Modern Physics Experiments Research Articles

Status of technology of MRPC time of flight system

TOF (Time Of Flight) system based on MRPC (Multi-gap Resistive Plate Chamber) technology is widely used in modern physics experiments, and it also plays an important role in particle identification. With the increase of accelerator energy and luminosity, the TOF system is required to identify definite particles precisely under high rate environment. The MRPC technology TOF system can be defined as three generations. The first generation TOF is based on float glass MRPC and its time resolution is around 80 ps, but the rate is relatively low (typically lower than a few hundred Hz/cm2). The typical systems are TOF of RHIC-STAR, LHC-ALICE and BES III endcap. For the second generation TOF, its time resolution is in the same order with the first generation, but the rate capability is much higher. Its rate capability can reach 30 kHz/cm2. The typical experiment with this high rate TOF is FAIR-CBM. The biggest challenge is on the third generation TOF. For example, the momentum upper limit of K/PI separation is around 7 GeV/c for JLab-SoLID TOF system under high particle rate as high as 20 kHz/cm2, the time requirement is around 20 ps. The readout electronics of the 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 is also designed to analyze the time performance. In this paper, we will describe the evolution of MRPC TOF technology and key technology of each generation TOF.

Detector Monitoring with Artificial Neural Networks at the CMS Experiment at the CERN Large Hadron Collider

Reliable data quality monitoring is a key asset in delivering collision data suitable for physics analysis in any modern large-scale high energy physics experiment. This paper focuses on the use of artificial neural networks for supervised and semi-supervised problems related to the identification of anomalies in the data collected by the CMS muon detectors. We use deep neural networks to analyze LHC collision data, represented as images organized geographically. We train a classifier capable of detecting the known anomalous behaviors with unprecedented efficiency and explore the usage of convolutional autoencoders to extend anomaly detection capabilities to unforeseen failure modes. A generalization of this strategy could pave the way to the automation of the data quality assessment process for present and future high energy physics experiments.

基于微课的近代物理实验教学模式探索

基于微课的近代物理实验教学模式探索

Time of flight technology based on multi-gap resistive plate chamber

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.

Research and Verification of Blackbody Radiation Law

<p>Blackbody radiation theory is one of the important origins of light quantum theory in the twentieth century. It is not only an important basis for quantum mechanics and photonics theory, but also an important conclusion of blackbody radiation, and an important foundation of modern measurement. In the early nineteenth century, the study of thermal radiation was supported by thermodynamics and spectroscopy, and the rapid development of electromagnetism and optics was used. By the end of the 19th century, it was recognized that both the thermal radiation and the optical radiation were electromagnetic waves, and began to study the distribution of radiant energy in different frequency ranges, especially the study of blackbody radiation in theory and practice. Blackbody radiation experiment is one of the contents of modern physics experiment in colleges and universities. This paper mainly studies and validates the law of blackbody radiation by the WGH-10 blackbody experimental device. There is already a calibrated bromine tungsten lamp energy curve at 2940k. At the beginning of the experiment, we should scan at 2940k color temperature to get the baseline, and then calculate the transfer function. Again, the energy curve obtained by scanning at different color temperatures is divided by the transfer function to obtain the correct energy radiation curve. The experimental study of blackbody radiation by computer scanning grating spectrometer and bromine tungsten lamp was carried out. By means of scrolling grating and sine mechanism, the data were recorded by computer scanning to verify the three laws of blackbody radiation directly, and the radiation, transmission and reception of blackbody were analyzed Error correction. </p>

The prototype design of integrated base for PMT with pulse digitalization and readout electronics

High-speed pulse digitalization is critical for modern physics experiments with photomultiplier tubes (PMTs). This prototype design integrates the high-speed analogue to digital converter (ADC) for pulse digitalization, high voltage generator, high-speed buffer, synchronized clock, PoE (Power over Ethernet) power management and ZYNQ SoC (System on Chip) in a compact base which can be mounted with the PMT directly. There is only one category 5 Gigabit Ethernet cable needed for power, data and synchronized timing. This integrated design can be used to replace the conventional readout electronics system with PMTs which use the discrete or integrated pulse shaping circuit and FADC boards based on NIM or VME system. In the applications of several PMTs are used, or in the system where thousands of PMTs are deployed, this prototype design of integrated base for PMT has advantages to simplify the tremendous long distance analogue cables and high voltage cables. This paper presents the mechanical and hardware design, challenges and software design, the ENOB (effective number of bits) of ADC and the TCP data throughput of the Gigabit Ethernet will also be discussed. A scintillator neutron detector mounted with PMTs is connected to this prototype and spectrum analysis with the 137Cs γ source is performed to verify the system function; the preliminary results are also illustrated.

