Hcal

Geometry and Assembly

CLIC Meeting - LAPP

December 2008, 15th

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Study of a new Hcal geometry……motivation: « cracks »

in the calorimeter

Classical geometry

( muons are lost, hadrons ? )

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Study of a new Hcal geometry…

Same internal & external boundaries (2 regular dodecagons)

Projective configuration Tilted configuration

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Proposal of Hcal assembly

Detail of 2 modules

Detection layer

Steel interaction plate

Stairs shape

Objective : to fix the steel plates together to obtain a structure in which the detection layers can be inserted (like drawers).

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Proposal of Hcal assembly

Detail of a module assembly

Using of several stringers along the modules to fix the steel interaction plates together

Complementary shapes

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Study of a new Hcal assembly…

Left-shifted stringers

Right-shifted stringers

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Proposal of Hcal assembly

Shifted stringers Gain of volume / No “air” gap

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Study of a new Hcal assembly…

To realize a belt to fix the modules together thanks to screws

Possibility of multiple belts along the length of the barrel !

NB: Belt maybe out of scale…

Drawback : increase of the overall dimension

Belt

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Study of a new Hcal assembly…

Possibility of several belts along the barrel, whose shapes could be full

rectangular, or I profile, etc…Cf. Atlas experiment

Cf. DELPHI

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Study of a new Hcal assembly…

Integration with ECAL

No crack in the 2

detectors

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Study of a new Hcal assembly…

3D view

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Study of the Hcal forward

Face viewTop view

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Study of the Hcal forward

Top view

Beam axis

Only absorbers are represented

Minimize the space betwwen the 2 absorbers of the same plane

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Study of the Hcal forwardAssembly procedure

Muons detector

The first 2 absorbers are fixed on the muon detector

Blue parts are screwed on absorbers

Their thicknesses are the same than the ones of chambers, i.e. 8 mm !

The following absorbers are screwed on the blue parts

Counterbored holes in spacers (blue parts)

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Study of the Hcal forward

Chambers insertion

No crack in the Hcal end-cap

Planes of the blue parts are non projective

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Study of the Hcal forward

Inserted from the left

Inserted from the right

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Study of the Hcal forward

Chambers insertion

3D view

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Prospects

Perform Finite Element Analyses (FEA) :

• Computations of displacements/stresses of the structure

check stresses near the fixation locations: Fixation of the Ecal modules on the base of Hcal modules. Fixation of the whole structure on the cryogenic magnet.

check displacements of the structure : displacements of the modules with respect to the beam axis. displacements of the interaction plates (sufficient margin between 2 consecutives interaction plates to insert chamber).

• Optimization of the stringers thickness(= maximization of the size of the chambers)

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Prospects

Tungsten Stainless Steel

Absorption length λ (mm) 95.855 167.598

4.5 x λ (mm) 431.3 754.2

Absorber thickness (mm) 10.8 18.9

1 layer thickness (mm) 18.8 26.9

Calorimeter thickness (mm) 752 1076

External radius (mm) 2247 2583

NB : absorber thickness depends on the number of layers: 40 layers in this case !

Hcal made of Tungsten will be obviously more expensive than using Stainless Steel.

Nevertheless it drastically reduces the cost of the solenoid and the muon system !

OPTIMIZATION (need for physic simulation…)

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Prospects

Hcal & Ecal divided into 16 modules

Other configuration :

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Last comments

• The Hcal modules are not projective, but internal cracks can appear (due to bad layout of chambers).

• The modules must be fixed together, the Hcal has to be inserted and fixed inside the coil.

Spaces / clearances for Mechanics (and services) must be taken into account !

The external radius of the Hcal is NOT given by the circle which passes through the tip of the last chamber…

To take into consideration in Physics simulation !!!

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Prospects

16 modules configuration :Hcal structure still symmetric

Drawback : 16 spaces without detection (+4)

Advantages :

Smaller modules= smaller interaction plates & chambers

Stiffer modules (less problem of flexion)

Thinner stringers (smaller spaces without detection)

Lighter modules (manoeuvrability)

Reduction of loads (force & torque)

on each Hcal module (due to Ecal modules)

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Study of a new Hcal assembly… Wouldn’t it be possible to put locking devices

at 5 & 7 o’clock ?

Maybe more simple parts at 5&7 o’clock than 3&9 o’clock (compression and no torque…no flexion!)

Maybe a great benefit considering the overall dimension (magnet internal radius)

DELPHI

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Study of a new Hcal assembly… Wouldn’t it be possible to put fixation devices

at 5 & 7 o’clock ?

Case of a fixation at 3 o’clock :

Parts really under-estimated (because of torques, etc…)

Parts under compressionMinimal magnet internal radius ???