AliPMDv1.cxx

AliPMDv1.h
 

The basic unit of the PMD detector is a hexagonal cell filled with Argon and carbon dioxide gas as the sensitive medium. The specifications of this cell as implemented in GEANT can be seen here

Heaxgonal cell of PMD
 

These cells are then arranged in a strip. There are two kinds of strip, one with 48 cells and the other with 96 cells.

Figure of a strip of hexagonal cells as implemented in GEANT

Figure of a strip of hexagonal cells as implemented in GEANT

These strips are then placed 96 and 48 times to form an array of hexagonal cells. So our PMD has two kinds of modules. The total number of cells in each module is 48X96 or 96X48 = 4608

Figure of an array of honeycomb/hexagonal cells forming a module Type A

Figure of an array of honeycomb/hexagonal cells forming a module Type B
 
 

One module of preshower plane or veto plane has many components (top PCB, bottom PCB, G10, back plane, base plate, stainless steel boundary channel), the tree structure of these components as implemented in GEANT is given in these figures :

Figure shows the tree structure of a module a preshower module Type A

Figure shows the tree structure of a module a preshower module Type B
 
 

Figure shows the tree structure of a module a veto module Type A

Figure shows the tree structure of a module a veto module Type B
 
 

One can have a better understanding of the placement of the various components in a modules by looking along the Z-axis with X-Y plane rotated by 90 degrees (theta = 90), these can be seen in the following figures  (note the position of back plane and base plate are opposite in preshower and veto modules):

Figure shows the placement of various componenets of a preshower module A

Figure shows the placement of various componenets of a veto module A
 

Now we place 6 such modules of a given type to form a quadrant of the detector, this layout can be seen in the following figures :

Figure for preshower Type A housing 6 modules

Figure for preshower Type B housing 6 modules
 

Each quadrant of PMD has many components (preshower plane, lead plates, steel support and veto plane). The tree structure of this quadrant can be seen in the following figures :

Figure of tree structure of a quadrant of PMD housing Type A modules

Figure of tree structure of a quadrant of PMD housing Type B modules

The complete layout of the PMD as viewd from the interaction point and as implemented in GEANT can be seen in the following figure :

Figure of the PMD layout from IP
 

It is very neccessary to make sure the preshower, veto, lead plate and steel support is properly placed in Z. This can be viewd by looking along the Z-dirrection with XY plane rotated by 90 deg (theta = 90)
 

Figure of PMD along Z direction with theta = 90 degree
 

It is important to know the first cell of the veto and preshower planes.
This has to be consistent with hardware also. This is shown for the veto plane in the figure below :

Figure of PMD layout (veto plane) showing the first 2 cells in each module
 

The arrangement of 1st strip of cells in various modules are
shown below :

Type-A Preshower module 1 strip of cells

Type-A Veto 1st strip of cels

Type-B 1st strip of cells

Type-B Veto 1st strip of cells

For the preshower plane the first cell is identically placed as in veto plane (mirror reflection). The figure below shows the first cell of preshower plane after we rotate by theta of 180 degrees :

Figure shows the PMD layout rotated around Z-axis by 
theta = 180 deg, so that rotated preshower plane is visible
 
 

Some more details on FIRST cell arrangements

For TYPE A

For TYPE B
 

ELECTRONICS IMPLEMENTATION IN PMD GEANT :

The FEE boards of 70mm X 24 mm X 1mm (X,Y,Z) is implemented in PMD GEANT.
TYPE A has 12 FEE boards in a row and there is 6 rows of  12  such boards. 
TYPE B has 24 FEE boards in a row and there is 3 rows of 24 such boards.

TYPE A module with FEE boards
TYPE B module with FEE boards
 

To see how the FEE boards are arranged in a system of 6 modules look at
the following figure

TYPE A SM with FEE boards
TYPE B SM with FEE boards
FEE Boards on PMD

To see how the arrangement looks when we rotate it 

  Roated view of FEE boards on PMD plane
 

We also tried to confirm that veto plane is facing the beam
For this be put only the FEE boards in VETO plane and plotted 
the following figure with TPC and beam pipe

Confirm that veto faces IP

To see the effect of implementation of FEE boards on upsream Material look at the figure below

Amount of material seen by PMD only (It has 3 X0 convertor) with FEE boards addition.