Present: M. Blaszkiewcz, D. Carrillo, S. Georgakakis, L. Feslberger.
The presentation started by covering the sources of failure data used in the modelling process. S mentioned the idea of setting up a failure database to keep track of the component failures, where measurements could be taken on recurring basis in the future.
The next point covered the base assumptions made in the models. The operating temperature proves to be quite elusive, as generally in some cases can be as low as 20, but in some others - 45 and even more, depending on heating from nearby components. D expressed surprise at the fact that it is an important factor for reliability and not only ageing of components.
D also highlighted the impact of the stops, such as Technical Stops, on capacitors: lack of powering leads to their deterioration.
Next important aspect is radiation. The models estimate 25 Gy/year. S suggested seeking synergies with other teams dealing with the subject. He specifically listed impact on transistors energizing/deenergizing, less current, etc. L proposed to check the critical path components specifically from this angle. D further stressed that 1, 2 years may lead to degradation, but shorts of power supply can happen already from the 1st day. A contact person from section dealing with reliability in radiation has been suggested.
The deadline for the study became more relaxed: S suggested that changes will be possible to make until the CHARM tests in April.
L proposed a general plan:
1. Standard FMECA pipeline
2. Confirming critical path
3. Digging into CP components in terms of radiation
In parallel: top-level model.
S assured that there will be testing of the board just as there is of Universal Control crate with a test bench. 1st level testing will concern electrical loads, 2nd level more functional testing (e.g., delay times).
Operating voltages for FET is -5V to 5V, for relay 5V and the other line is 24V. There is change compared to the drawing in S’s presentation: mains are integrated into boards, so they are also redundant.
End-effects:
- Missed opening
- Spurious opening
- Maintenance (may be non-existent in this case)
- No effects
Lifetime aspects may not be necessary as components were chosen with them in mind. Also, the choice of components was usually in favour of ones used in EPC with proven operational value.