Spatial resolution of triple-GEM detectors Kudryavtsev, V.N.; Maltsev, T.V.; Shekhtman, L.I.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
Recenzirano
Gas Electron Multiplier (GEM) based detectors are widely used in numerous collider experiments and, in particular, at the Budker Institute of Nuclear Physics (BINP). In order to determine the best ...possible spatial resolution, the simulation of charged particle registration process is accomplished. The simulation shows that spatial resolution is definitely less than 20μm for applied operation configurations. The simulation of electron transport through single GEM and through GEM-cascade shows that an electron cluster is compressed by GEM holes and an effective transverse diffusion is reduced by approximately 15% as maximum. The experimental part of the work is devoted to the operability tests of the designed detector with orthogonal strips readout with a pitch of 250μm and the measurements of its characteristics including the dependence of gain on GEM-voltage, the registration efficiency and the spatial resolution. Spatial resolution of the studied detector is measured as 31.5±0.9(stat.)−7.5+6.9(syst.)μm.
In this work we describe simulation and experimental studies of the possible reasons for the observed increase of the maximum gain in multi-GEM devices. Two main hypotheses are analyzed: first, a ...diffusion-dominated charge spread reducing the density in individual holes, acting as independent amplifiers and therefore an increase of the discharge limit with the number of cascaded electrodes; second, the possibility that total avalanche charge before transition to a discharge (Raether limit) strongly depends on the field value and is therefore much higher in cascaded than in single-stage systems.
Gas Electron Multiplier (GEM) based coordinate detectors are used at different high energy physics centres and at Budker Institute of Nuclear Physics particularly. These detectors possess a spatial ...resolution in ten micron scale together with high rate capability up to 107 cm−2s−1. Thus, the precise investigation of best possible spatial resolution, achieved with GEM-detectors, is the subject of interest. The experimental data, accumulated by the moment, gives the possibility to compare it with the simulation results. The simulation of applied detector configurations includes transport of electrons through the detector and tracking of avalanche evolution inside the working volume, as well as obtaining signal distribution on the readout strips. The spatial resolution, obtained in the simulation of an individual detector, is found to be essentially better (the difference is about two standard deviations) than the experimental results. Further efforts to find out the reasons of the contradiction between the simulation and measurements were made. In particular, the simulation of complete experimental set-up (including tracking detectors) was performed. The results of individual detector simulation and the simulation of complete set-up were determined to generally coincide.
We study the causes and signs of degradation of cementite in chromium-nickel cast iron used for the production of massive forming rolls and the specific features of structural formation in cementite ...under the influence of operating temperatures and local strains formed in the rolls in the course of their operation. For this purpose, we use the procedure of high-temperature vacuum etching in order to detect dislocations, scanning electron microscopy, and the method of optical-mathematical description of the phases and their heterogeneity. It is shown that the degradation of cementite is connected with the formation of dislocation structures and diffusion, which promote the formation of new types of carbide phases with nonstoichiometric compositions, quasicrystalline graphite, and also ferrite and bainite. Possible combinations of newly formed phases are identified. They are also responsible for the stability of carbides. By analyzing the results of our studies of the degradation of cementite (regarded as a structural component specifying the level of hardness of the operating cast iron), we give recommendations concerning the possibility of improvement of stability of the cementite structure and decreasing the level of stresses in the rolls.
Micro-pattern gas technology is planned for the upgrade of the tracking system of the CMD-3 detector at the VEPP-2000 electron-positron collider in Budker INP. The upgrade includes a new cylinder ...tracking and trigger detector that consists of two tracking layers at a radius of 32 to 33 cm with coordinate resolution close to 0.1 mm in Z (along the beam axis) and trigger segments of about 1 cm in phi. Another new coordinate subsystem includes two end-cap discs with active area between radius of 50 mm and 250 mm, that provides spatial resolution in R and in phi close to 1 mm as well as trigger signal from the phi segments. For these two subsystems we plan to use micro-RWELL technology because it allows much simpler assembling of large cylindrical detector and large discs due to more rigid glass-fiber support as compared to the triple GEM technology. The new cylindrical detector and end-cap discs of the CMD-3 are considered as a prototypes of the Inner Tracker of the detector for the future Super C-Tau Factory (SCTF) at Budker INP. The SCTF is an electron-positron collider for the energy range of 3-7 GeV in the center of mass system that will provide luminosity of 1035 cm−2s−1. Coordinate system of the detector for the SCTF will include among other systems, the Inner Tracker and the end-cap discs. The Inner Tracker will be 60 cm long and occupy radius up to 20 cm, while the end-cap discs will have radius up to 180 cm and will have to provide trigger signal. For the end-cap discs the MPGD option is considered based either on the triple-GEM or on the micro-RWELL, while for the Inner Tracker three main options are competing: compact Time Projection Chamber, silicon micro-strip tracker and cylindrical MPGD tracker. The first results of simulations with all these options are presented with preliminary discussion about the choice of the option.
The multilayer ion-plasma coating TiN/CrN, 6 layers of CrN and 5 lauers of TiN, for hardening of piston rings is proposed. It is established that as a result of hardening, the wear rate of rings ...decreases 15.7 times. A new method for estimating the residual thickness of the coating, which gives recommendations for improving the quality of coatings, is proposed.
The spatial resolution of GEM based tracking detectors has been simulated and measured. The simulation includes the GEANT4 based transport of high energy electrons with careful accounting for atomic ...relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing, including accounting for diffusion, gas amplification fluctuations, the distribution of signals on readout electrodes, electronics noise and a particular algorithm of the final coordinate calculation (center of gravity). The simulation demonstrates that a minimum of the spatial resolution of about 10
μ
m can be achieved with strip pitches from 250
μ
m to 300
μ
m. For larger pitches the resolution is quickly degrading reaching 80-100
μ
m at a pitch of 500
μ
m. The spatial resolution of low-material triple-GEM detectors for the DEUTRON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4M collider. The amount of material in these detectors is reduced by etching the copper of the GEMs electrodes and using a readout structure on a thin kapton foil rather than on a glass fibre plate. The exact amount of material in one DEUTRON detector is measured by studying multiple scattering of 100 MeV electrons in it. The result of these measurements is X/X0 = 2.4×10
−3
corresponding to a thickness of the copper layers of the GEM foils of 3
μ
m. The spatial resolution of one DEUTRON detector is measured with 500 MeV electrons and the measured value is equal to 35 ± 1
μ
m for orthogonal tracks.
Currently, the Budker Institute of Nuclear Physics together with Novosibirsk State University are developing the detector for the future Super Charm-Tau Factory (SCTF) to be built in Russia. SCTF is ...an electron–positron collider with 3.5GeV per beam and a luminosity of 1035cm−2s−1. SCTF will be instrumented with a general-purpose detector (SCTD). The innermost part of the SCTD will contain the inner tracker (IT). The main task of the IT is an extension of the lever arm of the central drift chamber, efficient detection of soft hadrons and reconstruction of secondary vertices of particles that decay in the IT volume (like Ks,Λ0, etc.). The most attractive candidate for the IT is the compact time-projection chamber (CTPC). It can be made with a very thin inner wall allowing to reduce significantly the threshold for soft hadrons. In addition, CTPC can provide the dE/dx information for the discrimination of electrons from hadrons. We present recent results on the simulation of spatial resolution and drift time of CTPC as well as space charge effects induced by positive ions.
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