External-cavity mode-locked quantum-dot laser diodes for low repetition rate, sub-picosecond pulse generation

This paper presents an investigation of the mode-locking performance of a two-section external-cavity mode-locked InGaAs quantum-dot laser diode, focusing on repetition rate, pulse duration and pulse energy. The lowest repetition rate to-date of any passively mode-locked semiconductor laser diode is demonstrated (310 MHz) and a restriction on the pulse energy (at 0.4 pJ) for the shortest pulse durations is identified. Fundamental mode-locking from 310 MHz to 1.1 GHz was investigated, and harmonic mode-locking was achieved up to a repetition rate of 4.4 GHz. Fourier transform limited subpicosecond pulse generation was realized through implementation of an intra-cavity glass etalon, and pulse durations from 930fs to 8.3ps were demonstrated for a repetition rate of 1 GHz. For all investigations, mode-locking with the shortest pulse durations yielded constant pulse energies of ∼0.4 pJ, revealing an independence of the pulse energy on all the mode-locking parameters investigated (cavity configuration, driving conditions, pulse duration, repetition rate, and output power). © 2011 IEEE.

Switching characteristics of diamond-based m-i-p+ diodes in power electronic applications

Modeling and numerical analysis of diamond m-i-p+ diode have been performed for static and transient analysis using TCAD Sentaurus platform. The simulation results are compared with experimental measurements. Prediction of transient turn-off characteristics of diamond m-i-p+ diode at high temperature is performed for the first time. It was found that unlike conventional Si diode, peak reverse current in diamond m-i-p+ diode reduces with increasing temperature while on-state voltage drop increases. © 2011 IEEE.

The mechanical integrity of fuel pin cladding in a pulsed-beam accelerator driven subcritical reactor

The Accelerator Driven Subcritical Reactor (ADSR) is one of the reactor designs proposed for future nuclear energy production. Interest in the ADSR arises from its enhanced and intrinsic safety characteristics, as well as its potential ability to utilize the large global reserves of thorium and to burn legacy actinide waste from other reactors and decommissioned nuclear weapons. The ADSR concept is based on the coupling of a particle accelerator and a subcritical core by means of a neutron spallation target interface. One of the candidate accelerator technologies receiving increasing attention, the Fixed Field Alternating Gradient (FFAG) accelerator, generates a pulsed proton beam. This paper investigates the impact of pulsed proton beam operation on the mechanical integrity of the fuel pin cladding. A pulsed beam induces repetitive temperature changes in the reactor core which lead to cyclic thermal stresses in the cladding. To perform the thermal analysis aspects of this study a code that couples the neutron kinetics of a subcritical core to a cylindrical geometry heat transfer model was developed. This code, named PTS-ADS, enables temperature variations in the cladding to be calculated. These results are then used to perform thermal fatigue analysis and to predict the stress-life behaviour of the cladding. © 2011 Elsevier Ltd. All rights reserved.

The effect of beam interruptions on the integrity of ADSR fuel pin cladding: A thermo-mechanical analysis

During its lifetime in the core, the cladding of an Accelerator Driven Subcritical Reactor (ADSR) fuel pin is expected to experience variable stresses due to frequent interruptions in the accelerator proton beam. This paper investigates the thermal fatigue damage in the cladding due to repetitive and unplanned beam interruptions under certain operational conditions. Beam trip data was obtained for four operating high power proton accelerators, among which the Spallation Neutron Source (SNS) superconducting accelerator was selected for further analysis. 9Cr-1Mo-Nb-V (T91) steel was selected as the cladding material because of its proven compatibility with proposed ADSR design concepts. The neutronic, thermal and stress analyses were performed using the PTS-ADS, a code that has been specifically developed for studying the dynamic response to beam-induced transients in accelerator driven subcritical systems. The lifetime of the fuel cladding in the core was estimated for three levels of allowed pin power and specific operating conditions. © 2012 Elsevier Ltd. All rights reserved.

FPGA, physics-based modeling of IGBT and pin diode for hardware co-simulation of complex power electronic converters and systems

This paper presents the steps and the challenges for implementing analytical, physics-based models for the insulated gate bipolar transistor (IGBT) and the PIN diode in hardware and more specifically in field programmable gate arrays (FPGAs). The models can be utilised in hardware co-simulation of complex power electronic converters and entire power systems in order to reduce the simulation time without compromising the accuracy of results. Such a co-simulation allows reliable prediction of the system's performance as well as accurate investigation of the power devices' behaviour during operation. Ultimately, this will allow application-specific optimisation of the devices' structure, circuit topologies as well as enhancement of the control and/or protection schemes.

The effects of operational and design parameters on the tolerance of ADSR fuel pin cladding to beam interruptions

This paper investigates the effects of design parameters, such as cladding and coolant material choices, and operational phenomena, such as creep and fission product decay heat, on the tolerance of Accelerator Driven Subcritical Reactor (ADSR) fuel pin cladding to beam interruptions. This work aims to provide a greater understanding of the integration between accelerator and nuclear reactor technologies in ADSRs. The results show that an upper limit on cladding operating temperature of 550 °C is appropriate, as higher values of temperature tend to accelerate creep, leading to cladding failure much sooner than anticipated. The effect of fission product decay heat is to reduce significantly the maximum stress developed in the cladding during a beam-trip-induced transient. The potential impact of irradiation damage and the effects of the liquid metal coolant environment on the cladding are discussed. © 2013 Elsevier Ltd. All rights reserved.