B. Salvachua

Digital signal reconstruction in the ATLAS hadronic tile calorimeter

We present an optimal filtering (OF) algorithm to reconstruct the energy, time and pedestal of a photomultiplier signal from its digital samples. The OF algorithm was first developed for liquid ionization calorimeters, its implementation in scintillator calorimeters, specifically in the ATLAS hadronic tile calorimeter (TileCal), is the aim of this paper. The objective is to implement the algorithm on the DSPs of the read out driver cards in order to reconstruct online the energy of the calorimeter and provide it to the second level trigger. The algorithm is tested and compared with a plain filtering algorithm using both calibration and real data from the TileCal detector. The results are promising specially in the regions where the electronic noise contributes significantly to the resolution

Development of the Optical Multiplexer Board Prototype for Data Acquisition in the TileCal System

This paper describes the development of the optical multiplexer board (OMB), also known as PreROD board, for the TileCal readout system in the ATLAS experiment. The aim of this board is to overcome the problems that may arise in the integrity of data due to radiation effects. The solution adopted has been to add redundancy to data transmission and so two optical fibers with the same data come out from the detector front end boards. The OMB has to decide in real time which fiber, eventually, carries data with no errors switching it to the output link connected to the read out driver (ROD) motherboard where data processing takes place. Besides, the board may be also used as a data injector for testing purposes of the ROD motherboard. The paper describes the design and tests of the first prototype, implemented as a 6U VME64x slave module, including both hardware aspects, focusing on signal integrity problems, and firmware aspects, dealing with the cyclic redundancy code algorithms used to check data consistency used to make the decision

ATLAS TileCal read out driver production

The production tests of the 38 ATLAS TileCal Read Out Drivers (RODs) are presented in this paper. The hardware specifications and firmware functionality of the RODs modules, the test-bench and the test procedure to qualify the boards are described. Finally the performance results, the temperature studies and high rate tests are shown and discussed.

Digital Signal Reconstruction in the ATLAS Hadronic Tile Calorimeter

We present an Optimal Filtering (OF) algorithm to reconstruct the energy, time and pedestal of a photomultiplier signal from its digital samples. The OF algorithm was first developed for liquid ionization calorimeters, its implementation in scintillator calorimeters, specifically in the ATLAS hadronic Tile calorimeter (TileCal), is the aim of this study. The objective is to implement the algorithm on the DSPs of the Read Out Driver cards in order to reconstruct online the energy of the calorimeter and provide it to the second level trigger. The algorithm is tested and compared with a plain filtering algorithm using both calibration and real data from the TileCal detector. The results are promising specially in the regions where the electronic noise contributes significantly to the resolution

DSP Online Algorithms for the ATLAS TileCal Read-Out Drivers

TileCal is the hadronic tile calorimeter of the ATLAS experiment at LHC/CERN. The central element of the back-end system of the TileCal detector is the read-out driver (ROD).The main components of the TileCal ROD are the digital signal processors (DSPs) placed on the processing unit (PU) daughterboards. This paper presents a detailed description of the code developed for the DSPs. The code is divided into two different parts: the first part contains the core functionalities and the second part the reconstruction algorithms. The core acts as an operating system and controls configuration, data reception and transmission and synchronization between front-end data and the timing, trigger and control (TTC) information. The reconstruction algorithms implemented on the DSP are the optimal filtering (OF), muon tagging (MTag) and missing ET calculation. The OF algorithm reconstructs the deposited energy and the arrival time of the signal for every calorimeter channel within a front-end module. This reconstructed energy is used by the MTag algorithm to tag low transverse momentum muons that may escape the ATLAS muon spectrometer level 1 trigger whereas the missing ET algorithm computes the total transverse energy and the projection on X and Y axis for the entire module that will be used by the level 2 trigger system.

