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M. Karlsson, J. -O. Adler,
L. E. M. Andersson,
V. Avdeichikov,
B. L. Berman,
M. J. Boland,
W. J. Briscoe,
J. Brudvik,
J. R. Calarco,
G. Feldman, [......],
A. A. Kotov,
P. Lilja,
M. Lundin,
B. Nilsson,
D. Nilsson,
G. V. O’Rielly,
G. E. Petrov,
B. Schröder,
I. I. Strakovsky,
L. A. Vaishnene
[show abstract]
[hide abstract]
ABSTRACT: The two-body photodisintegration of 3He 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° 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.
Phys. Rev. C. 10/2009; 80(4).
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M Karlsson, J. -O. Adler,
L. E. M. Andersson,
V Avdeichikov,
B L Berman,
M.J. Boland,
W. J. Briscoe,
J. Brudvik,
J R Calarco,
G Feldman, [......],
A. A. Kotov,
P. Lilja,
M. Lundin,
B. Nilsson,
D. Nilsson,
G V O'Rielly,
G. E. Petrov,
B. Schroder,
I. I. Strakovsky,
L. A. Vaishnene
[show abstract]
[hide abstract]
ABSTRACT: The two-body photodisintegration of 3He 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 over-determined 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 90deg 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 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. Comment: 12 pages, 13 figures; further Referee comments addressed
03/2009;
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D Nilsson, J-O Adler,
B-E Andersson,
K I Blomqvist,
L Isaksson,
A Sandell,
B Schröder,
K Ziakas,
L van Hoorebeke,
D Rykbosch,
R van de Vyver
[show abstract]
[hide abstract]
ABSTRACT: The tagged photon technique has been used to measure the excitation energy spectra resulting from the (γ, p) reaction in 6Li and 12C at 90 degrees for incident photon energies around 61 and 77 MeV. Strong evidence is found for the quasideuteron absorption mechanism, not only in the high excitation energy regions, but also in bound states. Furthermore, for the 12C(γ, p) reaction the photon seems to be absorbed on pn-pairs in both T = 0 and T = 1 states.
Physica Scripta 08/2006; 49(4):397. · 1.20 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Relative populations of states in 11B following the 12C(γ,p)11B reaction have been measured with high resolution using a 70% HpGe γ detector to observe decay γ 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 γ-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 Δ currents, under the assumption that the photons are mainly absorbed on exchanged pions.
Phys. Rev. C. 04/2006; 73(4).
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A Zanini,
E Durisi,
F Fasolo,
C Ongaro,
L Visca,
U Nastasi,
K W Burn,
G Scielzo, J O Adler,
J R M Annand,
G Rosner
[show abstract]
[hide abstract]
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.
Physics in Medicine and Biology 03/2004; 49(4):571-82. · 2.83 Impact Factor
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I Akkurt, J O Adler,
J R M Annand,
F Fasolo,
K Hansen,
L Isaksson,
M Karlsson,
P Lilja,
M Lundin,
B Nilsson,
C Ongaro,
A Reiter,
G Rosner,
A Sandell,
B Schröder,
A Zanini
[show abstract]
[hide abstract]
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 natW, using tagged photons at the MAX-Lab photonuclear facility in Sweden. This work presents neutron yields for natW(gamma, n) and compares these with the predictions of the Monte Carlo code MCNP-GN, developed specifically to simulate photoneutron production at medical accelerators.
Physics in Medicine and Biology 11/2003; 48(20):3345-52. · 2.83 Impact Factor
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M Lundin, J-O Adler,
M Boland,
K Fissum,
T Glebe,
K Hansen,
L Isaksson,
O Kaltschmidt,
M Karlsson,
K Kossert, [......],
B Lindner,
A I L'vov,
B Nilsson,
D E Oner,
C Poech,
S Proff,
A Sandell,
B Schröder,
M Schumacher,
D A Sims
[show abstract]
[hide abstract]
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 45 degrees, 125 degrees, and 135 degrees. 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.
