14 results on '"Youcef, Nedjadi"'
Search Results
2. Ytterbium-175 half-life determination
- Author
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Claude Bailat, Thierry Stora, Youcef Nedjadi, François Bochud, Zeynep Talip, M. Teresa Durán, Ulli Köster, Frédéric Juget, Charlotte Duchemin, and Nicholas P. van der Meulen
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Physics ,Radionuclide ,Spectrum analyzer ,Radiation ,Analogue electronics ,Nuclear engineering ,Detector ,Nuclear data ,010403 inorganic & nuclear chemistry ,01 natural sciences ,0104 chemical sciences ,Metrology ,010309 optics ,Neutron capture ,0103 physical sciences ,Ionization chamber - Abstract
$^{175}$Yb is a radionuclide that can be generated by neutron capture on $^{174}$Yb and whose decay properties make it useful for developing therapeutic radiopharmaceuticals. As it happens with many of the emerging radionuclides for medical uses in recent years, its nuclear data were determined decades ago and are not thoroughly documented nor accurate enough for metrological purposes. The last documented reference for the $^{175}$Yb half-life value is 4.185(1) days and dates back to 1989, so a redetermination of the value was considered appropriate before standardization at the Institute of Radiation Physics (IRA, Lausanne, Switzerland) primary measurements laboratory. Three independent measurement methods were used to this purpose: reference ionization chamber (CIR, $chambre$ $d'ionization$ $de$ $référence$), CeBr$_{3}$ γ-ray detector with digital electronics and a second CeBr$_{3}$ detector with analog electronics and single-channel analyzer (SCA) counting. The value obtained for the $^{175}$Yb half-life is 4.1615(30) days which shows a 0.56% relative deviation to the last nuclear reference value (ENSDF 2004) and is supported with a detailed calculation of the associated uncertainty.
- Published
- 2021
3. Activity standardisation of
- Author
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Youcef, Nedjadi, Laurent, Desorgher, Frédéric, Juget, Thierry, Buchillier, François, Bochud, and Claude, Bailat
- Abstract
We report here on the primary activity standardisation of a
- Published
- 2021
4. Determination of the gamma and X-ray emission intensities of terbium-161
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Frédéric Juget, Zeynep Talip, Thierry Buchillier, M. Teresa Durán, Youcef Nedjadi, Laurent Desorgher, François Bochud, Pascal Grundler, Nicholas P. van der Meulen, and Claude Bailat
- Subjects
Radiation - Abstract
In this study, the gamma and X-ray emission intensities of
- Published
- 2021
5. Activity standardisation of
- Author
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Youcef, Nedjadi, Frédéric, Juget, Laurent, Desorgher, M Teresa, Durán, François, Bochud, Cristina, Müller, Zeynep, Talip, Nicholas P, van der Meulen, and Claude, Bailat
- Published
- 2020
6. Determination of
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M Teresa, Durán, Frédéric, Juget, Youcef, Nedjadi, François, Bochud, Pascal V, Grundler, Nadezda, Gracheva, Cristina, Müller, Zeynep, Talip, Nicholas P, van der Meulen, and Claude, Bailat
- Abstract
The radiolanthanide
- Published
- 2019
7. Evaluation of digital pulse processing techniques for a β-γ coincidence counting system
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M. Teresa Durán, François Bochud, Claude Bailat, Youcef Nedjadi, and Frédéric Juget
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Signal processing ,Radiation ,Computer science ,Detector ,Filter (signal processing) ,010403 inorganic & nuclear chemistry ,01 natural sciences ,Pulse shaping ,030218 nuclear medicine & medical imaging ,0104 chemical sciences ,03 medical and health sciences ,0302 clinical medicine ,Pulse-amplitude modulation ,Electronic engineering ,Coincidence counting ,Electronic hardware ,Digital filter - Abstract
Signal processing is a core part of any electronic chain for radioactivity measurement systems and can influence measurement results drastically. A thorough study of the different alternatives for this treatment is especially worthwhile when developing a new digital system. This article describes an evaluation performed to optimize the digital pulse processing stage of the β-γ coincidence counting system at the Institute of Radiation Physics (IRA) designated laboratory for the activity unit. This study is a part of IRA's digitalization project to modernize the aging analog electronic hardware of its primary measurement systems. The β-γ coincidence counting system consists of a plastic scintillation detector in the beta channel and a well-type NaI detector in the gamma channel. Six pulse shaping digital filters along with amplitude calculation algorithms were implemented to obtain beta and gamma pulse amplitude values. In addition, four timing digital filters and time pick-off methods were set up to calculate arrival times (timestamps) for the pulses generated by both detectors. Filter parameters and algorithm settings were adjusted to obtain the best performance. Combination of filters into traditional two channel (fast for timing and slow for shaping) or one channel configuration using dCFD (digital constant fraction discrimination) and LE (leading edge) time pick-off methods were also tested and compared to study the whole digital pulse processing system, using both real measurement signals (241Am, 137Cs, 60Co and 166mHo) and simulated reference pulses. The results of these tests were quantified by evaluating the following metrics: processing speed, signal-to-noise ratio (SNR) at different energies, gamma energy resolution, time measurement accuracy, time resolution and detection efficiency. The results of this evaluation provide a rational ground to assess the system and help decide which digital pulse processing (DPP) method should be the most appropriate.
