High-pressure Drift Tubes Research Articles

Effects of modular ion-funnel technology onto analysis of breath VOCs by means of real-time mass spectrometry

Proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a powerful tool for real-time monitoring of trace concentrations of volatile organic compounds (VOCs). The sensitivity of PTR-ToF-MS also depends on the ability to effectively focus and transmit ions from the relatively high-pressure drift tube (DT) to the low-pressure mass analyzer. In the present study, a modular ion-funnel (IF) is placed adjacent to the DT of a PTR-ToF-MS instrument to improve the ion-focusing. IF consists of a series of electrodes with gradually decreasing orifice diameters. Radio frequency (RF) voltage and direct current (DC) electric field are then applied to the electrodes to get the ions focused. We investigated the effect of the RF voltage and DC field on the sensitivity of a pattern of VOCs including hydrocarbons, alcohols, aldehydes, ketones, and aromatic compounds. In a proof-of-concept study, the instrument operating both as normal DT (DC-mode) and at optimal IF conditions (RF-mode) was applied for the breath analysis of 21 healthy human subjects. For the range of investigated VOCs, an improvement of one order of magnitude in sensitivity was observed in RF-mode compared with DC-mode. Limits of detection could be improved by a factor of 2–4 in RF-mode compared with DC-mode. Operating the instrument in RF-mode allowed the detection of more compounds in the exhaled air compared with DC-mode. Incorporation of the IF considerably improved the performance of PTR-ToF-MS allowing the real-time monitoring of a larger number of potential breath biomarkers.Graphical abstract

Resolution of the ATLAS muon spectrometer monitored drift tubes in LHC Run 2

The momentum measurement capability of the ATLAS muon spectrometer relies fundamentally on the intrinsic single-hit spatial resolution of the monitored drift tube precision tracking chambers. Optimal resolution is achieved with a dedicated calibration program that addresses the specific operating conditions of the 354 000 high-pressure drift tubes in the spectrometer. The calibrations consist of a set of timing offsets and drift time to drift distance transfer relations, and result in chamber resolution functions. This paper describes novel algorithms to obtain precision calibrations from data collected by ATLAS in LHC Run 2 and from a gas monitoring chamber, deployed in a dedicated gas facility. The algorithm output consists of a pair of correction constants per chamber which are applied to baseline calibrations, and determined to be valid for the entire ATLAS Run 2. The final single-hit spatial resolution, averaged over 1172 monitored drift tube chambers, is 81.7 ± 2.2 μm.

Spatial resolution of thin-walled high-pressure drift tubes

A small prototype detector based on high pressure thin-walled tubes (straws) has been developed and its parameters have been studied on a bench at JINR, Dubna, and SPS at CERN. The inner diameter of the straws is 9.53 mm. The pressure of the active gas mixture Ar/CO 2 (80/20) was varied from 1 to 5 bar. The best spatial resolution achieved in this pressure range is ∼40 μm. Both the high efficiency and high rate capability are retained.

Commissioning with cosmic rays of the muon spectrometer of the ATLAS experiment at the large hadron collider

The Muon Spectrometer of the ATLAS experiment is made of large toroidal magnets, arrays of high-pressure drift tubes for precise tracking and dedicated fast detectors for the first-level trigger. All the detectors in the barrel toroid have been installed and commissioning has started with cosmic rays. These detectors are arranged in three concentric rings and the total area is about 6000 square meters. During the installation and commissioning of the detectors, data are usually taken with the magnet off, but a dedicated run took place with the magnetic field of the barrel toroid turned on. We present the procedure to control the response of the single detectors installed in the barrel toroid, Monitored Drift Tubes and Resistive Plate Chambers, and results of the first tests done with cosmic rays triggered by the first-level processor and read-out trough the ATLAS data acquisition. Details on the installation and commissioning schedule will be given in view of the completion of the instrumentation of the muon spectrometer for the first period of data taking with proton-proton collisions.

Validation Tools for ATLAS Muon Spectrometer Commissioning

The ATLAS Muon Spectrometer (MS), currently being installed at CERN, is designed to measure final state muons of 14 TeV proton-proton interactions at the Large Hadron Collider (LHC) with a good momentum resolution of 2–3% at 10–100 GeV/c and 10% at 1 TeV, taking into account the high level background enviroment, the inhomogeneous magnetic field, and the large size of the apparatus (24 m diameter by 44 m length). The MS layout of the ATLAS detector is made of a large toroidal magnet, arrays of high-pressure drift tubes for precise tracking and dedicated fast detectors for the first-level trigger, and is organized in eight Large and eight Small sectors. All the detectors of the barrel toroid have been installed and the commissioning has started with cosmic rays. In order to validate the MS performance using cosmic events, a Muon Commissioning Validation package has been developed and its results are presented in this paper. Integration with the rest of the ATLAS sub-detectors is now being done in the ATLAS cavern.

