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Boersma, David J.
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Publications (10 of 45) Show all publications
Almhagen, E., Boersma, D. J., Nyström, H. & Ahnesjö, A. (2018). A beam model for focused proton pencil beams. Physica medica (Testo stampato), 52, 27-32
Open this publication in new window or tab >>A beam model for focused proton pencil beams
2018 (English)In: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 52, p. 27-32Article in journal (Refereed) Published
Abstract [en]

Introduction: We present a beam model for Monte Carlo simulations of the IBA pencil beam scanning dedicated nozzle installed at the Skandion Clinic. Within the nozzle, apart from entrance and exit windows and the two ion chambers, the beam traverses vacuum, allowing for a beam that is convergent downstream of the nozzle exit. Materials and methods: We model the angular, spatial and energy distributions of the beam phase space at the nozzle exit with single Gaussians, controlled by seven energy dependent parameters. The parameters were determined from measured profiles and depth dose distributions. Verification of the beam model was done by comparing measured and GATE acquired relative dose distributions, using plan specific log files from the machine to specify beam spot positions and energy. Results: GATE-based simulations with the acquired beam model could accurately reproduce the measured data. The gamma index analysis comparing simulated and measured dose distributions resulted in > 95% global gamma index pass rates (3%/2 mm) for all depths. Conclusion: The developed beam model was found to be sufficiently accurate for use with GATE e.g. for applications in quality assurance (QA) or patient motion studies with the IBA pencil beam scanning dedicated nozzles.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Proton therapy, Monte Carlo, Beam model
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-364002 (URN)10.1016/j.ejmp.2018.06.007 (DOI)000442110000004 ()30139606 (PubMedID)
Funder
Swedish Childhood Cancer FoundationSwedish Radiation Safety Authority
Available from: 2018-10-30 Created: 2018-10-30 Last updated: 2018-10-30Bibliographically approved
Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., . . . Zoll, M. (2017). PINGU: a vision for neutrino and particle physics at the South Pole. Journal of Physics G: Nuclear and Particle Physics, 44(5), Article ID 054006.
Open this publication in new window or tab >>PINGU: a vision for neutrino and particle physics at the South Pole
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2017 (English)In: Journal of Physics G: Nuclear and Particle Physics, ISSN 0954-3899, E-ISSN 1361-6471, Vol. 44, no 5, article id 054006Article in journal (Refereed) Published
Abstract [en]

The Precision IceCube Next Generation Upgrade (PINGU) is a proposed low-energy in-fill extension to the IceCube Neutrino Observatory. With detection technology modeled closely on the successful IceCube example, PINGU will provide a 6 Mton effective mass for neutrino detection with an energy threshold of a few GeV. With an unprecedented sample of over 60 000 atmospheric neutrinos per year in this energy range, PINGU will make highly competitive measurements of neutrino oscillation parameters in an energy range over an order of magnitude higher than long-baseline neutrino beam experiments. PINGU will measure the mixing parameters theta(23) and Delta m(32)(2), including the octant of theta(23) for a wide range of values, and determine the neutrino mass ordering at 3 sigma median significance within five years of operation. PINGU's high precision measurement of the rate of nu(T) appearance will provide essential tests of the unitarity of the 3 x 3 PMNS neutrino mixing matrix. PINGU will also improve the sensitivity of searches for low mass dark matter in the Sun, use neutrino tomography to directly probe the composition of the Earth's core, and improve IceCube's sensitivity to neutrinos from Galactic supernovae. Reoptimization of the PINGU design has permitted substantial reduction in both cost and logistical requirements while delivering performance nearly identical to configurations previously studied.

