| 1. |
- Blomgren, Jan, et al.
(författare)
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Progress in Dosimetry of Neutrons and Light Nuclei
- 2007
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 126:1-4, s. 1-2
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Liamsuwan, Thiansin, et al.
(författare)
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Microdosimetry of proton and carbon ions
- 2014
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Ingår i: Medical physics (Lancaster). - : Wiley. - 0094-2405 .- 2473-4209. ; 41:8, s. 239-250
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate microdosimetry properties of 160 MeV/u protons and 290 MeV/u C-12 ion beams in small volumes of diameters 10-100 nm. Methods: Energy distributions of primary particles and nuclear fragments in the beams were calculated from simulations with the general purpose code SHIELD-HIT, while energy depositions by monoenergetic ions in nanometer volumes were obtained from the event-by-event Monte Carlo track structure ion code PITS99 coupled with the electron track structure code KURBUC. Results: The results are presented for frequencies of energy depositions in cylindrical targets of diameters 10-100 nm, dose distributions (y) over bar (D) in lineal energy y, and dose-mean lineal energies YD For monoenergetic ions, the hp was found to increase with an increasing target size for high-linear energy transfer (LET) ions, but decrease with an increasing target size for low-LET ions. Compared to the depth dose profile of the ion beams, the maximum of the hp depth profile for the 160 MeV proton beam was located at similar to 0.5 cm behind the Bragg peak maximum, while the PD peak of the 290 MeV/u C-12 beam coincided well with the peak of the absorbed dose profile. Differences between the (y) over bar (D) and dose-averaged linear energy transfer (LETD) were large in the proton beam for both target volumes studied, and in the C-12 beam for the 10 nm diameter cylindrical volumes. The (y) over bar (D) determined for 100 run diameter cylindrical volumes in the C-12 beam was approximately equal to the LETD. The contributions from secondary particles to the (y) over bar (D) of the beams are presented, including the contributions from secondary protons in the proton beam and from fragments with atomic number Z = 1-6 in the C-12 beam. Conclusions: The present investigation provides an insight into differences in energy depositions in subcellular-size volumes when irradiated by proton and carbon ion beams. The results are useful for characterizing ion beams of practical importance for biophysical modeling of radiation-induced DNA damage response and repair in the depth profiles of protons and carbon ions used in radiotherapy.
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| 3. |
- Lillhök, Jan Erik, 1968-
(författare)
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The microdosimetric variance-covariance method used for beam quality characterization in radiation protection and radiation therapy
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radiation quality is described by the RBE (relative biological effectiveness) that varies with the ionizing ability of the radiation. Microdosimetric quantities describe distributions of energy imparted to small volumes and can be related to RBE. This has made microdosimetry a powerful tool for radiation quality determinations in both radiation protection and radiation therapy. The variance-covariance method determines the dose-average of the distributions and has traditionally been used with two detectors to correct for beam intensity variations. Methods to separate dose components in mixed radiation fields and to correct for beam variations using only one detector have been developed in this thesis. Quality factor relations have been optimized for different neutron energies, and a new algorithm that takes single energy deposition events from densely ionizing radiation into account has been formulated. The variance-covariance technique and the new methodology have been shown to work well in the cosmic radiation field onboard aircraft, in the mixed photon and neutron fields in the nuclear industry and in pulsed fields around accelerators.The method has also been used for radiation quality characterization in therapy beams. The biological damage is related to track-structure and ionization clusters and requires descriptions of the energy depositions in nanometre sized volumes. It was shown that both measurements and Monte Carlo simulation (condensed history and track-structure) are needed for a reliable nanodosimetric beam characterization. The combined experimental and simulated results indicate that the dose-mean of the energy imparted to an object in the nanometre region is related to the clinical RBE in neutron, proton and photon beams. The results suggest that the variance-covariance technique and the dose-average of the microdosimetric quantities could be well suited for describing radiation quality also in therapy beams.
