Sense Wire Research Articles

Construction and performance of the precision tracking chambers for the ATLAS muon spectrometer upgrade for high-luminosity LHC

For the operation at the High-Luminosity (HL) LHC, the Monitored Drift Tube (MDT) chambers of the inner barrel layer (BIS) of the ATLAS muon spectrometer will be replaced by small-diameter Muon Drift Tube (sMDT) chambers which will be integrated with triplets of thin-gap Resistive Plate Chambers (RPC) in order to improve the acceptance and robustness of the barrel muon trigger system. The sMDT chambers have half the drift tube diameter of the MDT chambers and about one order of magnitude higher background rate capability. The construction of the 96 new sMDT chambers was performed between January 2021 and September 2023 at two production sites at a continuous rate of one chamber every two weeks. The sense wire positioning accuracy guaranteed by precision assembly jigs was measured to be around 5μm over the whole construction period. Stringent performance tests had to be passed during the production which have been successfully repeated after delivery of the chambers to CERN. The chambers have been tested with the new MDT front-end ASICs developed for operation at HL-LHC which improve the spatial resolution of the drift tubes by 10% compared to readout with the legacy electronics.

A variable gain front-end electronics for drift chambers

The cluster counting/timing technique in a drift chamber allows to have a bias free impact parameter estimate. The application of this technique requires to measuring and counting the arrival times of each individual ionization cluster to a sense wire. In a Helium based gas mixture the rise time of the signal from a cluster is approximately 1 ns, therefore a readout electronic front-end with high linearity, low distortion and sufficiently high bandwidth is required. Furthermore, it would be useful for the readout electronics to be able to easily adapt its gain to the detector’s operating point. The use of a variable gain amplifier (VGA) allows to meet the needs arising from the changed operating conditions of the detector. The market offers components capable of satisfying all these needs with dimensions compatible with high-density drift chambers. A high linear, low distortion, remotely controllable, about 1GHz bandwidth and compact VGA is presented together with the measurements performed.

A [formula omitted] drift velocity monitoring chamber for the MEG II experiment

The MEG-II experiment searches for the lepton-flavor-violating decay: μ⟶e+γ. The reconstruction of the positron trajectory uses a drift chamber operated with a mixture of He and iC4H10 gas. It is crucial to provide a stable performance of the detector in terms of its electron transport parameters, avalanche multiplication, composition and purity of the gas mixture. In order to have a continuous monitoring of the quality of the gas injected, we plan to install a small drift chamber, with a simple geometry that allows to measure very precisely the electron drift velocity in a prompt way. The chamber is a small box with cathode walls, that determine a highly uniform electric field inside two adjacent drift cells. Along the axis separating the two drift cells, four staggered sense wires alternated with five guard wires collect the drifting electrons. The trigger is provided by two 90Sr radioactive sources placed on top of a two thin scintillator tiles telescope. The whole system is designed to give a response in few minutes about drift velocity variations at the 10−3 level. In this paper the development of the drift chamber is presented, with a particular focus on the details of its construction.

Implementation of the Cluster Counting and Timing technique on FPGA for the reduction of transferred data and stored information

Ultra-low mass and high granularity Drift Chambers fulfill the requirements of tracking systems for modern High Energy Physics experiments at future high luminosity accelerators (FCC or CEPC). The application of the Cluster Counting/Timing (CCT) technique adds a valuable particle identification capabilities with resolutions outperforming the traditional dE/dx technique. By measuring the arrival times of each individual ionization electron to the sense wire and by using suitable statistical tools it is possible to perform a bias free estimate of the impact parameter and a precise particle identification in drift chamber operating in a Helium based gas mixtures. The CCT technique consisting in identifying pulses due to different ionization electrons and in associating them in clusters according to their relative time delays, therefore it is necessary to have read-out interfaces capable of processing such high speed signals. This requires a data acquisition chain, able to manage the low amplitude signals from the sense wires (a ∼few mV) with a high bandwidth (∼1 GHz). Requirements on the drift chamber performance impose analog-to-digital conversions by a fast ADC at sample rates of at least 2 GS/s with 14-bit resolution. These constraints, together with maximum drift times and many readout channels, impose some sizeable data reduction strategy, while preserving all relevant information. Measuring both the amplitude and the arrival time of each peak in the signal associated to each ionization electron is the minimum requirement on the data transfer for storage to prevent any data loss. An electronic board including a Fast ADC and an FPGA for real-time processing of drift chamber signals is presented. The implementation of different algorithms for peaks finding are compared.

