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Dynamic control of laser-produced proton beams

Dynamic control of laser-produced proton beams

on laser and target parameters). The manipulation of laser generated proton beams gives new challenges due to the high bunch charge and short pulse nature of the beams, requiring innovative approaches to enable beam control - recently a technique employing electric fields triggered by a second laser pulse on a separate target, has been used for focusing selectively a portion of the beam spectrum [10]. However, the inherent large divergence and energy spread can make it hard to utilise the full flux of the proton beam for applications and indeed for further transport and beam manipulation. Here we demonstrate a novel target configuration which, without the need for an auxiliary laser pulse, exploits the self-charging of the target to improve the collimation of the entire proton beam, while conserving the characteristic high laminarity required for radiography applications [11]. This approach also allows the control of chromatic properties of the beam and creation of achromatic electrostatic lenses, by exploiting the strong temporal variation of the target potential. Hence this technique allows the full flux of the proton beam to be used in many demanding applications in science, medicine and industry [7].
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Cascaded acceleration of proton beams in ultrashort laser-irradiated microtubes

Cascaded acceleration of proton beams in ultrashort laser-irradiated microtubes

an injected proton beam, this proton beam can be effi- ciently further accelerated by the transient axial electric field in the laser-irradiated microtube. Further, the ener- gy spread of the injected proton beam can be reduced if the accelerating field is still rising when the proton beam comes out the microtube. In addition, the divergence of the injected proton beam could be suppressed by the inward radial electric field in the microtube. More impor- tantly, this cascaded acceleration scheme works well with the non-relativistic laser pulses and the injected proton beams with initial energies up to a few hundred MeV. Therefore, proton beams may be accelerated in multi- stages with this scheme to higher energy.
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Spectral modification of laser-accelerated proton beams by self-generated magnetic fields

Spectral modification of laser-accelerated proton beams by self-generated magnetic fields

40 fs laser pulse were found to have energy spectra that contained a broad peak near to 1 MeV. By carrying out 2D PIC simulations of the experiment, it has been concluded that quasi-static magnetic fields at the rear of the target are responsible for producing these spectral peaks. As the spectrometer only measures those protons that are emitted into a narrow cone, the quasi-static magnetic field will strongly shape the spectrum by deflections in the field that are dependent on the dwell time of the proton in the field. This produces broad spectral peaks. This may provide a new or complementary route to optically controlling the energy spectrum of laser-accelerated proton beams, in contrast to the ‘target engineering’ approach, which has previously been advocated [14]. This work also highlights a more generic issue—that of properly accounting for the limited angular sampling of magnetic spectrometers when interpreting ion acceleration experiments.
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Angle-dependent modulated spectral peaks of proton beams generated in ultrashort intense laser-solid interactions

Angle-dependent modulated spectral peaks of proton beams generated in ultrashort intense laser-solid interactions

Laser-driven ion beams hashave advantages of short pulse duration, high brightness and small source size. For their potential applications such as proton radiography 1 , proton-driven fast ignition 2 , tumour therapy 3 , proton-driven nuclear reactions 4 , etc., monoenergetic spectral distributions of protons are preferred. However, most of the experimentally generated proton beams present exponential-like proton energy spectra. To produce proton beams with modulated spectral distributions, several mechanisms, such as radiation pressure acceleration 5 , break-out afterburner 6 , and laser-driven shock acceleration 7 , have been proposed, and successfully demonstrated by numerical simulations and experiments 8,9 . However, to implement these mechanisms the drive laser pulses must have very high contrast ratio better than 10 -10 and high focused intensity higher than 10 21 W/cm 2 , typically. Such requirements are great challenges for the laser systems in commission.
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Manipulation of the spatial distribution of laser-accelerated proton beams by varying the laser intensity distribution

Manipulation of the spatial distribution of laser-accelerated proton beams by varying the laser intensity distribution

increasing the pulse energy has a significantly larger influ- ence on the total flux of protons than the same increase in in- tensity obtained by reducing the laser spot size. Xu et al. 11 and Green et al. 12 show that, with constant laser pulse energy and pulse duration, the total flux of protons can be increased by defocusing the laser at the target, even though the peak laser intensity is decreased. The proton beam divergence depends on the laser parameters and on the proton energies; the most energetic protons exhibit the smallest divergence. 13 Schollmeier et al. 14 used micro-structured target foils as a tool to demonstrate the effect of defocusing the laser beam on the generated proton beam. Several more studies have been reported in the literature regarding the proton beam divergence and laminarity 15 and how they can be manipu- lated, e.g., via the use of curved targets. 16,17 In this paper, we report on experimental studies of how the angular/spatial dis- tribution of the proton beams can be manipulated without changing the target shape or composition, and instead by varying spatially the laser intensity distribution on the tar- get’s front surface. We keep the target and laser parameters fixed and vary the intensity distribution while monitoring the
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Stable laser-produced quasimonoenergetic proton beams from interactive laser and target shaping

