ECAL layout

The ecal surrounds the barrel of the TPC. It consists of a number of ``towers'' connected together in sections called modules. There are 60 modules in $\theta$, surrounding $2\pi$. Along the barrel they divided into two sections in $\eta$. There are 120 modules in all. There are 40 towers per module giving 4800 towers in total.

Cal. layout

The barrel is surrounded by 120 modules. 60 of these cover the east side and 60 cover the west side
Note: North points out of page, south into page

Barrel EMC front view and numbering system

• 60 Modules span all of $\phi$.
• They are numbered 1-60, clockwise, on the west face (61-120 on east face).
• Each module carries 40 towers split into two rows of 20.
• There are two sub-modules per. module are labled A and B in the picture.
• Each sub. module is numbered sub1 for the A's and sub2 for the B's.

Module layout

• The module is made of 40 towers divided into two rows of twenty
• The length of the module is half the length of the barrel.
• One set of 60 modules covers west half of the barrel and the others the east half

In this picture, the length of a west module, $\eta$ from 0 to 1, is shown. The upper section is a top down view, showing 40 towers in two rows of twenty, the lower view shows a side on projection of the module and how the tower side angle increses with increasing $\eta$ to account for the radial distribuition of the decay particles from the source.

Tower layout

• In total there are 120 modules with 2 rows of 20 towers in each, 4800 towers
• The towers are made of 20 layers of lead and 21 layers of scintillator
• Each layer is approx. one radiation length
• The first layer is read out separately as the pre-shower. This is wheremost of the MIPS, Minimum Ionising Particles, are expected to deposit their energy. Hadrons will deposit their enegy over the full length of the tower, allowing these interactions to be seperated using Tower and Preshower events.
• The towers are interlaced with two layers of SMD strips, which improve the particle tracking inside the tower

SMD Silicon Microstrip detector

After the first five layers of the towers, they spanned by silicon strips to improve particle resolution. There are two layers of strips arranged at $90^{o}$ to each other and by correlating a hit on the lower and upper strips, this will allow a postion coordinate to be found.
For a west face module, the two layers are arranged with 15 stips along the width of the module, running the length of $\eta$, 0 to 1 and with 150 strips along the length, running along the width if the modue in $\phi$.
Along the length, the 150 stips are divided into sections of 10, with 15 strips per section. The spacing of the strips in the sections along the length will then match the 15 strips spacing along the width forming square sections. The module is 2 towers wide, so 4 towers will be found in each of these square sections, with approx. 7.5 strips resolution in length and width per-tower.