A large area 100 channel Picosec Micromegas detector with sub 20 ps time resolution

The PICOSEC Micromegas precise timing detector is based on a Cherenkov radiator coupled to a semi-transparent photocathode and a Micromegas amplification structure. The first proof of concept single-channel small area prototype was able to achieve time resolution below 25 ps. One of the crucial aspects in the development of the precise timing gaseous detectors applicable in high-energy physics experiments is a modular design that enables large area coverage. The first 19-channel multi-pad prototype with an active area of approximately 10 cm$^2$ suffered from degraded timing resolution due to the non-uniformity of the preamplification gap. A new 100 cm$^2$ detector module with 100 channels based on a rigid hybrid ceramic/FR4 Micromegas board for improved drift gap uniformity was developed. Initial measurements with 80 GeV/c muons showed improvements in timing response over measured pads and a time resolution below 25 ps. More recent measurements with a new thinner drift gap detector module and newly developed RF pulse amplifiers show that the resolution can be enhanced to a level of 17~ps. This work will present the development of the detector from structural simulations, design, and beam test commissioning with a focus on the timing performance of a thinner drift gap detector module in combination with new electronics using an automated timing scan method

Towards robust PICOSEC Micromegas precise timing detectors

The PICOSEC Micromegas (MM) detector is a precise timing gaseous detector consisting of a Cherenkov radiator combined with a photocathode and a MM amplifying structure. A 100-channel non-resistive PICOSEC MM prototype with 10x10 cm^2 active area equipped with a Cesium Iodide (CsI) photocathode demonstrated a time resolution below 18 ps. The objective of this work is to improve the PICOSEC MM detector robustness aspects; i.e. integration of resistive MM and carbon-based photocathodes; while maintaining good time resolution. The PICOSEC MM prototypes have been tested in laboratory conditions and successfully characterised with 150 GeV/c muon beams at the CERN SPS H4 beam line. The excellent timing performance below 20 ps for an individual pad obtained with the 10x10 cm^2 area resistive PICOSEC MM of 20 MOhm/sq showed no significant time resolution degradation as a result of adding a resistive layer. A single-pad prototype equipped with a 12 nm thick Boron Carbide (B4C) photocathode presented a time resolution below 35 ps; opening up new possibilities for detectors with robust photocathodes. The results made the concept more suitable for the experiments in need of robust detectors with good time resolution

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb-Pb collisions at root s(NN)=2.76TeV

The elliptic flow, v(2), of muons from heavy-flavour hadron decays at forward rapidity (2.5 <y <4) is measured in Pb-Pb collisions at root s(NN)= 2.76TeVwith the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v(2) of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, p(T), is studied in the interval 3 <p(T)<10 GeV/c. A positive v(2) is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the p(T) interval from 3 to about 5GeV/c with a significance larger than 3 sigma, based on the combination of statistical and systematic uncertainties. The v(2) magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6 <p(T)<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Next-Generation Electronics for the Read-Out of Micro-Pattern Gaseous Detectors

Developed by the RD51 collaboration, the Scalable Readout System (SRS) is widely used for the read-out of Micro-Pattern Gaseous Detectors (MPGDs). With different front-end Application-Specific Integrated Circuits (ASICs) integrated into the SRS and its capability to read out small R&D set-ups up to mid-size experiments, the SRS functions as a multi-purpose read-out system. One of the ASICs integrated into the SRS is the VMM3a, which was specifically developed for the read-out of gaseous detectors. Due to its rich feature set and high configurability, it is the ideal candidate to further enhance the multi-purpose character of the SRS and move it into its next era. In the scope of this thesis, the capabilities of the VMM3a front-end of the RD51 Scalable Readout System (VMM3a/SRS) were explored for the charge read-out of MPGDs. This includes characterisation studies and the evaluation and improvement of calibration procedures to understand and optimise the system response. There it was found that the time resolution of VMM3a/SRS is better than 2 ns and that it allows to read-out detectors with trigger rates in the MHz regime. Furthermore, it was explored how different measurement types can benefit from the capabilities of VMM3a/SRS. As such, various kinds of X-ray imaging studies were performed with a single-detector set-up. In addition, a new beam telescope with VMM3a/SRS read-out was built for the RD51 collaboration, which meant the read-out of multiple detectors at the same time. This allowed to demonstrate that VMM3a/SRS can be used as an integrated read-out system, which provides position, time and energy information at the same time. In addition to the characterisation measurements, also different applications of VMM3a/SRS were demonstrated, such as the possibility to resolve argon fluorescence interactions inside gaseous detectors and use these interactions to determine the electron drift velocity. Ultimately, the newly built beam telescope was used in the NA61/SHINE experiment at CERN, demonstrating that VMM3a/SRS can be successfully operated in particle physics experiments

