| 1. |
- Stefanescu, I., et al.
(författare)
-
Coulomb Excitation of 68,70Cu: First Use of Postaccelerated Isomeric Beams
- 2007
-
Ingår i: Physical Review Letters. ; 98
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the first low-energy Coulomb excitation measurements with radioactive Ipi=6- beams of odd-odd nuclei 68,70Cu. The beams were produced at ISOLDE, CERN and were post-accelerated by REX-ISOLDE to 2.83 MeV/nucleon. gamma rays were detected with the MINIBALL spectrometer. The 6- beam was used to study the multiplet of states (3-, 4-, 5-, 6-) arising from the pi2p3/2nu1g9/2 configuration. The 4- state of the multiplet was populated via Coulomb excitation and the B(E2;6--->4-) value was determined in both nuclei. The results obtained illustrate the fragile stability of the Z=28 shell and N=40 subshell closures. A comparison with large-scale shell-model calculations using the 56Ni core shows the importance of the proton excitations across the Z=28 shell gap to the understanding of the nuclear structure in the neutron-rich nuclei with N[approximate]40.
|
|
| 2. |
- Diriken, J., et al.
(författare)
-
Coulomb excitation of Ga-73
- 2010
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 82:6
-
Tidskriftsartikel (refereegranskat)abstract
- The B(E2; I-i -> I-f) values for transitions in Ga-71(31)40 and Ga-73(31)42 were deduced from a Coulomb excitation experiment at the safe energy of 2.95 MeV/nucleon using post-accelerated beams of Ga-71,Ga-73 at the REX-ISOLDE on-line isotope mass separator facility. The emitted gamma rays were detected by the MINIBALL gamma-detector array, and B(E2; I-i -> I-f) values were obtained from the yields normalized to the known strength of the 2(+) -> 0(+) transition in the Sn-120 target. The comparison of these new results with the data of less neutron-rich gallium isotopes shows a shift of the E2 collectivity toward lower excitation energy when adding neutrons beyond N = 40. This supports conclusions from previous studies of the gallium isotopes, which indicated a structural change in this isotopic chain between N = 40 and 42. Combined with recent measurements from collinear laser spectroscopy showing a 1/2(-) spin and parity for the ground state, the extracted results revealed evidence for a 1/2(-), 3/2(-) doublet near the ground state in Ga-73(31)42 differing by at most 0.8 keV in energy.
|
|
| 3. |
- Georgali, E., et al.
(författare)
-
Experimental study of the 165Ho(n, 2n) reaction : Cross section measurements for the population of the 164Ho ground state and isomeric state from the threshold up to 20 MeV
- 2020
-
Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 102:3
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work the 165Ho(n,2n) reaction was studied experimentally and theoretically for the population of the ground state (Jπ=1+) of the 164Ho product nucleus, as well as for the population of its isomeric state (Eex=139.8 keV, Jπ=6−). The cross sections of both the ground and isomeric state channels were measured at energies near the reaction threshold (Eth=8.04 MeV), at 10.1, 10.4, and 10.7 MeV, as well as at energies higher than 17 MeV, at 17.1, 18.1, 19.0, and 19.6 MeV. The adopted method was the activation technique relative to the 197Au(n,2n) 196Au and 27Al(n,α)24Na reference reactions. The quasi-monoenergetic neutron beams for the near threshold energies were produced via the 2H(d,n)3He reaction, while for the neutron beams above 17 MeV the 3H(d,n)4He reaction was utilized. In both cases the deuteron beams were delivered by the 5.5 MV Tandem Van de Graaff accelerator of the Institute of Nuclear and Particle Physics at N.C.S.R. “Demokritos”. Additional to the experimental study, calculations were performed using the talys code (v. 1.9). The experimental data of the present work along with the previous measurements were compared with the talys results so as to investigate the reproduction of the experimental data for the different level density models of the code.
|
|
| 4. |
- Kalamara, A., et al.
