International audienceIn view of the High-Luminosity phase of the Large Hadron Collider (LHC), in the barrel region of the CMS electromagnetic calorimeter (ECAL) the entire readout electronics will be replaced to cope with the more stringent requirements in terms of trigger latency, acquisition rate, and radiation and pileup resilience. The configuration sequence for the new on-detector electronics, involving both the improved very-front-end and front-end cards, is reported. The sequence of commands and parameters to load in the electronics is controlled by a software developed at CERN by the ECAL upgrade group and it will be the base on which to build the new data acquisition system (DAQ)

Chiusi, M

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Development of a DAQ system for the CMS ECAL Phase 2 recommissioning

In view of the High-Luminosity phase of the Large Hadron Collider (LHC), in the barrel region of the CMS electromagnetic calorimeter (ECAL) the entire readout electronics will be replaced to cope with the more stringent requirements in terms of trigger latency, acquisition rate, and radiation and pileup resilience. The configuration sequence for the new on-detector electronics, involving

both the improved very-front-end and front-end cards, is reported. The sequence of commands and parameters to load in the electronics is controlled by a software developed at CERN by the ECAL upgrade group and it will be the base on which to build the new data acquisition system (DAQ)

Chiusi, M.

Scientific Open-access Literature Archive and Repository

DOI 10.1393/ncc/i2023-23089-6Communications: SIF Congress 2022IL NUOVO CIMENTO 46 C (2023) 89Development of a DAQ system for the CMS ECAL Phase 2recommissioningM. Chiusi on behalf of the CMS CollaborationLLR, École polytechnique - Palaiseau, Francereceived 31 January 2023Summary. — In view of the High-Luminosity phase of the Large Hadron Col-lider (LHC), in the barrel region of the CMS electromagnetic calorimeter (ECAL)the entire readout electronics will be replaced to cope with the more stringent re-quirements in terms of trigger latency, acquisition rate, and radiation and pileupresilience. The configuration sequence for the new on-detector electronics, involvingboth the improved very-front-end and front-end cards, is reported. The sequenceof commands and parameters to load in the electronics is controlled by a softwaredeveloped at CERN by the ECAL upgrade group and it will be the base on whichto build the new data acquisition system (DAQ).1. – IntroductionThe Electromagnetic Calorimeter (ECAL) is a homogeneous calorimeter made of75848 lead tungstate (PbWO4) scintillating crystals. The crystals are divided into abarrel part (EB) with 61200 of them, covering the pseudorapidity region |η| < 1.48, andtwo endcap parts with 7324 crystals each extending the coverage to |η| < 3.0.ECAL measures with high accuracy the energies of electrons and photons by absorbingthem: the energy resolution achieved during past years ranges from 1.1 to 2.6% in thebarrel and 2.2 to 5% in the endcaps for photons from the Higgs boson decay [1].The main objective of the High-Luminosity LHC (HL-LHC) upgrade [2] of the LHCaccelerator is to deliver a much larger data set to the LHC experiments, for new physicssearches, Higgs boson coupling measurements, and precision tests of the standard model.The goals include reaching an instantaneous luminosity of 5 × 1034 cm2s−1 after 2029and an integrated luminosity of 250 fb−1 per year, with the goal of 3000 fb−1 in 12 yearsof operations.The main requirement of the EB upgrade is to maintain the Run 1 physics performancefor photons and electrons at the higher luminosity and pileup of the HL-LHC. In order toaccomplish this, the EB electronics must accommodate the Level-1 trigger requirementson latency and rate, in particular a latency up to 12.5 μs and an increased Level-1 triggerrate of up to 750 kHz.The current crystals and avalanche photo-diode (APD) detectors will remain, whilethe upgrade will affect the front-end and off-detector read-out electronics of EB. The newfront-end electronics will provide single crystal information to the off-detector electronics,where the trigger primitives will be formed in powerful FPGAs, and will guarantee a morec© CERN on behalf of the CMS CollaborationCreative Commons Attribution 4.0 License (http://creativecommons.org/licenses/by/4.0) 12 M. CHIUSI on behalf of