Compact Muon Solenoid Electromagnetic Calorimeter Research Articles

DC-DC converters for the CMS MTD BTL and ECAL for HL-LHC

The Minimum Ionizing Particle Timing Detector (MTD) will be introduced in the Compact Muon Solenoid (CMS) experiment to measure the production time of Minimum Ionizing Particles (MIPs). Power Conversion Cards (PCCs) regulates and supplies low voltage to front end electronics of the MTD barrel, the Barrel Timing Layer (BTL). The PCCs host three radiation and magnetic field tolerant DC-DC converters. The physical height of the PCC is limited to 7 mm, having necessitated development of custom inductors and shields. Additionally, the CMS Electromagnetic Calorimeter will be upgraded. On-detector Low Voltage Regulator (LVR) cards host four DC-DC converters and one linear regulator. In these proceedings we will present both cards’ designs evolution, stack-up and layout optimization, noise filtering choices and a performance evaluation.

Software migration of the CMS ECAL Detector Control System during the CERN Large Hadron Collider Long Shutdown II

During the second long shutdown (LS2) of the CERN Large Hadron Collider (LHC), the Detector Control System (DCS) of the Compact Muon Solenoid (CMS) Electromagnetic Calorimeter (ECAL) is undergoing a large software upgrade at various levels. The ECAL DCS supervisory system has been reviewed and extended to migrate the underlying software toolkits and platform technologies to the latest versions. The resulting software will run on top of a new computing infrastructure, using the WinCC Open Architecture (OA) version 3.16 and newly developed communication drivers for some of the hardware. The ECAL DCS has been configured and managed from a different control version system and stored with more modern encoding and file formats. A new set of development guidelines has been prepared for this purpose, including conventions and recommendations from the CMS Central DCS and CERN Joint Controls Project (JCOP) framework groups. The large list of modifications also motivated the revision and reorganization of the software architecture, which is needed to resolve and satisfy additional software dependencies. Many modifications also aimed to improve the installation process, anticipating in some cases works for the next long shutdown upgrade.

Calibration and performance of the CMS Electromagnetic Calorimeter in LHC Run-II

Many physics analyses using the Compact Muon Solenoid (CMS) detector at the LHC require accurate, high resolution electron and photon energy measurements. Excellent energy resolution is crucial for studies of Higgs boson decays with electromagnetic particles in the final state, as well as searches for very high mass resonances decaying to energetic photons or electrons. The CMS electromagnetic calorimeter (ECAL) is a fundamental instrument for these analyses and its energy resolution is crucial for the Higgs boson mass measurement. Recently the energy response of the calorimeter has been precisely calibrated exploiting the full Run-II data, aiming at a legacy reprocessing of the data. A dedicated calibration of each detector channel has been performed with physics events such as electrons from W and Z boson decays, and photons from π0/η decays. This paper presents the calibration strategies that have been implemented and the excellent performance achieved by the CMS ECAL with the ultimate calibration of Run-II data, in terms of energy scale stability and energy resolution.

The upgrade and re-validation of the Compact Muon Solenoid Electromagnetic Calorimeter Control and Safety Systems during the Second Long Shutdown of the Large Hadron Collider at CERN

The Electromagnetic Calorimeter (ECAL) is one of the subdetectors of the Compact Muon Solenoid (CMS), a general-purpose particle detector at the CERN Large Hadron Collider (LHC). The CMS ECAL Detector Control System (DCS) and the CMS ECAL Safety System (ESS) have supported the detector operations and ensured the detector’s integrity since the CMS commissioning phase, more than 10 years ago. Over this long period, several changes to both systems were necessary to correct issues, extend functionality and keep them in-line with current hardware technologies and the evolution of software platforms. Due to the constraints imposed on significant changes to a running system, major hardware and software upgrades were therefore deferred to the second LHC Long Shutdown (LS2). This paper presents the architectures of the CMS ECAL control and safety systems, discusses the ongoing and planned upgrades, details implementation processes and validation methods and highlights the expectations for the post-LS2 systems.

