Basic concept

The NSW chambers are assemblies of Micromegas monolayers, TGC’s and spacer/stiffeners.In order to simplify the assembly procedures we propose to construct the monolayerssuch that:

- they are sufficiently strong, rigid, stiff, and gas tight that they can be manipulated,transported, fully tested, stored, and approved or rejected;

- The thickness (height) of a monolayer has a tight tolerance of 5 μm;

- Each monolayer has (X,Y) reference markings to the strips, in up to four corners;

- monolayers can consist of more than one AB or CB board, allowing arbitrary larger sizes;

- The monolayers can be assembled by all possible means (glueing, external clampingframes, through-going bolts, nylon wire stitching).

Essential construction element: the monolayer

Monolayer material minimalisation: only AB, CB, drift spacers and seal strips at edges

- Monolayer is glued together and is NOT repairable;- does not deform under gas pressure;- has a precise height (thickness): var < 5 μm;- allows the thinnest possible (low cost, good thickness precision) pcb’s (R&D);- drift spacers in gas (drift) volume: ~100 pcs per m2 (R&D)) such that:

- small dead surface for track detection;- drift spacer induced discharges: should not occur (R&D).

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Monolayer assembly step 1Spacers on Cathode Boards (CBs)

- non-precision spacer:- height: 4.70 mm (mold injection) for 5 mm drift gap- dia. 5 mm- optional: hollow cylinder: wall thickness 0.8 mm: allows assembly by layer stitching

- Spacer pitch: square pattern, pitch 100 – 200 mm (R&D)

- Cathode Boards (CB): single sided (segmented) CuThickness tolerances: subject of (R&D)

- Tool (template) for rapid positioning of spacers

- Apply UV curing glue (check ageing effects(R&D))

DriftSpacer Application Tool

• Use UV curing glue, cured by UV LEDs (ageing tests R&D)• apply 100 spacers on CB in 30 minutes per m2

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UV-LED

Spring (cushion)

O-ring

CB

Ref

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Resistive silk screen printing on Anode Board (AB)Photoresist Avalanche Gap Pillars + DriftSpacer Pedestals

AB + photoresist pillars

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Mesh on Anode Board

Mesh-in-frame

Preparation (in design) of the Anode Boards (ABs):

AB (0.8 – 1.0 mm)

Micromegas

Micromegas support(photo resist)

Pedestal for spacerdia. 5 mm

Granite flat table

Construction of monolayers

CB + spacers + edge gas seals

AB + pillars + pedestals

Bridge: assembly of straight edges + CB board suckers

Granite flat table

Construction of monolayers

Gauge blocks: define thickness monolayer (σ < 5 μm)Gas seals at edges: undersized, glue sealed

Mesh fixation in plane

Plan

e Ed

ge S

eal

Edge

dyk

eD

riftSp

acer

Pede

stal

Drift

Spac

er

Epoxy Glue Epoxy Glue

AB board

CB board

The effect of thickness variations in the AB and CB pcb’s

Muon

ABCB

COG ofprimaryionisationcharge

We measure the COG of theprimary charge of the muon trackin the gas-filled drift volume.This point is displaced in Z and read-outby the strips.As a consequence, the COG (Z) of the driftvolume causes an error dZ . sin (α) in ‘R’.Since the distance between the outsideplanes of the AB and CB boards is precise,the thickness variation of both boardscomes in: equal variation (i.e. bothtoo thick by the same amount) cancelsthe error in the gas layer COG.

dZα

Strategy for tolerance on Z (COG) of drift volume

- a solid MonteCarlo simulation including diffusion (significant at large drift distance)with dR/dZ as a function of the radial distance as result;

- a systematical study of the thickness variations of commercial pcb’s in termsof thickness, batch, position on board (edges, corners)

- Selection of boards: combining selected AB and CB boards for chamber sections- at large radial distance.

Two tools are required for the production of monolayers:

Tool 1: granite table with thick vacuum sucker sections to permit doubling pieces;

Tool 2: bridge to keep top plane of (assembly of) CB boards in plane within 5 μm.

Granite flat table

Tool 1: granite table with sucking fixators

Large monolayers (combination of 2 or more ABs):

• Glue strip ends together with (permanent) aux. joint plate (doubling piece)• interconnect (wire bond) strips• The pattern of the sucking pad’s leaves space for the doubling pieces• The sucking pads have a precise height (thickness) ~ 3 μm (mesh + Si rubber)

sucking pad

ABCB

doubling piece

Tool 2: bridge to keep top plane of CB boards in plane within 5 μm

Carbon fiber frame

The Bridge is an assembly of straight edges with spacing equal tothe pitch of the drift spacers (~ 100 mm).

Granite flat table

Fix sucking pads (= Y ref) at bottom of straight edge by means of flat table.Elimination of non-flatness of granite table!

Sucking pads

Granite flat table

straight edgesPitch equals drift spacer pitch

lifting mount

Granite flat table

Construction of bi-layers (doublets)

Assembly of:- two monolayers- spacer:

- could be (interconnected) bi-spacers (same X,Y position as in monolayer)- could be (machined) honeycomb- could be polyester wire (1.000 mm dia).

- Height verification after assembly

CB

ABAB

CB

(X,Y) alignment of Anode Boards (AB’s):Idea of Saclay: Rasnik code in Cu at upper and lower edges

Granite flat table

Construction of quadlayers Assembly of:- two duallayers- quad spacer:

- could be interconnected spacers- could be (machined) honeycomb- could be plastic wire

Height verification after assembly

Spacer (stiffback, cross plate,longbeam, InPlane Rasnik systems)

Quad layer

Granite flat table

Construction of chamber stations

Assembly of:- two quadlayers- spacer:

- made from G10 plates, bars, profiles- has 3 or more external temporally references: only precise in length (height).- includes Rasnik InPlane system (2 cams, 4 diff. plates, 4 light sources)

readout during construction (calibration: ‘straight’ values).

USB Pixel CMOS chip (taken out 10 $ webcam)

Diffraction Plate

lasers (out of pointer!) Readout USB webcam:any processor

Quad layer

Granite flat table

Construction of chamber stations: fixing the 2nd quad layer

Quad layer

Spacer (stiffback, cross plate, longbeam, InPlane Rasnik systems)

Granite flat table

Alignment of Micromegas PCB (AB):- Integrate Rasnik mask in Cu of all ABs:- Record (X,Y) positions in each corner (4x) by means of 4 cam’s- adjust (X,Y) position of each corner by means of (X,Y) actuator at each corner,

at each monolayer- Also Z values can be measured (quality control)!

Cam

Actuator