Discovery and cross-section measurement of 58 new fission products in projectile-fission of 750 · A MeV 238U

Bernas, M.; Engelmann, Ch.; Armbruster, P.; Czájkowski, S.; Ameil, F.; Böckstiegel, C.; Dessagne, Ph.; Donzaud, C.; Geißel, H.; Heinz, A.; Janas, Z.; Kozhuharov, C.; Miehé, Ch.; Münzenberg, G.; Pfützner, M.; Schwab, W.; Stéphan, C.; Sümmerer, K.; Tassan‐Got, L.; Voss, B.

doi:10.1016/s0370-2693(97)01216-1

Cited by 155 publications

(65 citation statements)

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“…This was well demonstrated by experiments at GSI, in which more than a hundred new isotopes were identified in a single experiment. 6,7) The BigRIPS separator has been designed with large acceptances, to take advantage of the high production cross sections of neutron-rich isotopes from these reactions. The full angular acceptances of 80 mrad (horizontal) and 100 mrad (vertical), and the full momentum acceptance of 6% allows efficient RI beam production with in-flight fission, in which fission fragments are produced with large spreads in both angle and momentum.…”

Section: )mentioning

confidence: 99%

“…The estimates for 124 Pd, 125 Pd, and 126 Pd isotopes are 80, 7, and 0.7 nb, respectively, and are consistent with the experimental results at GSI for 124 Pd (32 nb). 7) In summary, we have performed the first experiment at the RIBF using the BigRIPS in-flight RI beam separator and a search for new neutron-rich isotopes was carried out using the in-flight fission of a 238 U beam at 345 MeV/nucleon. We observed the production of two new isotopes 125 Pd and 126 Pd, even though the uranium beam intensity was far from the goal for the RIBF and the total observation time was only about a day.…”

Section: )mentioning

confidence: 99%

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Identification of New Isotopes ¹²⁵Pd and ¹²⁶Pd Produced by In-Flight Fission of 345 MeV/nucleon ²³⁸U: First Results from the RIKEN RI Beam Factory

et al. 2008

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A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out in the commissioning experiment of the next-generation in-flight radioactive isotope beam separator BigRIPS at the RI Beam Factory at the RIKEN Nishina Center. Two neutron-rich palladium isotopes 125 Pd and 126 Pd were observed for the first time, which demonstrates the great potential of the RIKEN RI beam factory. 2) at the RIKEN Nishina Center that promises to advance the study of exotic nuclei to a great extent. The new superconducting in-flight RI beam separator BigRIPS is a major experimental device at the RIBF for RI beam production based on the in-flight separation technique and for research with exotic nuclei.3,4) Thanks to its large acceptances, not only projectile fragmentation of various heavy-ion beams but also in-flight fission of fissile beams 5) can be efficiently used as a production reaction in the BigRIPS separator. Figure 1 shows a schematic layout of the BigRIPS separator along with the IRC and SRC cyclotrons 1) and the ZeroDegree spectrometer.3) The cyclotrons at the RIBF can accelerate all heavy ions up to approximately 400 MeV/nucleon, including very heavy elements such as uranium, with the goal of reaching an intensity of 1 pmA (6 Â 10 12 particles/s). 1)In-flight fission of fissile beams, such as a 238 U beam, is known as an excellent mechanism for producing a wide range of neutron-rich exotic nuclei far from stability. This was well demonstrated by experiments at GSI, in which more than a hundred new isotopes were identified in a single experiment.6,7) The BigRIPS separator has been designed with large acceptances, to take advantage of the high production cross sections of neutron-rich isotopes from these reactions. The full angular acceptances of 80 mrad (horizontal) and 100 mrad (vertical), and the full momentum acceptance of 6% allows efficient RI beam production with in-flight fission, in which fission fragments are produced with large spreads in both angle and momentum. Due to its large acceptance, the BigRIPS separator has an approximately 50% efficiency for the collection of these fission fragments.Another important feature of the BigRIPS separator is its two-stage structure, which allows delivery of tagged RI beams, or use as a two-stage separator. In the tagging mode, which may also be called a separator-spectrometer mode, the first stage is used to produce and separate RI beams with a wedge energy degrader, while the second works as a spectrometer to analyze and identify those RI beams. The momentum resolution of the second stage has been designed to be high enough to identify RI beams without measuring their total kinetic energies, even though they are produced in several charge states in our energy domain. In the two-stage LETTERS Ã

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Section: )mentioning

confidence: 99%

Section: )mentioning

confidence: 99%

Identification of New Isotopes ¹²⁵Pd and ¹²⁶Pd Produced by In-Flight Fission of 345 MeV/nucleon ²³⁸U: First Results from the RIKEN RI Beam Factory

et al. 2008

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“…Nearly all the n-rich nuclides on the diagonals have been discovered except the last corner stone in the SHE-region. The diagonal connects between 78 Ni and 132 Sn n-rich nuclides, all observed [12], but not well investigated. The second diagonal between 132 Sn and 208 Pb connects known territory.…”

Section: The Interacting Boson Approximation (Iba) -A Guideline To Numentioning

confidence: 99%

A region of oblate nuclides centred at Z = 114 and of spherical nuclides centred at the magic nucleus - A possible scenario to understand the production of superheavy elements beyond copernicium

