beta-decay study of the T-z =-2 proton-rich nucleus Mg-20

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">The beta decay of the drip-line nucleus Mg-20 gives important information on key astrophysical resonances in 20Na, which are relevant to the onset of the rapid proton capture process. A detailed beta-decay spectroscopic study of 20Mg was performed by a continuous-implantation method. A detection system was specially developed for charged-particle decay studies, giving improved spectroscopic information including the delayed proton energies, the half-life of 20Mg, the excitation energies, the branching ratios, and the log ft values for the states in Na-20 populated in the beta decay of Mg-20. A new proton branch was observed and the corresponding excited state in 20Na was proposed. The large isospin asymmetry for the mirror decays of Mg-20 and O-20 was also well reproduced. To resolve the long-standing problem about the astrophysically interesting 2645 keVresonance in Na-20 convincingly, a higher-statistics measurement may still be needed.</span

Significance of Heavy-Ion Beam Irradiation-Induced Avermectin B1a Production by Engineered Streptomyces avermitilis

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Heavy-ion irradiation technology has advantages over traditional methods of mutagenesis. Heavy-ion irradiation improves the mutation rate, broadens the mutation spectrum, and shortens the breeding cycle. However, few data are currently available regarding its effect on Streptomyces avermitilis morphology and productivity. In this study, the influence of heavy-ion irradiation on S. avermitilis when cultivated in approximately 10 L stirred-tank bioreactors was investigated. The specific productivity of the avermectin (AVM) B1a-producing mutant S. avermitilis 147-G58 increased notably, from 3885 to 5446 mu g/mL, approximately 1.6-fold, compared to the original strain. The mycelial morphology of the mutant fermentation processes was microscopically examined. Additionally, protein and metabolite identification was performed by using SDS-PAGE, 2-and 3-dimensional electrophoresis (2DE and 3DE). The results showed that negative regulation gene deletion of mutants led to metabolic process upregulating expression of protein and improving the productivity of an avermectin B1a. The results showed that the heavy-ion beam irradiation dose that corresponded to optimal production was well over the standard dose, at approximately 80Gy at 220 AMeV (depending on the strain). This study provides reliable data and a feasible method for increasing AVM productivity in industrial processes.</span

A high-throughput screening method for breeding Aspergillus niger with C-12(6+) ion beam-improved cellulase

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">In this study, a high-throughput screening method was established through the 24-square deep-well microliter plate (MTP) fermentation and micro-plate detection for large-scale screening of the mutants. It was suitable for screening a large number of mutants and improving the breeding efficiency after heavy-ion beam irradiation. Seventeen strains showed higher cellulase activity compared with the initial strain after the screening of plate and MTP fermentation. The filter paper activity and beta-glucosidase activity of Aspergillus niger H11201 had increased 38.74 and 63.23 % separately compared with A. niger H11 by shaking flask fermentation, and it was genetically stable after being passaged to nine generations. The results indicate that the high-throughput screening method can be used for the quick breeding of A. niger with high cellulase activity.</span

High power acceleration of an HSC type injector for cancer therapy

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">A hybrid single cavity (HSC) linac, which is formed by combining a radio frequency quadrupole (RFQ) and a drift tube (DT) structure into one interdigital-H (IH) cavity, is fabricated and assembled as a proof of principle injector for cancer therapy synchrotron, based on the culmination of several years of research. The HSC linac adopts a direct plasma injection scheme (DPIS), which can inject a high intensity heavy ion beam produced by a laser ion source (LIS). The input beam current of the HSC is designed to be 20 mA C</span><sup style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; line-height: 22px; background-color: rgb(248, 248, 248);">6+</sup><span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">&nbsp;ions. According to numerical simulations, the HSC linac can accelerate a 6-mA C</span><sup style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; line-height: 22px; background-color: rgb(248, 248, 248);">6+</sup><span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">beam, which meets the requirement of the needed particle number for cancer therapy (10</span><sup style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; line-height: 22px; background-color: rgb(248, 248, 248);">8-9</sup><span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">&nbsp;ions/pulse). The HSC injector with the DPIS method makes the existing multi-turn injection system and stripping system unnecessary, and can also bring down the size of the beam pipe in existing synchrotron magnets, which could reduce the whole cost of synchrotron. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured Q equal to 91% of the simulated value. A C</span><sup style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; line-height: 22px; background-color: rgb(248, 248, 248);">6+</sup><span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">&nbsp;ion beam extracted from the LIS was used for the HSC commissioning. In beam testing, we found the measured beam parameters agreed with simulations. More details of the measurements and the results of the high power test are reported in this paper.</span

Odd-even staggering in yields of neutron-deficient nuclei produced by projectile fragmentation

