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Register a new userCharged particle timing at sub-25 picosecond precision: the PICOSEC detection concept
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Added by
Francisco Jose Iguaz Gutierrez Dr.
Publication date
2018
fields
Physics
and research's language is
English
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The PICOSEC detection concept consists in a two-stage Micromegas detector coupled to a Cherenkov radiator and equipped with a photocathode. A proof of concept has already been tested: a single-photoelectron response of 76 ps has been measured with a femtosecond UV laser at CEA/IRAMIS, while a time resolution of 24 ps with a mean yield of 10.4 photoelectrons has been measured for 150 GeV muons at the CERN SPS H4 secondary line. This work will present the main results of this prototype and the performance of the different detector configurations tested in 2016-18 beam campaigns: readouts (bulk, resistive, multipad) and photocathodes (metallic+CsI, pure metallic, diamond). Finally, the prospects for building a demonstrator based on PICOSEC detection concept for future experiments will be discussed. In particular, the scaling strategies for a large area coverage with a multichannel readout plane, the R&D on solid converters for building a robust photocathode and the different resistive configurations for a robust readout.
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The prospect of pileup induced backgrounds at the High Luminosity LHC (HL-LHC) has stimulated intense interest in developing technologies for charged particle detection with accurate timing at high rates. The required accuracy follows directly from the nominal interaction distribution within a bunch crossing ($sigma_zsim5$ cm, $sigma_tsim170$ ps). A time resolution of the order of 20-30 ps would lead to significant reduction of these backgrounds. With this goal, we present a new detection concept called PICOSEC, which is based on a two-stage Micromegas detector coupled to a Cherenkov radiator and equipped with a photocathode. First results obtained with this new detector yield a time resolution of 24 ps for 150 GeV muons, and 76 ps for single photoelectrons.
The prospect of pileup induced backgrounds at the High Luminosity LHC (HL-LHC) has stimulated intense interest in technology for charged particle timing at high rates. In contrast to the role of timing for particle identification, which has driven incremental improvements in timing, the LHC timing challenge dictates a specific level of timing performance- roughly 20-30 picoseconds. Since the elapsed time for an LHC bunch crossing (with standard design book parameters) has an rms spread of 170 picoseconds, the $sim50-100$ picosecond resolution now commonly achieved in TOF systems would be insufficient to resolve multiple in-time pileup. Here we present a MicroMegas based structure which achieves the required time precision (ie 24 picoseconds for 150 GeV $mu$s) and could potentially offer an inexpensive solution covering large areas with $sim 1$ cm$^2$ pixel size. We present here a proof-of-principle which motivates further work in our group toward realizing a practical design capable of long-term survival in a high rate experiment.
The experimental requirements in near future accelerators (e.g. High Luminosity-LHC) has stimulated intense interest in development of detectors with high precision timing capabilities. With this as a goal, a new detection concept called PICOSEC, which is based to a two-stage MicroMegas detector coupled to a Cherenkov radiator equipped with a photocathode has been developed. Results obtained with this new detector yield a time resolution of 24,ps for 150,GeV muons and 76,ps for single photoelectrons. In this paper we will report on the performance of the PICOSEC in test beams, as well as simulation studies and modelling of its timing characteristics.
The PICOSEC Micromegas detector can time the arrival of Minimum Ionizing Particles with a sub-25 ps precision. A very good timing resolution in detecting single photons is also demonstrated in laser beams. The PICOSEC timing resolution is determined mainly by the drift field. The arrival time of the signal and the timing resolution vary with the size of the pulse amplitude. Detailed simulations based on GARFIELD++ reproduce the experimental PICOSEC timing characteristics. This agreement is exploited to identify the microscopic physical variables, which determine the observed timing properties. In these studies, several counter-intuitive observations are made for the behavior of such microscopic variables. In order to gain insight on the main physical mechanisms causing the observed behavior, a phenomenological model is constructed and presented. The model is based on a simple mechanism of time-gain per interaction and it employs a statistical description of the avalanche evolution. It describes quantitatively the dynamical and statistical properties of the microscopic quantities, which determine the PICOSEC timing characteristics, in excellent agreement with the simulations. In parallel, it offers phenomenological explanations for the behavior of these microscopic variables. The formulae expressing this model can be used as a tool for fast and reliable predictions, provided that the input parameter values (e.g. drift velocities) are known for the considered operating conditions.
The multi-pad PICOSEC-Micromegas is an improved detector prototype with a segmented anode, consisting of 19 hexagonal pads. Detailed studies are performed with data collected in a muon beam over four representative pads. We demonstrate that such a device, scalable to a larger area, provides excellent time resolution and detection efficiency. As expected from earlier single-cell device studies, we measure a time resolution of approximately 25 picoseconds for charged particles hitting near the anode pad centers, and up to 30 picoseconds at the pad edges. Here, we study in detail the effect of drift gap thickness non-uniformity on the timing performance and evaluate impact position based corrections to obtain a uniform timing response over the full detector coverage.
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