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Journal Articles

Population and decay of a $$K^{pi}$$ = 8$$^{-}$$ two-quasineutron isomer in $$^{244}$$Pu

Hota, S.*; Tandel, S.*; Chowdhury, P.*; Ahmad, I.*; Carpenter, M. P.*; Chiara, C. J.*; Greene, J. P.*; Hoffman, C. R.*; Jackson, E. G.*; Janssens, R. V. F.*; et al.

Physical Review C, 94(2), p.021303_1 - 021303_5, 2016/08

 Times Cited Count:5 Percentile:46.59(Physics, Nuclear)

The decay of a $$K^{pi}$$ = 8$$^{-}$$ isomer in $$^{244}$$Pu and the collective band structure populating the isomer are studied using deep inelastic excitations with $$^{47}$$Ti and $$^{208}$$Pb beams, respectively. Precise measurements of $$M1/E2$$ branching ratios in the band confirm a clean 9/2$$^-$$[734]$$_{nu}$$$$otimes$$7/2$$^+$$[624]$$_{nu}$$ for the isomer, validating the systematics of K$$^{pi}$$ = 8$$^{-}$$ two-quasineutron isomers observed in even-$$Z$$, $$N$$ = 150 isotones. These isomers around the deformed shell gap at $$N$$ = 152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

Journal Articles

Search for a 2-quasiparticle high-$$K$$ isomer in $$^{256}$$Rf

Robinson, A. P.*; Khoo, T. L.*; Seweryniak, D.*; Ahmad, I.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; Chowdhury, P.*; Davids, C. N.*; Greene, J.*; et al.

Physical Review C, 83(6), p.064311_1 - 064311_7, 2011/06

 Times Cited Count:24 Percentile:16.78(Physics, Nuclear)

We have identified an isomer with a half-life of 17 $$mu$$s in $$^{256}$$Rf through a calorimetric conversion electron measurement tagged with implanted $$^{256}$$Rf nuclei using the fragment mass analyzer at Argonne National Laboratory. The low population yield for this isomer suggests that this isomer should not be a 2-quasiparticle high-$$K$$ isomer which is typically observed in the N = 152 isotones, but should be a 4-quasiparticle one. Possible reasons of the non-observation of a 2-quasiparticle isomer are this isomer decays by fission with a half-life similar to that of the ground state of $$^{256}$$Rf. Another possibility, that there is no 2-quasiparticle isomer at all, would imply an abrupt termination of axially symmetric deformed shape at Z=104.

Journal Articles

Bridging the nuclear structure gap between stable and super heavy nuclei

Seweryniak, D.*; Khoo, T. L.*; Ahmad, I.*; Kondev, F. G.*; Robinson, A.*; Tandel, S. K.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; Chowdhury, P.*; et al.

Nuclear Physics A, 834(1-4), p.357c - 361c, 2010/03

 Times Cited Count:7 Percentile:47.93(Physics, Nuclear)

Experimental data on single-particle energies in nuclei around Z=100 and N=152 play an important role to test validity of theoretical predictions for shell structure of superheavy nuclei. We found high-K two-quasiparticle isomers in $$^{252}$$No and $$^{254}$$No, and evaluated energies of proton single-particle orbitals around Z=100. We also found a new high-K three quasiparticle isomer in $$^{257}$$Rf. Energies of neutron single-particle orbitals were also evaluated from experimental data of the $$alpha$$ decay of $$^{257}$$Rf. Comparisons between the present experimental data and various theoretical calculations for the proton single-particle orbitals indicate that the calculation by using the Woods-Saxon potential gives the best agreement with the data.

Journal Articles

Spectroscopy of $$^{257}$$Rf

Qian, J.*; Heinz, A.*; Khoo, T. L.*; Janssens, R. V. F.*; Peterson, D.*; Seweryniak, D.*; Ahmad, I.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; et al.

Physical Review C, 79(6), p.064319_1 - 064319_13, 2009/06

 Times Cited Count:27 Percentile:15.33(Physics, Nuclear)

$$alpha$$-, $$gamma$$-, and conversion electron spectroscopy experiments for $$^{257}$$Rf have been performed using Fragment Mass Analyzer at Argonne National Laboratory. A new isomer with a half-life of 160 $$mu$$s has been discovered in $$^{257}$$Rf, and it is interpreted as a three-quasiparticle high-$$K$$ isomer. Neutron configurations of one-quasiparticle states in $$^{253}$$No, the $$alpha$$-decay daughter of $$^{257}$$Rf, have been assigned on the basis of $$alpha$$-decay hindrance factors. Excitation energies of the 1/2$$^{+}$$[620] states in $$N$$=151 isotones indicate that the deformed shell gap at $$N$$=152 increases with the atomic number.