Stable laser-produced quasimonoenergetic proton beams from interactive laser and target shaping

There is increasing demand worldwide for more effective cancer therapy techniques. Among all the known methods, ion beams show incomparable advantages due to their high cure rate and painless treatment, mainly due to its unique sharp Bragg absorption peak. Usually well controlled energy spectrum ( Δ E E / ~ 1% ) proton beams with energy around 200MeV or carbon ions with energy around 400MeV/amu and flux ≥ 10 10 s -1 are essential for practical applications of this technique. Even though the traditional accelerator technology is able to get such ion beams currently, the huge cost in the construction and maintenance of a large ion accelerator and subsequently the large cost imposed to patient may limit its wide applications. On the other hand, with the rapid development of ultra-intense laser technology [1], there have been lots of studies on ion beam generation by using laser plasma interaction (see Ref. [2] and references therein) aiming at cancer therapy and related applications [3-5].The method of laser driven ion beams may allow potential simplification in beam control, avoiding gantry systems with the conventional accelerator technology. Laser plasma interaction has been proved to be a promising way to obtain high energy particle beams. For example, GeV level electron beams [6] and tens of MeV level ion beams have already been demonstrated in experiments [2].Currently one of the big challenges is to produce >200MeV proton beams under feasible experimental conditions. It is much more difficult to accelerate ions than electrons because of the large mass to charge ratio of ions.
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Spectral shaping of laser generated proton beams

Spectral shaping of laser generated proton beams

Clearly, monoenergetic proton beams at 9.3 MeV central energy will not yet be a competitor for conventional accelerators. They will, however, be of great value when starting to investigate the suitability of laser accelerators as pre-acceleration stages for e.g. storage rings, which would be a first step to combine the unique acceleration fields of laser plasma sources with the mature conventional accelerator technology. Also, they will open up the possibility of the first biophysical experiments, such as pulsed proton irradiation of biological tissue. 10 MeV protons are capable of penetrating up to 1.2 mm into biological tissue, which—in conjunction with the narrow bandwidth—would allow for a concise dose application. For more conclusive estimations, the dependency of the peak properties on other laser parameters such as pulse duration and intensity has to be investigated, which will be the subject of future experiments. The continuation of the present work will also include the study of micro-dot targets both with reduced hydrogen concentration (as proposed in [27, 32]) as well as heavier dot materials (e.g. carbon dots). In the prospect of these promising experiments, however, today’s capability of reliably generating 10 9 quasi-monoenergetic protons with less than 10% bandwidth by means of a scalable technique marks an important step towards application and will contribute significantly to the future of laser particle acceleration.
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Fast electron transport patterns in intense laser-irradiated solids diagnosed by modeling measured multi-MeV proton beams

Fast electron transport patterns in intense laser-irradiated solids diagnosed by modeling measured multi-MeV proton beams

profile, is strongly affected by the target electrical resistivity at relatively low temperatures. In that study, performed at a higher peak laser intensity (2 × 10 20 Wcm − 2 ) smooth proton beams were obtained for diamond targets (across the full proton beam area) and structured beams were measured with vitreous carbon. The difference between the two results was explained by the higher resistivity of vitreous carbon at relatively low temperatures of 1 – 50 eV, giving rise to higher resistive instability growth rates. The differences in resistivity of the two carbon targets arises due to the different degree of ordering of the carbon ions (i.e., the lattice struc- ture). The distinctly different proton beam profile measured with diamond for the lower peak laser intensity in the present work points to a different fast electron beam transport pattern within the target.
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Study of the Drell-Yan process with the pair-production of polarized tau leptons in collisions of polarized proton beams

Study of the Drell-Yan process with the pair-production of polarized tau leptons in collisions of polarized proton beams

Hence, for a consistent description of processes with polarized nucleons in a wide en- ergy range and the most complete description of the proton structure a generalized parton model was developed [3–5], which consist of 8 specialized parton distribution functions. These functions are: the distribution of the parton density in unpolarized nucleon (Den- sity); distribution of the longitudinal polarization of quarks in the longitudinally polarized nucleon (Helicity); distribution of transverse polarization of quarks in transversely polarized nucleon (Transversity); the correlation between the transverse polarization of a nucleon and the transverse momentum of unpolarized quarks (Sivers); the correlation between the trans- verse polarization of a nucleon and the longitudinal polarization of quarks (Worm-gear-T);
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Buffered high charge spectrally-peaked proton beams in the relativistic-transparency regime

Buffered high charge spectrally-peaked proton beams in the relativistic-transparency regime

