1. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 1 GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 3B: EM Mini-Tower Robert Johnson Santa Cruz Institute for Particle Physics University of California at Santa Cruz Tracker Subsystem Manager johnson@scipp.ucsc.edu Gamma-ray Large Area Space Telescope

2. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 2 Mini-Tower Objectives Develop and test tray assembly procedures with real electronics and detectors. Test the readout electronics in a realistic environment. Test the detector system with minimum-ionizing particles (cosmic rays). Exercise the TEM based readout with multiple layers and multiple cables. Platform for development of Tracker subsystem test procedures and software that will be needed for flight-module production. Platform for I&T preparations. Note: this device is not intended to be used for environmental testing, mechanical or thermal.

3. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 3 Mini-Tower Configuration The essence: –3 instrumented x,y silicon-strip detector planes –Each x,y plane is preceded by a thin tungsten foil (3% rad. len.) The details: –4 light composite panels supporting SSD ladders –1 bottom tray with no SSD but with the mechanical interface to the grid This is an older prototype tray refitted by COI with preliminary versions of the titanium reinforcement –8 short versions of the readout cables –8 MCMs (2 for each pair of readout cables) The 2 lowest MCMs have no SSDs connected but are required in order to complete the data transmission circuit –Inexpensive aluminum walls

4. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 4 Extra Functional Tray Another tray, instrumented on both sides with SSD and electronics, plus thin converter foils, is being assembled in Italy. This is in addition to the Mini-Tower. This tray will undergo complete environmental testing to qualification levels, including –Random vibration: GEVS (LAT-TD-01004) –Thermal vacuum:  30  C to +50  C (LAT-TD-01037) This will complement the environmental testing of the mechanical- thermal tower module, which will not include functional detectors and electronics.

5. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 5 Mini-Tower Al “grid” fixture

6. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 6 Mini-Tower Bottom Tray Refurbished extra bottom tray from the prototype mechanical tower Titanium and carbon-fiber reinforcement added by COI (intermediate design between the prototype tower and the final Hytec design). Vibration fixture frame Bottom face of the bottom tray Titanium corner reinforcement and flexure blade Stainless Steel

7. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 7 Mini-Tower Electronics 13 functional MCMs were assembled at Teledyne. 6 are in the mini-tower, and 2 more will be on the tray destined for environmental testing. 2 of them are shown below, in protective cases, connected to 2 Mini-Tower readout cables (via connector savers). The cables are connected to a TEM module.

8. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 8 Mini-Tower Tray One of the functional EM trays, inside its service box.

9. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 9 Leakage currents Leakage current remains within specifications for all tested trays (no damage during assembly). The leakage current measured on full trays is in most cases lower than the sum of the single-ladder currents (but ladders were tested at 22º average temperature, while trays were tested at 17.5 º).

10. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 10 Grounding Considerations Handles for assembly/storage fixtures MCM ground point (1 of 3), required scraping off conformal coat Initially the aluminum honeycomb core was floating, resulting in a huge increase of noise when trying to ground the box containing the tray. Good ground electrical contact (handles-honeycomb and MCM-honeycomb) was accomplished through long screws that touch the honeycomb (as was always in the specification). This solved all grounding-related noise problems.

11. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 11 Noise Trigger Rate The noise trigger rate is monitored for each FE chip as a function of discriminator threshold. Residual triggers at high threshold are due to cosmic rays. OR of 64 Channels

12. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 12 Masking Noisy Channels: TS001 Threshold Scan @ 115 V with 7 noisy strips masked With the 7 noisy strips (<0.5%) masked, the behavior of the counting rate as a function of threshold is quite uniform over the whole tray.

13. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 13 Pitch Adapter Issues Threshold Scan at 115 V with 6 noisy strips masked. Problems with the pitch adapters used by Teledyne for the functional EM MCMs resulted in sections of some MCMs in which most strips could not be wire bonded to the SSDs. This leaves holes in the coverage, as illustrated below. This problem with the pitch adapter design has been resolved (Presentation 6E). Region of bad pitch-adapter alignment.

14. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 14 Ruthenium  Source Profile Some noisy strips masked. TG001 Front

15. GLAST LAT ProjectMarch 24, 2003 3B Tracker Peer Review, WBS 4.1.4 15 Cosmic Ray Triggers Number of fired strips per event. Number of clusters per event. TS001 Front