Straw Tracker Research Articles

NA62 Spectrometer: A Low Mass Straw Tracker

Abstract The NA62 experiment at CERN, aiming at a precision measurement of the ultra-rare decay K + → π + νν, relies on kinematical rejection up to 10 5 (≈ 10 12 is needed in total). One of the limiting factors to achieve this goal is the multiple scattering in the magnetic spectrometer for kaon decay products; therefore an almost massless (≈1.5% X0) straw tracker has been designed to operate in vacuum, to be able to install it inside the decay volume. A vacuum tight prototype was built and tested in 2010: efficiency (≈99%), rate capability and single straw resolution (≈200 μm) were verified. The construction of the first chamber started in 2011.

Straw tracker prototype for the precise measurement of the very rare decay [formula omitted] (NA62 experiment at SPS CERN)

The proposal (CERN no. P326) for a new experiment, NA62, is described. This experiment aims to perform a precise measurement of the very rare kaon decay K + → π + ν ν ¯ branching ratio. About 80 K + → π + ν ν ¯ events with 10% of background are expected to be obtained in two years of data taking. To reconstruct charged pion tracks with high efficiency and high resolution a single magnet spectrometer based on straw tubes, working in vacuum, should be designed and produced. The current status of R&D of this detector and the results of its prototype tests are discussed.

Development of segmented straws for very high-rate capability coordinate detector

To reduce the occupancy of the large-size coordinate detectors, the high-granularity straw tracking chamber has been designed and tested. The main tasks were to improve the detector granularity and provide the best value of the detector radiation thickness. We have developed the techniques of the multiple anode production, assembling of the segmented straws and the low-mass readout by means of flat cable. Testing of the constructed prototypes has shown that these techniques can be applied to build the high-granularity straw detectors.

Development of high granulated straw chambers of large sizes

We have developed the baseline design for the straw drift tube tracking detectors for high rate environment application. The low-mass inner straw elements and the technology of the multianode straws assembly was devised and checked. The prototype chamber was constructed and studied the granularity of similar chambers can be reduced to one cm2. Submitted to Physics of Elementary Particles and Atomic Nuclei, Letters

The LHCb tracking system

The LHCb detector is being constructed to measure CP-violation parameters and rare B decays. The LHCb tracking system consists of silicon micro-strip detectors and straw chambers. The system is composed of four major sub-detectors: the Vertex Locator (Velo), Trigger Tracker (TT), Inner Tracker (IT) and Outer Tracker (OT). The Velo uses silicon micro-strip detectors which are placed at 8 mm from the beam, and that can be retracted during injection. The TT is a four-layer silicon-strip detector that covers the full acceptance of the experiment at the entrance of the spectrometer dipole magnet. The fringe field of the magnet allows the transverse momentum of tracks to be measured by their deflection between the Velo and TT detectors for use in the trigger. The IT and OT detectors measure the tracks behind the magnet. The IT is a silicon-strip detector which covers the region close to the beam pipe, while the OT is a straw tube detector which covers the rest of the acceptance. All of the detectors are currently under construction and will be ready for installation before the end of 2006. The expected performance for the tracking system is as follows: the tracking efficiency is larger than 95% and the ghost rate is smaller than 7%, for tracks with a momentum larger than 12 GeV. The momentum resolution ranges from 0.35% to 0.5% and the IP resolution reaches 14 μm for tracks with a large transverse momentum.

Performance of a Prototype Tracking Detector With Waveform Sampling Electronics

A straw tracking detector was proposed for the MECO experiment in order to measure the parameters of the helical trajectory of electrons emitted from stopped muon decays. The events of interest are expected to be embedded in an intense background of both energetic electrons and low-energy protons. A prototype of the proposed detector with its DAQ system was built, tested, and compared to a simulation. The results are reported in this paper. They provide the information required to improve the computer simulation of the MECO experiment, and in general, the design of any high-rate DAQ system that is required to efficiently select minimum ionizing tracks from an environment of highly ionizing particles

Static forces on the anode wires in a straw chamber

This paper derives equations for the deflection of an anode wire in a proportional straw chamber under electrostatic forces due to misalignments of the wire, deformation of the straw tube surface, and gravity.

