[u/mrichter/AliRoot.git] / ITS / doc / doc_itsgeo.html

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<p style="margin-top: 0.42cm; margin-bottom: 0.5cm; page-break-after: avoid;">
<font face="Albany, sans-serif"><font size="4">============================================================================</font></font></p>
<p style="margin-top: 0.42cm; margin-bottom: 0.5cm; page-break-after: avoid;">
<font face="Albany, sans-serif"><font size="4">Description of ALICE ITS
Geometry Code   (Rev. 1,00 -  April, 30<sup>th</sup>
2008 -  M. Sitta)</font></font></p>
<p style="margin-top: 0.42cm; margin-bottom: 0.5cm; page-break-after: avoid;">
<font face="Albany, sans-serif"><font size="4">============================================================================</font></font></p>
<p style="margin-bottom: 0cm;"><a name="Content"></a><strong><font style="font-size: 16pt;" size="4">Content</font></strong>
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<ol>
	<li><p style="margin-bottom: 0cm;"><a href="#punto%201">General
	description</a></p>
	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%202">
	Detector-specific classes</a></p>
	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%203">Initialization
	</a></p>
	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%204">Main
	methods</a></p>
	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%205">Helper
	classes AliITSgeom and AliITSgeomTGeo</a></p>
</li></ol>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p><a name="punto 1"></a><strong><a href="#Content" name="punto 1">General
description</a></strong></p>
<p style="margin-bottom: 0cm;">The <font face="Courier 10 Pitch">
AliITSv11Hybrid</font> class describes the overall ITS geometry. It is a
mix between the old geometry (originally coded in the
<font face="Courier 10 Pitch">AliITSvPPRasymmFMD</font> class) and the new
TGeo geometry (v11). The "old" part is described using Geant3 volumes, while
the "new" one using TGeo volumes; moreover the new part is more adherent to
the technical drawings and so is more realistic.
</p>
<p style="margin-bottom: 0cm;">Proper flags, set in the
<font face="Courier 10 Pitch">AliITSInitGeometry</font> class, determine
whether the old or the new part is used.
</p>
<p style="margin-bottom: 0cm;">Currently all the sensitive detectors and their
supports, the mechanical supports and part of the services (namely the SDD
cables) are described in the new geometry. The rest of the services and some
other mechanics are (sometimes partly) described in the old geometry. Work is
in progress to move everything in the new geometry.
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">================================================================================</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p><a name="punto 2"></a><strong><a href="#Content" name="punto 2">
Detector-specific classes</a></strong></p>
<p style="margin-bottom: 0cm;">The old geometry is fully described in the
<font face="Courier 10 Pitch">AliITSv11Hybrid</font> class. For the new
geometry on the other hand, a set of specific classes are defined
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">-&gt; <font face="Courier 10 Pitch">
AliITSv11GeometrySPD</font> describes the whole SPD geometry
</p>
<p style="margin-bottom: 0cm;">-&gt; <font face="Courier 10 Pitch">
AliITSv11GeometrySDD</font> describes the whole SDD geometry
</p>
<p style="margin-bottom: 0cm;">-&gt; <font face="Courier 10 Pitch">
AliITSv11GeometrySSD</font> describes the whole SSD geometry
</p>
<p style="margin-bottom: 0cm;">-&gt; <font face="Courier 10 Pitch">
AliITSv11GeometrySupport</font> describes the geometry of some mechanical
supports (thermal shields and support cylinders and cones)
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">================================================================================</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p><a name="punto 3"></a><strong><a href="#Content" name="punto 3">
Initialization</a></strong></p>
<p style="margin-bottom: 0cm;">To initialize an object of the
<font face="Courier 10 Pitch">AliITSv11Hybrid</font> class it is enough to
call its constructor in the <font face="Courier 10 Pitch">Config.C</font>
macro
</p>
<p style="margin-bottom: 0cm;"><font face="Courier 10 Pitch">
AliITSv11Hybrid *ITS  = new AliITSv11Hybrid("ITS","ITS detailed version with TGeo description");</font>
</p>
<p style="margin-bottom: 0cm;">the first string is the detector name (which
is actually ignored, and internally set to "ITS"), the second string is an
arbitrary title. Both strings are passed to the <font face="Courier 10 Pitch">
AliITS</font> constructor.
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">The class constructor initializes its private
members, creates an object for each detector-specific class and sets their
names, and sets the defaults for some detector parameters.