- Published
- 2019
8. A portable precision ionization chamber: The transfer ionization reference chamber
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Claude Bailat, François Bochud, Teresa Durán, Christian Kottler, Frédéric Juget, Youcef Nedjadi, and T. Buchillier
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Reproducibility ,Radionuclide ,Radiation ,Chemistry ,Nuclear engineering ,Measure (physics) ,Electrometer ,010403 inorganic & nuclear chemistry ,01 natural sciences ,030218 nuclear medicine & medical imaging ,0104 chemical sciences ,Nuclear physics ,03 medical and health sciences ,0302 clinical medicine ,Ionization ,Ionization chamber ,Calibration - Abstract
A portable instrument was developed at the Institute of Radiation Physics (IRA) for on-site radionuclides measurements. It will enable the measurement of short-lived radionuclides in nuclear medicine departments or isotope production centres. The system involves an ionization chamber read directly by an electrometer and it was optimized to ensure a good reproducibility through the selection of an appropriate vial, filling volume and source position in the well chamber, as well as monitoring the external background and performing a detailed uncertainty estimation. The calibration factors were determined using solutions whose activity concentration is traceable to the international reference system using the IRA reference chamber. Currently the transfer ionization chamber is calibrated for F-18, C-11, O-15, N-13, I-131 and Tc-99m. The final instrument is able to measure isotope activities with a relative standard uncertainty not larger than 1%.
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- 2017
9. On the stability of
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Youcef, Nedjadi, Pierre-François, Duc, François, Bochud, and Claude, Bailat
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The stability of
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- 2016
10. Determination of
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Frédéric, Juget, Youcef, Nedjadi, Thierry, Buchillier, François, Bochud, and Claude, Bailat
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The half-life of
- Published
- 2016
11. A new measurement of the half-life of (166m)Ho
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Yvan Caffari, Claude Bailat, Pascal Froidevaux, Claude Wastiel, François Bochud, Gilles Triscone, Youcef Nedjadi, Niko Kivel, Ines Guenther-Leopold, and Frédéric Jaquenod
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Radioisotopes ,Radiation ,Internationality ,Ion exchange ,Isotope ,Chemistry ,Ion chromatography ,Analytical chemistry ,Half-life ,Equipment Design ,Isotope dilution ,Reference Standards ,Chromatography, Ion Exchange ,Radiation Dosage ,Mass Spectrometry ,Equipment Failure Analysis ,Holmium ,Reference Values ,Mass concentration (chemistry) ,Nuclide ,Radiometry ,Inductively coupled plasma mass spectrometry ,Half-Life - Abstract
The work presented here is a new and precise measurement of the half-life of (166m)Ho by determining the activity concentration, using an ionisation chamber calibrated for this nuclide, and measuring the number of (166m)Ho atoms using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Since the isotope (166)Er interferes with the mass spectrometric measurement, Er has to be eliminated from the (166m)Ho radioactive solution. The elimination was achieved using ion-exchange chromatography with the cation exchange resin Dowex AG 50W-X8 and 2-Hydroxybutanoic acid as the mobile phase. After a first transit through the chromatographic column, the purified (166m)Ho eluate was spiked with natural Er to get a resulting Er isotopic composition close to that of natural Er at better than 99.5%, and then it underwent two further separations to eliminate the Er. The activity concentration of this Er-free radioactive (166m)Ho solution was measured in our reference ionisation chamber calibrated for this nuclide by means of the 4πβ(PC)-γ and 4πβ(PS)-4πγ coincidence techniques and integral counting with a well-type NaI(Tl) detector and Monte Carlo efficiencies. An aliquot of this standardized solution was sent to the Paul Scherrer Institute (PSI) for mass concentration determination using an isotope dilution MC-ICP-MS approach. The mass concentration of (166m)Ho in this solution was determined with 0.25% relative standard uncertainty. This value was corroborated by two other independent measurements. The new half-life of (166m)Ho, 1132.6(39) years (k=1), is compatible with the value determined in 1965, but is 5.6% shorter and about 43 times more precise.
