Abstract
The Synchrotron-light for Experimental Science and Applications in the Middle East (SESAME) is currently in the process of designing, constructing and procuring a hard X-ray full-field tomography beamline through international collaboration. The beamline will use phase contrast and absorption imaging. The beamline will be designed with a front end, optical hutch and an experimental hutch. With the construction of the BEAmline for Tomography at SESAME (BEATS) beamline underway, there is a need to design and analyse the equipment for the sample environment. Namely the detector stage and the sample furnace.
The aim of this study is to design and study the experimental hutch equipment required to study samples in the beamline for the SESAME light source. The project will focus on the equipment in the experimental hutch and will be centred around the detector stage where the detector stage design will be optimised for minimum displacement taking into account the floor vibration of SESAME and the study of a sample heating furnace for computed tomography. To achieve the aim of the project, the following objectives were identified: Characterise vibration of a back scattering monochromator and benchmark it against experimental data, analyse the vibrational displacement of the SESAME detector stage using the Finite Element Method and design a lab scale furnace and characterise its’ thermal behaviour for the purposes of design optimization.
In order to conduct the vibrational analysis of the BEATS detector stage, an existing structure from the European Synchrotron Radiation Facility (ESRF) beamline ID28 was used in order to validate the modelling technique. The structure in question is the back scattering monochromator from the optical hutch. Amplitude response data was gathered from the back scattering monochromator. A Finite Element Analysis model of the monochromator was developed and the vibrational response data from the model was validated against measured vibrational data.
The comparison of the experimental data and the model data showed that there was a deviation of 4% on the modal analysis and 2% deviation of the Root Mean Squared (RMS) displacement values in the three Cartesian directions, thus, validating the accuracy of the model. Hence justifying the model’s application to studying the vibrational response of the BEATS detector stage.
The BEATS detector stage was modelled using the same technique as the Insertion Device 28 (ID28) back scattering monochromator to calculate the modal frequencies and the RMS displacement values. It was found that the RMS displacement values were below the limit of (1μm) and this certified that the structure is sufficiently rigid.
The second aspect of the study was the design of a small-scale furnace for the purpose of heating samples. The maximum design temperature of the furnace is 1500℃. The sample holder was designed with a graphite crucible for induction heating for samples that are non-metallic. In order to characterise the heat distribution and the flow of nitrogen gas, used to maintain an inert environment for the samples, a Computational Fluid Dynamics model was developed to study the different parameters such as heat distribution in the base with different materials for the purpose of design optimization.
In conclusion, part of the equipment design for the BEATS experimental hutch has been analysed and studied using engineering best practices, experiment, and numerical simulation. It is further concluded that the detector stage structure is sufficiently rigid and will not deflect under vibrational noise to a point where the image quality will be compromised during experiments. It is recommended that the furnace is tested and benchmarked against the model and if necessary, the model should be fine-tuned. It can also be concluded that the gas in the furnace will encapsulate the sample such that it does not oxidise during the heating process and that the base of the furnace will be at a temperature which will not cause drift on the sample stage due to high temperatures.