Drift Tube Chambers Research Articles

Precision muon tracking detectors for high-energy hadron colliders

Small-diameter muon drift tube (sMDT) chambers with 15mm tube diameter are a cost-effective technology for high-precision muon tracking over large areas at high background rates as expected at future high-energy hadron colliders including HL-LHC. The chamber design and construction procedures have been optimised for mass production and provide sense wire positioning accuracy of better than 10μm. The rate capability of the sMDT chambers has been extensively tested at the CERN Gamma Irradiation Facility. It exceeds the one of the ATLAS muon drift tube (MDT) chambers, which are operated at unprecedentedly high background rates of neutrons and γ-rays, by an order of magnitude, which is sufficient for almost the whole of the muon detector acceptance at FCC-hh at maximum luminosity. sMDT operational and construction experience exists from ATLAS muon spectrometer upgrades which are in progress or under preparation for LHC Phase 1 and 2.

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.

Development of a sub-nanosecond time-to-digital converter based on a field-programmable gate array

The present time-to-digital converter (TDC) chips for the monitored drift tube (MDT) chambers at the ATLAS experiment will be replaced with new ones for the High-Luminosity LHC, expected to begin operation in 2026. The design and the performance of a 24 channel TDC with a variable time binning of down to 0.28 nsec based on a Xilinx Kintex-7 field programmable gate array are reported. The time measurement is provided by a multisampling scheme with quad phase clocks synchronized with an external reference clock. The differential and integral nonlinearities have been measured to be less than half of the time binning. The temperature dependence on the performance is observed to be small. In conclusion the obtained performance of the time measurement is sufficiently high for the use with MDT chambers.

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.

Upgrades of the ATLAS muon spectrometer with sMDT chambers

With half the drift-tube diameter of the Monitored Drift Tube (MDT) chambers of the ATLAS muon spectrometer and otherwise unchanged operating parameters, small-diameter Muon Drift Tube (sMDT) chambers provide an order of magnitude higher rate capability and can be installed in detector regions where MDT chambers do not fit. The chamber assembly time has been reduced by a factor of seven to one working day and the sense wire positioning accuracy improved by a factor of two to better than ten microns. Two sMDT chambers have been installed in ATLAS in 2014 to improve the momentum resolution in the barrel part of the spectrometer. The construction of an additional twelve chambers covering the feet regions of the ATLAS detector has started. It will be followed by the replacement of the MDT chambers at the ends of the barrel inner layer by sMDTs improving the performance at the high expected background rates and providing space for additional RPC trigger chambers.

Characterization and Calibration of Large Area Resistive Strip Micromegas Detectors

Resistive strip Micromegas detectors have been tested extensively as small detectors of about 10×10cm2 in size and they work reliably at high rates of 100kHz/cm2 and above. Tracking resolution well below 100μm has been observed for 100GeV muons and pions. Micromegas detectors are meanwhile proposed as large area muon precision trackers of 2–3m2 in size. To investigate possible differences between small and large detectors, a 1m2 detector with 2048 resistive strips at a pitch of 450μm was studied in the LMU Cosmic Ray Measurement Facility (CRMF) using two 4×2.2m2 large Monitored Drift Tube (MDT) chambers for cosmic muon reference tracking. A segmentation of the resistive strip anode plane in 57.6mm×93mm large areas has been realized by the readout of 128 strips with one APV25 chip each and by eleven 93mm broad trigger scintillators placed along the readout strips. This allows for mapping of homogeneity in pulse height and efficiency, determination of signal propagation along the 1m long anode strips and calibration of the position of the anode strips.

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.

An analytical solution to the problem of linear track segment reconstruction in drift tube chambers

Drift tube chambers are used for high resolution position measurements of charged particles in high energy physics. In the case of track reconstruction in two dimensions, for given geometry of a calibrated drift tube chamber, its output can be translated to a collection of triples, each one containing the coordinates of the wire of the drift tube crossed by a particle and the distance of the closest approach of a particle to the wire. The distance of the closest approach defines a drift circle which has the center at the wire and the radius equal to the distance of the closest approach. To reconstruct a linear segment of a track, a common tangent must be found to drift circles associated with that single track. In the study it is shown that this problem can be solved analytically.

CMS RPC muon detector performance with 2010-2012 LHC data

The muon spectrometer of the CMS (Compact Muon Solenoid) experiment at the Large Hadron Collider (LHC) is equipped with a redundant system made of Resistive Plate Chambers (RPCs) and Drift Tube (DT) chambers in the barrel, RPC and Cathode Strip Chambers (CSCs) in the endcap region. In this paper, the operations and the performance of the RPC system during the first three years of LHC activity are presented. The stability of the RPC performance, in terms of efficiency, cluster size and noise, is also reported. Finally, the radiation background levels on the RPC system have been measured as a function of the LHC luminosity. Extrapolations to the High Luminosity LHC conditions are also discussed.

