Notable improvements on LWFA through precise laser wavefront tuning.

Laser wakefield acceleration (LWFA) continues to grow and awaken interest worldwide, especially as in various applications it approaches performance comparable to classical accelerators. However, numerous challenges still exist until this can be a reality. The complex non-linear nature of the process of interaction between the laser and the induced plasma remains an obstacle to the widespread LWFA use as stable and reliable particle sources. It is commonly accepted that the best wavefront is a perfect Gaussian distribution. However, experimentally, this is not correct and more complicated ones can potentially give better results. in this work, the effects of tuning the laser wavefront via the controlled introduction of aberrations are explored for an LWFA accelerator using the shock injection configuration. Our experiments show the clear unique correlation between the generated beam transverse characteristics and the different input wavefronts. The electron beams stability, acceleration and injection are also significantly different. We found that in our case, the best beams were generated with a specific complex wavefront. A greater understanding of electron generation as function of the laser input is achieved thanks to this method and hopes towards a higher level of control on the electrons beams by LWFA is foreseen.

Coupling Effects in Multistage Laser Wake-field Acceleration of Electrons.

Staging laser wake-field acceleration is considered to be a necessary technique for developing full-optical jitter-free high energy electron accelerators. Splitting of the acceleration length into several technical parts and with independent laser drivers allows not only the generation of stable, reproducible acceleration fields but also overcoming the dephasing length while maintaining an overall high acceleration gradient and a compact footprint. Temporal and spatial coupling of pre-accelerated electron bunches for their injection in the acceleration phase of a successive laser pulse wake field is the key part of the staging laser-driven acceleration. Here, characterization of the coupling is performed with a dense, stable, narrow energy band of <3% and energy-selectable electron beams with a charge of ~1.6 pC and energy of ~10 MeV generated from a laser plasma cathode. Cumulative focusing of electron bunches in a low-density preplasma, exhibiting the Budker-Bennett effect, is shown to result in the efficient injection of electrons, even with a long distance between the injector and the booster in the laser pulse wake. The measured characteristics of electron beams modified by the booster wake field agree well with those obtained by multidimensional particle-in-cell simulations.

Decomposition of powerful axisymmetrically polarized laser pulses in underdense plasma.

Interaction of relativistically intense axisymmetrically polarized (radially or azimuthally polarized) laser pulses (RIAPLP) with underdense plasma is shown experimentally and theoretically to be essentially different from the interaction of conventional Gaussian pulses. The difference is clearly observed in distinct spectra of the side-scattered laser light for the RIAPLP and Gaussian pulses, as well as in the appearance of a spatially localized strong side emission of second harmonic of the laser pulse in the case of RIAPLP. According to our analysis based on three-dimensional particle-in-cell simulations, this is a result of instability in the propagation of RIAPLP in uniform underdense plasma.

Unique case of thrombotic thrombocytopenic purpura and diabetes insipidus.

Thrombotic thrombocytopenic purpura (TTP) is a rare and often fatal disorder characterized by thrombocytopenia, microangiopathic hemolytic anemia, mental status changes, and renal dysfunction. Central diabetes insipidus (CDI) is a rare disease due to anatomic lesions of the hypothalamicpituitary system associated with various underlying diseases, or trauma. We present an unusual case of TTP and CDI in a 47 year-old African American female who was admitted to our hospital with crampy abdominal pain and nausea. The patient had tachycardia, fever and hypotension. The patient subsequently became confused, developed seizures, and her renal function deteriorated. Bone marrow analysis showed adequate megakaryocytes while a peripheral smear revealed severe thrombocytopenia, polychromasia and schistocytes. The diagnosis of thrombotic thrombocytopenic purpura (TTP) was made and plasmapharesis initiated. Over the next few days, the patient developed severe polyuria with a rise in serum sodium. Central diabetes insipidus was diagnosed and DDAVP (desmopressin acetate, 1-deamino-8-D-arginine vasopressin) was given. However, DDAVP was stopped several times due to worsening thrombocytopenia. Renal function worsened and the patient expired. A review of the literature revealed only one case of report of TTP and central diabetes insipidus. Our case was the only one reporting the use of DDAVP in such a setting.