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This work presents a study of radioactivity in soil samples collected from oil well sites of the Al-Qayyarah Oil Wells and refinery in Nineveh Government, Iraq. The study utilized spectroscopy system with NaI(Tl). The average activity concentrations observed were 30.58±0.38 Bq/kg for 226Ra, 19.98±0.57 Bq/kg for 232Th, 292.32 ±10.28 Bq/kg for 40K. These results were compared to the average worldwide values, and it was found that the values for some sites exceeded the allowable worldwide levels. Additionally, various hazard indices were calculated. The radium equivalent activity (Raeq) was 81.97 Bq/kg, the absorbed gamma dose rate (DR) was 38.55 nGy/h, the annual effective dose rate (AEDE) was 47.28 µSv/y outdoor and 189.13 µSv/y indoor, the external hazard (Hex) was 0.22, the internal hazard (Hin) was 0.30, the gamma radiation representative level index (I?) was 0.60, the annual gonadal dose equivalent (AGDE) was 271.05, and the excess lifetime cancer risk was 165.48. Statistical analyses, including mean, median, standard deviation, kurtosis, skewness, box plots, frequency distributions, Quantile-quantile (Q-Q) plots, Pearson's correlation coefficient, principal component analysis (PCA), and cluster analysis, were conducted to further examine and explain the results.

QC 2024-03-15

The activity concentrations of 226Ra, 232Th and 40K were determined in 43 soil samples collected from 0 to 10 cm and 10 to 50 cm depths of Niška Banja region, Serbia, using a low background gamma spectroscopy with 3″ × 3″ NaI(Tl) scintillation detector. The mean absorbed dose rate of 0–10 cm and 10–50 cm depth soil were 66.1 and 60.4 nGy/h, respectively which was close to UNSCEAR worldwide value. The radium equivalent and annual effective dose effect were lower than the permissible level. Therefore, there is no significant radiological risk from the soil to residents living in this region.

Sorption and desorption of Al(III) on a series of different extraction resins (LN, LN2, LN3, TK100, TK101, TK201) in acidic HNO3 media containing high concentrations of V(IV,V) was investigated. Static batch studies were conducted as a way of obtaining preliminary distribution coefficient (Kd) values that were further used to develop dynamic tests on real samples. It was shown that a complete separation and recovery of Al(III) from V(V) under acidic conditions (pH = 2) is possible by utilizing LN resin. Active “hot” dynamic studies with 26Al (≈10 Bq) as a radiotracer and real waste samples were conducted to further investigate and confirm the results of the inactive “cold” experiments. Utilizing this separation procedure, we have successfully removed all traces of 26Al (∼10−9 g) radiotracer from the bulk vanadium matrix.

The use of segmented HPGe detectors for gamma-ray tracking applications is well established. The spectroscopic capabilities of these detectors make them most suitable for such applications. For similar reasons, the use of such detectors in the tomographic measurement of irradiated nuclear fuel has also been envisioned. Especially, these detectors can facilitate faster fuel examination with excellent energy resolution. We have proposed and designed a novel planar segmented HPGe detector for use in gamma emission tomography. The design of the detector segmentation and the mode of operation is unique and offers six simultaneous detection channels for tomographic measurements. This work reports the first experimental evaluation of the performance of the detector. Important characteristics of the detector have been obtained, such as energy resolution of the segments in 1-fold (one segment) and 2-fold (two segments) modes, throughput curves, crosstalk energy corrections, and mislocalisation rate. Collimated source tests have been performed and the results have been compared with the MCNP simulations results. The obtained results are as expected and in good agreement with the simulation results, and it is estimated that using this detector can speed up the data collection by 3.2 times in comparison to an unsegmented detector of the same overall dimensions, in a tomographic application. Further improvements are foreseeable if scaling up to a larger detector with greater segmentation.

Gamma emission tomography (GET) is a proven non-invasive technique for post-irradiation examination of nuclear fuel. In the past, collimated HPGe detectors were used for GET measurements due to their good energy resolution. However, because a large number of projections need to be acquired to achieve high spatial resolution, the use of a single HPGe detector is associated with long measurement times. This thesis investigates the use of an electrically segmented HPGe detector for GET, proposing two conceptual types of segments: 1) scattering segments, each aligned with a collimator slit for localisation, and 2) energy deposition segments for aiding in the full energy deposition. The feasibility of a true coaxial segmented detector for this application was studied using the Monte Carlo particle transport code MCNP. Performance parameters, such as detection efficiency and mislocalisation rate, were obtained using proposed analysis methods. Furthermore, the dimensions of the segmentation pattern of the 18 detection elements were optimised based on the detector's foreseeable use and the performance parameters. For the experimental demonstration, a scaled-down planar prototype detector consisting of 6 scattering segments and 1 energy deposition segment was designed, with a working principle similar to the proposed true coaxial detector. The spatial response of the collimated prototype detector was obtained using MCNP simulations. In the experimental evaluation, energy resolution in different operating modes, count rate capabilities, and mislocalisation rate were obtained. The detector was found 3 times faster than when used in an unsegmented mode upon comparing the simulation and experimental results concerning the relative detection efficiency. An experimental demonstration of the detector in the proposed application was successfully performed at the BETTAN tomography test bench at Uppsala University using three mockup fuel rods (filled with 137Cs source). Images were re

This dataset is a report about gamma spectroscopy measurement of the irradiated cyclotron target generated by GammaVision software (ORTEC/AMETEK, Version 8.00.03).

The present thesis is focused on gamma spectroscopy studies using germanium semiconductor detectors. In particular, two different lines of research were addressed. On one hand, gamma emissions coming from low energy proton interactions on the two stable isotopes of chlorine, 35Cl and 37Cl, via elastic scattering and (p,alfa) and (p,n) channels were investigated with the purpose of measuring, for the first time, detailed gamma yields and differential cross sections. The other branch of research was the study of environmental gamma radiation. Natural sources of radiation have been investigated by measuring and analysing the background at three locations. The EnsarRoot program was the cornerstone of these investigations, because it provided a general framework where data analysis and simulations were conducted.

The activity concentrations of 226Ra, 232Th and 40K were determined in 43 soil samples collected from 0 to 10 cm and 10 to 50 cm depths of Niška Banja region, Serbia, using a low background gamma spectroscopy with 3″ × 3″ NaI(Tl) scintillation detector. The mean absorbed dose rate of 0–10 cm and 10–50 cm depth soil were 66.1 and 60.4 nGy/h, respectively which was close to UNSCEAR worldwide value. The radium equivalent and annual effective dose effect were lower than the permissible level. Therefore, there is no significant radiological risk from the soil to residents living in this region. © 2023, Akadémiai Kiadó, Budapest, Hungary.