Physical Review Letters 06/2003; 90(19):192501. · 7.37 Impact Factor
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M.J. Boland,
M. A. Garbu tt,
R.P. Rassool,
M N Thompson,
A. J. Bennett,
J. W. Jury, J. -O. Adler,
B. Schroeder,
D. Nilsson,
K Hansen,
M Karlsson,
M. Lundin,
I. J. D. MacGregor
[show abstract]
[hide abstract]
ABSTRACT: A broad excited state was observed in 6-He with energy E_x = 5 +/- 1 MeV and width Gamma = 3 +/- 1 MeV, following the reaction Li-7(gamma,p)He-6. The state is consistent with a number of broad resonances predicted by recent cluster model calculations. The well-established reaction mechanism, combined with a simple and transparent analysis procedure confers considerable validity to this observation. Comment: 3 pages of LaTeX, 3 figures in PostScript, approved for publication in Phys. Rev. C, August, 2001
06/2001;
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D. Branford,
A. W. Rauf,
J. Lác, J. O. Adler,
T. Davinson,
D. G. Ireland,
C. W. de Jager,
M. Liang,
W. J. Kasdorp,
L. Lapikás,
B. Nilsson,
H. Ruijter,
D. Ryckbosch,
A. Sandell,
B. Schröder,
A. C. Shotter,
G. van der Steenhoven,
R. Van de Vyver,
P. J. Woods
[show abstract]
[hide abstract]
ABSTRACT: Cross sections have been measured for the 209Bi(e,e′p)208Pb and 209Bi(γ,p)208Pb reactions using electrons at Ee=293 and 412 MeV, and tagged photons at mean Eγ∼43.7 and ∼52.0 MeV, respectively. The 209Bi(e,e′p)208Pb results are compared to complete distorted wave impulse approximation calculations, from which it is deduced that a model of 209Bi based on a 1h9/2 proton orbiting an inert 208Pb core has a high degree of validity. The interpretation of the 209Bi(γ,p)208Pb results makes use of the (e,e′p) results to constrain the calculation of the direct knockout contribution. Using this approach, a comparison of the 209Bi(γ,p)208Pb data to various calculations with and without meson exchange contributions shows that the enhancement of the (γ,p) cross section due to meson exchange is small. This is in contrast to results obtained for light nuclei, but in agreement with results for heavier nuclei.
Phys. Rev. C. 12/2000; 63(1).
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S. Proff,
C. Pöch,
T. Glebe, J. -O. Adler,
K. Fissum,
K Hansen,
M. -Th. Hütt,
O. Kaltschmidt,
M. Lundin,
B. Nilsson,
B Schröder,
M Schumacher,
D. Sims,
F. Smend,
F. Wissmann
[show abstract]
[hide abstract]
ABSTRACT: Differential cross sections for elastic scattering of photons have been measured for $^{40}$Ca at energies of 58 and 74 MeV and for $^{16}$O and $^4$He at 61 MeV, in the angular range from 45$^o$ to 150$^o$. Evidence is obtained that there are no significant in-medium modifications of the electromagnetic polarizabilities except for those originating from meson exchange currents. Comment: 20 pages including 5 Figures
01/1999;
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D. Nilsson, J. -O. Adler,
B. -E. Andersson,
K. I. Blomqvist,
L. Isaksson,
A. Sandell,
B. Schröder,
K. Ziakas,
L. Van Hoorebeke,
D. Ryckbosch,
R. Van de Vyver
[show abstract]
[hide abstract]
ABSTRACT: The reaction6Li (, d) with E around 60 MeV has been investigated with monoenergetic photons using a Si-Ge E-E telescope, allowing accurate identification of deuterons with good energy resolution. A strict obedience of the isospin selection rule for E1 absorption, i.e. T=1, is observed for the ground state transition.
Zeitschrift für Physik A Hadrons and Nuclei 05/1990; 335(2):239-240.
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[show abstract]
[hide abstract]
ABSTRACT: The energy and angular distributions ofp, d, t,3He and4He from the three targets Cu, Ag and Au were measured at five different angles for bremsstrahlung with peak energy 500MeV. The measurements were made using a telescope consisting of four surface-barrier detectors. The experimental data are compared with cascade-evaporation calculations. For the4He-distributions the calculations were extended to include the contribution from knock-out of surface alphas by the cascade nucleons. The comparison shows that the main contribution comes from evaporation but that there is a direct component of the order of 10%.
Zeitschrift für Physik A Hadrons and Nuclei 02/1980; 295(1):65-72.
