Muon Detection System Research Articles

Validating Geant4 versions 7.1 and 8.3 against 6.1 for BaBar

Since 2005 and 2006, respectively, Geant4 versions 7.1 and 8.3 have been available, providing: improvements in modeling of multiple scattering; corrections to muon ionization and improved MIP signature; widening of the core of electromagnetic shower shape profiles; newer implementation of elastic scattering for hadronic processes; detailed implementation of Bertini cascade model for kaons and lambdas, and updated hadronic cross-sections from calorimeter beam tests. The effects of these changes in simulation are studied in terms of closer agreement of simulation using Geant4 versions 7.1 and 8.3 as compared to Geant4 version 6.1 with respect to data distributions of: the hit residuals of tracks in BABAR silicon vertex tracker; the photon and KOL shower shapes in the electromagnetic calorimeter; the ratio of energy deposited in the electromagnetic calorimeter and the flux return of the magnet instrumented with a muon detection system composed of resistive plate chambers and limited-streamer tubes; and the muon identification efficiency in the muon detector system of the BaBar detector.

See inside: The development of a cosmic ray muon imaging system to aid the clean up of the UK’s nuclear waste legacy

In recent years the use of non-intrusive and non-invasive imaging techniques to safely interrogate non-nuclear (industrial) storage vessels or process units has seen a significant increase. The nature of material found within active ‘legacy waste’ storage vessels and other radiation shielded vessels coupled with the distinct lack of access makes representative sampling or visual inspection of the vessel extremely problematic and in some cases impossible. However, until recently, the radiation shielding which is commonplace on all nuclear sites has rendered existing remote non-intrusive imaging techniques useless. This is due to the limiting penetrative power of X-rays and gamma-rays as well as lack of access for other semi-invasive techniques such as electrical and acoustic imaging. Cosmic ray muon based imaging systems have great potential. This is because muons have very high energies (up to 10 12 GeV) and therefore, offer a superior penetrative power which provides a means to ‘peer through’ objects which otherwise would be inaccessible. Such objects may include lead lined silo or vessels as well as various intermediate material transport modules. Because muons only show detectable interactions with high atomic number material they also offer a means to detect the quantity and location of heavy metal elements and their associated compounds. In this work the first attempts at two-dimensional muon attenuation mapping are described. More specifically multiple plane prototype muon detection system has been used to image the resultant attenuation maps for a number of lead phantoms. This opens up possibilities for the collation of muon trajectory data which in turn can be used to track muon events both entering and leaving the object of interest allowing attenuation based image processing. It is believed that future work in this area will serve to significantly improve both the coverage area and the spatial resolution of the system though improved detector technology providing a powerful tool for the rendering of either large or dense objects.

Low momentum muon identification in the ATLAS detector at the LHC

Muon identification and high momentum measurement accuracy are crucial to fully exploit the physics potential of the ATLAS experiment at the LHC. The muon detection system of the ATLAS detector is characterized by two high precision tracking systems, namely the Inner Detector and the Muon Spectrometer, and sufficient calorimetry to ensure the safe absorption of hadrons before the spectrometer, yielding high purity muons with momenta above 3 GeV. In order to reconstruct and efficiently identify muon tracks, the MOORE and MuId Object-Oriented software packages have been developed within the ATLAS ATHENA framework. The MOORE and MuId algorithms combine to identify track segments in the Muon Spectrometer, exploit calorimeter information in order to extrapolate muons back to their production vertex, associate them with corresponding segments in the Inner Detector, and perform a combined fit to obtain optimal parameter resolution. To identify low pT muons that do not have a reconstructed Muon Spectrometer track, other strategies must be employed. We report on a method we developed to identify low pT muons and describe the offline performance studies. The simplicity of the algorithm renders it suitable for use in the ATLAS High-Level Trigger (HLT) system. We will discuss the adaptation of this algorithm for the Level Two Trigger.

