Laser plasma accelerators (LPAs) enable the generation of intense and short proton bunches on a micrometre scale, thus offering new experimental capabilities to research fields such as ultra-high dose rate radiobiology or material analysis. Being spectrally broadband, laser-accelerated proton bunches allow for tailored volumetric dose deposition in a sample via single bunches to excite or probe specific sample properties. The rising number of such experiments indicates a need for diagnostics providing spatially resolved characterization of dose distributions with volumes of approximately 1 cm ${}^3$ for single proton bunches to allow for fast online feedback. Here we present the scintillator-based miniSCIDOM detector for online single-bunch tomographic reconstruction of dose distributions in volumes of up to approximately 1 cm ${}^3$ . The detector achieves a spatial resolution below 500 $\unicode{x3bc}$ m and a sensitivity of 100 mGy. The detector performance is tested at a proton therapy cyclotron and an LPA proton source. The experiments’ primary focus is the characterization of the scintillator’s ionization quenching behaviour.

We present detailed characterization of laser-driven fusion and neutron production ( $\sim {10}^5$ /second) using 8 mJ, 40 fs laser pulses on a thin (<1 μm) D ${}_2$ O liquid sheet employing a measurement suite. At relativistic intensity ( $\sim 5\times {10}^{18}$ W/cm ${}^2$ ) and high repetition rate (1 kHz), the system produces deuterium–deuterium (D-D) fusion, allowing for consistent neutron generation. Evidence of D-D fusion neutron production is verified by a measurement suite with three independent detection systems: an EJ-309 organic scintillator with pulse-shape discrimination, a ${}^3\mathrm{He}$ proportional counter and a set of 36 bubble detectors. Time-of-flight analysis of the scintillator data shows the energy of the produced neutrons to be consistent with 2.45 MeV. Particle-in-cell simulations using the WarpX code support significant neutron production from D-D fusion events in the laser–target interaction region. This high-repetition-rate laser-driven neutron source could provide a low-cost, on-demand test bed for radiation hardening and imaging applications.

激光惯性约束聚变实验需要使用数十台套诊断设备从不同方位对瞬态微尺度物理过程进行诊断表征。大部分诊断设备通常需要进入巨型靶室真空环境内，在厘米到米级的不同工作距离上，对聚变靶上面毫米到数十微米的靶标进行瞄准，大部分诊断设备的瞄准精度需要达到50 μm水平。双目瞄准方法是在真空环境下实现远距离高精度瞄准的一种重要方法，但目前主要依赖人工判读图像识别靶标和手动操作诊断搭载平台运动实现对靶瞄准，特别是靶室内照明条件或诊断设备瞄准视线存在夹角等条件会严重影响靶标识别效果，对诊断设备瞄准精度造成较大影响。发展了一种基于机器视觉的诊断自动瞄准方法，采用Mask R-CNN算法并以大量模拟瞄准图进行靶标识别训练，有效解决了靶标自动判读问题，对靶标识别误差控制在8个像素点以内；同时基于实验室瞄准测试平台开展了靶标像素偏差与瞄准坐标偏离关系的离线标定，开展了算法引导下的瞄准精度测试，根据测试结果预估指向瞄准精度优于30 μm、径向瞄准精度优于50 μm，对实现诊断设备的高精度自动瞄准有一定的基础参考价值。

The target backsheath field acceleration mechanism is one of the main mechanisms of laser-driven proton acceleration (LDPA) and strongly depends on the comprehensive performance of the ultrashort ultra-intense lasers used as the driving sources. The successful use of the SG-II Peta-watt (SG-II PW) laser facility for LDPA and its applications in radiographic diagnoses have been manifested by the good performance of the SG-II PW facility. Recently, the SG-II PW laser facility has undergone extensive maintenance and a comprehensive technical upgrade in terms of the seed source, laser contrast and terminal focus. LDPA experiments were performed using the maintained SG-II PW laser beam, and the highest cutoff energy of the proton beam was obviously increased. Accordingly, a double-film target structure was used, and the maximum cutoff energy of the proton beam was up to 70 MeV. These results demonstrate that the comprehensive performance of the SG-II PW laser facility was improved significantly.

