Ring Imaging Cherenkov Research Articles

Results from cosmics and first LHC beam with the ALICE HMPID detector

The ALICE HMPID (High Momentum Particle IDentification) detector has been designed to identify charged pions and kaons in the range 1 ÷ 3 GeV/c and protons in the range 1.5 ÷ 5 GeV/c . It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters, covering in total 11 m 2, which exploit large area MWPC equipped with CsI photocathodes for Cherenkov light imaging emitted in a liquid C 6F 14 radiator. The ALICE detector has been widely commissioned using cosmics and LHC beam from December 2007 until October 2008. During the cosmics data taking the HMPID detector collected a large set of data, using mainly the trigger provided by the TOF detector. We present here preliminary results of detector alignment using TPC tracking. The HMPID could be operated in a stable way, at a safe HV setting, also during LHC beam injection and circulation tests, when a very large occupancy (up to 50%) was achieved. Resulting gain mapping and overall detector performance will also be discussed.

The High Voltage Protection Boards for the RICH Detectors of the LHCb Experiment

We present the protection system for the monitoring circuitry of the 20 kV high-voltage bias for the Hybrid Photon Detectors of the Ring Imaging Cherenkov detectors of the LHCb experiment. The protection system buffers the voltage lines, attenuated by about 12700 V/V in normal operating conditions, and limits the output voltage excursion to the ADCs of the monitoring system to a safe range (between -2.5 V and +5 V) in case of discharge. The circuit has been designed and tested to be radiation tolerant under the expected working conditions of LHCb. Results show that the protection boards are fully adequate for the whole LHCb lifetime.

Construction and performance of the BABAR-DIRC

The new type of ring-imaging Cherenkov detector technology called DIRC (an acronym for Detection of Internally Reflected Cherenkov Light) has been used successfully for hadronic particle identification in the BABAR experiment at the B Factory (PEP-II) located at the SLAC National Accelerator Laboratory. This paper describes the R&D for and the construction of the DIRC radiator bars and the performance of the DIRC during more than eight years of B Factory operation.

Hybrid Photon Detectors and Ion Feedback

The long-term development of the Ion Feedback rate of Hybrid Photon Detectors in the LHCb Ring Imaging Cherenkov detectors was studied as a sensitive measure of the vacuum quality. From a phenomenological understanding of the development reliable predictions can be made for individual photon detectors. Eighty percent of them will operate well for the lifetime of LHCb. In a 20% subsample a faster-than-expected degradation of the vacuum quality was found. A HPD repair and replacement programme guarantees a good performance of the LHCb RICH detector at all time during data taking.

The LHCb RICH detectors

The LHCb experiment at the Large Hadron Collider has been optimised for high precision measurements of the charm and beauty quark sector. The different particle species produced in the high-energy collision are identified using two Ring-Imaging Cherenkov detectors.

Proximity focusing RICH detector based on multilayer silica aerogel radiator

The performance of a proximity focusing Ring Imaging Cherenkov detector equipped with a radiator of silica aerogel is presented. The aerogel tile used is a monolith with variable index of refraction. Cherenkov photons are detected with high granularity by eight Hamamatsu H9500 flat panel multi anode phototubes.

The LHCb RICH online monitor and data-quality

The LHCb experiment at the Large Hadron Collider has been optimised for high precision measurements of the charm and beauty quark sector. Efficient particle identification at high purities over a wide momentum range from around 1 to 100 GeV/ c is vital to many LHCb analyses. Central to the LHCb particle identification strategy are two Ring Imaging CHerenkov (RICH) detectors. Rigorous monitoring of the RICH sub-detector is being developed to insure that high-quality data is recorded which meets the stringent demands from physics analyses.

Measurement of Cherenkov photons by SiPMs with light guides

Silicon Photomultipliers (SiPMs) are attractive photon detectors for Ring Imaging Cherenkov (RICH) counters inside large magnetic spectrometers due to their insensitivity to magnetic fields. We have investigated the possibilities offered by these new photon detectors in a cosmic ray test set-up. Cherenkov photons emitted by cosmic ray particles in an aerogel radiator have been detected with silicon photomultipliers for the first time. Estimates and tests show how light concentrators may improve the detection efficiency, thus showing promise for a SiPM based RICH detector. The optimum shape for these light guides is investigated.

