High energy density plasma physics experiments are required to validate computer simulations in the absence of nuclear testing[
High Power Laser Science and Engineering, Volume. 5, Issue 4, 04000e28(2017)
X-ray computed tomography of adhesive wicking into carbon foam
Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together. In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray computed tomography (CT) and image processing software have been utilized. Two different laser target configurations have been assessed
1 Scope
High energy density plasma physics experiments are required to validate computer simulations in the absence of nuclear testing[
2 Experimental
Two different types of laser target assemblies, produced at Atomic Weapons Establishment (AWE), were analysed using the Xradia™ micro-XCT 200 system. The optimizations of X-ray CT parameters used for this assessment are documented. X-ray CT data were image processed in the ScanIP software environment (Synopsys, Exeter, UK) to determine the quantity of adhesive and to produce volumetric rendered images.
Each target consisted of three different materials: carbon foam, polythene holder and adhesive. The carbon foam was precision machined into a cylindrical form using precision diamond turning lathe (Precitech) and the polythene holder was milled using a Kern EVO. The target components were assembled together using the assembly station and the adhesive applied around the circumference of the carbon foam, as shown in Figure
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The target assemblies were mounted onto the X-ray CT mount as shown in Figure
All three materials have a similar X-ray opacity prompting the use of phase contrast geometry rather than the standard absorption mode. The X-ray CT system used for imaging was equipped with phase contrast and standard absorption mode capability. Phase contrast was achieved on the Xradia™ micro-XCT 200 system by increasing the sample to source and sample to detector distances (Tables
The X-ray CT data was obtained using the Xradia™ Micro-XCT 200 CT system shown in Figure
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Scan IP image processing software was then used to analyse the X-ray CT data. Voxels were created with attenuation and density data in all three dimensions (
3 Results and discussion
3.1 Sample A – cylindrical support
X-ray CT sections of Sample A are given in Figures
Figure
3.2 Sample B – cubic support
X-ray CT sections of Sample B are given in Figures
3.3 Adhesive distribution
The adhesive distribution within Samples A and B are shown in Figures
The volume of adhesive associated with Sample A was
The accuracy of the measurements is dependent on a number of factors associated with the X-ray CT hardware, reconstruction and image processing software. X-ray CT hardware error factors include source stability, detector characteristics and geometrical errors associated with source, detector and rotation stage. Operator parameters include the selection of suitable accelerating voltage (kV) of the X-ray tube which determines the X-ray energies current
It is important at this time to know the extent of the wicking of the adhesive into the pores of the foam as this can then be compensated for in the physics models used to support the understanding of the target once shot in a laser facility.
4 Conclusion
It has been successfully demonstrated that X-ray tomography is a viable nondestructive method for assessing both internal and external surfaces for a multimaterial adhesively bonded target assembly.
The complex distribution of adhesive into carbon foams was investigated for two samples. Volume-rendered images determined the quantities and distribution of the adhesive. The extent of wicking was found to be similar for the two samples; in both cases, adhesive was not present toward the bottom edges in the deeper sections of the carbon foam. The central region of the carbon foam is adhesive free, providing reassurance that experimental design is not compromised.
The combination of X-ray tomography and image processing provides an effective tool for assessing the suitability of adhesively bonded multicomponent targets for plasma physics experiments. Furthermore these nondestructive in situ assessments were novel work, enhancing and developing characterization capability for complex material target assemblies.
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Sav Chima. X-ray computed tomography of adhesive wicking into carbon foam[J]. High Power Laser Science and Engineering, 2017, 5(4): 04000e28
Special Issue: TARGET FABRICATION
Received: Nov. 24, 2016
Accepted: May. 11, 2017
Published Online: Nov. 21, 2018
The Author Email: Sav Chima (sav.chima@awe.co.uk)