A high rate and precise timing photo-RPC with low-resistivity float glass

Two Multigap Resistive Plate Chambers (MRPCs) were built with thin (0.4 mm) low-resistive glass sheets for the inner plates and standard 0.28 mm ‘soda lime’ float glass as external plates. The 6-gap MRPC reaches 96.5% efficiency at 15.6 kV and a time resolution of 68 ps at an instantaneous particle flux around 2.5 kHz/cm 2 . The 20-gap MRPC reaches 98% efficiency at 18.8 kV and a time resolution of 32 ps. Compared to a 6-gap MRPC built previously with all plates made with soda-lime float glass, the two MRPCs made with low-resistive inner glass show a much higher count rate capability. A third MRPC with all plates made from low-resistive glass was also constructed to verify the operation at high particle flux. In this paper a relative rate capability comparison between the MRPCs has been performed under a pulsed beam with a small spot on the chamber. Their rate capability under full illumination with continuous particle flux needs to be further studied.

Multi-gap Resistive Plate Chambers (MRPC) has been used to construct time-of-flight system in the field of nuclear and particle physics, due to their high-precision timing properties, high efficiency, reliability and coverage of large area. With the increase of accelerator luminosity, MRPCs have to withstand particle fluxes up to several tens of kHz/cm2 in view of the next generation physics experiments, such as the SIS-100/300 at FAIR-CBM, SoLID at JLab and NICA at JINR. But the MRPC assembled with float glass has very low rate capability not exceeding some hundreds of Hz/cm2. Two possible solutions for increasing rate capability, one is to reduce the bulk resistivity of glass and the other is to reduce the electrode thickness. Tsinghua University has done R&D on high rate MRPC for many years. A special low resistive glass with bulk resistivity around 1010Ω.cm was developed. We also studied the rate capability changes with glass thickness. In this paper we describe the performance of low resistive glass and two kinds of high rate MRPC (Pad readout and Strip readout) tested by deuterium beams. The results show that the tolerable particle flux can reach 70 kHz/cm2. In the mean time, MRPCs assembled with three thickness (0.7 mm, 0.5 mm and 0.35 mm) of float glass were also tested with deuteron beams, the results show that the three detectors can afford particle rate up to 500 Hz/cm2, 0.75 kHz/cm2 and 3 kHz/cm2, respectively.

Multigap Resistive Plate Chambers (MRPCs) are often used as time-of-flight (TOF) detectors for high-energy physics and nuclear experiments thanks to their excellent time accuracy. For the Compressed Baryonic Matter (CBM) TOF system, MRPCs are required to work at particle fluxes on the order of 1–10kHz/cm2 for the outer region and 10–25kHz/cm2 for the central region. Better time resolution will allow particle identification with TOF techniques to be performed at higher momenta. From our previous studies, a time resolution of 25ps has been obtained with a 20-gap MRPC of 140μm gap size with enhanced rate capability. By using a new type of commercially available thin low-resistivity glass, further improvement MRPC rate capability is possible. In order to study the rate capability of the 10-gap MRPC built with this new low-resistivity glass, we have performed tests using the continuous electron beam at ELBE. This 10-gap MRPC, with 160μm gaps, reaches 97% efficiency at 19.2kV and a time resolution of 36ps at particle fluxes near 2kHz/cm2. At a flux of 100kHz/cm2, the efficiency is still above 95% and a time resolution of 50ps is obtained, which would fulfil the requirement of CBM TOF system.

A thin float glass MRPC for the outer region of CBM-TOF wall

For precise start time determination a Beam Fragmentation T0 Counter (BFTC) is under development for the Time-of-Flight Wall of the Compressed Baryonic Matter Spectrometer (CBM) at the Facility for Antiproton and Ion Research (FAIR) at Darmstadt/Germany. This detector will be located around the beam pipe, covering the front area of the Projectile Spectator Detector. The fluxes at this region are expected to exceed 105cm−2s−1. Resistive plate chambers (RPC) with ceramic composite electrodes could be use because of their high rate capabilities and radiation hardness of material. Efficiency ≥ 97 %, time resolution ≤ 90 ps and rate capability ≥ 105cm−2s−1 were confirmed during many tests with high beam fluxes of relativistic electrons. We confirm the stability of these characteristics with low resistive Si3N4/SiC floating electrodes for a prototype of eight small RPCs, where each of them contains six gas gaps. The active RPC size amounts 20×20 mm2 produced on basis of Al3O2 and Si3N4/SiC ceramics. Recent test results obtained with relativistic electrons at the linear accelerator ELBE of the Helmholtz-Zentrum Dresden-Rossendorf with new PADI-10 Front-end electronic will be presented.

