Energy Resolution Performance of the CMS Electromagnetic Calorimeter

The energy resolution performance of the CMS lead tungstate crystal electromagnetic calorimeter is presented. Measurements were made with an electron beam using a fully equipped supermodule of the calorimeter barrel. Results are given both for electrons incident on the centre of crystals and for electrons distributed uniformly over the calorimeter surface. The electron energy is reconstructed in matrices of 3 times 3 or 5 times 5 crystals centred on the crystal containing the maximum energy. Corrections for variations in the shower containment are applied in the case of uniform incidence. The resolution measured is consistent with the design goals

Silicon sensors for the CMS Preshower

The paper is a summary of a research and development program, conducted during the past three years on the CMS Preshower silicon sensors with the goal at defining the specifications. The main point was the radiation hardness of these devices, resulting from the specific design: metal lines wider than the p+ implants and a series of guard rings, and to the production technology: a deep n+ layer on the ohmic side. An acceptable noise and a uniform charge collection were guaranteed by an appropriate choice of the interstrip region width. About 65 sensors, of different designs and coming from six manufacturers, were irradiated with neutrons and protons and thoroughly tested before and after irradiation. The results of the tests and the final specifications are presented

The Muons Registration Efficiency of the CMS ECAL Preshower in the Integrated Test

The Muon registration efficiency of the Preshower was estimated from experimental data of the Integrated Test of the module, that is a prototype of the CMS Endcap detector. In the work it is shown that the muon registration efficiency of the preshower plane is 93% for the muon particles with the energy from 100 to 300 GeV in 3 Tesla axial magnetic field. It was mainly defined by the noise value of the electronics devices-AMPLEX SICAL chips. The muons energy loss distribution in the preshower planes was investigated. A mathematical method was proposed to describe the distribution of the energy losses taking into account the intrinsic noise of the electronics devices. A comparison of the experimental data with the simulation results was made

Performance of Si sensors irradiated 5x1014 n/cm2

The expected particle fluence in the inner part of the CMS Preshower is calculated to be 1.6x1014 cm^-2 for neutrons and 0.4x1014 cm2 for charged hadrons. Since the error of the calculation is high and/or unexpected accidental beam miss-alignments might happen we have irradiated Preshower silicon sensors to fluences up to 5x1014 n/cm2 to verify that they hold voltages necessary to reach the full charge collection efficiency. All irradiated sensors showed no signs of breakdown up to 1000 V, the maximum voltage applied. For all but one the operating voltage was lower than 900 V and a charge collection efficiency plateau was at least 200 V long. No noisy channels were observed at the extreme voltages. The measured charge was 71+-12% and 59+-12% for sensors irradiated to 3x1014 n/cm2 and 5x1014 n/cm2, respectively. These values are consistent with the extrapolation from previous measurements made on sensors irradiated to 2.3x1014 n/cm2. The work presents the results of static and dynamic measurements and shows that our design and the technology are very robust

Performance Study of Non-Irradiated Prototype Silicon Preshower Samplers for CMS

The performance of the prototype silicon preshower detectors for the CMS experiment has been studied at CERN-PS. The charge collection efficiency for different regions of the geometrical wafer layout is examined. The lateral shower profile and spatial resolution are investigated for electrons with energies between 1 and 12 GeV

High Voltage Performance of Silicon Detectors Irradiated under Bias

The CMS Preshower detector contains 16 sq. m of silicon. The silicon sensors' design is being finalized by taking into account their performance after five years of operation at high luminosity. Three detectors from different manufacturers were irradiated by neutrons and photons under bias and at low temperature. Their electrical parameters and their response to alpha and beta particles were measured. The charge collection efficiency attains a plateau at around 300 V. The irradiation set-up and the results of the measurements are presented in this paper

Results from the 1999 Beam Test of a Preshower Prototype

At the end of June 1999 a test of a preshower prototype, equipped with real-size detectors and LHC-style electronics, was tested in the H4 beam at CERN in front of a matrix of "Endcap" crystals. Data were taken with a variety of incident electron energies, and three angles of incidence ( to simulate different regions of the CMS endcaps). The prototype functioned well, with a very small startup period and operated successfully for the duration of the test ( ~ 1 week) without intervention. Good agreement has been found between data and a GEANT-3 based simulation, and the absolute results are promising. Plans are presented for a further test of the prototype in 2000 in the H2 beam inside the 3T magnet