Analysis and study of the problems on the wires used in the MEG CDCH and the construction of the new drift chamber

In the MEG II detector, the measurement of the momentum of the charged particle is performed by a high transparency single volume, full stereo cylindrical Drift Chamber (CDCH). It is composed by 9 concentric layers, each consisting of 192 drift cells. The single drift cell is approximately squared, with a 20 μm gold plate tungsten sense wire surrounded by 40 μm/50 μm silver plated aluminum field wires in a ratio of 5:1. During the construction of the first CDCH, we observed the breaking of about hundred cathode wires: 97 of these were 40 μm aluminum wires, while 10 were 50 μm wires. Since the number of broken cathodes is less than 1% of the total, one can expect the influence on the track reconstruction efficiency to be not so dramatic. We verified by means of simulations that the loss of one cathode does not change the cell electric field appreciably. Here we present the results of the analysis of the effects of mechanical stress and chemical corrosion observed on these broken wires. Finally, we show the studies carried out on new wires to overcome the weaknesses found and the process that will be used for the construction of the new drift chamber (CDCH2). It will be built with the same modular technique, as for the previous one, the use of the wiring robot will be optimized to improve some weaker step in the procedure, new wires will be adopted with a 25% thicker diameter, which has very little effects on the resolution and efficiency of the detector. Furthermore these wires are made with a manufacturing process different from that used previously.

The measuring systems of the wire tension for the MEG II Drift Chamber by means of the resonant frequency technique

The ultra-low mass cylindrical drift chamber designed for the MEG II experiment is a challenging apparatus made of 1728 ϕ=20μm gold plated tungsten sense wires, 7680 ϕ=40μm and 2496 ϕ=50μm silver plated aluminium field wires. Because of electrostatic stability requirements all the wires have to be stretched at mechanical tensions of ∼25, ∼19 and ∼29g respectively which must be controlled at a level better than 0.5g. This chamber is presently in acquisition, but during its construction ∼100 field wires broke, because of chemical corrosion induced by the atmospheric humidity.On the basis of the experience gained with this chamber we decided to build a new one, equipped with a different type of wires less sensitive to corrosion. The choice of the new wire required a deep inspection of its characteristics and one of the main tools for doing this is a system for measuring the wire tension by means of the resonant frequency technique, which is described in this paper. The system forces the wires to oscillate by applying a sinusoidal signal at a known frequency, and then measures the variation of the capacitance between a wire and a common ground plane as a function of the external signal frequency. We present the details of the measuring system and the results obtained by scanning the mechanical tensions of two samples of MEG II cylindrical drift chamber wires and discuss the possible improvements of the experimental apparatus and of the measuring technique.

Flexible and Modular Fully Metallic Housing Concept for Solid Oxide Fuel Cells

The state-of-the-art alumina oxide housings used in single cell test rigs are fragile, inflexible and expensive. They are designed for a specific cell geometry, a change of the cell type - changing the cell thickness - or a change in the cell size is not intended and is thus associated with an immense expenditure of effort and time. In detail, the state-of-the-art ceramic frame concept is vulnerable to a fracturing of the frame or an insufficient contacting of the cell if a change in the cell thickness occurs. The connection of the ceramic housing with the typically metallic tubing of the gas supply is fragile, prone to develop leakages and is time consuming to replace and thereby prevents a change of the cell size. Gold wire seals used at the cathode side are a common source of leakage. Furthermore, the whole ceramic housing is sensitive to fracturing due thermal or load induced stress, and thus prevents fast thermal cycling of the specimen.This paper presents a modular, fully metallic housing concept which enables a fast and easy change of the cell size due to the utilization of a baseplate and a robustness towards different cell thicknesses due to the usage of a flexible metallic frame. The utilization of metal instead of alumina oxide reduces the manufacturing costs. Furthermore, an additional sealing on the cathode side enables a separation of the contacting pressure via a pneumatic piston from the sealing pressure applied via metallic screws. The force of the sealing pressure is not applied onto the cell and is thereby limited by the material constraints and not by the mechanical stability of the cell. For accurate voltage measurements, sense wires are separated from the current collection and are electrically isolated from the metallic housing. Thermocouples are used to measure the temperature distribution inside the anodic part of the housing, as close as possible to the cell. The chromium evaporation of the cathode part of the housing is reduced by a protective coating and the utilization of double layered tubes. In the end, the results of preliminary tests are presented.

