Lightweight laser scanning systems on UAV are becoming crucial for agriculture and forestry but require suitable calibration to ensure accuracy. Existing in situ calibration techniques rely on man-made features that may be lacking in field environments and require special manoeuvres. This study proposes a static calibration technique to estimate boresight misalignment angles between the IMU and the laser unit in a controlled setting. The approach can use two distinct control entities: points and planes. The process involves: (1) assembly of a calibration field; (2) levelling the system on a static platform; (3) data acquisition and raw data retrieval; and (4) determination of boresight angles via Least Squares Adjustment (LSA). The mathematical model was modified to integrate points and planes directly from raw sensor data, minimising errors from positioning systems and time synchronisation. The method was evaluated using an Ibeo LUX scanner. After applying the estimated boresight angles, the regenerated point cloud was validated by measuring distances between points and corresponding ground planes. The results yielded a standard deviation of approximately 2.5 cm. The proposed technique achieved suitable accuracy, with errors falling below the sensor’s nominal measurement uncertainty. This suggests the method is a promising pre-flight calibration solution, though further precision gains would require higher-end laser units.
This work presents a covariance-aware extension of the hybrid nonlinear-kicker (NLK) injection framework. While previous baseline studies established centroid action reduction and hardware-aware NLK placement for idealized beams, the present study addresses finite-beam optimization using a realistic, position-dependent eight-wire kick profile. A realistic NLK field not only corrects the injected-beam centroid but also induces an amplitude-dependent shear across the internal phase-space ellipse. Depending on the injected covariance and ellipse orientation, this shear can either reduce or enhance beam filamentation. To exploit this mechanism, the AC-septum angle is treated as a trajectory-control knob for the injected centroid, while transfer-line matching is used to control the injected covariance matrix. We use ID2-downstream as the primary optics-favored case, as its high βN simultaneously increases nonlinear-field sampling and reduces the required correction kick. Furthermore, at this location, the injected beam is close to a matched, near-upright covariance condition (αbeam≈0). We also examine ID1 middle and ID1 downstream as trajectory-controllable alternatives, and formulate a combined optimization over septum angle, transfer-line optics, and NLK current. Operational measurements of AC-septum stability, first-turn trajectory reproducibility, septum response, and injection-bump response validate the available trajectory-control authority required for realistic NLK optimization. The analysis identifies a residual oscillation floor proportional to the square of the remaining centroid offset and inversely proportional to the local beta function, demonstrating that the physically relevant objective is minimization of the final mean action after the realistic NLK kick, rather than percentage action reduction alone. This framework establishes a practical optimization strategy under realistic aperture, stability, and hardware constraints. In a representative covariance-matched ID2D case, the realistic eight-wire NLK reduces both mean horizontal action (from 3.372 μm to 0.382 μm) and finite-beam spread contribution (from 0.475 μm to 0.039 μm). Operationally, first-turn rms trajectory variations remain under 0.4 mm, and the measured trajectory response of 19.4 mm/mrad closely matches the 19.8 mm/mrad model.
Particle accelerators have become indispensable tools in fundamental charged-particle and beam-physics research, medical diagnostics and therapy, security screening, and many other applications. A small number of large, GeV-scale machines, often called “Big Science,” drive scientific discovery, while thousands of small accelerators serve everyday needs, primarily as X-ray sources when an electron beam is used. When an electron beam in the keV–MeV range strikes a high-Z (high-atomic-number) target material, it produces bremsstrahlung photons, whose interaction with matter is governed by the photoelectric effect, Compton scattering, and pair production, each dominant in a distinct energy regime that also depends on the atomic number of the absorbing material. A small accelerator can generate such significant effects if the energy and material parameters are properly matched, and these interactions can be exploited to generate material-specific signatures. Ion beams, on the other hand, deposit energy in materials and are used for gamma and neutron production, microstructure analysis, and many other applications. Here we review the operating principles of several small accelerators and their potential applications, offering a unified perspective on their role in contemporary science and technology.
The commercially available compact electron linear accelerator (LINAC) products used for high-energy imaging of dense and/or thick objects offer accelerated electron beams in an energy range from 1 MeV to 10 MeV with focal spot sizes generally from 1.0 mm to 2.0 mm on a stopping target measured at Full Width at Half Maximum (FWHM) of usually close to a Gaussian distribution profile. Reducing the focal spot used to generate Bremsstrahlung for imaging is very important, as smaller focal spots permit less penumbra for much better resolution in the produced images. Meeting such demand presents several serious challenges. Common methods for such focal spot reduction add extra elements, complexity, deliver insufficient beam power, etc., making them unsuitable for compact commercial machines. An alternative method to obtain a submillimeter electron beam focal spot FWHM of less than 0.5 mm with a “clean” Gaussian distribution using a novel RF structure design and tuning method (patent pending) is presented, used in the first 3, 6, and 9 MeV Accelerator Beam Centerlines (ABC). This invention started a New MicroBeam LINATRON™ (MBL) product line with the first MBL6 prototype LINAC, built and tested by the High Energy Systems (HES) group at Varex Imaging Corporation.
Ultrasonic Lamb waves are promising for the nondestructive evaluation of silicon wafers; however, their dispersive, multimode, and orientation-dependent propagation complicates multidirectional measurements in anisotropic media. This study presents a measurement system for wedge-free, multidirectional, A0-dominant Lamb-wave interrogation in a silicon wafer. The distinctive feature of the system is the integration of a fixed normal-incidence PZT source with non-contact scanning laser Doppler vibrometry, enabling wavefield acquisition along arbitrary in-plane directions without repeated wedge coupling or directional source reconfiguration. Frequency–wavenumber analysis demonstrates an A0-dominant wavefield, with the S0-associated power virtually indistinguishable from the baseline spectrum. A noise-adaptive Hilbert-envelope time-of-flight method and locally weighted scatterplot smoothing (LOWESS) reconstruct the orientation-dependent A0 group-velocity profile. The reconstruction shows a root-mean-square percentage deviation of 1.39% relative to the theoretical group velocities obtained from numerical simulations. This capability is practically important for wafer inspection as it reduces setup complexity, thereby improving measurement consistency.
