Detector Development - Liquid Argon Calorimeter


For liquid argon calorimeters as for other detectors, the Read-Out Driver (ROD) is the central element of back-end electronics. In this field, the University of Geneva has contributed and still contributes to the following activities:

Development of the Read-Out Driver

The Read-Out Driver obbeys the 9U VME64x protocol. As can be seen, it is composed of a motherboard and 4 mezzanine boards. The Printed Circuit Board (PCB) of the motherboard has been designed by the DPNC group, while mezzanines have been developed by LAPP and Nevis groups. Almost one year has been necessary to produce the 192 ROD modules of the liquid argon calorimeter. A brief explanation of how a ROD module works is given in the following. On the picture, data travel from left to right:

Validation and repair of ROD boards

Test bench Before being installed in the ATLAS cavern dedicated to back-end electronics, each ROD module has been validated with a test bench.

The setup shown on the right reproduces a part of the data acquisition chain. Front end boards are replaced with an injector module which emulates data. As the injector only has 5 output channels, an optical splitter is used to feed the 8 input channels of the ROD board. Level 1 Accepts (L1A) and TTC signals are produced by the injector as well.

A test consists in a series of write/read cycles, and allows to verify the behavior of every component of the ROD board at each step of data processing. Tests are performed in the same software environment as for real data taking.

The validation of ROD modules came to completion by the end of 2005. The test bench is now used to indentify problems in faulty boards.

Maintenance of ROD racks

The Geneva group is in charge of ROD racks operation. A rack is composed of two or three crates, each of which containing:

View of ROD racks

Below is displayed a diagram of the water-cooling station, and a view of the water tank. A vacuum pump is connected to the hydraulic system such that the water pressure remains below the atmospheric pressure all along the circuit. Thus, water does not leak on boards in case of problem. The cooling drawers are connected in parallel between the outlet and return manifolds. The University of Geneva has played a leading role in the design of these drawers, which have to resist to mechanical stress and corrosion.

Control panel of the water cooling ciruit Main elements of the cooling ciruit

Last modified: 2009/05/05