The barrel-inner-large tracking chambers for the ATLAS muon spectrometer: Ready for installation

We describe the commissioning and performance tests of 116 high pressure drift tube chambers, MDT, built to equip the inner ring of the Muon Barrel Spectrometer of the ATLAS experiment at the Large Hadron Collider. After assembly and test in the home laboratories, the chambers were transported at CERN, equipped with the final version of the front-end electronics, alignment system, temperature and magnetic field probes, slow controls for a complete system-test of all detectors. The uniformity of response of the drift tubes and the tracking performance of the chambers were measured with cosmic rays before installation in the experiment. A summary of the commissioning procedure and of the results of the performance tests is presented.

Test of the BIL tracking chambers for the ATLAS Muon Spectrometer

We describe the final quality tests of 116 high-pressure drift tube chambers (MDT – Monitored Drift Tube) built to equip the inner ring of the muon barrel spectrometer of the ATLAS experiment at the LHC. The chambers are equipped with read-out, optical alignment system, temperature and magnetic field probes. The procedure to test the single components and to test the chambers for gas and current leaks is described. Mechanical adjustments were performed to insure the quality of response of the tubes in the whole chamber. The uniformity of response of the drift tubes and the tracking performance of each chamber were measured with cosmic rays.

Study of the drift properties of high-pressure drift tubes for the ATLAS muon spectrometer

High-pressure monitored drift tube (MDT) chambers are used as precision tracking detectors in the Muon Spectrometer of the ATLAS experiment at the Large Hadron Collider. MDT chambers, operated at 3 bar absolute pressure with 93% argon 7% carbon dioxide gas mixture, were tested with cosmic rays at the Roma TRE test site, and their properties upon variations of the operating conditions are discussed. The improvement of spatial resolution using the measurement of a fraction of the collected charge, exploiting the final version of the MDT electronics, is considered

Assembly and test of the BIL tracking chambers for the ATLAS Muon spectrometer

We describe the assembly procedure and the performance tests of 62 high pressure drift tube chambers, MDT, that equip the inner ring of the Muon Barrel Spectrometer of the ATLAS experiment at the LHC. The uniformity of response of the drift tubes and the tracking performance of the chambers were measured with cosmic rays and compared with the results obtained with high momentum muons.

Performance of BIL tracking chambers for the ATLAS muon spectrometer

Tracking in the muon spectrometer of the ATLAS experiment at the Large Hadron Collider is based on high pressure drift tubes. The performance of Monitored Drift Tube (MDT) chambers has been extensively studied with cosmic rays at the Roma Tre test site. Results on chamber calibration and resolution with varying operating conditions, such as gas composition and temperature, have been investigated. The improvement of spatial resolution using the measurement of a fraction of the collected charge is also discussed.

Improvement of High Pressure Drift Tube for Negative Ion Mobility Measurement

Negative ion mobility of oxygen molecules in oxygen has been measured by high pressure ion drift tube. The ion drift tube equips a positive corona gap as a negative ion detector. It allows for the measurement under the atmospheric pressure. The ion drift space is varied from 1 to 9 cm using a micrometer attached on a feedthrough of the chamber. The observed mobility decreases against E/p0 and the tendency becomes remarkable in the shorter ion drift space. This would be caused by the field distortion effect near the mesh electrode. The electric field analysis is performed using a finite element method. It is found that field distortion is found by mesh electrode, separated the ion drift gap and the ion detecting gap. The mesh is changed in to new one of which diameter is 0.05mm. The obtained mobility can be improved and the reduced mobility μ0-=2.31±0.03cm2/V·s is obtained.

High-precision spectroscopy with the ATLAS muon system

The ATLAS muon spectrometer will measure muon tracks along a spectrometer arm of up to 15 m length, embedded in a magnetic field of ∼0.5 T . The precision tracking devices in the muon system will be high-pressure drift tubes (MDTs). To achieve a momentum resolution of ∼10% for muons with a transverse momentum of p T =1 TeV/c , the systematic error to the space–time relationship has to be smaller than δ r.m.s. <70 μm . Contributions to a systematic error δ r.m.s. and its impact on the muon-momentum resolution are discussed. LHC physics require excellent knowledge of the absolute momentum scale. We show a calibration method which will achieve an accuracy at the 10 −4 level.

Measurement of the mobilities of Cl−, NO2−⋅H2O, NO3−⋅H2O, CO3−⋅H2O, and CO4−⋅H2O in N2 as a function of temperature

The zero-field mobilities of Cl and the first water clusters of NO2,-NO3,-CO3,-and COu-in N2 are measured. The measurements are perfromed in a high-pressure drift tube mass spectrometer. (AIP)