Bended probe diagnostics of the plasma characteristics within an ECR ion source with a rectangular waveguide

To reveal the argon plasma characteristics within the entire region of an electron cyclotron resonance（ECR） ion source, the plasma parameters were diagnosed using a bended Langmuir probe with the filament axis perpendicular to the diagnosing plane. Experiments indicate that,with a gas volume flow rate and incident microwave power of 4 sccm and 8.8 W, respectively,the gas was ionized to form plasma with a luminous ring. When the incident microwave power was above 27 W, the luminous ring was converted to a bright column, the dark area near its axis was narrowed, and the microwave power absorbing efficiency was increased. This indicates that there was a mode transition phenomenon in this ECR ion source when the microwave power increased. The diagnosis shows that, at an incident microwave power of 17.4 W, the diagnosed electron temperature and ion density were below 8 eV and 3×10^17 m^-3, respectively, while at incident microwave power levels of 30 W and 40 W, the maximum electron temperature and ion density were above 11 eV and 6.8×10^17 m^-3, respectively. Confined by magnetic mirrors, the higher density plasma region had a bow shape, which coincided with the magnetic field lines but deviated from the ECR layer.

Experiment and analysis of the neutralization of the electron cyclotron resonance ion thruster

An electron cyclotron resonance ion thruster must emit an electron current equivalent to its ion beam current to prevent the thruster system from being electrically charged. This operation is defined as neutralization. The factors which influence neutralization are categorized into the ion beam current parameters, the neutralizer input parameters, and the neutralizer position. To understand the mechanism of neutralization, an experiment and a calculation study on how these factors influence thruster neutralization are presented. The experiment results show that the minimum bias voltage of the neutralizer was -60 V at the ion beam current of 80 mA for the argon propellant, and a critical gas flow rate existed, below which the coupling voltage increased sharply. Based on the experiment, the neutralization was analyzed by means of a onedimensional calculation model. The computation results show that the coupling voltage was influenced by the beam divergence and the negative potential zone near the grids.

METTL7A-mediated m6A modification of corin reverses bisphosphonates-impaired osteogenic differentiation of orofacial BMSCs

Bisphosphonate-related osteonecrosis of jaw(BRONJ)is characterized by impaired osteogenic differentiation of orofacial bone marrow stromal cells(BMSCs).Corin has recently been demonstrated to act as a key regulator in bone development and orthopedic disorders.However,the role of corin in BRONJ-related BMSCs dysfunction remains unclarified.A m6A epitranscriptomic microarray study from our group shows that the CORIN gene is significantly upregulated and m6A hypermethylated during orofacial BMSCs osteogenic differentiation.Corin knockdown inhibits BMSCs osteogenic differentiation,whereas corin overexpression or soluble corin(sCorin)exerts a promotion effect.Furthermore,corin expression is negatively regulated by bisphosphonates(BPs).Corin overexpression or sCorin reverses BPs-impaired BMSCs differentiation ability.Mechanistically,we find altered expression of phos-ERK in corin knockdown/overexpression BMSCs and BMSCs under sCorin stimulation.PD98059(a selective ERK inhibitor)blocks the corin-mediated promotion effect.With regard to the high methylation level of corin during osteogenic differentiation,we apply a non-selective m6A methylase inhibitor,Cycloleucine,which also blocks the corin-mediated promotion effect.Furthermore,we demonstrate that METTL7A modulates corin m6A modification and reverses BPs-impaired BMSCs function,indicating that METTL7A regulates corin expression and thus contributes to orofacial BMSCs differentiation ability.To conclude,our study reveals that corin reverses BPs-induced BMSCs dysfunction,and METTL7A-mediated corin m6A modification underlies corin promotion of osteogenic differentiation via the ERK pathway.We hope this brings new insights into future clinical treatments for BRONJ.