Newsletter | November 2022

Out of the Lab: Terahertz imaging in the field at Stonehenge

TeraView is pleased to announce the publication of a paper on using TeraView’s TeraPulse Lx instrument to study rock carvings on the world famous Stonehenge monument. The paper is a joint collaboration with the University of Brighton, UK, and was produced in collaboration with English Heritage.

Read the full press release here.

A short film discussing the project can be viewed below:

TeraView – Stonehenge Terahertz Project

Select Papers

Polymer pellet fabrication for accurate THz-TDS measurements

Abstract

We investigate fabrication of compacts using polytetrafluoroethylene (PTFE) and polyethylene (PE), and the effect of compaction conditions on their terahertz transmission properties. The conditions used to fabricate compressed powder samples for terahertz time-domain spectroscopy (THz-TDS) can impact the accuracy of the measurements and hence the interpretation of results. This study investigated the effect of compaction conditions on the accuracy of the THz-TDS analysis. Two polymers that are commonly used as matrix materials in terahertz spectroscopy studies were explored using a compaction simulator and a hydraulic press for sample preparation. THz-TDS was used to determine the refractive index and loss coefficient to compare the powder compacts (pellets) to the values of solid material. Sample porosity, axial relaxation and tensile strength were measured to assess the material’s suitability for terahertz spectroscopy. It was found that PTFE is the preferable material for creating THz-TDS samples due to its low porosity and high tensile strength. PE was found to show significant porosity at all compaction pressures, making it an unsuitable material for the accurate determination of optical parameters from THz-TDS spectroscopy measurements. The larger particle sizes of PE resulted in compacts that exhibited significantly lower tensile strength than those made from PTFE making handling and storage difficult.

Full article available here.

Theoretical and experimental analysis of the dielectric properties of 3D orthogonal woven GFRP composites in the terahertz frequency range

Abstract

A novel method to calculate the dielectric constant of (ε’_r) three-dimensional orthogonal woven glass fiber-reinforced polymer-matrix (3DOW-GFRP) composites in the terahertz (THz) frequency range is developed and experimentally verified using the THz time-domain spectroscopy (THz-TDS). The dielectric anisotropy is demonstrated through simulation by considering a single propagation direction of the THz waves and three different fiber orientations in unidirectional GFRP composites. Simulation results are compared to those obtained from the classic rule-of-mixture equations to determine the representative equations for the three different cases of fiber orientations in the (x, y, z) – coordinate system and a new model is developed to calculate ε’_rof 3DOW-GFRP composites based on electromagnetic modeling principles. As opposed to previously reported lumped circuit models, our model addresses the issue of orthogonality of fiber and considers the shape and spatial disposition of the composite with respect to the polarization direction of the THz waves for accurate determination of ε’_r.. A comparison between the measured and calculated ε’_r indicates that the proposed method is highly accurate with ≤ 2.68% maximum error, while the latter reaches 7.82% for the classic rule-of-mixture equations. This method is potentially useful for the design of 3DOW-GFRP with desired ε’_r for applications such as electromagnetic shielding and electrostatic discharging structures.

Full article available here.

Previous Events & Conferences

Europe

TeraView attended IRMMW-THz at Delft in the Netherlands. The event included the presentation of a paper on the study of rock carvings at Stonehenge, along with a demonstration of the TeraPulse Lx modular system.

United States

TeraView were proud to participate as part of the UK Pavilion at the Battery Show in Novi, Michigan, USA. The show proved to be a great success in discussing terahertz solutions for the battery industry.

Upcoming Events & Conferences

TeraView’s VP of Business, Andy Bell, will be presenting a talk on ‘High Accuracy Multi-Layer Paint Thickness measurements’ at this year’s Car Body Painting Workshop in Germany, November 7 at 5.30pm.

Full details can be found here.

ISTFA 2022

TeraView are exhibiting at ISTFA2022 and will be presenting a paper ‘Soft Defect Localization and Characterization for Advanced IC packaging using Novel EOTPR In-situ Dynamic Temperature Probing’.

Full details here.

Would you like to partake in an online workshop?

TeraView are looking at conducting online workshops throughout the year.
Contact us if you are interested