Dynamical signals in fragmentation reactions : Time scale determination from three fragments correlations by using the 4 [Pi] Chimera multidetector

For fragments emitted in the reactions 124Sn + 64Ni and 112Sn + 58Ni at 35 AMeV, isotopic composition and velocity correlations have been studied as a function of the centrality of the collision, using the 4 Chimera multidetector. We have investigated the time scale for fragments formation, in order to distinguish between prompt dynamical and sequential statistical emission. Promptly emitted light fragments (Z ≤9) produced in the mid-rapidity domain are characterised by larger N/Z ratio and stronger angular anisotropies than those produced in sequential statistical emission. Results are compared with stochastic BNV code simulations obtained for primary fragments. Valuable information on the symmetry term of the nuclear equation of state at sub-saturation densities are obtained

Isoscaling in neck fragmentation

Production of intermediate mass fragments (IMF) has been studied in semi-peripheral 124Sn (35AMeV) + 64Ni and 112Sn (35AMeV) + 58Ni reactions. Our recently proposed new method of an analysis of the neck- like fragmentation processes that provides information on the IMFs time equence and time scale is reviewed. Isotopic analysis of so characterized IMFs gives evidence for neutron enrichment of mid-velocity fragments. A clear isoscaling behavior is found despite the short emission time scale. Evolution of the isoscaling parameters from semi-peripheral to central collisions is discussed

Combining Expansion Microscopy and STED Nanoscopy for the Study of Cellular Organization

Expansion microscopy (ExM) is a novel method that allows super-resolutionimaging with conventional microscopes(1, 2). It consists in soaking the cellswith a polymer, inducing the polymerization to form a dense meshworkthroughout the cell, cross-linking the fluorophores to the polymer and, afterdigestion of cellular protein, rehydrating of the sample. The swelling ofthe polymer gel led to a fourfold isotropic stretching of the sample. Therefore,it increases the distance between two objects that otherwise couldnot be seen as two different things with an ordinary microscope. One of the drawback of sucha technique is the long preparation made of several stages, i.e. immunostaining,gelation, digestion and expansion. They are really crucial steps for a good im-aging post-expansion.In our work we present a comparison between ExM and stimulated emissiondepletion (STED) nanoscopy(3). Our aim is to study the e possible combinationof STED and ExM as a method to further enhance the final resolution achiev-able. We will in particularly take advantage of the use of separation of photonsby lifetime tuning (SPLIT) STED (4).We show application of these methods from single fixed cells to slices of fixedmouse retina tissue.We are also interested in applying the approach to high-density compartmentslike the cell nucleus to decipher the high-order structure organization of chro-matin-DN

Encoding and decoding spatio-temporal information for super-resolution microscopy

The challenge of increasing the spatial resolution of an optical microscope beyond the diffraction limit can be reduced to a spectroscopy task by proper manipulation of the molecular states. The nanoscale spatial distribution of the molecules inside the detection volume of a scanning microscope can be encoded within the fluorescence dynamics and decoded by resolving the signal into its dynamics components. Here we present a robust and general method to decode this information using phasor analysis. As an example of the application of this method, we optically generate spatially controlled gradients in the fluorescence lifetime by stimulated emission. Spatial resolution can be increased indefinitely by increasing the number of resolved dynamics components up to a maximum determined by the amount of noise. We demonstrate that the proposed method provides nanoscale imaging of subcellular structures, opening new routes in super-resolution microscopy based on the encoding/decoding of spatial information through manipulation of molecular dynamics

Two-Photon Excitation STED Microscopy with Time-Gated Detection

We report on a novel two-photon excitation stimulated emission depletion (2PE-STED) microscope based on time-gated detection. The time-gated detection allows for the effective silencing of the fluorophores using moderate stimulated emission beam intensity. This opens the possibility of implementing an efficient 2PE-STED microscope with a stimulated emission beam running in a continuous-wave. The continuous-wave stimulated emission beam tempers the laser architecture's complexity and cost, but the time-gated detection degrades the signal-to-noise ratio (SNR) and signal-to-background ratio (SBR) of the image. We recover the SNR and the SBR through a multi-image deconvolution algorithm. Indeed, the algorithm simultaneously reassigns early-photons (normally discarded by the time-gated detection) to their original positions and removes the background induced by the stimulated emission beam. We exemplify the benefits of this implementation by imaging sub-cellular structures. Finally, we discuss of the extension of this algorithm to future all-pulsed 2PE-STED implementationd based on time-gated detection and a nanosecond laser source

On-board digital signal processing for 4 pi-detector large-area telescopes

The digital pulse shape data acquisition (DAQ)system used by the large area telescopes of the 4 pi-multidetector CHIMERA requires transferring large amount of data to the computer. This is necessary so that the same information can be extracted from the detector pulses as in previous analog based systems. To overcome this problem, we have used a sampling ADC-board equipped with two TigerSHARC digital signal processors. The board receives the data and reconstructs the event parameters online. The data volume is significantly reduced by transmitting to the DAQ only the reconstructed event parameters

Charge identification in large area planar silicon detectors, using digital pulse shape acquisition

The capability of digital pulse shape technique to acquire data from CHIMERA detection cells (Si-CSI(TI) telescopes) has been evidenced in our previous works. We have now applied this technique to the charge discrimination of the products stopped in the silicon detectors. Large area totally depleted CHIMERA planar silicon detectors (5 cm x 5 cm area, 300 pm thick) in both rear and front side injection have been used. In preliminary tests full charge identification for the reaction products up to Z = 11 have been obtained for products both crossing (DE-E technique) and stopping in the silicon detector, using a 21 MeV/u Ne-20 beam at the LNS Superconducting Cyclotron in Catania. The quality of the obtained results clearly indicates that the digital signal processing approach is able to give excellent results in this application, too

High resolution mass identification using a 100MS/s sampling ADC

In order to improve the resolution in mass identification, we have applied digital signal processing to time of flight measurements directly acquaring silicon detector and RF pulse forms. In the present contribution, we report the results obtained at different sampling frequencies (mass identification up to A=33 for the reaction products produced by a 20.5 AMeV 20Ne beam on 27Al target)