Minutes of BBB-meeting with Mirion on Februar 9, 2022.
Topic: Detectors for AHEPaM demo model and implications for flight model.
Attendees:
Mirion: Jyttte Elseviers, Matthieu Morelle
CAU: Stephan Böttcher, Björn Schuster, Lars Seimetz, Patrick, Kühl, Bob Wimmer-Schweingruber
\begin{enumerate}
\item
Do you have any Solar Orbiter HET A \& B detectors left over that we could purchase for the demo model?
Mirion still has 6 wafers but needs to re-assess them. A little suspicious whether they can be used.
3 A and 3 B detectors per wafer, so a total of 18 A plus 18 B detectors. Could characterize in a few weeks. CAU would need detectors in summer 2023, if we proceed to phase 1.
\item We would like you to glue an HET A detector onto an HET B detector. In the following I will call such glued detector pairs "detector sandwiches".
In principle yes, critical because the two are of a different size. Would need a front to back connector, should be OK. Glueing done once the larger detector has been mounted to the carrier. It would be OK if the B detector is not supported around the entire edge. \newline
\mir Miron will look into using a different epoxy which can be cured at lower temperature. \newline
\mir Matthieu: check material and get by to CAU (2022-02-17)
\item We would need 5 such pairs, plus about 2 reserve. Are there enough Solar Orbiter HET A\& B detectors left at Mirion?
This should be OK, as there are 18 AB pairs left.
\item If there aren't enough Solar Orbiter detectors left over, we would want such "detector sandwiches" made from commercial off-the-shelf detectors. Those would be PD900 glued onto
PD1200 detectors (each 500 micron thick). We understand that the 500 micron PD900 and PD1200 are actually fully depleted.
Not needed.
\item Just as a matter of interest: How would the cost for such a "commercial detector sandwich" compare with one made from new, 500 micron HET A\&B detectors, that you would
fabricate using the existing masks?
Not needed, will go with 300 micron Solo detectors.
\item We would, as usual, supply the carriers, but see next question.
Already clarified, \newline
\cau CAU to update carrier design to accommodate HET detector pairs. (2022-03-15)
\item Do you have experience with carrier materials with similar CTEs as your detectors? We expect large thermal stresses with the large detectors bonded to off-the-shelf carrier material.
Ceramics: Only limited experience with smaller detectors and Al-oxide, LTCC, but not clear whether delta-CTE is any better. Also only for smaller sizes. For cryogenic applications Mirion uses different material.\newline
\mir Mirion: check what the material is and check delta-CTE. (2022-02-17)
\item The old question: For the flight model (not the demo model), we originally wanted our largest detectors to be 120 mm in diameter but you told us that you can't offer that. In
the mean time you said that you had experience with the KIT detectors which were larger than 100 mm in diameter. How large would you feel comfortable to go?
Processing done on 5 and 6 inch wafers. Could deliver full wafer, but still need some space (~10 mm) plus extra space for alignment marks.
Supply of 6-inch wafers may give less choice in resistivity. Full depletion for 500 micron detectors would be ~120 V.
On 5-inch wafer can not accommodate 120 mm diameter detector. But it would be nice to cut the wafer and then glue it to the carrier without needing to cut off any edges. Of course, the larger the area, the larger the chance of a defect. Mirion also need some space to handle the detectors/wafers.
Yield will be a risk for very large detectors. Leakage current in the outer segments is less critical than that in the inner segments. \newline
\mir Mirion: Drawing of flats of 5-inch wafer (2022-02-17)\newline
\mir Mirion: Provide drawing of what they believe is a feasible maximum detector. (2022-03-15)
\item Could you provide us (for the demo model) with such a piece of Si for the "large detector" onto which a smaller detector is glued. We do not need a real large "detector
sandwich", it does not need to be functional, but would like to integrate such a piece in the demo model which will undergo structural and thermal testing (shake and bake). We
want to make sure that it will survive launch and commissioning.
In principle Mirion could supply a large non-functional wafer and bond a smaller (HET B) detector to it which would be functional. CAU would supply the carrier board.