Reform Ideas for the Teaching Practice of Modern Physics Experiment

Modern physics experiment is an important and basic curriculum. It plays an important role in increasing students' ability to resolve and analyze a problem. In view of the problems existing in the teaching of "modern physics experiment" in our university, we put forward some personal suggestions and concrete measures of reformation on the contents, means and management of experiment teaching.

Water purification in low background experiments

Water purification is an important technique in high-mass low radioactivity experiments in modern physics. Water is frequently used both as a shielding and as the sensitive part of a particle detector in underground arrangements, especially in the frame of Astroparticle Physics studies. In this paper, I will describe the main purification techniques and discuss some of its performances.

Characterization of high-temperature performance of cesium vapor cells with anti-relaxation coating

Vapor cells with antirelaxation coating are widely used in modern atomic physics experiments due to the coating's ability to maintain the atoms' spin polarization during wall collisions. We characterize the performance of vapor cells with different coating materials by measuring longitudinal spin relaxation and vapor density at temperatures up to 95 °C. We infer that the spin-projection-noise-limited sensitivity for atomic magnetometers with such cells improves with temperature, which demonstrates the potential of antirelaxation coated cells in applications of future high-sensitivity magnetometers.

Formation of point bars through rising and falling flood stages: Evidence from bar morphology, sediment transport and bed shear stress

ABSTRACTFlow processes and sediment transport in a channel bend and associated point bar have been studied in modern rivers, theoretical models and physical experiments: however, the relationship between flow process and point‐bar morphology has rarely been explained due to the complex nature of open channel flow. Plan‐view exposures of an ancient point‐bar complex, exposed at the top of the Cretaceous Ferron Sandstone Member of the Mancos Shale Formation, south‐central Utah, allowed reconstruction of bar morphology, sediment transport and bed shear stress, which were used to extrapolate flow processes. Studies of these outcrops show that compound point bars and scroll bars were probably formed during falling and rising flood stages, respectively. A simulation model of plan‐view channel form shows that channel dimensions, such as radius of curvature and sinuosity of the point‐bar complex, range between 205 m and 351 m and 1·04 and 1·22, respectively, throughout the evolution of the channel bend. Variations in strength of the helical flow were interpreted as the main control on facies architecture and bar morphology. Strong helical flow was related to the deposition of the scroll bars, while strength of helical flow is decreased for compound bars. The use of cross‐beds as a common palaeocurrent indicator was found to be inconsistent with mean flow directions and channel margin orientation.

Reaching time resolution of less than 10 ps with plastic scintillation detectors

Timing-pick up detectors with excellent timing resolutions are essential in many modern nuclear physics experiments. Aiming to develop a Time-Of-Flight system with precision down to about 10ps, we have made a systematic study of the timing characteristic of TOF detectors, which consist of several combinations of plastic scintillators and photomultiplier tubes. With the conventional electronics, the best timing resolution of about 5.1ps (σ) has been achieved for detectors with an area size of 3×1cm2. It is found that for data digitalization a combination of TAC and ADC can achieve a better time resolution than the currently available TDC. Simultaneous measurements of both time and pulse height are very valuable for the correction of time-walk effect.

A high-throughput readout architecture based on PCI-Express Gen3 and DirectGMA technology

Modern physics experiments produce multi-GB/s data rates. Fast data links and high performance computing stages are required for continuous data acquisition and processing. Because of their intrinsic parallelism and computational power, GPUs emerged as an ideal solution to process this data in high performance computing applications. In this paper we present a high-throughput platform based on direct FPGA-GPU communication. The architecture consists of a Direct Memory Access (DMA) engine compatible with the Xilinx PCI-Express core, a Linux driver for register access, and high- level software to manage direct memory transfers using AMD's DirectGMA technology. Measurements with a Gen3 x8 link show a throughput of 6.4 GB/s for transfers to GPU memory and 6.6 GB/s to system memory. We also assess the possibility of using the architecture in low latency systems: preliminary measurements show a round-trip latency as low as 1 μs for data transfers to system memory, while the additional latency introduced by OpenCL scheduling is the current limitation for GPU based systems. Our implementation is suitable for real-time DAQ system applications ranging from photon science and medical imaging to High Energy Physics (HEP) systems.