Post-acceleration of protons in helical coil targets driven by intense, ultrashort laser pulses can enhance ion energy by utilizing the transient current from the targets’ self-discharge. The acceleration length of protons can exceed a few millimeters, and the acceleration gradient is of the order of GeV/m. How to ensure the synchronization between the accelerating electric field and the protons is a crucial problem for efficient post-acceleration. In this paper, we study how the electric field mismatch induced by current dispersion affects the synchronous acceleration of protons. We propose a scheme using a two-stage helical coil to control the current dispersion. With optimized parameters, the energy gain of protons is increased by four times. Proton energy is expected to reach 45 MeV using a hundreds-of-terawatts laser, or more than 100 MeV using a petawatt laser, by controlling the current dispersion.

The interaction of relativistically intense lasers with opaque targets represents a highly non-linear, multi-dimensional parameter space. This limits the utility of sequential 1D scanning of experimental parameters for the optimization of secondary radiation, although to-date this has been the accepted methodology due to low data acquisition rates. High repetition-rate (HRR) lasers augmented by machine learning present a valuable opportunity for efficient source optimization. Here, an automated, HRR-compatible system produced high-fidelity parameter scans, revealing the influence of laser intensity on target pre-heating and proton generation. A closed-loop Bayesian optimization of maximum proton energy, through control of the laser wavefront and target position, produced proton beams with equivalent maximum energy to manually optimized laser pulses but using only 60% of the laser energy. This demonstration of automated optimization of laser-driven proton beams is a crucial step towards deeper physical insight and the construction of future radiation sources.

The acoustic pulse emitted from the Bragg peak of a laser-accelerated proton bunch focused into water has recently enabled the reconstruction of the bunch energy distribution. By adding three ultrasonic transducers and implementing a fast data analysis of the filtered raw signals, I-BEAT (Ion-Bunch Energy Acoustic Tracing) 3D now provides the mean bunch energy and absolute lateral bunch position in real-time and for individual bunches. Relative changes in energy spread and lateral bunch size can also be monitored. Our experiments at DRACO with proton bunch energies between 10 and 30 MeV reveal sub-MeV and sub-mm resolution. In addition to this 3D bunch information, the signal strength correlates also with the absolute bunch particle number.

We predict the production yield of a medical radioisotope ${}^{67}$ Cu using ${}^{67}$ Zn(n, p) ${}^{67}$ Cu and ${}^{68}$ Zn(n, pn) ${}^{67}$ Cu reactions with fast neutrons provided from laser-driven neutron sources. The neutrons were generated by the p+ ${}^9\mathrm{Be}$ and d+ ${}^9$ Be reactions with high-energy ions accelerated by laser–plasma interaction. We evaluated the yield to be (3.3 $\pm$ 0.5) $\times$ 10 ${}^5$ atoms for ${}^{67}$ Cu, corresponding to a radioactivity of 1.0 $\pm$ 0.2 Bq, for a Zn foil sample with a single laser shot. Using a simulation with this result, we estimated ${}^{67}$ Cu production with a high-frequency laser. The result suggests that it is possible to generate ${}^{67}$ Cu with a radioactivity of 270 MBq using a future laser system with a frequency of 10 Hz and 10,000-s radiation in a hospital.

激光驱动的白光光源在超高亮度、高准直性和远距离照明领域具有很大的应用潜力, 但由于蓝光激光和转换荧光在光源性质上的失配, 造成激光驱动白光光源的光均匀性差。本研究在Y₃Al₅O₁₂ : Ce³⁺(YAG)荧光玻璃薄膜(PiG)中引入不同种类的第二相, 如TiO₂、BN、Al₂O₃或SiO₂作为散射介质来调节光路, 并对第二相的掺杂浓度分别进行了优化。研究分析了掺入不同种类第二相的YAG PiG获得激光驱动白光光源的实物照明图像和散斑图像、亮度和色温的角分布情况及其光学性质。结果发现, 引入第二相大大改善了白光光源的亮度和色温均匀性, 其中具有最大相对反射率的YAG-TiO₂ PiG, 获得综合性能最佳的高均匀性白光光源, 在蓝光激光激发下, 其发光饱和阈值和光通量值达到最高, 分别为20.12 W/mm²和1056.6 lm。本研究为荧光转换材料中散射介质的选择提供了指导, 为实现高均匀性、高亮度的激光驱动白光光源奠定了基础。