Sub-100 nanosecond temporally resolved imaging with the Medipix3 direct electron detector

Detector developments are currently enabling new capabilities in the field of transmission electron microscopy (TEM). We have investigated the limits of a hybrid pixel detector, Medipix3, to record dynamic, time varying, electron signals. Operating with an energy of 60keV, we have utilised electrostatic deflection to oscillate electron beam position on the detector. Adopting a pump-probe imaging strategy we have demonstrated that temporal resolutions three orders of magnitude smaller than are available for typically used TEM imaging detectors are possible. Our experiments have shown that energy deposition of the primary electrons in the hybrid pixel detector limits the overall temporal resolution. Through adjustment of user specifiable thresholds or the use of charge summing mode, we have obtained images composed from summing 10,000s frames containing single electron events to achieve temporal resolution less than 100ns. We propose that this capability can be directly applied to studying repeatable material dynamic processes but also to implement low-dose imaging schemes in scanning transmission electron microscopy.Comment: 11 pages, 6 figures; improve ref formatting + revise tex

Intervención fisioterápica en la acondroplasia

Introducción: la acondroplasia es una enfermedad genética causante de la forma de enanismo más frecuente. Es una alteración de tipo óseo que se caracteriza por un crecimiento disarmónico y desproporcionado del cuerpo, con las extremidades más cortas que el tronco y la cabeza ligeramente más grande. En este trabajo se estudia a una paciente con acondroplasia que padece discapacidades que merman parcialmente sus AVD (actividades de la vida diaria) y le originan una postura que le obliga a usar adaptaciones ortopédicas. Objetivos: se realiza una intervención fisioterápica de carácter preventivo y de reeducación funcional para tratar de corregir algunas de sus anomalías; lograr que consiga una adaptación ergonómica a diferentes objetos, utensilios e infraestructuras que utiliza en su vida diaria; y se trabaja y se entrena la flexibilidad, el tono y la fuerza muscular como fase previa de preparación al alargamiento de las extremidades. Metodología: se valora a la paciente tras aplicar un tratamiento fisioterápico basado en ejercicios de fortalecimiento axial de la columna, ejercicios de tonificación general, estiramientos de las cadenas musculares acortadas, movilizaciones de las articulaciones hipomóviles, RPG (Reeducación Postural Global) método Pilates e higiene postural durante 3 sesiones por 5 semanas. Los ítems valorados y contrastados en relación a la eficacia del tratamiento son: Fuerza muscular general (escala Kendall), tono muscular, flexibilidad, rango articular (goniometría) y postura. Hallazgos: se observa una mejoría en todos los ítems examinados, logrando una mejora postural y del rango de las articulaciones limitadas, así como también una mayor autonomía en las AVD y una disminución del dolor articular. Conclusiones: las técnicas fisioterápicas encaminadas al trabajo postural y el rango articular son herramientas eficientes para mejorar las AVD, prevenir la dependencia de dispositivos ortopédicos y evitar complicaciones neurológicas en el futuro

A Study on Goodwill Accounting Based on the Corporate Competence Theory

在一个多世纪的时间里，商誉问题一直是会计研究领域内极具魅力的主题之一。如今，随着企业的价值创造过程日益依赖于无形资源，随着企业并购市场的日趋扩大，人们对于商誉这个超越了具体产品和服务、提升了企业整体价值的战略性资产日益重视，也更加渴求有关它的高质量会计信息。有关商誉的论述浩如烟海，然而，人们对于商誉的许多问题仍争辩激烈，莫衷一是。本文依据战略管理领域内迅速发展的一种理论——“企业能力论”来对商誉作一系统的研究，希望通过相关学科知识的引入来为商誉研究的发展作出一些贡献。 本文分为八章来进行论述：第一章为引言。第二章进行了系统的文献回顾。第三章介绍了企业能力论，并提出了资源和能力基础的商誉定义，...Since the beginning of last century, goodwill has been an extremely attractive topic in accounting. Nowadays, with the corporate value creation process depending more on intangible resources, and the acquisition and merger market growing dramatically, people pay more attention to goodwill, which overtakes specific product and service and adds to the whole corporate value. Also, people desire for m...学位：管理学硕士院系专业：管理学院会计系_会计学学号：2005130118

