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Instruments / Technical Area	Publication Details	Published
I12-JEEP: Joint Engineering, Environmental and Processing	Mechanistic insights into the initial explosion in the deflagration-to-detonation transition Trevor A. Feagin , Eric M. Heatwole , David S. Eastwood , Ian Lopez-Pulliam , Thomas Connolley , Neil K. Bourne , Gary Parker Combustion And Flame 242 DOI: 10.1016/j.combustflame.2022.112175 Diamond Proposal Number(s): [22393] Show Abstract ▼ Abstract: This work presents an imaging study of the complex and often overlooked early-onset mechanisms of the deflagration-to-detonation transition (DDT). Columns of granular octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) doped with tungsten tracer particles are ignited thermally by hot wire and the resulting reactions are studied via high-speed X-ray radiography utilizing the Diamond Light Source synchrotron. The observed results provide insights into the initial development of the DDT process, resulting in a proposed mechanism for the slow initial steps in DDT for thermally ignited, low bulk-density granular explosive contained in a quasi-one dimensional tube configuration. In order to clarify the proposed mechanism, the terms preferential flow channel and matrix burning are adapted from the soil mechanics and hydrology literature to further elucidate the role of convective burning in DDT. The proposed mechanism helps to clarify the ongoing debate on the transport of gases in the Baer–Nunziato and reduced Baer–Nunziato models and suggests that applicability of each interpretation depends on which step in the mechanism is being described.	Aug 2022
I13-2-Diamond Manchester Imaging	4D micro-scale, phase-contrast X-ray imaging and computed tomography of HMX-based polymer-bonded explosives during thermal runaway G. R. Parker , D. S. Eastwood , M. Storm , K. Vitharana , E. M. Heatwole , I. Lopez-Pulliam , R. M. Broilo , P. M. Dickson , A. Martinez , Christoph Rau , N. K. Bourne Combustion And Flame 226, 478 - 489 DOI: 10.1016/j.combustflame.2020.12.025 Diamond Proposal Number(s): [15068, 16650, 18198] Show Abstract ▼ Abstract: High-resolution synchrotron x-ray radiography with computed tomography is used to observe the evolution of porosity created by thermal exposure in two HMX-based polymer-bonded explosive compositions; LX-04 and BX-63. The measurements were made in situ, over an extended period of time, during which the samples were heated on a slow-rate thermal trajectory. The tests ended with thermal-runaway to ignition after which the samples were consumed by combustion. The primary means of damage appears to be from mechanical debonding of the HMX-binder interface with secondary contribution from chemical decomposition. Confinement and binder properties affect the amount of porosity and permeability that develops. Additionally, observations were made describing the emergence and structure of an internal ignition volume, the formation and transport of a pre-ignition melt layer, and how the early stages of combustion were affected by material morphology, mechanical confinement and melt. The contact angle between molten HMX and the fluoropolymer, Viton A, is also presented. For the first time we have time-resolved x-ray images of ignition in sufficient detail to verify the mechanism of cookoff in polymer-bonded explosive compositions.	Apr 2021
I12-JEEP: Joint Engineering, Environmental and Processing	The transit to detonation in high explosives N. K. Bourne , D. E. Eastwood , S. Marussi , G. Parker , P. M. Dickson , R. C. Atwood , T. Connolley , A. Martinez , D. Wagstaff Shock Compression of Condensed Matter - 2019 DOI: 10.1063/12.0000904 Diamond Proposal Number(s): [19556] Open Access Show Abstract ▼ Abstract: Accidents with explosive materials are still too common over 150 years after the patenting of dynamite. The manner by which they transit from burn to detonation (Deflagration to Detonation Transition; DDT) after a random thermal event, such as an electrical arc, or by friction if a package is dropped, is by far the single biggest risk associated with explosives storage and use. However this is a particularly difficult process to observe and quantify. Thus there are no agreed and verified theoretical frameworks for the process and thus no comprehensive predictive modelling capabilities. Recent experiments conducted at the Diamond Synchrotron have yielded ground-breaking, time-resolved observations of DDT. They have pioneered new experimental techniques and opened a new area for fast imaging at synchrotrons. We illustrate critical processes that occur within burning to detonation revealed in this study. These provide a new framework for understanding processes operating and offer the means to handle this class of materials more safely.	Nov 2020

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