Journal Articles

$$K^{pi}=8^{-}$$ isomers and $$K^{pi}=2^{-}$$ octupole vibrations in $$N=150$$ shell-stabilized isotones

Robinson, A. P.*; Khoo, T. L.*; Ahmad, I.*; Tandel, S. K.*; Kondev, F. G.*; Nakatsukasa, Takashi*; Seweryniak, D.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; et al.

Physical Review C, 78(3), p.034308_1 - 034308_6, 2008/09

 Times Cited Count:42 Percentile:9.25(Physics, Nuclear)

Isomers have been identified in $$^{246}$$Cm and $$^{252}$$No with quantum number $$K^{pi}=8^{-}$$, which decay through $$K^{pi}=2^{-}$$ rotational bands built on octupole vibrational states. For $$N=150$$ isotones with atomic number $$Z=94$$$$sim$$102, the $$K^{pi}=8^{-}$$ and 2$$^{-}$$ states have remarkably stable energies, indicating neutron excitations. An exception is a singular minimum in the 2$$^{-}$$ energy at $$^{246}$$Cm, due to the additional role of proton configurations.

Journal Articles

Research and development of imaging bolometers

Peterson, B. J.*; Konoshima, Shigeru; Kostryukov, A. Y.*; Seo, D. C.*; Liu, Y.*; Miroshnikov, I. V.*; Ashikawa, Naoko*; Parchamy, H.*; Kawashima, Hisato; Iwama, Naofumi*; et al.

Plasma and Fusion Research (Internet), 2, p.S1018_1 - S1018_4, 2007/11

An overview of the research and development of imaging bolometers giving a perspective on the applicability of this diagnostic to a fusion reactor is presented. Traditionally the total power lost from a high temperature has been measured using one dimensional arrays of resistive bolometers. The large number of signal wires associated with these resistive bolometers poses hazards not only at the vacuum interface, but also in the loss of electrical contacts that has been observed in the presence of fusion reactor levels of neutron flux. Infrared imaging video bolometers (IRVB), on the other hand, use the infrared radiation from the absorbing metal foil to transfer the signal through the vacuum interface and out from behind a neutron shield. The IRVB can provide hundreds of channels of bolometric signal in an image of the plasma radiation. Recently a prototype IRVB has been deployed on the JT-60U tokamak which demonstrates the ability of this diagnostic to operate in a reactor environment.

Journal Articles

Spatial variation of the foil parameters from in situ calibration of the JT-60U imaging bolometer foil

Araghy, H. P.*; Peterson, B. J.*; Hayashi, Hiromi*; Konoshima, Shigeru; Ashikawa, Naoko*; Seo, D. C.*; JT-60U Team

Plasma and Fusion Research (Internet), 2, p.S1116_1 - S1116_4, 2007/11

We obtain the local foil properties of the JT-60U imaging bolometer foil (a single graphite-coated gold foil with an effective area of 9 $$times$$ 7 cm$$^{2}$$ and a nominal thickness of 2.5 microns) such as the thermal diffusivity and the product of the thermal conductivity and the thickness of the foil by the foil calibration. Calibration of the foil was made in situ using a He-Ne laser ($$sim$$27 mW) as a known radiation source to heat the foil. The thermal images of the foil are provided by an IR camera (micro-bolometer type). The parameters are determined by finite element modeling of the foil temperature and comparing the solution to the experimental results. In this work we apply this calibration technique to investigate the spatial variation of the foil parameters. Significant variation in the local temperature rise of the foil due to local heating by the laser beam indicates a spatial variation of the foil parameters. This variation is possibly due to nonuniformity in the carbon coating and/or the thickness of the foil. In a separate work, the spatial calibration data will be used to produce the bolometer intensity data to be utilized in the tomographic analyses.

