From Event: SPIE Optical Engineering + Applications, 2016
There are several challenges associated with the design and manufacture of the optics required for the imaging time-of-
propagation detector constructed for the Belle II particle physics experiment. This detector uses Cherenkov light
radiated in quartz bars to identify subatomic particles: pions, kaons, and protons. The optics are physically large
(125 cm x 45 cm x 2 cm bars and 45 cm x 10 cm x 5 cm prisms), all surfaces are optically polished, and there is very
little allowance for chamfers or surface defects. In addition to the optical challenges, there are several logistical and
handling challenges associated with measuring, assembling, cleaning, packaging, and shipping these delicate
This paper describes a collaborative effort between Pacific Northwest National Laboratory, the University of
Cincinnati, and ZYGO Corporation for the design and manufacture of 48 fused silica optics (30 bars and 18 prisms)
for the iTOP Detector. Details of the iTOP detector design that drove the challenging optical requirements are
provided, along with material selection considerations. Since the optics are so large, precise, and delicate, special
care had to be given to the selection of a manufacturing process capable of achieving the challenging optical and
surface defect requirements on such large and high-aspect-ratio (66:1) components. A brief update on the current
status and performance of these optics is also provided.
Mike Albrecht, James Fast, and Alan Schwartz, "Design and manufacture of imaging time-of-propagation optics," Proc. SPIE 9969, Radiation Detectors: Systems and Applications XVII, 99690C (Presented at SPIE Optical Engineering + Applications: September 01, 2016; Published: 12 September 2016); https://doi.org/10.1117/12.2238833.
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