High Duty Factor Research Articles

Mind to move: Differences in running biomechanics between sensing and intuition shod runners.

Delving into the complexities of embodied cognition unveils the intertwined influence of mind, body, and environment. The connection of physical activity with cognition sparks a hypothesis linking motion and personality traits. Hence, this study explored whether personality traits could be linked to biomechanical variables characterizing running forms. To do so, 80 runners completed three randomized 50-m running-trials at 3.3, 4.2, and 5m/s during which their running biomechanics [ground contact time (tc), flight time (tf), duty factor (DF), step frequency (SF), leg stiffness (kleg), maximal vertical ground reaction force (Fmax), and maximal leg compression of the spring during stance (ΔL)] was evaluated. In addition, participants' personality traits were assessed through the Myers-Briggs Type Indicator (MBTI) test. The MBTI classifies personality traits into one of two possible categories along four axes: extraversion-introversion; sensing-intuition; thinking-feeling; and judging-perceiving. This exploratory study offers compelling evidence that personality traits, specifically sensing and intuition, are associated with distinct running biomechanics. Individuals classified as sensing demonstrated a more grounded running style characterized by prolonged tc, shorter tf, higher DF, and greater ΔL compared to intuition individuals (p≤0.02). Conversely, intuition runners exhibited a more dynamic and elastic running style with a shorter tc and higher kleg than their sensing counterparts (p≤0.02). Post-hoc tests revealed a significant difference in tc between intuition and sensing runners at all speeds (p≤0.02). According to the definition of each category provided by the MBTI, sensing individuals tend to focus on concrete facts and physical realities while intuition individuals emphasize abstract concepts and patterns of information. These results suggest that runners with sensing and intuition personality traits differ in their ability to use their lower limb structures as springs. Intuition runners appeared to rely more in the stretch-shortening cycle to energetically optimize their running style while sensing runners seemed to optimize running economy by promoting more forward progression than vertical oscillations. This study underscores the intriguing interplay between personality traits of individuals and their preferred movement patterns.

What does climbing mean exactly? Assessing spatiotemporal gait characteristics of inclined locomotion in parrots.

At what inclination does climbing begin? In this paper, we investigate the transition from walking to climbing in two species of parrot (Agapornis roseicollis and Nymphicus hollandicus) that are known to incorporate both their tail and their craniocervical system into the gait cycle during vertical climbing. Locomotor behaviors ranging in inclination were observed at angles between 0° and 90° for A. roseicollis, and 45°-85° degrees for N. hollandicus. Use of the tail in both species was observed at 45° inclination, and was joined at higher inclinations (> 65°) by use of the craniocervical system. Additionally, as inclination approached (but remained below) 90°, locomotor speeds were reduced while gaits were characterized by higher duty factors and lower stride frequency. These gait changes are consistent with those thought to increase stability. At 90°, A. roseicollis significantly increased its stride length, resulting in higher overall locomotor speed. Collectively these data demonstrate that the transition between horizontal walking and vertical climbing is gradual, incrementally altering several components of gait as inclinations increase. Such data underscore the need for further investigation into how exactly "climbing" is defined and the specific locomotor characteristics that differentiate this behavior from levelwalking.

Evaluating The Precocial-altricial Axis of Motor Skill at Birth in A Preterm Pig Model.

The pace of locomotor development is a critical component of lifetime evolutionary fitness. Developmental researchers often divide species into two broad categories based on functional competence at birth: precocial infants who can independently stand and locomote soon after birth versus altricial infants who are either incapable of independent movement or can only do so in a rudimentary manner. However, investigating the lower level neuromotor and biomechanical traits that account for perinatal variation in motor development is complicated by the lack of experimental control inherent to all comparative analyses. Precocial and altricial animals often differ along a host of dimensions that can obfuscate the specific factors controlling motor development per se. Here, we propose an alternative approach of examining locomotor development in a nominally precocial species-the domestic pig (Sus scrofa)-in which gestation length has been experimentally manipulated, thereby creating "functionally altricial" cohorts for comparison. We have used standard biomechanical testing to evaluate balance and locomotor performance in preterm pigs born at 94% full-term gestation (N=29 individuals) and compared these data to a similar dataset on age-matched full-term piglets (N=15 individuals). Static balance tests showed that preterm pigs were characterized by increased postural sway, particularly in the fore-aft (anteroposterior) direction. Locomotor analyses showed that preterm piglets tended to take shorter, more frequent strides, use higher duty factors, and preferentially choose gait patterns that ensured they were supported by at least three limbs during most of the stride cycle, though differences between preterm and full-term animals were often modulated by variation in locomotor speed. Morphometric analysis showed no differences in relative extensor muscle mass between preterm and full-term animals, suggesting that neurological immaturity might be more determinant of preterm piglet motor dysfunctions than musculoskeletal immaturity per se (though much work remains to be done to fully document the neuromotor phenotype of the preterm infant pig model). In many ways, the postural and locomotor deficits shown by the preterm piglets paralleled the locomotor phenotype of altricial mammals. Overall, our study demonstrates the utility of a "within-species" design for studying the biomechanical correlates and neuromotor basis of evolutionary variation in motor skill at birth.

