tray (4)
Narrow 50-cm prototype

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This prototype uses the triangular scintillators, with only 3 16-fiber rows per layer (out of 12 for a 50cm-wide panel), but the full 4-layer height.

Need for 4 layers: 
	- 2 24x24" carbon-honeycomb sheets, cut in thirds
	- plus 2 end pieces for connectors
	- 2 80-20 frames
	- 80-20 clips (small)
	- panel joiners
	- M2 screw handle
	- drill guide (2x4 cm)
	- drill guide (10cm)
Trays
I made a parametrized version of the tray (in Fusion, lhcb->layerb), so I can quickly make A, B, C and D. The parameters correspond to the boundaries between blocks. (notes) 
        A    B   C    D
  ---------------------
  dd1  30   30  30   60 
  dd2  90   90  90  120 
  dd3 180  150 180  210 
  dd4 305  240 270  340 
  dd5 445  375 410  500 
  dd6 500  500 500  500
For A and C, we need the yellow parts, for B and D, the RGB parts.

layera_1.stl, layera_2.stl, layera_3.stl,
layerb_7.stl, layerb_8.stl, layerb_9.stl,
layerc_1.stl, layerc_2.stl, layerc_3.stl,
layerd_7.stl, layerd_8.stl, layerd_9.stl,



Covers
Same as trays, these are parametrized. In Fusion lhcb->'layer a top'.

layeratop_1.stl, layeratop_2.stl, layeratop_3.stl,
layerbtop_7.stl, layerbtop_8.stl, layerbtop_9.stl,
layerctop_1.stl, layerctop_2.stl, layerctop_3.stl,
layerdtop_7.stl, layerdtop_8.stl, layerdtop_9.stl,



Connectors
OK, so we're not getting connectors with thumbscrews from Fermilab or any other place, so we brew our own. Also, there are now objections to any metal components.

Connectors using nylon M2 nuts and screws

M2 screws at McMaster 96295A702, specs
M2 nuts at McMaster 93800A300, specs

conn_m2_in.stl
conn_m2_out.stl

The dimensions of the M2 nut means the connectors have to be thicker (8mm), which means the holders and tops need to be redesigned.

Using these conncetors, I redesigned the holders and holder covers, using 2 parameters. In Fusion look for lhcb->newnew_connectors. 
    H(mm) angle    holder stl        top stl
---------------------------------------------
 A   6.86   15 holder_par_a.stl top_par_a.stl
 B   7.86   15 holder_par_b.stl top_par_b.stl
 C   7.86   15 holder_par_c.stl top_par_c.stl
 D   8.21   10 holder_par_d.stl top_par_d.stl
 E  10.46    5 holder_par_e.stl top_par_e.stl
 F  14.38    0 holder_par_f.stl top_par_f.stl



A little tight. Here is the next version: 
    H(mm) angle    holder stl        top stl
---------------------------------------------
 A   6.86   15 holder_par_1.stl top_par_1.stl
 B   7.86   15 holder_par_2.stl top_par_2.stl
 C   8.26   15 holder_par_3.stl top_par_3.stl
 D   8.9    15 holder_par_4.stl top_par_4.stl
 E   9.9    10 holder_par_5.stl top_par_5.stl
 F  13.4     0 holder_par_6.stl top_par_6.stl

And the corresponding tops: 
    A top_par_1.stl    top_par_21.stl    top_par_31.stl
    B top_par_2.stl    top_par_22.stl    top_par_32.stl
    C top_par_3.stl    top_par_23.stl    top_par_33.stl
    D top_par_4.stl    top_par_24.stl    top_par_34.stl
    E top_par_5.stl    top_par_25.stl    top_par_35.stl
    F top_par_6.stl    top_par_26.stl    top_par_36.stl
assemble the frame. Drill holes for connectors, using drill guide.
Print trays, scrub back with soap and brillo pad. Check that bridges are clear. Place with double-sided tape
Place connector A and block #1
Place connector B and block #3
Note the fibers go to the left and right of the block 1 fiber pair.
Place connector C and block #5
Place connector D and block #6
Use a bridge underneath
Place connector E and block #4
Place connector F and block #2
Note where 32 fibers pass over block 6, it is hard to get them to all lay side-by-side. Therefore allow 2mm for this.
Also, I had to trim the bottom of the F connector holder so that the fibers from blocks 1 and 3 (from A and B) can fan out.
Green: jig to hold fiber connector while being glued. The to-be-polished face is up a bit from the bottom.
fiber_glue.stl