Armbruster

2011

EPJ Web of Conferences

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Abstract.The recent experiments at FLNR, Dubna, demonstrated that cross sections to produce SHEs by 48 Ca induced reactions on actinide targets increase beyond Z = 111, reach a maximum of 5 pb at Z = 114/115, and fall below the 1 pb-level at Z = 118. A scenario is proposed to understand the findings within the frame of former experimental results of heavy element production and theoretical predictions on the stability of the nuclides concerned. New ingredients introduced are 1) to shift the next proton shell beyond Pb from Z = 114 to Z = 122, 2) the isotopes of elements Z = 112 to Z = 118 are deformed and their nuclei have oblate shapes, and 3) the fission barriers around the next magic nucleus 306 122 184 are larger than the neutron separation energies and reach values in the range of 10 MeV. The ascent of the flat top at 306 122 184 is described by the proposed scenario, which likewise excludes to reach the doubly closed shell region at the top by today ′ s experimental methods in complete fusion reactions. Closed proton shell shifts away from Z = 11448 Ca-induced fusion reactions on heavy actinide targets have been investigated at the FLNR-Dubna. The discovery of many isotopes and evidence for new superheavy elements (SHEs) Z = 114 to 118 were reported since 2004 and presented in a review [1,2]. For more than 40 years the protonshell of SHEs has been positioned at Z = 114 [3,4]. The next neutron-shell stayed fixed at N = 184, as predicted by the early shell model [5], whereas recent calculations position the proton shell at Z = 120 or Z = 122 [6,7]. In 2008 [8] I presented an analysis of α-decay chains for pairs of even-even nuclei measured in the FLNR-experiments. These chains give access to Q α -values between the groundstates of the isotopes involved. The isospin-values (N − Z)/2 characterising the chains were 29 and 30 and cover the even elements between Z = 118 and Z = 112. They cross the proposed proton-shell Z = 114 at N = 172 and N = 174 away from the next neutron-shell at N = 184 by 12 and 10 neutrons. Q α -values in decay-chains decrease steadily descending the chain to smaller Z-values. Passing a shell a jump from higher Q α -values above the shell to lower values below the shell is well documented in nuclear data tables [9] for the main shells Z = 82, 50. The size of the jump crossing the magic proton-shell becomes smaller going away from the nearest doubly magic nucleus. We will examine by a comparison to the well-established Pbshell at equivalent distances in the neutron numbers, whether for a shell at Z = 114 a jump should still be observed at a distance of 12 or 10 neutrons. The point of comparison for the Pb-shell is N = 118. The Pb-shell crossed at N = 119 − 116 by the chains passing from Po via Pb to Hg manifests a jump of (1.21±0.02) MeV at the shell-crossing. a e-mail: Peter.Armbruster@gsi.deThe analysis presented in Fig. 1 demonstrates that the Pbshell is still clearly visible at 200 Pb, and a shell closure at Z = 114 should be manifested in the α-chains presented by FLNR. An analysis ...

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“…The boosting of the fission fragments induced by the inverse kinematics made it possible to fully identify in atomic, and mass number one of the final fission fragments using a high resolving power magnetic spectrometer [9], or identify in atomic number both fragments using large acceptance ionization chambers [10]. Moreover, fragmentation or spallation reactions produce fissioning systems with high excitation energy, moderate angular momentum, and small shape distortion, fulfilling the optimal conditions for the investigation of dissipative effects in fission [6,11].…”

Section: Introductionmentioning

confidence: 99%

New experimental approaches to investigate the fission dynamics

Benlliure¹,

Rodríguez-Sànchez²,

Álvarez‐Pol³

et al. 2016

AIP Conference Proceedings

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Abstract. The first ever achieved full identification of both fission fragments, in atomic and mass number, made it possible to define new observables sensitive to the fission dynamics along the fission path up to the scission point. Moreover, proton-induced fission of 208 Pb at high energies offers optimal conditions for the investigation of dissipative, and transient effects, because of the high-excitation energy of the fissioning nuclei, its low angular momentum, and limited shape distortion by the reaction. In this work we show that the charge distribution of the final fission fragments can constrain the ground-to-saddle dynamics while the mass distribution is sensitive to the dynamics until the scission point.

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Discovery and cross-section measurement of 58 new fission products in projectile-fission of 750 · A MeV 238U

Cited by 155 publications

References 21 publications

Identification of New Isotopes ¹²⁵Pd and ¹²⁶Pd Produced by In-Flight Fission of 345 MeV/nucleon ²³⁸U: First Results from the RIKEN RI Beam Factory

Identification of New Isotopes ¹²⁵Pd and ¹²⁶Pd Produced by In-Flight Fission of 345 MeV/nucleon ²³⁸U: First Results from the RIKEN RI Beam Factory

A region of oblate nuclides centred at Z = 114 and of spherical nuclides centred at the magic nucleus - A possible scenario to understand the production of superheavy elements beyond copernicium

New experimental approaches to investigate the fission dynamics

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Discovery and cross-section measurement of 58 new fission products in projectile-fission of 750 · A MeV 238U

Cited by 155 publications

References 21 publications

Identification of New Isotopes 125Pd and 126Pd Produced by In-Flight Fission of 345 MeV/nucleon 238U: First Results from the RIKEN RI Beam Factory

Identification of New Isotopes 125Pd and 126Pd Produced by In-Flight Fission of 345 MeV/nucleon 238U: First Results from the RIKEN RI Beam Factory

A region of oblate nuclides centred at Z = 114 and of spherical nuclides centred at the magic nucleus - A possible scenario to understand the production of superheavy elements beyond copernicium

New experimental approaches to investigate the fission dynamics

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Identification of New Isotopes ¹²⁵Pd and ¹²⁶Pd Produced by In-Flight Fission of 345 MeV/nucleon ²³⁸U: First Results from the RIKEN RI Beam Factory

Identification of New Isotopes ¹²⁵Pd and ¹²⁶Pd Produced by In-Flight Fission of 345 MeV/nucleon ²³⁸U: First Results from the RIKEN RI Beam Factory