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Spatially varying alignment of liquid crystals is essential for research and applications. One widely used method is based on the photopatterning of thin layers of azo-dye molecules, such as Brilliant Yellow (BY), that serve as an aligning substrate for a liquid crystal. In this study, we examine how photopatterning conditions, such as BY layer thickness (b), light intensity (I), irradiation dose, and age affect the alignment quality and the strength of the azimuthal surface anchoring. The azimuthal surface anchoring coefficient, W, is determined by analyzing the splitting of integer disclinations into half-integer disclinations at prepatterned substrates. The strongest anchoring is achieved for b in the range of 5–8 nm. W increases with the dose, and within the same dose, W increases with I. Aging of a non-irradiated BY coating above 15 days reduces W. Our study also demonstrates that sealed photopatterned cells filled with a conventional nematic preserve their alignment quality for up to four weeks, after which time W decreases. This work suggests the optimization pathways for photoalignment of nematic liquid crystals.
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Optical transmission characterization of fused silica materials irradiated at the CERN Large Hadron Collider
The Target Absorbers for Neutrals (TANs) represent one of the most radioactive regions in the Large Hadron Collider. Seven 40cm long fused silica rods with different dopant specifications, manufactured by Heraeus, were irradiated in one of the TANs located around the ATLAS experiment by the Beam RAte of Neutrals (BRAN) detector group. This campaign took place during Run 2 data taking, which occurred between 2016 and 2018. This paper reports a complete characterization of optical transmission per unit length of irradiated fused silica materials as a function of wavelength (240 nm–1500 nm), dose (up to 18 MGy), and level of OH and H2 dopants introduced in the manufacturing process. The dose delivered to the rods was estimated using Monte Carlo simulations performed by the CERN FLUKA team.
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- PAR ID:
- 10472693
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Nucl.Instrum.Meth.A 1055 (2023) 168523
- Date Published:
- Journal Name:
- Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
- Volume:
- 1055
- Issue:
- C
- ISSN:
- 0168-9002
- Page Range / eLocation ID:
- 168523
- Subject(s) / Keyword(s):
- FLUKA, Radiation damage, Fused silica, Optical transmission, numerical calculations: Monte Carlo, CERN LHC Coll, radioactivity
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.nima.2023.168523
