Multi-particle Tracking Research Articles

The study and design of a deuteron drift tube linear accelerator for middle energy neutron source

The paper concerns a room-temperature cross-bar H-mode (CH) drift tube linac (DTL) with KONUS (Kombinierte Null Grad Struktur) [1,2] beam dynamics. To make the acceleration in DTL cell more efficient, we studied the correlation between transit time factor (TTF) and structural coefficients, first. Furthermore, we developed a new code with Python to demonstrate the longitudinal dynamics more clearly. The code computationally generates clusters, bunch centers, and emittance growth in a single figure. Thus, the stabilization region and cluster evolution at various negative phases can be studied. Based on the above studies, we designed a 162.5 MHz CH-DTL to accelerate 10 mA D+ from 2.11 MeV to 3.25 MeV in continuous-wave (CW) mode. The proposed CH-DTL is a part of the Middle Energy Neutron Source (MENS). The dynamics and RF design were iterated to make the gap voltage error lower than 1 %. The initial beam is assumed to come from a Radio Frequency Quadrupole accelerator (RFQ). The geometries of the CH-DTL are optimized by using CST. Multiparticle tracking from LEBT to RFQ is performed with TraceWin and the transmission efficiency in the CH-DTL is 100 %.

Multi-Particle Tracking in Complex Plasmas Using a Simplified and Compact U-Net.

Detecting micron-sized particles is an essential task for the analysis of complex plasmas because a large part of the analysis is based on the initially detected positions of the particles. Accordingly, high accuracy in particle detection is desirable. Previous studies have shown that machine learning algorithms have made great progress and outperformed classical approaches. This work presents an approach for tracking micron-sized particles in a dense cloud of particles in a dusty plasma at Plasmakristall-Experiment 4 using a U-Net. The U-net is a convolutional network architecture for the fast and precise segmentation of images that was developed at the Computer Science Department of the University of Freiburg. The U-Net architecture, with its intricate design and skip connections, has been a powerhouse in achieving precise object delineation. However, as experiments are to be conducted in resource-constrained environments, such as parabolic flights, preferably with real-time applications, there is growing interest in exploring less complex U-net architectures that balance efficiency and effectiveness. We compare the full-size neural network, three optimized neural networks, the well-known StarDist and trackpy, in terms of accuracy in artificial data analysis. Finally, we determine which of the compact U-net architectures provides the best balance between efficiency and effectiveness. We also apply the full-size neural network and the the most effective compact network to the data of the PK-4 experiment. The experimental data were generated under laboratory conditions.

Scaling law of correlated diffusion of colloidal particles confined to a rugged surface

Using optical microscopy and multiparticle tracking techniques, we investigate the correlated diffusion of colloidal particles over a rugged surface. Our findings demonstrate that the correlated diffusion caused by the hydrodynamic interactions of particles confined to energy landscapes displays a distinctive power-law behavior. The local energy landscape on the rugged surface reduces the long-range hydrodynamic interactions between colloidal particles. The energy landscape influences the strength of hydrodynamic interactions, but not their power-law form. The responding factor of the colloidal particles over the energy landscape to hydrodynamics decays exponentially with the potential energy minimum. We propose a scaling method, with which the correlated diffusion of colloidal particles over various energy landscapes can be scaled onto a master curve. The master curve characterizes the response of the particles over the energy landscape to the hydrodynamics. The scale factors used for the master curve allow for the calculation of the energy landscape. The findings provide physical insights into the confinement hydrodynamics and would be helpful for designing material surfaces and controlling the motion of particles on rough surfaces.

Differentiable self-consistent space-charge simulation for accelerator design

The nonlinear space-charge effects in a high intensity or high brightness accelerator can have a significant impact on the beam properties through the accelerator. These effects are included in the accelerator design via self-consistent multi-particle tracking simulations. In order to study the sensitivity of the final beam's properties with respect to the accelerator design parameters, one has to carry out the time-consuming space-charge simulation multiple times. In this paper, we propose a differentiable self-consistent space-charge simulation model that enables the study of the beam sensitivity through only one simulation. Such a model can also be used with gradient-based numerical optimizers for accelerator design optimizations including the self-consistent space-charge effects.

