MDT Chambers Research Articles

Test result of the new ASD2 chips for Phase-II upgrade of the ATLAS MDT chambers at HL-LHC

For the Phase-II upgrade of the ATLAS Muon Spectrometer to High-Luminosity LHC, new front-end readout electronics for the Monitored Drift Tube chambers is required, as the old one no longer meets the demands. The first stage in the Monitored Drift Tubes readout chain is the Amplifier-Shaper-Discriminator chip. For the upgrade, the new ASD2 ASIC chip in IBM 130 nm CMOS technology has been developed. For the ATLAS experiment, 80000 ASD2 chips are produced, which have to be tested before integration in order to obtain the required 50000 well-performing chips in the end. Using a prototype tester board and pre-production ASD2 chips, the overall performance and the influence on programmable parameters is investigated. Based on these results, 1775 production chips are tested to define final optimized cut values for the automated production testing of all chips in the company.

The readout panels for the BI-RPC project for ATLAS Phase-II upgrade

To take full advantage from the LHC upgrade to high luminosity in 2029, the ATLAS community has approved an intensive detector upgrade program that includes the construction of an additional trigger layer positioned close to the BI MDT chambers of the muon spectrometer. These chambers are RPC with thin gas gap, thin High Pressure Laminate electrodes coated with graphite on one side, and only use strips orthogonal to the beam-axis to reconstruct the eta and phi coordinates of the detector point where an ionizing particle passes. A detailed description of the construction and validation of these strip panels in China and Italy assembly sites, is presented here.

Certification of the amplifier-shaper-discriminator ASICs produced for the ATLAS MDT chambers at the HL-LHC

The front-end electronics of the ATLAS muon drift-tube chambers will be upgraded in the experiment’s phase-II upgrade to comply with the new trigger and read-out scheme at the HL-LHC. A new amplifier shaper discriminator chip was developed in 130 nm Global Foundries technology for this upgrade. A preproduction of 7500 chips was launched in 2019 and tested in 2020. The functionality of the chips, the test set-up and test procedure and results showing a yield of 93% are presented. The certification of the preproduction was followed by the production of 80,000 chips in fall 2020. The tests of a sample of 2949 preproduction and 1174 production chips gave a production yield > 93%.

Construction and testing of sMDT tubes at the University of Michigan for the ATLAS Muon Spectrometer upgrade

This paper reports on the design and construction of infrastructure and test stations for small-diameter monitored drift tube (sMDT) assembly and testing at the University of Michigan (UM) to prepare for the ATLAS Muon Spectrometer upgrade for the high-luminosity program of the Large Hadron Collider. Procedures of the tube assembly and quality assurance and control (QA/QC) tests are described in detail. More than 99% of the tubes meet the tube QA/QC specifications based on 2100 tubes built at UM. The UM test stations are also used for QA/QC testing on the tubes constructed at Michigan State University. These tubes are being used to construct the sMDT chambers which will replace the current MDT chambers of the barrel inner station of the Muon Spectrometer.

The ATLAS Muon Spectrometer upgrade for High-Luminosity LHC

The muon spectrometer of the ATLAS detector will undergo a major upgrade in order to cope with the operational conditions at the high-luminosity LHC. The trigger and readout system will need to support Level-0 trigger rates of 1 MHz and a latency of 10 μs. The readout electronics of all the trigger and precision chambers will be replaced and the precision chambers, currently not included in the hardware trigger, will be integrated into the Level-0 trigger in order to sharpen the momentum threshold and increase the system redundancy. New-generation RPC chambers will be installed in the inner barrel layer to increase the acceptance and robustness of the trigger. Some of the MDT chambers in the inner barrel layer will be replaced with new small-diameter MDTs. New TGC triplet chambers will replace the current TGC doublets in the barrel-endcap transition region to enhance the suppression of fake triggers in this region. A major upgrade of the power system is also planned. In this presentation the main detector technology developments of the project will be presented.

