| 1. |
- Adler, Jan-Olof, et al.
(författare)
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A broad range tagging spectrometer for the MAX-laboratory
- 1997
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 388:1-2, s. 17-26
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Tidskriftsartikel (refereegranskat)abstract
- A broad range tagging spectrometer together with a new beam transport system for photonuclear experiments at the MAX-laboratory in Lund is described. The spectrometer consists of a quadrupole followed by an Elbek-type dipole and has a large momentum acceptance. It can produce both polarized and unpolarized tagged photons in the energy range 10–80 MeV with an energy resolution of about 300 keV.
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| 2. |
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| 3. |
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| 4. |
- Adler, Jan-Olof, et al.
(författare)
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The upgraded photon tagging facility at the MAX IV Laboratory
- 2013
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 715, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- A description is given of the upgraded photon tagging facility at the MAX IV Laboratory. Two magnetic spectrometers are used to momentum analyze post-bremsstrahlung electrons. The tagged photon range extends from 10 to 180 MeV with an energy resolution of about 300 keV. The system has been operated at rates up to 4 x 10(6) photons s(-1) MeV (-1). Different diagnostic tools are described as well as the experimental program.
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| 5. |
- Akkurt, I, et al.
(författare)
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Photoneutron yields from tungsten in the energy range of the giant dipole resonance
- 2003
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 48:20, s. 3345-3352
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Tidskriftsartikel (refereegranskat)abstract
- Photoneutron production on the nuclei of high-Z components of medical accelerator heads can lead to a significant secondary dose during a course of bremsstrahlung radiotherapy, However, a quantitative evaluation of secondary neutron dose requires improved data on the photoreaction yields. These have been measured as a function of photon energy, neutron energy and neutron angle for W-nat, using tagged photons at the MAX-Lab photonuclear facility in Sweden. This work presents neutron yields for W-nat(gamma, n) and compares these with the predictions of the Monte Carlo code MCNP-GN, developed specifically to simulate photoneutron production at medical accelerators.
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| 6. |
- Al Jebali, Ramsey, et al.
(författare)
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A helium gas scintillator active target for photoreaction measurements
- 2015
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 51:10
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Tidskriftsartikel (refereegranskat)abstract
- A multi-cell He gas scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 g/cm(3) at an operating pressure of 2MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of N-2 to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has a timing resolution of around 1 ns and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in He-4, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response.
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| 7. |
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| 8. |
- Fissum, Kevin, et al.
(författare)
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High-resolution measurement of the 12C(γ,p)11B reaction to excited states for Eγ=50–70MeV
- 1998
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Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 58:4, s. 2167-2173
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Tidskriftsartikel (refereegranskat)abstract
- Relative population of states in 11B following the 12C(γ,p) reaction has been measured with high resolution using the deexcitation γ-ray technique. The states near 7 MeV in 11B are clearly resolved and the measured population clarifies earlier conflicting data. Comparison of the results with new calculations indicates the importance of both one-nucleon and multinucleon processes.
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| 9. |
- Karlsson, Martin, et al.
(författare)
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Measurement of the differential cross section for the two-body photodisintegration of He-3 at theta(LAB)=90 degrees using tagged photons in the energy range 14-31 MeV
- 2009
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:4
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Tidskriftsartikel (refereegranskat)abstract
- The two-body photodisintegration of He-3 has been investigated using tagged photons with energies from 14-31 MeV at MAX-lab in Lund, Sweden. The two-body breakup channel was unambiguously identified by the (nonsimultaneous) detection of both protons and deuterons. This approach was made feasible by the overdetermined kinematic situation afforded by the tagged-photon technique. Proton-and deuteron-energy spectra were measured using four silicon surface-barrier detector telescopes located at a laboratory angle of 90 degrees with respect to the incident photon-beam direction. Average statistical and systematic uncertainties of 5.7% and 6.6% in the differential cross section were obtained for 11 photon-energy bins with an average width of 1.2 MeV. The results are compared to previous experimental data measured at comparable photon energies as well as to the results of two recent Faddeev calculations which employ realistic potential models and take into account three-nucleon forces and final-state interactions. Both the accuracy and precision of the present data are improved over those obtained in the previous measurements. The data are in good agreement with most of the previous results, and favor the inclusion of three-nucleon forces in the calculations.
