Secondary electron emission from plasma-generated nanostructured tungsten fuzz

Recently, several researchers [e.g., Yanget al., Sci. Rep.5, 10959 (2015)] have shown thattungsten fuzz can grow on a hottungstensurface under bombardment by energetic helium ions in different plasma discharges and applications, including magnetic fusion devices with plasma facingtungsten components. This work reports the directmeasurements of the total effectivesecondary electron emission (SEE) fromtungsten fuzz. Using dedicated materialsurfacediagnostics andin-situ characterization, we find two important results: (1) SEE values fortungsten fuzz are 40% –63% lower than for smoothtungsten and (2) the SEE values fortungsten fuzz are independent of the angle of the incident electron. The reduction in SEE fromtungsten fuzz is most pronounced at high incident angles, which has important implications for manyplasma devices since in a negative-goingsheath the potentialstructure leads to relatively high incident angles for the electrons at the plasma confining walls. Overall, low SEE will create a relatively highersheath potential difference that reduces plasma electron energy loss to the confining wall. Thus, the presence or self-generation in a plasma of a low SEEsurface such astungsten fuzz can be desirable for improved performance of manyplasma devices.

Source: Applied Physics Letters - November 15, 2016 Category: Physics Authors: M. Patino, Y. Raitses and R. Wirz Source Type: research