Multi-particle tracking in crowded environments.

Super-resolved localization by fluorescence (such as PALM and STORM) is used to probe static molecular structures below the diffraction limit. Super-resolved localization trades temporal resolution for high spatial resolution, limiting its use for dynamic structures. What is more, approximately localizing static structures across frames necessarily leads to aliasing artifacts, which are known to compromise our ability to achieve single-particle tracking (SPT). The situation is further exacerbated by having molecules transiently overlap in their point spread functions across frames.

Equilibrium electron beam parameters of the High Energy Photon Source

PurposeThe physics design of the High Energy Photon Source (HEPS) was finished after many times of iteration. Hereby, the typical equilibrium electron beam parameters corresponding to the proposed two baseline operation modes in the baseline design of HEPS are presented.MethodsTo compute the equilibrium parameters of the electron beam, the lattice parameters, RF parameters, and the parameters of the insertion devices (IDs) were determined first. Furthermore, it is more precise to use the full-current electron beam parameters in the estimations of the performance of the synchrotron light. Therefore, not only the single-particle dynamics but also the current-dependent collective effects need to be considered in the computations of the full-current, equilibrium parameters of the electron beam. Both analytic computations and multi-particle tracking simulations were carried out.ResultsThe full-current, equilibrium parameters of the electron beams in the HEPS storage ring are presented in this paper. Moreover, the main beam parameters in the injector (the booster and the LINAC), corresponding to the two baseline operation modes of the storage ring, are also presented.ConclusionThe typical electron beam parameters corresponding to the two baseline operation modes are given in detail in this paper.

Magnetically Driven Muco-Inert Janus Nanovehicles for Enhanced Mucus Penetration and Cellular Uptake.

One of the main challenges of transmucosal drug delivery is that of enabling particles and molecules to move across the mucosal barrier of the mucosal epithelial surface. Inspired by nanovehicles and mucus-penetrating nanoparticles, a magnetically driven, mucus-inert Janus-type nanovehicle (Janus-MMSN-pCB) was fabricated by coating the zwitterionic polymer poly(carboxybetaine methacrylate) (pCB) on the mesoporous silica nanorod, which was grown on one side of superparamagnetic Fe3O4 nanoparticle using the sol-gel method. X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and Fourier infrared spectroscopy were used to characterize the structure and morphology of the nanovehicles, proving the success of each synthesis step. The in vitro cell viability assessment of these composites using Calu-3 cell lines indicates that the nanovehicles are biocompatible in nature. Furthermore, the multiparticle tracking, Transwell® system, and cell imaging experimental results demonstrate that both the modification of pCB and the application of a magnetic field effectively accelerated the diffusion of the nanovehicles in the mucus and improved the endocytosis through Calu-3. The favorable cell uptake performance of Janus-MMSN-pCB in mucus systems with/without magnetic driving proves its potential role in the diagnosis, treatment, and imaging of mucosal-related diseases.

Imaging of the microstructure of Carbopol dispersions and correlation with their macroelasticity: A micro- and macrorheological study

We developed a new data analysis strategy, the so-called micro-rheo-mapping technique, based on multiparticle tracking experiments to obtain an accurate and direct visualization of the microstructure of commercial acrylate thickeners of Carbopol-type with high (Ultrez 10), intermediate (ETD 2020), and low (ETD 2050) degree of crosslinking. At low polymer concentration, aggregates made of several primary Carbopol particles are formed with an average diameter of 43 ± 11, 56 ± 14, and 10 ± 2.5 μm for Ultrez 10, ETD 2020, and ETD 2050, respectively. For ETD 2050, the least crosslinked thickener, the shell of dangling polymer chains covering the aggregate surface is thicker than for ETD 2020 and Ultrez 10. At technically relevant polymer concentrations, our results indicate, for all three thickeners, that the microstructure is highly heterogeneous with regions of different crosslink densities. One region inaccessible for tracer particles corresponding to a mixture of polydisperse aggregates and individual primary particles with a core mesh size less than 200 nm and a second, diluted enough to be accessible and which exhibits both elastic and viscous characteristics. The study of the impact of pH, polymer concentration, and crosslink density on these local structural and viscoelastic heterogeneities as well as macrorheological properties allowed us to establish a correlation between microstructure and macroelasticity. In particular, we found that the bulk shear modulus strongly depends on the fraction of inaccessible areas, making this microscopic parameter most relevant for describing the macroelasticity of Carbopol gels, whereas the local elasticity of the interstitial regions is of minor importance.

