Double-layered target and identification method of individual target correlated with evaporation residues

Kaji, D.; Morimoto, K.

doi:10.1016/j.nima.2015.04.042

Cited by 8 publications

(4 citation statements)

References 8 publications

(7 reference statements)

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“…However, among the six nuclides ( 65 As, 69 Br, 73 Rb, 66 Se, 70 Kr, and 74 Sr ) which are the counterparts for calculating Q p -and Q 2p -values, only the masses of 65 As and 69 Br A 3.30 MeV/nucleon 36 Ar 10+ beam, with maximum intensity of 3 pµA, was provided by the RIKEN linear accelerator RILAC. Sixteen Mo nat S 2 targets mounted on a 300 mm diameter rotating wheel [21] were employed to produce neutron-deficient nuclei through fusion-evaporation reactions via nat S( 36 Ar,X). The Mo nat S 2 targets were prepared by a spray coating technique [22] on 3 µm Ti backing foils.…”

Section: Introductionmentioning

confidence: 99%

Atomic masses of intermediate-mass neutron-deficient nuclei with relative uncertainty down to 35-ppb via multireflection time-of-flight mass spectrograph

Kimura

Ito

Kaji

et al. 2018

International Journal of Mass Spectrometry

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High-precision mass measurements of 63 Cu, 64−66 Zn, 65 Ga, 65−67 Ge, 67 As, 78,81 Br, 80 Rb, and 79 Sr were performed utilizing a multireflection time-of-flight mass spectrograph combined with the gas-filled recoil ion separator GARIS-II. In the case of 65 Ga, a mass uncertainty of 2.1 keV, corresponding to a relative precision of δm/m = 3.5 × 10 −8 , was obtained and the mass value is in excellent agreement with the 2016 Atomic Mass Evaluation. For 67 Ge and 81 Br, where masses were previously deduced through indirect measurements, discrepancies with literature values were found. The feasibility of using this device for mass measurements of nuclides more neutron-deficient side, which have significant impact on the rp-process pathway, is discussed.have been determined experimentally, with uncertainties of 85 keV [8] and 40 keV [9], respectively. For the others, only theoretical predictions are given. A recent Q-value sensitivity study pointed out that the 65 As mass uncertainty has significant impact on the light curves and the ash compositions of X-ray bursts [10].High-precision experimental mass data of nuclides near the N = Z line are also necessary for verification of the Standard Model through the unitarity of the Cabibbo-Kobayashi-Masukawa (CKM) matrix. The "corrected" Ft-values of super allowed 0 + → 0 + β + -decay between T = 1 analog states are directly related to the dominant term in the top-row sum of the CKM matrix [11]. To calculate the Ft-values, the necessary nuclear parameters are partial lifetimes of the 0 + → 0 + transition and the corresponding Q EC -values. For nuclear masses, a relative precision of δm/m 5 × 10 −8 is required. The unitarity of the CKM matrix is confirmed to the level of 1.2 × 10 −4 with the uncertainties of present nuclear data [12]. A large fraction of the nuclear uncertainty stems from the mass uncertainty of 66 As (30 keV [5]) and the ambiguity in the 70 Br mass value [12,6].Half-lives of these as-yet insufficiently studied nuclides, excluding highly proton-unbound 69 Br and 73 Rb, span from tens to hundreds of milliseconds. These short half-lives make them difficult to effectively measure with Penning traps. In contrast, the multireflection time-of-flight mass spectrograph (MRTOF-MS) has advantages, discussed below.The MRTOF-MS has been developed for both mass measurement and isobar separation techniques in recent years. Typical mass resolving power of MRTOF-MS reaches R m > 10 5 with short measurement times of less than 10 ms. MRTOF-MS have been applied for mass measurement of heavy nuclei [13,14,15] and light neutron-rich nuclei [16,17,18] in several facilities. The achieved relative mass uncertainties have so far reached the order of δm/m ∼ 10 −7 , providing measurements relevant for nuclear-structure physics and some astrophysics. However, the measurement precision reported so far from on-line MRTOF-MS measurements is not sufficient for rp-process and unitarity of CKM matrix.The SHE-mass facility at RIKEN has been constructed to enable mass measurements of super-hea...

