Si disk with tiles

RSU_DRAWING_SUMMARY.md

@@ -0,0 +1,211 @@
+# RSU Drawing Summary
+
+Source: `rsu.pdf`
+
+The PDF is a single raster drawing, so the values below were read visually from the rendered page. All dimensions appear to be in millimeters.
+
+## Clearly Readable Dimensions
+
+### RSU / Sensor Strip
+
+```text
+RSU pitch / length along module long axis: 21.67
+RSU active/sensor width:                  19.56
+Six-RSU strip length:                    136.02
+```
+
+The six-RSU strip length is consistent with:
+
+```text
+136.02 = 4.50 + 6 * 21.67 + 1.50
+```
+
+Interpreted as:
+
+```text
+left margin before RSU chain   = 4.50
+six RSUs                       = 6 * 21.67 = 130.02
+right margin after RSU chain   = 1.50
+total strip length             = 136.02
+```
+
+### Full Module / Package Envelope
+
+```text
+full package length: 152.02
+full package width:   30.00
+inner width marker:   29.00
+```
+
+The full package length is consistent with:
+
+```text
+152.02 = 11.00 + 136.02 + 5.00
+```
+
+Interpreted as:
+
+```text
+left external/package extension   = 11.00
+central six-RSU strip             = 136.02
+right external/package extension  = 5.00
+full package length               = 152.02
+```
+
+### Width Direction / Carbon Fiber Support
+
+The carbon fiber support has a main width of `29.00`, plus `3.00` mm associated with the bottom-edge cut features.
+
+The bottom edge cutouts are:
+
+```text
+bottom-left cutout:   3.00 x 11.00
+bottom-right cutout:  3.00 x 5.00
+```
+
+So the support is not a simple rectangle if these edge cuts are represented explicitly. A simplified envelope model could use the full package outline, while a more detailed support model should subtract or omit these two bottom-edge rectangles.
+
+### RSU Width Within Support
+
+The RSUs are narrower than the carbon fiber support. The drawing gives top and bottom margins of:
+
+```text
+top margin:     6.22
+bottom margin:  6.22
+```
+
+Using the existing/read RSU width:
+
+```text
+RSU width = 19.56
+```
+
+the vertical span is consistent with:
+
+```text
+6.22 + 19.56 + 6.22 = 32.00
+```
+
+This supports the earlier `32 mm` corrugated/support envelope assumption for the RSU region, while the drawing also shows a `30.00 mm` package/support width marker in another view. This should be resolved before finalizing the module envelope convention in code.
+
+## Other Visible Callouts
+
+The following dimensions are visible in smaller end/detail views and should be treated as drawing-read values until cross-checked against the CAD/source model:
+
+```text
+edge clearance values:       0.50, repeated at ends
+small end feature:           2.40
+side/end view width:        30.00
+side/end active width:      19.56
+RSU top/bottom margins:      6.22 each
+curvature radius:            R5.12
+small rectangular feature:   4.00
+```
+
+Additional left-side FPC/readout-looking feature callouts:
+
+```text
+10.00
+9.30
+17.00
+15.00
+7.00
+5.39
+5.00
+1.00
+diameter 1.50
+```
+
+## Constants Already Matching the Drawing
+
+The existing XML constants in `compact/tracking/silicon_disks_modules.xml` match the drawing well:
+
+```xml
+<constant name="SiEndcapRSU_width"  value="19.564*mm"/>
+<constant name="SiEndcapRSU_length" value="21.666*mm"/>
+```
+
+These correspond to the visible drawing values:
+
+```text
+RSU width  ~= 19.56
+RSU length ~= 21.67
+```
+
+## RSU Inactive-Region Assumptions
+
+The current geometry implementation uses a simplified tile-level RSU approximation informed by `1RSU_top_half.png`. This is still an approximation: fine routing traces and detailed metal features are not modeled.
