Muon Drift Tube Chambers Research Articles

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%.

A 4-channel front-end electronics for muon drift tubes detectors in 65 nm CMOS technology

A 4-channel front-end electronics chip in 65 nm CMOS technology (ASD65 nm) for muon drift tube chambers at high background counting rates in the ATLAS detector at High-Luminosity LHC and in future high-energy collider experiments is presented. Each channel of the ASD65 nm chip is a mixed-signal processing circuit consisting of a Charge Sensitive Preamplifier (CSP), a two-stage shaper, and a timing discriminator. The CSP exhibits a peaking time of 11 ns and a sensitivity of 1.1 mV/fC. The peaking time of the full analog chain is 14.6 ns. The minimum signal-to-noise ratio of the channel is 15 dB for the minimum input charge of 5 fC, and it rises to 40.5 dB for the maximum input charge of 100 fC. At the output, the time representation of input signal is provided in both, CMOS level as well as low-voltage-differential-signal. Each channel consumes a current of 10.6 mA from a single 1.2 V supply, and occupies an area of 0.235 mm2. The specified performance parameters of the ASD65 nm have been achieved for 60 pF parasitic capacitance of the detector connected the input terminal.

Design, construction and test of small-diameter Muon Drift Tube chambers (sMDT) for the Phase-1 upgrade of the ATLAS muon spectrometer

The ATLAS muon spectrometer consists of an efficient muon trigger system and precision muon tracking chambers providing high momentum resolution up to the TeV scale. Yet, in the regions between the inner barrel and endcap of the muon spectrometer the trigger selectivity is limited. Furthermore, at the future High-Luminosity LHC the efficiency of the resistive plate trigger chambers (RPCs) will decrease due to ageing effects. Therefore, additional RPCs will be installed at the ends of the inner barrel layer of the muon spectrometer in the current long shutdown for the Phase-1 upgrade of the LHC in 2019 and 2020. In order to free space for them, the current Muon Drift Tube (MDT) chambers will be replaced by small-diameter Muon Drift Tube (sMDT) chambers with 15 instead of 30 mm tube diameter, which will be integrated with thin-gap RPCs. Due to their higher background rate capability, the new sMDT chambers are also suitable precision muon tracking detectors at future hadron colliders. An overview of the design and production of the new ATLAS sMDT chambers, their performance and their mechanical integration with the RPCs is given. The construction of these new chambers also serves as a pilot project for the replacement of half of the barrel inner layer in the Phase-2 upgrade of the ATLAS detector.

The new octal amplifier–shaper–discriminator chip for the ATLAS MDT chambers at HL-LHC

In order to fully exploit the physics potential of the ATLAS experiment at the HL-LHC, the trigger rate of and maximum latency of the first-level trigger system will be increased to 1 MHz and 10 μ s , respectively. In addition, a new first-level muon track trigger with high momentum resolution based on the ATLAS precision Muon Drift-Tube (MDT) chambers will be employed which requires triggerless readout. The TDC ASICs of the current front-end electronics of the MDT chambers are incompatible with these requirements. The front-end boards, each with a TDC chip and three 8-channel amplifier–shaper–discriminator (ASD) chips have to be replaced. Therefore, a new octal ASD2 ASIC has been developed in modern 130 nm IBM/Global Foundries CMOS technology. The chip also contains a Wilkinson ADC to perform both time-over-threshold and signal charge measurement. The ASD design has been fully qualified for the serial production of 80000 chips for ATLAS. The performance in terms of signal rise time and channel uniformity significantly surpasses the one of the previous chip while keeping the power consumption constant. In addition to the characterization with test pulses, several chips have been mounted on the front-end boards and tested in a muon beam at the Gamma Irradiation Facility GIF++ at CERN up to high counting rates where the superior drift time and spatial resolution becomes evident. • New Amplifier–Shaper–Discriminator chips for the readout of ATLAS (s)MDT chambers at HLLHC. • Design of new ASD chip in 130 nm CMOS IBM/Global Foundries technology completed. • Improved signal rise time and channel uniformity. • Radiation hardness far better than needed in the ATLAS muon spectrometer at HLLHC. • Successful full performance test in a muon beam at CERN under intense gamma irradiation.