All matter in our Universe is made up of atoms, which are made up of protons, neutrons and electrons. The protons and neutrons sit tightly bound together by the strong force in the nucleus, which the electrons orbit. Understanding the structure of nuclei is a vital part of fundamentally understanding what we are all made of. Nuclei where the number of protons is equal to the number of neutrons are generally the most stable. Studying highly unstable nuclei with disproportionate numbers of protons and neutrons is interesting because it provides a deeper understanding of how the strong force works. Nuclei have discrete energy levels - and so when they lose energy they emit gamma rays with fixed energies, and other types of radiation, such as protons, alpha radiation and neutrons. The Germanium isotope of interest in this thesis was created by using a fusion-evaporation reaction in the Argonne National Laboratory, USA. The Argonne Tandem Linac Accelerator System was used to accelerate a beam of Calcium-40 atoms to collide with a stationary Magnesium-24 target. This thesis is an attempt at exploring the nuclear structure of Germanium-62, while confirming and extending its level scheme.

The activity of 226Ra, 232Th and 40K in soil samples were measured by gamma spectrometry using high-purity germanium detector. The study involved 40 samples from four divisions: 10 samples each were drawn from the control area (CTR), washing area 1 (W1), washing area 2 (W2) and the mining pits (MP). Radium and Thorium were measured in highest value (80.44 and 94.62) Bq/kg, respectively at MP-9 while the lowest levels (1.56 and 0.96) Bq/kg, respectively were detected at MP-2. At W1, 40K (max. 887.5 Bq/kg) recorded the highest mean level while 232Th (mean=16.7 Bq/kg) had the lowest level. For W2, 40K (max. 1535.7 Bq/kg) recorded highest level and 232Th (mean = 8.1 Bq/kg) recorded the lowest (10.7 Bq/kg). Results further show that mean activity levels of 226Ra, 232Th and 40K fromining area 42.5, 35.5 and 652.4Bq/kg, respectively. In comparison, the respective average activity for 40K, 226Ra, and 232Th recoded 118.4, 14.5 and 9.7 Bq/kg, respectively in control area. For the sake of assessing the suitability of building materials, hazard indices were calculated and their results were less than unity indicating that, building materials are safe. The annual gonadal equivalent dose, representative gamma index, alpha index revealed values of 484.8 µSv/y, 1.1 and 0.2, respectively. The average annual effective dose was 85.5 mSv which is about 8% greater than the world average. Results show that mining activities in Rwamagasa might be posing radiological hazard to people. Therefore, measures on radioactive materials to the miners and the surrounding community are recommended.

DAL MOLIN, ANDREA, open, Fast particles, both electrons and ions, play an important role for the success of the next generation of large tokamak devices, such as ITER, that will prove the feasibility of magnetically confined thermonuclear fusion as an energy source. Ions accelerated by external heating or born in fusion reactions can reach energies in the MeV range. Their primary role is to sustain the plasma temperature and the fusion reaction rate, thus lots of efforts have been put into the development of efficient heating schemes and in the improvement of their confinement. On the other hand, during fast terminations of plasma pulses on tokamaks, electrons can accelerate to relativistic velocities, entering the runaway regime. Runaway electrons have enough energy to seriously damage the plasma facing components of large tokamaks, thus mitigation techniques are under study in view of ITER operations. This thesis focuses on the implementation of deconvolution techniques for the reconstruction of the fast particles distributions from their emission in the MeV energy range. The problem was approached from two different perspectives: the unfolding of the runaway electrons velocity-space distribution from spectroscopic measurements of their bremsstrahlung emission, and the tomographic reconstruction of the density distribution of both fast ions and runaway electrons from the integrated measurement of their emission performed with multiple lines of sight. These algorithms were implemented in an open source Python library. Four deconvolution algorithms were implemented for the unfolding of runaway electrons energy distribution: singular value decomposition, maximum likelihood - expectation maximization, Tikhonov regularization and Poissonian regularization. The transfer matrix necessary for this inversion was calculated using the GENESIS code for estimating the probability of bremsstrahlung emission and the MCNP code for computing the detector response function. The detector response function w, Lo studio degli ioni ed elettroni veloci è fondamentale per il successo della prossima generazione di tokamak di grande dimensione, come ITER, che mirano a dimostrare la possibilità di produrre energia attraverso la fusione termonucleare. Siano essi accelerati dal riscaldamento ausiliario o nati da reazioni di fusione, gli ioni possono raggiungere energie nell’ordine dei MeV. Questa energia viene poi trasmessa al plasma attraverso collisioni, aumentandone l’energia media e il rateo delle reazioni di fusione. È quindi cruciale migliorare il confinamento degli ioni veloci e sviluppare schemi di riscaldamento efficienti. Gli elettroni, invece, possono raggiungere velocità relativistiche se accelerati da campi elettrici induttivi generati durante disruzioni di plasma. Questi elettroni runaway rappresentano una minaccia per l'integrità strutturale dei tokamak di grandi dimensioni e necessitano di essere mitigati. Questa tesi tratta di metodi di deconvoluzione applicati alla ricostruzione della distribuzione delle particelle veloci a partire dall’emissione di radiazione nel range di energia del MeV. La deconvoluzione è stata declinata in due modi: unfolding della distribuzione di velocità degli elettroni runaway a partire dalla loro radiazione di bremsstrahlung, e tomografia della distribuzione di densità di ioni veloci o elettroni runaway a partire dalla misura dei loro profili di emissione fatta con linee di vista multiple. Questi algoritmi sono stati implementati in una libreria Python open source. Quattro algoritmi per l’unfolding sono stati implementati: singular value decomposition, maximum likelihood - expectation maximization, regolarizzazione di Tikhonov and di Poisson. La matrice di probabilità necessaria per svolgere queste inversioni è stata calcolata usando il codice GENESIS per stimare la probabilità di emettere fotoni di bremsstrahlung, e il codice MCNP per calcolare la funzione di risposta del detector. Queste funzioni di risposta sono state calcolate per, 0, open, Panontin, E