The quest for a third generation of gaseous photon detectors for Cherenkov imaging counters

RICH (Ring Imaging CHerenkov) counters for PID in the high momentum domain and in large acceptance experiments require photon detectors covering extended surface (several square meters) and able to accept Cherenkov photons in a wide angular range. An ideal approach is represented by gaseous photon detectors, which allow covering wide surfaces at affordable costs. The first generation of these detectors was based on the use of organic vapors. The second generation consists of CsI photocathodes and open geometry gaseous detectors (MWPC). In spite of the success of this approach, some limits of the technique arise from the bombardment of the photocathodes by the ions generated in the amplification process and by the photon feedback. A third generation of gaseous photon detectors using closed geometry, as those possible with multistage arrangements of micropattern gaseous detectors, can overcome the observed limitations. We have started an R&D programme to develop a Thick-GEM-based photon detector and we report about our initial studies.

Study of an HAPD with 144 channels for the Aerogel RICH of the Belle upgrade

For the upgrade of the Belle detector at the KEKB collider, we are developing a proximity focusing ring imaging Cherenkov detector using aerogel as a radiator. A 144 channel HAPD (Hybrid Avalanche Photo-Detector) is one of the candidate photo-detectors. We have measured the performance of the HAPDs, and succeeded to read out signals from the HAPD corresponding to one photo-electron using ASICs that have been developed for this purpose. We have also performed a beam test with a 2 GeV electron beam, and succeeded to detect a Cherenkov ring from the aerogel radiator.

Hybrid photon detectors for the LHCb RICH system

The LHCb experiment, currently being commissioned at CERN, uses two Ring Imaging Cherenkov (RICH) detectors as its principal particle identification system. These detectors are essential in allowing LHCb to perform the precision measurements of CP-violation in B-meson mixing and decays for which the experiment was designed. The photodetectors used in the LHCb RICH system are Hybrid Photon Detectors (HPDs), which employ a vacuum photocathode and a solid-state pixel sensor. The operating principle and production process of the HPDs are described. The performance criteria for the HPDs is outlined, along with the qualification procedures carried out at dedicated test facilities. The compiled results of tests performed on more than 500 HPDs are presented. The performance of the HPDs in a 25 ns structured test-beam and during the RICH commissioning process with the HPDs installed is discussed. Finally, the time alignment of the HPDs via a pulsed laser system is described.

Very high voltage power supply system for the ring imaging Cherenkov detectors of the LHCb experiment

A modular power supply system is described, for use in the Ring Imaging Cherenkov Detectors of the LHCb experiment. The main characteristics of the supply are very good time stability and voltage resolution, full programmability, floating supplies, self protection and remote control. The choice of a commercial HV module with standard control inputs allows easy customisation to adapt our design to different requirements. The realisation shown here supplies voltages up to 20 kV with a maximum current of 0.5 mA and up to 32 channels on a single crate.

The RICH system of the LHCb experiment: Status and performance

The LHCb experiment is a single forward arm spectrometer at the LHC at CERN. Particle identification (pion, kaon and proton discrimination) is a crucial requirement to meet the physics goals of the experiment. This is provided by two Ring Imaging Cherenkov (RICH) detectors providing particle identification coverage between 1 and 100 GeV/ c. After a brief description of the LHCb experiment and RICH detectors, the results from the latest beam test using the final detector components and readout system will be given and the anticipated particle identification performance of the RICH detectors from Monte Carlo simulations will be presented. Finally, a technique to calibrate the particle identification performance of the RICH system with data using D * decays will be described.

Effects of radiation damage caused by proton irradiation on Multi-Pixel Photon Counters (MPPCs)

We have investigated the effects caused by proton-induced radiation damage on Multi-Pixel Photon Counter (MPPC), a pixelized photon detector developed by Hamamatsu Photonics. The leakage current of irradiated MPPC samples linearly increases with total irradiated doses due to radiation damage, which is not completely recovered even after a year from the irradiation. No significant change has been observed in the gains at least up to 8.0 Gy ( 9.1 × 10 7 n / mm 2 in 1 MeV neutron equivalent fluence, Φ eq ). The device has completely lost its photon-counting capability due to baseline fluctuations and noise pile-up after 21 Gy irradiation ( 2.4 × 10 8 n / mm 2 in Φ eq ), which might be problematic for some applications, such as ring-imaging Cherenkov detectors. We have found that the pulse-height resolution has been slightly deteriorated after 42 Gy irradiation ( 4.8 × 10 8 n / mm 2 in Φ eq ), where the measured sample has been illuminated with a few hundred photons. This effect should be considered in the case of energy-measurement applications.

