Knockout reaction mechanism studied by 6He projectile

Knockout reaction experiment was carried out by using the ⁶He beams at 61.2 MeV/u impinging on a CH₂ target. The α core fragments at forward angles were detected in coincidence with the recoiled protons at larger angles. From this exclusive measurement the valence nucleon knockout mechanism and the core knockout mechanism can be distinguished by the relation between the polar angles of the core fragments and the recoiled protons, respectively. It is demonstrated that the core knockout mechanism may result in some strong contamination to the real invariant mass spectrum.

     

30MeV/u 40Ar+115In反应中的IMF能谱

测量了30MeV/u ⁴⁰Ar束流轰击¹¹⁵In反应靶时出射的中等质量碎片(IMF)的能谱.通过比较在不同出射角度发射的同一种IMF的能谱,得到了IMF的发射机制随出射角的演化关系.在假定运动源速度和出射离子库仑位垒不随出射角变化的条件下,通过改变发射源的强度和核温度参量完成了对实验测得能谱的运动源拟合,并详细讨论了3个发射源所占份额和源强随出射角的演化关系.     

Experimental research into the two-proton emissions from ~(17,18) Ne,~(28) P and ~(28,29)S

Two-proton emissions from the excited states of 17,18Ne, 28P and 28,29S were investigated experimentally by the radioactive beams bombarding on the 197Au target via the Coulomb excitation. The complete-kinematics measurements were actualized by the stacks of silicon-strip detectors and CsI+PIN array detectors. The invariant mass of final systems as well as the relative momentum, opening angle, and relative energy of the two emitted protons was reconstructed under the framework of relativ istic kinematics. V...     

Speed of the internal pellet target in CSRm

Pellet target is one of the main candidate targets in CSRm (cooler storage ring’s main ring) for hadron physics studies. Pellet speed is an important physical parameter for the target. Larger pellet speed could shorten the interacting time interval between the pellet and the cyclotron beam, and thus results in a small temperature variation for the pellet. This could make the pellet facility work in a stable condition. A fluid dynamic simulation was carried out for the pellet speed, and it was found that the...     

Study of proton resonances in ~(18)Ne via resonant elastic scattering of ~(17)F+p and its astrophysical implication

The proton resonant properties in 18Ne, which determine the reaction rate of the key stellar 14O(α,p)17F reaction, have been studied by using a technique of proton resonant elastic scattering of 17F+p. A 4.22 MeV/nucleon 17F radioactive ion (RI) beam was produced via a projectile-fragmentation reaction, and separated by a Radioactive Ion Beam Line in Lanzhou (RIBLL). By bombarding a thick (CH2)n target, the energy spectra of the recoiled protons were measured by two ΔE-E silicon telescopes at the center-of-...     

RFQ冷却聚束器的离子引出系统

论述了RFQ冷却聚束器的两种离子引出系统——静电引出和小型RFQ方法的模拟结果，并通过流体力学方法计算了设计中的静电引出系统的氦气流量和系统可能获得的真空度. 研究结果表明：在较低氦气气压时，应该选用小型RFQ引出方法，以获得更好的束流品质，而在较高氦气气压时，只能选用静电引出方法. 另外，由于设计中的RFQ冷却聚束器经常工作于高氦气气压条件下，因此高纯度氦气的回收和再利用是必需的.     

The properties of halo structure for 17B

The total reaction cross section (1724 ± 93 mb) of ¹⁷B at the energy of 43.7 A MeV on C target has been measured by using the transmission method at the Radioactive Ion Beam Line in Lanzhou (RIBLL). Assuming ¹⁷B consists of a core ¹⁵B plus two halo neutrons, the total cross section of ¹⁷B on C target was calculated with the zero-range Glauber model, where double Gaussian density distributions and Gaussian plus HO density distributions were used. It can fit the experimental data very well. The characteristic of halo structure for ¹⁷B was found with a large diffusion of the neutrons density distribution. Supported by the National Natural Science Foundation of China (Grant Nos. 10475098, 10605033 and 10221003), the Chinese Academy of Sciences (Grant Nos. CXTD-J2005-1 and KJCX2-SW-N18), and Hundred Talent Project of CAS (Grant No. 0501080BR0)     

Study of proton resonances in 18Ne via resonant elastic scattering of 17F+p and its astrophysical implication

The proton resonant properties in ¹⁸Ne, which determine the reaction rate of the key stellar ¹⁴O(α,p)¹⁷F reaction, have been studied by using a technique of proton resonant elastic scattering of ¹⁷F+p. A 4.22 MeV/nucleon ¹⁷F radioactive ion (RI) beam was produced via a projectile-fragmentation reaction, and separated by a Radioactive Ion Beam Line in Lanzhou (RIBLL). By bombarding a thick (C_H2) _n target, the energy spectra of the recoiled protons were measured by two ΔE-E silicon telescopes at the center-of-mass scattering angles of θ _c.m.≈175°±5°, θ _c.m.≈152°±8°, respectively. Several proton resonances in ¹⁸Ne were observed clearly. A further R-matrix analysis of the experimental data is under way to determine the resonant parameters. The present work reports the preliminary results briefly.     

Experimental research into the two-proton emissions from 17,18Ne, 28P and 28,29S

Two-proton emissions from the excited states of ^17,18Ne, ²⁸P and ^28,29S were investigated experimentally by the radioactive beams bombarding on the ¹⁹⁷Au target via the Coulomb excitation. The complete-kinematics measurements were actualized by the stacks of silicon-strip detectors and CsI+PIN array detectors. The invariant mass of final systems as well as the relative momentum, opening angle, and relative energy of the two emitted protons was reconstructed under the framework of relativistic kinematics. Visible proton-proton correlations were observed in these systems. The mechanisms of two-proton emission were analyzed in a simple schematic model, in which the extreme decay modes like ²He cluster emission, three-body phase-space decay, and two-body sequential decay were taken into account. With the help of Monte-Carlo simulations, the two protons emitted from the 6.15 MeV excited state of ¹⁸Ne and the excited states in the energy region of 9.6–10.4 MeV of ²⁹S, respectively, exhibited prominent features of ²He cluster decay while for the other cases, no obvious diproton emissions were observed.