Laser powder bed fusion of a pure tungsten ultra-fine single pinhole collimator for use in gamma ray detector characterisation. (November 2019)

• Record Type: Journal Article
• Authors: Sidambe, A.T.; Judson, D.S.; Colosimo, S.J.; Fox, P.
• Is Part Of: International journal of refractory metals & hard materials. Volume 84(2019)
• Publication Date: 2019-11
• Subjects: Laser powder bed fusion -- Selective laser melting -- Tungsten -- Refractory metals -- Additive manufacturing -- Collimator -- Gamma radiation; Heat resistant alloys -- Periodicals; Refractory materials -- Periodicals; Metallography -- Periodicals; Alliages réfractaires -- Périodiques; Matériaux réfractaires -- Périodiques; Métallographie -- Périodiques; Heat resistant alloys; Metallography; Refractory materials; Periodicals; Electronic journals; 669.73
• DOI: 10.1016/j.ijrmhm.2019.104998
• Languages: English
• ISSNs: 0263-4368

Abstract

Abstract: Laser Powder Bed Fusion is a leading additive manufacturing technology, whose use has been recently extended to refractory metals such as tungsten. This work was carried out to manufacture a pure tungsten pinhole collimator that would otherwise be difficult to produce using conventional methods such as machining. The laser powder bed fusion process was used to produce an ultra-fine 0.5 mm diameter hole running along a 40 mm long beam stop component. A laser powder bed fusion scanning strategy (laser energy density of 348 J/mm 3 ) was selected with the aim of fabricating a high density tungsten component. The manufactured collimator was then used for gamma-ray detector characterisation. A collimated gamma-ray using a 241 Am source mounted on an automated scanning table was used to study the gamma-ray interaction with respect to position in a semiconductor detector, so that the position-dependent charge collection process could be characterized. The 0.5 mm diameter fine tungsten collimator yielded a relatively narrower beam spot, leading to more accurate scan results. However that was at the expense of number of gamma rays detected per second. Overall, the 0.5 mm collimator allowed for higher resolution scans giving better detector characterisation results in comparison to a 1 mm diameter collimator. Highlights: LPBF was used to produce a tungsten collimator that would be difficult to produce using conventional methods Collimated gamma-ray sources were used to study the gamma-ray interaction wrt position in a semiconductor detector Position-dependent charge collection was characterized and the fine LPBF tungsten collimator yielded a narrower beam spot The more accurate scan results came at the expense of gamma rays per second It is envisaged that the 0.5 mm LPBF collimator would be used to scan specific regions of interest on a detector.