Data Filtering in the readout of the CMS Electromagnetic Calorimeter

For an efficient data taking, the Electromagnetic Calorimeter (ECAL) data of the CMS experiment must be limited to 10\% of the full event size (1MB). Other requirements limit the average data size to 2kB per data acquisition link. These conditions imply a reduction factor of close to twenty on the data collected. The data filtering in the readout of the ECAL detector is discussed. Test beam data are used to study the digital filtering applied in the readout channels and a full detector simulation allows to estimate the energy thresholds to achieve the desired data suppression factor

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

A Three-Step Low-Power Multichannel TDC Based on Time Residual Amplifier

International audienceThis article proposes and evaluates an architecture for a low-power time-to-digital converter (TDC) with high resolution, optimized for high-rate operation (40 MSa/channel), and integration with analog front end in multichannel readout chips in 130-nm CMOS technology. The converter is based on a three-step architecture. The first step uses a counter and the following ones are based on two types of delay-line (DL) structures. A programmable time amplifier (TA) is used between the second and third steps to reach a final resolution of 24.4 ps in the standard mode of operation. In addition, this architecture uses common continuously stabilized reference blocks that control the channels against the effects of global process, voltage, and temperature (PVT) variations. We also propose a per-channel DL gain correction based on a trimmable block to correct the mismatch effect. The area of the TDC channel is only 0.051 mm2. For a 40-MSa/channel rate, the TDC average power consumption measured per channel is 2.2 mW for a 100% hit occupancy and decreases to 311 $\mu \text{W}$ for the 10% occupancy specified for our main application. The demonstrated compactness and low power consumption fully match our requirements for integration into multichannel front-end chips. The experimental results demonstrate good timing performance over a broad range of operating temperatures (-35 degrees C and 65 degrees C), which conforms to our expectations. For example, the measured timing integral nonlinearity (INL) is better than +/- 1 LSB (+/- 25 ps), and the overall timing precision is better than 21-ps rms

The selective read-out processor for the CMS electromagnetic calorimeter

This paper describes the selective read-out processor (SRP) proposed for the electromagnetic calorimeter (ECAL) of the Compact Muon Solenoid (CMS) experiment at LHC (CERN). The aim is to reduce raw ECAL data to a level acceptable by the CMS data acquisition (DAQ) system. For each positive level 1 trigger, the SRP is guided by trigger primitive generation electronics to identify ECAL regions with energy deposition satisfying certain programmable criteria. It then directs the ECAL read-out electronics to apply predefined zero suppression levels to the crystal data, depending whether the crystals fall within these regions or not. The main challenges for the SRP are some 200 high speed (1.6 Gbit/s) I/O channels, asynchronous operation at up to 100 kHz level 1 trigger rate, a 5- mu s real-time latency requirement and a need to retain flexibility in choice of selection algorithms. The architecture adopted for the SRP is based on modern parallel optic pluggable modules and high density field programmable gate array (FPGA) devices with embedded processors and multigigabit transceivers. Implementation studies to validate proposed solutions are presented. The performance of envisaged selection algorithms is investigated with the CMS detector simulation software. The robustness of optical communication channels is estimated via direct measurements and calculations. The feasibility to perform data reduction operations within the allocated timing budget is verified by running a representative SRP firmware on a development board with a Xilinx Virtex2Pro FPGA device

Status of the BONuS12 Radial Time Projection Chamber

International audiencePart of the experimental program in Hall B of the Jefferson Lab, Virginia, USA is dedicated to studying neutron structure functions using deep inelastic scattering on nuclei. For this purpose, the BONuS12 experiment will detect low momentum recoil protons in coincidence with scattered electrons. The protons will be detected by a second-generation Radial Time Projection Chamber (RTPC) using triple Gas Electron Multiplier foils for amplification while the scattered electrons will be detected by the CLAS12 spectrometer installed in Hall B. The following article presents the status of the BONuS12 RTPC detector that will take data within the next 2 years. The main improvements made from the previous BONuS RTPC: the new electronics and mounting process are presented. We also detail some aspect of the gas simulation

Electromagnetic Calorimeter Raw Data Format

This document describes the Electromagnetic Calorimeter (ECAL) raw data format, which is generated by the ECAL Data Concentrator Card (DCC) sitting on the ECAL Off-Detector electronics crates. The DCC actions in response to possible errors in the input data are discussed. A software package responsible for the event decoding and data integrity monitoring, developed for the ECAL On-line and Off-line systems, is presented

Discovery of a big void in Khufu’s Pyramid by observation of cosmic-ray muons

International audienceThe Great Pyramid or Khufu’s Pyramid was built on the Giza Plateau (Egypt) during the IVth dynasty by the pharaoh Khufu (Cheops), who reigned from 2509 to 2483 BC$^1$ . Despite being one of the oldest and largest monuments on Earth, there is no consensus about how it was built. To better understand its internal structure, we imaged the pyramid using muons, which are by-products of cosmic rays that are only partially absorbed by stone. The resulting cosmic-ray muon radiography allows us to visualize the known and potentially unknown voids in the pyramid in a non-invasive way. Here we report the discovery of a large void (with a cross section similar to the Grand Gallery and a length of 30m minimum) above the Grand Gallery, which constitutes the first major inner structure found in the Great Pyramid since the 19$^{th}$ century. This void, named ScanPyramids Big Void, was first observed with nuclear emulsion films installed in the Queen’s chamber (Nagoya University), then confirmed with scintillator hodoscopes set up in the same chamber (KEK) and re-confirmed with gas detectors12 outside of the pyramid (CEA)This large void has therefore been detected with a high confidence by three different muon detection technologies andthree independent analyses. These results constitute a breakthrough for the understanding of Khufu’s Pyramid and its internal structure. While there is currently no information about the role of this void, these findings show how modern particle physics can shed new light on the world’s archaeological heritag

Energy Resolution of the Barrel of the CMS Electromagnetic Calorimeter

The energy resolution of the barrel part of the CMS Electromagnetic Calorimeter has been studied using electrons of 20 to 250 GeV in a test beam. The incident electron's energy was reconstructed by summing the energy measured in arrays of 3x3 or 5x5 channels. There was no significant amount of correlated noise observed within these arrays. For electrons incident at the centre of the studied 3x3 arrays of crystals, the mean stochastic term was measured to be 2.8% and the mean constant term to be 0.3%. The amount of the incident electron's energy which is contained within the array depends on its position of incidence. The variation of the containment with position is corrected for using the distribution of the measured energy within the array. For uniform illumination of a crystal with 120 GeV electrons a resolution of 0.5% was achieved. The energy resolution meets the design goal for the detector