Vlasov description of the beam response to noise in the presence of wakefields in high-energy synchrotrons: beam transfer function, diffusion, and loss of Landau damping

Noise can have severe impacts on particle beams in high-energy synchrotrons. In particular, it has recently been discovered that noise combined with wakefields can cause a diffusion that leads to a loss of Landau damping after a latency. Such instabilities have been observed in the Large Hadron Collider. This paper, therefore, studies the beam response to noise in the presence of wakefields, within the framework of the Vlasov equation. First, a wakefield beam eigenmode transfer function (MTF) is derived, quantifying the amplitude of a wakefield eigenmode when excited by noise. Then, the MTFs of all the wakefield eigenmodes are combined to derive the beam transfer function (BTF) including the impact of wakefields. It is found to agree excellently with multi-particle tracking simulations. Finally, the MTFs are also used to derive the single-particle diffusion driven by the wakefield eigenmodes. This new Vlasov-based theory for the diffusion driven by noise-excited wakefields is found to be superior to an existing theory by comparing to multi-particle tracking simulations. Through sophisticated simulations that self-consistently model the evolution of the distribution and the stability diagram, the diffusion is found to lead to a loss of Landau damping after a latency. The most important technique to extend the latency and thereby mitigate these instabilities is to operate the synchrotron with a stability margin in detuning strength relative to the amount of detuning required to barely stabilize the beam with its initial distribution.

Four-dimensional multi-particle tracking in living cells based on lifetime imaging

Abstract Research on dynamic events in living cells, such as intracellular transportation, is important for understanding cell functions. As movements occur within cells, the microenvironment of the moving vesicles or biomacromolecules may affect the behavior of them. Herein, we propose a method of simultaneously monitoring changes in spatial positions and the local environment related to the fluorescence lifetime, i.e., four-dimensional (4D) multi-particle parallel-tracking in living cells. Based on double-helix point spread function (DH-PSF) microscopy and streak camera, the method combines three-dimensional (3D) localization methods and fluorescence lifetime imaging. By modifying the PSF of the system, the 3D positions and fluorescence lifetime information for several molecules within a depth of a few microns can be acquired simultaneously from a single snapshot. The feasibility of this method is verified by simulating the real-time tracking of a single particle with a given trajectory. In addition, a proof-of-concept 4D tracking system based on the DH-PSF and streak camera was built. The experimental results show that the 3D localization and lifetime precision are σ(x, y, z) = (26 nm, 35 nm, 53 nm) and σ(τ) = 103 ps, respectively, and the effective depth of field is approximately 4 μm. Finally, intracellular endocytosis in a living cell was observed using the system, which demonstrated the successful 4D tracking of two microspheres moving within an axial depth of 4 μm. This work opens a new perspective for research of dynamic processes, by providing information about the chemical (microenvironments) and physical (positions) changes of moving targets in living cells.

Large deformation adhesion study of polymetric hydrogel under different stimuli

Hydrogels possess excellent and interesting properties that may be harnessed for future applications, especially in soft machines. However, this is not achievable if the adhesion theory of hydrogel is not well understood. This paper aims to develop an adhesion theory of hydrogels based on the Maugis model and large deformation theory. By applying the proposed theory, we predict the mechanical behaviour during the debonding process for both polymeric networks and swollen hydrogels. Furthermore, the proposed adhesion theory is extended to temperature-sensitive hydrogels, salt concentration sensitive gels, and pH-sensitive gels. Extensive parametric studies are carried out to demonstrate the effect of several key parameters which influence the response of hydrogels subjected to different stimuli. We find that different stimuli, such as a change in the temperature, the pH, can be reflected in the debonding process. Finally, by applying a network simulation method and multi particle tracking method, simulation and experiments are conducted to verify the proposed theory. The theoretical prediction matches reasonably well with the simulation and experimental results.