Performance of drift-tube detectors at high counting rates for high-luminosity LHC upgrades

The performance of pressurized drift-tube detectors at very high background rates has been studied at the Gamma Irradiation Facility (GIF) at CERN and in an intense 20MeV proton beam at the Munich Van-der-Graaf tandem accelerator for applications in large-area precision muon tracking at high-luminosity upgrades of the Large Hadron Collider (LHC). The ATLAS muon drift-tube (MDT) chambers with 30mm tube diameter have been designed to cope with γ and neutron background hit rates of up to 500Hz/cm2. Background rates of up to 14kHz/cm2 are expected at LHC upgrades. The test results with standard MDT readout electronics show that the reduction of the drift-tube diameter to 15mm, while leaving the operating parameters unchanged, vastly increases the rate capability well beyond the requirements. The development of new small-diameter muon drift-tube (sMDT) chambers for LHC upgrades is completed. Further improvements of tracking efficiency and spatial resolution at high counting rates will be achieved with upgraded readout electronics employing improved signal shaping for high counting rates.

Improvement of the L1 trigger for the ATLAS muon spectrometer at high luminosity

When the peak luminosity of 1034cm−2s−1 of the LHC will be increased by a factor of 5–7 in about a decade from now (“SLHC”), the selectivity of the ATLAS Level-1 (L1) triggering system will have to be improved in order to cope with the maximum allowed trigger rate of about 100kHz. For the L1 trigger of the ATLAS Muon Spectrometer this calls for an increase of the pT-threshold for single muons. In the present L1 muon trigger system, however, the effective pT-threshold is not very sharp due to the limited spatial resolution of the trigger chambers, resulting in a majority of L1 triggers from muons below threshold. We describe a new, high-speed readout system of the Monitored Drift Tube chambers, which allows to supply the precision coordinates of the candidate muon to the L1 trigger, resulting in an accurate momentum determination, a sharpened pT-threshold and an efficient rejection of unwanted L1 triggers from low-pT muons.

Construction and test of a full prototype drift-tube chamber for the upgrade of the ATLAS muon spectrometer at high LHC luminosities

For the planned high-luminosity upgrades of the Large Hadron Collider (LHC) background rates of neutrons and gamma rays of up to 14kHz/cm2 are expected which exceed the rate capability of the current ATLAS precision muon tracking detectors, the Monitored Drift Tube (MDT) chambers, with a drift tube diameter of 30mm. Smaller diameter drift tube (sMDT) chambers with 15mm tube diameter have been developed for upgrades of the ATLAS muon spectrometer. A full sMDT prototype chamber has been constructed and tested in a muon beam at CERN and with cosmic muons at high background irradiation rates of up to 95kHz/cm2 and 1400kHz/tube. The test results demonstrate the required track reconstruction efficiency and spatial resolution of the sMDT chambers at background rates well beyond the maximum expected values at high-luminosity LHC. The sense wire locations in the prototype chamber have been measured with few microns precision with cosmic rays using precise reference chambers confirming the required wire positioning accuracy of better than the 20μm.

Construction and Test of a Prototype Chamber for the Upgrade of the ATLAS Muon Spectrometer

Abstract Monitored drift tube chambers are used as precision tracking detectors in the muon spectrometer of the ATLAS experiment at the LHC at CERN. These chambers provide a spatial resolution of 35 μm and a tracking efficiency of close to 100% up to background rates of 0.5 kHz/cm 2 , the former being limited at higher rates mainly due to space-charge effects and the latter due to the maximum drift time of 700 ns. For LHC upgrades, a faster drift tube chamber has been developed, using drift tubes with a diameter of 15 mm instead of 30 mm. The increased channel density and shorter drift time of about 200 ns raise the rate capability to about 10 kHz/cm 2 , while retaining the spatial resolution. A prototype chamber with trapezoidal shape consisting of 2 x 8 layers of 15 mm diameter drift tubes with an active surface of 0.8 m 2 has been constructed. The prototype chamber has been tested at CERN with a 180 GeV muon beam at a SPS beam line and with cosmic ray muons at the Gamma Irradiation Facility (GIF) at high γ radiation rates.

Calibration and Performance of the Precision Chambers of the ATLAS Muon Spectrometer

The ATLAS muon spectrometer consists of a system of precision tracking and trigger chambers embedded in a 2T magnetic field generated by three large aircore superconducting toroids. The precision Monitored Drift Tube (MDT) chambers measure the track sagitta up to a pseudorapidity of 2.7 with a 50 μm uncertainty yielding a design muon transverse momentum resolution of 10% at 1 TeV. Muon tracking is augmented in the very forward region by Cathode Strip Chambers (CSC). The calibration program, essential to achieve the spectrometer design performance and physics reach, is conducted at three worldwide computing centers. These centers each receive a dedicated High Level Trigger data stream that enables high statistics based determination of t 0 and drifttime to driftspace relations. During the first year of data taking a system of periodic calibration updates has been established. The calibration algorithms, methods and tools and performance results using LHC collision data are discussed.

