first wire that we found broken. Beni and Bill discussed if this was caused by a frame deformation. | ||
*One cathode channel didn't have a good contact; it passed the test with the diode testing card, but when we checked it with a generator the signals were attenuated. Re-heating the conductive tape for 30 sec solved the problem. However, after finding this we checked all the channels with a generator and found another bad channel. In this case re-heating for 30 sec didn't help. Casey decided to try re-heating for 60 sec and this time it helped. | *One cathode channel didn't have a good contact; it passed the test with the diode testing card, but when we checked it with a generator the signals were attenuated. Re-heating the conductive tape for 30 sec solved the problem. However, after finding this we checked all the channels with a generator and found another bad channel. In this case re-heating for 30 sec didn't help. Casey decided to try re-heating for 60 sec and this time it helped. | ||
| − | *On the two wire frames that will go in the first package we found several broken resistors, some at the signal and some at the HV side. These are 1MOhm current limiting resistors. Most likely they were broken during the ring lamination when putting lead bricks on the top to make the ring flat. We were using cork pads bellow them, but Bill suggested another ( | + | *On the two wire frames that will go in the first package we found several broken resistors, some at the signal and some at the HV side. These are 1MOhm current limiting resistors. Most likely they were broken during the ring lamination when putting lead bricks on the top to make the ring flat. We were using cork pads bellow them, but Bill suggested another (polyethylene based) material. Also for the future we should try putting the bricks on ant elements on the boards. |
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*testing the resistors on the wire frames (with an ohmmeter) before stringing. | *testing the resistors on the wire frames (with an ohmmeter) before stringing. | ||
*testing the wire channels by applying step function with a generator on the +HV and locking with a scope at the individual channels at the connector | *testing the wire channels by applying step function with a generator on the +HV and locking with a scope at the individual channels at the connector | ||
| − | *testing of the cathode channels can be done with a generator (suggested by Anatoly) but it will require applying the signal on the other side of the strip which is not possible for the short strips in the middle. Another way is to induce the | + | *testing of the cathode channels can be done with a generator (suggested by Anatoly) but it will require applying the signal on the other side of the strip which is not possible for the short strips in the middle. Another way is to induce the signals on all the strips but laying a cable from the generator on the top of the cathode. This method was used now to check all the cathodes for the stack. Probably the easiest way to do it is just to measure the resistance of the contacts. |
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== Engineering == | == Engineering == | ||
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== Electronics == | == Electronics == | ||
| − | - | + | - Information from Chris before the meeting: all rigid-flexes were tested and found 5 (out ~500) that can't be easily fixed and will be shipped back for repair. In any case we have enough for the production. |
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| + | - As discussed for the tests above we need to look at the wire and strip signals (or measure resistance) at the daughter card connectors. For that we need a card similar to the cathode testing card, same connectors on both sides but just with straight through traces to bring the signals outside of the frame. Chris will make such cards. | ||
== Chamber testing at 126 (cell #2) == | == Chamber testing at 126 (cell #2) == | ||
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- Lubomir showed drift time spectra (FDC logbook page 576) for two very high HV for this gas mixture (pre-mixed 89.8/10.2 Ar/CO2): 1800V and 1875V. Certainly there's strong dependence of the drift time on the HV and at 1800V it's much flatter. It will be interesting to compare with the results at 1650V that Beni has. Also, additional studies of the deadened area were done placing the 55Fe source in the middle of the chamber and triggering with one of the central wires. Plotted on page 577 are the number of counts on the top strips; note that 12 strips cover the part of the central wire that is deadened. One concludes that the counting on the strips at the edge of the area is reduced by a factor of 100. Note also that the source was 1cm above the wires and the gamma flux in the middle is ~9 times higher than at the edge of the deadened area. At the same time the strips in the middle don't reach the central wire by 1.8 cm. | - Lubomir showed drift time spectra (FDC logbook page 576) for two very high HV for this gas mixture (pre-mixed 89.8/10.2 Ar/CO2): 1800V and 1875V. Certainly there's strong dependence of the drift time on the HV and at 1800V it's much flatter. It will be interesting to compare with the results at 1650V that Beni has. Also, additional studies of the deadened area were done placing the 55Fe source in the middle of the chamber and triggering with one of the central wires. Plotted on page 577 are the number of counts on the top strips; note that 12 strips cover the part of the central wire that is deadened. One concludes that the counting on the strips at the edge of the area is reduced by a factor of 100. Note also that the source was 1cm above the wires and the gamma flux in the middle is ~9 times higher than at the edge of the deadened area. At the same time the strips in the middle don't reach the central wire by 1.8 cm. | ||
Revision as of 15:37, 9 September 2011
September 8, 2011 FDC meeting
Contents
Agenda
- Production Construction Tracking (Dave)
- Status
- Additional testing procedures
- First package tests (Lubomir)
- Engineering update (Bill)
- Electronics update (Chris)
- New testing card for the cathodes
- Chamber testing at EEL126 (cell#2) (Beni)
- Other
Minutes
Participants: Bill, Dave, Simon, Beni, Elton, Mark, and Lubomir.
Production
- Dave: The capacitors were changed on all wire frames needed for the first production package. Wires frame #6 was populated, wires deadened and will be put in package today or tomorrow. Wire frame #7 is out of the stringing table and Chris will put the elements on it tomorrow. The last two cathodes for the first package: started putting the rigid-flexes on type-1; on type-2 the frame was glued and on Monday the Mylar foil will be glued.
- After testing the first cell of the production package we found the following problems:
- One wire was broken at the standard place, between the pad and the epoxy. Casey fixed it already. Beni asked if this is a "standard place", how we can mitigate the problem. Dave: before soldering we started putting additional epoxy at that place that reduced the number of broken wires, so after that this is the first wire that we found broken. Beni and Bill discussed if this was caused by a frame deformation.
- One cathode channel didn't have a good contact; it passed the test with the diode testing card, but when we checked it with a generator the signals were attenuated. Re-heating the conductive tape for 30 sec solved the problem. However, after finding this we checked all the channels with a generator and found another bad channel. In this case re-heating for 30 sec didn't help. Casey decided to try re-heating for 60 sec and this time it helped.
- On the two wire frames that will go in the first package we found several broken resistors, some at the signal and some at the HV side. These are 1MOhm current limiting resistors. Most likely they were broken during the ring lamination when putting lead bricks on the top to make the ring flat. We were using cork pads bellow them, but Bill suggested another (polyethylene based) material. Also for the future we should try putting the bricks on ant elements on the boards.
- All the above findings suggested that we need to do more tests before stringing and before stacking the wire frames and the cathodes:
- testing the resistors on the wire frames (with an ohmmeter) before stringing.
- testing the wire channels by applying step function with a generator on the +HV and locking with a scope at the individual channels at the connector
- testing of the cathode channels can be done with a generator (suggested by Anatoly) but it will require applying the signal on the other side of the strip which is not possible for the short strips in the middle. Another way is to induce the signals on all the strips but laying a cable from the generator on the top of the cathode. This method was used now to check all the cathodes for the stack. Probably the easiest way to do it is just to measure the resistance of the contacts.
Engineering
-
Electronics
- Information from Chris before the meeting: all rigid-flexes were tested and found 5 (out ~500) that can't be easily fixed and will be shipped back for repair. In any case we have enough for the production.
- As discussed for the tests above we need to look at the wire and strip signals (or measure resistance) at the daughter card connectors. For that we need a card similar to the cathode testing card, same connectors on both sides but just with straight through traces to bring the signals outside of the frame. Chris will make such cards.