the CMS COLLABORATIONprecise matching between the electromagnetic showers and tracks in order to improvebackground reduction.The very-front-end card, which provides pulse amplification, shaping, and digitizationfunctions of the signals, will be replaced. The chosen technology is a trans-impedanceamplifier (TIA), a device that generates an image of the APD photocurrent in outputof this latter. The pulse shaping will be shortened for a better filter of the increasedAPD noise and the sampling rate will be increased to 160MHz, to provide better timingresolution and spikes suppression (1) in the Level-1 trigger. TIA signals are sampled at160MHz —compared to the current 40MHz— by two identical 12-bit ADCs (4096 ADCchannels available). The digitized signals, or patterns, are transmitted to the front-endcards. Each card reads five independent channels, each controlling a single ECAL crystal.The front-end card transmits single crystal data to the back-end electronics systemusing four Low power Giga-Bit Transceiver (LpGBT), a radiation tolerant and multi-purpose ASIC, able to simultaneously execute the data readout, timing measurements,and to monitor the status of other electronic components. A Versatile Link plus (VTRx)which converts electrical signals into optical and viceversa is integrated in the board.The readout tower (RT), the simplest CMS ECAL data acquisition block, is composedof five very-front-end cards and a single front-end card. A low-voltage regulator providesprecise and stable values of voltage and current to the tower. Each tower —managedby four LpGBT chips— controls a matrix of 5 × 5 crystals of the ECAL barrel, i.e., 25different channels.2. – The configuration of the RTMany tests have been carried out at CERN by the ECAL upgrade group, whose mainpurpose is to assemble the new front-end electronics cards prototypes and perform datareadout with the first model of the back-end electronics card, named Barrel CalorimeterProcessor (BCP), to find the best and more stable configuration chain of an RT.The experimental setup allows to control the whole RT ASICs making use of Pythonscripts executed on the laboratory computers. These computers can communicate viaoptical fibers to the BCP, which forwards each command to the LpGBTs installed inthe front-end cards via the optical Link and TCLink protocol [3]. A single configurationcommand allows the user to access one or more chip registers for basic reading or writingoperations. During data acquisition, the off-detector electronics receives and buffers datafrom the detector front-end cards and implements functions for data integrity checks andalignment of event data to the provided clock. At the moment of writing, no PbWO4crystal is present in the setup, therefore the acquired raw data from the RT read, collectedand stored in the laboratory computers, are mainly electronic noise.Table I shows the entire RT configuration chain as it has been built by the ECALupgrade group. The procedure can be executed from a computer installed in the CERNlaboratory and takes ∼9 minutes. This procedure has to be executed every time the RTis powered on. Nevertheless, the basic configuration of the tower, executed periodicallyduring data acquisition, lasts ∼4 minutes. Indeed, the Phase-locked scan (PLL)(2) canbe avoided.(1) Spikes are signals generated by hadron-APD direct interaction. They have to be separatedfrom the signals and rejected.(2) A PLL is an electronic circuit able to match its own oscillation frequency with the one froman input signal. For correct data acquisition, the RT chips have to be synchronized with theBCP clock frequency.DEVELOPMENT OF A DAQ SYSTEM FOR THE CMS ECAL PHASE 2 RECOMMISSIONING 3Table I. – The RT configuration chain. Configuration time is given in the third column.Step Description TimeLpGBTs configuration A basic ASICs configuration —followed by a gen-eral reset of the boards— is performed. Mainly,clocks and e-links (radiation-hard and low-powerelectrical interfaces for chip-to-chip data trans-mission) are enabled in the LpGBTs and dis-tributed in the RT.20 sADCs PLL scan The ADCs are forced to send a specific patterninstead of APD data. Then, a reference voltagefor the ADC PLL circuit is set, and the data readby the BCP are checked to see if the pattern isrecognised. If it is the case, the ADC has lockedthe external clock and VFEs are synchronised. Ifnot, a new PLL value is set repeating the test.5 