A new design of wire locators for drift tubes

Every position-sensitive wire detector needs to solve the problem of wire positioning with a defined accuracy all over its sensitive volume. In particular, thin-walled drift tubes ("straws"), which are currently being attached to large detector units of several tens of square meters of surface, need to be equipped with wire locators along their signal wires. A wire locator has been developed together with an insertion device, especially for medium-sized drift tube systems, which significantly reduces the production time and avoids the danger of applying epoxy glue to the signal wire. The wire locator is being inserted in one single time-saving production step together with the signal wire itself. The proposed design is being compared to the rigid wire locators in use in the COMPASS straw tracking system at CERN. The investigation comprises both wire-centering capability and influence on the efficiency of adjacent detector regions, demonstrating the competitive performance of the proposed new system. Its sufficient mechanical reliability could be shown by means of an X-ray tomography; the attractively small influence on the drift field was determined in a test measurement using a silicon tracking system in a hadron beam.

The COMPASS spectrometer at CERN

The COMPASS spectrometer was designed for the NA58 fixed-target experiment at the CERN SPS. The physics aim is the study of the spin structure of the nucleon and the spectroscopy of hadrons with muon and hadron beams. Several novel techniques like Micromegas, GEMs and straw tracking detectors were deployed as well as large area CsI-based photo detectors for the RICH. A powerful DAQ and custom front-end electronics allow very high data rates. The paper focuses on the performance of the spectrometer during the first physics run in 2002 in which 5 billion events corresponding to 260 TByte of data were collected with a 160 GeV muon beam and polarised deuteron target.

DYNAMICS OF A STRAW TRACKER WHEEL-DETECTOR

This article deals with the dynamic analysis of a straw tracker wheel-detector of ATLAS, an experiment of the future Large Hadron Collider (LHC) to be installed at CERN. To take into account the severe particle trajectory detection specifications, both static and dynamic responses of the wheel-detector to the vibratory environment must be predicted at the design stage. After a description of the various components of the LHC and of the vibration sources, the dynamic characteristics of the wheel-detector are determined by an experimental modal analysis and by a finite element model. Finally, the predicted response of the structure to vibration spectra defined by existing studies and specific measurements provides the answer to the question, ‘Is there a dynamic risk?’

A light straw tracker detector working in vacuum

We are developing a straw tracking system with 3000 straws to work under vacuum conditions. The inactive parts of the detector-like frames, gas system and electronics, etc. have an extremely small mass density to reduce straggling of charged particles which will be detected in further surrounding detectors like the TOF-experiment at COSY. We avoid a massive frame by running the straw tubes with an excess pressure of 1 bar. The mechanical properties and the excess pressure create the necessary wire tension and the stability of the straw tubes which have a wall thickness of 30 μm Mylar. In this paper, we present our new detector concept and discuss results of the first prototype tests.

ATLAS: triggers for B-physics

The LHC will produce b b ̄ events at an unprecedented rate. The number of events recorded by ATLAS will be limited by the rate at which they can be stored offline and subsequently analysed. Despite the huge number of events, the small branching ratios mean that analysis of many of the most interesting channels for CP violation and other measurements will be limited by statistics. The challenge for the Trigger and Data Acquisition (DAQ) system is therefore to maximise the fraction of interesting B decays in the B-physics data stream. The ATLAS Trigger/DAQ system is split into three levels. The initial B-physics selection is made in the first-level trigger by an inclusive low- p T muon trigger (∼6 GeV) . The second-level trigger strategy is based on identifying classes of final states by their partial reconstruction. The muon trigger is confirmed before proceeding to a track search. Electron/hadron separation is given by the transition radiation tracking detector and the Electromagnetic calorimeter. Muon identification is possible using the muon detectors and the hadronic calorimeter. From silicon strips, pixels and straw tracking, precise track reconstruction is used to make selections based on invariant mass, momentum and impact parameter. The ATLAS trigger group is currently engaged in algorithm development and performance optimisation for the B-physics trigger. This is closely coupled to the R&D programme for the higher-level triggers. Together the two programmes of work will optimise the hardware, architecture and algorithms to meet the challenging requirements. This paper describes the current status and progress of this work.

