GLAST LAT Tracker Tower-4/5 Pre-Ship Review

1. GLAST LAT Tracker Tower-4/5 Pre-Ship Review Luca.latronico@pi.infn.it INFN-Pisa

2. Tower 4 - Assembly and test highlights • Apr. 13-14, 2005 (INFN-Pisa) : • assembly of complete tray stack • incomplete cable set (C0,C1,C3,C5,C7) due to late arrival of complete set • CPT could not be performed w/o cables C2, C4, C6 due to a known issue with GTFE reset (see NCR/INFN/PI-417) • Apr. 18-21, 2005 (INFN-Pisa) : • Installation of late cables • Tray01 (L020) damaged during cable assembly - L023 installed in place of L020 (NCR/INFN/PI-470) • CPT • Sidewalls and alignment • Final CPT and ship to Roma • Apr. 27, 2005 (Alenia-Roma) : • VIB test • May. 23-27, 2005 (Alenia-Roma) : • TVAC test with tower 5 • May 30, 2005 (Roma) • Through customs in Roma airport • Full EIDP details at: • http://glast.pi.infn.it (soon available)

3. Tower 4 - Assembly and components details Tower PN: LAT-DS-00722 (rev3) Tower SN: 4

4. Tower 4 & 5 - Configuration Configuration: • Kapton tape and foam applied on the flex cables as per LAT-DS-00722 • 4 layers of Poron foam 0.037 THK used on Bottom and Top Tray (–X) side (in place of 5 layers) • Base Plate assembly: • Torque of nuts 5.1 Nm on TWR 4 • Torque of nuts 5.3 Nm on TWR 5, spec is (5.08 +0.56/-0 Nm)  higher resonance frequency detected at VIBE test

5. Tower 4 & 5 – Alignment, CG & MASS • Tower 4 and 5 well aligned and inside stayclear • Mass and CG near estimated values (when used real masses) • Data available on INFN-PISA web site

6. Tower 4 – Open NCRs • INFN/PI-494: Bad channels out of spec • with reference to tray NCRs 460,465,464, 463 (all closed as per MRB) layers X6, Y5, Y3, Y13 fail test TE301 as expected and due to known problems • Status of channels was monitored through TVAC test and show no significant loss of channels (see next slide), the NCR can be closed and converted into a SLAC one for reference. • INFN/PI-496: Vacuum level out of specification. • Common to Tower 5, see following slides. • INFN/PI-503: CPT reduction after TVAC • Common to Tower 5, see following slides

7. ~ 130 disconnected channels overall (less than 0.25%). Layer X6 is stable as bad channels are due to broken PA traces Fluctuations in layers Y3 (H17-back-MCM 1117)and Y5 (H16-back-MCM 1049)are due to delaminations in the MCM encapsulant – such MCMs were out of spec (>20 bad chans) already at SLAC and their use was authorized by an MRB for schedule reasons

8. Tower 4 - Efficiency 3 layers with efficiency < 99% as a consequence of missing channels (see previous slide) overall efficiency (pre-ship) at the tower level is 99.7% (required 98%)

9. Tower 5 - Assembly and test highlights • May 5-9, 2005 (INFN-Pisa) : • assembly (tray stack, cables, sidewalls, alignment, turn-over) • test (CPT) • May. 23-27, 2005 (Alenia-Roma) : • TVAC test with tower 4 • VIB test • May 30, 2005 (Roma) : • Through customs in Roma airport • Full EIDP details at: • http://glast.pi.infn.it (soon available)

10. Tower 5 - Assembly and components details Tower PN: LAT-DS-00722 (rev3) Tower SN: 5

11. Tower 5 – Open NCRs • INFN/PI-492: Bad channels out of spec • 18 bad channels found in Pisa on X2 (9 dead, 9 disconnected) • 7 dead were known from ladders • nb of dead channels was stably 7 during TVAC; a fluctuation in the Pisa measurement determined the 9 dead channels initially recorded • Status of channels was monitored through TVAC test and show no loss of channels (see next slide), the NCR can be closed. • INFN/PI-496: Vacuum level out of specification. • Common to Tower 4, see following slides. • INFN/PI-504: CPT reduction after TVAC • Common to Tower 5, see following slides

12. ~ 45 disconnected channels overall (~0.08%). • All layers within specs, i.e. nb of bad chans <16, and stable • new MCM encapsulant deposition, new MCM-PA gluing fixture, new shipping box are working!

13. Tower 5 - Efficiency worst layer is 99.4% overall efficiency (pre-ship) is 99.7%

14. EGSE/TVAC – Communication problems with 2 towers • Relevant NCR: • INFN/PI-474 • Problem: • Some instabilities in the EGSE systems for TVAC made it impossible to operate towers 1 and 3 during TVAC test, and the EGSE systems had to be operated independently • Action taken (as per dispositions): • TVAC chamber setup was improvedby using separate feed-through for EGSE-power lines and chamber temperature control • GASU cables connecting to the TEMs were shielded • Findings • TVAC test of towers 4 and 5 was run with 2 systems in parallel, the NCR can be closed

15. Tower 4 and 5 – Vacuum level out of spec • Relevant NCR: • INFN/PI-496, INFN/PI-497 • Description: • The vacuum level was mostly outspec during the test (specs call for 5E-5 torr) • Observations (see annex for details): • P ~ 3.15E-5 torr at room T after 90 hours of pumping • correlation between T-P • no improvement after hot soak as observed with towers 1 and 3 • new material (MLI) that did not undergo bake-out was introduced for thermal blanket of tower 4 and EGSE RF shield • The proposed disposition is use as is.

16. CPT reduction for TVAC • Reference NCR • 504 • Description • TE101 (leakage current and power consumption test) not performed on tower 5 after TVAC test • Proposed dispositions • only perform test TE101 after TVAC is anomalies are detected in the tower CPT suite • Rationale: correct behaviour of tower during and after TVAC is assessed by observations of layers noise, channels status, CR detection efficiency • reduce CR data taking time to 100k events for CPT and 50K for LPT • Rationale: such statistics are enough for efficiency measurements and the test time reduction allow compressing TVAC in 3 days • Submit a document change request with the above changes

17. Tower 4 and 5 - Conclusions • Both towers well aligned and within stayclear • The overall number of disconnected channels is very low • All the silicon layers (but the bottom tray of tower 3) close to 100% efficiency • Communication issue during TVAC solved • Vacuum level still outspec during TVAC