112985462
Electromagnetic Compatibility of a Low Voltage Power Supply for the ATLAS Tile Calorimeter Front-End Electronics
The front-end electronics of the ATLAS Tile Calorimeter is powered by DC/DC converters that sit close to it. The performance of the detector electronics is constrained by the conducted noise emissions of its power supply. A compatibility limit is defined for the system. The noise susceptibility of the front-end electronics is evaluated, and different solutions to reduce the front-end electronics noise are discussed and tested. I. POWER DISTRIBUTION SCHEME FOR THE TILE CALORIMETER The front-end electronics of the Tile Calorimeter [1] is organized in drawers that are inserted in detector modules. Each drawer is 3 meter long and contains the front-end analogue and digitizing electronics for 45 photomultiplier tubes [2] in the case of the barrel modules. It is powered by eight regulated low voltage lines, and it is rated to consume a maximum power of 300W. Because a drawer requires a tight voltage regulation on its power lines, the low voltage power supply was designed to fit in its vicinity, as an extension of it. The environmental constrains such as radiation and magnetic field tolerance were solved with the design of custom DC/DC converters that are remotely controlled by an ELMB [3]. The power supply is located in a closed volume known as finger. The power supply is water cooled. Figure 1: Finger low voltage power supply of the ATLAS Tile Calorimeter. The finger low voltage power supplies (figure 1) are fed by bulk power supplies (200VDC) located in a control room. Auxiliary power supplies in the same control room are also required to power separately the monitoring and control circuitry. The power system (figure 2) is controlled by the Detector Control System (DCS) through a CANBus line that communicates with the ELMB of the power supply. The low voltage outputs are isolated from earth, but all the return lines are put in common inside the drawer. Figure 2: Tile Calorimeter power distribution scheme. NOISE PERFORMANCE TEST METHODS The front-end noise is composed by the drawer electronics noise, by the power supply noise and by the external couplings on the interconnecting cables (not studied here). A. System Noise. The achievable performance of the drawer electronics in terms of noise is limited by design. The system noise in each front-end channel was measured in detail on drawers that were powered with low noise linear power supplies. The system noise is evaluated in terms of high frequency and low frequency contributions from the data taken with the full data acquisition chain. The high frequency noise seen by the fast readout electronics is estimated from the pedestals data. The estimation is based on a selection of parameters computed over several runs and on all the channels of a drawer: • RMS of the pedestals distribution. • Gaussian property of the pedestals distribution. Module DRAWER LVPS Finger 200VDC
120473193
Trigger of low pT muons with the ATLAS hadronic calorimeter
Abstract A strategy for tagging muons with the Tile Calorimeter at the second level trigger (LVL2) of the ATLAS experiment is presented and its efficiency and mistagging fraction are discussed. It is demonstrated that the Tile Calorimeter can identify muons with good efficiency down to p T =2 GeV /c where the stand-alone muon spectrometer has zero efficiency. A method of exploiting all information available at LVL2 to reduce spurious muon-tag and measure the candidate muon momentum is discussed. The effectiveness of this method is tested, in particular, in the case of b b events at low Large Hadron Collider luminosity (10 33 cm −1 s −2 ) with full simulation of experimental conditions.
15020199
A device to characterize optical fibres
Abstract ATLAS is a general purpose experiment approved for the LHC collider at CERN. An important component of the detector is the central hadronic calorimeter; for its construction more than 600,000 Wave Length Shifting fibres (corresponding to a total length of 1120 km ) have been used. We have built and put into operation a dedicated instrument for the measurement of light yield and attenuation length over groups of 20 fibres at a time. The overall accuracy achieved in the measurement of light yield (attenuation length) is 1.5% (3%). We also report the results obtained using this method in the quality control of a large sample of fibres.
125411098
Radiation studies for the Readout Electronic of the ALICE Dimuon Forward Spectrometer
120140050
Studies of radiation effects in the NA60 silicon pixel detectors
Abstract NA60 is a fixed target experiment at the CERN SPS, which studies dimuon production in proton- and ion-induced collisions. Downstream of the target system a silicon pixel telescope made with p-on-n silicon sensors measures the charged tracks originating from the interactions. During the 2003 data taking period with indium–indium collisions at 158 GeV per incident nucleon, a significant radiation dose with a very inhomogeneous distribution has been accumulated in the pixel telescope, leading to partially type-inverted silicon sensors. Measurements of the depletion voltage and leakage current performed during this run are shown and compared with simulation results. It is also shown that the operation of partially type-inverted sensors poses no major problem.