Grizzlies and gazelles: Duty factor is an effective measure for categorizing running style in English Premier League soccer players.

English Premier League soccer players run at multiple speeds throughout a game. The aim of this study was to assess how well the duty factor, a dimensionless ratio based on temporal variables, described running styles in professional soccer players. A total of 25 players ran on an instrumented treadmill at 12, 16, and 20 km/h. Spatiotemporal and ground reaction force data were recorded for 30 s at each speed; video data (500 Hz) were collected to determine footstrike patterns. In addition to correlation analysis amongst the 25 players, two groups (both N = 9) of high and low duty factors were compared. The duty factor was negatively correlated with peak vertical force, center of mass (CM) vertical displacement, and leg stiffness (kleg) at all speeds (r ≥ −0.51, p ≤ 0.009). The low duty factor group had shorter contact times, longer flight times, higher peak vertical forces, greater CM vertical displacement, and higher kleg (p < 0.01). Among the high DF group players, eight were rearfoot strikers at all speeds, compared with three in the low group. The duty factor is an effective measure for categorizing soccer players as being on a continuum from terrestrial (high duty factor) to aerial (low duty factor) running styles, which we metaphorically refer to as “grizzlies” and “gazelles,” respectively. Because the duty factor distinguishes running style, there are implications for the training regimens of grizzlies and gazelles in soccer, and exercises to improve performance should be developed based on the biomechanical advantages of each spontaneous running style.

Duty factor and foot-strike pattern do not represent similar running pattern at the individual level

Runners were classified using their duty factor (DF) and using their foot-strike pattern (FSP; rearfoot, midfoot, or forefoot strikers), determined from their foot-strike angle (FSA). High and low DF runners showed different FSPs but DF was assumed to not only reflect what happens at initial contact with the ground (more global than FSP/FSA). Hence, FSP and DF groups should not necessarily be constituted by the same runners. However, the relation between FSP and DF groups has never been investigated, leading to the aim of this study. One hundred runners ran at 9, 11, and 13 km/h. Force data (1000 Hz) and whole-body kinematics (200 Hz) were acquired by an instrumented treadmill and optoelectronic system and were used to classify runners according to their FSA and DF. Weak correlations were obtained between FSA and DF values and a sensitivity of 50% was reported between FSP and DF groups, i.e., only one in two runners was attributed to the DF group supposedly corresponding to the FSP group. Therefore, ‘local’ FSP/FSA and DF do not represent similar running pattern information when investigated at the individual level and DF should be preferred to FSP/FSA when evaluating the global running pattern of a runner.

Prospects for Disruption Handling in a Tokamak-Based Fusion Reactor

Disruptions present a great challenge to achieving an economically viable commercial tokamak fusion reactor. Disruption handling, including prevention, mitigation, and resilient design, must be incorporated into future reactor designs at the same priority as core performance and steady-state heat flux removal. Prevention requires avoiding unstable regimes; actively stabilizing instabilities if they do appear; or, if those steps should fail, terminating the plasma-controlled rampdown. Mitigation is a last resort that utilizes massive impurity injection to reduce a damaging concentration of thermal and mechanical loads. Extremely robust disruption prevention will be of paramount importance to ensure high duty factor and capital return on the reactor investment, but the reactor environment poses significant technical challenges exceeding those in ITER. The long-term mission of a commercial reactor motivates investment in passive resilient design to survive disruptions in the absence of active intervention.