Beam test results of high counting rate MRPCs at GSI

In evoked potential testing, it is common practice to abrade the skin surface as a means of reducing and balancing electrode impedance. The effects of skin preparation and electrode impedance on ocular vestibular-evoked myogenic potential (oVEMP) prevalence and amplitudes are not known. We sought to determine whether comparable oVEMP waveforms could be recorded without excessive skin preparation. This was a prospective study with a repeated-measures (within-subjects) design. The study group comprised 20 healthy participants (12 females and 8 males) ages 21-57 yr. oVEMP reflexes were recorded in response to air-conducted and bone-conducted (AC and BC) stimuli in three conditions. In the first condition (no skin preparation), electrodes were simply placed over the skin surface. For the second condition (moderate skin preparation), oVEMP testing was repeated after the skin had been prepared with 70% isopropyl alcohol swabs. oVEMPs recorded in these two conditions were then compared with those recorded using a third conventional protocol whereby the skin was abraded with skin preparation gel until electrode impedances were low and balanced. For BC stimuli, reflex amplitudes and latencies were compared using a repeated-measures general linear model. For AC stimuli, rates of reflex detection were analyzed using a generalized estimating equation. Nonparametric Friedman tests were used to compare AC oVEMP amplitudes across the three conditions. There was no significant effect of electrode impedance on reflex amplitudes, latencies, or rates of detection (p > 0.05). The results indicated significant stimulus-related artifact (≥3 μV) in 25 of 40 recordings under the high-impedance condition in response to BC stimulation. The stimulus artifact was detectable in 12 of 40 recordings after moderate skin preparation and in 5 recordings after skin abrasion. Comparable rates of reflex detection and oVEMP amplitudes were recorded in the three conditions, implying that rigorous rubbing of the facial skin is largely unnecessary in clinical oVEMP testing. However, for oVEMPs recorded in response to a single-polarity stimulus, reducing and balancing electrode impedances with either isopropyl alcohol wipes or skin abrasion may help reduce unwanted stimulus artifact.

The resistivity of conventional glass is quite high and is unacceptable in a high rate environment. Low resistive glass-electrodes could be a solution for this problem. The present study reports the e+/e− simulation results of an RPC detector made from low resistive phosphate glass electrodes. The detailed geometrical configuration of the content materials which are the essential components of the glass of the RPC detector have been created with the GEANT4 simulation code. Two different types of particle sources, i.e. for e+/e−, have been located on the detectors surface to evaluate the performance of the phosphate glass RPC. Both of the particles have been simulated as a function of their respective energies in the range of 0.1 MeV − 1.0 GeV. The present simulation work has shown that the resistive electrode plays an important role for the particle production in the RPC configuration.

For the production of time-resolved spark spectra, an electronically controlled source operating with a high precision in time is necessary. The high operational precision of the spark source with double controlling spark gaps is, on the one hand due to the spark gaps being electrically prestressed, and on the other hand to the transient wave arising at the breakdown of spark gaps. A further condition for the high operational precision in time is the adequate preionization of the spark gaps. A spark frequency higher than mains frequency may be realized by using a saturated iron-cored transformer to give complete separation of the charging and discharging processes. To illustrate time-resolved spectrochemical analysis, the separation of the background of the spark spectrum was carried out by means of a rotating disk placed before the slit of the spectrograph. Owing to the separation of the background the working curve obtained is a straight line even in the case of small percentage contents, and the sensitivity may be increased.

Electrochemical Impedance Spectroscopy (EIS) with Transmission Line Model (TLM) was utilized to study the electrochemical capacitive performance in a three dimensional hierarchical carbon network with hollow core and mesoporous shell (HCMS) structure in KOH electrolyte. In order to systematically study the performance-structure relationship, the shell thickness (S) of the HCMS structure was stepwise increased from S=0 to 100 nm while other geometric parameters were kept constant. Nyquist plots were presented and fitted with Transmission line models. Ion transportation through the HCMS hierarchical structure, RC time constants and capacitance distribution across the carbon electrodes were derived from the 6-loop TLM. The stepwise increased shell thickness (S) of the HCMS structure affects both the electrochemical and physical properties of the carbon electrodes, for example, the electrode resistance, diffusion resistance, capacitance, and rate capability. TLM demonstrated that major capacitance were contributed from the second to fourth loop, which can be associated to the mesoporous shell region in the HCMS texture; while the 5th loop is associated to the diffusion of ions into micropores. Though the carbon with thicker shells can provide large specific capacitance, the rate capability (determined by RC time constants) worsens, no direct stepwise relationship was observed for increased shell thickness.

