Diameter Drift Tubes Research Articles

Simulations of the Self-Focused Pseudospark-Sourced Electron Beam in a Background Ion Channel

Using pseudospark discharge sourced electron beams for the generation of high-peak-power millimeter and terahertz radiation has attracted increasing research interest in recent years. However, one of the crucially important and hitherto unanswered questions is what is the upper-frequency limit at which millimeter-wave devices can be driven by pseudospark discharge sourced electron beams?. In this paper, we studied this question from the perspective of beam transportation in a plasma background, more specifically an ion channel using particle-in-cell simulations to find the limitations. The parameter ranges of the beam transportation with small oscillations in the beam diameter were investigated and summarized, through simulations of beam propagation in a large diameter drift tube with different ion densities, plasma electron densities, beam density distributions, and beam energies. The beam transportation in a small diameter beam tunnel was also simulated. It showed the maximum beam current with a small velocity spread that can be transported in the beam tunnel was determined by the diameter of the beam tunnel and the ion density. High injected current will cause significant beam loss and reduce the overall efficiency. The simulation results indicate a minimum diameter of the beam tunnel in a millimeter-wave circuit that can be effectively driven by a pseudospark-sourced electron beam. The equivalent upper limit in the operating frequency is about 400 GHz.

Design and construction of integrated small-diameter drift tube and thin-gap resistive plate chambers for the phase-1 upgrade of the ATLAS muon spectrometer

In the long shutdown for the Phase-1 upgrade of the Large Hadron Collider (LHC) in 2019–2020, 16 new integrated muon tracking and trigger chambers will be installed at the ends of the toroid magnet coils in the small azimuthal sectors of the inner barrel layer (BIS) of the ATLAS muon spectrometer in order to improve the trigger selectivity and fake trigger suppression in the transition region 1 . 0 < | η | < 1 . 3 between the barrel part and the endcaps. The new muon detectors consist of a small-diameter muon drift tube (sMDT) precision tracking chamber with 15 mm tube diameter and a pair of thin-gap RPC chambers with 1 mm gas gap width. The new integrated chamber modules (labeled BIS 78) are currently under construction and will replace the present BIS 7 and 8 MDT tracking chambers with 30 mm diameter drift tubes. The project is the pilot phase for the complete replacement of the small barrel inner layer MDT chambers with the new integrated tracking and trigger detectors in the ATLAS Phase-2 upgrade in 2024–2026 in order to increase the barrel first-level muon trigger coverage and efficiency at the high luminosities at HL-LHC. The sMDT chambers have been chosen to make room for the new trigger chambers and because of their eight times higher rate capability than MDT chambers. The new thin-gap RPC chambers have about 15 times lower avalanche charges and correspondingly increased lifetime and rate capability at HL-LHC and will be operated in coincidence with the endcap trigger chambers. They consist of a triplet of gas gaps which has to be very thin as well and which is supported by a light-weight aluminum structure which is interleaved with the sMDT chamber supports.

Quantifying spot size reduction of a 1.8 kA electron beam for flash radiography

The spot size of Axis-I at the Dual Axis Radiographic Hydrodynamic Test facility was reduced by 15.5% by including a small diameter drift tube that acts to aperture the outer diameter of the electron beam. Comparing the measured values to both analytic calculations and results from a particle-in-cell model shows that one-third to one-half of the spot size reduction is due to a drop in beam emittance. We infer that one-half to two-thirds of the spot-size reduction is due to a reduction in beam-target interactions. Sources of emittance growth and the scaling of the final focal spot size with emittance and solenoid aberrations are also presented.