Comparative forelimb kinematics of the “pygmy” chameleon Brookesia superciliaris

Understanding the locomotor characteristics of early diverging “pygmy” or “leaf” chameleons can help to explain how their unique morphology is adapted to fit their environment and mode of life. However, nearly all quantitative studies of chameleon locomotion thus far have focused on the larger, highly arboreal “true” chameleons. Unlike “true chameleons, “pygmy” chameleons spend most of their time on the ground and are considered terrestrial. We investigated forearm kinematics in the Brown Leaf Chameleon Brookesia superciliaris to quantify and compare the locomotor characteristics of B. superciliaris relative to “true” chameleons such as Trioceros and Bradypodion. We predicted that elbow joint angles would be smaller in B. superciliaris, corresponding to a less upright posture, and that wrist range of motion would be more limited because of their simplified wrist structure. Kinematic data were collected from B. superciliaris and Trioceros jacksonii, a three horned chameleon native to east Africa. Markers were painted on the skin, and locomotion was recorded using four high speed cameras at 120 Hz while the chameleons traversed a horizontal dowel. Five events (recordings) for B. superciliaris and one event for T. jacksonii were analyzed. Markers on the elbow, forearm, wrist, and manual digits were tracked throughout one stride in each event. Outcome measures were range of motion at the wrist, elbow angle, and footfall patterns. Elbow joint angles in B. superciliaris at mid-stance and touch-down were similar to values reported in the literature forBradypodion pumilim, a larger arboreal chameleon found in parts of south Africa. The elbow joint angle of B. superciliaris at lift off was smaller when compared to B. pumilim. T. jacksonii had a much smaller elbow range of motion than B. superciliaris and B. pumilim. Wrist range of motion was similar between B. superciliaris and T. jacksonii. B. superciliaris used a lateral sequence walk with a lower step frequency and higher duty factor than T. jacksonii, which used a walking trot. Our results do not support the hypothesis that “pygmy” chameleons have more restricted ranges of motion at the wrist than “true” chameleons, but they indicate that the elbow is slightly more flexed and has a smaller range of motion. However, the greatest difference between the two groups was that B. superciliaris moved much more slowly and kept at least three feet in contact with the substrate, trading speed for increased stability. Thus, the transition to a fully arboreal way of life in “true” chameleons may have involved changes in limb kinematics as well as morphology.

One hundred marathons in 100 days: Unique biomechanical signature and the evolution of force characteristics and bone density

BackgroundAn extraordinary long-term running performance may benefit from low dynamic loads and a high load-bearing tolerance. An extraordinary runner (age = 55 years, height = 1.81 m, mass = 92 kg) scheduled a marathon a day for 100 consecutive days. His running biomechanics and bone density were investigated to better understand successful long-term running in the master athlete. MethodsOverground running gait analysis and bone densitometry were conducted before the marathon-a-day challenge and near its completion. The case's running biomechanics were compared pre-challenge to 31 runners who were matched by a similar foot strike pattern. ResultsThe case's peak vertical loading rate (Δx̄ = –61.9 body weight (BW)/s or –57%), peak vertical ground reaction force (Δx̄ = –0.38 BW or –15%), and peak braking force (Δx̄ = –0.118 BW or –31%) were remarkably lower (p < 0.05) than the control group at ∼3.3 m/s. The relatively low loading-related magnitudes were attributed to a remarkably high duty factor (0.41) at the evaluated speed. The foot strike angle of the marathoner (29.5°) was greater than that of the control group, affecting the peak vertical loading rate. Muscle powers in the lower extremity were also remarkably low in the case vs. controls: peak power of knee absorption (Δx̄ = –9.16 watt/kg or –48%) and ankle generation (Δx̄ = –3.17 watt/kg or –30%). The bone mineral density increased to 1.245 g/cm² (+2.98%) near completion of the challenge, whereas the force characteristics showed no statistically significant change. ConclusionThe remarkable pattern of the high-mileage runner may be useful in developing or evaluating load-shifting strategies in distance running.

Relationship between duty factor and external forces in slow recreational runners

ObjectivesRecreational runners show a large interindividual variation in spatiotemporal characteristics. This research focused on slow runners and intended: (1) to document the variance in duty factor (DF) between runners in...