Upgrades of the ATLAS muon spectrometer with new small-diameter drift tube chambers

Abstract Small diameter muon drift-tube (sMDT) chambers with 15 mm tube diameter provide excellent spatial resolution like the MDT chambers with 30 mm tube diameter used in the ATLAS muon spectrometer so far, but can be operated at ten times higher background rates and allow for the instrumentation of regions where MDT chambers do not fit in. In April 2014 two such chambers (called BME) have been installed at the bottom of the barrel middle layer of the muon spectrometer, followed in January 2016 by another 12 sMDT chambers (called BMG) inserted in the detector feet in the barrel middle layer. They are since then operational in ATLAS, increasing the acceptance for precision muon momentum measurement in all three chamber layers. An unprecedently high sense wire positioning accuracy of 5 μ m (rms) has been achieved. In the next long LHC shutdown 2019–2020, 16 new sMDT chambers (called BIS 78) will be installed in the barrel inner layer in the transition region to the endcaps in order to make room for the installation of new RPC muon trigger chambers which will reduce the accidental trigger rate in this region as required for operation at the high-luminosity upgrade of the LHC (HL-LHC). This is a pilot project for the complete replacement of the MDT chambers in the small azimuthal sectors of the barrel inner layer (called BIS 1-6) by integrated sMDT-RPC detectors in the long shutdown 2024–2026 for the upgrade to HL-LHC.

Design and construction of integrated small-diameter drift tube and thin-gap resistive plate chambers for the phase-1 upgrade of the ATLAS muon spectrometer

In the long shutdown for the Phase-1 upgrade of the Large Hadron Collider (LHC) in 2019–2020, 16 new integrated muon tracking and trigger chambers will be installed at the ends of the toroid magnet coils in the small azimuthal sectors of the inner barrel layer (BIS) of the ATLAS muon spectrometer in order to improve the trigger selectivity and fake trigger suppression in the transition region 1 . 0 < | η | < 1 . 3 between the barrel part and the endcaps. The new muon detectors consist of a small-diameter muon drift tube (sMDT) precision tracking chamber with 15 mm tube diameter and a pair of thin-gap RPC chambers with 1 mm gas gap width. The new integrated chamber modules (labeled BIS 78) are currently under construction and will replace the present BIS 7 and 8 MDT tracking chambers with 30 mm diameter drift tubes. The project is the pilot phase for the complete replacement of the small barrel inner layer MDT chambers with the new integrated tracking and trigger detectors in the ATLAS Phase-2 upgrade in 2024–2026 in order to increase the barrel first-level muon trigger coverage and efficiency at the high luminosities at HL-LHC. The sMDT chambers have been chosen to make room for the new trigger chambers and because of their eight times higher rate capability than MDT chambers. The new thin-gap RPC chambers have about 15 times lower avalanche charges and correspondingly increased lifetime and rate capability at HL-LHC and will be operated in coincidence with the endcap trigger chambers. They consist of a triplet of gas gaps which has to be very thin as well and which is supported by a light-weight aluminum structure which is interleaved with the sMDT chamber supports.

New high-precision drift-tube detectors for the ATLAS muon spectrometer

Small-diameter muon drift tube (sMDT) detectors have been developed for upgrades of the ATLAS muon spectrometer. With a tube diameter of 15 mm, they provide an about an order of magnitude higher rate capability than the present ATLAS muon tracking detectors, the MDT chambers with 30 mm tube diameter. The drift-tube design and the construction methods have been optimised for mass production and allow for complex shapes required for maximising the acceptance. A record sense wire positioning accuracy of 5 μm has been achieved with the new design. In the serial production, the wire positioning accuracy is routinely better than 10 μm. 14 new sMDT chambers are already operational in ATLAS, further 16 are under construction for installation in the 2019–2020 LHC shutdown. For the upgrade of the barrel muon spectrometer for High-Luminosity LHC, 96 sMDT chambers will be contructed between 2020 and 2024.

Construction and test of new precision drift-tube chambers for the ATLAS muon spectrometer

ATLAS muon detector upgrades aim for increased acceptance for muon triggering and precision tracking and for improved rate capability of the muon chambers in the high-background regions of the detector with increasing LHC luminosity. The small-diameter Muon Drift Tube (sMDT) chambers have been developed for these purposes. With half of the drift-tube diameter of the MDT chambers and otherwise unchanged operating parameters, sMDT chambers share the advantages of the MDTs, but have an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit in. The chamber assembly methods have been optimized for mass production, minimizing construction time and personnel. Sense wire positioning accuracies of 5μm have been achieved in serial production for large-size chambers comprising several hundred drift tubes. The construction of new sMDT chambers for installation in the 2016/17 winter shutdown of the LHC and the design of sMDT chambers in combination with new RPC trigger chambers for replacement of the inner layer of the barrel muon spectrometer are in progress.

