The TOF detector covers a cylindrical surface (at 3.7 m from the beam
line) of polar acceptance
[45,135] degrees and a full coverage in phi angle using MRPC
strips. The area of the detector is ~150 square
The system has a modular structure corresponding to 18
sectors in phi and five modules along the beam direction (with a
total of 90 modules and 1638 MRPC strips).
active area of each strip is 121.5*7.4 square centimeters.
Taking into account that each strip contains 96 pickup pads, it results a total number of read-out channels (pads) equal to 157248.
The general design has been conceived taking into account the results of the simulations, the feasibility of the proposed solution, the performances of the detector and the need to keep the dead area inside the module to a minimum.
- In particular, it is important to minimise the transversal path of the particles through the strip that can create a sharing effect of the signal among adjacent pickup pads, thereby increasing the occupancy and the time jitter of the detected signals. To overcome this effect, a special positioning of the strips has been envisaged: their angle with respect to the axis of the cylinder is progressively increased from 0 degrees in the central part (theta=90 degrees) of the detector to 45 degrees in the extreme part of the external module (theta=45 degrees).
- To avoid dead areas, adjacent strips inside one module have been
overlapped by 2 mm and adjacent modules have specially shaped boundaries
(see the following figure for the intermediate module).