Multi-beam Illumination Research Articles

Adaptive multi-beam X-ray ptychography.

Ptychography has evolved as an important method for nanoscale X-ray imaging with synchrotron radiation. Recently, it has been proposed to work with multiple beams in parallel. The main advantage of so-called multi-beam ptychography is that larger areas can be imaged much faster than with a conventional single beam scan. We introduce adaptive multi-beam ptychography performed with two Fresnel zone plates, placed one behind the other. In contrast to previous demonstrations of multi-beam ptychography, our optical scheme allows for adapting the spatial beam separation to the needs of the sample under investigation, relaxes thickness requirements on zone plates and is straightforward to implement. Moreover, it is simple to switch between single and multi-beam illumination during the same experiment. This opens the possibility of combining large and fast overview scans with detailed imaging of certain regions of interests.

Head-to-tail imaging of mice with spiral volumetric optoacoustic tomography

Optoacoustic tomography has been established as a powerful modality for preclinical imaging. However, efficient whole-body imaging coverage has not been achieved owing to the arduous requirement for continuous acoustic coupling around the animal. In this work, we introduce panoramic (3600) head-to-tail 3D imaging of mice with spiral volumetric optoacoustic tomography (SVOT). The system combines multi-beam illumination and a dedicated head holder enabling uninterrupted acoustic coupling for whole-body scans. Image fidelity is optimized with self-gated respiratory motion rejection and dual speed-of-sound reconstruction algorithms to attain spatial resolution down to 90 µm. The developed system is thus highly suitable for visualizing rapid biodynamics across scales, such as hemodynamic changes in individual organs, responses to treatments and stimuli, perfusion, total body accumulation, or clearance of molecular agents and drugs with unmatched contrast, spatial and temporal resolution.

Spatter reduction by multi-beam illumination in laser powder-bed fusion

Modulation of laser radiation is a promising approach to increase the process speed in laser powder-bed fusion. However, with an increased buildup rate, the preservation of product quality must be guaranteed. For this purpose, we investigated spatter generation with single-beam and multi-beam distributions for single tracks and printed objects. The investigation with a coaxial high-speed camera to capture thermal radiation of spatters and an off-axis high-speed camera for a qualitative observation of the melt pool led to a better understanding of spatter generation. The results showed dependency of power and scan velocity on the number of spatters. Furthermore, we showed that the application of multi-beams preserves the number of spatters per track at higher applied power. Due to the wide melt pools and fewer required hatches, the total number of spatters in a generated part was significantly reduced. In addition, by means of high-speed recordings, it was shown that melt pools with high volume have a higher stability against impurities of the powder bed and spatters. Finally, the application of multi-beam illumination led to a higher buildup rate with reduced spatter particles.

Single-sweep volumetric optoacoustic tomography of whole mice

Applicability of optoacoustic imaging in biology and medicine is determined by several key performance characteristics. In particular, an inherent trade-off exists between the acquired field-of-view (FOV) and temporal resolution of the measurements, which may hinder studies looking at rapid biodynamics at the whole-body level. Here, we report on a single-sweep volumetric optoacoustic tomography (sSVOT) system that attains whole body three-dimensional mouse scans within 1.8 s with better than 200 μm spatial resolution. sSVOT employs a spherical matrix array transducer in combination with multibeam illumination, the latter playing a critical role in maximizing the effective FOV and imaging speed performance. The system further takes advantage of the spatial response of the individual ultrasound detection elements to mitigate common image artifacts related to limited-view tomographic geometry, thus enabling rapid acquisitions without compromising image quality and contrast. We compare performance metrics to the previously reported whole-body mouse imaging implementations and alternative image compounding and reconstruction strategies. It is anticipated that sSVOT will open new venues for studying large-scale biodynamics, such as accumulation and clearance of molecular agents and drugs across multiple organs, circulation of cells, and functional responses to stimuli.

Generation and electromagnetic coherence of unpolarized three-component light fields

Conditions for controlled generation of completely unpolarized, genuine three-component random light fields, both radiating and evanescent, in multi-beam illumination at a planar dielectric interface are explored. The associated electromagnetic degrees of coherence are also analyzed. Our results reveal the possibility to tailor fields with polarization properties identical to those of universal blackbody radiation, yet with tunable spatial coherence characteristics. Such unconventional, fully unpolarized three-component electromagnetic fields, not addressable by the traditional beam-field formalism, could be exploited in surface-photonic light-matter interactions.