A drift chamber with a new type of straws for operation in vacuum

A 2150×2150mm2 registration area drift chamber capable of working in vacuum is presented. Thin-wall tubes (straws) of a new type are used in the chamber. A large share of these 9.80mm diameter drift tubes are made in Dubna from metalized 36µm Mylar film welded along the generatrix using an ultrasonic welding machine created at JINR. The main features of the chamber and some characteristics of the drift tubes are described. Four such chambers with the X, Y, U, V coordinates each, containing 7168 straws in total, are designed and produced at JINR and CERN. They are installed in the vacuum volume of the NA62 setup in order to study the ultra-rare decay K+→π+vv¯ and to search for and study rare meson decays. In autumn 2014 the chambers were used for the first time for the data taking in the experimental run of the NA62 at CERN׳s SPS.

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.

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.

THE HYBRID TRACKING SYSTEM OF ATLAS

The central tracker of the ATLAS experiment is built using both silicon and gaseous detectors immersed in a 2 T solenoidal magnetic field. To better match the topology of the tracks emerging from the proton–proton collisions, the tracker is separated into a central barrel part (measuring below pseudorapidity |η|≈1.2) and two end-caps (measuring from ≈1.2 to 2.5). Different technologies are used at different radii to optimize the cost–performance ratio. The innermost part, immediately surrounding the beam pipe and up to ≈15 cm , is made up of silicon pixels for best pattern recognition and maximal radiation resistance. The intermediate region (radii from 30 to 60 cm) uses microstrip detectors and provides excellent space resolution over a large area. The outer layer (radii from 60 to 95 cm) is made up of a large number of small diameter drift tubes (straws) which provide good space resolution in the track bending plane and greatly contribute to pattern recognition with multiple measurements. The transition radiation detection capability of this gaseous detector also helps in electron identification.

Track chambers based on proportional drift tubes with wire field shaping electrodes

The characteristics of track chambers based on round 60 mm diameter drift tubes with four wire field shaping electrodes, using a 88% Ar + 12% CO 2 gas mixture at atmospheric pressure, are described. These track chambers are planned to be used at the Serpukhov accelerator.

A new miniature x‐ray source for interstitial radiosurgery: Device description

A device that generates low-energy x rays at the tip of a needle-like probe was developed for stereotactic interstitial radiosurgery. Electrons from a small thermionic gun are accelerated to a final energy of up to 40 keV and directed along a 3 mm outside diameter drift tube to a thin Au target, where the beam size is approximately 0.3 mm. All high-voltage electronics are in the probe housing, connected by low-voltage cable to a battery-operated control box. X-ray output, which is nearly isotropic, consists of a bremsstrahlung spectrum and several lines between 7 and 14 keV, with characteristic radiation contributing 15% of the total energy output. To date, 14 patients with metastatic brain tumors have been treated with this device.

Wave Excitation in Waveguides below Cut-Off

A 400 kV, 2kA, electron beam has been used to grow space charge waves in a 5.0 cm diameter drift tube. The waves are excited by propagating the pencil beam through a series of annular metallic rings with alternate rings grounded and the others capacitively coupled to the beam. Measurements have been made and will be presented of the wave characteristics downstream of the exciting structure. The wave excitation may result from a parametric excitation of eigenmodes of the beam in the guide.

Propagation of an intense relativistic electron beam through a plasma region into vacuum

An intense relativistic electron beam (IREB) is injected through a narrow plasma region into a vacuum drift tube at current levels far above the space-charge limit of the drift tube. Experiments show that accelerated co-moving positive ions from the plasma enable the beam to propagate to a collector at the end of the 15 cm diameter drift tube. In one set of experiments, the IREB (1 MeV, 27 kA, 30 nsec) passes through a hydrogen gas cloud with an effective width of approximately 2 cm. The net current measured by a 7 cm diameter collector at the end of a 55 cm long drift tube is 70% of the peak injected electron current. In another configuration, the IREB is injected through a laser-produced carbon plasma. A model is proposed linking electron beam propagation with collective ion acceleration which results in the generation of charge- and current-neutral plasmoids capable of free space propagation. Possible implications of this work to astrophysical processes (cosmic ray acceleration) and laser fusion (observation of high-energy positive ions escaping from target plasma) are discussed.