Ion Beam
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2021 ◽  
Vol 61 (03) ◽  
Xinshang Niu ◽  
Hongfei Jiao ◽  
Bin Ma ◽  
Jinlong Zhang ◽  
Xinbin Cheng ◽  

2021 ◽  
Vol 61 (03) ◽  
Jinlin Bai ◽  
Huasong Liu ◽  
Yugang Jiang ◽  
Lishuan Wang ◽  
Xiao Yang ◽  

2021 ◽  
Suresh Basnet ◽  
Anish Maskey ◽  
Atit Deuja ◽  
Raju Khanal

Abstract The effects of ion beam current associated with the streaming positive ions on the dust charge fluctuations and ion acoustic wave propagation in quiescent electronegative dusty plasma have been investigated using fluid theory. The dust charging phenomenon and unstable mode of ion waves are modified for two streaming conditions of positive ions which are extended and graphically illustrated. The dependencies of the growing and damping rate of ion waves on dust density and the size of dust grains are studied. The evolution of dust surface potential is found in the negative domain with the increase in concentration of negative ions and the instability rate for ion wave decreases. Furthermore, it is shown that the dust surface potential shifts into positive domain as the electrons are significantly depleted (and the plasma becomes ion-ion plasma) from the electronegative plasma and thus ion waves exhibit a damping phenomenon.

2021 ◽  
Vol 4 (4) ◽  
pp. 043004
Zhixiang Tao ◽  
Wei Zhao ◽  
Shang Wang ◽  
Boyu Zhao ◽  
Rushuai Hua ◽  

2021 ◽  
Zhiwen Chen ◽  
Yanan Wang ◽  
Maoqi Cai ◽  
Ruizhi Li ◽  
Tao Ren ◽  
Ion Beam ◽  

2021 ◽  
Vol 12 (1) ◽  
Michael Gatchell ◽  
João Ameixa ◽  
MingChao Ji ◽  
Mark H. Stockett ◽  
Ansgar Simonsson ◽  

AbstractLaboratory studies play a crucial role in understanding the chemical nature of the interstellar medium (ISM), but the disconnect between experimental timescales and the timescales of reactions in space can make a direct comparison between observations, laboratory, and model results difficult. Here we study the survival of reactive fragments of the polycyclic aromatic hydrocarbon (PAH) coronene, where individual C atoms have been knocked out of the molecules in hard collisions with He atoms at stellar wind and supernova shockwave velocities. Ionic fragments are stored in the DESIREE cryogenic ion-beam storage ring where we investigate their decay for up to one second. After 10 ms the initially hot stored ions have cooled enough so that spontaneous dissociation no longer takes place at a measurable rate; a majority of the fragments remain intact and will continue to do so indefinitely in isolation. Our findings show that defective PAHs formed in energetic collisions with heavy particles may survive at thermal equilibrium in the interstellar medium indefinitely, and could play an important role in the chemistry in there, due to their increased reactivity compared to intact or photo-fragmented PAHs.

OSA Continuum ◽  
2021 ◽  
Po-Kai Chiu ◽  
DonYau Chiang ◽  
Chien-Nan Hsiao ◽  

Sergey Vybin ◽  
V. A. Skalyga ◽  
Ivan Izotov ◽  
Sergey Golubev ◽  
Sergey Razin ◽  

Abstract The high efficiency of a new ion beam extraction system with a strongly inhomogeneous electric field has been experimentally demonstrated. Previously, this approach was proposed and analysed numerically by the authors. The experiment was carried out using a pulsed high-current electron-cyclotron resonance (ECR) ion source SMIS 37 with high frequency (37.5 GHz) and high power (100 kW) microwave plasma heating. The accelerating field strength is increased (when compared to a flat or a quasi-pierced geometry) in the plasma meniscus region due to its inhomogeneity. It allows for the increase of the ion acceleration rate and for expansion of the available range of current densities with effective ion beam formation. The experiment demonstrated the main advantages of this approach, such as: a significant decrease in the optimal accelerating voltage for certain values of current density; a possibility of ion beam formation with previously inaccessible current densities; a significant decrease in the ion flux to the puller in non-optimal modes of ion beam formation. Proton beams with a current density of up to 1.1 A cm-2 were obtained for the first time with an ECR ion source.

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Xiaoyun Ma ◽  
Mengling Zhang ◽  
Wanbin Meng ◽  
Xiaoli Lu ◽  
Ziheng Wang ◽  

Background. The dose distribution of heavy ions at the edge of the target region will have a steep decay during radiotherapy, which can better protect the surrounding organs at risk. Objective. To analyze the dose decay gradient at the back edge of the target region during heavy ion radiotherapy. Methods. Treatment planning system (TPS) was employed to analyze the dose decay at the edge of the beam under different incident modes and multiple dose segmentation conditions during fixed beam irradiation. The dose decay data of each plan was collected based on the position where the rear edge of the beam began to fall rapidly. Uniform scanning mode was selected in heavy ion TPS. Dose decay curves under different beam setup modes were drawn and compared. Results. The dose decay data analysis showed that in the case of single beam irradiation, the posterior edge of the beam was 5 mm away, and the posterior dose could drop to about 20%. While irradiation in opposite direction, the posterior edge of the beam was 5 mm away, and the dose could drop to about 50%. In orthogonal irradiation of two beams, the posterior edge of the beam could drop to about 30-38% in a distance of 5 mm. Through the data analysis in the TPS, the sharpness of the dose at the back edge of the heavy ion beam is better than that at the lateral edge, but the generated X-ray contamination cannot be ignored. Conclusions. The effect of uneven CT value on the dose decay of heavy ion beam should also be considered in clinical treatment.

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