Flexible and Modular Fully Metallic Housing Concept for Solid Oxide Fuel Cells

This paper presents a modular, fully metallic housing concept that enables a fast change of the cell size due to the utilization of a baseplate. Metal instead of alumina oxide is used to reduce the manufacturing costs. Two different variations are presented, one utilizing a gold seal and a second concept based on a flexible metallic frame. The latter is designed to separate the contacting pressure via a pneumatic piston from the sealing pressure applied via metallic screws. For accurate voltage measurements, sense wires are separated from the current collection and are electrically isolated from the metallic housing. Thermocouples are used to measure the temperature distribution inside the anode part of the housing, as close as possible to the cell, as well as the inlet and outlet gas temperatures. The chromium evaporation of the cathode part of the housing is reduced by a protective coating.

In-situ and in-operando analysis of voltage losses using sense wires for proton exchange membrane water electrolyzers

Proton exchange membrane water electrolyzer development requires understanding processes at the materials and interface levels to reach the required performance and lifetime targets for increasing market penetration. To achieve the required progress, it is critical to develop advanced in-situ diagnostics that allow observation of the changes that come with the reduction of catalyst loading combined with long-term intermittent operation. This work presents an internal voltage sensing method that enables observing internal voltage drops in an operating electrolyzer cell. It allows the total cell resistance to be separated into anode, CCM, and cathode resistance. The method is demonstrated by operating cells with different anode porous transport layers (PTLs). The changing properties of the PTLs result in significant variations of the resistances. Enhancing the PTL properties with a protective coating reduces the anode resistance significantly. In addition to these observations, the method enables a real-time monitoring of resistance related values that impact performance in water electrolyzers. Long-term experiments with the method allow us to gain insights into processes that occur during operation such as conditioning or degradation. The internal voltage sensing method presented in this study is a novel technique for diagnosing, analyzing, and optimizing water electrolyzers and other energy conversion devices.

A 10−3 drift velocity monitoring chamber

The MEG-II experiment searches for the lepton-flavor-violating decay: μ⟶ e+γ . The reconstruction of the positron trajectory uses a cylindrical drift chamber operated with a mixture of He and iC4H10 gas. It is important to provide a stable performance of the detector in terms of its electron transport parameters, avalanche multiplication, composition and purity of the gas mixture. In order to have a continuous monitoring of the quality of gas, we plan to install a small drift chamber, with a simple geometry that allows to measure very precisely the electron drift velocity in a prompt way. This monitoring chamber will be supplied with gas coming from the inlet and the outlet of the detector to determine if gas contaminations originate inside the main chamber or in the gas supply system. The chamber is a small box with cathode walls, that determine a highly uniform electric field inside two adjacent drift cells. Along the axis separating the two drift cells, four staggered sense wires alternated with five guard wires collect the drifting electrons. The trigger is provided by two 90Sr weak calibration radioactive sources placed on top of a two thin scintillator tiles telescope. The whole system is designed to give a prompt response (within a minute) about drift velocity variations at the 10−3 level.

The ultra light Drift Chamber of the MEG II experiment

The MEG experiment at the Paul Scherrer Institute searches for the charged Lepton Flavor Violating μ+→e+γ decay. MEG has already determined in a first data taking phase the world best upper limit on the branching ratio: BR(μ+→e+γ)<4.2×10−13 An upgrade of the whole detector has been approved to obtain a substantial increase in sensitivity. Currently MEG is in upgrade phases, this phase involves all the detectors. The new positron tracker is a high transparency single volume, fully stereo cylindrical Drift Chamber (CDCH), immersed in a non uniform longitudinal B-field, with length of 1.93 m, internal radius of 17 cm and external radius of 30 cm. It is composed of 9 concentric layers, divided into 12 identical sector of 16 drift cells. The single drift cell is approximately square, with a 20 μm gold plated W sense wire surrounded by 40 μm silver plated Al field wires in a ratio of 5:1. The total number of wires amounts to 11904 for an equivalent radiation length per track turn of about 1.5x10−3 X0 when the chamber is filled with a gas mixture of helium and iso-butane. Due to the high wire density (12wires∕cm2), the use of the classical feed-through technique as wire anchoring system could hardly be implemented and therefore it was necessary to develop new wiring strategies. The number of wires and the stringent requirements impose the use of an automatic system (wiring robot) to operate the wiring procedures. Several tests have been performed in different prototypes of the drift chamber, exposed to cosmic rays, test beams and radioactive sources, to fulfill the requirement on the spatial resolution to be less than 110 μm. In this paper we describe the CDCH construction and the first tests during the 2018 Engineering Run.

Towards new front-end electronics for the HADES drift chamber system

Operating HADES at the future FAIR SIS-100 accelerator challenges the rate capability of DAQ and electronics. A new, more robust version of front-end electronics needs to be built for the HADES drift chamber system. Due to the unavailability of the previously used ASD-8 analog read-out ASIC, PASTTREC (PANDA straw tube read-out ASIC) was tested as an ASD-8 replacement in different scenarios including a beam test. PASTTREC falls 20% short of the ASD-8 time precision but performs better w.r.t. signal charge measurements and overall operation stability. The measured time precision as a function of distance to the sense wire was modeled within a 3D GARFIELD simulation of the HADES drift cell.