Performance of the new Amplifier-Shaper-Discriminator chip for the ATLAS MDT chambers at the HL-LHC

The Phase-II Upgrade of the ATLAS Muon Detector requires new electronics for the readout of the MDT drift tubes. The first processing stage, the Amplifier-Shaper-Discriminator (ASD), determines the performance of the readout for crucial parameters like time resolution, gain uniformity, efficiency and noise rejection. An 8-channel ASD chip, using the IBM 130 nm CMOS 8RF-DM technology, has been designed, produced and tested. The area of the chip is 2.2 × 2.9 mm2 size. We present results of detailed measurements as well as a comparison with simulation results of the chip behavior at three different levels of detail.

Precision muon tracking detectors and read-out electronics for operation at very high background rates at future colliders

The experience of the ATLAS MDT muon spectrometer shows that drift-tube chambers provide highly reliable precision muon tracking over large areas. The ATLAS muon chambers are exposed to unprecedentedly high background of photons and neutrons induced by the proton collisions. Still higher background rates are expected at future high-energy and high-luminosity colliders beyond HL-LHC. Therefore, drift-tube detectors with 15mm tube diameter (30mm in ATLAS), optimised for high rate operation, have been developed for such conditions. Several such full-scale sMDT chambers have been constructed with unprecedentedly high sense wire positioning accuracy of better than 10μm. The chamber design and assembly methods have been optimised for large-scale production, reducing considerably cost and construction time while maintaining the high mechanical accuracy and reliability. Tests at the Gamma Irradiation Facility at CERN showed that the rate capability of sMDT chambers is improved by more than an order of magnitude compared to the MDT chambers. By using read-out electronics optimised for high counting rates, the rate capability can be further increased.

A highly selective first-level muon trigger with MDT chamber data for ATLAS at HL-LHC

Highly selective triggers are essential for the physics programme of the ATLAS experiment at HL-LHC where the instantaneous luminosity will be about an order of magnitude larger than the LHC instantaneous luminosity in Run 1. The first level muon trigger rate is dominated by low momentum muons below the nominal trigger threshold due to the moderate momentum resolution of the Resistive Plate and Thin Gap trigger chambers. The resulting high trigger rates at HL-LHC can be sufficiently reduced by using the data of the precision Muon Drift Tube chambers for the trigger decision. This requires the implementation of a fast MDT read-out chain and of a fast MDT track reconstruction algorithm with a latency of at most 6μs. A hardware demonstrator of the fast read-out chain has been successfully tested at the HL-LHC operating conditions at the CERN Gamma Irradiation Facility. The fast track reconstruction algorithm has been implemented on a fast trigger processor.

ATLAS Muon Calibration Framework

Automated calibration of the ATLAS detector subsystems (like MDT and RPC chambers) are being performed at remote sites, called Remote Calibration Centers. The calibration data for the assigned part of the detector are being processed at these centers and send the result back to CERN for general use in reconstruction and analysis. In this work, we present the recent developments in data discovery mechanism and integration of Ganga as a backend which allows for the specification, submission, bookkeeping and post processing of calibration tasks on a wide set of available heterogeneous resources at remote centers.

First cosmic ray results of the RPC commissioning in the ATLAS cavern

The first commissioning test of three muon towers of the ATLAS Muon Spectrometer, installed in the cavern, was carried out. The stations under test belong to the barrel sector 13, which is a large sector. A muon tower consists of three stations: the Inner, the Middle and the Outer, starting from the interaction point. The Barrel Inner Large (BIL) stations are constituted by MDT chambers; the Barrel Middle Large (BML) stations by MDTs assembled between two RPC chambers; and the Barrel Outer Large (BOL) stations by MDTs with only one RPC mounted downstream. Specific Level-1 trigger algorithms have been studied to trigger on cosmic rays and implemented to commission the muon stations. Comparison between the measured trigger rate and the simulated results will be presented. Moreover, the RPC performances have been studied by comparing the MDT track extrapolations with the firing RPC readout strips. The RPC detection efficiency is evaluated in the eta measuring view, resulting as a combination of gas volume efficiency and Front-End efficiency.