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">================================================================================</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p><a name="punto 4"></a><strong><a href="#Content" name="punto 4">Main
Methods</a></strong></p>
<p style="margin-bottom: 0cm;">The main methods of the
<font face="Courier 10 Pitch">AliITSv11Hybrid</font> class are
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<ul>
<li><font face="Courier 10 Pitch">AliITSv11Hybrid::CreateGeometry</font> first
calls <font face="Courier 10 Pitch">CreateOldGeometry</font> to define the
old (Geant3) volumes (the ones still active according to the aforementioned
flags); then it calls specific methods of the detector classes to create
the new geometry</li>
<li><font face="Courier 10 Pitch">AliITSv11Hybrid::CreateOldGeometry</font>
creates the old geometry volumes; flags are used to determine which sections
are to be skipped because already coded in the detector-specific classes</li>
<li><font face="Courier 10 Pitch">AliITSv11Hybrid::CreateMaterials</font>
defines all materials and mediums used in the ITS geometry description</li>
<li><font face="Courier 10 Pitch">AliITSv11Hybrid::AddAlignableVolumes</font>
creates entries for alignable volumes associating the symbolic volume name
with the corresponding volume path</li>
<li><font face="Courier 10 Pitch">AliITSv11Hybrid::StepManager</font> is
called at every step in the ITS to save hits according to the subdetector
which the particle is in</li>
</ul>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">================================================================================</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p><a name="punto 5"></a><strong><a href="#Content" name="punto 5">Helper
classes AliITSgeom and AliITSgeomTGeo</a></strong></p>
<p style="margin-bottom: 0cm;"><font face="Courier 10 Pitch">AliITSgeomTGeo
</font> is a simple interface class to TGeoManager. It is used in the
simulation and reconstruction in order to query the TGeo ITS geometry.
</p>
<p style="margin-bottom: 0cm;">It has methods such as for example<br>
<font face="Courier 10 Pitch">GetModuleIndex</font> to compute the module
index number from the layer, ladder, and detector numbers<br>
<font face="Courier 10 Pitch">GetModuleId</font> to compute the layer,
ladder and detector number given the module index number<br>
<font face="Courier 10 Pitch">GetLayer</font> to compute the layer number
for a given the module index<br>
<font face="Courier 10 Pitch">GetMatrix</font> to get the
transformation matrix for a given module by quering the TGeoManager<br>
<font face="Courier 10 Pitch">GetTranslation</font> and
<font face="Courier 10 Pitch">GetRotation</font> to get the translation
vector or the rotation matrix for a given module by quering the
TGeoManager<br>
<font face="Courier 10 Pitch">LocalToGlobal</font> and
<font face="Courier 10 Pitch">GlobalToLocal</font> to make the conversion
from the local sensitive reference system to the global reference system
and vice-versa, for an arbitrary local or global position
</p>
<p style="margin-bottom: 0cm;"><br>
</p>
<p style="margin-bottom: 0cm;">Similarly the <font face="Courier 10 Pitch">
AliITSgeom</font> class contains other methods for querying and
interfacing the ITS geometry.
</p>
<p style="margin-bottom: 0cm;"><br>
</p>

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Commit	Line	Data
a65a7e70	1	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
	2	<html><head>
	3	<meta http-equiv="CONTENT-TYPE" content="text/html; charset=utf-8"><title></title>
	4
	5	<meta name="GENERATOR" content="OpenOffice.org 1.1.5 (Linux)">
	6	<meta name="CREATED" content="20080430;10144900">
	7	<meta name="CHANGED" content="20080430;11283000">
	8	<style>
	9	<!--
	10	@page { size: 21.59cm 27.94cm; margin: 2.01cm }
	11	P { margin-bottom: 0.2cm }
	12	-->
	13	</style></head>
	14
	15	<body dir="ltr" lang="en-US">
	16	<p style="margin-top: 0.42cm; margin-bottom: 0.5cm; page-break-after: avoid;">
	17	<font face="Albany, sans-serif"><font size="4">============================================================================</font></font></p>
	18	<p style="margin-top: 0.42cm; margin-bottom: 0.5cm; page-break-after: avoid;">
	19	<font face="Albany, sans-serif"><font size="4">Description of ALICE ITS
	20	Geometry Code (Rev. 1,00 - April, 30<sup>th</sup>
	21	2008 - M. Sitta)</font></font></p>
	22	<p style="margin-top: 0.42cm; margin-bottom: 0.5cm; page-break-after: avoid;">
	23	<font face="Albany, sans-serif"><font size="4">============================================================================</font></font></p>
