beta(+)/EC decay and systematic analysis of Ir-176,Ir-178

The gamma rays following the beta(+)/EC decay of Ir-176,Ir-178 nuclei have been investigated using in-beam gamma-ray experiment. In addition, with the aid of a helium-jet recoil fast tape transport system, the beta(+)/EC decay of Ir-176 was further studied, the new gamma rays were proved and a low-spin isomer was proposed in Ir-176. The isomeric state was analysized according to the systematics in neighboring nuclei.

Phase transition to color-flavor-locked matter and condensation of Goldstone bosons in neutron star matter

Deconfinement phase transition and condensation of Goldstone bosons in neutron star matter are investigated in a chiral hadronic model (also referred as to the FST model) for the hadronic phase (HP) and in the color-flavor-locked (CFL) quark model for the deconfined quark phase. It is shown that the hadronic-CFL mixed phase (MP) exists in the center of neutron stars with a small bag constant, while the CFL quark matter cannot appear in neutron stars when a large bag constant is taken. Color superconductivity softens the equation of state (EOS) and decreases the maximum mass of neutron stars compared with the unpaired quark matter. The K-0 condensation in the CFL phase has no remarkable contribution to the EOS and properties of neutron star matter. The EOS and the properties of neutron star matter are sensitive to the bag constant B, the strange quark mass m(s) and the color superconducting gap Delta. Increasing B and m(s) or decreasing Delta can stiffen the EOS which results in the larger maximum masses of neutron stars.

beta-delayed proton decays of Sm-133 and Yb-149

Sm-133 was produced via fusion evaporation in the reaction Ca-40+Ru-96. Its P-delayed proton decay was studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The possible spins and parities of 133Sm were extracted by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces of Sm-133 were calculated by using the Woods-Saxon Strutinsky method. Comparing the experimental and calculated results, the spins and parities Of Sm-133 were assigned to be 5/2(+) and 1/2(-), which is reconciled with our published simple (EC+beta(+)) decay scheme Of Sm-113 in 2001. In addition, our experimental data on the beta-delayed proton decay of Yb-149 reported in Eur. Phys. J., 2001, A12: 1-4 was also analyzed by using the same method. The spin and parity of Yb-149 was assigned to be 1/2-.

beta-delayed proton decays and spin assignments for Sm-133 and Yb-149

The proton-rich isotope Sm-133 was produced via the fusion evaporation reaction Ca-40 + Ru-96. Its beta-delayed proton decay was studied by p-gamma coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, gamma-transitions following the proton emission, as well as beta-delayed proton branching ratios to the low-lying states in the grand-daughter nucleus were determined. Comparing the observed beta-delayed proton branching ratios with statistical model calculations, the best agreement is found assuming that only one level with the spin of 3/2 in Sm-133 decays or two levels with the spins of 1/2 and 5/2 decay with similar half-lives. The configuration-constrained nuclear potential energy surfaces of Sm-133 were calculated using the Woods-Saxon-Strutinsky method, which suggests a 1/2-ground state and a 5/2(+) isomer with an excitation energy of 120 keV. Therefore, the simple(EC+beta(+)) decay scheme of Sm-133 in Eur. Phys. J.A 11,277(2001) has been revised. In addition, our previous experimental data on the beta-delayed proton decay of Yb-149 reported in Eur. Phys. J. A 12,1 ( 2 0 0 1) was also analyzed using the same method. The spin-parity of Yb-149 is suggested to be 1/2(-).

beta-delayed proton decays of Tb-140 and Dy-140 as well as the spin and parity of Dy-143

Tb-140 and Dy-141 were produced via fusion evaporation in the reaction Ca-40+Cd-106. Their beta-delayed proton decays were studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of Tb-140 and Dy-141 were extracted as 7(+/-) and 9/2(+/-), respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of Tb-140 and Dy-147 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 was also calculated by using the same method. From the NPES a 1/2(+) ground state and a 11/2(-) isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of Dy-143 reported in Eur. Phys. J., 2003, A16: 347-351.

