| 1. |
- Akkoyun, S., et al.
(author)
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AGATA - Advanced GAmma Tracking Array
- 2012
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In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 0167-5087 .- 1872-9576. ; 668, s. 26-58
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Journal article (peer-reviewed)abstract
- The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation γ-ray spectrometer. AGATA is based on the technique of γ-ray energy tracking in electrically segmented high-purity germanium crystals. This technique requires the accurate determination of the energy, time and position of every interaction as a γ ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of γ-ray tracking and AGATA is a result of many technical advances. These include the development of encapsulated highly segmented germanium detectors assembled in a triple cluster detector cryostat, an electronics system with fast digital sampling and a data acquisition system to process the data at a high rate. The full characterisation of the crystals was measured and compared with detector- response simulations. This enabled pulse-shape analysis algorithms, to extract energy, time and position, to be employed. In addition, tracking algorithms for event reconstruction were developed. The first phase of AGATA is now complete and operational in its first physics campaign. In the future AGATA will be moved between laboratories in Europe and operated in a series of campaigns to take advantage of the different beams and facilities available to maximise its science output. The paper reviews all the achievements made in the AGATA project including all the necessary infrastructure to operate and support the spectrometer. © 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Morris, B. M., et al.
(author)
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CHEOPS precision phase curve of the Super-Earth 55 Cancri e
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 653
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Journal article (peer-reviewed)abstract
- Context. 55 Cnc e is a transiting super-Earth (radius 1.88 R-circle plus and mass 8 M-circle plus) orbiting a G8V host star on a 17-h orbit. Spitzer observations of the planet's phase curve at 4.5 mu m revealed a time-varying occultation depth, and MOST optical observations are consistent with a time-varying phase curve amplitude and phase offset of maximum light. Both broadband and high-resolution spectroscopic analyses are consistent with either a high mean molecular weight atmosphere or no atmosphere for planet e. A long-term photometric monitoring campaign on an independent optical telescope is needed to probe the variability in this system. Aims. We seek to measure the phase variations of 55 Cnc e with a broadband optical filter with the 30 cm effective aperture space telescope CHEOPS and explore how the precision photometry narrows down the range of possible scenarios. Methods. We observed 55 Cnc for 1.6 orbital phases in March of 2020. We designed a phase curve detrending toolkit for CHEOPS photometry which allowed us to study the underlying flux variations in the 55 Cnc system. Results. We detected a phase variation with a full-amplitude of 72 +/- 7 ppm, but did not detect a significant secondary eclipse of the planet. The shape of the phase variation resembles that of a piecewise-Lambertian; however, the non-detection of the planetary secondary eclipse, and the large amplitude of the variations exclude reflection from the planetary surface as a possible origin of the observed phase variations. They are also likely incompatible with magnetospheric interactions between the star and planet, but may imply that circumplanetary or circumstellar material modulate the flux of the system. Conclusions. This year, further precision photometry of 55 Cnc from CHEOPS will measure variations in the phase curve amplitude and shape over time.
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| 3. |
- Lieder, R M, et al.
(author)
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Gamma-ray tracking arrays
- 2001
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In: PROGRESS IN PARTICLE AND NUCLEAR PHYSICS, VOL 46. ; , s. 399-407
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Conference paper (peer-reviewed)abstract
- The next generation of 4 pi arrays for high-precision gamma -ray spectroscopy will involve "gamma -ray tracking front-end on digital signal processing techniques, which allows to extract energy, timing and spatial information on the interactions of a gamma -ray in the Ge detector by pulse shape analysis of its signals. Utilizing the information on the positions of the interaction points and the energies released at each point the tracks of the gamma -rays in a Ge shell can be reconstructed in three dimensions.
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| 4. |
- Lieder, R. M., et al.
(author)
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From highly to superdeformed shapes : study of Gd-143
- 2000
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In: Nuclear Physics A. - 0375-9474 .- 1873-1554. ; 671:04-jan, s. 52-70
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Journal article (peer-reviewed)abstract
- A superdeformed band has been discovered in Gd-143 consisting Of 15 transitions. It does not show the band crossing observed in the neighbouring heavier Gd isotopes and it is degenerate with the superdeformed band in Eu-143. In contrast to other degenerate bands at superdeformed shape, the configurations of the bands are quite different here. They result from the exchange of a nu 6(4) with a pi[404]9/2 configuration. In addition, a collective band has been observed which adopts a well-deformed triaxial shape at high spins according to calculations. The transition from highly to superdeformed shapes proceeds via triaxial shapes.