Keywords
neutrino oscillations, atmospheric neutrinos, IceCube Neutrino Observatory, PINGU
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-322098 (URN)10.1088/1361-6471/44/5/054006 (DOI)000399127900001 ()
Funder
Swedish Research CouncilSwedish Polar Research SecretariatSwedish National Infrastructure for Computing (SNIC)Knut and Alice Wallenberg FoundationGerman Research Foundation (DFG)Australian Research Council
Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2019-05-21Bibliographically approved
Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., . . . Zoll, M. (2017). The Contribution Of Fermi-2Lac Blazars To Diffuse Tev-Pev Neutrino Flux. Astrophysical Journal, 835(1), Article ID 45.
Open this publication in new window or tab >>The Contribution Of Fermi-2Lac Blazars To Diffuse Tev-Pev Neutrino Flux
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2017 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 835, no 1, article id 45Article in journal (Refereed) Published
Abstract [en]

The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the 2LAC catalog. No significant excess is observed, and upper limits for the cumulative flux from these populations are obtained. These constrain the maximum contribution of 2LAC blazars to the observed astrophysical neutrino flux to 27% or less between around 10 TeV and 2 PeV, assuming the equipartition of flavors on Earth and a single power-law spectrum with a spectral index of -2.5. We can still exclude the fact that 2LAC blazars (and their subpopulations) emit more than 50% of the observed neutrinos up to a spectral index as hard as -2.2 in the same energy range. Our result takes into account the fact that the neutrino source count distribution is unknown, and it does not assume strict proportionality of the neutrino flux to the measured 2LAC gamma-ray signal for each source. Additionally, we constrain recent models for neutrino emission by blazars.

Keywords
astroparticle physics, BL Lacertae objects_ general, gamma rays_ galaxies, methods_ data analysis, neutrinos, quasars_ general
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-316947 (URN)10.3847/1538-4357/835/1/45 (DOI)000393455400045 ()
Funder
Swedish Research CouncilSwedish Polar Research SecretariatKnut and Alice Wallenberg FoundationGerman Research Foundation (DFG)
Available from: 2017-03-10 Created: 2017-03-10 Last updated: 2017-05-15Bibliographically approved
Aartsen, M. G., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., Ahrens, M., . . . Zoll, M. (2017). The IceCube Neutrino Observatory: instrumentation and online systems. Journal of Instrumentation, 12, Article ID P03012.
Open this publication in new window or tab >>The IceCube Neutrino Observatory: instrumentation and online systems
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2017 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 12, article id P03012Article in journal (Refereed) Published
Abstract [en]

The IceCube Neutrino Observatory is a cubic-kilometer-scale high-energy neutrino detector built into the ice at the South Pole. Construction of IceCube, the largest neutrino detector built to date, was completed in 2011 and enabled the discovery of high-energy astrophysical neutrinos. We describe here the design, production, and calibration of the IceCube digital optical module (DOM), the cable systems, computing hardware, and our methodology for drilling and deployment. We also describe the online triggering and data filtering systems that select candidate neutrino and cosmic ray events for analysis. Due to a rigorous pre-deployment protocol, 98.4% of the DOMs in the deep ice are operating and collecting data. IceCube routinely achieves a detector uptime of 99% by emphasizing software stability and monitoring. Detector operations have been stable since construction was completed, and the detector is expected to operate at least until the end of the next decade.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
Large detector systems for particle and astroparticle physics, Neutrino detectors, Online farms and online filtering, Trigger concepts and systems (hardware and software)
National Category
Subatomic Physics Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-359268 (URN)10.1088/1748-0221/12/03/P03012 (DOI)000406997600012 ()
Funder
Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)Knut and Alice Wallenberg FoundationGerman Research Foundation (DFG)Australian Research Council
Available from: 2018-09-06 Created: 2018-09-06 Last updated: 2019-05-21Bibliographically approved
Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., . . . Zoll, M. (2016). All-flavour search for neutrinos from dark matter annihilations in the Milky Way with IceCube/DeepCore. European Physical Journal C, 76(10), Article ID 531.
Open this publication in new window or tab >>All-flavour search for neutrinos from dark matter annihilations in the Milky Way with IceCube/DeepCore
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2016 (English)In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 76, no 10, article id 531Article in journal (Refereed) Published
Abstract [en]