Yellow: holder for polishing.
polish_holder.stl

Holder for a M2 screw to insert M2 nuts into the connectors.
m2holder.stl

Fiber lengths for layer A:
Block to end add to connector sum measured delta
1 50 cm A 10 cm 60 63.5 3.5
2 47 cm F 0 cm 47 50.3 3.3
3 41 cm B 8 cm 49 52.4 3.4
4 32 cm E 2 cm 34 37.2 3.2
5 19.5 cm C 6 cm 25.5 28.8 3.3
6 5.5 cm D 4 cm 9.5 12.8 3.3
So for A, B, C, D, using delta=3.3cm:

  Block 1 Block 2 Block 3 Block 4 Block 5 Block 6
Layer A 63.3 50.3 52.3 37.3 28.8 12.8
Layer B 63.3 50.3 52.3 40.3 35.3 19.8
Layer C 63.3 50.3 52.3 37.3 32.3 16.3
Layer D 63.3 47.3 49.3 34.3 25.3 (7.5)

We need to cut hundreds of fibers to exact length. Here is a fixture for that: the WLS fiber feeds into a thin plastic hose from the right, is passed over a cutting fixture into another tube, until it hits a stop. The stop is a rod (coat hanger wire), inserted from the left, with some tape at the end. The cutting fixture is a narrow slot to guide a razor blade. This way you can set the stop, cut 16 fibers exactly the same length, then reset the stop and cut the next set. 
 - Insert M2 nuts into a connector using the tool.
 - Place the connector in the gluing jig
 - Mix a small amount of 5-min epoxy
 - lay a line of glue over the holes in the connector
 - insert fibers 4 at a time, pushing so
                  they protrude out the bottom
 - remove connector with fibers
 - clean the jig
Once you get the hang of this, you can do 2 connectors for each epoxy mix before it hardens too much.

Sanding and polishing connectors after gluing. I use these papers: 

    orange: P120
    black: 320, then 600
    blue: xxx
    green: xxx
Then check under the microscope
(21)
Lasercutting the blocks leaves burrs on the channel ends. Clean up with small Dremel bit (or equivalent).
The "F" holders need a little filing to accomodate fiber fanout
For top blocks 2,4,6, insert fibers on the table.
Blocks 1-6 (from the right) of row 1 done, and blocks 1,3,5 of rows 2 ad 3 done
The raised blocks (2,4,6), are supported by 'bridges'. Where there is no surface to support them, they rest on a piece of paper.


layer a bridge 6.0 cm
layer a bridge 12.5 cm
layer a bridge 5.5 cm

Blocks 4,6 of rows 2 and 3 done
All blocks of layer A finished. 
  6×3×16 = 96 scintillators
  96 fibers
  6×3 = 18 connector holders
  18 connectors, M2 nuts
  18 connector covers
  stop blocks, standoffs
  threaded rods, nuts
Fibers light up unde fluorescent room light.

Status of A (22 nov 23)

For the top, just use carbon fiber sheet.
Drill guide drill guide top
AC Standoff block1 stopblock1.stl
AC Standoff block2 stopblock2.stl
Cyl spacer spacer_cylinder.stl
BD Standoff block1 bd_stop_block1.stl
BD Standoff block2 bd_stop_block2.stl
For the next layers C and D we need 
v  80-20 1 inch:
v     - 2x >90cm cm long,
v     - 2x 19.5 cm
v     - L brackets: 20
v     - screws and flat nuts: 40
v  carbon fiber panels: aa×bb and cc× dd
v  panel clips: 8
   C tray: 3 pieces
   D tray: 3 pieces
v  bridges: ??
   connector holders: C 3 sets, D 3 sets
v  connectors: C 18, D 18
v   M2 nuts 18+18
   tops: C 3 sets, D 3 sets
v  6-32 rods: 24 for connectors, 13 for cover
v  6-32 nuts 74
Status of B (29 nov 23)
All 4 layers finished, spacing between layers A+B and C+D is 50.0 cm
Some readout ribbons connected
Same, cover removed
View from the other side
Cluseup of an output ribbon. Looks like superglue was used, also the bottom fiber looks bent at the connector exit.

→ We need strain relief brackets.

Hubert van Hecke
Last update Sep 2024
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