Tracking and Level-1 triggering in the forward region of the ATLAS Muon Spectrometer at sLHC

In the endcap region of the ATLAS Muon Spectrometer (η > 1) precision trackingand Level-1 triggering are performed by different types of chambers. Monitored Drift Tube chambers(MDT) and Cathode Strip Chambers (CSC) are used for precision tracking, while Thin Gap Chambers(TGC) form the Level-1 muon trigger, selecting muons with high transverse momentum (pT).When by 2018 the LHC peak luminosity of 1034 cm−2s−1 will be increased by a factorof ∼ 2 and by another factor of ∼ 2–2.5 in about a decade from now (``SLHC''), animprovement of both systems, precision tracking and Level-1 triggering, will become mandatory inorder to cope with the high rate of uncorrelated background hits (``cavern background'') and to staybelow the maximum trigger rate for the muon system, which is in the range of 10–20 % of the 100kHz rate, allowed for ATLAS. For the Level-1 trigger of the ATLAS Muon Spectrometer this means a stronger suppression ofsub-threshold muons in the high-pT trigger as well as a better rejection of tracks not comingfrom the primary interaction point. Both requirements, however, can only be fulfilled ifspatial resolution and angular pointing accuracy of the trigger chambers, in particular of those inthe Inner Station of the endcap, are improved by a large factor. This calls for a completereplacement of the currrently used TGC chambers by a new type of trigger chambers with betterperformance. In parallel, the precision tracking chambers must be replaced by chambers with higherrate capability to be able to cope with the intense cavern background.In this article we present concepts to decisively improve the Level-1 trigger with newly developedtrigger chambers, being characterized by excellent spatial resolution, good time resolution andsufficiently short latency. We also present new types of precision chambers, designed tomaintain excellent tracking efficiency and spatial resolution in the presence of high levels ofuncorrelated background hits, as generated by γ and neutron conversions.

Design studies of the ATLAS muon Level-1 trigger based on the MDT detector for the LHC upgrade

The present muon Level-1 trigger of the ATLAS detector is given by dedicated detectors; RPC and TGC chambers in barrel and end-cap regions, respectively. The Monitored Drift Tube (MDT) chambers and the Cathode-Strip Chambers (CSC) are used for precision measurements of muon tracks. The performance of the muon Level-1 trigger is limited by the momentum resolution of the trigger chambers. In order to improve the trigger performance, a muon track finding scheme based on MDT signals is envisaged. Studies of the scheme and the algorithm are presented. The trigger latency is estimated to be approximately 3 μs.

Upgrade of the ATLAS Muon Trigger for the SLHC

The outer shell of the ATLAS experiment at the LHC consists of a system of toroidal air-core magnets in order to allow for the precise measurement of the transverse momentum (pT) of muons, which in many physics channels are a signature of interesting physics processes [1,2]. For the precise determination of the muon momentum Monitored Drift Tube chambers (MDT) with high position accuracy are used, while for the fast identification of muon tracks chambers with high time resolution are used, able to select muons above a predefined pT threshold for use in the first Level of the ATLAS triggering system (Level-1 trigger). When the LHC peak luminosity of 1034 cm−2s−1 will be increased by a factor of 4–5 in about a decade from now (''SLHC''), an improvement of the selectivity of the ATLAS Level-1 triggering system will be mandatory in order to cope with the maximum allowed trigger rate of 100 kHz. For the Level-1 trigger of the ATLAS muon spectrometer this means an increase of the pT threshold for single muons. Due to the limited spatial resolution of the trigger chambers, however, the selectivity for tracks above ∼ 20 GeV/c is insufficient for an effective reduction of the Level-1 rate. We describe how the track coordinates measured in the MDT precision chambers can be used to decisively improve the selectivity for high momentum tracks. The resulting increase in latency will also be discussed.

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.

A data-driven performance evaluation method for CMS RPC trigger through CMS muon trigger

Abstract The muon system of the CMS (Compact Muon Solenoid) experiment at the LHC (Large Hadron Collider, Geneva-CH) consists of three gaseous detectors with complementary features: the Drift Tube Chambers (DT) in the barrel and the Cathode Strips Chambers (CSC) in the forward region provide good spatial resolution while the Resistive Plate Chambers (RPC), in both barrel and forward region, have an excellent time resolution. The measurements of these detectors are employed for triggering on muons in the hardware-based Level-1 trigger stage. In such scenario an algorithm has been developed, the Global Muon Trigger (GMT), which is in charge of collecting and merging the information provided by the three detectors and outputs muon trigger candidates (GMT candidates). The GMT candidates are henceforth transmitted to the L1 Global Trigger Logic which performs the final decision of accepting or rejecting the muon candidates. The GMT algorithm allows to trace back the detectors whose measurements have been used for each GMT candidate: such feature has been exploited in developing a method for the performance evaluation of muon trigger provided by the RPC system.

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.