Real-time single-proton counting with transmissive perovskite nanocrystal scintillators.

High-sensitivity radiation detectors for energetic particles are essential for advanced applications in particle physics, astronomy and cancer therapy. Current particle detectors use bulk crystals, and thin-film organic scintillators have low light yields and limited radiation tolerance. Here we present transmissive thin scintillators made from CsPbBr3 nanocrystals, designed for real-time single-proton counting. These perovskite scintillators exhibit exceptional sensitivity, with a high light yield (~100,000 photons per MeV) when subjected to proton beams. This enhanced sensitivity is attributed to radiative emission from biexcitons generated through proton-induced upconversion and impact ionization. These scintillators can detect as few as seven protons per second, a sensitivity level far below the rates encountered in clinical settings. The combination of rapid response (~336 ps) and pronounced ionostability enables diverse applications, including single-proton tracing, patterned irradiation and super-resolution proton imaging. These advancements have the potential to improve proton dosimetry in proton therapy and radiography.

Breaking the 10 nm barrier using molecular ions in nuclear microprobes.

The spatial resolution plays a crucial role in determining the performance of a nuclear microprobe. However, the formation of spatial resolutions below 10 nm remains a challenge in nuclear microprobes. Here, we propose novel technologies (near-axis scanning transmission ion microscopy and double-fragment scattering) utilizing molecular ions to address this challenge and demonstrate a H2+ molecular beam with 6.0 × 10 nm2 lateral resolution and monolayer thickness resolution respectively. Using the improved nuclear microprobe, we directly demonstrate that the ionization of a H2+ can be efficiently achieved using one single layer graphene, and also that single and few layers of freestanding graphene can be clearly differentiated and identified. The precise control of fast molecular ions at sub-10 nm scales has the potential to unlock new avenues of applications.

Quantifying nanodiamonds biodistribution in whole cells with correlative iono-nanoscopy.

Correlative imaging and quantification of intracellular nanoparticles with the underlying ultrastructure is crucial for understanding cell-nanoparticle interactions in biological research. However, correlative nanoscale imaging of whole cells still remains a daunting challenge. Here, we report a straightforward nanoscopic approach for whole-cell correlative imaging, by simultaneous ionoluminescence and ultrastructure mapping implemented with a highly focused beam of alpha particles. We demonstrate that fluorescent nanodiamonds exhibit fast, ultrabright and stable emission upon excitation by alpha particles. Thus, by using fluorescent nanodiamonds as imaging probes, our approach enables quantification and correlative localization of single nanodiamonds within a whole cell at sub-30 nm resolution. As an application example, we show that our approach, together with Monte Carlo simulations and radiobiological experiments, can be employed to provide unique insights into the mechanisms of nanodiamond radiosensitization at the single whole-cell level. These findings may benefit clinical studies of radio-enhancement effects by nanoparticles in charged-particle cancer therapy.

FANM: A software for focus and aberrations of nuclear microprobe.

Focus and Aberrations of Nuclear Microprobe (FANM) is a new beam optics package to achieve fast and accurate design of a nuclear microprobe. FANM achieves a balance between speed of focusing and accuracy of high order aberrations. A combined method proposed in FANM is to achieve focusing conditions using a matrix method and to calculate aberration coefficients using a numerical ray tracing method. FANM has two optional optimization algorithms (derivative-free method and particle swarm optimization), offering a powerful choice for multi-variable optimization. Numeric variables in FANM are stored as 64-bit (8-byte) double-precision floating-point values to reduce calculation errors. Results obtained with FANM are compared with six existing computational tools (PRAM, TRANSPORT-PSI, TRANSPORT-PBO, WinTRAX, GEANT4-nanobeam and Zgoubi). The reasons for discrepancies between the different packages are discussed. Calculated currents of magnetic quadrupole lenses obtained with FANM are compared with experimental values of a nuclear microprobe in the National University of Singapore.

Considerations for the nano aperture ion source: Geometrical design and electrical control.

A new type of ion source is being developed for proton beam writing and other focused ion beam applications. The potential of this source as well as achieved performance of the nano aperture ion source will be evaluated. Based on the ideal source parameters, critical geometrical parameters constraining chromatic aberrations and a possible pathway to achieve this performance will be presented. Finally, an electronic control system to minimize chromatic and spherical aberrations to an acceptable level will be demonstrated.

GEANT4 models for the secondary radiation flux in the collimation system of a 300MeV proton microbeam.

In Harbin, we are developing a 300MeV proton microbeam for many applications in space science including upset studies in microelectronic devices, radiation hardness of materials for satellites and radiation effects in human tissues. There are also applications of this facility proposed for proton therapy. The microbeam system will employ a purpose-built proton synchrotron to provide the beam. However there are many challenges to be addressed in the design, construction and operation of this facility. Here we address two important design aspects for which we apply GEANT4 modeling. First, the high energy proton beam interacts strongly with beam line materials, especially the collimation slits, to produce showers of secondary particles which could introduce significant background signals and degrade the resolution of the proton microbeam. Second, the beam transport within the residual vacuum of the beam line may also introduce undesirable background radiation. In both cases mitigation strategies need to be incorporated during the design phase of the new system. We study the use of a dipole magnet following the aperture collimator to reduce the flux of secondary particles incident on the analysis chamber. Monte Carlo simulations are performed using GEANT4 and SRIM. By inserting the dipole magnet, we find as expected a significant reduction in the scattering of protons and other particles, such as neutrons and gamma rays, at the collimation system exit position. Secondary radiation from the residual gas pressure within the beam line vacuum system are also modelled and found to be negligible under the standard operating conditions.