PANDA Barrel Research Articles

Performance of the most recent Microchannel-Plate PMTs for the PANDA DIRC detectors at FAIR

In the PANDA experiment at the FAIR facility at GSI two DIRC (Detection of Internally Reflected Cherenkov light) detectors will be used for π/K separation up to 4GeV/c. Due to their location in a high magnetic field and other stringent requirements like high detection efficiency, low dark count rate, radiation hardness, long lifetime and good timing, MCP-PMTs (microchannel-plate photomultiplier) were the best choice of photon sensors for the DIRC detectors in the PANDA experiment. This paper will present the performance of some of the latest 2 × 2inch 2 MCP-PMTs from Photek and Photonis, including the first mass production tubes for the PANDA Barrel DIRC from Photonis. Performance parameters like the collection efficiency (CE), quantum efficiency (QE), and gain homogeneity were determined. The effect of magnetic fields on some properties like gain and charge cloud width was investigated as well. Apart from that the spatial distribution of many internal parameters like time resolution, dark count rate, afterpulse ratio, charge sharing crosstalk and recoil electrons were measured simultaneously with a multihit capable DAQ system. The latest generation of Photonis MCP-PMTs shows a unexpected ”escalation” effect where the MCP-PMT itself produces photons.

The PANDA Barrel DIRC

The PANDA experiment at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR), Darmstadt, Germany, will address fundamental questions of hadron physics using p̄p annihilations. Excellent Particle Identification (PID) over a large range of solid angles and particle momenta will be essential to meet the objectives of the rich physics program. Charged PID in the target region will be provided by a Barrel DIRC (Detection of Internally Reflected Cherenkov light) counter. The Barrel DIRC, covering the polar angle range of 22–140 degrees, will provide a π/K separation power of at least 3 standard deviations for charged particle momenta up to 3.5 GeV/c. The design of the Barrel DIRC features narrow radiator bars made from synthetic fused silica, an innovative multi-layer spherical lens focusing system, a prism-shaped synthetic fused silica expansion volume, and an array of lifetime-enhanced Microchannel Plate PMTs (MCP-PMTs) to detect the hit location and arrival time of the Cherenkov photons. Detailed Monte-Carlo simulations were performed, and reconstruction methods were developed to study the performance of the system. All critical aspects of the design and the performance were validated with system prototypes in a mixed hadron beam at the CERN PS. In 2020 the PANDA Barrel DIRC project advanced from the design stage to component fabrication. The series production of the fused silica bars was successfully completed in 2021 and delivery of the MCP-PMTs started in May 2022.

PANDA Barrel DIRC: From Design to Component Production

Excellent particle identification (PID) will be essential for the PANDA experiment at FAIR. The Barrel DIRC will separate kaons and pions with at least 3 s.d. for momenta up to 3.5 GeV/c and polar angles between 22 and 140 deg. After successful validation of the final design in the CERN PS/T9 beam line, the tendering process for the two most time- and cost-intensive items, radiator bars and MCP-PMTs, started in 2018. In Sep. 2019 Nikon was selected to build the fused silica bars and successfully completed the series production of 112 bars in Feb. 2021. Measurements of the mechanical quality of the bars were performed by Nikon and the optical quality was evaluated at GSI. In Dec. 2020, the contract for the fabrication of the MCP-PMTs was awarded to PHOTONIS and the delivery of the first-of-series MCP-PMTs is expected in July 2021. We present the design of the PANDA Barrel DIRC as well as the status of the component series production and the result of the quality assurance measurements.

Status of the PANDA Barrel DIRC

The PANDA experiment will use cooled antiproton beams with high intensity stored in the High Energy Storage Ring at FAIR. Reactions on a fixed target producing charmed hadrons will shed light on the strong QCD. Three ring imaging Cherenkov counters are used for charged particle identification. The status of the Barrel DIRC (Detection of Internally Reflected Cherenkov light) is described. Its design is robust and its performance validated in experiments with test beams. The PANDA Barrel DIRC has entered the construction phase and will be installed in 2023/2024.

