Institutional Repository of Institute of Modern Physics, CAS
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Design study on medium beta superconducting half-wave resonator at IMP
No full text<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 325-MHz superconducting half-wave resonator has been designed with beta = 0.51. Three shapes of the inner conductors (race track, ring shape and elliptical shape) were optimized to decrease the peak electromagnetic fields and minimize the dissipated RF power on the cavity walls. In order to suppress the operation frequency shift caused by fluctuations of the helium pressure and maximize the tuning ranges, the frequency shifts and mechanical properties were studied on the electric and magnetic areas. The helium vessel was designed to keep the mechanical structure as robust as possible.</span
High-energy proton emission and Fermi motion in intermediate-energy heavy-ion collisions
No full text<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);">An antisymmetrized molecular dynamics model (AMD-FM), modified to take into account the Fermi motion explicitly in its nucleon-nucleon collision process, is presented. Calculated high-energy proton spectra are compared with those of Ar-40 + V-51 at 44 MeV/nucleon from Coniglione et al. [Phys. Lett. B 471, 339 (2000)] and those of Ar-36 + Ta-181 at 94 MeV/nucleon from Germain et al. [Nucl. Phys. A 620, 81 (1997)]. Both of the experimental data are reasonably well reproduced by the newly added Fermi boost in the nucleon-nucleon collision process without additional processes, such as a three-body collision or a short-range correlation. The production mechanism of high-energy protons in intermediate-energy heavy-ion collisions is discussed.</span
Shell Evolution Study for New Magic Number N =32 via Isochronous Mass Spectrometry
No full text<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);">Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed.</span
Development of higher power density evaporative cooling magnet coils in ECR ion source
No full text<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);">Traditional electron cyclotron resonance ( ECR) ion source coil with higher power density have some disadvantages, such as high pressure in the water-cooling system, restricted cooling ability, complex maintenance and operation system. A new ECR ion source coil was designed by using self-circulation evaporative cooling technology. The new design is based on the principle of self-circulation evaporative cooling, besides, the layout structure of ECR ion source coil and high operation reliability are both considered. The coil is composed by disk coil arrays. Vertical cooling channels are set among unit coils, where evaporative cooling coolant flows automatically driven by the heat of coils. According to the parameter index of LECR - DRAGON ion source magnet coil, the test model of evaporative cooling magnet coil was built. The experimental results show that the window current density of the new designed coil can be 12A/mm</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);">2</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);"> , which can maintain a long-term stable and reliable running. The evaporative cooling magnet coil can meet the requirements of practical engineering.</span
New development of laser ion source for highly charged ion beam production at Institute of Modern Physics
No full text<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
High power acceleration of an HSC type injector for cancer therapy
No full text<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);"> 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);"> 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);"> 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
Highly Selective Ionic Transport through Subnanometer Pores in Polymer Films
No full text<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+>Na+>K+>Cs+>> Mg2+>Ca2+>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
High power acceleration of an HSC type injector for cancer therapy (Retracted Article. See vol.40,099101,2016)
No full text近玻尔速度氙离子激发钒的K壳层X射线
No full text<span id="ChDivSummary" name="ChDivSummary">测量了2.4—6.0 MeV Xe<sup>20+</sup>离子轰击V靶表面过程中辐射的X射线.计算了V的K壳层X射线发射截面,并将实验结果与平面波恩近似、ECPSSR、两体碰撞近似的理论计算进行了对比.讨论了近玻尔速度非对称碰撞过程中,BEA模型估算高电荷态重离子激发内壳层电离的修正因素.结果表明,综合考虑库仑偏转和有效电荷态修正后,BEA理论与实验结果符合较好. </span><a id="ChDivSummaryMore" style="DISPLAY: none">更多</a><a id="ChDivSummaryReset" style="DISPLAY: none">还原</a><br /><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 X-ray emission spectra produced by 2.4-6.0 MeV Xe20+ ions impacting on vanadium surface were measured. The V K-shell X-ray production cross sections were extracted from the experimental yield data and compared with the theoretical predictions of the binary encounter approximation (BEA), the plane wave born approximation (PWBA), and the energy-loss coulomb-repulsion perturbed-stationary-state relativist (ECPSSR). In order to predict reasonably the inner-shell ionization induced by highly charged heavy ions during the asymmetric collisions at near the Bohr velocity, the corrections of BEA model are discussed. It is found that the X-ray production cross section induced by highly charged heavy ions moving at near the Bohr velocity is on the magnitude of 1 barn, which is almost four orders of magnitude larger than that induced by proton. The ECPSSR, which is regarded as the best model to simulate the inner-shell ionization by light ions, may underestimate the experimental data at least three orders of magnitude. The PWBA model presents a prediction to the results on an order of magnitude better than the ECPSSR simulation, but gives a worse tendency than the BEA model. The BEA calculations, corrected both by Coulomb repulsion and effective nuclear charge, present the best agreement with the experimental results. It is proposed, that in the energy region near the Bohr velocity, during the asymmetric collisions of Xe20+ ions with V atoms, the K-shell electron of V is ionized by direct ionization, and that it can be described by the binary encounter process between the xenon ions and the bound electrons. The X-ray production cross section can be simulated by BEA model, but the corrections of Coulomb repulsion and effective nuclear charge must be considered.</span
H~(1+)和He~(2+)激发Au 靶的M-X 射线辐射
No full text<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);">利用兰州重离子加速器国家实验室提供的H~(1+)和He~(2+)的离子束入射Au 靶表面, 测量了激发靶原子的M壳层特征X 射线辐射. 实验结果显示: 靶原子的特征X 射线M_alpha 和M_zeta 产额以及X 射线产生截面随入射离子的动能增加而增加, 实验获得X 射线产生截面数值与利用BEA 近似、PWBA 模型以及ECPSSR 理论估算的结果相比较大, 实验截面随动能增加的趋势同PWBA模型估算的趋势较为接近. 通过进一步分析, 我们认为: 当入射离子接近高Z 靶原子时, 由于高Z 靶原子的M 壳层电子束缚能相对较小, 使靶原子产生双重离化和多重离化, 荧光产额显著增强, 使X 射线产生截面增大.</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);">The X-ray emissions from H1+ and He2+ beams impinging on Au surface are measured. The results show that the yields and production cross sections of Mzeta and Malpha of target atom Au increased with the kinetic energy of H~(1+) and He~(2+). The measured production cross sections are higher than the theoretical predictions based on the PWBA approximation, the BEA approximation and ECPSSR theory. The measured production cross sections increased trend with ionic kinetic energy close to the theoretical predictions based on the PWBA. The fluorescence yield is enhanced dramatically owing to multiple vacancies as the projectiles approach target atoms. In the low projectile-energy region (E <1 MeV), because the projectiles velocities are nearly the M-shell electronic Bohr velocity of the high-Z target atom, and the bound of target atomic nucleus to electron decrease, so multiple ionization effects easily occur. One would have to conclude that these theories clearly fail at low velocities due to the electrons be assumed to be at rest in the early stage of these theories were constituted.</span