(författare)
-
Determination of the Ir-193(n, 2n) reaction cross section and correction methodology for the Ir-191(n, gamma) contamination
- 2019
-
Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 55:10
-
Tidskriftsartikel (refereegranskat)abstract
- The cross section of the Ir-193(n, 2n)Ir-192 reaction has been determined by means of the activation technique, relative to the Al-27(n, alpha) and Au-197(n, 2n) reference reactions cross sections, at neutron beam energies ranging from 10 to 21 MeV. The quasi-monoenergetic neutron beams were produced at the 5.5 MV Tandem T11/25 Accelerator Laboratory of NCSR "Demokritos" via the H-2(d, n) and H-3(d, n) reactions. The induced gamma-ray activity of the irradiated target and reference foils was measured with high resolution HPGe detectors. In order to correct for the contribution of the Ir-191(n, gamma)Ir-192 reaction, which is open to low energy parasitic neutrons, a recently developed analysis method was implemented and it is presented in great detail. Furthermore, cross section theoretical calculations were carried out using the EMPIRE and TALYS codes over a wide energy range.
|
|
| 5. |
- Mayer, M., et al.
(författare)
-
Ion beam analysis of fusion plasma-facing materials and components : Facilities and research challenges
- 2020
-
Ingår i: Nuclear Fusion. - : Institute of Physics Publishing. - 0029-5515 .- 1741-4326. ; 60:2
-
Tidskriftsartikel (refereegranskat)abstract
- Following the IAEA Technical Meeting on 'Advanced Methodologies for the Analysis of Materials in Energy Applications Using Ion Beam Accelerators', this paper reviews the current status of ion beam analysis (IBA) techniques and some aspects of ion-induced radiation damage in materials for the field of materials relevant to fusion. Available facilities, apparatus development, future research options and challenges are presented and discussed. The analysis of beryllium and radioactivity-containing samples from future experiments in JET or ITER represents not only an analytical but also a technical challenge. A comprehensive list of the facilities, their current status, and analytical capabilities comes alongside detailed descriptions of the labs. A discussion of future issues of sample handling and the current status of facilities at JET complete the technical section. To prepare the international IBA community for these challenges, the IAEA technical meeting concludes the necessity for determining new nuclear reaction cross-sections and improving the inter-laboratory comparability by defining international standards and testing these via a round-robin test.
|
|
| 6. |
- Stefanescu, I, et al.
(författare)
-
Interplay between single-particle and collective effects in the odd-A Cu isotopes beyond N=40
- 2008
-
Ingår i: Physical Review Letters. - 1079-7114. ; 100:11
-
Tidskriftsartikel (refereegranskat)abstract
- Collective properties of the low-lying levels in the odd-A Cu67-73 were investigated by Coulomb excitation with radioactive beams. The beams were produced at ISOLDE and postaccelerated by REX-ISOLDE up to 2.99 MeV/u. In Cu-67,Cu-69, low-lying 1/2(-), 5/2(-), and 7/2(-) states were populated. In Cu-71,Cu-73, besides the known transitions deexciting the single-particle-like 5/2(-) and core-coupled 7/2(-) levels, gamma rays of 454 and 135 keV, respectively, were observed for the first time. Based on a reanalysis of beta-decay work and comparison with the systematics, a spin 1/2(-) is suggested for these excited states. Three B(E2) values were determined in each of the four isotopes. The results indicate a significant change in the structure of the odd-A Cu isotopes beyond N=40 where single-particle-like and collective levels are suggested to coexist at very low excitation energies.
|
|
| 7. |
- Georgali, E., et al.
(författare)
-
Cross-section measurements of the Dy-156(n, 2n)Dy-155 reaction at neutron energies higher than 17 MeV
- 2021
-
Ingår i: Physical Review C. - : American Physical Society. - 2469-9985 .- 2469-9993. ; 104:6
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work the cross section of the 156Dy (n, 2n) 155Dy reaction (Eth = 9.51 MeV) was measured at neutron beam energies above 17 MeV: 17.1, 18.1, and 19.0 MeV. The irradiations were performed at the 5.5-MV tandem accelerator of the Institute of Nuclear and Particle Physics at N.C.S.R. "Demokritos", where quasimonoenergetic neutron beams were produced via the 3H (d, n) 4He reaction. The cross-section measurements were performed by means of the activation technique relative to the 27Al (n, alpha) 24Na reference reaction. Within the present work the experimental study is framed by theoretical calculations performed via the TALYS code (version 1.95).
|
|
| 8. |
- Lagoyannis, A., et al.