DIRC: Internally reflecting imaging Cherenkov detectors

In this article we review a distinctive type of Cherenkov ring imaging device generically called a DIRC detector. DIRC is an acronym for “Detection of Internally Reflected Cherenkov (Light)”. We briefly discuss how these devices were first motivated and conceived, describe their basic operating principles, their early prototypes, and fabrication R&D. We then describe the BaBar DIRC at SLAC, as the first full scale implementation of this detector type for a major physics experiment. Further R&D at SLAC that was motivated to enable operations at the very high rates of SuperB factories led to the Focusing DIRC concept and prototype that will next be described. We then review a wide range of further developments now underway using variants on the DIRC theme, including the TOP counter at Belle-II; a number of FDIRC designs for GLUEX, PANDA barrel and endcap; and the LHCb TORCH.

The innovative design of the PANDA Barrel DIRC

The innovative design of the PANDA Barrel DIRC

The PANDA Barrel DIRC

The PANDA experiment at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR) near GSI, Darmstadt, Germany will address fundamental questions of hadron physics. Excellent Particle Identification (PID) over a large range of solid angles and particle momenta will be essential to meet the objectives of the rich physics program. Charged PID for the barrel region of the PANDA target spectrometer will be provided by a DIRC (Detection of Internally Reflected Cherenkov light) detector. The Barrel DIRC will cover the polar angle range of 22̂–140̂ and cleanly separate charged pions from kaons for momenta between 0.5 GeV/c and 3.5 GeV/c with a separation power of at least 3 standard deviations. The design is based on the successful BABAR DIRC and the SuperB FDIRC R&D with several important improvements to optimize the performance for PANDA, such as a focusing lens system, fast timing, a compact fused silica prism as expansion region, and lifetime-enhanced Microchannel-Plate PMTs for photon detection. This article describes the technical design of the PANDA Barrel DIRC and the result of the design validation using a “vertical slice” prototype in hadronic particle beams at the CERN PS.

Performance of prototypes for the PANDA barrel EMC

The PANDA experiment will be part of the future Facility for Antiproton and Ion Research (FAIR) and aims for the study of strong interaction within the charm sector via antiproton proton collisions up to antiproton momenta of 15 GeV/c. Reflecting the variety of the physics program the PANDA detector is designed as a multi-purpose detector able to perform tracking, calorimetry and particle identification with nearly complete coverage of the solid angle. The Electromagnetic Calorimeter (EMC) contained inside its Target Spectrometer is based on cooled PbWO4 scintillator crystals. In order to ensure an excellent performance throughout the large dynamic range of photon/electron energies ranging from a few MeV up to 15 GeV an extensive prototyping phase is mandatory. This contribution describes the measured response of the EMC barrel part prototype PROTO60 at the largest design energy to secondary beams provided by the SPS at CERN. In addition to PROTO60 a tracking station was deployed, providing precise position information of the 15 GeV/c positrons. For calibration purposes a 150 GeV/c muon beam and cosmic radiation, in combination with estimations from GEANT4 simulations were used. The obtained performance concerning energy, position and time information is presented.

Simulation and reconstruction of the PANDA Barrel DIRC

Hadronic particle identification (PID) in the barrel region of the PANDA experiment at the new Facility for Antiproton and Ion Research in Europe (FAIR) at GSI, Darmstadt will be provided by a DIRC (Detection of Internally Reflected Cherenkov light) counter. To optimize the performance and reduce the detector cost, detailed simulations of different design elements, such as the width of the radiators, the shape of the expansion volume, and the type of focusing system, were performed using Geant. Custom reconstruction algorithms were developed to match the detector geometry. We will discuss the single photon resolution and photon yield as well as the PID performance for the Barrel DIRC baseline design and several detector design options.

Status of the PANDA Barrel DIRC

The PANDA experiment at the future Facility for Antiproton andIon Research in Europe GmbH (FAIR) at GSI, Darmstadt will studyfundamental questions of hadron physics and QCD using high-intensitycooled antiproton beams with momenta between 1.5 and 15 GeV/c.Hadronic PID in the barrel region of the PANDA detector will beprovided by a DIRC (Detection of Internally Reflected Cherenkov light)counter. The design is based on the successful BABAR DIRC withseveral key improvements, such as fast photon timing and a compactimaging region. Detailed Monte Carlo simulation studies wereperformed for DIRC designs based on narrow bars or wide plates with avariety of focusing solutions. The performance of each design wascharacterized in terms of photon yield and single photon Cherenkovangle resolution and a maximum likelihood approach was used todetermine the π/K separation. Selected design options wereimplemented in prototypes and tested with hadronic particle beams atGSI and CERN. This article describes the status of the design andR&D for the PANDA Barrel DIRC detector, with a focus on theperformance of different DIRC designs in simulation and particlebeams.