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Section: Introductionmentioning

confidence: 99%

Atomic masses of intermediate-mass neutron-deficient nuclei with relative uncertainty down to 35-ppb via multireflection time-of-flight mass spectrograph

Kimura

Ito

Kaji

et al. 2018

International Journal of Mass Spectrometry

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“…The 208 Pb target segments were prepared by evaporation onto 60 µg/cm 2 carbon backings until an average thickness of 450 µg/cm 2 was achieved. The target segments were mounted on a 30 cm diameter target wheel [12] that was nominally rotated at 2000 rpm during irradiation.…”

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confidence: 99%

Reduction of contaminants originating from primary beam by improving the beam stoppers in GARIS-II

Kimura

Kaji

Ito

et al. 2021

Nuclear Instruments and Methods in Physics Research Section A:

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“…Experimental conditions, reactions, and primary beam energies for each measured isotope are included in Table I 2 Ti backings for actinide targets and 60-μg=cm 2 C backing for other targets and were mounted on a 300-mm wheel [27] which rotated at 2000 rpm during irradiation.…”

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“…A 48 Ca primary beam of ∼0.3 pµA intensity was used to produce 249,250,251 Md and 254 No via cold-fusion reactions with nat Tl and 208 Pb targets. All targets had a thickness of ∼500 µg/cm 2 with 1.4-mg/cm 2 Ti backings for actinide targets and 60-µg/cm 2 C backing for other targets, and were mounted on a 300-mm wheel [27] which Results for all isotopes measured are listed in Table I; the mass values are compared with AME16 [33] values in Fig. 6.…”

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confidence: 99%

First Direct Mass Measurements of Nuclides around Z=100 with a Multireflection Time-of-Flight Mass Spectrograph

Ito¹,

Schury²,

Wada³

et al. 2018

Phys. Rev. Lett.

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The masses of 246 Es, 251 Fm, and the transfermium nuclei 249−252 Md and 254 No, produced by hot-and cold-fusion reactions, in the vicinity of the deformed N ¼ 152 neutron shell closure, have been directly measured using a multireflection time-of-flight mass spectrograph. Mt, were determined. These new masses were compared with theoretical global mass models and demonstrated to be in good agreement with macroscopic-microscopic models in this region. The empirical shell gap parameter δ 2n derived from three isotopic masses was updated with the new masses and corroborates the existence of the deformed N ¼ 152 neutron shell closure for Md and Lr. DOI: 10.1103/PhysRevLett.120.152501 Precision mass measurements of unstable nuclei, providing a direct measure of the nuclear binding energy, are invaluable for the study of nuclear shell evolution and collective effects, such as deformations, far from stability [1,2]. For transfermium nuclei and the yet poorly investigated region towards the superheavy nuclei (SHN), where proton repulsion becomes a generally dominant feature, the description of nuclear lifetimes depends crucially on shell stabilization effects mainly driven by deformed shells [3][4][5]. Theoretical studies with increasing particle numbers investigate the so-called "island of stability" [6], where features like the continuing decrease of energy gaps [7] and the emergence of shape coexistence [8] have a crucial impact on the predicted position and localization of stability regions and the corresponding lifetimes of the nuclei. Although the first experimental evidence for SHN has reached the region of the predicted subshell closure at N ¼ 162 [9-11], the deformed shell closure at N ¼ 152 for transfermium nuclei (see, e.g., [12]) and, as recently pointed out, weaker shell effects in the vicinity [13], still represents the cutting edge for thorough experimental investigations. The transfermium nuclei, however, can be produced only online, in heavy-ion fusion and nucleon transfer reactions, and consequently only low yields are available for study, necessitating highly efficient techniques. Direct mass measurements of transfermium nuclei have so far been performed for only six nuclei-four isotopes of nobelium and two isotopes of lawrencium-with the Penning trap mass spectrometer SHIPTRAP [14,15].In this Letter, we report the first implementation of a multireflection time-of-flight mass spectrograph (MRTOF MS) for transfermium nuclei as shown in Fig. 1, including new mass measurements of 246 Es, 251 Fm, [249][250][251][252]

show abstract

Double-layered target and identification method of individual target correlated with evaporation residues

Cited by 8 publications

References 8 publications

Atomic masses of intermediate-mass neutron-deficient nuclei with relative uncertainty down to 35-ppb via multireflection time-of-flight mass spectrograph

Atomic masses of intermediate-mass neutron-deficient nuclei with relative uncertainty down to 35-ppb via multireflection time-of-flight mass spectrograph

Reduction of contaminants originating from primary beam by improving the beam stoppers in GARIS-II

First Direct Mass Measurements of Nuclides around Z=100 with a Multireflection Time-of-Flight Mass Spectrograph

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