Single shot ptychographical iterative engine based on multi-beam illumination

An optical alignment and a corresponding reconstruction algorithm are proposed to realize a single shot Ptychographical Iterative Engine (PIE). Multiple light beams generated by a cross grating are used to illuminate the specimen, and the resulting diffraction patterns formed on the detector plane by each beam are recorded simultaneously. The modulus and phase images are properly reconstructed with standard PIE algorithm. The proposed single shot method omits the needs for a mechanical x-y scanning of standard PIE algorithm and hence dramatically reduces the data acquisition time.

Controllable optical multi-well trap and its optical lattices using compounded cosine patterns

This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam. Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns. It also discusses how to expand this multi-well trap to two-dimensional lattices with single- or multi-well trap by using an orthogonally or non-orthogonally modulated grating, as well as using incoherent multi-beam illumination, and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.

Code OK3 – An upgraded version of OK2 with beam wobbling function

For computer simulations on heavy ion beam (HIB) irradiation onto a target with an arbitrary shape and structure in heavy ion fusion (HIF), the code OK2 was developed and presented in Computer Physics Communications 161 (2004). Code OK3 is an upgrade of OK2 including an important capability of wobbling beam illumination. The wobbling beam introduces a unique possibility for a smooth mechanism of inertial fusion target implosion, so that sufficient fusion energy is released to construct a fusion reactor in future. New version program summary Program title: OK3 Catalogue identifier: ADST_v3_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADST_v3_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 221 517 No. of bytes in distributed program, including test data, etc.: 2 471 015 Distribution format: tar.gz Programming language: C++ Computer: PC (Pentium 4, 1 GHz or more recommended) Operating system: Windows or UNIX RAM: 2048 MBytes Classification: 19.7 Catalogue identifier of previous version: ADST_v2_0 Journal reference of previous version: Comput. Phys. Comm. 161 (2004) 143 Does the new version supersede the previous version?: Yes Nature of problem: In heavy ion fusion (HIF), ion cancer therapy, material processing, etc., a precise beam energy deposition is essentially important [1]. Codes OK1 and OK2 have been developed to simulate the heavy ion beam energy deposition in three-dimensional arbitrary shaped targets [2, 3]. Wobbling beam illumination is important to smooth the beam energy deposition nonuniformity in HIF, so that a uniform target implosion is realized and a sufficient fusion output energy is released. Solution method: OK3 code works on the base of OK1 and OK2 [2, 3]. The code simulates a multi-beam illumination on a target with arbitrary shape and structure, including beam wobbling function. Reasons for new version: The code OK3 is based on OK2 [3] and uses the same algorithm with some improvements, the most important one is the beam wobbling function. Summary of revisions: 1. In the code OK3, beams are subdivided on many bunches. The displacement of each bunch center from the initial beam direction is calculated. 2. Code OK3 allows the beamlet number to vary from bunch to bunch. That reduces the calculation error especially in case of very complicated mesh structure with big internal holes. 3. The target temperature rises during the time of energy deposition. 4. Some procedures are improved to perform faster. 5. The energy conservation is checked up on each step of calculation process and corrected if necessary. New procedures included in OK3 1. Procedure BeamCenterRot( ) rotates the beam axis around the impinging direction of each beam. 2. Procedure BeamletRot( ) rotates the beamlet axes that belong to each beam. 3. Procedure Rotation( ) sets the coordinates of rotated beams and beamlets in chamber and pellet systems. 4. Procedure BeamletOut( ) calculates the lost energy of ions that have not impinged on the target. 5. Procedure TargetT( ) sets the temperature of the target layer of energy deposition during the irradiation process. 6. Procedure ECL( ) checks up the energy conservation law at each step of the energy deposition process. 7. Procedure ECLt( ) performs the final check up of the energy conservation law at the end of deposition process. Modified procedures in OK3 1. Procedure InitBeam( ): This procedure initializes the beam radius and coefficients A1, A2, A3, A4 and A5 for Gauss distributed beams [2]. It is enlarged in OK3 and can set beams with radii from 1 to 20 mm. 2. Procedure kBunch( ) is modified to allow beamlet number variation from bunch to bunch during the deposition. 3. Procedure ijkSp( ) and procedure Hole( ) are modified to perform faster. 4. Procedure Espl( ) and procedure ChechE( ) are modified to increase the calculation accuracy. 5. Procedure SD( ) calculates the total relative root-mean-square (RMS) deviation and the total relative peak-to-valley (PTV) deviation in energy deposition non-uniformity. This procedure is not included in code OK2 because of its limited applications (for spherical targets only). It is taken from code OK1 and modified to perform with code OK3. Running time: The execution time depends on the pellet mesh number and the number of beams in the simulated illumination as well as on the beam characteristics (beam radius on the pellet surface, beam subdivision, projectile particle energy and so on). In almost all of the practical running tests performed, the typical running time for one beam deposition is about 30 s on a PC with a CPU of Pentium 4, 2.4 GHz.