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B Nilsson, J.-O Adler,
B.-E Andersson,
J R M Annand,
I Akkurt,
M J Boland,
G I Crawford,
K G Fissum,
K Hansen,
P D Harty, [......],
L Isaksson,
M Karlsson,
M Lundin,
J C Mcgeorge,
G J Miller,
H Ruijter,
A Sandell,
B Schröder,
D A Sims,
D Watts
[show abstract]
[hide abstract]
ABSTRACT: A comprehensive set of 4 He(γ, n) absolute cross-section measurements has been performed at MAX-lab in Lund, Sweden. Tagged photons from 23 < Eγ < 70 MeV were directed toward a liquid 4 He target, and neutrons were identified using pulse-shape discrimination and the time-of-flight technique in two liquid-scintillator detector arrays. Seven-point angular distributions have been measured for fourteen photon energies. The results have been subjected to complementary Transition-coefficient and Legendre-coefficient analyses. The results are also compared to experi-mental data measured at comparable photon energies as well as Recoil-Corrected Continuum Shell Model, Resonating Group Method, and Effective Interaction Hyperspherical-Harmonic Expansion calculations. For photon energies below 29 MeV, the angle-integrated data are significantly larger than the values recommended by Calarco, Berman, and Donnelly in 1983.
01/2002; 20.
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E.C. Aschenauer,
C. Van den Abeele, J.-O. Adler,
B.-E. Andersson,
L.J. de Bever,
I. Bobeldijk,
D. Branford,
S.A. Bulychjov,
T. Davinson,
K. Hansen, [......],
H. Ruijter,
D. Ryckbosch,
A. Sandell,
A.C. Shotter,
B. Schröder,
V. Van der Sluys,
G. van der Steenhoven,
P. Svensson,
M.A. van Uden,
R.E. Van de Vyver
[show abstract]
[hide abstract]
ABSTRACT: Cross sections have been measured for the reactions 208Pb(γ,p) and 12C(γ,p) leading to the low-lying and continuum states in 207Tl and 11B using a high energy-resolution tagged photon beam of 41 to 57 MeV. The data are compared with results obtained with the (e,e′p) reaction in the same recoil-momentum range and with various theoretical calculations. A comparison of the (e,e′p) and (γ,p) data in terms of a reduced cross section versus momentum does not show a systematic overlap of the (e,e′p) and (γ,p) results, i.e. no scaling is observed. Distorted-wave impulse-approximation (DWIA) calculations, of which the input is constrained by the (e,e′p) data, and random-phase approximation calculations (RPA) underestimate the 12C(γ,p) data by typically a factor five depending on angle and missing energy. For 208Pb the difference between the calculations and the data for the low-lying states is much less, but an increasing discrepancy between the data and the calculations is found in the continuum. The inclusion of meson-exchange currents (MEC) brings the calculations for both nuclei on average closer to the data, but MEC effects are considerably less important for 208Pb as compared to 12C. Finally, a remarkable similarity is observed between the continuum response of the (γ,p) and (e,e′p) reactions on 208Pb despite the difference in the electromagnetic couplings involved.
Nuclear Physics A. 615(1):33-51.
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L. J. de Bever, J.-O. Adler,
B.-E. Andersson,
H. P. Blok,
J. Blouw,
I. Bobeldijk,
D. Branford,
S. Bulychev,
A. Cichocki,
T. Davinson, [......],
A. C. Shotter,
G. van der Steenhoven,
K. Takahisa,
J. Takamatsu,
H. de Vries,
K. Wang,
P. K. A. de Witt Huberts,
P. J. Woods,
M. Yosoi,
K. Ziakas
Nuclear Physics B - Proceedings Supplements 34:383-384. · 0.88 Impact Factor
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K. Hansen, J.-O. Adler,
K. I. Blomqvist,
D. Nilsson,
A. Sandell,
B. Schrøder,
W. R. Dodge,
Jr. J. W. Lightbody,
J. S. O’Connell,
J. R. Calarco,
J. P. Connelly,
F. W. Hersman,
W. Kim,
M. Leuschner
[show abstract]
[hide abstract]
ABSTRACT: The coincident electrofission (e,e’f) cross sections of 233,238U were measured in the excitation range 150–550 MeV. The probability of fission was found to be near unity in the delta resonance region (250–550 MeV), but less than unity in the quasifree scattering region (150–250 MeV). The data are analyzed with a model based on the quasifree and delta reaction mechanisms. An excitation energy of 25 MeV is found for the residual nucleus in the quasifree region and over 40 MeV in the delta region.