Performance of the LHCb RICH photo-detectors and readout in a system test using charged particles from a 25 ns-structured beam

The LHCb experiment at the CERN Large Hadron Collider (LHC) utilises two Ring Imaging CHerenkov (RICH) detectors for particle identification. To verify that the RICH assembly will perform as expected prior to installation, an array of 48 production Hybrid Photon Detectors and their readout have been tested under realistic running conditions in a 25 ns-structured charged particle beam provided by the SPS facility at CERN. This system test is an important milestone in the overall commissioning of the LHCb detector and demonstrates that all aspects meet the stringent physics requirements of the LHCb experiment.

Hybrid Photon Detectors for the LHCb RICH: Performance and operational experience

Pion/kaon discrimination in the LHCb experiment will be provided by two Ring Imaging Cherenkov (RICH) counters. These use arrays of 484 Hybrid Photon Detectors (HPDs) to detect the Cherenkov photons emitted by charged particles traversing the RICH. The results from comprehensive quality assurance tests on the 550 HPDs manufactured for LHCb are described. Leakage currents, dead channel probabilities, dark count rates and ion feedback rates are reported. Furthermore, results from two specialised measurements carried out on a sample of HPDs to determine the efficiencies of the HPD pixel chip and photocathode, respectively, are described. Finally, an overview is given of the in situ performance of the HPDs which are now installed in the RICH.

Level 3 trigger algorithm and Hardware Platform for the HADES experiment

A next generation real time trigger method to improve the enrichment of lepton events in the High Acceptance DiElectron Spectrometer (HADES) trigger system has been developed. In addition, a flexible Hardware Platform (Gigabit Ethernet-Multi-Node, GE-MN) was developed to implement and test the trigger method. The trigger method correlates the ring information of the HADES Ring Imaging Cherenkov (RICH) detector with the fired wires (drift cells) of the HADES Mini Drift Chamber (MDC) detector. It is demonstrated that this Level 3 trigger method can enhance the number of events which contain leptons by a factor of up to 50 at efficiencies above 80%. The performance of the correlation method in terms of the events analyzed per second has been studied with the GE-MN prototype in a lab test setup by streaming previously recorded experiment data to the module. This paper is a compilation from Kirschner [Level 3 trigger algorithm and Hardware Platform for the HADES experiment, Ph.D. Thesis, II. Physikalisches Institut der Justus-Liebig-Universität Gießen, urn:nbn:de:hebis:26-opus-50784, October 2007 [1]].

The RICH detector of the LHCb experiment

The status of the Ring Imaging Cherenkov system of the LHCb experiment is reviewed. The detector is in the commissioning phase and it is expected to take data later this year at the start-up of the Large Hadron Collider, providing essential contributions to the physics program of the experiment.

The high-voltage system for the LHCb RICH hybrid photon detectors

We describe the characterization of the high-voltage (HV) distribution system designed and produced for the pixel hybrid photon detectors of the ring imaging Cherenkov counters of the LHCb experiment. The HV system consists of a series of printed circuit boards with a specific layout designed to prevent any discharge arising from high electric fields. The system has dedicated monitoring and control features to supervise HV set-up during data taking. The full production of the HV system has been now completed and all the boards have been fully characterized and installed in the detector, which is currently being commissioned.

Development of FARICH-detector for ALICE experiment at CERN

In order to extend the momentum range of the charged particle identification up to 10 GeV /c for pion–kaon separation and to 14 GeV /c for kaon–proton separation of the ALICE experiment at LHC (CERN), the focusing aerogel ring imaging Cherenkov (FARICH) detector employing a multi-layer silica aerogel as radiator has been proposed. The design project of the FARICH Prototype is presented. Results of the test of the avalanche photo-diodes with metal-resistance-semiconductor structure produced by the Centre of Perspective Technology and Apparatus (CPTA MRS APDs) are shown. Preliminary data of tests of the light-collecting capability for aluminum and stainless steel Winston cone holes of different types are presented. The performance of the proposed detector was estimated using the GEANT4 simulation. Results of the optimization of characteristics of the aerogel radiators, CPTA MRS APDs with and without wavelength shifter paint are discussed.