RESUMO
The breakthrough provided by plasma-based accelerators enabled unprecedented accelerating fields by boosting electron beams to gigaelectronvolt energies within a few centimeters [1-4]. This, in turn, allows the realization of ultracompact light sources based on free-electron lasers (FELs) [5], as demonstrated by two pioneering experiments that reported the observation of self-amplified spontaneous emission (SASE) driven by plasma-accelerated beams [6,7]. However, the lack of stability and reproducibility due to the intrinsic nature of the SASE process (whose amplification starts from the shot noise of the electron beam) may hinder their effective implementation for user purposes. Here, we report a proof-of-principle experiment using plasma-accelerated beams to generate stable and reproducible FEL light seeded by an external laser. FEL radiation is emitted in the infrared range, showing the typical exponential growth of its energy over six consecutive undulators. Compared to SASE, the seeded FEL pulses have energies 2 orders of magnitude larger and stability that is 3 times higher.
RESUMO
Background: Intravenous drug users (IVDUs) represent a very small group of patients affected by chronic wounds (CWs). Objectives: To assess the risk factors for CWs in IVDUs, to improve their treatment. Methods: A retrospective review of 7 IVDUs with CWs was performed at the Dermatology of the University of Bologna. Results: A history of 10 years of the most frequent injection was heroin in the gaiter area. The most observed comorbidities were HIV, HCV and HBV. They were treated most with an alginate with silver dressing with an average follow-up of 2.8 years. Conclusions: We would like to highlight the importance of clinical history in this type of patients and that in our experience specialized skin wounds risk assessment and management could be useful, aside from traditional compression therapy.
RESUMO
The possibility to accelerate electron beams to ultra-relativistic velocities over short distances by using plasma-based technology holds the potential for a revolution in the field of particle accelerators1-4. The compact nature of plasma-based accelerators would allow the realization of table-top machines capable of driving a free-electron laser (FEL)5, a formidable tool to investigate matter at the sub-atomic level by generating coherent light pulses with sub-ångström wavelengths and sub-femtosecond durations6,7. So far, however, the high-energy electron beams required to operate FELs had to be obtained through the use of conventional large-size radio-frequency (RF) accelerators, bound to a sizeable footprint as a result of their limited accelerating fields. Here we report the experimental evidence of FEL lasing by a compact (3-cm) particle-beam-driven plasma accelerator. The accelerated beams are completely characterized in the six-dimensional phase space and have high quality, comparable with state-of-the-art accelerators8. This allowed the observation of narrow-band amplified radiation in the infrared range with typical exponential growth of its intensity over six consecutive undulators. This proof-of-principle experiment represents a fundamental milestone in the use of plasma-based accelerators, contributing to the development of next-generation compact facilities for user-oriented applications9.
RESUMO
We present the experimental evidence of the generation of coherent and statistically stable two-color free-electron laser radiation obtained by seeding an electron beam double peaked in energy with a laser pulse single spiked in frequency. The radiation presents two neat spectral lines, with time delay, frequency separation, and relative intensity that can be accurately controlled. The analysis of the emitted radiation shows a temporal coherence and a shot-to-shot regularity in frequency significantly enhanced with respect to the self-amplified spontaneous emission.
