The SPD geometry in AliRootThe SPD geometry in AliRoot

Alberto Pulvirenti

University & INFN Catania

In collaboration with:

Domenico Elia (INFN Bari)

Outline: Implementation Volumes & Displacement Material budget estimates Cables and sevices on the cones Outlook

3° Convegno Nazionale sulla Fisica di ALICE

Frascati – LNF, 14 November 2007

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Advantages of ROOT geometry Advantages of ROOT geometry modelingmodeling

Modeler independent from transport code (GEANT3, FLUKA, …)› geometry is implemented once for all transport engines

› easy to be interfaced with the virtual “generic” simulation engine (TVirtualMC)

› easy to swtich among different transport codes

Geometry built with ROOT classes› reusability for reconstruction

› easy to implement (mis)alignment of modules

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Components of a TGeo Components of a TGeo geometrygeometry

[TGeo]Medium:› a tracking medium (material + physical status)

[TGeo]Volume:› a block of material, which represents a part of the

detector

› a box which contains several sub-volumes, in order to be able to replicate a composite structure made of several parts

[TGeo]VolumeAssembly:› a “virtual” space with several volumes inside

useful to manage situations where a group of volumes can superimpose on another group of volumes

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Implementation philosophyImplementation philosophy

Multi-level implementation:› all groups of volumes which are replicated

many times in the whole detector are inserted into an “upper level” container …which will be a TGeoVolume or TGeoVolumeAssembly

depending on how its components are displaced in space

Advantages:› reduces the elements to be checked in case

that corrections are needed

› “logic” of the implementation is more easily readable and followable

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Half-stave architectureHalf-stave architecture

Aluminum-polyimide grounding foil (25 + 50 µm thick) with 11 windows to improve the thermal coupling

Multi-chip module (MCM) to configure and read-out the half-stave

2 Ladders consisting of:• p+n silicon sensor matrix 200 µm thick

with 40960 pixels arranged in 256 rows and 160 columns

• 5 FE chip Flip-chip bonded to the sensor through Sn-Pb bumps [single cell dimensions = 50 µm (r) x 425 µm (z)]

Aluminum-polyimide multi-layer bus to connect the MCM and FE chip

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HALFSTAVE

“BASE”

MCM

“Extenders”

Grounding Foil

Ladder

Uppermost level

Implemented as an assembly, to avoid some overlaps on the sector.

‘Box’ volume containing the grounding foil and the ladders.

Thin cables which go from inside to outside the sensitive area of the SPD.

MCM Cover

Chips inside MCM

Pixel Bus Extender

Sensor

Chips

Kapton

Al

MCM Extender

Implementation levelsImplementation levels

Bumps

Glues

Grease

Alignable

Alignable

Volumes

Volumes

MCM base

Pixel Bus“Base”

Pt1000

Resistors

Capacitors

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Stave architectureStave architecture

1 Stave = 1 “left” half-stave + 1 “right” half-stave“LEFT”-type half-stave

“RIGHT”-type half-stave

Example: couple of half-staves on the outer layer

A - side C - side

z

x

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LadderLadder = 1 sensor + 5 chips + 32 bump-bondings one single

container

bump bondings implemented in “stripes” (1 x column) of- 0.042 mm width- 0.013 mm thickness

guard ring around the sensor

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Grounding foilGrounding foil Complicated shape with holes inside

› holes are filled with thermal grease

Cosisting in two layers (kapton & aluminum)› Small differences in size

Big resistors and capacitors in correspondence of the end of each ladder

Pt1000’s (one per chip)Pixel busPixel bus

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Half-stave assemblyHalf-stave assembly

Glue

CARBON FIBER SUPPORT

Grounding Foil

Glue

Ladder

Glue

Pixel Bus

Needed some room for movement of ladders and half-staves to implement misalignment: this could cause an overlap of volumes.