Journal Articles

Observation of divertor and core radiation in JT-60U by means of bolometric imaging

Peterson, B. J.*; Konoshima, Shigeru; Parchamy, H.*; Kaneko, Masashi*; Omori, Toshimichi*; Seo, D. C.*; Ashikawa, Naoko*; Sukegawa, Atsuhiko; JT-60 Team

Journal of Nuclear Materials, 363-365, p.412 - 415, 2007/06

 Times Cited Count:11 Percentile:34.46(Materials Science, Multidisciplinary)

Diagnosis of the radiation from both the divertor and core plasma regions is a key issue for the study of impurities resulting from plasma-surface interaction in existing magnetic plasma confinement experiments and future fusion reactors. An infrared imaging video bolometer has been designed, fabricated and installed on the JT-60U tokamak. This diagnostic utilizes an IR camera to image the temperature change of a thin foil which is exposed to plasma radiation through an aperture resulting in an image of the incident plasma radiation absorbed by the foil. In the 2004-2005 experimental campaign intitial data was taken which was limited to 8-bit analog video data from ohmic and hydrogen neutral beam discharges due to inadequate shielding. The semitangential, wide-angle view of the plasma covers the entire poloidal cross-section and the divertor extending over 90 degrees toroidally. This preliminary data showed a strong radiation zone from the divertor that moved up into the core plasma as the discharge terminated in agreement with the data from the resistive bolometer arrays. For the current campaign we have upgraded the system by improving the shielding against neutrons, $$gamma$$ and magnetic field. This has enabled operation of the camera during high magnetic field and some high power deuterium neutral beam discharges. We also improved the triggering and data transmission system to acquire 14-bit digital data. This will allow processing of the IR camera data to produce images of the radiation brightness at the foil which can be viewed as a movie with a frame rate of 30 fps. This data is used to study the toroidal uniformity of the radiation from the divertor in JT-60U.

Journal Articles

Progress in the ITER physics basis, 7; Diagnostics

Donn$'e$, A. J. H.*; Costley, A. E.*; Barnsley, R.*; Bindslev, H.*; Boivin, R.*; Conway, G.*; Fisher, R.*; Giannella, R.*; Hartfuss, H.*; von Hellermann, M. G.*; et al.

Nuclear Fusion, 47(6), p.S337 - S384, 2007/06

 Times Cited Count:275 Percentile:21.05(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Detailed ${it in situ}$ laser calibration of the infrared imaging video bolometer for the JT-60U tokamak

Parchamy, H.*; Peterson, B. J.*; Konoshima, Shigeru; Hayashi, Hiromi*; Seo, D. C.*; Ashikawa, Naoko*; JT-60U Team

Review of Scientific Instruments, 77(10), p.10E515_1 - 10E515_4, 2006/10

 Times Cited Count:13 Percentile:41.57(Instruments & Instrumentation)

no abstracts in English

Oral presentation

Imaging bolometers for steady state fusion experiments

Peterson, B. J.*; Seo, D. C.*; Konoshima, Shigeru; Kawashima, Hisato; Ashikawa, Naoko*; Parchamy, H.*; Liu, Y.*

no journal, , 

Resistive bolometers have problems with signal drift due to the uncompensated change in the background temperature of the detector. The electrical connections are susceptible to large changes in temperature. These characteristics render them ill suited for the application to steady-state fusion experiments. InfraRed imaging Video Bolometers (IRVB), on the other hand, are suited to steady state operation. The radiation is absorbed by the front surface of a thin foil and measured with an infrared camera. Temperature difference is taken with respect to the surrounding frame and no drift in the signal occurs. The materials are all metals and there are no electrical connections. IRVBs have been operated in LHD and JT-60U and are under design for KSTAR and planned for JT-60SA. Foil calibration and tomography techniques have been developed to provide poloidal profiles of the radiation emissivity.

Oral presentation

Design of an imaging bolometer upgrade for JT-60U

Peterson, B. J.*; Konoshima, Shigeru; Kostryukov, A. Y.*; Kawashima, Hisato; Seo, D. C.*; Miroshnikov, I. V.*; Ashikawa, Naoko*; Parchamy, H.*; Liu, Y.*; JT-60 Team

no journal, , 

Oral presentation

Comparison of the Au and Ta foil parameters from laser calibration of imaging bolometer foils

Parchamy, H.*; Peterson, B. J.*; Hayashi, Hiromi*; Konoshima, Shigeru; Ashikawa, Naoko*; Seo, D. C.*; Kawashima, Hisato; JT-60 Team

no journal, , 

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