Laboratory Astrophysics

Source SAGE

Date 2017

With the development of high-energy-density experimental facilities, such as high-power lasers, Z-pinch and electron beam ion traps or sources (EBIT/S) facilities, one can create extreme astrophysical conditions in the laboratory. This progress promotes the emergence of new research field ⎯ laboratory astrophysics (LA). LA, as an accessory to the astronomical observation, is a research field in laboratory for fundamental astrophysical processes or some astrophysical events that can be scaled-down to controllable phenomena.

Our group is focusing on the following subjects:

1. X-ray and EUV spectroscopy: X-ray and EUV photons are observed for various celestial objects, and a large amount of spectra with high-resolution are available by present and planned missions. But there are many missed emission sources from present available theoretical modeling codes due to their inherent physical process and/or atomic database, i.e. popular used MEKAL, Chianti and AtomDB, as well as Cloudy and Xstar. So our group constructs a spectroscopic modeling code ⎯ SASAL with multiple functions (i.e. applicable to collisional, and charge-exchange dominant plasmas with properties of non-thermal electrons, non-equilibrium, metastable population and real-time calculation for atomic parameters). Some spectroscopic diagnostic modules are setup, e.g. component and velocity of solar winds, as well as the high vacuum pressure in the EBIT/S chamber. There are still many issues and application modules to be overcome or complemented. Secondly, we perform data calculation for some fundamental atomic processes by using complete or semi-quantum and close-coupling methods for collisions between particles. Additionally, we also perform laboratory measurements for X-ray and EUV spectra to fulfill and benchmark the linelist in various spectral models by using the EBIT/S facility, and miniature the interaction region between the solar wind and cometary or planetary atmospheres by using intense lasers and EBIT/S.

2. Photoionization process: The photoionized plasmas widely exist in the universe, such as the X-ray binaries and AGN. The radiation from the accretion process would excite and ionize the surrounding medium to determine the properties of the plasmas. With theoretical models, the properties of astronomical objects can be obtained by analyzing the observed spectra, such as wind speeds, temperatures, densities, element abundances, and etc. The related photoionized plasmas and photoionizing process can be reproduced in the laboratories by using high-power laser facilities, such as Gekko-XII and SG-II. In the lab, the ionization parameters were about 10 erg cm/s (Physics of Plasma, 15, 073108), the obtained temperature of the black body radiation was up to around 0.5 keV, and the measured X-ray spectra are comparable to astronomical observations of X-ray binaries(Nature Physics, 5, 786). The experiment measurements help us to benchmark the theoretical models and to understand more about the astronomical objects.

3. Radiation opacity: Opacity is important to astrophysics for understanding the stellar evolution. With the development of high power laser, it has become possible to test and improve the theoretical opacity models by comparison with the measured opacity of laser-produced plasmas in laboratory. Very recently, large discrepancies are found between the iron opacity of theoretical models and those measured by Z-pinch experiments. These results offer great challenges and opportunities. The corresponding experiments are in preparation and will be carried on SG-II laser facility in China. These experiments would greatly advance the progress in this filed.

4. Collisionless shocks: Collisionless shocks (CSs) are ubiquitous in the universe, such as supernova remnants, gamma-ray bursts and solar wind etc. It is believed that CSs play an important role in the high-energy particles generation and the origin of cosmic rays. Counter-streaming flows system, as an appealing test-bed, has been used for study the generation mechanism of CSs. The formation and evolution of a pair of electrostatic shocks have been successfully observed using SG-II lasers in laboratory. In addition, the filamentation induced by the Weibel-type instability has also been observed as the evolution of the counter-streaming flows. These results obtained in laboratory will help us to understand the microphysical process of CS formation in the astrophysical scenario.

5. Jets: Astrophysical jets are spectacular and breathtaking phenomena observed to emanate from young stellar objects (YSOs), active galactic nuclei (AGN), and X-ray binary systems. They are observed with sizes and velocities of various orders of magnitude, and are well collimated over large distances with exquisite symmetries in the universe. We have studied the radiation cooling effect on the jet collimation using the C-shaped target in laboratory. It can be well-scaled under the transformation. We also used this collimated jet to study the “jet deflection” phenomenon in the HH 110/270 system and verified the flow-flow collision model.

Team Member

Staff: Guiyun Liang, Feilu Wang, Huigang Wei

Postdoc: Dawei Yuan

Phd student: Bo Han, Xiaoxing Pei

Master student: Jimin Peng