An automated testing system for the RD51 VMM hybrid and yield measurement of the first production batches

We present the development of an automated testing system for the VMM hybrid of the RD51 collaboration. The VMM hybrid is a new front-end board for the RD51 common readout system, the Scalable Readout System, and will become the workhorse for the next decade to read out Micro-Pattern Gaseous Detectors. It uses the VMM chip developed for the ATLAS New Small Wheel to convert charge signals from detectors to digital data. Our testing system automatically characterises the quality of the VMM chips on the hybrid after production during multiple tests. Results are evaluated to classify the chips and hybrids and uploaded to a database. We evaluated those results for the first two production batches to measure the production yield. The yield is better than the threshold below which chip testing on a wafer level offers financial benefits. Observations on prominent chip failures were propagated back to the hybrid production process to further increase the yield for future productions.We present the development of an automated testing system for the VMM hybrid of the RD51 collaboration. The VMM hybrid is a new front-end board for the RD51 common readout system, the Scalable Readout System, and will become the workhorse for the next decade to read out Micro-Pattern Gaseous Detectors. It uses the VMM chip developed for the ATLAS New Small Wheel to convert charge signals from detectors to digital data. Our testing system automatically characterises the quality of the VMM chips on the hybrid after production during multiple tests. Results are evaluated to classify the chips and hybrids and uploaded to a database. We evaluated those results for the first two production batches to measure the production yield. The yield is better than the threshold below which chip testing on a wafer level offers financial benefits. Observations on prominent chip failures were propagated back to the hybrid production process to further increase the yield for future productions

Studying signals in particle detectors with resistive elements such as the 2D resistive strip bulk MicroMegas

As demonstrated by the ATLAS New Small Wheel community with their MicroMegas (MM) design,resistive electrodes are now used in different detector types within the Micro Pattern GaseousDetector family to improve their robustness. The extended form of the Ramo-Shockley theorem forconductive media has been applied to a 1 MΩ/□ 2D resistive strip bulk MM to calculatethe signal spreading over neighbouring channels using an 80 GeV/c muon track. For this geometry,the dynamic weighting potential was obtained numerically using a finite element solver by applyinga junction condition and coordinate scaling technique to accurately represent the boundaryconditions of a 10 × 10 cm$^{2}$ active area. Using test beam measurements, the results ofthis model will be used to benchmark this microscopic modelling methodology for signal inductionin resistive particle detectors.As demonstrated by the ATLAS New Small Wheel community with their MicroMegas (MM) design, resistive electrodes are now used in different detector types within the Micro Pattern Gaseous Detector family to improve their robustness or performance. The extended form of the Ramo-Shockley theorem for conductive media has been applied to a 1 M$\Omega$/$\Box$ 2D resistive strip bulk MM to calculate the signal's spreading over neighbouring channels using an 80 GeV/c muon track. For this geometry, the dynamic weighting potential was obtained numerically using a finite element solver by applying a junction condition and coordinate scaling technique to accurately represent the boundary conditions of a $10\times 10$ cm$^2$ active area. Using test beam measurements, the results of this model will be used to benchmark this microscopic modelling methodology for signal induction in resistive particle detectors

燒津鰹漁業に於ける船仲組織(上) - 本邦漁業に特異なる勞働組織の一例 -

We report on the measurement of freeze-out radii for pairs of identical-charge pions measured in Pb-Pb collisions at √sNN = 2.76 TeV as a function of collision centrality and the average transverse momentum of the pair kT. Three-dimensional sizes of the system (femtoscopic radii), as well as direction-averaged onedimensional radii are extracted. The radii decrease with kT, following a power-law behavior. This is qualitatively consistent with expectations from a collectively expanding system, produced in hydrodynamic calculations. The radii also scale linearly with _dNch/dη_1/3. This behavior is compared to world data on femtoscopic radii in heavy-ion collisions. While the dependence is qualitatively similar to results at smaller √sNN, a decrease in the ratio Rout/Rside is seen, which is in qualitative agreement with a specific prediction from hydrodynamic models: a change from inside-out to outside-in freeze-out configuration. The results provide further evidence for the production of a collective, strongly coupled system in heavy-ion collisions at the CERN Large Hadron Collider