+
+Each RSU is represented as:
+
+```text
+2 divisions along local x  x  3 tile columns per x-half  x  2 divisions along local y
+= 12 active rectangular silicon tile regions
+```
+
+The inactive pieces are represented as passive silicon around or between those active regions:
+
+```text
+backbone width:     0.06
+power-switch width: 0.02
+bias width:         0.06
+periphery width:    0.525
+```
+
+Interpretation:
+
+- `backbone`: narrow inactive strip at the start of each local-x half-RSU. In the current model it runs across the full RSU width in local `y`.
+- `power-switch`: narrow inactive strip after each tile column within a local-x half-RSU.
+- `bias`: narrow inactive strip at the internal boundary between the two local-y halves. It follows the vertex-barrel convention where bias regions sit near the central boundary.
+- `periphery`: inactive strip near the outer local-y edges of the RSU, representing the readout periphery plus pads/dicing lane. The current `0.525 mm` value corresponds to `0.200 + 0.325 mm` from the RSU architecture drawing.
+
+With the current constants, each active rectangle is:
+
+```text
+tile_x = (RSU_length/2 - backbone_width - 3 * power-switch_width) / 3
+       = (21.666/2 - 0.06 - 3 * 0.02) / 3
+       = 3.571
+
+active_y = RSU_width/2 - bias_width - periphery_width
+         = 19.564/2 - 0.06 - 0.525
+         = 9.197
+```
+
+This approximation captures the tracking-relevant active versus inactive silicon pattern while representing the drawing's 12-tile RSU structure. A 6-RSU module therefore has `6 * 12 = 72` sensitive silicon regions.
+
+## Implementation Notes
+
+For a detailed six-RSU corrugated/endcap module, the drawing suggests that the old simplified `130 mm x 30 mm` module footprint is only the approximate six-RSU active pitch region. A more complete package model should likely distinguish:
+
+```text
+RSU chain length:       6 * 21.666 = 129.996
+sensor/readout strip:   136.02
+full package length:    152.02
+full package width:      30.00
+```
+
+Candidate constants for implementation:
+
+```xml
+<constant name="SiEndcapModule6RSU_strip_length"        value="136.02*mm"/>
+<constant name="SiEndcapModule6RSU_package_length"      value="152.02*mm"/>
+<constant name="SiEndcapModule_width_corrugated"        value="30.0*mm"/>
+<constant name="SiEndcapModule_inner_width_corrugated"  value="29.0*mm"/>
+<constant name="SiEndcapModule_support_bottom_cut_width" value="3.0*mm"/>
+<constant name="SiEndcapModule6RSU_left_cut_length"     value="11.0*mm"/>
+<constant name="SiEndcapModule6RSU_right_cut_length"    value="5.0*mm"/>
+<constant name="SiEndcapRSU_y_margin"                   value="6.22*mm"/>
+<constant name="SiEndcapModule6RSU_left_extension"      value="11.0*mm"/>
+<constant name="SiEndcapModule6RSU_right_extension"     value="5.0*mm"/>
+<constant name="SiEndcapModule6RSU_sensor_left_margin"  value="4.5*mm"/>
+<constant name="SiEndcapModule6RSU_sensor_right_margin" value="1.5*mm"/>
+```
+
+Open validation items before final geometry implementation:
+
+- Confirm whether the drawing's `30.00 mm` package width supersedes the earlier `32 mm` corrugated-width assumption.
+- Confirm whether the RSU-region width convention should use `32.00 = 6.22 + 19.56 + 6.22`, while the carbon fiber support/package view uses `29.00 + 3.00`.
+- Confirm whether the carbon fiber support bottom-edge cutouts should be represented explicitly or approximated by a rectangular envelope.
+- Confirm which end features correspond to LEC, REC, FPC, or mechanical support.
+- Confirm material choices for the non-sensitive package extensions.
+- Confirm whether the small left-side detail dimensions should be represented in DD4hep or treated as simplified envelope material.