Enforced stripping of negative muons from $\mu$He+ ions to stimulate muon-catalyzed fusion by cyclotron resonance acceleration

Abstract The addition (sticking) of a negative muon to an $\alpha$ particle to form a $\mu$He$^+$ ion limits the number of chain reactions in muon-catalyzed fusion (MuCF), making scientific break-even in MuCF difficult. The reduction in the sticking probability by boosting the negative muon stripping using resonance radio-frequency (RF) acceleration of $\mu$He$^+$ ions has been examined with multi-particle tracking simulations. It was found that the stripping efficiency was largely depressed by ion–electron capture processes that have not been considered so far. Improvement of the fusion chain cycles is rather difficult with an RF electric field strength of 50 MV m$^{-1}$ even at a small deuterium/tritium (D/T) gas pressure of approximately 5 atm. However, in the scheme of using spatially localized D/T mixture gas streams, the sticking probability could be reduced almost tenfold even at a large gas density of 100 atm with a modest RF field strength of less than 50 MV m$^{-1}$.

Ion-optical design and multiparticle tracking in 3D magnetic field of the gas-filled recoil separator SHANS2 at CAFE2

The CAFE2 (China Accelerator Facility for superheavy Elements) is a new facility constructed at IMP-CAS (Institute of Modern Physics, Chinese Academy of Sciences). It is based on the upgrade of a superconducting linear accelerator. A new gas-filled recoil separator SHANS2 (Spectrometer for Heavy Atoms and Nuclear Structure-2) with a total flight length path of 5.85 m at the CAFE2 is designed to synthesize and study the superheavy elements, including their physical and chemical properties. The maximum acceptable divergence angles of the SHANS2 are ±70 mrad and ±113 mrad in horizontal and vertical directions, respectively, and the maximum magnetic rigidity is 2.5 Tm. The ion-optical design and simulation are investigated in detail, including the first and the fifth order beam optics. The magnets design and magnetic field calculation are presented. Using the 3D field maps, a multiparticle tracking study is carried out for the design validation, trajectory analysis, and performance evaluation.

Longitudinal equilibrium density distribution of arbitrary filled bunches in presence of a passive harmonic cavity and the short range wakefield

We propose a novel scheme for the calculation of bunch profiles and synchronous phase shifts for arbitrary fill patterns in electron storage rings considering both the effects of the passive harmonic cavity and the short range wakefield. This scheme treats the bunch as a charge distribution rather than a point charge with a bunch form factor, and divides the voltage induced in the cavity into two groups: that induced by the previous passages and that by the present passage, where the latter is integrated with the short range wakefield from all the other vacuum components. An iteration loop for computing the bunch profiles, including a subloop using Newton iteration for calculating the synchronous phase deviations, is built and implemented into a matlab-based code. Using this code, we study the bunch lengthening and centroid transient effects for several possible fill patterns in the Hefei Advanced Light Facility storage ring under design. We find the method is very efficient, and the CPU time for the whole calculation on a regular personal computer is less than 30 seconds for each case even with more than 700 bunches. Using the case of a long gap fill as a benchmark example, both the results given by our code and the multiparticle tracking simulation with elegant are in very good agreement.

Dynamical heterogeneity in the gelation process of a polymer solution with a lower critical solution temperature.

The gelation of a hydrophobically modified hyaluronic acid aqueous solution which shows a lower critical solution temperature of about 25 °C was investigated by multi-particle tracking microrheology. The linear viscoelasticity of the gelling system is converted from the microrheological data. The critical gelling temperature Tgel = 36.3 °C was determined from the loss tangent by the Winter-Chambon criterion. The critical exponent n = 0.62 was determined from the shift factors of the time-cure superposition. The length scales of the dynamic heterogeneity of the gelling system were analyzed using a proposed framework where single-particle and multi-particle non-Gaussian parameters were compared. The length scale of the dynamic heterogeneous regions monotonically decreases during the gelation process, consistent with the nucleation-and-growth mechanism of phase separation. Distributions of local viscosity in the gelling system were extracted from the observed distributions of particle displacement as a time-dependent fingerprint of the dynamic heterogeneity of the gelling system. The results and analyzing methods proposed in the present work can be applied to other microrheological studies.