Code OK2—A simulation code of ion-beam illumination on an arbitrary shape and structure target

For computer simulations on heavy ion beam (HIB) irradiation on a spherical fuel pellet in heavy ion fusion (HIF) the code OK1 was developed and presented in [Comput. Phys. Commun. 157 (2004) 160–172]. The new code OK2 is a modified upgraded computer program for more common purposes in research fields of medical treatment, material processing as well as HIF. OK2 provides computational capabilities of a three-dimensional ion beam energy deposition on a target with an arbitrary shape and structure. Program summary Title of program: OK2 Catalogue identifier: ADTZ Other versions of this program [1] : Title of the program: OK1 Catalogue identifier: ADST Program summary URL: http://cpc.cs.qub.as.uk/summaries/ADTZ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: PC (Pentium 4, ∼1 GHz or more recommended) Operating system: Windows or UNIX Program language used: C++ Memory required to execute with typical data: 2048 MB No. of bits in a word: 32 No. of processors used: 1CPU Has the code been vectorized or parallelized: No No. of bytes in distributed program, including test data: 17 334 No of lines in distributed program, including test date: 1487 Distribution format: tar gzip file Nature of physical problem: In research areas of HIF (Heavy Ion Beam Inertial Fusion) energy [1–4] and medical material sciences [5], ion energy deposition profiles need to be evaluated and calculated precisely. Due to a favorable energy deposition behavior of ions in matter [1–4] it is expected that ion beams would be one of preferable candidates in various fields including HIF and material processing. Especially in HIF for a successful fuel ignition and a sufficient fusion energy release, a stringent requirement is imposed on the HIB irradiation non-uniformity, which should be less than a few percent [4,6,7]. In order to meet this requirement we need to evaluate the uniformity of a realistic HIB irradiation and energy deposition pattern. The HIB irradiation and non-uniformity evaluations are sophisticated and difficult to calculate analytically. Based on our code one can numerically obtain a three-dimensional profile of energy deposition onto an arbitrary shape and structure target. Method of solution: OK2 code works on the base of OK1 [1–9]. The code simulates a multi-beam illumination on a target with arbitrary shape and structure, and obtains the 3D energy deposition profile. Restrictions on the complexity of the problem: None Typical running time: The execution time depends on the pellet mesh number and the number of beams in the simulated illumination as well as on the beam characteristics (beam radius on the pellet surface, beam subdivision, projectile particle energy and so on). In almost of the practical running tests performed, the typical running time for one beam deposition is about 40 s on a PC with a CPU of Pentium 4, 2.4 GHz. Unusual features of the program: None

31aZJ-9 Multi-beam illumination on a HIF pellet

31aZJ-9 Multi-beam illumination on a HIF pellet

A distributed radiator, heavy ion target driven by Gaussian beams in a multibeam illumination geometry

An inertial confinement fusion target driven by ion beams in a multibeam illumination geometry is presented. Two dimensional integrated LASNEX calculations (ion beam deposition to fusion burn in one computer simulation) predict a gain of greater than 65 for this target. Each beam has a Gaussian density profile and is focused to an elliptically shaped spot. Multiple beam ellipses are overlayed to form an annulus on the end of the cylindrical hohlraum. The beams enter at angles relative to the cylindrical axis of the hohlraum that are consistent with both liquid wall chamber protection and the space required for a final focusing system upstream. For an accelerator that is 25% efficient (η = 0.25), a gain G of 65 leads to ηG greater than 16; a reactor with a reasonably small recirculating power fraction requires ηG greater than 8-10.