LINAC developments for heavy ion operation at GSI and FAIR

The first cavity of a standalone superconducting (sc) continuous wave (cw) heavy ion Linac as a demonstration of the capability of 217 MHz multi gap Crossbar H-mode structures (CH) has been already commissioned at high acceleration gain. The worldwide first beam test with a superconducting multi gap CH-cavity was a milestone of the R&D work of HIM and GSI in collaboration with Goethe University Frankfurt (GUF) in preparation of the sc cw heavy ion Linac project, substituting GSI-UNILAC as a heavy ion high duty factor Linac. Recently the first two of four fully equipped cw-Linac cryomodules are in procurement. To meet the future FAIR science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. In the last years ion source developments, in particular for the high current Vacuum Arc Ion Sources (VARIS), were concentrated on heavy elements, as Bi and Pb, aiming for stable routine ion source operation at a sufficient rep. rate and high production efficiency. Stripping is a key technology for all heavy ion accelerators. After upgrade of the supersonic N2-gas jet implementation of high current foil stripping, recently a new H2gas cell, using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An enhanced stripper gas density as well as a simultaneously reduced gas load results in an increased stripping efficiency, while the beam emittance remains the same. A new record beam intensity (11.1 emA) for238U28+beams at 1.4 MeV/u has been achieved, applying the pulsed high density H2-stripper target to a high intensity238U4+beam from the VARIS ion source. Further ion source developments have been accomplished recently providing for sufficient heavy ion beam intensities at the High Current Injector Linac. A machine investigation program has been performed in 2020. The focus was to optimize the entire FAIR injector chain for high intensity heavy ion beam after the successful implementation of different upgrade measures. Besides a dedicated operation mode applying UNILAC, as a heavy ion Linac, at a synchronous phase significantly lower than 30 degrees for high intensity proton beam, could be established. Thus, UNILAC is able to deliver a sufficient proton beam intensity for the FAIR commissioning phase, when the FAIR-proton Linac is not yet available.

Duty Factor Reflects Lower Limb Kinematics of Running

The aim was to identify the differences in lower limb kinematics used by high (DFhigh) and low (DFlow) duty factor (DF) runners, particularly their sagittal plane (hip, knee, and ankle) joint angles and pelvis and foot segment angles during stance. Fifty-nine runners were divided in two DF groups based on their mean DF measured across a range of speeds. Temporal characteristics and whole-body three-dimensional kinematics of the running step were recorded from treadmill runs at 8, 10, 12, 14, 16, and 18 km/h. Across speeds, DFhigh runners, which limit vertical displacement of the COM and promote forward propulsion, exhibited more lower limb flexion than DFlow during the ground contact time and were rearfoot strikers. On the contrary, DFlow runners used a more extended lower limb than DFhigh due to a stiffer leg and were midfoot and forefoot strikers. Therefore, two different lower limb kinematic mechanisms are involved in running and the one of an individual is reflected by the DF.

J-PARC H- ion source and space-charge neutralized LEBT for 100-mA high energy and high duty factor LINACs.

In July 2019, a design beam of 8.3 × 1013 protons/pulse, whose 25 Hz operation produced the design beam power of 1 MW, was accelerated for 10.5 h by using the J-PARC 3 GeV rapid cycling synchrotron. During the operation, a J-PARC H- ion source and a 400 MeV linear accelerator (LINAC) were operated with the design beam duty factor (BDF) of 1.25% (0.5 ms × 25 Hz) and ejected beam intensities of 58 mA and 50 mA, respectively. Furthermore, as expected from the transverse emittances measured in an H- ion source test-stand, they were successfully operated with the BDF of 1.5% (0.6 ms × 25 Hz) and ejected beam intensities of 72 mA and 60 mA, respectively. In the operation, the beam pulse accelerated by the J-PARC radio-frequency quadrupole LINAC (RFQ) had a rapid rise-time of about 10 µs and an excellent flatness with a slow variation of ±0.2%. A flat beam pulse was produced by the predicted 100% space-charge neutralization (SCN) in the upstream half of the J-PARC low-energy beam transport (LEBT) with a vacuum pressure of 3.6 × 10-4 Pa and the unpredicted high and almost constant SCN of about 69% in the downstream half of the LEBT with a vacuum pressure of 2.8 × 10-5 Pa. The rapid rise-time was produced by the preformed 100% SCN with a preceding 100 µs 40 keV beam, which was not accelerated by the RFQ due to the low energy outside the RFQ acceptance. In the test-stand operated with the terminal voltage of 62 kV and BDF of 5% (1 ms × 50 Hz), the transverse emittances of a 100-mA beam were also measured to be suitable for the RFQs of high energy LINACs. A 100-mA high energy and high duty factor LINAC could be realized with this source since the transverse emittances were further improved by about 8% with the shortest beam extractor in the test-stand.