We present the first IceCube search for a signal of dark matter annihilations in the Milky Way using all-flavour neutrino-induced particle cascades. The analysis focuses on the DeepCore sub-detector of IceCube, and uses the surrounding IceCube strings as a veto region in order to select starting events in the DeepCore volume. We use 329 live-days of data from IceCube operating in its 86-string configuration during 2011-2012. No neutrino excess is found, the final result being compatible with the background-only hypothesis. From this null result, we derive upper limits on the velocity-averaged self-annihilation cross-section, , for dark matter candidate masses ranging from 30 GeV up to 10 TeV, assuming both a cuspy and a flat-cored dark matter halo profile. For dark matter masses between 200 GeV and 10 TeV, the results improve on all previous IceCube results on , reaching a level of 10 cm s, depending on the annihilation channel assumed, for a cusped NFW profile. The analysis demonstrates that all-flavour searches are competitive with muon channel searches despite the intrinsically worse angular resolution of cascades compared to muon tracks in IceCube.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:uu:diva-312123 (URN)10.1140/epjc/s10052-016-4375-3 (DOI)000388972200001 ()
Available from: 2017-01-04 Created: 2017-01-04 Last updated: 2019-05-21Bibliographically approved
Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., . . . Zoll, M. (2016). Anisotropy In Cosmic-Ray Arrival Directions In The Southern Hemisphere Based On Six Years Of Data From The Icecube Detector. Astrophysical Journal, 826(2), Article ID 220.
Open this publication in new window or tab >>Anisotropy In Cosmic-Ray Arrival Directions In The Southern Hemisphere Based On Six Years Of Data From The Icecube Detector
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2016 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 826, no 2, article id 220Article in journal (Refereed) Published
Abstract [en]

The IceCube Neutrino Observatory accumulated a total of 318 billion cosmic-ray-induced muon events between 2009 May and 2015 May. This data set was used for a detailed analysis of the sidereal anisotropy in the arrival directions of cosmic rays in the TeV to PeV energy range. The observed global sidereal anisotropy features large regions of relative excess and deficit, with amplitudes of the order of 10(-3) up to about 100 TeV. A decomposition of the arrival direction distribution into spherical harmonics shows that most of the power is contained in the low-multipole (l <= 4) moments. However, higher multipole components are found to be statistically significant down to an angular scale of less than 10 degrees, approaching the angular resolution of the detector. Above 100 TeV, a change in the morphology of the arrival direction distribution is observed, and the anisotropy is characterized by a wide relative deficit whose amplitude increases with primary energy up to at least 5 PeV, the highest energies currently accessible to IceCube. No time dependence of the large-and small-scale structures is observed in the period of six years covered by this analysis. The high-statistics data set reveals more details of the properties of the anisotropy and is potentially able to shed light on the various physical processes that are responsible for the complex angular structure and energy evolution.

Keywords
astroparticle physics, cosmic rays
National Category
Astronomy, Astrophysics and Cosmology Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-308242 (URN)10.3847/0004-637X/826/2/220 (DOI)000381977900120 ()
Funder
Swedish Research CouncilSwedish Polar Research SecretariatSwedish National Infrastructure for Computing (SNIC)Knut and Alice Wallenberg FoundationGerman Research Foundation (DFG)Australian Research Council
Available from: 2016-11-24 Created: 2016-11-24 Last updated: 2017-11-29Bibliographically approved
Aartsen, M. G., Abraham, K., Ackermann, M., Adams, J., Aguilar, J. A., Ahlers, M., . . . Zoll, M. (2016). Characterization of the atmospheric muon flux in IceCube. Astroparticle physics, 78, 1-27
Open this publication in new window or tab >>Characterization of the atmospheric muon flux in IceCube