The use of ultrafine and nanocrystalline materials is a proposed pathway to mitigate irradiation damage in nuclear fusion components. Here, we examine the radiation tolerance of helium bubble formation in 85 nm (average grain size) nanocrystalline-equiaxed-grained tungsten and an ultrafine tungsten-TiC alloy under extreme low energy helium implantation at 1223 K via in-situ transmission electron microscope (TEM). Helium bubble damage evolution in terms of number density, size, and total volume contribution to grain matrices has been determined as a function of He + implantation fluence. The outputs were compared to previously published results on severe plastically deformed (SPD) tungsten implanted under the same conditions. Large helium bubbles were formed on the grain boundaries and helium bubble damage evolution profiles are shown to differ among the different materials with less overall damage in the nanocrystalline tungsten. Compared to previous works, the results in this work indicate that the nanocrystalline tungsten should possess a fuzz formation threshold more than one order of magnitude higher than coarse-grained tungsten.

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The middle glenohumeral ligament (MGHL) is well recognized as a primary stabilizer of the shoulder. Its role in shoulder pathologies such as adhesive capsulitis, subscapularis tendon tear, and glenohumeral arthritis is less understood. Biomechanically, the MGHL plays an important role in range of motion, specifically involving normal and pathologic external rotation in less than 45 of abduction. In this Technical Note, we present a technique for arthroscopic release of the MGHL in the setting of a stable shoulder with preoperative loss of external rotation and a patient at risk for postoperative restriction of external rotation.