(författare)
-
Surface composition and structure of divertor tiles following the JET tokamak operation with the ITER-like wall
- 2017
-
Ingår i: Nuclear Fusion. - : IOP PUBLISHING LTD. - 0029-5515 .- 1741-4326. ; 57:7
-
Tidskriftsartikel (refereegranskat)abstract
- Samples extracted from several divertor tiles following the 2011-2012 operation of JET with the ITER-Like wall were analyzed using ion beam analysis methods, x-ray fluorescence spectroscopy, scanning electron microscopy with energy dispersive spectroscopy analysis and x-ray diffraction. The emphasis was on the determination of light species and on material mixing including compound formation on the bottom and the outer divertor tiles. Deposition of deuterium, beryllium, carbon, nitrogen, oxygen, iron, chromium, nickel and molybdenum has been detected on all studied tiles. The thickest deposition, of around 4 mu m, was measured on the bottom of the outer divertor, whereas the other surfaces (inner bottom and vertical outer) the co-deposits were around 1 mu m. x-ray diffraction measurements have revealed the formation of the compound W2C on all specimens.
|
|
| 9. |
- Tsavalas, P., et al.
(författare)
-
Fuel retention and carbon deposition on beryllium marker tiles from JET tokamak main chamber limiters investigated by ion beam analysis
- 2022
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:12
-
Tidskriftsartikel (refereegranskat)abstract
- The JET tokamak with the ITER-like wall is operated with arrays of castellated beryllium (Be) limiters in the main chamber. In several locations Be marker tiles were installed for erosion-deposition studies. The castellation sides and the plasma-facing surfaces (PFSs) of Be marker tiles from three different locations of the JET main chamber, from the experimental campaigns 2011-12 (ILW-1) and 2013-14 (ILW-2), were analysed, employing H-2 and He-3 micro-beams in order to determine carbon
|
|
| 10. |
- Georgali, E., et al.
(författare)
-
Using GEANT4 Monte Carlo simulations to resolve low energy γ-ray spectra : The study of 164Hog+m decay using a broad energy HPGe detector
- 2021
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 985
-
Tidskriftsartikel (refereegranskat)abstract
- Within the present work a peak analysis and unfolding method for low energy γ-ray spectroscopy is presented. This method can be used to facilitate the determination of the peak integral of a photopeak, when Ge X-ray escape peaks contaminate the latter and in parallel the source activity and the emission rate of the recorded photons which produce the escape peaks are unknown. It is based on extensive Monte Carlo simulations of the spectra by taking the full advantage of power and accuracy provided by the GEANT4 simulation toolkit.
|
|
| 11. |
- Kokkoris, M., et al.
(författare)
-
Benchmarking the evaluated proton differential cross sections suitable for the EBS analysis of natSi and 16O
- 2017
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 405, s. 50-60
-
Tidskriftsartikel (refereegranskat)abstract
- The evaluated proton differential cross sections suitable for the Elastic Backscattering Spectroscopy (EBS) analysis of Si-nat and O-16, as obtained from SigmaCalc 2.0, have been benchmarked over a wide energy and angular range at two different accelerator laboratories, namely at N.C.S.R. 'Demokritos', Athens, Greece and at Ruder Boskovic Institute (RBI), Zagreb, Croatia, using a variety of high-purity thick targets of known stoichiometry. The results are presented in graphical and tabular forms, while the observed discrepancies, as well as, the limits in accuracy of the benchmarking procedure, along with target related effects, are thoroughly discussed and analysed. In the case of oxygen the agreement between simulated and experimental spectra was generally good, while for silicon serious discrepancies were observed above E-p,E-lab = 2.5 MeV, suggesting that a further tuning of the appropriate nuclear model parameters in the evaluated differential cross-section datasets is required.
|
|
| 12. |
- Maragkos, F., et al.
