Doctorate in Applied and Engineering Physics  

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Thesis Proposal for the

Doctorate Program in Applied and Engineering Physics (DAEPHYS)

Starting in the Academic Year 2016/2017


Proposal 031


Title:Development of a state-of-the-art energy dispersive x-ray fluorescence spectrometer for biomedical applications
 
Objectives (recommended length: 2000-3000 char):
Energy Dispersive X-ray fluorescence (EDXRF) techniques, have been used for many years in the quantification of trace elements in several kind of samples, ranging from biological to geological [1]. These systems employ solid state detectors which allow obtaining energy dispersive spectra with energy resolutions up to 125 eV for the Kα line of Mn [2].

However, the lower limits of detection of commercial systems, which typically use a planar geometry, are of the order of tens of ppm, which for studies of toxic elements in the human organism is not viable. The toxicity of cancerous elements such as Be, Cr, Co, Ni, As, Cd, Sb, Pb, Hg, Pt, Mn, Fe, Cu, Zn, Se and Sr [3], sits at the level of the ppm down to hundreds of ppb, demanding better lower limits of detection, at least by a factor of 10.

The double polarization of the X-ray tube radiation, which is composed not only by the characteristic X-rays from the anode but also from Bremstrahlung, can seriously suppress the spectra noise, improving the detection limits. Thus, the use of this kind of spectrometers in human toxicology studies is possible.

The main goal of this work is that of designing and building a state-of-the-art energy dispersive X-ray spectrometer, using a triaxial geometry through the use of a secondary target. This way, the incoming radiation, which is the prime source for the background in the final spectra, can be completely suppressed, only remaining the secondary radiation from the secondary target. We intend to automatize all of the system for the interchange of secondary targets, filters and samples allowing a decrease of the operator exposure to ionizing radiation.

The X-ray tube driving the system is a Philips PW1400, capable of delivering 100kV and 80mA, with a Rh anode, and the detector is an Amptek XR-100SDD with a detection area of 25mm2 and 500 µm thickness with a Be window of 25 µm.

The step motors and the spectra acquisition program will be controlled remotely through an application developed by the candidate in LabView or Python.

[1] P. J. Custódio, M. L. Carvalho, F. Nunes, S. Pedroso and A. Campos, “Direct analysis of human blood (mothers and newborns) by energy dispersive X-ray fluorescence”, J. Trace Elem. Med. Biol.,19 (2-3), 151-8 (2005)
[2] M. Guerra, M. Manso, S. Longelin, S. Pessanha and M. L. Carvalho, “Performance of three different Si X-ray detectors for portable XRF spectrometers in cultural heritage applications”, Journal of Instrumentation, 7, C10004 (2012)
[3] W.H. Organization. International Agency for Research on Cancer. 2012; Available from: http://www.iarc.fr/.

 
Framework (recommended length: 500-2000 char):
The Atomic Physics Group of LIBPhys-UNL has several decades of expertise in X-ray spectrometry in the fields of highly charged ion plasmas, toxicology, material analysis, cultural heritage and forensic science. The required equipment, such as the X-ray tube and detector already exists in the Department of Physics of the Universidade Nova de Lisboa (UNL).
 
Tasks (recommended length: 1000-3000 char):
1. Bibliographic study of EDXRF systems
2. Design of the spectrometer geometry and sample support
3. Construction of the spectrometer
4. Testing and characterization of the X-ray beam (shape, flux, etc..)
5. Test of the spectral quality for all combinations of secondary targets and filters
6. Quantification assessment of a high matrix range of reference materials
7. Study of biological samples such as cancerous tissues and heavy metal contaminated human tissues
8. Dissertation writing
 
Research centre/lab or R&D unit hosting the thesis project:
LIBPhys-UNL
 
University to which the thesis project will be presented:
UNL - Universidade Nova de Lisboa
 
DAEPHYS Scientific Domain in which the project fits:
Instrumentation
 
Relation of the project to the Scientific Domains of DAEPHYS:
The project aims at developing instrumentation for the automation of an existing spectrometer at FCT UNL. The project will involve the design of the linear stages and the step motors control units and a software for control and signal acquisition of the experiment.
 
Candidate profile:
It is expected that the candidate is proficient in electronics and computer programming.
 
Does this proposal involve more than one University?:
no
 
Synergies between the two Universities participating in the proposal:
DAEPHYS strongly encourages the presentation of thesis projects in co-supervision by researchers from two of the universities participating in the Program. In this field, explain the benefits resulting from the proposed co-supervision and the involvement of elements from the two universities, e.g. building critical mass teams, profiting from existing infrastructures or advanced equipments, profiting from expert technical know-how, etc. If the proposal involves only one University, write n/a.
(recommended length: 500-1000 char)
: n/a
 
Does this proposal involve a company?:
no
 
Proposals involving a company:
DAEPHYS strongly encourages the presentation of thesis projects involving a company, preferably a high-tech company. These proposals have to: 1) be centered on a technological problem in which the partner company has been (or plan / would like to be) involved; 2) have a co-supervisor on the enterprise; 3) include part of the project to be carried out in the company.
(recommended length: 500-1000 char)
:

 

Supervisor

Name:Mauro Guerra
Institution:Universidade Nova de Lisboa
email:mguerra@fct.unl.pt
 
link to CV or indication of ORCID ID:
0000-0001-6286-4048

 

Co-Supervisor

Name:José Paulo Moreira dos Santos
Institution:Universidade Nova de Lisboa
email:jps@fct.unl.pt
 
link to CV or indication of ORCID ID:
0000-0002-5890-0971

 

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