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| 4. |
- Lindborg, Jenny, et al.
(författare)
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Systemperspektiv för effektiv produktion och användning av vätgas viakoppling till fjärrvärme
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta projekt har analyserat sektorkopplingars möjligheter att ta vara på restflöden som genereras vid produktion av vätgas genom elektrolys samt hur dessa flöden kan generera ekonomiska och systemmässiga fördelar. Förutsättningen har varit att all el köps in externt för spotpris. Projektet har redovisat i detalj hur restvärmen, som uppstår i elektrolysen, kan tillgodogöras som fjärrvärme och därigenom öka processens verkningsgrad från cirka 66 till 95 %. EU:s mål om produktion av 10 miljoner ton vätgas per år till 2030 innebär att det bildas 230 TWh restvärme, motsvarande fyra gånger Sveriges totala fjärrvärmeenergi. Det visar potentialen och vikten av att värmeöverskottet nyttjas i framtida investeringar. För varje kilo vätgas som produceras bildas åtta kilo syrgas, som kan användas i för att förbättra förbränningen i en avfallspanna. Alternativt kan syrgasen transporteras till ett närliggande vattenreningsverk, vilket minskar elanvändningen för de pumpar som idag cirkulerar luft i de biologiska reningsstegen. Svenska kraftnät har skapat flera olika marknader för systemtjänster. Vätgasproduktion har goda förutsättningar att delta, särskilt med FCR-D. Analyserna visar att intäkterna från dessa tjänster kan vara större än både restvärmen och syrgasen, förutsatt att restvärmen inte ersätter bränslen som har en högre kostnadsprofil, som exempelvis bio-olja eller pellets. I dessa fall får restvärmen ett betydligt högre värde. Sektorkopplingen mot fjärrvärme skapar ett resurseffektivt energisystem där alla restflöden kan komma till nytta. Vätgaslager kan också bidra till ett mer robust och resilient energisystem, med möjligheter att förse kritiska verksamheter med reservkraft eller för att starta lokala elnät i ö-drift. För bästa lönsamhet, utifrån befintliga data om elpriser och vätgasens värde, bör vätgasen säljas vidare som bränsle till tunga transport eller som råvara till industrier istället för att lagras för senare omvandling tillbaka till el. I en framtid, där behov av elgenerering för balanskraft kan öka och samtidigt krävas vara koldioxidneutral, kan dock situationen bli annorlunda. Baserat på indata och förutsättningar från omvärldsanalyserna visar att kostnaden för att producera vätgas (kr/kg) minimeras när elektrolysen är i drift cirka 80 % av årets timmar eftersom avskrivningskostnaderna annars blir högre i relation till producerad mängd vätgas. Förutsatt avsättning för vätgasen bör produktionen dras ner enbart vid de allra högsta elpriserna. Scenariot ”gas-to-power” har inte visat sig lönsamt, baserat på de förutsättningar som använts. Historiska elpriser har inte varit tillräckligt höga, tillräckligt ofta för att en extra investering i en gasturbin eller bränslecell ska betala sig. Samtidigt kan det vara missvisande att jämföra priser där dagens fossila bränslen ingår eftersom dessa bränslen på sikt inte är något alternativ. Även om sektorkopplingen till fjärrvärme ökar intäktsmöjligheterna för vätgasproduktion så finns fortfarande ett antal osäkra parametrar som påverkar lönsamheten och investeringsviljan. Dessa specificeras och diskuteras i denna och dess underliggande rapporter.
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| 5. |
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| 6. |
- Lindborg, Lennart, et al.
