ATLAS Monitored Drift Tube Research Articles

Development and test of a mini-Data Acquisition system for the High-Luminosity LHC upgrade of the ATLAS Monitored Drift Tube detector

New front-end electronics including ASICs and FPGA boards are under development for the ATLAS Monitored Drift Tube (MDT) detector to handle the large data rates and harsh environment expected in high luminosity LHC regime. A mobile Data Acquisition (miniDAQ) system is designed to perform integration tests of these front-end electronics. In addition, it will be used for surface commissioning of 96 small-radius MDT (sMDT) chambers and for integration and commissioning of new front-end electronics on the present ATLAS MDT chambers. Details of the miniDAQ hardware and firmware are described in this article. The system has been validated with cosmic muons using an sMDT prototype chamber and the new front-end electronics.

Time-Variant Front-End Read-Out Electronics for High-Data-Rate Detectors

The foreseen incremental luminosity for near-future high-energy physics experiments demands evolution for the read-out electronics in terms of event data-rate. However, the filtering necessary to reject noise and meet the signal-to-noise-ratio requirements imposes a restriction on the operational speed of the conventional read-out electronics. The stringent trade-off between signal-to-noise-ratio and the event data-rate originates from the time-invariant behavior of the conventional systems. In this paper, the cases of time-variant systems are addressed, studying a benchmark with the RC-CR shaping function used in time-over-threshold methods. It was demonstrated that the time-variant systems enable a higher data-rate for the given noise performance. Moreover, taking advantage of time-variant systems, the proposed rising-edge method enables further data-rate enhancement with respect to the traditional time-over-threshold technique by reading the data from the rising edge of the analog output waveform. A comparison between the conventional time-invariant time-over-threshold technique, its time-variant equivalent and rising-edge method confirms the better performance of the latter one in terms of data-rate enhancement for a target noise performance. Moreover, design challenges for time-variant systems are briefly discussed, considering the ATLAS Monitored Drift Tube detector as a design case.

Design of a Time-to-Digital Converter ASIC and a mini-DAQ system for the Phase-2 upgrade of the ATLAS Monitored Drift Tube detector

We present the second prototype of a time-to-digital (TDC) ASIC for the upgrade of the ATLAS Monitored Drift Tube (MDT) detector for High-Luminosity LHC operations. Compared to the first prototype, triple modular redundancy has been implemented for the configuration and flow control logic. The total power consumption is increased by less than 10 mW while achieving the same time resolution and channel uniformity. A mini-DAQ system has been built to verify the front-end electronics chain with the new prototype together with other ASICs and boards in triggered mode. Cosmic ray tests with a small-diameter MDT chamber indicate that the configuration and data transmission of the readout electronics perform well. It is expected that this prototype design will be used in the final production.

Design and performance of a TDC ASIC for the upgrade of the ATLAS Monitored Drift Tube detector

We present the prototype of a time-to-digital (TDC) ASIC for the upgrade of the ATLAS Monitored Drift Tube (MDT) detector for high-luminosity LHC operation. This ASIC is based on a previously submitted demonstrator ASIC designed for timing performance evaluation, and includes all features necessary for the various operation modes, as well as the migration to the TSMC 130 nm CMOS technology. We present the TDC design with the emphasis on added features and performance optimization. Tests of the timing performance demonstrate that this ASIC meets the design specifications. The TDC has a bin size of about 780 ps, and a timing bin variations within 40 ps for all 24 channels with leading and trailing edge digitization, while the power consumption has been limited to 250 mW, corresponding to a consumption of about 5.2 mW per edge measurement.

Development of a time-to-digital converter ASIC for the upgrade of the ATLAS Monitored Drift Tube detector

The upgrade of the ATLAS muon spectrometer for the high-luminosity LHC requires new trigger and readout electronics for various elements of the detector. We present the design of a time-to-digital converter (TDC) ASIC prototype for the ATLAS Monitored Drift Tube (MDT) detector. The chip was fabricated in a GlobalFoundries 130 nm CMOS technology. Studies indicate that its timing and power dissipation characteristics meet the design specifications, with a timing bin variation of ±40 ps for all 48 TDC slices and a power dissipation of about 6.5 mW per slice.