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| 10. |
- Lundin, Magnus, et al.
(författare)
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Compton scattering from the deuteron and extracted neutron polarizabilities
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 90:19
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Tidskriftsartikel (refereegranskat)abstract
- Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45degrees, 125degrees, and 135degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N) + beta(N) = 17.4 +/- 3.7 and alpha(N) - beta(N) = 6.4 +/- 2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p) - beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n) = 8.8 +/- 2.4(total) +/- 3.0(model) and beta(n) = 6.5 -/+ 2.4(total) -/+ 3.0(model), respectively.
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| 11. |
- Margaryan, Ashot, et al.
(författare)
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Low-Pressure MWPC System for the detection of Alpha-Particles and Fission Fragments
- 2010
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Ingår i: Armenian Journal of Physics. - 1829-1171. ; 3:4, s. 282-291
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Tidskriftsartikel (refereegranskat)abstract
- A low-pressure, position-sensitive, multi-wire proportional chamber (LPMWPC) system with an active area 12×12 cm 2 for the detection of heavy nuclear fragments, has been developed for use in tagged photon beam experiments. The LPMWPC system can be operated in single as well as double step operational modes. In the case of double step operational mode with a high gas amplification factor, signals from α-particles reside well above the electronic noise. Typical energy loss spectra of alpha particles and fission fragments (FF) obtained from a 252 Cf source are shown and discussed. The pulse height distributions of α-particles have a Landau distribution shape, while the pulse height distribution of FFs differs from Gaussian shape. It has long tails at both low-and high-energy sides. The average pulse height ratio of alpha particles and FF's is close to the theoretical value and amounts to about 1/80.
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| 12. |
- Morrow, S A, et al.
(författare)
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High-resolution study of the C-12(gamma,p gamma')B-11 reaction using a HpGe detector to resolve excited states of B-11 through the observation of their gamma-ray decays
- 2006
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Ingår i: Physical Review C: covering nuclear physics. ; 73
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Tidskriftsartikel (refereegranskat)abstract
- Relative populations of states in 11B following the 12C(,p)11B reaction have been measured with high resolution using a 70% HpGe detector to observe decay rays from the residual nucleus. The triplet of states near 7 MeV in 11B are resolved and the measured populations compared to previous data. The analysis includes a consideration of -proton angular correlations, which was not made in the previous measurement. The new and previous results corrected for angular correlation effects agree reasonably well with calculations that include one- and two-body nuclear currents, pion exchange, and currents, under the assumption that the photons are mainly absorbed on exchanged pions.
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| 13. |
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| 14. |
- Nilsson, Björn, et al.
(författare)
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Near-threshold measurement of the He-4(gamma,n) reaction
- 2005
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 626:1-4, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- A near-threshold He-4(gamma, n) cross-section measurement has been performed at MAX-lab. Tagged photons from 23 < Ey < 42 MeV were directed toward a liquid He-4 target, and neutrons were detected by time-of-flight in two liquid-scintillator arrays. Seven-point angular distributions were measured for eight photon energies. The results are compared to experimental data measured at comparable energies and Recoil-Corrected Continuum Shell Model, Resonating Group Method, and recent Hyperspherical-Harmonic Expansion calculations. The angle-integrated cross-section data are peaked at a photon energy of about 28 MeV, in disagreement with the value recommended by Calarco, Berman, and Donnelly in 1983.
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| 15. |
- Proff, S, et al.
(författare)
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Electromagnetic polarizabilities of nucleons bound in 40Ca, 16O and 4He
- 1999
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Ingår i: Nuclear Physics A. - 0375-9474. ; 646:1, s. 67-82
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Tidskriftsartikel (refereegranskat)abstract
- Differential cross sections for elastic scattering of photons have been measured for 40Ca at energies of 58 and 74 MeV and for 16O and 4He at 61 MeV, in the angular range from 45° to 150°. Evidence is obtained that there are no significant in-medium modifications of the electromagnetic polarizabilities except for those originating from meson exchange currents.