Independent yield distributions of high-energy neutron-induced fission are of importance to achieve a good understanding of fission. Even though the mass and charge yield distributions of thermal neutron-induced fission are well known, there are few experimental data for high-energy neutron-induced fission. In addition to basic research on the fission process, independent yield distributions of high-energy neutron-induced fission play a key role in the development of Generation IV fast nuclear reactors. To facilitate measurements of independent fission yields of high-energy neutron-induced fission, a dedicated ion guide and a proton-neutron converter were developed and put to use in experiments at the isotope separator facility IGISOL in Jyväskylä. In parallel, a simulation model of the system was developed in order to optimize the collecting efficiency of fission products in the ion guide. The model uses the Monte Carlo code MCNPX to simulate the neutron production, the fission model code GEF to simulate the fission process, and GEANT4 for ion transportation. In order to benchmark the simulation model, metal foils were inserted in the ion guide with the purpose of collecting fission products. At the same time, nickel, cobalt and indium foils were located between the pn-converter and the ion guide to record the neutron flux from the pn-converter. After the beam was turned off, and after several days of cooling, g-ray spectroscopy measurements of the foils were conducted using a well shielded HPGe detector. Based on the identified g-ray transitions in the spectroscopy data, the productions of corresponding fission products and neutron activation products were calculated, and then used to benchmark the transportation and collection of fission products, as well as neutron production, in the simulations. The conclusion from the benchmark is that the transportation of fission products in the helium gas, as simulated by GEANT4, agrees very well with the measurement, while

Gamma-ray spectrometry using collimated detectors is a well-established examination method for irradiated nuclear fuel. However, the feasibility of examining a particular nuclide of interest is subject to constraints; the peak must be statistically determinable with the desired precision and the total spectrum count rate in the detector should not cause throughput issues. Methods were assembled for gamma spectrum prediction to optimize instruments for gamma emission tomography and to enable a priori feasibility evaluation of determination of single peaks of irradiated nuclear fuel. The aim was to find reliable results (~10% accuracy) regarding total spectrum and peak count rates with faster computation time than a full-Monte Carlo approach. For this purpose, the method is based on depletion calculations with SERPENT2, a point-source kernel method for the collimator response, a rig response matrix and a detector response matrix, both computed with MCNP6. The computational methodology uses as input the fuel properties (dimensions, materials, power history, and cooling time), and the instrumental setup (collimator and detector dimensions and materials). The prediction method was validated using measured data from a high-burnup, short-cooled test fuel rodlet from the Halden reactor. Absolute count rates and ratios of characteristic peaks were compared between predicted and measured spectra, showing a total count rate overestimation of 7% and discrepancies between 2-20% for the single peaks (same order of magnitude of the uncertainty). This level of agreement is deemed sufficient for measurement campaigns planning, and the optimization of spectroscopic instruments for use in gamma scanning and tomography of nuclear fuel.

Swedish Nuclear Fuel and Waste Management Company- SKB has conducted measurement campaigns at the Swedish central interim storage facility for spent nuclear fuel- CLAB over the years, extending from year 2003 to 2019 where the gamma energy escape was acquired. At CLAB the spent nuclear fuel assembly is inserted into the calorimeter; device intended to measure temperature increase due to decay heat from the fuel assembly. The calorimetric construction is surrounded by water the medium in which the temperature deviations occur and thus are also measured by the calorimeter. However, there is some leakage of gamma energy from the calorimetric construction and does not contribute to the heating of the water. Therefore, only considering the calorimetric measurements is not enough to estimate the total decay heat in the fuel assembly since these measurements fail to account for the gamma escape. Measurements of gamma energy escape acquired over the years at CLAB were observed to have some tendencies that where questionable, mainly some stochastic behavior indicating that their uncertainty was profound. In the scope of the thesis a computational method was developed to calculate the gamma energy escape and thus assist in determining which measurements to discard. Combination of two programs were used one being Spent Nuclear fuel- SNF and the second Monte Carlo N particle Simulator- MCNP, to obtain the computational gamma energy escape for different fuel assemblies and cooling times- CTs. It was established that the escape had a range between 1-3,5% and that it had a dependency on CT, fuel assembly type and operational history. Calculated radial exponential decay coefficient for fuel assemblies of the medium; water had also a clear dependency on CT where values of the coefficient increased over CT. Normalized gamma energy distribution over a rotation around the fuel assembly was calculated and it showed that the assembly tended to have the highest radiation coming from its c

Lo studio degli ioni ed elettroni veloci è fondamentale per il successo della prossima generazione di tokamak di grande dimensione, come ITER, che mirano a dimostrare la possibilità di produrre energia attraverso la fusione termonucleare. Siano essi accelerati dal riscaldamento ausiliario o nati da reazioni di fusione, gli ioni possono raggiungere energie nell’ordine dei MeV. Questa energia viene poi trasmessa al plasma attraverso collisioni, aumentandone l’energia media e il rateo delle reazioni di fusione. È quindi cruciale migliorare il confinamento degli ioni veloci e sviluppare schemi di riscaldamento efficienti. Gli elettroni, invece, possono raggiungere velocità relativistiche se accelerati da campi elettrici induttivi generati durante disruzioni di plasma. Questi elettroni runaway rappresentano una minaccia per l'integrità strutturale dei tokamak di grandi dimensioni e necessitano di essere mitigati. Questa tesi tratta di metodi di deconvoluzione applicati alla ricostruzione della distribuzione delle particelle veloci a partire dall’emissione di radiazione nel range di energia del MeV. La deconvoluzione è stata declinata in due modi: unfolding della distribuzione di velocità degli elettroni runaway a partire dalla loro radiazione di bremsstrahlung, e tomografia della distribuzione di densità di ioni veloci o elettroni runaway a partire dalla misura dei loro profili di emissione fatta con linee di vista multiple. Questi algoritmi sono stati implementati in una libreria Python open source. Quattro algoritmi per l’unfolding sono stati implementati: singular value decomposition, maximum likelihood - expectation maximization, regolarizzazione di Tikhonov and di Poisson. La matrice di probabilità necessaria per svolgere queste inversioni è stata calcolata usando il codice GENESIS per stimare la probabilità di emettere fotoni di bremsstrahlung, e il codice MCNP per calcolare la funzione di risposta del detector. Queste funzioni di risposta sono state cal, Fast particles, both electrons and ions, play an important role for the success of the next generation of large tokamak devices, such as ITER, that will prove the feasibility of magnetically confined thermonuclear fusion as an energy source. Ions accelerated by external heating or born in fusion reactions can reach energies in the MeV range. Their primary role is to sustain the plasma temperature and the fusion reaction rate, thus lots of efforts have been put into the development of efficient heating schemes and in the improvement of their confinement. On the other hand, during fast terminations of plasma pulses on tokamaks, electrons can accelerate to relativistic velocities, entering the runaway regime. Runaway electrons have enough energy to seriously damage the plasma facing components of large tokamaks, thus mitigation techniques are under study in view of ITER operations. This thesis focuses on the implementation of deconvolution techniques for the reconstruction of the fast particles distributions from their emission in the MeV energy range. The problem was approached from two different perspectives: the unfolding of the runaway electrons velocity-space distribution from spectroscopic measurements of their bremsstrahlung emission, and the tomographic reconstruction of the density distribution of both fast ions and runaway electrons from the integrated measurement of their emission performed with multiple lines of sight. These algorithms were implemented in an open source Python library. Four deconvolution algorithms were implemented for the unfolding of runaway electrons energy distribution: singular value decomposition, maximum likelihood - expectation maximization, Tikhonov regularization and Poissonian regularization. The transfer matrix necessary for this inversion was calculated using the GENESIS code for estimating the probability of bremsstrahlung emission and the MCNP code for computing the detector response function. The detector response function w

