FRONTIERS PHOTONICS


3D SCANNING


Imaging technology helps to preserve Ukraine’s heritage


C


itizens in Ukraine are using their smartphones to digitally preserve sites


of cultural importance in case they are damaged or destroyed. As of 12 April 2023, UNESCO


has verified damage to 251 areas since the beginning of the war – including 108 religious sites, 21 museums, 90 buildings of historical and/or artistic interest and 19 monuments. The initiative, called Backup


Ukraine, is creating 3D models of buildings, monuments and artwork from images and videos taken by the general public. It uses 3D reconstruction


technology provided by Polycam, and captures data directly in the Polycam smartphone app, which has been made free in Ukraine. The project transforms standard images and videos into navigable, photorealistic 3D models that can be explored virtually in vivid detail.


The interior and exterior of the Church of Saints Andrew and Jehoshaphat have been recreated virtually via Backup Ukraine


Meanwhile, professionals are scanning larger or more intricate sites. Skeiron, for example, is a group of 3D data experts who have produced hundreds of models of sites of importance, including the destroyed Mariupol Drama Theatre.


BackUp Ukraine has created hundreds of 3D models of artefacts, artworks and buildings for the public to explore virtually


French engineer and 3D data specialist Emmanuel Durand scanned several bombed sites in spring 2022 to bring attention to the destruction of Ukrainian architecture and help future restoration efforts. Using a Leica BLK360 imaging laser scanner, Durand captured several sites, including a children’s library housed in a historic building in Chernihiv. He collected more than a billion data points, which he later processed to depict the scene with transparent layers, providing a unique perspective on the damage: surviving columns and arches stand beside demolished walls bordered by a crater.


“The laser scan brings


a different light, angle and perspective to a particular scene, something that has not existed in that way before,” Durand explained on HxGN Radio’s Digital Realities Podcast. “Just applying transparency to a point cloud allows people to immediately get a greater sense of the damage, like with the crater at the children’s library. This is not available through a photograph alone.” Durand hopes the scans help to sustain attention on Ukraine and attract resources from international institutions and grants for preservation work and rebuilding. l


ENVIRONMENT/ENERGY


PULSED LASERS


Photonics tech pushes past nuclear fusion milestone


I


n a defining moment for photonics, one of the most promising applications


of laser technology - the realisation of laser-driven fusion – has achieved a historical breakthrough. Announced by Lawrence


Livermore National Laboratory (LLNL) on 13 December, scientists at the National Ignition Facility (NIF) were able to release a fusion energy of 3.15 megajoules (MJ) from a pellet filled with the hydrogen isotopes deuterium and tritium. This is equivalent to 154%of the expended energy equivalent to 2.05MJ of the laser pulse that triggered the explosion. This net energy gain


represents the first breakthrough in fusion research. In the new milestone at NIF,


giant pulsed lasers deliver energy of more than two million Joules of UV light precisely into a ~1cm long gold-coated cylinder, which experts call a ‘Hohlraum’, where the interaction of the laser beams with the inner walls produces X-rays. These then spread evenly in the hohlraum as in a hot oven. A bead about two millimetres in size, containing a mixture of the hydrogen isotopes deuterium and tritium and suspended in the centre of the hohlraum, absorbs the propagating X-rays heating up rapidly. The outer shell of the pellet


is blown off, and the resulting implosion pressure compresses the hydrogen fuel reaching to a density hundreds of times of solid matter, forming a hot spot at its centre with a temperature


Each NIF laser bay is 122m long and contains 96 beamlines. This side view of Laser Bay 2 shows the four-high laser transport beamline enclosures above the preamplifier support structure


or more than 120 million degrees celsius. In turn this triggers the fusion of hydrogen into helium. In the current experiment, 2.05MJ of laser energy was used to compress and heat the target. Only ~ one per cent of the energy is delivered to the hot spot due to inefficiencies in the implosion process. The thermal runaway driven by the fusion reaction ignited the plasma and produced ~ 3.15MJ of energy


with an instantaneous power of about 52,500,000,000,000,000 watts, the diameter of which is less thick than a hair. The key advance over previous results was made possible by data from previous experiments and a better understanding of fusion physics, which then led to improvements in the hohlraum design, the structure of the fuel pellet, and modifications to the laser and the laser pulse. l


8 Photonics Frontiers 2023


BackUp Ukraine


LLNL NIF and Photon Science


BackUp Ukraine


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