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The discharged capillary plasma channel has been extensively studied as a high-gradient particle acceleration and transmission medium. A novel measurement method of plasma channel density profiles has been employed, where the role of plasma channels guiding the advantages of lasers has shown strong appeal. Here, we have studied the high-order transverse plasma density profile distribution using a channel-guided laser, and made detailed measurements of its evolution under various parameters. The paraxial wave equation in a plasma channel with high-order density profile components is analyzed, and the approximate propagation process based on the Gaussian profile laser is obtained on this basis, which agrees well with the simulation under phase conditions. In the experiments, by measuring the integrated transverse laser intensities at the outlet of the channels, the radial quartic density profiles of the plasma channels have been obtained. By precisely synchronizing the detection laser pulses and the plasma channels at various moments, the reconstructed density profile shows an evolution from the radial quartic profile to the quasi-parabolic profile, and the high-order component is indicated as an exponential decline tendency over time. Factors affecting the evolution rate were investigated by varying the incentive source and capillary parameters. It can be found that the discharge voltages and currents are positive factors quickening the evolution, while the electron-ion heating, capillary radii and pressures are negative ones. One plausible explanation is that quartic profile contributions may be linked to plasma heating. This work helps one to understand the mechanisms of the formation, the evolutions of the guiding channel electron-density profiles and their dependences on the external controllable parameters. It provides support and reflection for physical research on discharged capillary plasma and optimizing plasma channels in various applications.
Post-acceleration of protons in helical coil targets driven by intense, ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’ self-discharge. The acceleration length of protons can exceed a few millimeters, and the acceleration gradient is of the order of GeV/m. How to ensure the synchronization between the accelerating electric field and the protons is a crucial problem for efficient post-acceleration. In this paper, we study how the electric field mismatch induced by current dispersion affects the synchronous acceleration of protons. We propose a scheme using a two-stage helical coil to control the current dispersion. With optimized parameters, the energy gain of protons is increased by four times. Proton energy is expected to reach 45 MeV using a hundreds-of-terawatts laser, or more than 100 MeV using a petawatt laser, by controlling the current dispersion.
Family functioning is associated with anxiety and depression. Perinatal depression and anxiety are common and influence the well-being of women, partners and their offspring. However, little is known about differences in associations between family functioning and mood symptoms in women and their partners in early pregnancy.
Investigating differences in associations between family functioning and anxious and depressive symptoms in women and their partners in early pregnancy.
In total, 171 woman–partner pairs were enrolled. The Edinburgh Postnatal Depression Scale (EPDS), Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder 7-Item scale (GAD-7) and Family Assessment Device (FAD) were performed. Correlation analysis and multiple linear regression analysis were applied to investigate the associations.
In pregnant women, all the subscale scores on the FAD were correlated with total scores on the EPDS and GAD-7 (all P < 0.05), whereas only the Roles subscale showed a predicting effect in regression models (P < 0.01). In partners, all the subscale scores on the FAD were related to total scores on the PHQ-9 (all P < 0.05), whereas only the Problem Solving subscale showed a predicting effect (P = 0.029).
Our findings indicate that family functioning in the domain of roles is associated with anxious and depressive symptoms in pregnant women and functioning in the domain of problem solving is associated with depressive symptoms in partners. Clinicians should pay special attention to roles and problem solving when assessing mood symptoms in pregnant women and their partners. This study also provides a basis for family health education in early pregnancy.
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