Transient Monte Carlo Simulations for the Optimisation and Characterisation of Monolithic Silicon Sensors

An ever-increasing demand for high-performance silicon sensors requires complex sensor designs that are challenging to simulate and model. The combination of electrostatic finite element simulations with a transient Monte Carlo approach provides simultaneous access to precise sensor modelling and high statistics. The high simulation statistics enable the inclusion of Landau fluctuations and production of secondary particles, which offers a realistic simulation scenario. The transient simulation approach is an important tool to achieve an accurate time-resolved description of the sensor, which is crucial in the face of novel detector prototypes with increasingly precise timing capabilities. The simulated time resolution as a function of operating parameters as well as the full transient pulse can be monitored and assessed, which offers a new perspective on the optimisation and characterisation of silicon sensors. In this paper, a combination of electrostatic finite-element simulations using 3D TCAD and transient Monte Carlo simulations with the Allpix Squared framework are presented for a monolithic CMOS pixel sensor with a small collection diode, that is characterised by a highly inhomogeneous, complex electric field. The results are compared to transient 3D TCAD simulations that offer a precise simulation of the transient behaviour but long computation times. Additionally, the simulations are benchmarked against test-beam data and good agreement is found for the performance parameters over a wide range of different operation conditions

Personal Dosimetry in Pulsed Photon Fields with the Dosepix Detector

First investigations regarding dosimetric properties of the hybrid, pixelated, photon-counting Dosepix detector in a pulsed photon field (RQR8) for the personal dose equivalent $H\mathrm{_p(10)}$ are presented. The influence quantities such as pulse duration and dose rate were varied, and their responses were compared to the legal limits provided in PTB-A 23.2. The variation of pulse duration at a nearly constant dose rate of 3.7$\,$Sv/h shows a flat response around 1.0 from 3.6$\,$s down to 2$\,$ms. A response close to 1.0 is achieved for dose rates from 0.07$\,$mSv/h to 35$\,$Sv/h for both pixel sizes. Above this dose rate, the large pixels (220$\,\mathrm{\mu}$m edge length) are below the lower limit. The small pixels (55$\,\mathrm{\mu}$m edge length) stay within limits up to 704$\,$Sv/h. The count rate linearity is compared to previous results, confirming the saturating count rate for high dose rates.Comment: 6 pages, 3 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Ultrafast Radiographic Imaging and Tracking: An overview of instruments, methods, data, and applications

Ultrafast radiographic imaging and tracking (U-RadIT) use state-of-the-art ionizing particle and light sources to experimentally study sub-nanosecond dynamic processes in physics, chemistry, biology, geology, materials science and other fields. These processes, fundamental to nuclear fusion energy, advanced manufacturing, green transportation and others, often involve one mole or more atoms, and thus are challenging to compute by using the first principles of quantum physics or other forward models. One of the central problems in U-RadIT is to optimize information yield through, e.g. high-luminosity X-ray and particle sources, efficient imaging and tracking detectors, novel methods to collect data, and large-bandwidth online and offline data processing, regulated by the underlying physics, statistics, and computing power. We review and highlight recent progress in: a.) Detectors; b.) U-RadIT modalities; c.) Data and algorithms; and d.) Applications. Hardware-centric approaches to U-RadIT optimization are constrained by detector material properties, low signal-to-noise ratio, high cost and long development cycles of critical hardware components such as ASICs. Interpretation of experimental data, including comparisons with forward models, is frequently hindered by sparse measurements, model and measurement uncertainties, and noise. Alternatively, U-RadIT makes increasing use of data science and machine learning algorithms, including experimental implementations of compressed sensing. Machine learning and artificial intelligence approaches, refined by physics and materials information, may also contribute significantly to data interpretation, uncertainty quantification and U-RadIT optimization.Comment: 51 pages, 31 figures; Overview of ultrafast radiographic imaging and tracking as a part of ULITIMA 2023 conference, Mar. 13-16,2023, Menlo Park, CA, US

The Design and Implementation in 0.13μm0.13\mu m CMOS of an Algorithm Permitting Spectroscopic Imaging with High Spatial Resolution for Hybrid Pixel Detectors