SOLUTION: reduce glue layer thickness to leave some “free space” around the ladder and between GF and support, without changing the spacing between components

Glue

Glue

Glue

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Pixel bus & extenders (by R. Pixel bus & extenders (by R. Vernet)Vernet) Implemented as “folded” foils Volumes must intrude in each other TGeoVolumeAssembly

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MCMMCM Thin integrated circuit + Chips + Thick cover

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ClipsClips

Component on 3 over the 4 staves lying on layer 2

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Placement on sectorPlacement on sector Use reference points in the support placement planes

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Final appearanceFinal appearance

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Tests (1)Tests (1)what is done on the way along what is done on the way along implementationimplementation Fix coding conventions

› usually done before committing on CVS (by me or Massimo Masera)

Remove overlaps› the volumes must not overlap with each other, because this can

cause the transport of particles to get confused and return meaningless data

› a ROOT facility allows to check overlaps by sampling:1. points are generated randomly in the volume of the complete geometry2. for each point it is checked if it belongs to more than 1 volume3. an alert is raised when this happens an overlap is present

somewhere

Event generation in AliRoot with new geometry› check execution CPU time to detect anomalous increases due to

slow geometry creation (e.g. due to a too large amount of volumes)

› make sure that no run-time errors are raised

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Tests (2)Tests (2)what will be done with dedicated what will be done with dedicated teststests

Check materials used for implementation› for objects present in the old geometry:

translate their definition in TGeo language (done by Ludovic Gaudichet)

› for new objects only present in new geometry when possible, reuse old definition (chips, silicon, …) when not possible, a dedicated study is required to define new

materials

Radiation Length maps› comparison between “old” and “new” geometries

› comparison with computations from technical details

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Calculated material budget (as Calculated material budget (as implemented) implemented)

1.090

1.197

0.530

INNER LAYER

OUTER LAYER

TH. SHIELD

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Cables and services on the cones: Cables and services on the cones: what is therewhat is there

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Summary & outlookSummary & outlook

The new TGeo package allows a definition of a detector geometry decoupled from transport code› ease switching among different transport codes

› ease interacting with geometry also in reconstruction

Implementation of SPD has started since several months› Implemented part is almost equivalent to the actual geometry

› work started for implementation of other components on cones

Testing of new geometry on the way› Preliminary tests being done for radiation length maps and event

generation

› Test on materials is going to start

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XX00 map: comparison with old map: comparison with old geometry (very preliminary geometry (very preliminary result) with “geantinos”result) with “geantinos”

Z

(cm

)

Φ (deg)

Φ (deg)

Z

(cm

)

New

Old

Layer 2

R = 6.5 7.5 cm

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XX00 map: comparison with old map: comparison with old geometry (very preliminary geometry (very preliminary result) with “geantinos”:result) with “geantinos”:differencedifference

Z

(cm

)

Φ (deg)

Layer 2

R = 6.5 7.5 cm

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Cables and services on the cones: Cables and services on the cones: some estimatessome estimates1. Extenders:

12 per each (half-)sector: - 6 x pixel-bus

- 6 x MCM

18o

54o

90o

126o

162o

X/Xo = 6*(0.11/285.7+0.14/14.3) = 6%

X/Xo = 6*(0.10/285.7+0.10/14.3) = 4.4%

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Cables and services on the cones: Cables and services on the cones: some estimatessome estimates2. Optical patch-panels

10 in total, 1 per each (half-)sector

18o

162o

115o

90o

62o

100mm

50mm

50mm

50mm xy

yz

4mm

Aluminium

X/Xo = 4/27.0 = 14.8%

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Cables and services on the cones: Cables and services on the cones: some estimatessome estimates3. Plates holding the extenders

10 in total, 1 per each (half-)sectorat middle of the cone

50mm

5mm

xy

30mm

2mm

Carbon fiber

xz

50mm

200mm

X/Xo = 5/223.5 = 2.2%

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Cables and services on the cones: Cables and services on the cones: some estimatessome estimates4. Tubes for detector cooling

Flexible parts:

6mm

1mm

Inox

Central (rigid) part:may be assumedwith same diameterbut thinner walls (0.3mm)

X/Xo = 2/17.2 = 11.6%

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Cables and services on the cones: Cables and services on the cones: some estimatessome estimates5. Other materials

4 of these capillars on the cone

PHYNOX ducts2.6mm xternal diameter0.040mm thick wallsX/X0 = 0.080/16.1 = 0.5%

CARBON FIBER holding plate 300mm x 30mm0.3mm thickX/X0 = 0.3/223.5 = 0.1%

Cu/Ni (30/70) ducts1.85mm external diameter 0.35mm thick walls200mm lengthX/X0 = 0.7/14.3 = 4.9%

Optical fibers (quartz) 18 per halh-sector:9/125/900m buffered fibers1 fiber: X/X0 = 0.9/100 = 1.6%18 fiber pockets 4.5mm X/Xo = 4.5/100 = 4.5%