(författare)
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Nanodosimetry and RBE values in radiotherapy
- 2015
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Ingår i: Radiation Protection Dosimetry. - : OXFORD UNIV PRESS. - 0144-8420 .- 1742-3406. ; 166:1-4, s. 339-342
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Tidskriftsartikel (refereegranskat)abstract
- In a recent paper, the authors reported that the dose mean lineal energy, (y) over bar (D) in a volume of about 10-15 nm is approximately proportional to the alpha-parameter in the linear-quadratic relation used in fractionated radiotherapy in both low- and high-LET beams. This was concluded after analyses of reported radiation weighting factors, W-isoE (clinical RBE values), and (y) over bar (D) values in a large range of volumes. Usually, microdosimetry measurements in the nanometer range are difficult; therefore, model calculations become necessary. In this paper, the authors discuss the calculation method. A combination of condensed history Monte Carlo and track structure techniques for calculation of mean lineal energy values turned out to be quite useful. Briefly, the method consists in weighting the relative dose fractions of the primary and secondary charged particles with their respective energy-dependent dose mean lineal energies. The latter were obtained using a large database of Monte Carlo track structure calculations.
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| 7. |
- Scaini, Anna, et al.
(författare)
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Pathways from research to sustainable development: Insights from ten research projects in sustainability and resilience
- 2024
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Ingår i: AMBIO. - : SPRINGER. - 0044-7447 .- 1654-7209.
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Tidskriftsartikel (refereegranskat)abstract
- Drawing on collective experience from ten collaborative research projects focused on the Global South, we identify three major challenges that impede the translation of research on sustainability and resilience into better-informed choices by individuals and policy-makers that in turn can support transformation to a sustainable future. The three challenges comprise: (i) converting knowledge produced during research projects into successful knowledge application; (ii) scaling up knowledge in time when research projects are short-term and potential impacts are long-term; and (iii) scaling up knowledge across space, from local research sites to larger-scale or even global impact. Some potential pathways for funding agencies to overcome these challenges include providing targeted prolonged funding for dissemination and outreach, and facilitating collaboration and coordination across different sites, research teams, and partner organizations. By systematically documenting these challenges, we hope to pave the way for further innovations in the research cycle.
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| 8. |
- Söderberg, Jonas, 1969-
(författare)
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Fast neutron dosimetry : a study of basic dosimetric properties of fast-neutrons for external beam radiotherapy and problems associated with corrections of measured charged particle cross-sections
- 2001
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Basic dosimetric properties of fast-neutron beams with energies ≤80 MeV were explored using Monte Carlo techniques. Elementary pencil-beam dose distributions taking into account transport of all relevant types of released charged particles (protons, deuterons, tritons, 3He and a particles) were calculated and used to derive several absorbed dose distributions. Broad-beam depth doses in phantoms of different materials were compared and scaling factors calculated to convert absorbed dose in one material to absorbed dose in another. The scaling factors were in good agreement with available published data and show that water is a good substitute for soft tissue even at neutron energies as high as 80 Me V. The inherent penumbra and fraction of absorbed dose due to photons were also studied, and found to be consistent with published values.Treatment planning in fast-neutron therapy is commonly performed using dose calculation algorithms designed for photon beam therapy. These algorithms have limitations in the physical models when applied to neutron beams. Monte Carlo derived neutron pencil-beam kernels were parameterized and implemented into the photon dose calculation algorithms of the TMS (MDS Nordion) treatment planning system. It was shown that these algorithms yield good results in homogeneous water media. However, the heterogeneity correction method of the photon dose calculation algorithm failed to calculate correct results in heterogeneous media for neutron beams.Fundamental cross-section data are needed when calculating absorbed doses. To achieve results with adequate accuracy, neutron cross-sections are still not sufficiently well known. At the The Svedberg Laboratory in Uppsala, Sweden, an experimental facility has been designed to measure neutron-induced charged-particle production cross-sections for (n,xp), (n,xd), (n,xt), (n,x3He) and (n,xα) reactions at neutron energies up to 100 MeV. In order to derive the energy distributions of charged particles generated inside the production target, the measured data have to be corrected for the energy lost by the particles in the target. In this work a code (CRAWL) was developed for the reconstruction of the true spectrum. It uses a stripping method. With the limitation of reduced energy resolution, results using CRAWL compare well with those of other methods.
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