(författare)
-
Differential cross-section measurements and R-Matrix calculations for proton elastic scattering on natMg in the energy range Ep,lab=2.70-4.25 MeV, suitable for EBS
- 2023
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 536, s. 45-54
-
Tidskriftsartikel (refereegranskat)abstract
- In the current work the first coherent set of differential cross section values for the natMg(p,p0)natMg elastic scattering covering the Ep,lab = 2700-4250 keV energy range is presented for 6 backscattering detection angles (120 degrees, 130 degrees, 140 degrees, 150 degrees, 160 degrees and 170 degrees). R-Matrix calculations were implemented using the AZURE 2.0 code [1] in an attempt to reproduce the obtained experimental data, whilst taking into account the 24Mg(p,p1)24Mg reaction channel. Both results are suitable for EBS and other IBA applications and, furthermore, they form a basis for a future expansion of the current SigmaCalc [2] evaluation, once more experimental data become available. The measurements were performed in the 5.5 MV TN11 HV Tandem Accelerator and the high precision goniometer of N.C.S.R. 'Demokritos', Athens, Greece. The experimental and data analysis procedures are presented in detail, along with the process behind the implementation of the R-Matrix calculations.
|
|
| 13. |
- Paneta, Valentina, et al.
(författare)
-
Accurate accelerator energy calibration using selected resonances in proton elastic scattering and in (p,gamma) and (p,p'gamma) reactions
- 2017
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier. - 0168-583X .- 1872-9584. ; 406, s. 108-111
-
Tidskriftsartikel (refereegranskat)abstract
- The present work aims at contributing to the field of Ion Beam Analysis by providing a set of standard, high-accuracy nuclear resonance reaction data points to be used for accelerator energy calibration up to 4.6 MeV, more specifically with the use of the Al-27(p,gamma),C-13(p,gamma), C-12(p,p(0)) and S-32(p,p'gamma) resonant reactions, as a result of a comprehensive investigation in two different laboratories. The use of resonances at higher energies, namely up to 6 MeV, is also discussed. The measurements have been performed at two different electrostatic accelerators, namely at the 5.5 MV HV TN-11 of NCSR "Demokritos", Greece, and at the 5 MV 15SDH-2 Pelletron Tandem accelerator at Uppsala University in Uppsala, Sweden. Common points were used to normalize and validate the data. The possible use of the O-16(p,p(o)) resonance at 3.47 MeV is also discussed and analyzed. (C) 2017 Elsevier B.V. All rights reserved.
|
|
| 14. |
- Tsavalas, P., et al.
(författare)
-
Be ITER-like wall at the JET tokamak under plasma
- 2017
-
Ingår i: Physica Scripta. - : IOP PUBLISHING LTD. - 0031-8949 .- 1402-4896. ; T170
-
Tidskriftsartikel (refereegranskat)abstract
- The JET tokamak is operated with beryllium and tungsten plasma-facing components to prepare for the exploitation of ITER. To determine beryllium erosion and migration in JET a set of markers were installed. Specimens from different beryllium marker tiles of the main wall of the ITER-like wall (ILW) JET tokamak from the first and the second D-D campaign were analyzed with nuclear reaction analysis, x-ray fluorescence spectroscopy, scanning electron microscopy and x-ray diffraction (XRD). Emphasis was on the determination of carbon plasma impurities deposited on beryllium surfaces. The C-12(d, p(0))C-13 reaction was used to quantify carbon deposition and to determine depth profiles. Carbon quantities on the surface of the Be tiles are low, varying from (0.35 +/- 0.07) x 10(17) to (11.8 +/- 0.6) x 10(17) at cm(-2) in the deposition depth from 0.4 to 6.7 mu m, respectively. In the 0.4-0.5 mm wide grooves of castellation sides the carbon content is found up to (14.3 +/- 2.5) x 10(17) at cm(-2) while it is higher (up to (38 +/- 4) x 10(17) at cm(-2)) in wider gaps (0.8 mm) separating tile segments. Oxygen (O), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni) and tungsten (W) were detected in all samples exposed to plasma and the reference one but at lower quantities at the latter. In the central part of the Inner Wall Guard Limiter from the first ILW campaign and in the Outer Poloidal Limiter from the second ILW campaign the Ni interlayer has been completely eroded. XRD shows the formation of BeNi in most specimens.
|
|