EDM ASSISTED BY MAGNETIC FIELD FOR ARMOURED STEEL

The present paper presents a study on the performance of electrical discharge machining (EDM) assisted by magnetic field for armoured steel (HV500). Response surface methodology (RSM) has been utilized to model, analyze and determine the optimal parameters setting in the EDM process assisted by magnetic field. The process performance criteria such as; material removal rate (MRR), tool wear rate (TWR), were evaluated. Peak current, magnetic flux density, duty factor, and dielectric fluid pressure have been considered the main factors affecting EDM assisted by magnetic field performance. RSM was employed to develop the experimental models. The EDM process assisted by magnetic field process has proved its adequacy to machine armoured steel alloy under acceptable metal removal rate and minimum tool wear rate. The metal removal rate generally increases with the increase of the magnetic flux density and peak current value. The effect of duty factor was limited and dielectric fluid pressure has a moderate effect. Further, the minimum tool wear rate has been obtained at the parametric combination of higher magnetic flux density and higher duty factor when machined by EDM assisted by magnetic field with copper electrodes. It has also been clarified that the effect of magnetic flux density was limited on metal removal rate with graphite electrodes. It has also been found that the minimum tool wear rate was obtained at the parametric combination of higher magnetic flux density, higher peak current and lower duty factor, when machined by EDM assisted by magnetic field, with graphite electrodes.

Duty Factor Is a Viable Measure to Classify Spontaneous Running Forms.

Runners were classified using two different methods based on their spontaneous running form: (1) subjectively using the V®score from the Volodalen® scale, leading to terrestrial and aerial groups; and (2) objectively using the duty factor (DF), leading to high (DFhigh) and low (DFlow) DF groups. This study aimed to compare these two classification schemes. Eighty-nine runners were divided in two groups using the V®score (VOL groups) and were also ranked according to their DF. They ran on a treadmill at 12 km·h−1 with simultaneous recording of running kinematics, using a three-dimensional motion capture system. DF was computed from data as the ratio of ground contact time to stride time. The agreement (95% confidence interval) between VOL and DF groups was 79.8% (69.9%, 87.6%), with relatively high sensitivity (81.6% (68.0%, 91.2%)) and specificity (77.5% (61.6%, 89.2%)). Our results suggest that the DF and V®score reflect similar constructs and lead to similar subgroupings of spontaneous running form (aerial runners if DF < 27.6% and terrestrial runners if DF > 28.8% at 12 km·h−1). These results suggest that DF could be a useful objective measure to monitor real-time changes in spontaneous running form using wearable technology. As a forward-looking statement, spontaneous changes in running form during racing or training could assist in identifying fatigue or changes in environmental conditions, allowing for a better understanding of runners.

Uniformity and stability of the LSST focal plane

The Large Synoptic Survey Telescope (LSST) focal plane consists of 21 autonomous modules [raft tower modules (RTMs)], each of which contains nine thick, fully depleted 4k × 4k CCDs with associated control and readout electronics. To enable LSST’s repetitive short-exposure cadence while maintaining high duty factor and low read noise, the readout is highly parallelized into 3024 independent video channels (16 per CCD and 144 per RTM). Two vendors supplied the LSST sensors; the devices have compatible mechanical and electrical interfaces and meet the same electro-optic specifications, but each RTM is constructed with sensors from a single supplier. The full complement of rafts was assembled at Brookhaven National Laboratory during January 2017 to January 2019. Each unit underwent extensive electro-optic and metrology characterization at operating temperature, the results of which are presented here along with a discussion of uniformity and stability.

Production of hard and lubricating surfaces on miniature components through micro-EDM process

The study acclaims the generation of hard, wear-resistant, and lubricating layer on Ti alloy using molybdenum disulfide (MoS2) powders mixed in dielectric (deionized water) using a brass tool electrode (diameter 800 μm) through the micro-electrical discharge process. The deposition rate, micro-hardness, recast layer, and surface roughness were studied for the surface generated through the process and correlated with the XRD, AFM, electron probe micro-analyzer, EDS analysis, and FESEM images. Results indicate that a higher voltage (60 V) and powder concentration (12 g/L) increase the material deposition rate in the form of intermetallic compounds deposited on the recast layer. The coated layer formed shows an increase in micro-hardness ranging from 426.42 to 714.25 HV, which is more when compared to the base material hardness of 417.61 HV. In addition to this, lower micro-cracks were seen at high powder concentration, voltage, and duty factor with improved surface quality. The pin-on-disc wear test of the coated samples was performed, and results indicated that the specific wear rate decreased with the increase in duty factor due to the formation of hard and wear-resistant intermetallic compounds as confirmed from the EDS and XRD plots.