An accurate characterization of the neutron fields at spallation sources is crucial for many applications based on neutron irradiations, such as radiation damage tests that need a precise dose estimate. In this work, we present the neutron flux measurements performed with the multi-foil activation technique in the ROTAX and ChipIr beamlines of the ISIS spallation source, characterized by moderated and unmoderated spectra, respectively. We selected many different activation reactions to cover a wide energy range, from thermal to very fast neutrons up to about 100 MeV. By applying a Bayesian unfolding algorithm, we demonstrate the effectiveness of this technique in measuring the neutron flux intensity and energy spectrum with precision and accuracy.

Glavni cilj ove doktorske disertacije je sinteza poroznog aluminosilikatnog materijala za potencijalnu primenu u oblasti zaštite životne sredine. Aluminosilikatni materijali ekološki su prihvatljivi u smislu energetske efiksanosti i male potrošnje energije za sintezu. Sinteza ovakvih materijala podrazumeva i smanjenje proizvodnje gasova sa efektom staklene bašte, odnosno CO2. U prvom delu doktorske disertacije ispitivane su termodinamičke karakteristike homogenih rastvora alkalnih aktivatora na osnovu kojih se mogu tumačiti molekulske interakcije unutar rastvora. Ispraćena je promena termodinamičkih parametara (gustine, viskoznosti, indeksa refrakcije i brzine zvuka) u zavisnosti od temperature. Porozni silikatni materijali sintetisani su od polazne komponente (metakaolin-MK), alkalnog aktivatora koji se sastoji od rastvora NaOH različitih koncentracija (2M-16M NaOH) i natrijum silikata. Potencijalna primena usmerena je na ispitivanje adsorpcionih karakteristika ovih materijala za adsorpciju teških metala i ispitane su mehaničke osobine materijala radi potencijalne primene u građevinarstvu. Umrežena je i organska faza (poli(vinil-alkohol)-(PVA)) radi poboljšanja karakteristika sintetisanog materijala. Različitim metodama (rendgenska difrakciona analiza (XRD), Furijeova transformacija infracrvena spektroskopija (FTIR), Raman spektorskopija, Skenirajuća elektronska mikroskopija, (SEM)) analizirane su promene strukture sintetisanog materijala kao i morfologije čestica prahova prekursora i mikrostruktura sintetisanih uzoraka. Rendgenskom flurescentnom analizom (XRF) određen je hemijski sastav polaznih sirovina i sintetisanog materijala. XRD analizom i Raman spektroskopijom izvršena je identifikacija faza i praćenje veličina kristalita i udela amorfne faze u sintetisanom poroznom silikatnom materijalu. SEM metodom je ispitana morfologija čestica prahova prekursora, veličina i oblik pora sintetisanih poroznih materijala, a metodom energetske disperzione spektroskopije (ED, The main goal of this doctoral dissertation is the synthesis of porous aluminosilicate materials for potential application in the field of environmental protection. Aluminosilicate materials are environmentally friendly in terms of energy efficiency and low energy consumption for synthesis. The synthesis of such materials implies a reduction in the production of greenhouse gases, i.e., CO2. In the first part of the doctoral dissertation, the thermodynamic characteristics of homogeneous solutions of alkaline activators were examined, on the basis of which molecular interactions within the solution can be interpreted. The change of thermodynamic parameters (density, viscosity, refractive index and speed of sound) depending on temperature was monitored. Porous silicate materials were synthesized from the starting component (metakaolin-MK), an alkaline activator consisting of a solution of NaOH of different concentrations (2M-16M NaOH) and sodium silicate. The potential application is aimed at testing the adsorption properties of these materials for adsorption of heavy metals and the mechanical properties of the materials for potential application in construction have been examined. The organic phase (Poly(vinyl alcohol) (PVA)) was also crosslinked to improve the characteristics of the synthesized material. Changes in the structure of the synthesized material as well as the morphology of the precursor powder particles and the microstructure of the synthesized samples were analyzed by various methods (X - ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, Scanning electron microscopy (SEM)). The chemical composition of the starting materials and the synthesized material was performed by X - ray fluorescence analysis (XRF). XRD and Raman spectroscopy identified the phases and monitored the crystallite size and the proportion of the amorphous phase in the synthesized porous silicate material. SEM examined the morphology of p

The neutron generation technique was tested on the microtron M-10 with an output electron beam of 8.7 MeV. Given the low energy that the microtron can provide to electrons, the bremsstrahlung induced photonuclear reaction 9Be (, n), which has a low threshold, was chosen for neutron generation. Cobalt and indium targets were tested as activation detectors to estimate the neutron flux density. In the cobalt target, the isomeric state of 60mCo with an energy of 58.6 keV and a half-life of 10.5 minutes is well activated. Two well-known additional gamma lines of standard cobalt source permit to clarify the absolute value of the neutron flux. The activated indium target has four gamma lines bound to the 116mIn isomer - decaying with the half-life of 54.4 minutes, what is convenient for measurement of gamma spectrum. Despite the low energy of the output electron beam, at a beam intensity of 5 A it is possible to obtain an almost isotropic neutron flux of 107 n/(scm2).

