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Digital x-ray processing electronics for fluorescence EXAFS and spectroscopy : The 9th National conference on synchrotron radiation instrumentation (1996)

Hubbard, B. ; Warburton, W.K. ; Zhou, C.Z.

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 67 (1996), S. 3371-3371

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: We have developed a digital x-ray processor (DXP) for x-ray fluorescence spectroscopy, implemented in a 4-channel CAMAC module, which accepts inputs of either polarity from reset or tail preamplifiers, and outputs one spectrum per channel. Digital trapezoidal shaping and efficient pileup rejection are implemented in dedicated logic, with programmable peaking times from 0.5 to 20 msec. The energy resolution is comparable to good analog units at equivalent peaking times. A maximum input count rate (ICR) of 500,000 cps per channel can be accomodated at a peaking time of 0.5 msec. A digital signal processor on each channel is used to collect the data, apply corrections, and update the spectrum. The capabilities of the DXP prototype at high rates was tested at SSRL. Using an Ortec single-element germanium detector, the resolution was seen to degrade somewhat with increasing ICR above 150,000 cps, due to effects that we are still investigating. Collaborating with Hewlett-Packard and SSRL, the DXP was also used with a Kevex Si(Li) detector for trace element detection on silicon wafers in comparison with Kevex readout electronics. At 4 msec peaking time, DXP's resolution was slightly worse (10–15 eV) due to some excess noise pickup, though the background levels in the spectra were essentially identical in the two systems and the DXP's maximum count rate was several times higher. © 1996 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1147335

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Possible extensions of XIA's digital spectrometer technology to portable and remote monitoring instrumentation (1998)

Warburton, W. K. ; Darknell, D. A. ; Hubbard, B.

Springer

Journal of radioanalytical and nuclear chemistry 233 (1998), S. 233-239

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ISSN: 1588-2780

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract The XIA DXP-4C, a 4 channel, CAMAC based X-ray spectrometer, is based on digitally processing directly digitized preamplifier signals. Designed for instrumenting multi-detector arrays for synchrotron radiation applications, the DXP-4C was optimized for very high count rates at a low cost per detector channel. These design constraints coincidentally lead to an instrument which is very compact and relatively low power (3.4 W/channel), considering its count rate and MCA capabilities, and which therefore offers interesting possibilities for effective extension to portable applications. Further, because all functions (gain, filter parameters, pileup inspection criteria and internal calibrations) are digitally controlled, the design can be readily adapted to a large variety of user interfaces, including remote access interfaces. Here we present the basics of the design and examine approaches to lowering the power to less than 300 mW/channel while retaining count rate capabilities in excess of 50,000 cps. We then consider the engineering issues associated with portable and remote spectrometry applications, examining in detail the three cases of a lead paint detector, a remote contamination monitor, and a space mission spectrometer.