Optical probing of laser-induced expansion of levitating microspheres

In the present work, the expansion dynamics of levitating microspheres following the interaction with a fs-short laser pulse in the intensity regime of 1015 −1016 W/cm2 is investigated in a pump-probe experiment. The study comprises two plasma diagnostics: an intrinsic probing along the laser axis via the pump pulse, fixed at t = 0 ps, and a time-variable lateral probing on a separate probe pulse. In both cases, the transmitted light is recorded via a scatter screen, providing a very simple diagnostic tool that can be implemented in most high-power laser experiments. In order to extract a plasma density distribution from the recorded inline holograms, the experiment is reproduced via numerical simulations using the Python package LightPipes. The simulation setup is calibrated by comparison to experimental conditions such as focus size, beam profiles and holograms of defined polystyrene spheres. Several radial symmetric models are investigated for modeling the density distribution of the plasma at different times during its evolution by comparing simulation results against recorded experimental images. The best agreement is found for a Gaussian density distribution with an additional, decentralized Gaussian component. The validity of this empirically determined model is further strengthened by simulations using the hydrodynamic code RALEF, where experimentally obtained values for the spatial and temporal intensity distribution are used as input. The temporal course of the expanding density distribution is compared to a simple model assuming hydrodynamic expansion of the plasma. The good agreement between experimental data and the model allows determining physical quantities such as laser absorption and relate them to experimental conditions of the plasma. The findings of this work are a first step towards studying the expansion of micrometer spherical targets at intensities well above the plasma generation threshold and are particularly relevant for future experiments investigating the interaction of relativistically intense laser pulses with density-tailored, sub-focus sized microplasmas, e.g. in the field of laser-ion acceleration

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Temporally Resolved Intensity Contouring (TRIC) for characterization of the absolute spatio-temporal intensity distribution of a relativistic, femtosecond laser pulse

Today's high-power laser systems are capable of reaching photon intensities up to $10^{22}$ W/cm^2, generating plasmas when interacting with material. The high intensity and ultrashort laser pulse duration (fs) make direct observation of plasma dynamics a challenging task. In the field of laser-plasma physics and especially for the acceleration of ions, the spatio-temporal intensity distribution is one of the most critical aspects. We describe a novel method based on a single-shot (i.e. single laser pulse) chirped probing scheme, taking nine sequential frames at framerates up to THz. This technique, to which we refer as temporally resolved intensity contouring (TRIC) enables single-shot measurement of laser-plasma dynamics. Using TRIC, we demonstrate the reconstruction of the complete spatio-temporal intensity distribution of a high-power laser pulse in the focal plane at full pulse energy with sub picosecond resolution.Comment: Daniel Haffa, Jianhui Bin and Martin Speicher are corresponding author

I-BEAT: New ultrasonic method for single bunch measurement of ion energy distribution

The shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens' principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. This novel method, which we refer to as Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a generalization of the ionoacoustic approach. Featuring compactness, simple operation, indestructibility and high dynamic ranges in energy and intensity, I-BEAT is a promising approach to meet the needs of petawatt-class laser-based ion accelerators. With its capability of completely monitoring a single, focused proton bunch with prompt readout it, is expected to have particular impact for experiments and applications using ultrashort ion bunches in high flux regimes. We demonstrate its functionality using it with two laser-driven ion sources for quantitative determination of the kinetic energy distribution of single, focused proton bunches.Comment: Paper: 17 Pages, 3 figures Supplementary Material 16 pages, 7 figure

Whole-genome plasma sequencing reveals focal amplifications as a driving force in metastatic prostate cancer

Genomic alterations in metastatic prostate cancer remain incompletely characterized. Here we analyse 493 prostate cancer cases from the TCGA database and perform whole-genome plasma sequencing on 95 plasma samples derived from 43 patients with metastatic prostate cancer. From these samples, we identify established driver aberrations in a cancer-related gene in nearly all cases (97.7%), including driver gene fusions (TMPRSS2:ERG), driver focal deletions (PTEN, RYBP and SHQ1) and driver amplifications (AR and MYC). In serial plasma analyses, we observe changes in focal amplifications in 40% of cases. The mean time interval between new amplifications was 26.4 weeks (range: 5–52 weeks), suggesting that they represent rapid adaptations to selection pressure. An increase in neuron-specific enolase is accompanied by clonal pattern changes in the tumour genome, most consistent with subclonal diversification of the tumour. Our findings suggest a high plasticity of prostate cancer genomes with newly occurring focal amplifications as a driving force in progression