The drift velocity monitoring system of the CMS barrel muon chambers

The drift velocity is a key parameter of drift chambers. Its value depends on several parameters: electric field, pressure, temperature, gas mixture, and contamination, for example, by ambient air. A dedicated Velocity Drift Chamber (VDC) with 1-L volume has been built at the III. Phys. Institute A, RWTH Aachen, in order to monitor the drift velocity of all CMS barrel muon Drift Tube chambers. A system of six VDCs was installed at CMS and has been running since January 2011. We present the VDC monitoring system, its principle of operation, and measurements performed.

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.

Operation of the ATLAS muon drift-tube chambers at high background rates and in magnetic fields

In the ATLAS muon spectrometer, large drift-tube chambers are used for precision tracking. The chambers will be operated at a high neutron and /spl gamma/ background resulting in count rates of up to 500 Hz cm/sup -2/ corresponding to 300 kHz per tube. The spatial resolution of the drift tubes is degraded from 82 /spl mu/m without background to 108 /spl mu/m at 500 Hz cm/sup -2/ background count rate. Due to afterpulsing in the Ar/CO/sub 2/ gas mixture used in the drift tubes, ionizing radiation causes more than one hit in a tube within the maximum drift time of about 800 ns which is expected for magnetic field strengths around 1.2 T. In order to limit the count rate, the drift tubes are read out with an artificial dead time of 790 ns which causes an efficiency loss of 23% at a rate of 300 kHz per tube. The space-to-drift-time relationship of the tubes varies with background rate, temperature, and magnetic field strength. The mean magnetic field strength in a muon chamber is 0.4 T on the average, but may vary by up to 0.4 T within a chamber. The space-to-drift-time relationship must therefore be determined in short time intervals with an accuracy better than 20 /spl mu/m using muon tracks and applying corrections for measured magnetic field variations.

Resolution and efficiency of the ATLAS muon drift-tube chambers at high background rates

The resolution and efficiency of a precision drift-tube chamber for the ATLAS muon spectrometer with final read-out electronics was tested at the Gamma Irradiation Facility at CERN in a 100GeV muon beam at photon irradiation rates of up to 990Hz/cm2, which corresponds to twice the highest background rate expected in ATLAS. A silicon strip detector telescope served as external reference in the beam. The pulse-height measurement of the read-out electronics was used to perform time-slewing corrections, which lead to an improvement of the average drift-tube resolution from 104 to 82μm without irradiation, and from 128 to 108μm at the maximum expected rate. The measured drift-tube efficiency agrees with the expectation from the dead time of the read-out electronics up to the maximum expected rate.

Resolution and efficiency of the ATLAS muon drift-tube chambers at high background rates

The resolution and efficiency of a precision drift-tube chamber for the ATLAS muon spectrometer with final read-out electronics was tested at the Gamma Irradiation Facility at CERN in a 100 GeV muon beam at photon irradiation rates of up to 990 Hz / cm 2 , which corresponds to twice the highest background rate expected in ATLAS. A silicon strip detector telescope served as external reference in the beam. The pulse-height measurement of the read-out electronics was used to perform time-slewing corrections, which lead to an improvement of the average drift-tube resolution from 104 to 82 μ m without irradiation, and from 128 to 108 μ m at the maximum expected rate. The measured drift-tube efficiency agrees with the expectation from the dead time of the read-out electronics up to the maximum expected rate.

The alignment system of the ATLAS muon spectrometer

The muon spectrometer of the ATLAS detector at the LHC has been designed to provide a good stand-alone momentum resolution for muons up to about 1 TeV. For this purpose, muon drift tube chambers with very high spatial resolution were developed; in addition, a precise online alignment monitoring system is required. This system is based on optical sensors measuring the individual deformations and the relative positions of muon chambers; temperature sensors are used to monitor their thermal expansion. In the endcap, the alignment system has to make use of additional alignment bars, used as precision reference rulers. In the year 2002, the ATLAS muon collaboration has installed a large-scale test setup of the muon spectrometer barrel and endcap in the H8 test beam line at CERN; one of its aims is to test the concepts and the final prototypes of the components of the alignment system before starting the mass production.

First system performance experience with the ATLAS high-precision muon drift tube chambers

Three prototype monitor drift tube chambers corresponding to a full-size ATLAS barrel tower have been tested in the cosmic ray test setup DATCHA at CERN. The event reconstruction is based on a procedure which allows to self-calibrate the distance–time relation with high precision by using tracks. Results on the alignment systems compared to the information from the reconstructed events are presented.