ALICE Offline week, CERN 21 February 2005 I. Hrivnacova 1 New geometry framework in MUON...

ALICE Offline week, CERN21 February 2005

I. Hrivnacova 1

New geometry framework in MUON

I.HrivnacovaIPN, Orsay

ALICE Offline week, CERN

21 February 2005


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Motivation

Parametrisation of geometry– Extraction of the positions of selected pieces in a detector

geometry - “detection elements”

– Make possible to use them as input parameters and so to take into account the alignment

Presentation at the last Offline week in September 2004– Concentrated on the applied method

This presentation– Will give a more detailed description of the introduced

framework classes and their implementation for MUON

– Will cover the development since that time


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Logical Geometry Structure

We have defined logical geometry units that represent sets of volumes in the geometry

Three level structure:– Module - the biggest unit in a detector

– Envelope - non-virtual and virtual

– Envelope constituent – constituent of a virtual envelope Each unit represents a frame with respect to which its

components are placed


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Detection Element

In a logical geometry hierarchy it corresponds to an envelope

Detection element != a single volume in a MC geometry In real detector:

Quadrant, slat, trigger chamber

Has an ID unique in the whole detector Provides transformation between the global and its local

frames Object of alignment


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Structural Objects

Classes The elements defined before are represented in the

framework via correspondent classes:– Alice coding convention + need to make this group of classes retrievable

among ~ 90 other MUON classes has resulted in long class names: AliMUON*Geometry*XYZ

– To make presentation clear, AliMUONGeometry prefix will be skipped ...

– The V prefix stands for abstract classes

– Module, Envelope, EnvelopeConstituent, DetElement• Structural objects

– EnvelopeStore, GeometryStore, VDEIndexing• Utility objects

Transformation representation:– TGeoMatrix class from Root


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Structural objects

Classes (2)


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Structural objects

Classes (3)


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Building Geometry

User CreateGeometry function now have to define also the logical geometry elements

The framework builder classes help to simplify this:– User implements his detector construction class as a

geometry builder derived from VBuilder associated with one or more Module object

– The VBuilder base class provides utility functions for definition of Envelopes, EnvelopesConstituents and DetElements

– Concrete examples of a user code were shown in the presentation at the previous offline meeting

The main Builder than takes care of geometry construction via all user defined registered builders


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Behavioral Objects

Classes


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Procedure of Building Geometry

1. Definition of the logical structures (modules, envelopes, envelope constituents) and all volumes trees placed inside them

By UserBuilder : VBuilder objects

2. Placing the envelopes and their constituents with a composed transformation

Automatic procedure – using the data stored in modules and envelopes, by main Builder object

3. Definition of detection elements and storing their global transformations

By main Builder object


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Geometry ParametrisationI/O

Transformations defined in the logical volume structure can be exported to/imported from files

Option whether these data will be taken from the files or from geometry definition in building geometry

Defined in main Builder: SetAlign(), GetAlign() functions One file per user builder

Includes data for several geometry modules Reading/writing files implemented in VBuilder

ASCII files – temporary solution until such a functionality is provided via AliRoot framework


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Geometry Parametrisation I/0

trasform_st1V2.datData format:CH moduleId nofDEs pos: x y z rot: thex, phix, they, phiy, thez, phizDE deId envName copyNo pos: x y z rot: thex, phix, they, phiy, thez, phiz

Example of station1 V2 data:CH 1 4 pos: 0. 0. 533.5 rot: 90. 0. 90. 90. 0. 0.

CH 2 4 pos: 0. 0. 533.5 rot: 90. 0. 90. 90. 0. 0.

DE 100 SQM1 1 pos: -2.6 -2.6 3.25 rot: 90. 0. 90. 90. 0. 0.

DE 151 SQM1 2 pos: 2.6 -2.6 -3.25 rot: 90. 180. 90. 90. 180. 0. DE 150 SQM1 3 pos: 2.6 2.6 3.25 rot: 90. 180. 90. 270. 0. 0. DE 101 SQM1 4 pos: -2.6 2.6 -3.25 rot: 90. 0. 90. 270. 180. 0.

DE 200 SQM2 1 pos: -2.6 -2.6 3.25 rot: 90. 0. 90. 90. 0. 0. DE 251 SQM2 2 pos: 2.6 -2.6 -3.25 rot: 90. 180. 90. 90. 180. 0. DE 250 SQM2 3 pos: 2.6 2.6 3.25 rot: 90. 180. 90. 270. 0. 0. DE 201 SQM2 4 pos: -2.6 2.6 -3.25 rot: 90. 0. 90. 270. 180. 0.


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Geometry Segmentation

Segmentation defines the detector layout, topology of pads, which is not present in the geometry definition

In the current framework– User defined segmentations implement geometry functions

(“get pad position”) in the global reference frame

– Disconnected from geometry definition

In the new framework– User defined segmentations, derived from VDESegmentation

base class, implement geometry functions in the local detection element frame

– One general “global” segmentation per module, GeometrySegmentation, implement geometry functions in a global reference frame


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Geometry Segmentation

ImplementationBool_t AliMUONGeometrySegmentation::GetPadC( Int_t detElemId, Int_t ix, Int_t iy, Float_t& xg, Float_t& yg, Float_t& zg){// Transform from pad to real coordinates

if (!Notify(detElemId)) return false;

if (!fCurrentSegmentation->HasPad(ix, iy)) return false;

Float_t xl, yl, zl; fCurrentSegmentation->GetPadC(ix, iy, xl , yl, zl);

fGeometryModule->Local2Global(detElemId, xl, yl, zl, xg, yg, zg); return true;}


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Segmentation

Classes


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Use of Geometry Segmentation

Geometry segmentation has different API from the old segmentation

– Requires code transition from the old segmentation framework to the new one

Detection element ID has to be consistently used together with the new geometry segmentation

– Added to hit, digit, ... class definitions


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Present Status (1)

Framework classes: In a separate library libMUONgeometry Independent from MUON code

MUON specific classes that implement geometry are not included in this library

Geometry: The whole MUON geometry (v1) is now defined via new

framework

– Still some problems to be solved• Too many volumes going to ALIC from some builders (misuse of

virtual envelopes)

• Overlaps for newly placed volumes


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Present Status (2)

Segmentation New segmentations per detection elements:

• Station12, Slat stations, Trigger stations

• All in CVS

– AliMUONTest• Testing new segmentation framework (in CVS)

• Instantiation of new geometry segmentations, printing pads positions, drawing pads

AliMUONFactory, AliMUONChamber, ... In transition to the new geometry and segmentation framework In development


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Conclusions

Concept of detection elements Consistent use of the same set of geometry

transformations in both simulation and reconstruction Possibility to read transformations from a data file Concept of geometry modules – geometry builder classes

per development teams Framework classes fully independent from MUON specific

classes

ALICE Offline week, CERN 21 February 2005 I. Hrivnacova 1 New geometry framework in MUON...

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