Quantum Beam Science

This research investigated the performance of spark-plasma erosion-based machining, also known as electrical discharge machining, for micro-hole drilling in SS316L and Ti-6Al-4V under various spark-plasma formation conditions, with 27 experimental combinations of capacitance, voltage, and electrode feed rate. Spark-plasma conditions at various discharge energies were found to play a major role in influencing machining time and overcut, which were considered two responses to evaluate machining performance. Increasing the voltage from 80 to 180 V at 100 pF decreased machining time from 2553 s to 564 s for SS316L and from 2608.2 s to 570.6 s for Ti-6Al-4V, but it increased overcut from 6 to 17.5 µm and from 8 to 22 µm, respectively. At 10,000 pF and 180 V, machining times of 51.6 s (SS316L) and 62.4 s (Ti-6Al-4V) were obtained, with maximum overcut values of 62.5 µm and 73.5 µm, respectively. Analysis of variance revealed that voltage strongly controlled machining time (~64%), while capacitance dominated overcut (64–69%). Ti-6Al-4V required 5–20% more machining time and exhibited a higher overcut due to its lower thermal conductivity and higher strength. The experimental observations indicated consistent plasma formation and favorable spark to achieve the required geometric accuracy and process productivity for the fabrication of high-quality biomedical components from SS316L and Ti-6Al-4V.

Quantum beams-including X-rays, synchrotron radiation, electrons, neutrons, ions, and ultrafast photon sources-are indispensable tools for probing the structure, dynamics, and electronic properties of matter. The excitation time scale ${\tau }_{exc}$ is defined operationally as the characteristic temporal interval governing externally imposed energy deposition events within the interaction volume, such as pulse duration, bunch spacing, or beam dwell time. Interpretation of beam–matter interactions has traditionally relied on steady-state or quasi-equilibrium assumptions, implicitly presuming that intrinsic material relaxation processes can accommodate externally imposed excitation. Recent advances in high-brightness synchrotron sources, X-ray free-electron lasers (XFELs), and pulsed electron beams increasingly operate in regimes where this assumption is strained, and systematic nonequilibrium effects, radiation damage, and irreversible transformations are reported even under routine experimental conditions. This work examines the role of time-scale mismatch between beam-driven energy deposition and intrinsic material relaxation as a governing constraint in beam–matter interactions. Analyzing the hierarchy of excitation, electronic relaxation, phonon coupling, and thermal diffusion time scales, the analysis introduces a dimensionless mismatch parameter $\mathsf{\Lambda }={\displaystyle \frac{{\tau }_{rel}}{{\tau }_{exc}}}$, which quantifies the competition between externally imposed excitation and intrinsic relaxation processes in beam–matter interactions. The resulting framework provides a unified physical interpretation of beam-induced damage, signal distortion, dose dependence, and nonlinear response across quantum beam modalities, framing these effects as consequences of forced nonequilibrium dynamics rather than technique-specific artifacts.

Some windowless semiconductor photodiodes can detect not only photons but also charged particles, cover a wide spectral range including a part of the ionizing radiation region and, thus, play important roles for synchrotron radiation experiments. To understand the spectral, angular and polarizing properties of semiconductor photodiodes, complex amplitude coefficients of transmittance or reflectance are calculated based on rigorous formulation using Fresnel equations with complex optical constants of the composing materials, whose validity was verified by comparison with experiments. Concrete examples of the behavior on the complex plane are shown as a function of complex optical constants, film thickness, angle of incidence and the wavelength. The results show that the optical properties of the layered system are sensitive to its layer thickness, the angle of incidence and the wavelength in the ultraviolet region where optical indices of the composing materials steeply change. It has been shown that oblique incidence photodiodes are useful as polarization-sensitive devices, and that the graphical technique using the amplitude coefficients expressed on the complex plane is effective and powerful to search for optimal conditions for complex optical constants, film thickness and/or angle of incidence.