beta-delayed proton decays and spin assignments for Tb-140, Dy-141 and Dy-143

The proton-rich isotopes Tb-140 and Dy-141 were produced via the fusion evaporation reaction Ca-40+ Cd-106. Their beta-delayed proton decays were studied by p-gamma coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, gamma-transitions following the proton emission, as well as beta-delayed proton branching ratios to the low-lying states in the grand-daughter nuclei were determined. Comparing the experimental data with statistical model calculations, the ground-state spins of Tb-140 and Dy-141 were found to be consistent with 7 and 9/2, respectively. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated using the Woods-Saxon-Strutinsky method, which suggest the ground-state spins and parities of Tb-140 and Dy-141 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 were calculated, which predict a 1/2(+) ground state and a 11/2(-) isomer with excitation energy of 198 keV. These findings are consistent with our previous experimental data on Dy-143 reported in Eur. Phys. J. A 16, 347 (2003).

beta(+)/EC-decay study of Ir-176 neutron-deficient isotope

The beta(+)/EC decay of doubly odd Ir-176 has been investigated using Nd-146(Cl-35, 5n gamma)Ir-176 heavy ion fusion evaporation reaction at 210MeV bombarding energy. With the aid of a helium-jet recoil fast tape transport system, the reaction products were transported to a low-background location for measurements. Based on the data analysis, the previously published gamma rays in Ir-176 decay were proved, moreover, 3 new levels and 10 new gamma rays were assigned to Ir-176 decay. The new level scheme of Os-176 with low excitation energy has been established. The time spectra of typical gamma rays clearly indicate a long-lived low-spin isomer in Ir-176 nuclide.

Experimental study of the beta-delayed proton decays of Er-145,Er-147

The beta-delayed proton decays of Er-145,Er-147 have been studied experimentally using the Ni-58 + Mo-92 reaction at beam energy of 383 MeV. On the basis of a He-jet apparatus coupled with a tape transport system, the beta-delayed proton radioactivities both from the nu s(1/2) ground state and the nu h(11/2) isomer in Er-145,Er-147 were observed by proton-gamma coincidence measurements. By analyzing the time distributions of the 4(+) -> 2(gamma)(+) transitions in the granddaughter nuclei Dy-144,Dy-146, the half-lives of 1.0 +/- 0.3 s and 1.6 +/- 0.2 s have been deduced for the nu h(11/2) isomers in Er-145,Er-147, respectively.

Properties of the beta-delayed proton decay of Ho-146

The proton-rich isotope Ho-148 was produced via the fusion-evaporation reaction Mo-92 (Ni-58, 3p1n). The beta-delayed proton decay of Ho-146 was studied by proton-gamma coincidence measurements using a He-jet tape transport system. The gamma-transitions in Tb-145 following the proton emissions were observed, and the beta-delayed proton branching ratios to the final states in the grand-daughter nucleus Tb-145 were determined. According to the relative branching ratios, the ground-state spin of Ho-146 has been proposed and the possible configuration discussed.

2.6 s isomer of Nd-129

Nd-129 was produced by irradiation of an enriched target of Ru-96 with a Ar-36 beam and studied by using a helium-jet fast tape transport system in combination with X-gamma and gamma-gamma coincidence measurements. A 2.6s isomer of Nd-129 was observed for the first time and tentatively proposed to be the configuration of 1/2[411].

Properties of the beta-Delayed Proton Decay of Er-147

The beta-delayed proton decay of Er-147 is studied experimentally using the Ni-58+Mo-92 reaction at a beam energy of 383 MeV. Based on a He-jet apparatus coupled with a tape transport system, the beta-delayed proton radioactivities both from the nu s(1/2) ground state and the nu h(11/2) isomer in Er-147 are identified by proton-gamma coincidence measurements. By analyzing the time distribution of the 4(+) -> 2(+) gamma transition in the grand-daughter nucleus Dy-146, a half-life of 1.6 +/- 0.2 s is determined for the nu h(11/2) isomer in Er-147. The half-life for the ground state of Er-147 is estimated to be 3.2 +/- 1.2 s.

Observation of a Possible New Isomer in Ir-175

The neutron deficient nuclide Ir-175 was produced by irradiation of Nd-146 with 210 MeV Cl-35 via a fusion-evaporation reaction channel. The reaction products were transported to a low-background location using a helium-jet recoil fast-moving tape-transport system for measurement. The experimental devices and data analysis method are introduced. Based on the decay-curve fitting of the beta-delayed gamma ray from Ir-175, realized by the least-square method, a new long-lived isomeric state of Ir-175 is proposed and briefly discussed.

