GaN-Based Bipolar Cascade Lasers with 25nm Wide Quantum Wells

Utilizing self-consistent numerical simulation in good agreement with measurements, we analyze internal device physics, performance limitations, and optimization options for a unique laser design with multiple active regions separated by tunnel junctions, featuring surprisingly wide InGaN quantum wells. Contrary to common assumptions, these quantum wells are revealed to allow for perfect screening of the strong built-in polarization field, while optical gain is provided by higher quantum levels. However, internal absorption, low p-cladding conductivity, and self-heating are shown to strongly limit the laser performance.

A program to drive the ATLAS Local Trigger Interface (ALTI) at the ATLAS experiment

During the High Luminosity upgrade of the Large Hadron Collider at CERN, the LHC experiments will undergo a series of upgrades in order to maintain high physics performance following an increased data rate. The largest Phase 1 upgrade project at the ATLAS muon system is the replacement of the current inner station (end-cap regions) with the New Small Wheels. In addition, the ATLAS Local Trigger Interface (ALTI), a part of the Timing, Trigger and Control (TTC) system, will replace the four existing TTC modules. In normal operation, the detectors, along with the surrounding electronics, will receive TTC related signals from the Central Trigger Processor (CTP). This information is forwarded to the front-end electronics of each of the ATLAS sub-detectors through an optical network via the ALTI. The interface currently produces an artificially generated pulse pattern that contains the TTC information. This paper will summarize the creation of a program that generates pulse pattern files which are used to drive ALTI. Various tests have been conducted in order to study the performance of the NSW trigger electronics while using these files. Software development and data analysis using ROOT framework were used to validate the results of these tests.

Preliminary Multi-Physics Performance Analysis and Design Evaluation of UO2 Fuel for LBE-Cooled Subcritical Reactor of China Initiative Accelerator Driven System

The China initiative Accelerator Driven System (CiADS) and the corresponding lead-bismuth eutectic (LBE) cooled subcritical reactor, as the research subject of one of the major national science and technology infrastructure projects, are undertaken by the Institute of Modern Physics-Chinese Academy of Sciences (IMP-CAS). And in the first phase, UO2 fuels will be loaded in the subcritical core to test the coupling technology and achieve a long-term steady operation. A brief description of CiADS subcritical reactor, fuel assembly and fuel element are presented here, and a multi-physics performance analysis and design evaluation of CiADS UO2 fuel are carried out by means of the FUTURE code. FUTURE is a fuel performance analysis code to evaluate the synergy of phenomena occurring in the fuel element and their impact on the fuel design improvement for the liquid metal fast reactor, which was developed jointly by IMP-CAS and Xi’an Jiaotong University (XJTU). In this paper, the FUTURE code was modified and updated focusing on characteristics of CiADS fuels. Relocation and densification models were added. Results of the hottest fuel element, mainly concerning the thermo-mechanical behaviors, are discussed concerning both fuel and cladding performance on the basis of indicative design limits. According to the preliminary design, the CiADS UO2 fuel exhibits good performance, and the main safety parameters are far below the indicative limits. The Fuel Cladding Mechanical Interaction (FCMI) is not very serious, and the permanent cladding strains and Cumulative Damage Fraction (CDF) are small and even negligible thanks to the low level of fuel temperature and corresponding stress. However, some critical issues may still exist, especially on LBE corrosion near the coolant inlet, where protective oxide layers are very thin from BoL to EoL. The modeling is useful for providing feedback to the conceptual design of the CiADS LBE-cooled subcritical reactor and the update of FUTURE code.

CMS Full Simulation for Run 3

We report the status of the CMS full simulation for Run 3. During the long shutdown of the LHC a significant update has been introduced to the CMS code for simulation. The CMS geometry description is reviewed. Several important modifications were needed. CMS detector description software is migrated to the DD4Hep community developed tool. We will report on our experience obtained during the process of this migration. Geant4 10.7 is the CMS choice for Run 3 simulation productions. We will discuss arguments for this choice, the strategy of adaptation of a new Geant4 version, and will report on the physics performance of the CMS simulation. A special Geant4 Physics List configuration FTFP_BERT_EMM will be described, which provides a compromise between simulation accuracy and CPU performance. A significant fraction of time for simulation of CMS events is spent on tracking of charged particles in a magnetic field. In the CMS simulation a dynamic choice of Geant4 parameters for tracking in field is implemented. A new method is introduced into simulation of electromagnetic components of hadronic showers in the electromagnetic calorimeter of CMS. For low-energy electrons and positrons a parametrization of GFlash type is applied. Results of tests of this method will be discussed. In summary, we expect about 25% speedup of the CMS simulation production for Run 3 compared to the Run 2 simulations.

Key4hep: Status and Plans

Detector optimisation and physics performance studies are an integral part of the development of future collider experiments. The Key4hep project aims to design a common set of software tools for future, or even present, High Energy Physics projects. The proceeding describes the main components that are developed as part of Key4hep: the event data model EDM4hep, simulation interfaces to Delphes and Geant4, the k4MarlinWrapper to integrate iLCSoft components, as well as build and validation tools to ensure functionality and compatibility among the components. They also include the different adaptation processes by the CEPC, CLIC, FCC, and ILC communities towards this project, which show that Key4hep is a viable long term solution as baseline software for high energy experiments.