Calibration and Performance of the CMS Electromagnetic Calorimeter in LHC Run2

Many physics analyses using the Compact Muon Solenoid (CMS) detector at the LHC require accurate, high resolution electron and photon energy measurements. Excellent energy resolution is crucial for studies of Higgs boson decays with electromagnetic particles in the final state, as well as searches for very high mass resonances decaying to energetic photons or electrons. The CMS electromagnetic calorimeter (ECAL) is a fundamental instrument for these analyses and its energy resolution is crucial for the Higgs boson mass measurement. Recently the energy response of the calorimeter has been precisely calibrated exploiting the full Run2 data, aiming at a legacy reprocessing of the data. A dedicated calibration of each detector channel has been performed with physics events exploiting electrons from W and Z boson decays, photons from π0 and η decays, and from the azimuthally symmetric energy distribution of minimum bias events. This talk presents the calibration strategies that have been implemented and the excellent performance achieved by the CMS ECAL with the ultimate calibration of Run2 data, in terms of energy scale stability and energy resolution.

Status report on the architecture and future upgrades of the CMS Electromagnetic Calorimeter Control And Safety Systems

The Electromagnetic Calorimeter (ECAL) is one of the particle detectors of the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC). For more than ten years, the CMS ECAL Detector Control System (DCS) and the CMS ECAL Safety Systems (ESS) have supported the experiment operation, contributing to its high availability and safety. The evolution of both systems to fulfil new requirements and constraints, in addition to optimizations towards improving usage and processes automation, led to several changes to their original design. This paper presents the current software/hardware architecture of both CMS ECAL control and safety systems and reviews the major changes applied to both systems during the past years. Furthermore, in view of the CMS Phase-II upgrade of this sub-detector, the corresponding plans for the control and safety systems are also discussed.

Cms Ecal Daq Monitoring System

The Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, has just completed the Run 2 era, colliding protons at a center-of-mass energy of 13 TeV at high instantaneous luminosity. The Compact Muon Solenoid (CMS) is a general-purpose particle detector experiment at the LHC. The CMS electromagnetic calorimeter (ECAL) has been designed to achieve excellent energy and position resolution for electrons and photons. A multi-machine distributed software configures the on-detector and off-detector electronic boards composing the ECAL data acquisition (DAQ) system and follows the life cycle of the acquisition process. Since the beginning of Run 2 in 2015, many improvements to the ECAL DAQ have been implemented to reduce and mitigate occasional errors in the front-end electronics and not only. Efforts at the software level have been made to introduce automatic recovery in case of errors. Automatic actions has made even more important the online monitoring of the DAQ boards status. For this purpose a new web application, EcalView, has been developed. It runs on a light Node.js JavaScript server framework. It is composed of several routines that cyclically collect the status of the electronics. It display the information when web requests are launched by client side graphical interfaces. For each board, detailed information can be loaded and presented in specific pages if requested by the expert. Server side routines store information regarding electronics errors in a SQLite database in order to perform offline analysis about the long term status of the boards.

Predicting the Performance of the CMS Precision PbWO4 Electromagnetic Calorimeter in the HL-LHC Era From Test Beam Results on Irradiated Crystals

The harsh radiation environment, in which detectors will have to operate during the high luminosity phase of the Large Hadron Collider, represents a crucial challenge for many calorimeter technologies. In the Compact Muon Solenoid (CMS) forward calorimeters, ionizing doses and hadron fluences will reach up to 300 kGy (at a dose rate of 30 Gy/h) and ${2\times 10^{14} cm^{-2}}$ , respectively, at the pseudorapidity region of $\vert \eta \vert $ = 2.6. To evaluate the evolution of the CMS electromagnetic calorimeter performance in such conditions, a set of PbWO4 crystals, which had previously been exposed to 24 GeV protons up to integrated fluences between ${2.1\times 10^{13} cm^{-2}}$ and ${1.3\times 10^{14} cm^{-2}}$ , has been studied in beam tests. A degradation of the energy resolution and a nonlinear response to electron showers are observed in damaged crystals. Direct measurements of the light output from the crystals show the amplitude decreasing and pulse becoming faster as the fluence increases. The evolution of the performance of the PbWO4 crystals has been well understood and parameterized in terms of increasing light absorption inside the crystal volume. A double-sided readout configuration, in which two identical photodetectors are coupled to the opposite ends of each crystal, has also been tested. The separate and simultaneous readout of the light from the two sides of the crystal allows us to correct for longitudinal shower fluctuations and to mitigate the degradation of energy resolution in highly damaged crystals. The nonlinear response to electromagnetic showers, arising from high nonuniformity of light collection efficiency along the longitudinal axis of irradiated crystals, can also be corrected by means of the double-sided readout technique.

