An ultra-thin diamond membrane as a transmission particle detector and vacuum window for external microbeams

Several applications of external microbeam techniques demand a very accurate and controlled dose delivery. To satisfy these requirements when post-sample ion detection is not feasible, we constructed a transmission single-ion detector based on an ultra-thin diamond membrane. The negligible intrinsic noise provides an excellent signal-to-noise ratio and enables a hit-detection efficiency of close to 100%, even for energetic protons, while the small thickness of the membrane limits beam spreading. Moreover, because of the superb mechanical stiffness of diamond, this membrane can simultaneously serve as a vacuum window and allow the extraction of an ion microbeam into the atmosphere

Glueball Production in Peripheral Heavy-Ion Collisions

The method of equivalent quanta is applied both to photon-photon and, by analogy, to double pomeron exchange in heavy-ion collisions. This Weizs\"acker-Williams approach is used to calculate production cross sections for the glueball candidate $f_J(1710)$ meson via photon-photon and pomeron-pomeron fusion in peripheral heavy-ion collisions at both RHIC and LHC energies. The impact-parameter dependence for total and elastic cross sections are presented, and are compared to results for proton-proton collisions.Comment: 15 pages, 6 figure

Grain refining in additively manufactured titanium using boron nitride nanosheets

The functionalization of additive manufacturing (AM) powders with nucleating particles has the potential to alter the grain structure, and hence the mechanical properties of 3D printed structures. We have investigated use of hexagonal boron nitride (BN) nanosheets to modify the microstructure of Ti parts produced by laser-based powder bed fusion (PBF-LB). The components were 3D printed from commercially pure titanium (cp-Ti) powders coated with small amounts (1.5 vol% ≈ 0.77 wt%) of BN nanosheets. As a comparison, pure cp-Ti parts were also built under the same processing conditions. Small- and wide-angle X-ray scattering (SAXS-WAXS) analysis of the 3D printed test structures revealed that BN addition significantly refined the α-Ti grain size and randomized the α-Ti texture. It was observed that grain-refined Ti-BN samples were harder and more brittle than their pure cp-Ti counterparts. This research provides new insights for grain refining using functional powder feedstocks with relatively simple powder pre-processing, and may be applied more broadly in laser-based metal AM

Charge multiplication effect in thin diamond films

Herein, we report on the enhanced sensitivity for the detection of charged particles in single crystal chemical vapour deposition (scCVD) diamond radiation detectors. The experimental results demonstrate charge multiplication in thin planar diamond membrane detectors, upon impact of 18MeV O ions, under high electric field conditions. Avalanche multiplication is widely exploited in devices such as avalanche photo diodes, but has never before been reproducibly observed in intrinsic CVD diamond. Because enhanced sensitivity for charged particle detection is obtained for short charge drift lengths without dark counts, this effect could be further exploited in the development of sensors based on avalanche multiplication and radiation detectors with extreme radiation hardnes

Glueball production in radiative J/psi, Upsilon decays

Using a bound-state model of weakly bound gluons for glueballs made of two gluons and a natural generalization of the perturbative QCD formalism for exclusive hadronic processes, we present results for glueball production in radiative J/psi, Upsilon decays into several possible glueball states, including L \not= 0 ones. We perform a detailed phenomenological analysis, presenting results for the more favored experimental candidates and for decay angular distributions.Comment: RevTeX4, 26 pages, 11 eps figure

The evaluation of radiation damage parameter for CVD diamond

There are a few different phenomenological approaches that aim to track the dependence of signal height in irradiated solid state detectors on the fluence of damaging particles. However, none of them are capable to provide a unique radiation hardness parameter that would reflect solely the material capability to withstand high radiation environment. To extract such a parameter for chemical vapor deposited (CVD) diamond, two different diamond detectors were irradiated with proton beams in MeV energy range and subjected afterwards to ion beam induced charge (IBIC) analysis. The change in charge collection efficiency (CCE) due to defects produced was investigated in context of a theoretical model that was developed on the basis of the adjoint method for linearization of the continuity equations of electrons and holes. Detailed modeling of measured data resulted with the first known value of the kr product for diamond, where k represents the number of charge carriers’ traps created per one simulated primary lattice vacancy and r represents the charge carriers’ capture cross section. As discussed in the text, this product could be considered as a true radiation damage parameter

Ultralong-term high-density data storage with atomic defects in SiC

There is an urgent need to increase the global data storage capacity, as current approaches lag behind the exponential growth of data generation driven by the Internet, social media and cloud technologies. In addition to increasing storage density, new solutions should provide long-term data archiving that goes far beyond traditional magnetic memory, optical disks and solid-state drives. Here, we propose a concept of energy-efficient, ultralong, high-density data archiving based on optically active atomic-size defects in a radiation resistance material, silicon carbide (SiC). The information is written in these defects by focused ion beams and read using photoluminescence or cathodoluminescence. The temperature-dependent deactivation of these defects suggests a retention time minimum over a few generations under ambient conditions. With near-infrared laser excitation, grayscale encoding and multi-layer data storage, the areal density corresponds to that of Blu-ray discs. Furthermore, we demonstrate that the areal density limitation of conventional optical data storage media due to the light diffraction can be overcome by focused electron-beam excitation.Comment: 8 pages, 4 figure