Production and quality control of MWPC for the LHCb muon system at CERN

This work describes the production and quality control of the multi-wire proportional chamber for the LHCb muon detection system. The European Laboratory of Particle Physics (CERN) is in charge of the production of 134 chambers for the inner regions of the five Muon Stations. These chambers have demanding requirements on rate capability (>100 kHz/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and efficiency (>99%) in a short time window (20 ns), on overall response uniformity which has to be better than 30%, and on the aging properties. The technical design of the chambers is briefly presented, and the production line is described together with the quality assurance and quality control programs. This includes fabrication of the panels; wire winding, gluing, and soldering; gap uniformity control; pitch and wire tension measurement; gas leak tests; high-voltage training; and tests under intense radiation. An original method developed for gas gain uniformity measurements is described in detail, and the obtained results are shown

A novel technique for the production of large area Z-coordinate readout planes for the BABAR muon system

The B A B AR detector, at the Stanford Linear Accelerator Center is a general-purpose detector for the study of e + e - interactions at the ϒ ( 4 S ) resonance. B A B AR's muon-detection system consists of two parts: a hexagonal barrel region and two planar endcap regions each containing 18 layers of iron ( ∼ 3.6 λ ) , with resistive plate chambers within the inter-iron gaps. These chambers have suffered deterioration in performance over the past few years and are being replaced by limited streamer tube chambers in the barrel. Each layer of the system consists of a set of up to 10 streamer tube modules oriented parallel to the beamline providing the azimuthal coordinate ( Φ ) and a single “ Z-plane” with strips oriented perpendicular the streamer tubes providing the coordinate ( Z ) along the beamline. The large area Z-planes (up to 12 m 2 ) are 1 mm thick and contain 96 strips that detect the induced charge from avalanches on the streamer tube wires. This paper reports on the novel construction technique of the Z-planes.

Prototype of a cosmic muon detection system based on scintillation counters with MRS APD light readout

Scintillation tiles with MRS APD light readout (START) are proposed to be used as basic triggering units of a cosmic muon facility intended for regular tests of all of the numerous ALICE TOF modules in the course of their mass production and exploitation. A prototype 32-channel array of STARTs has been assembled and tested with cosmic rays and beam. With the bias voltage at approximately 50 V, the system has shown operational consistency and homogeneity, almost 100% detection efficiency over the whole surface and intrinsic noise of 10 - 2 Hz per detecting unit. If STARTs are to be mass-produced, the cost of a mosaic array is estimated at a moderate level of 3– 4 kUSD / m 2 .

Radiographic measurements of the internal structure of Mt. West Iwate with near-horizontal cosmic-ray muons and future developments

Cosmic-ray muon radiography has been studied as a potential method for the measurement of the internal structure of the active volcano Mt. West Iwate. We improved a cosmic-ray muon detection system built with a set of two position-sensitive segmented detectors by the multiplicity analysis of a soft-component background after passing through an Fe plate between the detectors. We measured the density of the region located 160 m under the peak of Mt. Kurokura and compared to the gravimetric data. Cosmic-ray muons as a radiographic probe provide useful information that complements the gravimetric data. We analyzed the data to find time-dependent changes in the cosmic-ray muon intensity after passing through Mt. West Iwate, and a lower limit of 0.82% was found in Mt. Kurokura at the 90% CL. We discuss the possibility of cosmic-ray muon tomography with two or more detection systems.

HyperCP: A high-rate spectrometer for the study of charged hyperon and kaon decays

The HyperCP experiment (Fermilab E871) was designed to search for rare phenomena in the decays of charged strange particles, in particular CP violation in Ξ and Λ hyperon decays with a sensitivity of 10 - 4 . Intense charged secondary beams were produced by 800 GeV/ c protons and momentum selected by a magnetic channel. Decay products were detected in a large-acceptance, high-rate magnetic spectrometer using multiwire proportional chambers, trigger hodoscopes, a hadronic calorimeter, and a muon-detection system. Nearly identical acceptances and efficiencies for hyperons and antihyperons decaying within an evacuated volume were achieved by reversing the polarities of the channel and spectrometer magnets. A high-rate data-acquisition system enabled 231 billion events to be recorded in 12 months of data-taking.