Development of an Endcap DIRC for PANDA

The aim of this research is to develop a planar DIRC detector showing advantages and performance similar to a classical, barrel shaped DIRC, but at smaller polar angles which cannot be accessed using a cylindrical geometry. The device will complement the PANDA Barrel DIRC by covering polar angles from 5° to 22°. The envisaged π/K-separation is ≥3σ up to 4GeV/c.A major challenge is the adaption of the device to the PANDA environment including a magnetic field of ~1–2T, high rates and radiation, limited space for optics and sensors as well as the lack of a common first-level trigger. This paper discusses a detector design which forms a compromise between these constraints and available hardware, a specific analytic reconstruction method, a performance estimation based on Geant4 simulations and finally the successful particle identification using a recent R&D prototype.

The PANDA Barrel DIRC detector

The PANDA experiment at the new Facility for Antiproton and Ion Research in Europe (FAIR) at GSI, Darmstadt, will study fundamental questions of hadron physics and QCD using high-intensity cooled antiproton beams with momenta between 1.5 and 15GeV/c. Efficient Particle Identification for a wide momentum range and the full solid angle is required for reconstructing the various physics channels of the PANDA program. Hadronic Particle Identification in the barrel region of the detector will be provided by a DIRC counter. The design is based on the successful BABAR DIRC with important improvements, such as focusing optics and fast photon timing. Several of these improvements, including different radiator geometries and optics, were tested in particle beams at GSI and at CERN. The evolution of the conceptual design of the PANDA Barrel DIRC and the performance of complex prototypes in test beam campaigns will be discussed.

Lifetime of MCP-PMTs

The main particle identification detector of the PANDA experiment will be of the DIRC type. For various reasons the favored sensors are micro-channel plate photo multipliers (MCP-PMTs). Despite many advantageous properties MCP-PMTs until recently had serious problems with aging issues at high photon rates. In this paper we present a simultaneous aging measurement for the latest MCP-PMTs of BINP, Hamamatsu (R10754X) and PHOTONIS (XP85112). In these devices specific countermeasures have been applied to reduce the loss of quantum efficiency (QE) of the photo cathode (PC) with increasing anode charge, which is the main feature of aging. We find that the new techniques show a significantly increased lifetime of the concerning MCP-PMTs. With several surface scans across the active area of the MCP-PMTs we find evidence that the loss of QE develops from the rims and corners of the PC. In addition, the spectral QE of the MCP-PMTs is given as a function of the integrated anode charge revealing that for the R10754X the QE drops faster for long wavelenghts than for short ones. At this point of the ongoing measurements the XP85112 does not show any significant aging signs after 5.6 C/cm2 which is a more than an order of magnitude improvement compared to former MCP-PMTs and corresponds to more than 10 years of running time for the PANDA Barrel DIRC. In this PMT the micro-channels are coated by an atomic layer deposition (ALD) technique which currently appears to be the most promising countermeasure against the aging of MCP-PMTs.

Simulation and reconstruction of the PANDA Barrel DIRC detector**Work supported by EU FP6 grant, contract number 515873, DIRAC secondary-beams and EU FP7 grant, contract number 227431, HadronPhysics2, HGS-Hire and HIC for FAIR.

The PANDA experiment at the future Facility for Antiproton and Ion Research (FAIR) at GSI, Darmstadt, aims at studying the strong interacting matter by precision spectroscopy. A detector system with excellent particle identification over a large range of solid angle and momentum is therefore mandatory. Charged hadron identification in the barrel region will be performed by a compact ring imaging Cherenkov detector based on the DIRC principle (Detection of Internally Reflected Cherenkov light), designed to separate pions from kaons with at least 3 standard deviations in the momentum range from 0.5 GeV/c to 3.5 GeV/c. We present details of the simulation of the PANDA Barrel DIRC and a study of the detector performance using a fast reconstruction algorithm to determine the single photon Cherenkov angle resolution and photon yield for several design options.