Calibration of large area Micromegas detectors using cosmic rays

Currently m2-sized micropattern detectors with spatial resolution better than 100 μm and online trigger capability are of big interest for many experiments. Large size in combination with superb spatial resolution and trigger capability implicates that the construction of these detectors is highly sophisticated and imposes strict mechanical tolerances. We developed a method to survey assembled and working detectors on potential deviations of the micro pattern readout structures from design value as well as deformations of the whole detector, using cosmic muons in a tracking facility. The LMU Cosmic Ray Facility consists of two 8 m2 ATLAS Monitored Drift Tube chambers (MDT) for precision muon reference tracking and two segmented trigger hodoscopes with sub-ns time-resolution and additional 10 cm position information along the wires of the MDTs. It provides information on homogeneity in efficiency and pulse height of one or several micropattern detectors installed in between the MDTs. With an angular acceptance of −30° to +30° the comparison of the reference muon tracking with centroidal position determination or time projection chamber like track reconstruction in the micropattern detector allows for calibration in three dimensions. We present results of a m2-sized one-dimensional resistive strip Micromegas detector consisting of two readout boards with in total 2048 strips, read out by 16 APV25 front-end boards. This 16-fold segmentation along the precision direction in combination with a 10-fold segmentation in orthogonal direction by the resolution of the trigger hodoscope, allows for very detailed analysis of the 1 m2 detector under study by subdivision into 160 partitions, each being analyzed separately. We are able to disentangle deviations from the readout strip straightness and global deformation due to the small overpressure caused by the Ar:CO2 (93:7) gas mixture flux. We introduce the alignment and calibration procedure, report on homogeneity in efficiency and pulse height and present results on deformation and performance of the m2-sized Micromegas.

Use of Triple Modular Redundancy (TMR) technology in FPGAs for the reduction of faults due to radiation in the readout of the ATLAS Monitored Drift Tube (MDT) chambers

The Triple Modular Redundancy (TMR) technology allows protection of the functionality of FPGAs against single event upsets (SEUs). Each logic block is implemented three times with a 2-out-of-3 voter at the output. Thus, the correct logical value is available even if there is an upset bit in one location. We applied TMR to the configuration code of a Virtex-II-2000 FPGA, which serves as the on-chamber readout processor of the ATLAS monitored drift tubes (MDTs). We describe the code implementation, results of performance measurements and discuss several limitations of the method. Finally, we present a supplementary technology called ``scrubbing''. It permanently checks the configuration memory while the FPGA is operating, and corrects upset configuration bits when necessary.

Development of fast high-resolution muon drift-tube detectors for high counting rates

Pressurized drift-tube chambers are efficient detectors for high-precision tracking over large areas. The Monitored Drift-Tube (MDT) chambers of the muon spectrometer of the ATLAS detector at the Large Hadron Collider (LHC) reach a spatial resolution of 35 μ m and almost 100% tracking efficiency with 6 layers of 30 mm diameter drift tubes operated with an Ar:CO 2 (93:7) gas mixture at 3 bar and a gas gain of 20 000. The ATLAS MDT chambers are designed to cope with background counting rates due to neutrons and γ rays of up to about 300 kHz per tube which will be exceeded for LHC luminosities larger than the design value of 10 34 cm −1 s −1. Decreasing the drift-tube diameter to 15 mm while keeping the other parameters, including the gas gain, unchanged reduces the maximum drift time from about 700 to 200 ns and the drift-tube occupancy by a factor of 7. New drift-tube chambers for the endcap regions of the ATLAS muon spectrometer have been designed. A prototype chamber consisting of 12 times 8 layers of 15 mm diameter drift tubes of 1 m length has been constructed with a sense wire positioning accuracy of 20 μ m . The 15 mm diameter drift-tubes have been tested with cosmic rays in the Gamma Irradiation Facility at CERN at γ counting rates of up to 1.85 MHz.

ATLAS monitored drift tube chambers for super-LHC

After the high-luminosity upgrade of the Large Hadron Collider (LHC), the ATLAS muon spectrometer is expected to work at 10-fold background rates of gammas and neutrons. As the momentum resolution of the spectrometer is expected to be 10% a single tube resolution of the muon drift tubes of 80μm is required. At background rates around 1000Hz/cm 2 space charge effects will lead in the slow and non-linear AR:CO2=93:7 gas mixture degrade the drift-tube spatial resolution. While this was studied for gammas and low energetic neutrons, almost no information exists for fast neutrons.This paper shows that:•11MeV neutrons at flux densities of 4 and 16kHz/cm2 degrade the position resolution by only 10μm at a detection efficiency of 4×10−4.•two modified inert gas mixtures selected by fastness and linearity of their position-drifttime ( r–t) relation show similar resolution as the standard gas in agreement with Garfield simulations.•the resolution of newly developed 15mm ∅ drift tubes are mostly unaffected by space charge effects due to gamma irradiation up to 1400Hz/cm2 according to Garfield simulations.

ATLAS Muon Drift Tube Electronics

This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60 μm, which corresponds to a momentum accuracy of about 10% at pT= 1 TeV. The design and performance of the MDT readout electronics as well as the electronics for controlling, monitoring and powering the detector will be discussed. These electronics have been extensively tested under simulated running conditions and have undergone radiation testing certifying them for more than 10 years of LHC operation. They are now installed on the ATLAS detector and are operating during cosmic ray commissioning runs.