A muon identification and combined reconstruction procedure for the ATLAS detector at the LHC at CERN

Muon identification and high momentum measurement accuracy is crucial to fully exploit the physics potential that will be accessible with ATLAS experiment at the LHC. The muon energy of physics interest ranges in a large interval from few GeV, where the b-physics studies dominate the physics program, up to the highest values that could indicate the presence of new physics. The muon detection system of the ATLAS detector is characterized by two high precision tracking systems, namely the Inner Detector and the Muon Spectrometer plus a thick calorimeter that ensures a safe hadron absorption filtering with high purity muons with energy above 3 GeV. In order to combine the muon tracks reconstructed in the Inner Detector and the Muon Spectrometer the Muon Identification (MUID) Object-Oriented software package has been developed. The purpose of the MUID procedure is to associate tracks found in the Muon Spectrometer with the corresponding Inner Detector track and calorimeter information in order to identify muons at their production vertex with optimum parameter resolution. The performance of these two combined systems has been evaluated with single muons of fixed transverse momentum and with full physics events.

Gas system upgrade for the BaBar IFR detector at SLAC

A new gas distribution and monitoring system was installed as part of an upgrade of the forward endcap muon detection system (IFR) of the BaBar detector at SLAC. Over 300 gas circuits are controlled and monitored. The return gas flow is monitored by digital bubblers which use photo-gate electronics to count the bubbling rate. The rates are monitored in real time and recorded in a history database allowing studies of flow rate versus chamber performance.

Electro-Mechanical Behavior of the ATLAS Toroids in Fault Condition

The three toroids magnet in the ATLAS detector provides the magnetic field for the muon detection system. It consists of a barrel toroid and two end cap toroids, which are electrically and magnetically coupled. In order to guarantee a safe operation, the behavior of the toroid support structures have to be verified in fault conditions. The mechanical behavior of the ATLAS magnet system in the equilibrium operating condition has been calculated in the past. In this paper, results of 3D electro-magnetic calculations of unbalanced force distributions under fault conditions are presented and analyzed. In addition, the energy dissipation and acceptable operating ramp rate in the windings are discussed.

Measuring the Magnetic Field in the CMS Steel Yoke Elements

Flux loops and Hall probes are being installed on selected segments of the steel flux return of the 4 T solenoid of the compact muon solenoid (CMS) detector under construction at CERN (European Center for Nuclear Research). This steel also serves as part of the muon detection system of CMS and accurate characterization of the magnetic flux density in the steel as elsewhere in the detector is required. Voltages induced in the flux loops during fast discharge of the solenoid will be sampled and integrated to measure the change in average flux density in the steel during the discharge. Hall probes mounted on the surface of the steel segments will provide information about the fields internal and external to the steel. In the laboratory work reported herein small iron discs with flux loops on their peripheries and Hall probes on their flat surfaces are magnetized between the pole tips of a laboratory standard magnet and controlled power supply. The voltages induced in the flux loops during charging and discharging of the magnet are integrated and compared with the Hall probes which sample the fields immediately external to the discs. The experimental work reported here will provide interpretation of the flux coil and Hall probe measurements from the CMS magnet when it is commissioned in 2005.

CDF Run 2 muon system

The CDF muon detection system for Run 2 of the Fermilab Tevatron is described. Muon stubs are detected for |{eta}| < 1.5, and are matched to tracks in the central drift chamber at trigger level 1 for |{eta}| < 1.25. Detectors in the |{eta}| < 1 central region, built for previous runs, have been enhanced to survive the higher rate environment and closer bunch spacing (3.5 {micro}sec to 396 nsec) of Run 2. Azimuthal gaps in the central region have been filled in. New detectors have been added to extend the coverage from |{eta}| < 1 to |{eta}| < 1.5, consisting of four layers of drift chambers covered with matching scintillators for triggering. The Level 1 Extremely Fast Tracker supplies matching tracks with measured p{sub T} for the muon trigger. The system has been in operation for over 18 months. Operating experience and reconstructed data are presented.