Segmented coaxial HPGe (High Purity Germanium) detectors have recently been shown to be feasible for Gamma Emission Tomography (GET). This type of detector allows for a combination of high efficiency and high energy resolution in gamma spectrometry of irradiated nuclear fuel. The ultimate aim of developing segmented HPGe for GET measurements is to achieve a high spatial resolution to facilitate imaging of rod-internal features and interrogation of smaller irradiated fuel samples. In this work, we present the optimisation of a segmented HPGe detector through a simulation study using the Monte Carlo particle transport code MCNP. Constraints to each dimension of the detector were identified, from manufacturing limitations and requirements arising from the use of a finite-sized collimator slit. In particular, a relationship between the minimum inner radius of the coaxial detector and the segments azimuthal dimension was derived based on the identified constraints. Segment azimuthal and radial dimensions have been varied (based on the derived relationship between the azimuthal and radial dimension) and the full energy efficiency and misidentification rate were evaluated to obtain the optimal dimensions. The optimal ranges of the segment dimensions were determined., VR Bränslediagnostik

Future colliders will set stringent requirements on the performance of detector materials in terms of timing and radiation hardness. Scintillating garnet crystals proved to satisfy the latter, while the former can be improved through technological developments. In this work, optical and scintillation properties of Cerium-doped Gd3Al2Ga3O12 (GAGG:Ce) single crystals were studied upon gamma radiation excitation. Several 2x2x3 mm3 and 2x2x10 mm3 samples from various producers were characterized in terms of light output, transmission, scintillation kinetics and coincidence time resolution (CTR). Light output was measured using a 137Cs radioactive source, ranging between 27900 and 49500 photons per MeV. Scintillation emission time profiles were measured with 511 keV gamma excitation, and the fastest samples displayed components below 70 ps rise time and 50 ns decay time. CTR was measured employing silicon photomultipliers (SiPMs) obtaining a best value of 87 ± 2 ps full width at half maximum, significantly improving on past state-of-the-art GAGG.

The neutron generation technique was tested on the microtron M-10 with an output electron beam of 8.7 MeV. Given the low energy that the microtron can provide to electrons, the bremsstrahlung induced photonuclear reaction 9Be (, n), which has a low threshold, was chosen for neutron generation. Cobalt and indium targets were tested as activation detectors to estimate the neutron flux density. In the cobalt target, the isomeric state of 60mCo with an energy of 58.6 keV and a half-life of 10.5 minutes is well activated. Two well-known additional gamma lines of standard cobalt source permit to clarify the absolute value of the neutron flux. The activated indium target has four gamma lines bound to the 116mIn isomer - decaying with the half-life of 54.4 minutes, what is convenient for measurement of gamma spectrum. Despite the low energy of the output electron beam, at a beam intensity of 5 A it is possible to obtain an almost isotropic neutron flux of 107 n/(scm2).

The neutron generation technique was tested on the microtron M-10 with an output electron beam of 8.7 MeV. Given the low energy that the microtron can provide to electrons, the bremsstrahlung induced photonuclear reaction 9Be (, n), which has a low threshold, was chosen for neutron generation. Cobalt and indium targets were tested as activation detectors to estimate the neutron flux density. In the cobalt target, the isomeric state of 60mCo with an energy of 58.6 keV and a half-life of 10.5 minutes is well activated. Two well-known additional gamma lines of standard cobalt source permit to clarify the absolute value of the neutron flux. The activated indium target has four gamma lines bound to the 116mIn isomer - decaying with the half-life of 54.4 minutes, what is convenient for measurement of gamma spectrum. Despite the low energy of the output electron beam, at a beam intensity of 5 A it is possible to obtain an almost isotropic neutron flux of 107 n/(scm2).

The neutron generation technique was tested on the microtron M-10 with an output electron beam of 8.7 MeV. Given the low energy that the microtron can provide to electrons, the bremsstrahlung induced photonuclear reaction 9Be (, n), which has a low threshold, was chosen for neutron generation. Cobalt and indium targets were tested as activation detectors to estimate the neutron flux density. In the cobalt target, the isomeric state of 60mCo with an energy of 58.6 keV and a half-life of 10.5 minutes is well activated. Two well-known additional gamma lines of standard cobalt source permit to clarify the absolute value of the neutron flux. The activated indium target has four gamma lines bound to the 116mIn isomer - decaying with the half-life of 54.4 minutes, what is convenient for measurement of gamma spectrum. Despite the low energy of the output electron beam, at a beam intensity of 5 A it is possible to obtain an almost isotropic neutron flux of 107 n/(scm2).

Daten zur Bestrahlung und Gammaspektroskopiemessung des Targets

Although primarily deemed to be an ornamental stone, granite may also be ground into fines for use in cement mortars, where it exhibits high strength and durability. Both the 40K present in the stone and the natural decay series of its uranium, thorium and actinium components exhibit high activity concentrations. An understanding is therefore needed of the correlation among the different particle sizes in granite aggregate to assess their con tribution to a mortar’s activity concentration index (ACI). This study analyses the variation in ACI with particle size in three types of granite based on the chemical, mineralogical and radiological characterisation of five size fractions. The activity concentrations of the tho rium and uranium natural decay series were highest in the finest fractions. A correlation was observed between thorium and the MgO and Fe2O3 normally present in mica group phyllosilicates. In two of the three granites, the mortars prepared with the smallest size particles had ACI values >1.

Threshold activation detectors (TAD) are of great importance for a determination of neutron energy spectra and flux density. For different sources, it is necessary to choose the right combination of materials that cover the estimated spectra. Several different materials were irradiated in a quasi-monoenergetic neutron field with 29.1 MeV peak neutrons energy in the CANAM facility. Neutrons were produced in p + Li-7 reaction in a thin target and the foils were situated in the proton beam axis and close geometry to the Li target. The integral number of protons was established from accelerator telemetry and lithium target activation measurements after the experiment. During the experiment, one long irradiation was done for following foils: Al, Au, Bi, Co, Cu, Fe, In, Mn, Pb, Ta, V, Y and four short irradiations for foils: Cu, Fe, In, Ta, V, W, Y. The foils were irradiated in a sandwich configuration, sorted by cross-section where the materials with higher cross-section were placed in the back of the sandwich. Neutrons produced in the p + Li-7 reaction have a quasi mono-energetic spectrum which provides a suitable basis for cross-section determination. Experimental results were calculated for (n,xn), (n,p) and (n,) reactions via the dosimetry foils activation method including a gamma-ray spectroscopy method. Several important spectroscopic corrections have to be applied to increase the accuracy of the obtained results, including neutron background suppression. Experimental data will be submitted to the EXFOR database.

This paper presents the results of neutron flux measurements at two irradiation facilities of the TRIGA Mark II reactor at ENEA Casaccia Research Center, Italy. The goal of these measurements is to provide a complete characterization of neutron irradiation facilities for accurate and precise dose evaluation in radiation damage tests and, more generally, for all applications that need a good knowledge of neutron flux in terms of intensity, energy spectrum and spatial distribution. The neutron activation technique is used to measure the activation rates of several reactions, chosen so to cover the whole energy range of neutron flux spectrum. A multi-group neutron flux measurement is obtained through an unfolding algorithm based on a Bayesian statistical model. The obtained results prove that this experimental method allows to measure the total neutron flux within 2% statistical uncertainty, and to get at the same time a good description of its energy spectrum and spatial distribution.