Experimental Transverse Beam Emittance Measurement Using Solenoid Magnet Strength Variation in AB-BNCT

Boron neutron capture therapy (BNCT) is a more efficient cancer treatment method compared to direct radiation therapy using charged particles such as protons or carbon beams. Particularly, accelerator-based BNCT (AB-BNCT) is attracting attention due to easy construction in a hospital. The Korea Institute of Radiological & Medical Sciences (KIRAMS) has constructed an injection system for an electrostatic AB-BNCT accelerator and commissioned 30 keV H− and 5 keV D− ion beam facilities. The beam characteristic parameters and Twiss parameters should be confirmed experimentally, and various methods have to be applied for the related measurements. In this study, the linear matrix formalism is used as a technique to measure the beam characteristic and Twiss parameters by varying the magnetic field strength of a solenoid in the beam line. To confirm the validity of this method, a multi-particle tracking code was executed. The simulation results confirm that the proposed method is effective for extracting Twiss parameters. After verification via the multi-particle tracking code, the method was applied to perform experimental measurements. Notably, the method accurately obtains the transverse beam emittance within reasonable uncertainty levels. Thus, our results show that the proposed method is a convenient technique for extracting the Twiss parameters indirectly. The results of the Twiss parameter measurement can potentially be more precise if other aspects, such as the quadrupole magnetic field strength, are incorporated.

Radial Matching Section of RFQ revisited

Radial Matching Section (RMS) which is the crucial part of Radio Frequency Quadru\\-pole (RFQ) Linac matches a stationary input beam to the time-varying focusing of RFQ. In this paper, the theory of RMS has been examined comprehensively from the point of view of the continuity of the potential function and the electric field. A methodology has been developed to include higher order term in the RMS potential function and an improved form of the focusing profile is derived which is also verified by a multi-particle tracking code. The continuity of various focusing and vane profiles for ideal RMS is also determined.

Beam loading effects and microwave instability in the booster ring of a high intensity heavy-ion accelerator facility

Transient beam loading effects and microwave instability are very important in ion synchrotrons. A simulation code longitudinal particle tracking code (LPTC) based on multiparticle tracking is developed to simulate the beam loading effects and the longitudinal beam instabilities in the booster ring (BRing) of the High Intensity heavy-ion Accelerator Facility (HIAF). A process of beam capture, acceleration, debunching, and the second capture is simulated with a reference ion beam of ${^{78}\mathrm{Kr}}^{19+}$. The simulation results show that the beam loading effects have major contribution to the beam behavior during the debunching stage and the second capture stage. A feed-forward system is suggested to compensate the beam loading effects, and the main parameters of the feed-forward system are given. The microwave instability of coasting ${^{78}\mathrm{Kr}}^{19+}$ beams is observed from the simulation results. The threshold of the microwave instability is also given. The development of self-bunching and methods to suppress the microwave instability in the BRing are discussed.

Numerical Analysis of Relaxation Process with Fast Particle Generation in Malmberg-Penning Trap Experiment for Ion Beam Inertial Fusion

To clarify a regeneration process of fast electrons in a Malmberg-Penning trap device, a numerical simulation was carried out using a multi-particle tracking code. The numerical simulations reproduced the fast particle regeneration by the rapid relaxation process observed in the experiment. In comparison with the experimental and the numerical results, it was considered that the rapid relaxation process was caused by the Coulomb interaction between the electrons.

Gelation of fish gelatin studied by multi-particle tracking method

Gelatin from various sources are extensively used as food hydrocolloids. Recently, fish gelatin has attracted special attention because of religious or medical reasons. Most food gels show structural inhomogeneity that may affect their texture and flavor release, although gelatin gels appear transparent and homogeneous. In this study, the local dynamics at the micron scale of the fish gelatin were investigated by using a multiple particle tracking method. The slow gelation of the fish gelatin compared to mammalian gelatin enabled us to study the gelation process in detail. The dynamics of microspheres embedded in the gelatin revealed the transition of gelatin from a homogeneous fluid to an elastic gel that is rheologically inhomogeneous at the micron scale.