Algorithms for the ROD DSP of the ATLAS hadronic Tile Calorimeter

In this paper we present the performance of two algorithms currently running in the Tile Calorimeter Read-Out Driver boards for the commissioning of ATLAS. The first algorithm presented is the so called Optimal Filtering. It reconstructs the deposited energy in the Tile Calorimeter and the arrival time of the data. The second algorithm is the MTag which tags low transverse momentum muons that may escape the ATLAS muon spectrometer first level trigger. Comparisons between online (inside the Read-Out Drivers) and offline implementations are done with an agreement around 99% for the reconstruction of the amplitude using the Optimal Filtering algorithm and a coincidende of 93% between the offline and online tagged muons for the MTag algorithm. The processing time is measured for both algorithms running together with a resulting time of 59.2 μs which, although above the 10 μs of the first level trigger, it fulfills the requirements of the commissioning trigger ( ~ 1 Hz). We expect further optimizations of the algorithms which will reduce their processing time below 10 μs.

ATLAS TileCal Read-Out Driver System Production and Initial Performance Results

The ATLAS hadronic Tile Calorimeter detector (TileCal) is an iron-scintillating tiles sampling calorimeter designed to operate at the Large Hadron Collider accelerator at CERN. The central element of the back-end system of the TileCal detector is a 9U VME read-out driver (ROD) board. The operation of the TileCal calorimeter requires a total of 32 ROD boards. This paper summarizes the tests performed during the ROD production and the results obtained. Data processing is performed in the ROD by digital signal processors, whose operation is based on the use of online algorithms such as the optimal filtering algorithm for the signal amplitude, pedestal and time reconstruction and the online Muon tagging algorithm which identifies low transverse momentum muons. The initial performance of both algorithms run during commissioning is also presented in this paper.

Real time data processing of the TileCal calorimeter of the ATLAS detector

The TileCal detector is an iron-scintillating fiber sampling calorimeter of the ATLAS experiment, one of the experiments at the Large Hadron Collider (LHC) accelerator at CERN (European Laboratory for Particle Physics), scheduled to start in 2007. At a Level 1 trigger rate of 100 kHz, the read out system of the TileCal has to be able to process and format the data of 10,000 read-out channels (112.91 Gbps of input bandwidth) in 2 mus to avoid dead time. Furthermore, to reduce the amount of data and to meet the maximum output bandwidth of the Level 2 Trigger of 53.7 Gbps, real time computation of the deposited energy applying optimal filtering techniques and collision time computation must be performed for each channel. This is accomplished with a read out driver system of which 32 9U VME boards are the main components. Each board consists of 8 G-links receivers and 4 S-Link transmitters, and 8 digital signal processors (Texas Instruments TMS320C6414@600 MHz DSP), totalizing 68992 MIPS of processing power. These boards are presently at the production stage. We report on the overall design of such system, using the DSP for energy and collision time computation, data formatting, and identification of low transverse momentum muons in real time with high efficiency

Signal integrity studies at optical multiplexer board for tilecal system

The Optical Multiplexer Board is a card included in the TileCal Data Acquisition System; it is designed to receive two optical fibers with same data from front-end boards and decided which has correct data. Inside this card we have different transmission lines that need to be studied; signal integrity problems such as signal delay, reflection, distortion and coupling should be analyzed. This paper presents the results of the signal integrity studies at the Optical Multiplexer Board for TileCal System.

Development of the optical multiplexer board prototype for data acquisition in TileCal experiment

The optical multiplexer board is one of the elements present in the read out chain of the tile calorimeter in ATLAS experiment. Due to radiation effects, two optical fibers with the same data come out from the front end boards to this board, which has to decide in real time which one carries good data and pass them to the read out driver motherboard for processing. This paper describes the design and tests of the first prototype, implemented as a 6U VME64x slave module, including both hardware and firmware aspects. In this last, algorithms for cyclic redundancy code checking are used to make the decision. Besides, the board may be used as a data injector for testing purposes of the read out driver motherboard