Production of highly charged ion beams with SECRAL

Superconducting electron cyclotron resonance ion source with advanced design in Lanzhou (SECRAL) is an all-superconducting-magnet electron cyclotron resonance ion source (ECRIS) for the production of intense highly charged ion beams to meet the requirements of the Heavy Ion Research Facility in Lanzhou (HIRFL). To further enhance the performance of SECRAL, an aluminum chamber has been installed inside a 1.5 mm thick Ta liner used for the reduction of x-ray irradiation at the high voltage insulator. With double-frequency (18+14.5 GHz) heating and at maximum total microwave power of 2.0 kW, SECRAL has successfully produced quite a few very highly charged Xe ion beams, such as 10 e mu A of Xe37+, 1 e mu A of Xe43+, and 0.16 e mu A of Ne-like Xe44+. To further explore the capability of the SECRAL in the production of highly charged heavy metal ion beams, a first test run on bismuth has been carried out recently. The main goal is to produce an intense Bi31+ beam for HIRFL accelerator and to have a feel how well the SECRAL can do in the production of very highly charged Bi beams. During the test, though at microwave power less than 3 kW, more than 150 e mu A of Bi31+, 22 e mu A of Bi41+, and 1.5 e mu A of Bi50+ have been produced. All of these results have again demonstrated the great capability of the SECRAL source. This article will present the detailed results and brief discussions to the production of highly charged ion beams with SECRAL.

新一代多电荷态离子源的研究

离子源发展存在两大热点问题：其一强流高电荷态离子的产生；其二强流金 属离子的产生。为了获得强流高电荷态离子，我们设计制造了全超导 ECR 离子 源 SECRAL（Superconducting ECR ion source with Advanced design in Lanzhou） ， 该离子源采用了全新的超导磁体结构形式，工作于 18～28GHz 的微波频率。根据 scaling laws 和实验经验，我们确定了 SECRAL 离子源所需要的约束磁场场形， 并针对新的磁体结构设想，通过 TOSCA 程序进行了详细的计算，成功地设计出 满足我们场形要求的超导磁体物理模型。据此，我们进一步进行了超导磁体的力 学结构分析，为磁体机械工艺设计提供了参考依据，保证了超导磁体结构设计的 可靠性。源体建成后，经过一系列的测试和调束实验，不但验证了我们的设计和 分析是合理的、可靠的，而且创造了许多项束流调试的新世界纪录，我们分别获 得了 810 A eμ O7+ 、730 A eμ Ar 11+ 、220 A eμ Ar 14+ 、73 A eμ Ar 16+ 、483 A eμ Xe 20+ 等束 流。为了获得强流中低电荷态金属离子束，我们尝试探索一种原理、结构、工作 模式全新的离子源－外部电子注入PIG离子源（E-PIG） 。目前，我们基本按照我 们的初期设想设计建造了 E-PIG离子源，设计中采用了外部电子枪注入电子、空 心阴极、特殊的场形等手段来提高金属离子的电荷态和流强。经过初步的起弧调 试，我们发现在初期的设计中还存在一些问题亟待进一步整改。

3T超导螺线管的研制

超导螺线管广泛应用于核磁共振仪、粒子探测器等设备。本文设计了中心场值为3T，中心附近Φ30mm区域内均匀度达到1×10-4的超导螺线管。磁体线圈采用多芯NbTi-Cu复合超导线绕制，并利用铁轭屏蔽漏场。磁体采用温孔冷铁轭、全浸泡冷却方式结构。同时，为了减少辐射漏热，采用液氮冷屏、真空多层绝热结构。 本文重点对带有冷铁轭的超导螺线管的磁场进行了优化设计。设计过程中结合了专业磁场计算软件OPERA和多种优化方法。线圈采用六次槽型结构，利用遗传算法和优选法优化线圈尺寸；铁轭采用正交试验设计优化尺寸。 利用有限元软件ANSYS对超导磁体进行电磁力分析，并且对降温后线圈、支撑筒和箍筒的热应力进行了模拟计算。估算了支撑系统的传导漏热、磁体的辐射漏热以及剩余气体漏热。详细介绍了超导磁体绕制工艺，超导磁体液氦杜瓦的加工工艺，并且对杜瓦的绝热工艺进行了介绍。最后介绍了超导螺线管的总体加工进展