minRT channels bit align-mentThe good PLL values found in the previous stepare set. Each ADC is forced to send a specificpattern and the BCP to look for it among theacquired data. If not found, 1-bit shift is appliedat BCP level and this process is repeated.40 sADCs calibration TIAs are forced to send a reference voltage (∼1V)to the ADCs, which perform self-calibration.10 sPedestals optimization A specific value of current is sent by TIAs tothe ADCs. The peaks positions are collected andchecked by the BCP. If the average value is notin the desired range (around 20th ADC channel),higher current is provided.3 min3. – ResultsFigure 1 shows data acquisition before and after the RT configuration performedusing the ECAL group software. Since crystals are not yet installed in the setup, dataacquisitions show the electronic noise. On the left, before the ADCs calibration, thesampled data distribution of each channel is reported in blue. Moreover, since the samedataset has been divided into two different parts based on the sampling ADC of eachdata, two peaks (corresponding to two different ADCs of each channel, named ADC evenand odd) are visible. The position of each peak is higher than ADC channel 300 andthe ADCs odd and even mean values are not always matching. On the right, the sameblue peaks are presented as they appear after the RT calibration: the two ADCs are wellcalibrated and the corresponding peaks have compatible mean values. Moreover, theblue peak standard deviations are significantly reduced with values around ∼1.9 ADCchannels. Their positions lie around ADC channel 20, in order to maximise the availabledynamic range composed of 4096 channels.4 M. CHIUSI on behalf of the CMS COLLABORATIONFig. 1. – Electronic noise peaks from 3 channels of the RT as appearing during data acquisitionbefore (right) and after (left) the boards configuration. Distributions in blue (left and right)have been built including sampled data in their totality, whether they were sampled by ADCodd or even. Green and orange distributions (left) have been built using data respectively fromADC even and odd. For each peak, mean and standard deviation are reported.4. – ConclusionThe CMS barrel electromagnetic calorimeter will be upgraded for the HL-LHC Phase.The lead tungstate crystals and APD photodetectors will be retained. Both the on-detector and off-detector electronics will be replaced to cope with more demanding Phase-2 CMS trigger requirements, to maintain the best possible energy resolution, and toprovide improved capabilities for pileup and spike suppression necessary for the HL-LHC Phase. The software to configure the new front-end boards and to acquire rawdata, unpack, and visualize them was tested. It will be embedded in a more formal andoperative code and it will allow the future detector to efficiently control each RT. Effortswill be done to reduce the time required for a full configuration of the RT.REFERENCES[1] The CMS Collaboration, The Phase-2 Upgrade of the CMS Barrel Calorimeters (CERN)2017, https://cds.cern.ch/record/2283187.[2] Aberle O., Béjar Alonso I., Brüning O., Fessia P., Rossi L., Tavian L. andZerlauth M., High-Luminosity Large Hadron Collider (HL-LHC): Technical design report(CERN) 2020, https://cds.cern.ch/record/2749422.[3] Mendes E. B. De. Souza, Baron S. and Taylor M., TCLink: A TimingCompensated High-Speed Optical Link for the HL-LHC experiments (CERN) 2020,https://cds.cern.ch/record/2724958.

Development of a DAQ system for the CMS ECAL Phase 2

recommissioning

HAL-Polytechnique

In view of the High-Luminosity phase of the Large Hadron Collider (LHC), in the barrel region of the CMS electromagnetic calorimeter (ECAL) the entire readout electronics will be replaced to cope with the more stringent requirements in terms of trigger latency, acquisition rate, and radiation and pileup resilience.
The configuration sequence for the new on-detector electronics, involving both the improved very-front-end and front-end cards, is reported. The sequence of commands and parameters to load in the electronics is controlled by a software developed at CERN by the ECAL upgrade group and it will be the base on which to build the new data acquisition system (DAQ)

Chiusi, Marco

CERN Document Server

http://eprints.bice.rm.cnr.it/22661/1/ncc12659.pdf

Development of a DAQ system for the CMS ECAL Phase 2 recommissioning

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