OT Geometry
Module Position
The basic OT geometrical structure and naming conventions
are discussed in the
introduction
(following the LHCb note
LHCb-2003-041).
Here it is described the positioning of the straw-tube modules on the
C-Frames.
By construction,
the straw tube modules are built out of two "mono-layers"
of straws, conventionally called "A" and "B".
These two types of panels are identical, except in the details of the
straw length, as schematically shown in the
figure below
(details in the
Engineering Drawings).
In the detector construction and installation, straw mono-layers become
detector elements through the following steps:
-
two mono-layers were joined to form one
straw-tube module
-
in the case of the
S Modules,
"Upper" and "Lower" modules were attached to each other by means
of a carbon-fiber junction.
By design, this was done such that side "A" and "B" of the upper and
lower side would match; however, by mistake for a few modules
this is not the case
-
attach the gas pipes to each straw tube module.
In this step, it was decided that all modules would be installed with
side A attached to the C-Frames; however, by mistake for a few S modules
this is not the case
-
install all straw-tube modules in the C-Frames
Due to this combination of construction and installation features,
the straw-tube modules present a few "asymmetries".
The first one is due to the staggering of the two mono-layer
by half straw pitch in X (e.g. the schematic top view
in the
figure below).
The second one is specific to the
F Modules,
and it is due to the the various straw lengths, that results
in a "staggering" in Y of the "dead" region
(e.g. see the schematic side view in the
figure below).
The details of the position and geometry of each straw-tube module are given
in the
Module Location Page
(and in the
Module Location Database).