	24	<p style="margin-bottom: 0cm;"><a name="Content"></a><strong><font style="font-size: 16pt;" size="4">Content</font></strong>
	25	</p>
	26	<p style="margin-bottom: 0cm;"><br>
	27	</p>
	28	<ol>
	29	<li><p style="margin-bottom: 0cm;"><a href="#punto%201">General
	30	description</a></p>
	31	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%202">
	32	Detector-specific classes</a></p>
	33	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%203">Initialization
	34	</a></p>
	35	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%204">Main
	36	methods</a></p>
	37	</li><li><p style="margin-bottom: 0cm;"><a href="#punto%205">Helper
	38	classes AliITSgeom and AliITSgeomTGeo</a></p>
	39	</li></ol>
	40	<p style="margin-bottom: 0cm;"><br>
	41	</p>
	42	<p style="margin-bottom: 0cm;"><br>
	43	</p>
	44	<p><a name="punto 1"></a><strong><a href="#Content" name="punto 1">General
	45	description</a></strong></p>
	46	<p style="margin-bottom: 0cm;">The <font face="Courier 10 Pitch">
	47	AliITSv11Hybrid</font> class describes the overall ITS geometry. It is a
	48	mix between the old geometry (originally coded in the
	49	<font face="Courier 10 Pitch">AliITSvPPRasymmFMD</font> class) and the new
	50	TGeo geometry (v11). The "old" part is described using Geant3 volumes, while
	51	the "new" one using TGeo volumes; moreover the new part is more adherent to
	52	the technical drawings and so is more realistic.
	53	</p>
	54	<p style="margin-bottom: 0cm;">Proper flags, set in the
	55	<font face="Courier 10 Pitch">AliITSInitGeometry</font> class, determine
	56	whether the old or the new part is used.
	57	</p>
	58	<p style="margin-bottom: 0cm;">Currently all the sensitive detectors and their
	59	supports, the mechanical supports and part of the services (namely the SDD
	60	cables) are described in the new geometry. The rest of the services and some
	61	other mechanics are (sometimes partly) described in the old geometry. Work is
	62	in progress to move everything in the new geometry.
	63	</p>
	64	<p style="margin-bottom: 0cm;"><br>
65	</p>
66	<p style="margin-bottom: 0cm;">================================================================================</p>
67	<p style="margin-bottom: 0cm;"><br>
68	</p>
69	<p><a name="punto 2"></a><strong><a href="#Content" name="punto 2">
70	Detector-specific classes</a></strong></p>
71	<p style="margin-bottom: 0cm;">The old geometry is fully described in the
72	<font face="Courier 10 Pitch">AliITSv11Hybrid</font> class. For the new
73	geometry on the other hand, a set of specific classes are defined
74	</p>
75	<p style="margin-bottom: 0cm;"><br>
76	</p>
77	<p style="margin-bottom: 0cm;">-> <font face="Courier 10 Pitch">
78	AliITSv11GeometrySPD</font> describes the whole SPD geometry
79	</p>
80	<p style="margin-bottom: 0cm;">-> <font face="Courier 10 Pitch">
81	AliITSv11GeometrySDD</font> describes the whole SDD geometry
82	</p>
83	<p style="margin-bottom: 0cm;">-> <font face="Courier 10 Pitch">
84	AliITSv11GeometrySSD</font> describes the whole SSD geometry
85	</p>
86	<p style="margin-bottom: 0cm;">-> <font face="Courier 10 Pitch">
87	AliITSv11GeometrySupport</font> describes the geometry of some mechanical
88	supports (thermal shields and support cylinders and cones)
89	</p>
90	<p style="margin-bottom: 0cm;"><br>
91	</p>
92	<p style="margin-bottom: 0cm;">================================================================================</p>
93	<p style="margin-bottom: 0cm;"><br>
94	</p>
95	<p><a name="punto 3"></a><strong><a href="#Content" name="punto 3">
96	Initialization</a></strong></p>
97	<p style="margin-bottom: 0cm;">To initialize an object of the
98	<font face="Courier 10 Pitch">AliITSv11Hybrid</font> class it is enough to
99	call its constructor in the <font face="Courier 10 Pitch">Config.C</font>
100	macro
101	</p>
102	<p style="margin-bottom: 0cm;"><font face="Courier 10 Pitch">
103	AliITSv11Hybrid *ITS = new AliITSv11Hybrid("ITS","ITS detailed version with TGeo description");</font>
104	</p>
105	<p style="margin-bottom: 0cm;">the first string is the detector name (which
106	is actually ignored, and internally set to "ITS"), the second string is an
107	arbitrary title. Both strings are passed to the <font face="Courier 10 Pitch">
108	AliITS</font> constructor.
109	</p>
110	<p style="margin-bottom: 0cm;"><br>
111	</p>
112	<p style="margin-bottom: 0cm;">The class constructor initializes its private
113	members, creates an object for each detector-specific class and sets their
114	names, and sets the defaults for some detector parameters.