Threshold activation detectors (TAD) are of great importance for a determination of neutron energy spectra and flux density. For different sources, it is necessary to choose the right combination of materials that cover the estimated spectra. Several different materials were irradiated in a quasi-monoenergetic neutron field with 29.1 MeV peak neutrons energy in the CANAM facility. Neutrons were produced in p + Li-7 reaction in a thin target and the foils were situated in the proton beam axis and close geometry to the Li target. The integral number of protons was established from accelerator telemetry and lithium target activation measurements after the experiment. During the experiment, one long irradiation was done for following foils: Al, Au, Bi, Co, Cu, Fe, In, Mn, Pb, Ta, V, Y and four short irradiations for foils: Cu, Fe, In, Ta, V, W, Y. The foils were irradiated in a sandwich configuration, sorted by cross-section where the materials with higher cross-section were placed in the back of the sandwich. Neutrons produced in the p + Li-7 reaction have a quasi mono-energetic spectrum which provides a suitable basis for cross-section determination. Experimental results were calculated for (n,xn), (n,p) and (n,) reactions via the dosimetry foils activation method including a gamma-ray spectroscopy method. Several important spectroscopic corrections have to be applied to increase the accuracy of the obtained results, including neutron background suppression. Experimental data will be submitted to the EXFOR database.

Im Rahmen der vorliegenden Arbeit wurde der Einfluss der Pilzarten Leucoagaricus naucinus und Schizophyllum commune auf den Transfer von Radionukliden in Pflanzen auf radioaktiv kontaminierten Böden untersucht. Ziel der Untersuchungen war es, geeignete Kandidaten für ein Strahlenschutzkonzept zu identifizieren, welches auf die Fixierung der potentiell gesundheitsschädigenden Radionuklide im Boden durch ein dort zu etablierendes Pilz-Myzel abzielt (Myko-Fixierung). Hierzu wurden Pflanzenaufzucht-Experimente von Kartoffeln (Solanum tuberosum) und Winterroggen (Secale cereale) unter Laborbedingungen, sowie Feldexperimente auf einem Testfeld 5 km südlich des ehemaligen Kernreaktors von Tschernobyl durchgeführt, bei denen der Boden gezielt durch die Pilzkulturen beimpft wurde. Im Rahmen der, ausführlich in der Arbeit diskutierten, Unsicherheiten, konnten hierbei Hinweise auf einen reduzierenden Effekt von Leucoagaricus naucinus auf die Aufnahme von Cs-137 in Pflanzen, auf bis zu 55 % verglichen mit der Kontrollgruppe, identifiziert werden. Der Pilz Schizophyllum commune zeigte eher einen mobilisierenden Effekt des Cs-137, und erhöhte die Aufnahme in Pflanzen auf bis zu 128 % weshalb dieser für ein Strahlenschutzkonzept zur Myko-Fixierung als ungeeignet befunden wurde. Im Rahmen der Bodenanalytik auf dem Testfeld nahe Tschernobyl wurden umfangreiche Daten zur lokalen Aktivitätsverteilung und zur chemischen Speziation der Nuklidbelastung gewonnen. Diese deuten im Fall des Sr-90 darauf hin, dass noch bis zu 13 % des ursprünglich deponierten Inventars refraktär im Boden gebunden vorliegt und damit noch nicht in die Bodenlösung freigesetzt wurde. Im Rahmen einer umfangreichen Durchsuchung der zur Transferfaktorbestimmung genommenen Bodenproben, konnten 12 Reaktorpartikel aus dem Boden des Testfeldes isoliert und mittels Rasterelektronenmikroskopie und Gammaspektrometrie charakterisiert werden. Hierbei zeigte sich, dass der überwiegende Anteil (6 von 12) der gefundenen Partike, The impact of the fungal species Leucoagaricus naucinus and Schizophyllum commune on the soil-to-plant radionuclide transfer was investigated. The study aims at the potential of soil-dwelling fungal mycelia for the retention and fixation of radionuclides in soils (myco-fixation) and the minimization of radionuclide uptake by crops cultivated on contaminated lands. For this purpose, we grew potatoe (Solanum tuberosum) and winter rye (Secale cereale) plants on soils incoluated with fungal biomass. Parallel to labwork which was carried out in growth chambers at the institute of radioecology and radiation protection, Hannover, we also examined the effect of fungal treatment on a testfield in the Chernobyl exclusion zone, located 5 km south of the former nuclear power plant. Within the boundaries of the given uncertainties - which are adressed in detail in the manuscript - we were able to show a reduction of Cs-137 transfer to the leaves of winter rye by Leucoagaricus naucinus down to 55 \% as compared to the control group. Treatment with Schizophyllum commune induced a slight increase in radionuclide uptake in the majority of experiments, resulting in a transfer of up to 128 % of Cs-137 in potatoe tubers as compared to the control group. Extensive analytical work was conducted aiming at the status of radionuclide contamination of the testfield. Here, we found roughly 13 % of the Sr-90 inventory to be associated with the refractory fraction of soil. We performed a systematical screening of soil samples collected for the determination of transfer factors to identify and isolate a total of 12 reactor particles from the soil matrix. These were characterized using electron microscopy and single particle gamma spectroscopy. Most frequently we identified the reactor particles as non-oxidized UO2-particles (6 out of 12). We also identified a number of particles that we interpreted as secondary phases of reactor-borne fuel. Using energy dispersive X-ray analysis we found that on

Threshold activation detectors (TAD) are of great importance for a determination of neutron energy spectra and flux density. For different sources, it is necessary to choose the right combination of materials that cover the estimated spectra. Several different materials were irradiated in a quasi-monoenergetic neutron field with 29.1 MeV peak neutrons energy in the CANAM facility. Neutrons were produced in p + Li-7 reaction in a thin target and the foils were situated in the proton beam axis and close geometry to the Li target. The integral number of protons was established from accelerator telemetry and lithium target activation measurements after the experiment. During the experiment, one long irradiation was done for following foils: Al, Au, Bi, Co, Cu, Fe, In, Mn, Pb, Ta, V, Y and four short irradiations for foils: Cu, Fe, In, Ta, V, W, Y. The foils were irradiated in a sandwich configuration, sorted by cross-section where the materials with higher cross-section were placed in the back of the sandwich. Neutrons produced in the p + Li-7 reaction have a quasi mono-energetic spectrum which provides a suitable basis for cross-section determination. Experimental results were calculated for (n,xn), (n,p) and (n,) reactions via the dosimetry foils activation method including a gamma-ray spectroscopy method. Several important spectroscopic corrections have to be applied to increase the accuracy of the obtained results, including neutron background suppression. Experimental data will be submitted to the EXFOR database.

