Wagga Wagga CMM 2016

Development of a compact X-ray source

Not scheduled

15m

Speaker

Ms Emily Wern Jien Yap (UNSW Australia/CSIRO Mineral Resources)

Description

Since their discovery by Wilhelm Röntgen in 1895, X-rays have become a valuable tool for characterising the composition and structure of matter. The X-ray tube has long been central to techniques such as X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis. However, the external high-voltage power supply, size and costs associated with X-ray tube technology have limited the wider application of X-ray analysis. There has recently been a renewed interest in using materials exhibiting coupling mechanisms such as pyro- and piezoelectricity to generate X-rays [1, 2]. The surfaces of these materials inherit an intrinsic charge due to a spontaneous polarisation, induced by either temperature change or mechanical stress. This can be exploited to generate a high voltage in a low pressure gas, capable of both ionising the gas and accelerating the liberated electrons into a target to produce X-rays. This allows more portable X-ray sources to be built, with power supply voltages dramatically reduced from over 10 kV to a few volts [3-5]. The compact X-ray generator is being developed based around the pyroelectric effect. A vacuum chamber testbed has been constructed for the characterisation and optimisation of these novel X-ray generators. Mass flow controllers are used in conjunction with a turbo-molecular and diaphragm pump to control the gas pressure in the chamber. An Arduino microcontroller is employed to operate a thermoelectric cooler, which cycles the temperature of the pyroelectric crystal under-test. The microcontroller is also used to record temperature and pressure readings. A silicon drift detector is installed to characterise the X-ray output. Along with the details on the experimental apparatus, initial measurements using LiNbO3 crystals will be presented. References: [1] J. D. Brownridge and S. Raboy, "Investigations of pyroelectric generation of x-rays," Journal of Applied Physics, vol. 86, p. 640, 1999. [2] B. Gall, S. D. Kovaleski, J. A. Van Gordon, P. Norgard, A. Benwell, B. H. Kim, et al., "Investigation of the Piezoelectric Effect as a Means to Generate X-Rays," Ieee Transactions on Plasma Science, vol. 41, pp. 106-111, Jan 2013. [3] G. L. Clark, Applied X-rays, Fourth ed. London: McGraw-Hill Publishing Company Ltd., 1955. [4] E. F. Kaelble, Ed., Handbook of X-rays: For diffraction, emission, absorption and microscopy. New York, U.S.A.: McGraw-Hill, Inc., 1967, p.^pp. Pages. [5] J. A. Geuther and Y. Danon, "Electron and positive ion acceleration with pyroelectric crystals," Journal of Applied Physics, vol. 97, p. 074109, 2005.