Tumor-associated copy number changes in the circulation of patients with prostate cancer identified through whole-genome sequencing

Background Patients with prostate cancer may present with metastatic or recurrent disease despite initial curative treatment. The propensity of metastatic prostate cancer to spread to the bone has limited repeated sampling of tumor deposits. Hence, considerably less is understood about this lethal metastatic disease, as it is not commonly studied. Here we explored whole-genome sequencing of plasma DNA to scan the tumor genomes of these patients non-invasively. Methods We wanted to make whole-genome analysis from plasma DNA amenable to clinical routine applications and developed an approach based on a benchtop high-throughput platform, that is, Illuminas MiSeq instrument. We performed whole-genome sequencing from plasma at a shallow sequencing depth to establish a genome-wide copy number profile of the tumor at low costs within 2 days. In parallel, we sequenced a panel of 55 high-interest genes and 38 introns with frequent fusion breakpoints such as the TMPRSS2-ERG fusion with high coverage. After intensive testing of our approach with samples from 25 individuals without cancer we analyzed 13 plasma samples derived from five patients with castration resistant (CRPC) and four patients with castration sensitive prostate cancer (CSPC). Results The genome-wide profiling in the plasma of our patients revealed multiple copy number aberrations including those previously reported in prostate tumors, such as losses in 8p and gains in 8q. High-level copy number gains in the AR locus were observed in patients with CRPC but not with CSPC disease. We identified the TMPRSS2-ERG rearrangement associated 3-Mbp deletion on chromosome 21 and found corresponding fusion plasma fragments in these cases. In an index case multiregional sequencing of the primary tumor identified different copy number changes in each sector, suggesting multifocal disease. Our plasma analyses of this index case, performed 13 years after resection of the primary tumor, revealed novel chromosomal rearrangements, which were stable in serial plasma analyses over a 9-month period, which is consistent with the presence of one metastatic clone. Conclusions The genomic landscape of prostate cancer can be established by non-invasive means from plasma DNA. Our approach provides specific genomic signatures within 2 days which may therefore serve as 'liquid biopsy'

The (q,t)(q,t)-Gaussian Process

We introduce a two-parameter deformation of the classical Bosonic, Fermionic, and Boltzmann Fock spaces that is a refinement of the $q$-Fock space of [BS91]. Starting with a real, separable Hilbert space $H$, we construct the $(q,t)$-Fock space and the corresponding creation and annihilation operators, $\{a_{q,t}(h)^\ast\}_{h\in H}$ and $\{a_{q,t}(h)\}_{h\in H}$, satifying the $(q,t)$-commutation relation $a_{q,t}(f)a_{q,t}(g)^\ast-q \,a_{q,t}(g)^\ast a_{q,t}(f)= _{_H}\, t^{N},$ for $h,g\in H$, with $N$ denoting the number operator. Interpreting the bounded linear operators on the $(q,t)$-Fock space as non-commutative random variables, the analogue of the Gaussian random variable is given by the deformed field operator $s_{q,t}(h):=a_{q,t}(h)+a_{q,t}(h)^\ast$, for $h\in H$. The resulting refinement is particularly natural, as the moments of $s_{q,t}(h)$ are encoded by the joint statistics of crossings \emph{and nestings} in pair partitions. Furthermore, the orthogonal polynomial sequence associated with the normalized $(q,t)$-Gaussian $s_{q,t}$ is that of the $(q,t)$-Hermite orthogonal polynomials, a deformation of the $q$-Hermite sequence that is given by the recurrence $zH_n(z;q,t)=H_{n+1}(z;q,t)+[n]_{q,t}H_{n-1}(z;q,t),$ with $H_0(z;q,t)=1$, $H_1(z;q,t)=z$, and $[n]_{q,t}=\sum_{i=1}^n q^{i-1}t^{n-i}$. The $q=0<t$ specialization yields a new single-parameter deformation of the full Boltzmann Fock space of free probability. The probability measure associated with the corresponding deformed semicircular operator turns out to be encoded, in various forms, via the Rogers-Ramanujan continued fraction, the Rogers-Ramanujan identities, the $t$-Airy function, the $t$-Catalan numbers of Carlitz-Riordan, and the first-order statistics of the reduced Wigner process.Comment: The present version reverts to v2, by removing former Lemma 13 that contained an erro