Global Time Fit for Tracking in an Array of Drift Cells: The Drift Tubes of the ATLAS Experiment

We present a global time fit to determine the reference time event-by-event in an array of drift cells. The method is applied to the monitored drift tube tracking chambers (MDT) of the muon spectrometer of the ATLAS experiment at the large hadron collider (LHC). During operation with proton-proton collisions, the muon trigger is based on dedicated fast detectors and the readout is clocked at the beam crossing frequency of 40 MHz. A method has been developed for tracking particles through the MDT chambers which works without a precisely timed external trigger. This study was conceived to exploit the MDT tracking capabilities in non standard operation of the ATLAS detector, e.g., during commissioning with cosmic rays when there is no time correlation with the LHC clock frequency. Results obtained using an asynchronous trigger, with a high energy muon beam from the CERN SPS, and with cosmic rays are reported.

Development of a gas filter against wire chamber ageing for the MDT chambers in ATLAS

Drift chamber ageing is a serious concern for the operation of the Monitored Drift Tube chambers (MDT) in the ATLAS muon system. Therefore systematic studies of ageing effects have been carried out at the University of Freiburg. It has been shown that tiny contaminations with volatile silicon compounds, which are found in many components supplied by industry, cause a severe degradation of the drift tube performance. Since the ATLAS MDT system contains many thousands of commercial components the cleanliness of all parts cannot be guaranteed. Therefore gas filters with zeolites have been developed in Freiburg, which remove these impurities efficiently. They will be employed in the gas system for the MDT chambers.

Intensive Irradiation Study on Monitored Drift Tubes Chambers

Monitored drift tube chambers (MDT) are the precision tracking detectors in the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC). From simulations of the LHC operating conditions, the count rate in the inner barrel chamber of the muon spectrometers is expected to reach 500 Hz/cm2 and can be ten times higher in the luminosity upgrade under discussion (SLHC). A degradation of the performances of drift tube chambers after extended operation in high-rate environment is usually caused by the formation of deposits on the anode wire. To study MDTs aging, three bundles of short tubes equipped like a final MDT chamber were irradiated in different periods with neutrons and photons using the TAPIRO nuclear reactor and the CALLIOPE gamma facility at the ENEA-Casaccia Research Center (Italy). The MDT performances with respect to accumulated dose were studied with cosmic rays and results on drift and tracking properties are presented.

Determination of the ATLAS MDT chambers response to 0.5–10 MeV neutrons and development of a simulation model

The study of the MDT chambers performance under the presence of a high neutron and gamma background radiation in a wide neutron energy range is presented in this work. The neutrons were provided by the TANDEM Van Der Graaff accelerator of NCSR “Demokritos”. Emphasis was given to the comprehension of all the interactive mechanisms resulting from the presence of the high background radiation, with respect to the neutron energy and the MDT materials. The MDT response to neutrons with energies 0.5–10.0 MeV was determined. A simulation model, based on the Geant4 program, was used to describe the experimental setup and the neutron impact. The simulation results were found to be in good agreement with the experimental results.

Gamma and neutron massive irradiation tests of the ATLAS MDT chambers

MDT chambers, the precision tracking system of the ATLAS muon spectrometer, have to operate for 10 years in the harsh LHC background environment mainly due to low energy photons and neutrons. The expected overall maximum count rate is 500 Hz / cm 2 . Moreover the upgrades for S-LHC will involve fluxes ten times higher than that at LHC. To study the behavior of MDT chambers under massive irradiation of gammas and neutrons at level of S-LHC, three extensive tests were performed at the ENEA-Casaccia Research Centre Facilities, irradiating several test detectors. The results about the drift properties, gas gain and tracking performances, both at high rates and after massive irradiation, are given.

Drift properties of the ATLAS MDT chambers

A cosmic ray setup has been assembled, in order to verify that the BIS-MDT chamber fulfils the requirements of the ATLAS Muon Spectrometer. We use measurements obtained with this setup to study the drift time spectra of the MDT tubes and explain its features, by comparing them with the predictions of Garfield, Magboltz and Heed simulation programs. The drift time spectra have a peculiarity of a double peak. The second peak is a clear evidence of the Ramsauer dip of the electron cross-section.