Test of the HAPD light sensor for the Belle II Aerogel RICH Yusa, Y.; Adachi, I.; Dolenec, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2017, Letnik:
876
Journal Article
Recenzirano
The Aerogel Ring-Imaging Cherenkov detector (ARICH) is being installed in the endcap region of Belle II spectrometer to identify particles from B meson decays by detecting the Cherenkov ring image ...from aerogel radiators. To detect single photons, high-sensitive photon detector which has wide effective area (∼70mm × 70mm), a Hybrid Avalanche Photo Detector (HAPD), has been developed in a collaboration with Hamamatsu K.K. The HAPD consists of hybrid structure of a vacuum tube and an avalanche photodiode (APD). It can be operated in 1.5T magnetic field of the spectrometer and withstands the radiation levels expected in the Belle II experiment. There are two steps of electric pulse amplification: acceleration of photo-electron in electric field in the vacuum tube part and electron avalanche in the APD part resulting in total gain of order 105. For the ARICH, we use 420 HAPDs in total. Before installing them, we performed quality assessment studies such as measurements of dark current, noise level, signal-to-noise ratio and two-dimensional scan with laser illumination. We also measured quantum efficiency of the photocathode. During the HAPD performance tests in the magnetic field, we observed very large signal pulses which cause long dead time of the readout electronics in some of the HAPDs. We have carried out a number of studies to understand this phenomenon, and have found a way to mitigate it and suppress the degradation of the ARICH performance. In this report, we will show a summary of the HAPD performance and quality assessment measurements including validation in the magnetic field for all of the HAPDs manufactured for the ARICH in the Belle II.
In the forward end-cap of the Belle II spectrometer, particle identification is provided by a proximity focusing RICH detector with an aerogel radiator (ARICH). The ARICH’s primary function is to ...effectively distinguish between pions and kaons in the momentum range of 0.5GeV/c to about 4GeV/c, as well as to contribute to identification of low-momentum leptons. Since its operation began, Belle II has collected over 420fb−1 of data. Based on this large data sample, studies of several effects that impact the performance of the ARICH detector were carried out. In this paper, we present a comparison of the observed Cherenkov ring image and detector particle identification performance in the measured data and detector simulation. Furthermore, we highlight recent efforts aimed at enhancing the ARICH’s performance by taking into account the effects of particle decay in flight and scattering in materials before the detector, as well as by refining the probability density function used for particle identification likelihood evaluation.
The Belle II experiment is a new generation B factory experiment at the SuperKEKB electron–positron collider. The main purpose of the experiment is to search for new physics with a large sample of B ...meson decays. The proximity-focusing Aerogel Ring-Imaging Cherenkov detector (ARICH) has been designed to identify kaons and pions in the forward end-cap of the Belle II spectrometer. Using aerogel as radiator with specialized photon sensors called HAPD, the K/π separation is expected to reach more than 4 σ in the momentum range from 0.5 GeV/c to 4.0 GeV/c. ARICH detector was constructed in summer 2017 and was installed in the Belle II spectrometer in the beam line of the SuperKEKB collider. The test of the ARICH detector is performed using both cosmic rays and the beam collisions during the accelerator commissioning. We observe Cherenkov rings in the ARICH detector associated with charged tracks detected by the tracking system. The reconstructed Cherenkov angle distribution has a clear and reasonable peak. The ARICH K∕π separation performance is evaluated using Bhabha events in beam runs; the separation power achieve the design value.
Front-end electronics of the Belle II aerogel ring imaging detector Pestotnik, R.; Adachi, I.; Burmistrov, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Letnik:
952
Journal Article
Recenzirano
A proximity focusing RICH detector with an aerogel radiator is used for charged particle identification in the forward end-cap of the Belle II spectrometer. The detector, consisting of a 4 cm aerogel ...radiator, a 16 cm expansion volume and a photon detector with 420 Hybrid Avalanche Photo Detectors, is mounted in a very confined space between Central Drift Chamber and Electromagnetic Calorimeter, allowing only 5 cm of space for the readout electronics. In our solution, low power front-end read-out boards are mounted at the back side of each of the HAPD photosensors. These boards have each been tested individually before their installation onto the photosensors and into the spectrometer. Most important design issues and first experiences with the aforementioned front-end read-out boards are presented in this contribution.
We have developed a RICH counter as a new forward particle identification device for the Belle II experiment. As a Cherenkov radiator in this counter, a dual aerogel layer combination consisting of ...two refractive indicies, n=1.045 and 1.055, is employed. Mass production of these aerogel tiles has been done during 2013–2014 with new method improved by Chiba group. Optical qualities for them have been examined. The refractive indices of the obtained tiles were found to be in good agreement with our expectations, and the transparencies were high enough to be used for the RICH radiator.
Development of slow control system for the Belle II ARICH counter Yonenaga, M.; Adachi, I.; Dolenec, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2017, Letnik:
876
Journal Article
Recenzirano
A slow control system (SCS) for the Aerogel Ring Imaging Cherenkov (ARICH) counter in the Belle II experiment was newly developed and coded in the development frameworks of the Belle II DAQ software. ...The ARICH is based on 420 Hybrid Avalanche Photo-Detectors (HAPDs). Each HAPD has 144 pixels to be readout and requires 6 power supply (PS) channels, therefore a total number of 2520 PS channels and 60,480 pixels have to be configured and controlled. Graphical User Interfaces (GUIs) with detector oriented view and device oriented view, were also implemented to ease the detector operation. The ARICH SCS is in operation for detector construction and cosmic rays tests. The paper describes the detailed features of the SCS and preliminary results of operation of a reduced set of hardware which confirm the scalability to the full detector.
Development of the ARICH monitor system for the Belle II experiment Hataya, K.; Adachi, I.; Dolenec, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2017, Letnik:
876
Journal Article
Recenzirano
The Belle II detector is under construction at KEK in Japan. In the forward endcap region of the Belle II detector, particle identification (PID) is performed by the Aerogel Ring Imaging Cherenkov ...(ARICH) counter composed of aerogel tiles and 144-channel Hybrid Avalanche Photo-Detectors (HAPDs). The photon detection efficiency of the photosensor is important for a stable operation of the ARICH. To examine the performance of the HAPDs periodically, a monitor system using scattered photons injected by optical fibers is being developed. In this paper, we report the test using the prototype monitor system and the tests with a partially built ARICH detector.
Abstract
The Aerogel Ring Imaging Cherenkov (ARICH) counter serves as a particle identification device in the forward end-cap region of the Belle II spectrometer. It is capable of identifying pions ...and kaons with momenta up to $4\>$GeV$\>$c$^{-1}$ by detecting Cherenkov photons emitted in the silica aerogel radiator. After the detector alignment and calibration of the probability density function, we evaluate the performance of the ARICH counter using early beam collision data. Event samples of $D^{\ast +} \to D^0 \pi^+ (D^0 \to K^-\pi^+)$ were used to determine the $\pi(K)$ efficiency and the $K(\pi)$ misidentification probability. We found that the ARICH counter is capable of separating kaons from pions with an identification efficiency of $93.5 \pm 0.6 \, \%$ at a pion misidentification probability of $10.9 \pm 0.9 \, \%$. This paper describes the identification method of the counter and the evaluation of the performance during its early operation.
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