- Published
- 2011
12. Seven years of gamma-ray spectrometry interlaboratory comparisons in Switzerland
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Yvan Caffari, François Bochud, Youcef Nedjadi, Sybille Estier, Philippe Spring, Claude Bailat, and T. Buchillier
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Observer Variation ,Radiation ,Clinical Laboratory Techniques ,Spectrometry, Gamma ,Radiation Monitoring ,Environmental chemistry ,Statistics ,Activity concentration ,Environmental science ,Observer variation ,Food Contamination, Radioactive ,Gamma ray spectrometry ,Switzerland ,Environmental Monitoring - Abstract
Since the 1990s, regular comparisons of gamma-ray spectrometry in Switzerland were organized to improve laboratory abilities to measure the radioactivity in the environment and food stuffs at typical routine levels. The activity concentration of the test samples and the evaluation of the associated uncertainties remained each year the main required test result. Over the years, the comparisons used certified reference solutions as well as environmental samples. The aim of this study is to research the effect of the comparisons on measurement quality. An analysis of the seven last interlaboratory comparisons revealed that the Swiss measurement capability is up to date. In addition, the results showed that the participants now have an improved evaluation of the uncertainties associated with their measurement.
- Published
- 2010
13. Standardisation of 18F by a coincidence method using full solid angle detectors
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François Bochud, Yvan Caffari, Claude Bailat, and Youcef Nedjadi
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Physics ,Fluorine Radioisotopes ,Radiation ,Monte Carlo method ,Detector ,Solid angle ,Scintillator ,Reference Standards ,Standard deviation ,Coincidence ,Computational physics ,Nuclear physics ,Ionization ,Methods ,Scintillation Counting ,Coincidence counting ,Nuclear Medicine - Abstract
A solution of (18)F was standardised with a 4pibeta-4pigamma coincidence counting system in which the beta detector is a one-inch diameter cylindrical UPS89 plastic scintillator, positioned at the bottom of a well-type 5''x5'' NaI(Tl) gamma-ray detector. Almost full detection efficiency-which was varied downwards electronically-was achieved in the beta-channel. Aliquots of this (18)F solution were also measured using 4pigamma NaI(Tl) integral counting and Monte Carlo calculated efficiencies as well as the CIEMAT-NIST method. Secondary measurements of the same solution were also performed with an IG11 ionisation chamber whose equivalent activity is traceable to the Système International de Référence through the contribution IRA-METAS made to it in 2001; IRA's degree of equivalence was found to be close to the key comparison reference value (KCRV). The (18)F activity predicted by this coincidence system agrees closely with the ionisation chamber measurement and is compatible within one standard deviation of the other primary measurements. This work demonstrates that our new coincidence system can standardise short-lived radionuclides used in nuclear medicine.
- Published
- 2010
14. Primary activity measurements with 4pigamma NaI(Tl) counting and Monte Carlo calculated efficiencies
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Gilles Triscone, Marc Décombaz, François Bochud, Youcef Nedjadi, Philippe Spring, Claude Bailat, Jean-Jacques Gostely, and Jean-Pascal Laedermann
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Physics ,Radioisotopes ,Radiation ,Decay scheme ,Monte Carlo method ,Detector ,Liquid scintillation counting ,Solid angle ,Analytical chemistry ,chemistry.chemical_element ,Radon ,Reference Standards ,Ampoule ,Nuclear physics ,chemistry ,Scintillation Counting ,Coincidence counting ,Monte Carlo Method - Abstract
The radioactive concentrations of (18)F, (88)Y and (152)Eu solutions and the activity of (222)Rn gas ampoules are measured using a primary method involving 4pigamma NaI(Tl) integral counting with a well-type NaI(Tl) detector and efficiencies computed by Monte Carlo simulations. The simulations use the GEANT code coupled with a routine (sch2for), which generates randomly the decay paths and emissions depending on the decay scheme parameters. The resulting radioactive concentrations of (88)Y, (152)Eu and (18)F are found to agree with those measured with other primary measurement methods, such as 4pi (beta, e, X)-gamma coincidence counting or liquid scintillation counting. Results of the determination of the activity of (222)Rn gas ampoules by this method also match the results of an absolute standardisation technique in which radon is condensed onto a cold surface and its alpha-emissions are detected through an accurately specified solid angle.
- Published
- 2006
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