Detector structure and naming conventions

   Barrel  →  Half Shell  →  Layer  →  Ladder  →  Module
↑                                 ↓
  Pixel                               ROC
  ↓                                 ↑
   Endcap → Half Cylinder → Half Disk → Blade → Panel → Module

Pixel detector

The Pixel detector consists of a central barrel and two endcaps at both ends (?<i>z</i>) of the barrel. Together, the endcaps are known as the forward Pixel or Pixel Endcap.

Figure: Diagram of the Pixel detector.

Barrel

Physically, the barrel is separated vertically (<i>y</i>-axis) to give two half-barrels. For the purpose of DAQ and DCS (but not for alignment), each half-barrel is considered to be made of two half-shells joined at <i>z</i> = 0. Therefore, the Pixel Barrel consists of four half-shells denoted as BmI, BmO, BpI, BpO, where 'p' stands for "plus" (+<i>z</i>), 'm' for "minus" (−<i>z</i>), 'I' for "Inner" (+<i>x</i>), 'O' for "Outer" (−<i>x</i>).

Figure: Schematic of Pixel Barrel showing the half-shells.

Figure: (Left) computer-aided drawing of a half-barrel in upright position. (Right) photograph of a half-barrel lying down.

Half shell

Each half-shell has 3 layers numbered as 1, 2, 3 in increasing radii. Logically, it is useful to divide each half-shell into 8 sectors in <i>φ</i>, Sector1 to Sector8, where the numbering increases from top to bottom (see figure).

Figure: r-φ view of Pixel Barrel showing the sector numbers.

Layer

Layer1 (considering a semi-circular surface) has 10 (so-called) ladders arranged symmetrically in <i>φ</i>, while Layer2 has 16 and Layer3 has 22. Due to the separation in <i>y</i>, the top and bottom ladders are actually half-ladders, but most of the time, we will simply refer to all as ladders.

Figure: r-φ view of the first layers of Pixel Barrel (2 half-shells together) showing the arrangement of the ladders.

Figure: Photograph of Layer1 of a half-barrel.

Ladder

A ladder consists of 8 modules joined end to end along the length of the barrel, four on the -z side and four on the +z side. To be precise, sometimes the letter 'F' or 'H' is used to indicate a full- or half-ladder in a label.

Module

Figure: (Left) computer-aided drawing of a 2 × 8 barrel module. (Right) photograph of a 2 × 8 barrel module.

Readout chip (ROC)

The readout chip is an array of 80 × 52 pixels, each of size 100 μm × 150 μm.

Figure: Computer-aided drawing (left) and photograph (right) of a ROC.

-- BalintRadics - 2011-03-02