Performance of the CMS precision electromagnetic calorimeter at LHC Run II and prospects for High-Luminosity LHC

Many physics analyses using the Compact Muon Solenoid (CMS) detector at the LHC require accurate, high-resolution electron and photon energy measurements. Following the excellent performance achieved during LHC Run I at center-of-mass energies of 7 and 8 TeV, the CMS electromagnetic calorimeter (ECAL) is operating at the LHC with proton-proton collisions at 13 TeV center-of-mass energy. The instantaneous luminosity delivered by the LHC during Run II has achieved unprecedented levels. The average number of concurrent proton-proton collisions per bunch-crossing (pileup) has reached up to 40 interactions in 2016 and may increase further in 2017. These high pileup levels necessitate a retuning of the ECAL readout and trigger thresholds and reconstruction algorithms. In addition, the energy response of the detector must be precisely calibrated and monitored. We present new reconstruction algorithms and calibration strategies that were implemented to maintain the excellent performance of the CMS ECAL throughout Run II. We will show performance results from the 2015-2016 data taking periods and provide an outlook on the expected Run II performance in the years to come. Beyond the LHC, challenging running conditions for CMS are expected after the High-Luminosity upgrade of the LHC (HL-LHC) . We review the design and R&D studies for the CMS ECAL and present first test beam studies. Particular challenges at HL-LHC are the harsh radiation environment, the increasing data rates, and the extreme level of pile-up events, with up to 200 simultaneous proton-proton collisions. We present test beam results of hadron irradiated PbWO crystals up to fluences expected at the HL-LHC . We also report on the R&D for the new readout and trigger electronics, which must be upgraded due to the increased trigger and latency requirements at the HL-LHC.

The CMS Electromagnetic Calorimeter: overview, lessons learned during Run 1 and future projections

The Electromagnetic Calorimeter (ECAL) of the Compact Muon Solenoid (CMS) experiment at the LHC is a hermetic, fine grained, homogeneous calorimeter, containing 75,848 lead tungstate scintillating crystals. We highlight the key role of the ECAL in the discovery and elucidation of the Standard Model Higgs boson during LHC Run I. We discuss, with reference to specific examples from LHC Run I, the challenges of operating a crystal calorimeter at a hadron collider. Particular successes, chiefly in terms of achieving and maintaining the required detector energy resolution in the harsh radiation environment of the LHC, are described. The prospects for LHC Run II (starting in 2015) are discussed, building upon the experience gained from Run I. The high luminosity upgrade of the LHC (HL-LHC) is expected to be operational from about 2025 to 2035 and will provide instantaneous and integrated luminosities of around 5 × 1034/cm2/s and 3000/fb respectively. We outline the challenges that ECAL will face and motivate the evolution of the detector that is thought to be necessary to maintain its performance throughout LHC and High-Luminosity LHC operation.

The upgrade and re-validation of the Compact Muon Solenoid Electromagnetic Calorimeter Control System

The Electromagnetic Calorimeter (ECAL) is one of the sub-detectors of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) at CERN. The Detector Control System (DCS) that has been developed and implemented for the CMS ECAL was deployed in accordance with the LHC schedule and has been supporting the CMS data-taking since LHC physics runs started in 2009. During these years, the control system has been regularly adapted according to operational experience and new requirements, always respecting the constraints imposed on significant changes to a running system. Several hardware and software upgrades and system extensions were therefore deferred to the first LHC Long Shutdown (LS1). This paper presents the main architectural differences between the system that supported the CMS ECAL during its first years and the new design for the coming physics runs after LS1. Details on the upgrade planning, including the certification methods performed in the CMS ECAL DCS laboratory facilities, reports on the implementation progress and the expectations for the post-LS1 system are highlighted.