Threshold activation detectors (TAD) are of great importance for a determination of neutron energy spectra and flux density. For different sources, it is necessary to choose the right combination of materials that cover the estimated spectra. Several different materials were irradiated in a quasi-monoenergetic neutron field with 29.1 MeV peak neutrons energy in the CANAM facility. Neutrons were produced in p + Li-7 reaction in a thin target and the foils were situated in the proton beam axis and close geometry to the Li target. The integral number of protons was established from accelerator telemetry and lithium target activation measurements after the experiment. During the experiment, one long irradiation was done for following foils: Al, Au, Bi, Co, Cu, Fe, In, Mn, Pb, Ta, V, Y and four short irradiations for foils: Cu, Fe, In, Ta, V, W, Y. The foils were irradiated in a sandwich configuration, sorted by cross-section where the materials with higher cross-section were placed in the back of the sandwich. Neutrons produced in the p + Li-7 reaction have a quasi mono-energetic spectrum which provides a suitable basis for cross-section determination. Experimental results were calculated for (n,xn), (n,p) and (n,) reactions via the dosimetry foils activation method including a gamma-ray spectroscopy method. Several important spectroscopic corrections have to be applied to increase the accuracy of the obtained results, including neutron background suppression. Experimental data will be submitted to the EXFOR database.

In-vivo range verification has been a hot topic in particle therapy for more than a decade. In spite of vast efforts made by research groups all over the world, clinical means for routinely monitoring the range of therapeutic proton or carbon ion beams in the patient’s body and to ensure their correspondence with the treatment plan are not yet available. The paper reviews recent approaches with focus on prompt-gamma based methods, and points to challenges that have not yet been fully recognized or discussed: First, the macro time structure of treatment beams in common proton therapy facilities requires detection systems with extreme load tolerance, throughput capability, and stability against load variations. Second, the test time available for verifying the range of a single pencil beam spot is of the order of milliseconds, which limits the number of prompt gamma events that can be detected and processed. Tight event selection by passive or active collimation as applied in all imaging setups sharpens the information carried by a valid event but strongly reduces their total number. It might be better to use a multitude of uncollimated detectors acquiring time and energy signatures of every gamma hit with reasonable precision, and to pick up all the pieces of information comprised in timing, energy, and coincidence patterns irrespective of their sharpness. This would maximize the number of valid events on the expense of information sharpness, and could eventually increase the total yield of information exploitable for range verification. Some aspects of such a strategy have already been realized with the Prompt Gamma-Ray Timing (PGT) and the Prompt Gamma Peak Integration (PGPI) techniques proposed recently. Data analysis schemes for a more generalized approach have not yet been developed, but the hardware to be used can already be sketched: Prompt gamma rays should be detected with scintillation detector blocks consisting of single pixels with individual light readou

The Lundium decay station improves on the existing TASISpec spectrometer used to investigate the nuclear structure of superheavy nuclei by photon- and charged particle-spectroscopy. This thesis aims to explore the potential benefits of the future Lundium station with the augmentation of anti-Compton shields com- posed by a set of BGO scintillator bars. The effects of anti-Compton shields was in- vestigated through a simulation toolkit, Geant4, developed by CERN. The Lundium station augmented by the anti-Compton shields was constructed in the simulation framework, then simulations of two point-like isotropic sources, 661.7 keV and Eu- 152, located at the Lundium focal plane were done. A beam-spot like Cs-137 was also simulated. The data was sorted and analyzed considering the effects of Compton scattering and the geometry of the setup. The response of Lundium and Lundium with anti-Compton shields augmentation was compared using the 661.7 keV gamma source. The effects of a more realistic situation were examined with the Cs-137 distribution, and the detector response of high energy gamma rays were explored using Eu-152. The anti-Compton shield augmentation yielded peak-to-background percentage increase of roughly 9% with comparable results in the more realistic simulation with Cs-137 distribution. The use of anti-Compton shields with multiple energies of photons was also successful in increasing the relative peak intensities., Simulation to See Superheavy Elements All matter as we understand are made up of combinations of different elements. The more common elements in the universe such as hydrogen and carbon are widely known and may feel familiar, but what about the rarest of the elements that are almost never seen? Elements are made up of 3 subatomic particles: neutrons, protons, and electrons. The stability of the isotopes, same element but with different numbers of neutrons, depends on the numbers and the ratios of these particles. Stability of an isotope mainly refers to its half-life, the average time it takes for half of an element’s sample to decay. The common and accessible elements (up to 103 protons), which are quite stable, have been studied thoroughly in their properties and potential applications. On the contrary, elements with more than 103 protons, commonly referred as superheavy elements, are more radioactive and thus unstable which generally make them rarer and difficult to deal with. When the anatomy of an atom was understood and elements were found, there has been constant scientific effort to discover new elements. Recently, new superheavy elements (element 115 and 117) have been synthesized and confirmed by the scientific community. These elements were found in studies of the “Island of Stability,” a region hypothesized to exist in the superheavy region of the chart of nuclides where there is a temporary increase in stability due to effects of magic numbers in the nuclear shell model which describes the structure of atoms’ nuclei. While the stability tends to decrease with higher numbers of protons and neutrons, this island of stability represents abnormality in a trending group of increasingly unstable nuclei. However, the formation of these new superheavy elements have been rare and difficult, which makes studying their properties even more challenging. In addition, due to the expenses and the energy required to create these elements, the experiments often involve

The activity concentrations of the naturally occurring radionuclides 238U, 232Th and 40K in soil samples taken from the towns of Okahandja and Karibib in Namibia have been determined by gamma-ray spectroscopy using an HPGe detector. The average activity concentrations of 238U, 232Th and 40K in Karibib are 29.4±5.8Bq/kg, 49.0±8.6Bq/kg, and 824.3±153.5Bq/kg while they are 40.9±8.6Bq/kg, 57.9±19.4Bq/kg, and 562.4±125.4Bq/kg respectively in Okahandja. Most of these values are much higher than the corresponding worldwide average values. These activity concentrations were used to calculate different radiological parameters in order to evaluate the associated health hazard. The value of 9.5×10−2 mSv/y obtained for the mean effective dose rate in both towns is far below the permissible limit of 1.0mSv/y recommended by the ICRP and implies that there is no significant radiation hazard in the towns. Also, the values of 163.0Bq/kg and 167.1Bq/kg obtained for the average radium equivalent activity (Raeq) in the towns and the corresponding values obtained for the average external hazard index (Hex) are much below their maximum permissible limits thus confirming that radiological hazard is negligible in the towns.