Advances in pixel detector technology are opening up new possibilities in many fields of science. Modern High Energy Physics (HEP) experiments use pixel detectors in tracking systems where excellent spatial resolution, precise timing and high signal-to-noise ratio are required for accurate and clean track reconstruction. Many groups are working worldwide to adapt the hybrid pixel technology to other fields such as medical X-ray radiography, protein structure analysis or neutron imaging. The Medipix3 chip is a 256x256 channel hybrid pixel detector readout chip working in Single Photon Counting Mode. It has been developed with a new front-end architecture aimed at eliminating the spectral distortion produced by charge diffusion in highly segmented semiconductor detectors. In the new architecture neighbouring pixels communicate with one another. Charges can be summed event-by-event and the incoming quantum can be assigned as a single hit to the pixel with the biggest charge deposit. In the case where incoming X-ray photons produce fluorescence – a particular issue in high-Z materials – the charge deposited by those fluorescent photons will be included in the charge sum provided that the deposition takes place within the volume of the pixels neighbouring the initial impact point. The chip is configurable such that either the dimensions of each detector pixel match those of one readout pixel or detector pixels are 4 times greate r in area than the readout pixels. In the latter case event-by-event summing is still possible between the larger pixels. The pixel cell occupies an area of $55\mu m x 55\mu m$. It contains an analog front-end and digital processing circuitry. The analog front end consists of a preamplifier, a shaper and two threshold discriminators. The first discriminator is used to define the lower threshold and as input to the arbitration logic when charge summing is enabled. The second discriminator can be used to define a second threshold. Clusters of 4 pixels can be grouped in a single detection unit allowing up to 8 thresholds for energy binning. The digital circuitry contains control logic, arbitration modules for hit allocation, circuitry for storage of the pixel configuration data and two registers that can be configured as two 1-bit, 4-bit or 12 bit counters or as a single 24 bit counter. In 24-bit counting mode only one discrimination level is used and DAQ(write) and readout(read) are sequential. With lower counter depths it is possible to have 2 discrimination levels per pixel in sequential read/write or a single threshold per pixel in continuous read/write. The chip was designed and manufactured in an 8-metal $0.13\mu m$ CMOS technology. It contains ~115M transistors. Measurements show an Equivalent Noise Charge of ~70e- rms (Single Pixel Mode) and ~140e- rms (Charge Summing Mode)

Asic developments for radiation imaging applications: The medipix and timepix family

Hybrid pixel detectors were developed to meet the requirements for tracking in the inner layers at the LHC experiments. With low input capacitance per channel (10–100 fF) it is relatively straightforward to design pulse processing readout electronics with input referred noise of ~100 e-rms and pulse shaping times consistent with tagging of events to a single LHC bunch crossing providing clean ‘images’ of the ionising tracks generated. In the Medipix Collaborations the same concept has been adapted to provide practically noise hit free imaging in a wide range of applications. This paper reports on the development of three generations of readout ASICs. Two distinctive streams of development can be identified: the Medipix ASICs which integrate data from multiple hits on a pixel and provide the images in the form of frames and the Timepix ASICs who aim to send as much information about individual interactions as possible off-chip for further processing. One outstanding circumstance in the use of these devices has been their numerous successful applications, thanks to a large and active community of developers and users. That process has even permitted new developments for detectors for High Energy Physics. This paper reviews the ASICs themselves and details some of the many applications

Design of a monolithic HR-CMOS sensor chip for the CLIC silicon tracker

The CLIC Tracker Detector (CLICTD) is a monolithic active pixel sensor targeted at the tracking detector of a future experiment at the Compact Linear Collider (CLIC). The chip features a matrix of $16 \times 128$ cells, each cell measuring $300 \times 30\,\mu m^{2}$ . The cells are segmented in the long direction in order to maintain the benefits of the small collection electrode. In the digital logic, a simultaneous 8-bit Time of Arrival and 5-bit Time over Threshold measurement is performed. A 180 nm HR-CMOS Imaging Process was selected for the design of a chip that will meet the requirements of the tracker at CLIC. In this document, the CLICTD design and chip interface are presented