Laser monitoring for the CMS ECAL

The Compact Muon Solenoid (CMS) detector at the LHC is equipped with a high precision lead tungstate crystal electromagnetic calorimeter (ECAL). To ensure the stability of the calorimetric response at the level of a few per mille, every channel of the detector is monitored with a laser system. This system enables corrections for fluctuations in the detector response with high precision, in particular the expected radiation induced changes in the crystal transparency. We describe the implementation of the laser monitoring system and report results from tests on the fully equipped supermodules of the ECAL. Specifically, we discuss results concerning the dynamics of crystal transparency change from dedicated irradiation studies in test beams.

Status of the CMS PbWO 4 Electromagnetic Calorimeter

In the mass range of 110-150 GeV the favored process for Higgs boson detection via p-p collisions is via its decay into two photons, which demands a very high-resolution electromagnetic calorimeter. This physics goal plus the Large Hadron Calorimeter (LHC)-imposed design constraints of 25ns bunch spacing and a hostile radiation environment have led the Compact Muon Solenoid (CMS) collaboration to the choice of lead tungstate (PbWO4) crystals. Their relatively low room-temperature scintillation photon yield plus the presence of a 4T magnetic field have motivated the choice of photodetection devices providing gain amplification: Avalanche photodiodes (APD) in the central barrel region and vacuum phototriodes (VPT) in the forward endcap regions. In 2002 and 2003 significant changes were undertaken to the radiation-hard ∼95dB-dynamic-range readout electronics system, which now features 0.25μm CMOS ASICs, and which has been tested for the first time in particle beams. The CMS electromagnetic calorimeter is now in the construction phase. We review progress in the areas of crystals, barrel and endcap photodetection devices, the implementation of the readout electronics system redesign and the scintillation light loss monitoring system, as well as the status of assembly and quality control. We also present selected results from the autumn 2003 test beam program including noise performance obtained with the redesigned readout electronics, and irradiation studies demonstrating the performance of the laser monitoring system.

Recent developments in crystal calorimeters (featuring the CMS PbWO 4 electromagnetic calorimeter)

In the mass range of 110–150 GeV the favored process for Higgs boson detection via p-p collisions is via its decay into two photons, which demands a very high-resolution electromagnetic calorimeter. This physics goal plus the Large Hadron Calorimeter (LHC)-imposed design constraints of 25ns bunch spacing and a hostile radiation environment have led the Compact Muon Solenoid (CMS) collaboration to the choice of lead tungstate (PbWO 4) crystals. These factors plus the presence of a 4T magnetic field and the relatively low room-temperature scintillation photon yield of PbWO 4 make photodetection a real challenge, which CMS has met via the choice of devices providing gain amplification: Avalanche photodiodes (APD) in the central barrel region and vacuum phototriodes (VPT) in the forward and backward endcap regions. In the past year the CMS electromagnetic calorimeter has entered the construction phase. We review progress in the areas of crystals, barrel and endcap photodetection devices, plans for detector calibration as well as the status of assembly and quality control. We also invoke relevant developments in other crystal calorimeters currently in operation or under development. Crystal calorimeters remain the medium of choice for precision energy and position measurements in high energy physics.

Workflow management in the assembly of CMS ECAL

As with all experiments in the LHC era, the Compact Muon Solenoid (CMS) detectors will be constituted of a very large number of constituent parts. Typically, each major detector may be constructed out of over a million precision parts and will be produced and assembled during the next decade by specialised centres distributed world-wide. Each constituent part of each detector must be accurately measured and tested locally prior to its ultimate assembly and integration in the experimental area at CERN. Much of the information collected during this phase will be needed not only to construct the detector, but for its calibration, to facilitate accurate simulation of its performance and to assist in its lifetime maintenance. The CRISTAL system is a prototype being developed to monitor and control the production and assembly process of the CMS Electromagnetic Calorimeter (ECAL). The software will be generic in design and hence reusable for other CMS detector groups. This paper discusses the distributed computing problems and design issues posed by this project. The overall software design architecture is described together with the main technology aspects of linking distributed object oriented databases via CORBA with WWW/Java-based query processing. The paper then concentrates on the design of the workflow management system of CRISTAL.