Database architecture for the calibration of ATLAS monitored drift tube chambers

The size and complexity of LHC experiments raise unprecedented challenges not only in terms of detector design, construction and operation, but also in terms of software models and data persistency. One of the more challenging tasks is the calibration of the 375000 Monitored Drift Tubes, that will be used as precision tracking detectors in the Muon Spectrometer of the ATLAS experiment. A high rate of muon tracks is needed to reach the design average resolution of 80 microns. In this context, data suitable for MDT calibration will be extracted from the second level trigger and then streamed to three remote Tier-2 Calibration Centers. The Calibration sites will also need the ATLAS conditions data that are relevant for the calculation of MDT calibrations: either the appropriate tables of the Conditions Database will be replicated at the remote sites via ORACLE streams, or the remote sites will directly access these tables from the nearest Tier-1. At each centre, the computation of the actual calibration constants will be performed in several steps, including strict validation and data quality checks. All information produced at every stage of the calibration procedure will be stored in local ORACLE Calibration databases that will be replicated to a central database located at CERN using ORACLE streams: this will allow each Calibration site to access the data produced by the others and to eventually provide back-up should one site become unavailable for any reason. The validated calibration constants will be extracted from the CERN Calibration DB and stored into the ATLAS Conditions database for subsequent use in reconstruction and data analysis. This paper reviews the complex chain of databases envisaged to support the MDT Calibration and describes the actual status of the implementation and the tests that are being performed to ensure a smooth operation at the LHC start-up at the end of this year.

Database architecture for the calibration of ATLAS Monitored Drift Tube Chambers

Database architecture for the calibration of ATLAS Monitored Drift Tube Chambers

Drift time spectrum and gas monitoring in the ATLAS Muon Spectrometer precision chambers

The ATLAS Muon Spectrometer incorporates 354 000 drift tubes assembled into 1200 Monitored Drift Tube (MDT) precision chambers, with a total gas volume of 723 m 3 . This MDT gas, Ar 93% and CO 2 7% at 3 bar, is cycled through the spectrometer at a rate of one total detector volume per day. Achieving the 80 μ m drift tube design resolution requires stringent gas quality control as a fundamental component of the MDT calibration program. We report on the design, deployment and performance of a dedicated MDT mini-chamber conceived for continuous monitoring and drift time calibration of the ATLAS MDT operating gas. This chamber enables measurement of the drift spectra from which gas properties relevant to MDT calibrations and stable operating conditions are determined. Located in the ATLAS gas facility at CERN, the mini-chamber produces hourly drift spectra which are automatically analyzed. Results are published online and disseminated to the ATLAS muon system conditions and calibration databases in real time.

ATLAS MDT chamber behaviour after neutron irradiation and in a high rate background

Many of the physics processes of interest at the Large Hadron Collider (LHC) will involve muon production in the final state. The Monitored Drift Tube (MDT) chambers, the precision tracking elements of the ATLAS muon spectrometer, are the main tools for the muon identification and measurement. They will operate in the harsh LHC background environment, mainly due to low energy photons and neutrons which will dominate the counting rate in most areas of the spectrometer, where an overall maximum counting rate of 500 Hz / cm 2 is expected. The upgrade to Super-LHC will involve fluxes ten times higher. To study the behaviour of MDT chambers under massive neutron irradiation at the level of Super-LHC, a test was performed at the “Tapiro” Neutron Facility of the ENEA “La Casaccia” Research Center.

Conditions database and calibration software framework for ATLAS monitored drift tube chambers

The size and complexity of LHC experiments raise unprecedented challenges not only in terms of detector design, construction and operation, but also in terms of software models and data persistency. One of the most challenging tasks is the calibration of the 375,000 Monitored Drift Tubes (MDTs) that will be used as precision tracking detectors in the Muon Spectrometer of the ATLAS experiment. This paper reviews the status of the MDT Calibration software and computing model. In particular, the options for a dedicated database are described.

ATLAS MDT neutron sensitivity measurement and modeling

The sensitivity of the ATLAS precision muon detector element, the Monitored Drift Tube (MDT), to fast neutrons has been measured using a 5.5MeV Van de Graaff accelerator. The major mechanism of neutron-induced signals in the drift tubes is the elastic collisions between the neutrons and the gas nuclei. The recoil nuclei lose kinetic energy in the gas and produce the signals. By measuring the ATLAS drift tube neutron-induced signal rate and the total neutron flux, the MDT neutron signal sensitivities were determined for different drift gas mixtures and for different neutron beam energies. We also developed a sophisticated simulation model to calculate the neutron-induced signal rate and signal spectrum for ATLAS MDT operation configurations. The calculations agree with the measurements very well. This model can be used to calculate the neutron sensitivities for different gaseous detectors and for neutron energies above those available to this experiment.

ATLAS monitored drift tube assembly and test at IHEP (Protvino)

Abstract The Monitored Drift Tube is the basic element of the muon spectrometer of ATLAS detector at LHC. More than 14 000 such tubes have been assembled and tested at IHEP (Protvino) in framework of construction of end-cap drift chambers for the spectrometer. This paper reports some details of assembling techniques and quality control and assurance test results.