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Sökning: WFRF:(Schröder Bent)

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1.
  • Adler, Jan-Olof, et al. (författare)
  • A broad range tagging spectrometer for the MAX-laboratory
  • 1997
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 388:1-2, s. 17-26
  • 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.
  • Adler, Jan-Olof, et al. (författare)
  • The upgraded photon tagging facility at the MAX IV Laboratory
  • 2013
  • 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
  • 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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3.
  • Akkurt, I, et al. (författare)
  • Photoneutron yields from tungsten in the energy range of the giant dipole resonance
  • 2003
  • Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 48:20, s. 3345-3352
  • 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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4.
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5.
  • Briscoe, W. J., et al. (författare)
  • Nuclear physics program at MAX-lab
  • 2009
  • Ingår i: Chinese Physics C. - : IOP Publishing. - 0899-9996 .- 1674-1137. ; 33:12, s. 1159-1166
  • Konferensbidrag (refereegranskat)abstract
    • The upgrade of the MAX-lab Injector and the construction of MAX III, provided the opportunity for upgrading the tagged-photon facility and thus lead to the possibility of more extensive program in nuclear physics research This upgrade increased the injected electron energy to all eventual maximum of 250 MeV and allows for the extraction of electrons from the MAX I ring operated in the stretcher mode The first stretched bean was delivered in September 2005. The tagged-photon facility was commissioned in parallel with the commissioning of new experimental equipment. The PAC approved experimental program is current in progress, including measurement of pion photoproduction below the Delta(1232) The efforts at the tagged photon-facility are pursed within all international collaboration with around fifty members
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6.
  • Burdeinyi, D., et al. (författare)
  • Cross section asymmetry of two-body carbon disintegration 12C(γ,p)11B with polarized photons at energy 40–50 MeV
  • 2017
  • Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 957, s. 321-331
  • Tidskriftsartikel (refereegranskat)abstract
    • The cross section asymmetry of C12(γ,p01)B11 and C12(γ,p2−6)B11 reactions has been studied at the energy range 40–55 MeV, using linearly polarized tagged photons of the MAX-lab facility. The asymmetry of the C12(γ,p01)B11 processes, which assume the one-body mechanism of the reaction, is Σ≈0.82±0.05 for photon energies 45–50 MeV. The asymmetry for the C12(γ,p2−6)B11 reactions, which produce a maximum at excitation energy ∼6 MeV, is Σ≈0.53±0.13 for a photon energy 49 MeV. It is close to the asymmetry of reaction of the free deuteron photodisintegration, and can be resulted from the two-body mechanism of the photon absorption.
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7.
  • Erni, W., et al. (författare)
  • Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
  • 2013
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
  • Tidskriftsartikel (refereegranskat)abstract
    • This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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8.
  • Feldman, G., et al. (författare)
  • Compton scattering from deuterium and the polarizabilities of the neutron
  • 2008
  • Ingår i: Few-Body Systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 44:1-4, s. 325-328
  • Konferensbidrag (refereegranskat)abstract
    • A new program of Compton scattering on deuterium is under way at the tagged-photon facility at MAX-Lab in Lund, Sweden. We will measure differential cross sections between 60A degrees and 150A degrees over the photon energy range 60-115 MeV in 5 MeV steps, with the ultimate goal of obtaining new precision information on the electric and magnetic polarizabilities of the neutron.
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9.
  • Fissum, Kevin, et al. (författare)
  • High-resolution measurement of the 12C(γ,p)11B reaction to excited states for Eγ=50–70MeV
  • 1998
  • Ingår i: Physical Review C: covering nuclear physics. - 2469-9985. ; 58:4, s. 2167-2173
  • 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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10.
  • Fissum, Kevin, et al. (författare)
  • The Coherent Bremsstrahlung Beam at MAX-lab Facility
  • 2008
  • Ingår i: Charged and Neutral Particles Channeling Phenomena Channeling 2008 : Proceedings of the 51st Workshop of the INFN ELOISATRON Project - Proceedings of the 51st Workshop of the INFN ELOISATRON Project. - : WORLD SCIENTIFIC. ; , s. 49-61
  • Konferensbidrag (refereegranskat)abstract
    • The linearly polarized photon beam for photonuclear researches has been produced at MAX-lab facility on the base of coherent bremsstrahlung process of electrons in a diamond crystal. Test experiments have been performed at electron energies 143.9 and 192.7 MeV with a diamond crystal 0.1 mm thick. The measured coherent bremsstrahlung spectra demonstrate typical features to be observed at higher electron energies. The polarization ~35% was obtained at coherent peak energy of ~60 MeV. The experiments have shown that produced polarized photon beam can be used for photonuclear investigations at energy range up to 60 MeV. To extend the energy range it is necessary to increase maximal energy of the electron beam up to 250 MeV.
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11.