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| 16. |
- Reiter, A., et al.
(författare)
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Measurement and simulation of the neutron response of the Nordball liquid scintillator array
- 2006
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 565:2, s. 753-762
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Tidskriftsartikel (refereegranskat)abstract
- The response of the liquid scintillator array Nordball to neutrons in the energy range 1.5 < T-n < 10 MeV has been measured by time of flight using a Cf-252 fission source. Fission fragments were detected by means of a thin-film plastic scintillator. The measured differential and integral neutron detection efficiencies agree well with predictions of a Monte Carlo simulation of the detector which models geometry accurately and incorporates the measured, non-linear proton light output as a function of energy. The ability of the model to provide systematic corrections to photoneutron cross-sections, measured by Nordball at low energy, is tested in a measurement of the two-body deuteron photodisintegration cross-section in the range E-gamma = 14-18 MeV. After correction the present H-2 (gamma, n)p measurements agree well with a published evaluation of the large body of H-2(gamma, p)n data. (c) 2006 Elsevier B.V. All rights reserved.
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| 17. |
- Sims, D. A., et al.
(författare)
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The He(γ,n) reaction: a potential testing ground for the alpha-particle wavefunction
- 1998
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Ingår i: Physics Letters B. - 0370-2693. ; 442:1-4, s. 43-47
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Tidskriftsartikel (refereegranskat)abstract
- Differential cross sections (σ(Eγ,θn)) for the He(γ,n) reaction have been measured at Eγ=50–71 MeV and θn=30–120°. These data are compared with theoretical predictions where a microscopic calculation of the He and He wavefunctions has been made within the Alt-Grassberger-Sandhas, integral-equation formalism.
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| 18. |
- Sims, D. A., et al.
(författare)
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(γ,n) study of the isovector quadrupole resonance in 40Ca
- 1997
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Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 55:3, s. 1288-1294
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Tidskriftsartikel (refereegranskat)abstract
- The forward-to-backward asymmetry of neutrons emitted in the 40Ca(γ,n0) reaction was measured at photon energies in the range of 27–50 MeV. An energy-dependent asymmetry was observed that is interpreted as evidence of interference between the isovector quadrupole resonance and the giant dipole resonance. Data analysis in terms of semiclassical and direct-semidirect models estimate the isovector quadrupole resonance to be at an excitation energy of 31.0±1.5 MeV, with a width of 16.0±1.5 MeV, and exhausting most of the energy-weighted sum rule for the isovector quadrupole resonance.
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| 19. |
- Zanini, A, et al.
(författare)
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Monte Carlo simulation of the photoneutron field in linac radiotherapy treatments with different collimation systems
- 2004
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 49:4, s. 571-582
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Tidskriftsartikel (refereegranskat)abstract
- Bremsstrahlung photon beams produced by linac accelerators are currently the most commonly used method of radiotherapy for tumour treatments. When the photon energy exceeds 10 MeV the patient receives an undesired dose due to photoneutron production in the accelerator head. In the last few decades, new sophisticated techniques such as multileaf collimators have been used for a better definition of the target volume. In this case it is crucial to evaluate the photoneutron dose produced after giant dipole resonance (GDR) excitation of the high Z materials (mainly tungsten and lead) constituting the collimator leaves in view of the optimization of the radiotherapy treatment. A Monte Carlo approach has been used to calculate,the photoneutron dose arising from the GDR reaction during radiotherapy with energetic photon beams. The simulation has been performed using the code MCNP4B-GN which is based on MCNP4B, but includes a new routine GAMMAN to model photoneutron production. Results for the facility at IRCC (Istituto per la Ricerca e la Cura del Cancro) Candiolo (Turin), which is based on 18 MV x-rays from a Varian Clinac 2300 C/D, are presented for a variety of different collimator configurations.
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