Dear colleagues and friends of the HI Jena,

welcome to the latest issue of the HI Jena newsletter. We use this opportunity to report about recent activities at the HI Jena, and to inform you about upcoming conferences and seminars.

Kind Regards,
Helmholtz Institute Jena

Observation of Gigawatt Class THz Pulses from a Compact Laser-Driven Particle Accelerator

High-power laser generated plasmas are known to be compact sources of high frequency electromagnetic radiation. In addition to being useful secondary radiation source, analysis of these radiation can also reveal the inner dynamics of these complex plasmas. Because most of the studies on the plasma-generated radiation have concentrated on the visible, EUV and X-ray bands, little is known about laser-plasmas as low frequency radiation emitters. In our latest research, we have recorded extremely high-power terahertz radiation (T rays) from relativistic laser-solid interaction [1]. T ray pulses with a minimum 700 μJ energy and sub-picosecond duration (that is, GW peak power levels) were generated by the transient sheath field which is responsible for the acceleration of protons and ions to MeV energies in laser-plasma experiments. The energy of this T-ray pulses are only rivaled by the light-sources based on conventional accelerators [2]. Our latest work, characterized the generated T rays in space and time and investigated the relation between the ion acceleration process and the T ray emission. We have found that the power of the emitted radiation is proportional to the square of the particle number and their magnitude of acceleration. Our estimates suggest that about 1% of the energy is converted from ions to T rays.

The experiments were performed at the JETI laser system at IOQ. Special geometry collection optics and non-collinear single-shot pump-probe diagnostics ensured the optimum collection of the T-rays and their detection respectively. Two dimensional PIC simulations carried out by the group of Dr. Paul Gibbon at the Jülich Super Computing Centre evidenced the generation of transient current at the target rear surface which could lead the generation of T rays. Spatial and temporal analysis of the Poynting vector shows also the emission of non-collinear low frequency radiation.

Our work has shown that high-power laser-solid interaction is a promising scalable source of highpower T rays. Optimal focusing of this radiation could generate electric fields of the order of 10⁹ V/m and associated magnetic fields of the order of few Tesla, thus opening the way for many exciting studies in nonlinear optics and material science. Moreover, the simultaneous generation of the highpower T rays and accelerated ion beam may be exploited to re-accelerate the ions to even higher energies by driving a miniaturized RF-cavity with T rays.

References:
[1] A.Gopal, et al., Physical Review Letters, 111 074802 (2013).
[2] A.Gopal, et al., Optics Letters, 38 4705 (2013).

ICAMDATA Conference was held at Helmholtz Institute Jena

The 9th International Conference on Atomic and Molecular Data and Their Applications (ICAMDATA 2014) took place on 21-15 September 2014 in Jena. The ICAMDATA 2014 was organized jointly by the Helmholtz Institute Jena and Friedrich Schiller University Jena. It was continuing the series of international conferences whose aim is to promote the use of atomic and molecular data in various fields of science and technology, and to provide a forum for the interaction of data producers, database designers and compilers, and data users. Almost 100 participants from more than 20 countries came to Jena in order to discuss a number of challenging topics, such as:

• Application and needs of atomic and molecular data
• Atomic and molecular data collections, assessment and dissemination
• Experimental and theoretical atomic and molecular data generation