An improved microelectrode resistance meter

Particle identification is very important in nuclear and particle physics experiments. Time of flight system (TOF) plays an important role in particle identification such as the separation of pion, kaon and proton. Multi-gap resistive plate chamber (MRPC) is a new kind of avalanche gas detector and it has excellent time resolution power. The intrinsic time resolution of narrow gap MRPC is less than 10 ps. So the MRPC technology TOF system is widely used in modern physics experiments for particle identification. With the increase of accelerator energy and luminosity, the TOF system is required to indentify definite particles precisely under high rate environment. The MRPC technology TOF system can be defined as three generations according to the timing and rate requirement. The first-generation TOF is based on the float glass MRPC and its time resolution is around 80 ps, but the rate is relatively low (typically lower than 100 Hz/cm<sup>2</sup>). The typical systems are TOF of RHIC-STAR, LHC-ALICE and BES III endcap. For the second-generation TOF, its time resolution has the same order as that for the first generation, but the rate capability is much higher. Its rate capability can reach 30 kHz/cm<sup>2</sup>. The typical experiment with this high rate TOF is FAIR-CBM. The biggest challenge is in the third-generation TOF. For example, the momentum upper limit of <inline-formula><tex-math id="M1">\begin{document}$ {\rm{K}}/{\text{π}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20182192_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20182192_M1.png"/></alternatives></inline-formula> separation is around 7 GeV/c for JLab-SoLID TOF system under high particle rate as high as 20 kHz/cm<sup>2</sup>, and the time requirement is around 20 ps. The readout electronics of first two generations is based on time over threshold method, and pulse shape sampling technology will be used in the third-generation TOF. In the same time, the machine learning technology LSTM network is also used to analyze the time performance. As a very successful sample, MRPC barrel TOF has been used in RHIC-STAR for more than ten years and many important physics results have been obtained. A prominent result is the observation of antimatter helium-4 nucleus. This discovery proves the existence of antimatter in the early universe. In this paper, we will describe the evolution of MRPC TOF technology and key technology of each generation of TOFs including MRPC detector and related electronics. The industrial and medical usage of MRPC are also introduced in the work finally.

Nickel and manganese-based layered oxides with a nickel content ranging from 50% to 80% are promising cathode materials for high-energy density lithium-ion batteries. However, these materials face challenges such as poor rate capability and limited cycling stability. The addition of excess lithium can mitigate these issues to some extent. This study examines the impact of incorporating small amounts of cobalt (5% or 10%) into these materials through an “all-dry” synthesis approach in stoichiometric and excess lithium-containing compositions. Results indicate that adding even these small amounts of cobalt decreases the cation mixing, improves crystallinity, reduces electronic resistance, and influences the morphology depending on whether nickel or manganese is replaced. The materials can accommodate up to 15% excess lithium without significant surface impurities. The addition of cobalt further enhances the rate capability of the material in excess lithium materials, but increasing cobalt content tends to compromise cycling stability when the materials are cycled up to 4.4 V. Materials in which 5% cobalt replaces nickel still exhibit superior rate capability and cycling performance compared to materials without cobalt. Therefore, incorporating small amounts of cobalt can positively impact the performance of Li1+x(Ni0.6Mn0.4)1−xO2 materials, offering a balance between improved rate capability and cycling stability.

Spectra dispersed only according to wavelength have a limited physical meaning since they fail to reveal the changes in the light source in time. Electronically controlled spectroscopic light sources operating with high precision in time make possible the production of time-resolved spectra, which can be represented as a function of wavelength and time. Resolution in time is accomplished with the aid of rotating mirrors and disks, fitted in the optical system of conventional spectrographs. The time-revolving element and the light source are synchronized magnetically or by means of a photocell. The light source is controlled by a trigger signal generator driven by a photocell or a magnetic coil. The rotating mirror or disk, driven by a synchronous motor from the mains voltage, is incorporated in a mechanical apparatus, making possible electric phase adjustments. Several details of time-resolved spectra of high- and low-voltage sparks and of ac arcs are demonstrated.

Time-resolved experiments often need detection devices able to provide information about position and arrival time of each detected event. Cross Delay-Lines detectors (CDL), which use arrival time information also for position detection, are the most suited instruments for this task and time resolution is a fundamental requirement, along with the high versatility and fast real-time computing. Typical acquisition architectures, based on Time-to-Digital Converters (TDC) followed by a Field Programmable Gate Array (FPGA), combine very fast parallel computing with a high time precision, allowing to perform state-of-the-art time-resolved experiments. In these devices, time precision as much as time accuracy are fundamental in order to guarantee a homogenous time-to-space conversion. Nevertheless, time resolution is still a limiting factor when time resolved experiments are associated to imaging.In 2017 at Nuclear Science Symposium, inside ″Development of fully FPGA-based 3D (X, Y, t) detection systems using multichannel Tapped Delay-Line Time-to-Digital Converter with Cross Delay-Line detectors″ we presented a new approach, combining FPGA-based multi-channel TDC and an efficient multipurpose readout logic addressed to CDL detector. In this contribution, thanks to the modularity and reconfigurability offered by the FPGA, we redesigned the firmware that describes the TDC increasing the resolution from 10 ps to 1 ps, the channel precision from 15 ps r.m.s. to 9.7 ps r.m.s. and, reducing the accuracy from 200 ps to 40 ps.As result, we have greatly improved the overall performance and versatility of CDL detector systems allowing image acquisition with spatial precision better than 30 μm.These make possible the application in a multidisciplinary research center like the Elettra and FERMI lightsources where electron analyzers and Time-of-Flight devices endowed with CDL detectors allow very high spatial and time resolved spectroscopy experiments.