The gamma-strength functions and level densities of in the quasi-continuum of 147,149Sm isotopes have been extracted from particle-gamma coincidences using the Oslo method. The nuclei of interest were populated via (p,d) reactions on pure 148,150Sm targets and the reaction products were recorded by the HYPERION array. An upbend in the gSF has been observed. The systematic analysis of the gSF for a range of Sm isotopes show that the scissors mode and the upbend compete with each other. Shell model calculations show a very good agreement with the experimental gSFs and confirm the competition between the upbend and scissors mode.

This paper investigates how concentrations of certain fission products and their related gamma-ray emissions can be used to discriminate between uranium oxide (UOX) and mixed oxide (MOX) type fuel. Discrimination of irradiated MOX fuel from irradiated UOX fuel is important in nuclear facilities and for transport of nuclear fuel, for purposes of both criticality safety and nuclear safeguards. Although facility operators keep records on the identity and properties of each fuel, tools for nuclear safeguards inspectors that enable independent verification of the fuel are critical in the recovery of continuity of knowledge, should it be lost. A discrimination methodology for classification of UOX and MOX fuel, based on passive gamma-ray spectroscopy data and multivariate analysis methods, is presented. Nuclear fuels and their gamma-ray emissions were simulated in the Monte Carlo code Serpent, and the resulting data was used as input to train seven different multivariate classification techniques. The trained classifiers were subsequently implemented and evaluated with respect to their capabilities to correctly predict the classes of unknown fuel items. The best results concerning successful discrimination of UOX and MOX-fuel were acquired when using non-linear classification techniques, such as the k nearest neighbors method and the Gaussian kernel support vector machine. For fuel with cooling times up to 20 years, when it is considered that gamma-rays from the isotope 134Cs can still be efficiently measured, success rates of 100% were obtained. A sensitivity analysis indicated that these methods were also robust.

In this article we present a method of characterizing scintillating materials by digitization of each individual scintillation pulse followed by digital signal processing. With this technique it is possible to measure the pulse shape and the energy of an absorbed gamma photon on an event-by-event basis. In contrast to time-correlated single photon counting technique, the digital approach provides a faster measurement, an active noise suppression, and enables characterization of scintillation pulses simultaneously in two domains: time and energy. We applied this method to study the pulse shape change of a CsI(Tl) scintillator with energy of gamma excitation. We confirmed previously published results and revealed new details of the phenomenon., Accepted Author Manuscript, RST/Luminescence Materials

CeBr3 scintillation detectors with light readout by photomultiplier tubes (PMT) have been used for prompt-gamma measurements in proton radiotherapy aiming at treatment verification by Prompt Gamma Timing (PGT) or Prompt Gamma Spectroscopy (PGS). Such treatments are usually structured in distinct beam spots grouped in several mono-energy layers, separated by breaks of few-seconds duration for beam energy switching. This causes a multitude of extreme load steps during delivery of a single treatment field. The paper presents preliminary results of two experiments exploring effects of such load steps on gain and timing of PGT detection units as developed for use in clinical treatments. Multiple units, consisting of scintillation detector (2”×1…2” CeBr3 crystal coupled to Hamamatsu R13089 or R13089-100 photomultiplier) and a plugged-on high-throughput digital spectrometer (U100 by Target Systemelektronik) that also provides well stabilized dynode voltages for the PMT, were exposed to prompt gamma radiation produced by 225 MeV protons in a plexiglass (PMMA) layer, or to bremsstrahlung produced by 13 MeV electrons. Beam shots of 3-5 s duration and varied intensity provoked load steps from background up to the Mcps region and back, and allowed analyzing the immediate and the retarded response of PMT gain and timing. Indeed we observed a noticeable change of the PMT transit time with the detector load, indicating that space charge effects are involved. The scaling of gain turns with the mean anode current supports this hypothesis. As long as the mean anode current is in a ‘reasonable’ operating range, gain and timing drifts of given detectors are well correlated, at least in the stationary case. The observed load-induced timing shifts are as large as 100 ps and would seriously disturb PGT measurements in a treatment, but could eventually be corrected for by tracking the PMT gain. In treatments, this could be done by tracking the ubiquitous 511 keV annihilation peak.

In-situ range verification of ion beams during dose delivery is a key for further improving the precision and reducing side effects of radiotherapy with particle beams. The detection and analysis of prompt gamma rays with respect to their emission points, emission time, and emission energy can provide corresponding means. Prompt gamma-ray imaging (PGI) has already been used for range verification in patient treatments with proton beams. The prompt gamma-ray timing (PGT) technique promises range verification at lower hardware expense with simpler detection systems superseding heavy collimators. After proving the principle, this technique is now being translated to the treatment room. The paper presents latest experimental results obtained with clinically applicable PGT hardware in irradiations of plexiglass targets in pencil beam scanning (PBS) mode with proton beams at clinical dose rates. The data were acquired with multiple PGT detection units while the distal layer of an artificial 1 Gy dose cube treatment plan was repeatedly delivered to a solid PMMA target that sometimes comprised a cylindrical air cavity of 5, 10, or 20 mm depth. The corresponding local range shifts were clearly detected and visualized by analyzing position or variance of the prompt gamma-ray timing peaks in PGT spectra assigned to the individual PBS spots. In this context, a major challenge concerning all prompt-gamma based techniques is examined and discussed: collecting the event statistics that is needed for range verification of single pencil beam spots at an accuracy level of a few millimeters.

In-vivo range verification has been a hot topic in particle therapy for more than a decade. In spite of vast efforts made by research groups all over the world, clinical means for routinely monitoring the range of therapeutic proton or carbon ion beams in the patient’s body and to ensure their correspondence with the treatment plan are not yet available. The paper reviews recent approaches with focus on prompt-gamma based methods, and points to challenges that have not yet been fully recognized or discussed: First, the macro time structure of treatment beams in common proton therapy facilities requires detection systems with extreme load tolerance, throughput capability, and stability against load variations. Second, the test time available for verifying the range of a single pencil beam spot is of the order of milliseconds, which limits the number of prompt gamma events that can be detected and processed. Tight event selection by passive or active collimation as applied in all imaging setups sharpens the information carried by a valid event but strongly reduces their total number. It might be better to use a multitude of uncollimated detectors acquiring time and energy signatures of every gamma hit with reasonable precision, and to pick up all the pieces of information comprised in timing, energy, and coincidence patterns irrespective of their sharpness. This would maximize the number of valid events on the expense of information sharpness, and could eventually increase the total yield of information exploitable for range verification. Some aspects of such a strategy have already been realized with the Prompt Gamma-Ray Timing (PGT) and the Prompt Gamma Peak Integration (PGPI) techniques proposed recently. Data analysis schemes for a more generalized approach have not yet been developed, but the hardware to be used can already be sketched: Prompt gamma rays should be detected with scintillation detector blocks consisting of single pixels with individual light readou