Investigation of LaBr3:Ce scintillator with excellent property

In order to satisfy high precision requirement for the modern nuclear physics experiment detectors and radiologic imaging technology equipments, we do some researches in improving the resolution of the detector with LaBr3:Ce scintillator.

Optimizing the quality of silicon strip sensors produced by Infineon Technologies Austria AG

The tracking systems of most modern particle physics experiments are realized by silicon based sensors. The size of such systems has continuously increased and nowadays a sensitive area of several 100 m2 has to be covered. This large amount of sensors might exceed the production capabilities of existing companies and institutes. Therefore the Institute of High Energy Physics of the Austrian Academy of Sciences (HEPHY) and the European semiconductor manufacturer Infineon Technologies Austria AG developed together a production process for p-on-n strip sensors.Although the first prototype run has shown a promising quality, it has been observed that weak strips exist, which are mainly located at distinctive areas on each wafer. At these areas the affected parameters are correlated to each other. A similar behaviour could be reproduced with a smaller second batch, whose sensors have been used for further analysis and advanced measurements.This paper sums up the characteristic behaviour of the specific effect and presents different possibilities how to cure the sensors. The systematic accumulation of weak strips can be traced back to a specific operation during the fabrication process. All data strongly indicate that the effect is caused by local charging effects on an isolating layer.

Efficient, reliable and fast high-level triggering using a bonsai boosted decision tree

High-level triggering is a vital component of many modern particle physics experiments. This paper describes a modification to the standard boosted decision tree (BDT) classifier,the so-called bonsai BDT, that has the following important properties: it is more efficient than traditional cut-based approaches; it is robust against detector instabilities,and it is very fast. Thus, it is fit-for-purpose for the online running conditions faced by any large-scale data acquisition system.

Spin–orbit induced electronic spin separation in semiconductor nanostructures

The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin–orbit interaction in an InGaAs-based heterostructure. Using a Stern–Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 108 T m−1 resulting in a highly polarized spin current.

Computer-Aided Modern Physics Experiment

In order to better adapt to the modern physics experiments under intelligent conditions, we examined a number of modern physics experiment the intelligent way from data acquisition and processing and concluded: Data collection can be attributed to two ways, one way is by means of computer device (such as sound card) to receive data, another way to install the data acquisition card (or frame grabber), moreover to install device driver in the computer; Modern experimental data processing is the main purpose of the intelligentization, with special software, fast data processing, and giving visual results. The results contribute to a better use of computer-based modern physics experiments.

Combination of the Research-Based Learning Method with the Modern Physics Experiment Course Teaching

It has been the hotspot to reconstruct the education course based on the research-based learning in the course reform in many countries in recent years. The new course standard of China insists that the teaching is the interactive process that teachers and students communicate and develop together. In the teaching, the relationship between imparting knowledge and cultivating ability, and students’ independence and self-determination should be emphasized, and teachers should lead students to doubt, survey, and search, and learn in the practice, and the learning should be the active and individual process under teachers’ instruction. The exploring learning is just based on cultivating students’ innovational spirit and practice ability. The research-based learning is introduced in the teaching of the modern physics experiment course, and this article mainly explores and attempts the concrete implementation and case design.

Very high dynamic range and high sampling rate VME digitizing boards for physics experiments

The trend in data acquisition systems for modern physics experiments is to digitize analog signals closer and closer to the detector. The digitization systems have followed the progress of commercial analog to digital converters. The state of the art for these devices is currently 225 MSample/s for a 10 to 12 bit range. The new boards, described in this paper, have been designed to improve these performances by an order of magnitude. In its simplest version, this board mainly includes 4 channels sampling analog data up to 2 GSample/s with an analog bandwidth of 300 MHz, and digitizing it with a 12-bit dynamic range. It is based on the custom-designed MATACQ chip. The latter's innovative design permits reaching these performances with power consumption smaller than 1 W. The boards are triggerable either by internal or external signals and several boards are easily synchronizable. The board integrates both GPIB and VME interfaces that permit a maximum readout speed of 500 events/s with the whole memory depth of the 4 channels read

Trends in physics data analysis algorithms

The paper provides a new look at algorithmic trends in modern physics experiments. Based on recently presented material, it attempts to draw conclusions in order to form a coherent historical picture of the past, present, and possible future of the field of data analysis techniques in physics. The importance of cross disciplinary approaches is stressed.