Phys. Rev. C. 41(4).
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D. A. Sims,
G. J. O’Keefe,
R. P. Rassool,
A. Kuzin,
M. N. Thompson, J-O. Adler,
B-E. Andersson,
K. G. Fissum,
K. Hansen,
L. Isaksson,
B. Nilsson,
H. Ruijter,
A. Sandell,
B. Schröder,
J. R. M. Annand,
G. I. Crawford,
P. D. Harty,
J. C. McGeorge,
G. J. Miller
[show abstract]
[hide abstract]
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.
Phys. Rev. C. 55(3).
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L. J. de Bever,
D. Branford, J-O. Adler,
B-E. Andersson,
I. Bobeldijk,
T. Davinson,
R. S. Hicks,
D. G. Ireland,
K. Livingston,
R. L. J. van der Meer, [......],
L. Isaksson,
R. D. Page,
G. A. Peterson,
J. Rahighi,
H. Ruijter,
B. Schrøder,
G. van der Steenhoven,
P. J. Woods,
K. Wang,
A. C. Shotter
[show abstract]
[hide abstract]
ABSTRACT: The reaction 10B(γ,p) has been studied using tagged photons of mean energies Eγ=57.6 and 72.9 MeV. Angular distributions and derived single-particle momentum distributions for protons leading to the ground state of 9Be and higher excited states are compared to various calculations made using model parameters constrained by 10B(e,e′p)9Be and 9Be(p,p′)9Be measurements. The effects of varying final-state interactions (including channel couplings) and meson exchange currents are considered. A sizable discrepancy between direct-knockout calculations and the experimental results is observed. If meson exchange currents are included in an approximate fashion, a good description of the 10B(γ,p0)9Be data is found.
Phys. Rev. C. 58(2).
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M.J. Boland,
M.A. Garbutt,
R.P. Rassool,
M N Thompson,
A. J. Bennett,
J. W. Jury, J. -O. Adler,
B. Schroder,
D. Nilsson,
K Hansen,
M Karlsson,
M. Lundin,
I. J. D. MacGregor
[show abstract]
[hide abstract]
ABSTRACT: A broad excited state was observed in <sup>6</sup>He with energy E-x = 5 +/- 1 MeV and width Gamma = 3 +/- 1 MeV, following the reaction <sup>7</sup>Li(gamma ,p)<sup>6</sup>He. The state is consistent with a number of broad resonances predicted by recent cluster model calculations. The well-established reaction mechanism, combined with a simple and transparent analysis procedure confers considerable validity to this observation.
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D Branford,
A.W. Rauf,
J. Lac, J. -O. Adler,
T. Davinson,
D G Ireland,
C W de Jager,
M Liang,
W. J. Kasdorp,
L. Lapikas,
B. Nilsson,
H Ruijter,
D. Ryckbosch,
A Sandell,
B. Schroder,
A.C. Shotter,
G. van der Steenhoven,
R. Van de Vyver,
P. J. Woods
[show abstract]
[hide abstract]
ABSTRACT: Cross sections have been measured for the /sup 209/Bi(e,e'p)/sup 208/Pb and /sup 209/Bi( gamma ,p)/sup 208/Pb reactions using electrons at E/sub e/=293 and 412 MeV, and tagged photons at mean E/sub gamma /~43.7 and ~52.0 MeV, respectively. The /sup 209/Bi(e,e'p)/sup 208/Pb results are compared to complete distorted wave impulse approximation calculations, from which it is deduced that a model of /sup 209/Bi based on a 1h/sub 9/2/ proton orbiting an inert /sup 208/Pb core has a high degree of validity. The interpretation of the /sup 209/Bi( gamma ,p)/sup 208/Pb results makes use of the (e,e'p) results to constrain the calculation of the direct knockout contribution. Using this approach, a comparison of the /sup 209/Bi( gamma ,p)/sup 208/Pb data to various calculations with and without meson exchange contributions shows that the enhancement of the ( gamma ,p) cross section due to meson exchange is small. This is in contrast to results obtained for light nuclei, but in agreement with results for heavier nuclei.