The CMS muon system

An overview of the CMS Muon Detector System design and goals is made. The system includes several types of detectors. In the barrel part Drift Tube Chambers are used, whereas Cathode Strip Chambers have been chosen for the endcaps. The main features, and the performance, of both types of chambers are described. We also report on the current status of the production of these detectors.

Restoring contaminated wires, removing gas contaminants, and aging studies of drift tube chambers

The original muon detection system of the Fermilab D0 colliding beam experiment contained 12,000 drift cells 10 cm×5 cm in cross-section and up to 580 cm in length. The gas mixture used was Ar/CF 4/CO 2 (90:6:4). There was one recycling gas system for all the chambers. During the first year of operation, it was discovered that inefficient cells, all in regions of high radiation, had a contaminating shell of crud coating their wires. The source of the contaminant was outgassing of the cathode pads, which were made from a laminate of fiberglass and epoxy/polyester resin, with a copper cladding on one surface. The vapor formed a brittle sheath on the wires, but only in regions of high current discharge due to radiation from the accelerator and colliding beams. A method for cleaning wires in place was devised. By heating the wire quickly to a temperature close to the melting temperature of gold, the sheath was ripped to shreds and blown away. The procedure for “zapping” wires and for removing the contaminating vapor is presented. The upgraded D0 experiment now uses Iarocci-type mini-drift tubes for the forward muon system. The results of aging tests for these chambers are also presented.

Review of the CMS muon detector system

The muon detector system of CMS consists of 3 sub detectors, the barrel drift tube chambers (DTs), the end cap cathode strip chambers (CSCs) and the resistive plate chambers (RPCs). During the last years the layouts of the sub detectors have been optimized by testing several prototypes. Now the project is frozen and the mass production of the chambers has started. Several production centers are coordinating their efforts. The muon system will be completed within September 2005. The final detectors, the construction status and planning and some test of the produced chambers will be presented.

Development of a two-fold segmented detection system for near horizontally cosmic-ray muons to probe the internal structure of a volcano

Very high-energy cosmic-ray muons penetrating through a mountain enable us to probe internal structure of volcanoes. An improved cosmic-ray muon detection system comprising two segmented detectors with multiplicity cut of the soft-component background of cosmic ray was developed. By applying to the measurement on internal structure of the volcano Mt. Asama, we proved that the volume occupancy in the region of a crater is less than 30%.

The CMS muon detector

The muon detection system of the Compact Muon Solenoid experiment is described. It consists of three different detector technologies: drift tubes in the barrel region, cathode strip chambers in the endcap region and resistive plate chambers in both barrel and endcap regions. The CMS muon detection system ensures excellent muon detection and efficient triggering in the pseudorapidity range 0< η<2.4. The most recent developments and some results from the R&D program will also be discussed.

Development of the Cosmic-Ray Muon Detection System for Probing Internal-Structure of a Volcano

Very high-energy cosmic-ray muons penetrating through a mountain enable us to probe the internal structure of volcanoes. An improved cosmic-ray muon detection system comprising two segmented detectors with multiplicity cut of the soft components of cosmic rays was developed. The test measurement for the volcano Mt. Asama is described.

A large Streamer Chamber muon tracking detector in a high-flux fixed-target application

Abstract Arrays of limited streamer tubes of the Iarocci type were deployed in our experiment at CERN as part of a forward muon detector system with provisions for the beam to pass through the center of each panel in the array. A total of 16 4 m×4 m panels were assembled with inductive readout strips on both sides of each panel. An active feedback system was deployed to regulate the high voltage to the streamer tubes to insure a constant efficiency for minimum ionizing particles. The arrays were operated in this environment for over five years of data taking. Streamer tube track-reconstruction efficiencies and tube replacement rates are reported.