  • Ganenko, V., et al. (författare)
  • Linearly polarized photon beam at MAX-lab
  • 2014
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 763, s. 137-149
  • Tidskriftsartikel (refereegranskat)abstract
    • A linearly polarized photon beam has been produced at MAX-lab using the coherent bremsstrahlung of electrons with an energy of 192.6 MeV in a 0.1 mm thick diamond crystal. The intensity and shape of the coherent maxima and their dependence on the crystal orientation are similar to the features observed at higher electron energies (similar to 1 GeV) and are well described by coherent bremsstrahlung theory. The linear polarization of the uncollimated beam at the coherent peak energy approximate to 50-60 MeV is about 20% and can be increased to 40-45% if collimation of half the characteristic angle is used At present the degree of polarization is high enough to allow the study of polarization observables in photo-nuclear reactions at MAX-lab in the energy range from Giant Dipole Resonance up to approximate to 80 MeV. (C) 2014 Elsevier B.V. All rights reserved.
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12.
  • Ganenko, V., et al. (författare)
  • Production of linearly polarized photon beam at MAX-lab
  • 2009
  • Ingår i: Voprosy Atomnoj Nauki i Techniki. - 1562-6016. ; :3, s. 95-102
  • Tidskriftsartikel (refereegranskat)abstract
    • Spectra of coherent bremsstrahlung from the diamond crystal in the laboratory MAX-lab on the accelerator MAX-I are measured at the energy of the electronic beam 144 MeV. First in the laboratory MAX-lab a source of the polarized photon radiation was created. Photon spectra were compared with theoretical calculations, that allow to estimate a magnitude of photon polarization, which is sufficient, for performing the nuclear experiments in the intermediate energy range.
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13.
  • Golubev, Pavel, et al. (författare)
  • Pion Emission in H-2,C-12,Al-27(gamma,pi+) Reactions at Threshold
  • 2008
  • Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 806:1-4, s. 216-229
  • Tidskriftsartikel (refereegranskat)abstract
    • The very first data from MAX-lab in Lund, Sweden on pion photoproduction at threshold energies are presented. The decrease of the total π+ yield in γ+12C, 27Al reactions below 200 MeV as well as the dσ/dΩ cross-section data essentially follow the predictions of an intranuclear-cascade model with an attractive potential for the pion–nucleus interaction. However, View the MathML source, cross-section data at 176 MeV show deviations which call for refinements of the model and possibly also for the inclusion of coherent pion-production mechanisms.
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14.
  • Karlsson, Martin, et al. (författare)
  • 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
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 80:4
  • 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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15.
  • Lee, V., et al. (författare)
  • Imaging high energy photons with PILATUS II at the tagged photon beam at MAX-lab
  • 2009
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 603:3, s. 379-383
  • Tidskriftsartikel (refereegranskat)abstract
    • In photonuclear experiments precise location of the photon beam relative to the experimental sample is critical. Previously used techniques such as using photographic film to identify the position, intensity and centroid of the beam is time-consuming and a faster method is required. PILATUS is a single-photon-counting pixel detector developed at the Paul Scherrer Institute (PSI), Switzerland. It is a silicon-based, two-dimensional detector with a large dynamic range and zero readout noise. Designed as an X-ray detector, its optimal quantum efficiency is between 3 and 30 keV. This paper reports measurements carried out at the MAX-lab tagged photon facility in Lund, Sweden. The beam endpoint energy of approximately 200 MeV is far above the designed optimal energy detection range of PILATUS, and provides a critical test of the use of PILATUS under high energy conditions. The detector was placed in the photon beam and images were taken both downstream of other experiments, and in close range of a 19 mm collimator. The successful measurements demonstrate the versatility and robustness of the detector and provide an effective way of quickly and accurately monitoring beam position and profile in real time. (C) 2009 Elsevier B.V. All rights reserved.
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16.
  • Lundin, Magnus, et al. (författare)
  • Compton scattering from the deuteron and extracted neutron polarizabilities
  • 2003
  • Ingår i: Physical Review Letters. - 1079-7114. ; 90:19
  • 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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17.
  • Makonyi, Karoly, et al. (författare)
  • Evaluating vacuum phototriodes designed for the PANDA electromagnetic calorimeter
  • 2014
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 763, s. 36-43
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work properties of a vacuum phototriode (VPT) and preamplifier unit designed for the electromagnetic calorimeter of the PANDA experiment being built at FAIR are investigated. With the use of lead tungstate and lanthanium bromide scintillators the VPT properties are studied at low photon energies, from tens of key in the lanthanium bromide measurements and between 10 MeV and 60 MeV in the lead tungstate measurements. At these energies the noise of the VPT unit can be expected to influence its performance significantly. It is shown that the noise contribution to the measured energy resolution, under optimal conditions, is consistent with a fluctuation of (one standard deviation) approximately 200 electrons at the VPT anode. For a lead tungstate crystal this is equivalent to a noise of 1.2 MeV. For lanthanium bromide this makes it possible to use VPTs for gamma ray spectroscopy above a few hundreds of keV without noticeable effects on the energy resolution compared to measurements with a standard photomultiplier.
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18.
