Experimental demonstration of an electromagnetic pulse mitigation concept for a laser driven proton source.

The targets that are used to produce high-energy protons with ultra-high intensity lasers generate a strong electromagnetic pulse (EMP). To mitigate that undesired side effect, we developed and tested a concept called the "birdhouse." It consists in confining the EMP field in a finite volume and in dissipating the trapped electromagnetic energy with an electric resistor. A prototype was tested at a 10 TW 50 fs laser facility. The recorded average EMP mitigation ratio is about 20 for frequencies from 100 MHz to 6 GHz. The EMP mitigation ratio attains the level of 50 in the frequency range of 1-2 GHz where microwave emission is maximal. We measured the intensity of proton emission in two directions: along the laser propagation direction and along the edge of the proton beam. We observed that the "birdhouse" induces a two-fold increase of the intensity in the center of the proton beam and a two-fold reduction of the intensity on its edge. We did not observe any modification of the proton beam normalized spectrum.

Erratum: Physics of giant electromagnetic pulse generation in short-pulse laser experiments [Phys. Rev. E 91, 043106 (2015)].

This corrects the article DOI: 10.1103/PhysRevE.91.043106.

Publisher's Note: Dynamic model of target charging by short laser pulse interactions [Phys. Rev. E 92, 043107 (2015)].

This corrects the article DOI: 10.1103/PhysRevE.92.043107.

Dynamic model of target charging by short laser pulse interactions.

A model providing an accurate estimate of the charge accumulation on the surface of a metallic target irradiated by a high-intensity laser pulse of fs-ps duration is proposed. The model is confirmed by detailed comparisons with specially designed experiments. Such a model is useful for understanding the electromagnetic pulse emission and the quasistatic magnetic field generation in laser-plasma interaction experiments.

Physics of giant electromagnetic pulse generation in short-pulse laser experiments.

In this paper we describe the physical processes that lead to the generation of giant electromagnetic pulses (GEMPs) at powerful laser facilities. Our study is based on experimental measurements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralization current in the target holder and the electromagnetic emission shows that the source of the GEMP is the remaining positive charge inside the target after the escape of fast electrons accelerated by the ultra-intense laser. A simple model for calculating this charge in the thick target case is presented. From this model and knowing the geometry of the target holder, it becomes possible to estimate the intensity and the dominant frequencies of the GEMP at any facility.

Target charging in short-pulse-laser-plasma experiments.

Interaction of high-intensity laser pulses with solid targets results in generation of large quantities of energetic electrons that are the origin of various effects such as intense x-ray emission, ion acceleration, and so on. Some of these electrons are escaping the target, leaving behind a significant positive electric charge and creating a strong electromagnetic pulse long after the end of the laser pulse. We propose here a detailed model of the target electric polarization induced by a short and intense laser pulse and an escaping electron bunch. A specially designed experiment provides direct measurements of the target polarization and the discharge current in the function of the laser energy, pulse duration, and target size. Large-scale numerical simulations describe the energetic electron generation and their emission from the target. The model, experiment, and numerical simulations demonstrate that the hot-electron ejection may continue long after the laser pulse ends, enhancing significantly the polarization charge.

Placental site trophoblastic tumor (trophoblastic pseudotumor) of the uterus with metastases and fatal outcome. Clinical and autopsy observations of a case.

A 41-year-old woman who 5 years earlier had a hysterectomy for a placental site trophoblastic tumor (formerly called trophoblastic pseudotumor) was readmitted to the hospital with pelvic recurrence and multiple lung metastases. Despite an initial decrease in the size of the lung metastases and concomitant lowering of the serum values of human chorionic gonadotropin (beta-HCG) from 2,200 to 40 ng/ml, combined chemotherapy became ineffective. The patient died 4 months later with widespread metastases. The clinical course and the autopsy findings of this case are reported and compared with the two similar cases reported in the literature.