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| 5. |
- Lieder, R. M., et al.
(author)
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Investigations of the level scheme of Gd-144 and lifetimes in the quadrupole bands
- 2004
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In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 21:1, s. 37-55
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Journal article (peer-reviewed)abstract
- For a level scheme investigation of Gd-144 an experiment with the gamma-spectrometer EUROBALL III has been carried out and lifetimes have been measured with the gamma-spectrometer GASP using the Doppler-shift attenuation method. The high-spin states have been populated in these experiments by means of the Mo-100(Ti-48,4n) reaction at 215 MeV and the Cd-114(S-36,6n) reaction at E = 182 MeV, respectively. The known quadrupole band has been modified and a new one has been established. Reduced E2 transition probabilities B(E2) were determined for seven members of these quadrupole bands. They show values between approximate to60 and 130 W.u. and this considerable enhancement gives evidence for a significant nuclear deformation. A (pih(11/2))(2) circle times (vh(11/2))(-2) configuration may be assigned to one of the quadrupole bands according to total Routhian surface calculations. The spin dependence of the B(E2) values has been explained by IBM calculations involving high-spin quasiparticle excitations.
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| 6. |
- Mason, P, et al.
(author)
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Octupole signatures in Ba-124,Ba-125
- 2005
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In: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 31:10, s. S1729-S1733
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Journal article (peer-reviewed)abstract
- The gamma decay of the nuclei Ba-121,Ba-125 has been investigated with the EUROBALL array, using the reaction Ni-64+Ni-64 at E-beam = 255 and 261 MeV. Six new E1 transitions have been found in the nucleus Ba-125, suggesting a significant role of octupole correlations in the origin of its parity doublets. The J(pi) = 3(-) level of the nucleus Ba-124 has been identified for the first time. Its excitation energy is in very good agreement with a prediction based on a microscopic model including octupole interactions.
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| 7. |
- Lieder, E O, et al.
(author)
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Investigation of lifetimes in quadrupole bands of Gd-142
- 2008
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In: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 35:2, s. 135-158
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Journal article (peer-reviewed)abstract
- For a level scheme investigation of Gd-142 an experiment with the gamma -spectrometer EUROBALLIII has been carried out and lifetimes have been measured with EUROBALL IV using the Doppler-shift attenuation method. The high-spin states have been populated in these experiments by means of the(99)Ru(Ti-48, 2p3n) reaction at a beam energy of 240MeV and the Sn-114(S-32, 2p2n) reaction at 160MeV, respectively. Reduced E2 transition probabilities B(E2) were determined for 15 members of four quadrupole bands. For the interpretation of the positive-parity even-spin quadrupole bands, calculations in the cranked Nilsson-Strutinsky as well as interacting boson models have been performed. From the former calculations it was concluded that the high-spin states of the (+ , 0)(1) band in Gd-142 represent a triaxial nucleus rotating around the longest principal axis.
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| 8. |
- Lieder, R. M., et al.
(author)
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Development of magnetic rotation in light Gd nuclei; study of Gd-142
- 2002
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In: European Physical Journal A. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 13:3, s. 297-305
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Journal article (peer-reviewed)abstract
- High-spin states in Gd-142 have been populated by means of the Ru-99(Ti-48, 2p3n) reaction at 2-10 MeV and investigated with the gamma-spectrometer EUROBALL III and the charged-particle detector array ISIS. The features of four dipole bands have been determined and compared with tilted-axis cranking model calculations indicating that they are magnetic rotational bands. A transition from regular to irregular bands has been found approaching N = 82 demonstrating that this is a general phenomenon in nuclei near a double-shell closure.
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| 9. |
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| 10. |
- Lieder, E. O., et al.
(author)
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DSAM Lifetime Studies for Gd-Nd nuclei with EUROBALL and AFRODITE
- 2008
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In: Frontiers in Nuclear Structure, Astrophysics, and Reactions, FINUSTAR 2007. - : AIP. - 1551-7616 .- 0094-243X. - 9780735405325 ; 1012, s. 383-385
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Conference paper (peer-reviewed)abstract
- Lifetimes of high-spin states have been measured for 142Gd and 134Nd with EU-ROBALL IV and AFRODITE, respectively, using DSAM. From calculations in the cranked Nilsson-Strutinsky model it was concluded that at the high-spin states of the (+,0)1 band, 142Gd represents a triaxial nucleus rotating around the longest principal axis.
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