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.

Evaluation of the readout electronics based on the center of gravity method for position sensitive radiation detection.

In the application of position sensitive radiation detection, the center of gravity method is often used to obtain better spatial resolution. In order to obtain the resolution degradation caused by the readout electronics, an evaluation method is put forward in this paper. The principle of the method is to simulate the signal distribution on sense wires of the MWPC (Multiwire Proportional Chamber) detector. The evaluation software quantizes the simulated data and drives the digital to analog converter to generate test signals. The readout electronics is evaluated with these stimulus signals according to the readout scale. An evaluation board based on this method is implemented. Tests are carried out in the laboratory to evaluate a readout circuit for the MWPC detector. The position resolution contributed by the electronics is better than 15 μm when the swtiching frenquency of the switch array is 12.5 MHz. The test results proved that the evaluation method is correct and practical. It can greatly simplify the evaluation of the readout electronics.

Noise Characterization and Filtering in the MicroBooNE Liquid Argon TPC

The low-noise operation of readout electronics in a liquid argon time projection chamber (LArTPC) is critical to properly extract the distribution of ionization charge deposited on the wire planes of the TPC, especially for the induction planes. This paper describes the characteristics and mitigation of the observed noise in the MicroBooNE detector. The MicroBooNE's single-phase LArTPC comprises two induction planes and one collection sense wire plane with a total of 8256 wires. Current induced on each TPC wire is amplified and shaped by custom low-power, low-noise ASICs immersed in the liquid argon. The digitization of the signal waveform occurs outside the cryostat. Using data from the first year of MicroBooNE operations, several excess noise sources in the TPC were identified and mitigated. The residual equivalent noise charge (ENC) after noise filtering varies with wire length and is found to be below 400 electrons for the longest wires (4.7 m). The response is consistent with the cold electronics design expectations and is found to be stable with time and uniform over the functioning channels. This noise level is significantly lower than previous experiments utilizing warm front-end electronics.

The construction technique of the high granularity and high transparency drift chamber of MEG II

The MEG experiment searches for the charged lepton flavor violating decay, μ +→ e+γ. MEG has already determined the world best upper limit on the branching ratio BR<4.2× 10−13 at 90% CL. An upgrade of the whole detector has been approved to obtain a substantial increase in sensitivity. Currently MEG is in upgrade phases, this phase involves all the detectors. The new positron tracker is a single volume, full stereo, small cells drift chamber (DCH) co-axial to the beam line. It is composed of 10 concentric layers and each single drift cell is approximately square 7 mm side, with a 20 μ m gold plated W sense wire surrounded by 40 μ m and 50 μ m silver plated Al field wires in a ratio of 5:1, about 12,000 wires. Due to the high wire density (12 wires/cm2), the use of the classical feed-through technique as wire anchoring system could hardly be implemented and therefore it was necessary to develop new wiring strategies. The number of wires and the stringent requirements on the precision of their position and on the uniformity of the wire mechanical tension impose the use of an automatic system to operate the wiring procedures. This wiring robot, designed and built at the INFN Lecce and University of Salento laboratories, consists of: ⋅ a semiautomatic wiring machine with a high precision on wire mechanical tensioning (better than 0.5 g) and on wire positioning (20 μ m) for simultaneous wiring of multiwire layers;⋅ a contact-less infrared laser soldering tool; ⋅ an automatic handling system for storing and transporting the multi-wire layers. The drift chamber is currently under construction at INFN and should be completed by the end of summer 2017 to be then delivered to PSI for commissioning.

Central Drift Chamber for Belle-II

The Central Drift Chamber (CDC) is the main device for tracking and identification of charged particles for Belle-II experiment. The Belle-II CDC is cylindrical wire chamber with 14336 sense wires, 2.3 m-length and 2.2 m-diameter. The wire chamber and readout electronics have been completely replaced from the Belle CDC. The new readout electronics system must handle higher trigger rate of 30 kHz with less dead time at the design luminosity of 8 × 1035 cm−2s−1. The front-end electronics are located close to detector and send digitized signal through optical fibers. The Amp-Shaper-Discriminator chips, FADC and FPGA are assembled on a single board. Belle-II CDC with readout electronics has been installed successfully in Belle structure in October 2016. We will present overview of the Belle-II CDC and status of commissioning with cosmic ray.

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.

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.