115	</p>
116	<p style="margin-bottom: 0cm;"><br>
117	</p>
118	<p style="margin-bottom: 0cm;">================================================================================</p>
119	<p style="margin-bottom: 0cm;"><br>
120	</p>
121	<p><a name="punto 4"></a><strong><a href="#Content" name="punto 4">Main
122	Methods</a></strong></p>
123	<p style="margin-bottom: 0cm;">The main methods of the
124	<font face="Courier 10 Pitch">AliITSv11Hybrid</font> class are
125	</p>
126	<p style="margin-bottom: 0cm;"><br>
127	</p>
128	<ul>
129	<li><font face="Courier 10 Pitch">AliITSv11Hybrid::CreateGeometry</font> first
130	calls <font face="Courier 10 Pitch">CreateOldGeometry</font> to define the
131	old (Geant3) volumes (the ones still active according to the aforementioned
132	flags); then it calls specific methods of the detector classes to create
133	the new geometry</li>
134	<li><font face="Courier 10 Pitch">AliITSv11Hybrid::CreateOldGeometry</font>
135	creates the old geometry volumes; flags are used to determine which sections
136	are to be skipped because already coded in the detector-specific classes</li>
137	<li><font face="Courier 10 Pitch">AliITSv11Hybrid::CreateMaterials</font>
138	defines all materials and mediums used in the ITS geometry description</li>
139	<li><font face="Courier 10 Pitch">AliITSv11Hybrid::AddAlignableVolumes</font>
140	creates entries for alignable volumes associating the symbolic volume name
141	with the corresponding volume path</li>
142	<li><font face="Courier 10 Pitch">AliITSv11Hybrid::StepManager</font> is
143	called at every step in the ITS to save hits according to the subdetector
144	which the particle is in</li>
145	</ul>
146	<p style="margin-bottom: 0cm;"><br>
147	</p>
148	<p style="margin-bottom: 0cm;">================================================================================</p>
149	<p style="margin-bottom: 0cm;"><br>
150	</p>
151	<p><a name="punto 5"></a><strong><a href="#Content" name="punto 5">Helper
152	classes AliITSgeom and AliITSgeomTGeo</a></strong></p>
153	<p style="margin-bottom: 0cm;"><font face="Courier 10 Pitch">AliITSgeomTGeo
154	</font> is a simple interface class to TGeoManager. It is used in the
155	simulation and reconstruction in order to query the TGeo ITS geometry.
156	</p>
157	<p style="margin-bottom: 0cm;">It has methods such as for example<br>
158	<font face="Courier 10 Pitch">GetModuleIndex</font> to compute the module
159	index number from the layer, ladder, and detector numbers<br>
160	<font face="Courier 10 Pitch">GetModuleId</font> to compute the layer,
161	ladder and detector number given the module index number<br>
162	<font face="Courier 10 Pitch">GetLayer</font> to compute the layer number
163	for a given the module index<br>
164	<font face="Courier 10 Pitch">GetMatrix</font> to get the
165	transformation matrix for a given module by quering the TGeoManager<br>
166	<font face="Courier 10 Pitch">GetTranslation</font> and
167	<font face="Courier 10 Pitch">GetRotation</font> to get the translation
168	vector or the rotation matrix for a given module by quering the
169	TGeoManager<br>
170	<font face="Courier 10 Pitch">LocalToGlobal</font> and
171	<font face="Courier 10 Pitch">GlobalToLocal</font> to make the conversion
172	from the local sensitive reference system to the global reference system
173	and vice-versa, for an arbitrary local or global position
174	</p>
175	<p style="margin-bottom: 0cm;"><br>
176	</p>
177	<p style="margin-bottom: 0cm;">Similarly the <font face="Courier 10 Pitch">
178	AliITSgeom</font> class contains other methods for querying and
179	interfacing the ITS geometry.
180	</p>
181	<p style="margin-bottom: 0cm;"><br>
182	</p>
183
184	</body></html>