Progress of the CFETR design

The Chinese Fusion Engineering Testing Reactor (CFETR), complementing the ITER facility, is aiming to demonstrate fusion energy production up to 200 MW initially and to eventually reach DEMO relevant power level 1 GW, to manifest a high duty factor of 0.3–0.5, and to pursue tritium self-sufficiency with tritium breeding ratio (TBR) >1. The key challenge to meet the missions of the CFETR is to run the machine in steady state (or long pulse) and high duty factor. By using a multi-dimensional code suite with physics-based models, self-consistent steady-state and hybrid mode scenarios for CFETR have been developed under a high magnetic field up to 6.5 T. The negative-ion neutral beam injection together with high frequency electron cyclotron wave and lower hybrid wave (and/or fast wave) are proposed to be used to drive the current. Subsequently the engineering design of CFETR including the magnet system, vacuum system, tritium breeding blanket, divertor, remote handling and maintenance system will be introduced. Some research and development (R&D) activities are also introduced in this paper.

Realizing Efficient Front Crawl Stroke With a Wheel-Paddle-Integrated Mechanism: Inspired by Human Competitive Swimming

Oscillating propulsion is widely used in underwater robots, which is inspired by the fin of fish. However, the negative force generated during the locomotion is affecting the propelling efficiency. To tackle such a problem, a swimming mode called front crawl stroke, which gets inspiration from human competitive swimming, has been proposed in this paper. It was implemented in a wheel-paddle-integrated mechanism. This mechanism is capable of flexible transformation among various locomotion modes, permitting more choices when facing complex application environment. The proposed front crawl stroke was studied both theoretically and experimentally. The results suggest that when generating the same maximum propelling force, the front crawl stroke can produce less negative force than the oscillating mode, so as to larger effective net thrust. Furthermore, the propelling efficiency of the front crawl stroke is 2.7 times higher than the oscillating mode. The stroke was also explored with various periods and duty factors. It was found that shorter period and lower duty factor can generate larger net thrust, whereas the force of longer stroke period and higher duty factor is comparatively stable.

The implications of time on the ground on running economy: less is not always better.

A lower duty factor (DF) reflects a greater relative contribution of leg swing versus ground contact time during the running step. Increasing time on the ground has been reported in the scientific literature to both increase and decrease the energy cost (EC) of running, with DF reported to be highly variable in runners. As increasing running speed aligns running kinematics more closely with spring-mass model behaviours and re-use of elastic energy, we compared the centre of mass (COM) displacement and EC between runners with a low (DFlow) and high (DFhigh) duty factor at typical endurance running speeds. Forty well-trained runners were divided in two groups based on their mean DF measured across a range of speeds. EC was measured from 4min treadmill runs at 10, 12 and 14 km h-1 using indirect calorimetry. Temporal characteristics and COM displacement data of the running step were recorded from 30s treadmill runs at 10, 12, 14, 16 and 18 km h-1 Across speeds, DFlow exhibited more symmetrical patterns between braking and propulsion phases in terms of time and vertical COM displacement than DFhigh DFhigh limited global vertical COM displacements in favour of horizontal progression during ground contact. Despite these running kinematics differences, no significant difference in EC was observed between groups. Therefore, both DF strategies seem energetically efficient at endurance running speeds.

Numerical simulation of high-intensity metal ion beam generation

The features and regularities of plasma-immersion formation of high-intensity repetitively pulsed beams of aluminum ions, as well as their transportation and ballistic focusing in an accelerating system with a curvilinear extracting potential grid electrode under application of negative bias with high pulse repetition rate of f = 105 Hz are studied by numerical methods. It is shown that the amplitude and shape of the ion beam current pulse depend significantly on the dynamic conditions of space charge neutralization of the beam. In case of using of bias potential with high duty factor, e.g. conditions of limited time of vacuum-arc plasma preinjection, the process of transportation and ballistic focusing of the ion beam up to densities manifold exceeding the density of the preliminary injected plasma, it is possible to obtain conditions leading to the formation of a virtual anode. It is shown that secondary electrons can be one of the additional mechanisms of compensation of the beam space charge which results in the improvement of transportation of high-intensity beams of aluminum ions.