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Background: Fragment yields exhibit a strong odd-even staggering (OES). This OES has been experimentally observed in different fragmentation reactions with different projectile-target combinations. However, the experimental data are still scarce for fragments close to drip lines and the origin of this OES is not well understood.&nbsp;</span><br style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);" /> <span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Purpose: More experimental data are needed to explore the origin of this OES in fragment yields and to validate fragmentation reaction models, especially for nuclei close to the drip lines. To study the pronounced OES near the proton drip line, we measured the yields of T-z = -1 and T-z = -3/2 nuclei over a wide range of mass number.&nbsp;</span><br style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);" /> <span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Methods: The combination of a fragment separator and a storage ring at the Heavy Ion Research Facility in Lanzhou has been used to measure the yields of T-z = -1 and T-z = -3/2 fragments, produced by Ni-58 projectiles impinging on a beryllium target at an energy of about 463 MeV/nucleon.&nbsp;</span><br style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);" /> <span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Results: A very strong OES is observed in the measured yields of both T-z = -1 and T-z = -3/2 fragments. Our experimental data demonstrate that the shell structure has a significant impact on the magnitude of this OES. A comparison of different fragmentation reaction data indicates that this OES is almost independent of the projectile-target combinations and the fragmentation energy between 140 and 650 MeV/nucleon.&nbsp;</span><br style="margin: 0px; list-style: none; padding: 0px; color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);" /> <span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Conclusions: Our study reveals that the OES of fragment yields originates mainly from the OES of particle-emission threshold energies, which is very close to the OES of fragment yields when the Coulomb barrier is considered in particle-emission threshold energies</span

New development of laser ion source for highly charged ion beam production at Institute of Modern Physics

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">A laser ion source based on Nd:YAG laser has been being studied at the Institute of Modern Physics for the production of high intensity high charge state heavy ion beams in the past ten years, for possible applications both in a future accelerator complex and in heavy ion cancer therapy facilities. Based on the previous results for the production of multiple-charged ions from a wide range of heavy elements with a 3 J/8 ns Nd: YAG laser [Zhao et al., Rev. Sci. Instrum. 85, 02B910 (2014)], higher laser energy and intensity in the focal spot are necessary for the production of highly charged ions from the elements heavier than aluminum. Therefore, the laser ion source was upgraded with a new Nd: YAG laser, the maximum energy of which is 8 J and the pulse duration can be adjusted from 8 to 18 ns. Since then, the charge state distributions of ions from various elements generated by the 8 J Nd: YAG laser were investigated for different experimental conditions, such as laser energy, pulse duration, power density in the focal spot, and incidence angle. It was shown that the incidence angle is one of the most important parameters for the production of highly charged ions. The capability of producing highly charged ions from the elements lighter than silver was demonstrated with the incidence angle of 10 degrees and laser power density of 8 x 10(13) W cm(-2) in the focal spot, which makes a laser ion source complementary to the superconducting electron cyclotron resonance ion source for the future accelerator complex especially in terms of the ion beam production from some refractory elements. Nevertheless, great efforts with regard to the extraction of intense ion beams, modification of the ion beam pulse duration, and reliability of the ion source still need to be made for practical applications. (C) 2015 AIP Publishing LLC.</span

Highly Selective Ionic Transport through Subnanometer Pores in Polymer Films

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Novel transport phenomena through nanopores are expected to emerge as their diameters approach subnanometer scales. However, it has been challenging to explore such a regime experimentally. Here, this study reports on polymer subnanometer pores exhibiting unique selective ionic transport. 12 mu m long, parallel oriented polymer nanopores are fabricated in polyethylene terephthalate (PET) films by irradiation with GeV heavy ions and subsequent 3 h exposure to UV radiation. These nanopores show ionic transport selectivity spanning more than 6 orders of magnitude: the order of the transport rate is Li+&gt;Na+&gt;K+&gt;Cs+&gt;&gt; Mg2+&gt;Ca2+&gt;Ba2+, and heavy metal ions such as Cd2+ and anions are blocked. The transport can be switched off with a sharp transition by decreasing the pH value of the electrolyte. Structural measurements and molecular dynamics simulations suggest that the ionic transport is attributed to negatively charged nanopores with pore radii of approximate to 0.3 nm, and the selectivity is associated with the dehydration effect.</span

低能强流质子束空间电荷补偿度研究

<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">对于低能强流离子束来说,空间电荷效应的存在将导致束流发散、发射度增加等一系列问题,从而降低束流品质。幸运的是,当束流由离子源引出通过低能传输线时会与其中的剩余气体发生电离反应,产生二次电子与二次离子;二次电子在束流自身产生的电场作用下,在束流中积累并中和部分空间电荷,达到抑制空间电荷效应的效果。为了测量空间电荷中和程度,中国科学院近代物理研究所研制了一台三栅网式能量分析仪用以测量电离过程中产生的二次离子能量来间接计算空间电荷中和度。实验结果表明,对于40 keV, 18.5 mA的质子束,真空度为1.5*10~(-3) Pa时得到最佳补偿度;真空度一定的情况下,空间电荷补偿度随束流流强增加而变大。</span><span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">For high-intensity low-energy ion beams, space charge effect is a main cause of beam divergence and emittance growth. Fortunately, residual gas molecules in the drift space tend to be ionized and neutralize the beam space charge spontaneously. The level of Space Charge Neutralization (SCN) is measured through the detection of created secondary ion energy distribution in the beam region. A so-called non-intereeptive Three-grid Energy Analyzer (TEA) has been designed and manufactured at Institute of Modern Physics, Chinese Academy of Sciences (IMP). This paper will present the details of the TEA detector and the application to diagnose proton beam SCN level in the Low Energy Beam Transport (LEBT) line. As a preliminary result, for an 18.5 mA proton beam a best compensating point appears at the vacuum pressure of 1.5 * 10~(-3) Pa. And the neutralization level is advanced with the growth of beam current in a constant vacuum pressure.</span