Complementary particle ID: transition radiation and d E/d x relativistic rise

The Particle Identification (PID) methods using Transition Radiation (TR) and Relativistic Rise (RR) of the ionization losses are discussed as a complementary methods to a RICH technique. The comparative possibilities and limitations of these PID are considered. For the TR the modern high granularity detectors are described (ATLAS Transition Radiation Straw Tracker – TRT – as an example). The comparison is given between widely used Truncated Mean (TM technique) and a new approach based on Time over Threshold (ToT) measurements, which is more preferable due to the simplification of readout electronics and possibility of the fast triggering.

Straw chamber prototype for COMPASS tracker system

The construction principals for straw tube chambers with size 3×2 m2 for Large Area Tracker (LAT) of COMPASS experiment are presented. A prototype with 2 m straw tubes has been made assembled. See possibility mechanical deformation and his dimension. Laborotory tests of the prototype were perfored. A good mechanical tolerance and stability of gas gain in longitudinal 2 m straw tubes was demonstrated. Also studying dependence of the tube lengthen with change of humidity and temperature. Bring results test of chamber prototype with size 600×800 mm make in CERN.

A straw chambers’ tracker for the high rate experiment 835 at the Fermilab accumulator

Two layers of proportional drift tubes (aluminum mylar straws) are staggered in two cylindrical light chambers to measure charged particles’ azimuthal angle. To stand the high rates (∼10kHz/cm2) and minimize the pile-up of the high luminosity experiment 835 at FNAL, a fast ASIC Amplifier-Shaper-Discriminator (ASD-8B) was chosen. The front-end electronics, designed exclusively with SMD components, was mounted on the downstream end plug of each chamber to avoid oscillations and noise. Design, construction and operational performances of these detectors are presented.

The ATLAS transition radiation straw tracker (or TRT): present status and performance

The main issues relevant to reliable operation of the ATALS Transition Radiation Tacker (TRT) at LHC are discussed. Progress in the development of large scale straw-tube mechanical and of front-end electronics is presented. The expected TRT performance at LHC is also illustrated

Straw chambers operating in vacuum for particle tracking and transition radiation detection in accelerator and space experiments

We have designed and tested some straw tubes prototype detectors to investigate the possibility to operate a full size chamber with extremely reduced gas leaks in a high vacuum environment in accelerator experiments or in sealed mode for astroparticle physics researches in outer space. After completing the tests we have finally built a tracking detector of 1300 channels which has run in a vacuum chamber in the experiment E864 at BNL with a leak of 7 × 10 −3Torr l/s compatible with the permeability of the materials used.

Particle identification performance of a straw transition radiation tracker prototype

An 864 channel prototype of an integrated straw tracker and transition radiation detector for tracking and electron identification has been tested with and without magnetic field at the CERN SPS. The rejection against hadrons and converted photons has been measured and the dependence of the rejection power on detection parameters has been investigated. Tracking and hadron rejection were also studied in a high multiplicity environment. The results are compared with Monte Carlo simulations. Wherever possible, conclusions are drawn concerning the performance of a full-scale detector at the future Large Hadron Collider.

The Atlas TRT straw proportional tubes: performance at very high counting rate

Results on analog front-end electronics and straw performance studies at high counting rates are described. Prototypes of the electronics have been tested at counting rates up to 17.5 MHz. A drift-time accuracy of 180 μm and a drift-time measurement efficiency of 53% were obtained at 17.5 MHz. The expected counting rate is between 5 and 15 MHz (depending on straw position) for the Atlas straw tracker at LHC design luminosity, leading to an estimated drift-time accuracy at 160 μm and hit registration efficiency of 68% for the average counting rate of 10 MHz. These results are in a good agreement with detailed MC simulations and could be improved with better front-end electronics.

Particle identification with the JETSET straw chambers

Feasibility studies on particle identification were performed for the barrel drift-tube (“straw”) chamber of the JETSET (PS202) experiment at CERN-LEAR. The energy loss of traversing particles was investigated using elastic p̄p scattering (0.3≲ β≲0.7) and the reaction pp → π +π − ( β ≈ 0.995). The resulting distributions could be reproduced well by a Landau function, convoluted with a Gaussian in the low β case. A weighted mean was calculated out of the 5–17 single-straw samplings of a track as an estimate for its mean differential energy loss. A resolution of about 10% was obtained. Using the Bethe-Bloch equation without corrections, a resolution σ β ≈ 0.03 was achieved for tracks from elastic scattering. The long-term behaviour was studied, yielding information about aging effects and the dependence of the energy loss on counting-gas parameters.