  • Marcks von Wurtemberg, Klas, et al. (författare)
  • The response of lead-tungstate scintillators (PWO) to photons with energies in the range 13 MeV-64 MeV
  • 2012
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 679, s. 36-43
  • Tidskriftsartikel (refereegranskat)abstract
    • The response of a matrix of 25 lead tungstate (PWO) scintillator detectors, operated at -25 degrees C, to photons in the range 13 MeV-64 MeV has been measured at the tagged-photon facility at MAX-lab, Lund. The tapered PWO crystals, each with a length of 200 mm and a cross-section of 24.4 x 24.4 mm(2) in the front end, read out by 19 mm photomultiplier tubes, were arranged in a 5 x 5 matrix. The response was measured for photons directed towards the centre of the central crystal as well as for photons directed towards the corner of the central crystal, where four crystals meet. The obtained energy resolution surpasses what has been published so far and is close to the limit given by Poisson statistics and escaped energy. For photons directed towards the centre(corner) of the central crystal the relative energy resolution, defined as (FWHM/2.35)/E-gamma, decreases from 7.3%(11.0%) at E-gamma = 13 MeV to 3.3%(3.6%) at E-gamma = 64 MeV. The reconstructed point of impact of a photon in this energy range is determined with an uncertainty (one standard deviation) of 7.3 +/- 0.1 mm.
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19.
  • Margaryan, Ashot, et al. (författare)
  • Low-Pressure MWPC System for the detection of Alpha-Particles and Fission Fragments
  • 2010
  • Ingår i: Armenian Journal of Physics. - 1829-1171. ; 3:4, s. 282-291
  • 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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20.
  • Morrow, S A, et al. (författare)
  • 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
  • Ingår i: Physical Review C: covering nuclear physics. ; 73
  • 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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21.
  • Myers, L. S., et al. (författare)
  • Compton scattering from C-12 using tagged photons in the energy range 65-115 MeV
  • 2014
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Elastic scattering of photons from C-12 has been investigated using quasimonoenergetic tagged photons with energies in the range 65-115 MeV at laboratory angles of 60 degrees, 120 degrees, and 150 degrees. at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the C-12(gamma,gamma)C-12 cross section to the bound- nucleon polarizabilities.
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22.
  • Myers, L. S., et al. (författare)
  • Compton scattering from the deuteron below pion-production threshold
  • 2015
  • Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Differential cross sections for elastic scattering of photons from the deuteron have recently been measured at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. These first new measurements in more than a decade further constrain the isoscalar electromagnetic polarizabilities of the nucleon and provide the first-ever results above 100 MeV, where the sensitivity to the polarizabilities is increased. We add 23 points between 70 and 112 MeV, at angles 60 degrees, 120 degrees, and 150 degrees. Analysis of these data using a chiral effective field theory indicates that the cross sections are both self-consistent and consistent with previous measurements. Extracted values of alpha(s) = [12.1 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] x 10(-4) fm(3) and beta(s) = [2.4 +/- 0.8(stat) +/- 0.2(BSR) +/- 0.8(th)] x 10(-4) fm(3) are obtained from a fit to these 23 new data points. This paper presents in detail the experimental conditions and the data analysis used to extract the cross sections.
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23.
  • Myers, L S, et al. (författare)
  • Measurement of compton scattering from the deuteron and an improved extraction of the neutron electromagnetic polarizabilities.
  • 2014
  • Ingår i: Physical Review Letters. - 1079-7114. ; 113:26
  • Tidskriftsartikel (refereegranskat)abstract
    • The electromagnetic polarizabilities of the nucleon are fundamental properties that describe its response to external electric and magnetic fields. They can be extracted from Compton-scattering data-and have been, with good accuracy, in the case of the proton. In contradistinction, information for the neutron requires the use of Compton scattering from nuclear targets. Here, we report a new measurement of elastic photon scattering from deuterium using quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden. These first new data in more than a decade effectively double the world data set. Their energy range overlaps with previous experiments and extends it by 20 MeV to higher energies. An analysis using chiral effective field theory with dynamical Δ(1232) degrees of freedom shows the data are consistent with and within the world data set. After demonstrating that the fit is consistent with the Baldin sum rule, extracting values for the isoscalar nucleon polarizabilities, and combining them with a recent result for the proton, we obtain the neutron polarizabilities as α_{n}=[11.55±1.25(stat)±0.2(BSR)±0.8(th)]×10^{-4} fm^{3} and β_{n}=[3.65∓1.25(stat)±0.2(BSR)∓0.8(th)]×10^{-4} fm^{3}, with χ^{2}=45.2 for 44 degrees of freedom.
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24.
  • Myers, L. S., et al. (författare)
  • Monte Carlo simulation of the photon-tagger focal-plane electronics at the MAX IV laboratory
  • 2013
  • Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 729, s. 707-717
  • Tidskriftsartikel (refereegranskat)abstract
    • Rate-dependent effects in the electronics used to instrument the tagger focal plane at the MAX IV Laboratory have been investigated using the novel approach of Monte Carlo simulation. Results are compared to analytical calculations as well as experimental data for both specialized testing and production running to demonstrate a thorough understanding of the behavior of the detector system.(C) 2013 Elsevier By. All rights reserved.
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