At higher energies, a low divergence component ( »  5 ) close to the laser-axis becomes apparent, consistent with the central beams seen experimentally. The sheath of the self-generated cone has a focussing effect on protons still being accelerated within the evacuated region, similar in action to other laser-triggered charged particle lenses [38, 39]. The focussing field, shown in figure 5(f), is maintained until the end of the interaction, producing a collimated beam on-axis. For thicker targets, there are suf fi cient protons in the target that a larger fraction remain in the central region, reducing the collimating effect. A static B - fi eld of magnitude » 2 kT also forms, and though providing an order of magnitude lower force on the protons than the electric field, acts to pinch the forward laser driven relativistic electrons, further enhancing the space charge collimating fields during the laser plasma interaction. Note that only the protons nearest the laser-axis are refocused by this collimating fi eld; further off-axis more divergent protons continue to be accelerated in the hot electron driven sheath fi elds to high energies. As previously discussed, such a highly divergent but lower fl ux beam was also witnessed in the experiment.
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A two-dimensional angular-resolved proton spectrometer

A two-dimensional angular-resolved proton spectrometer

for plain metal foil target, asymmetric proton beams were also measured. 18 To resolve the non- uniformity and asymmetry in proton beams, the two-dimensional (2D) angular-resolved measurement is pre-requisite. Furthermore, due to the limited target alignment accuracy, the target normal axis may have a pitch angle with respect to the laser incidence plane, causing the proton beam pointing variation from shot to shot. The 1D angular-resolved measurement may introduce systematic errors. Therefore, a 2D angular-resolved proton spectrometer is more desirable for source characterization, which is expected to give a more comprehensive picture on energy- and spatial-intensity distributions of proton beam. By using a 2D entrance-pinhole array, we designed a spectrometer which is capable of measuring the energy spectra in 2D angular dimensions simultaneously.
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Instrumentation for diagnostics and control of laser-accelerated proton (ion) beams

Instrumentation for diagnostics and control of laser-accelerated proton (ion) beams

There are high demands on the accuracy of biomedical beam monitors, typically better than 95%. A typical treatment fraction, consisting of 10 7 e 10 9 particles/cm 2 , delivered in a few hundred ms in present proton therapy, could be supplied from a single laser shot, where the bunch duration is of nanosecond order. Therefore, for laser-driven accelerators, dose rates can be several orders of magnitude higher than those conventionally used today [42]. This can be problematic for detectors typically used in particle therapy such as multiwire ionisation chambers. The pixilated detector advantage is attributed to the large number of small single pixels, where, each represents a small diode detector. This reduces the number of particles per pixel to a level that is within its dynamic range, and affords measurement of a 2D fl uence distribution with high spatial resolution. First tests of commercial CCD-based pixel detector, conducted at a conventional electrostatic accelerator us- ing 10 and 20 MeV proton beams (dc, pulsed and single ions), show good linearity between integrated detector signal level and particle fl uence, and also suf fi cient dynamic range for this application. Single ion detection is likewise possible for detection of up to 10 7 protons/cm 2 (shown at proton energy of 20 MeV [43]). Similar results were obtained for a CMOS photodiode array that was tested on equal terms [43].
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Microfabrication in Foturan™ Photosensitive Glass Using Focused Ion Beam

Microfabrication in Foturan™ Photosensitive Glass Using Focused Ion Beam

Recent work has investigated the use of femstosecond pulse UV excimer lasers to expose Foturan TM wafers using a direct write technique eliminating the requirement for the manufacture of masks [7]-[9]. Feature resolution of 10μm has been reported. Gomez-Morilla et al have reported the first example of Foturan TM patterning by a direct write ion beam method, using a focused and scanned beam of MeV proton beams with a diameter of 2-3μm [10]. The very high energy of the beam produces an exposure depth of ∼60μm. Postbake and HF etch produce features of this depth with lateral dimensions in the 10μm range.
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Selection of the elastic scattering events in interactions of the NICA colliding proton (deuteron) beams

Selection of the elastic scattering events in interactions of the NICA colliding proton (deuteron) beams

In our previous reports and publications [2–4] we have considered opportunities of studying the spin 1/2 and 1 observables in the elastic interactions of the colliding proton and deuteron beams of the NICA collider. It has been shown that in elastic interactions of colliding proton beams one can measure energy and angular dependencies of the analyzing powers of the reactions with one polarized beam A oono or A ooon , and the spin correlation parameters A ookk and A oonn in collisions of both polarized

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Computer Integrated Design, Analysis and Shape Optimization of Proton Beam Dump

Computer Integrated Design, Analysis and Shape Optimization of Proton Beam Dump

100 MeV Proton Beam Irradiation Facility was designed for the PEFP 100 MeV LINAC by Yun et al. The author carried out the study upon general propagation shape and spatial distribution of proton beam which was to be extracted from the vacuum in the beamlines through beam window by Monte Carlo method so that proton beams can be utilized for research and development purpose. The author designed the arrangement like Beam Window, Beam Dump, Support Frame, etc. such that nonlinear proton beam transports to the target room, spread out by the octupole magnet in the target chamber so as to provide large and uniform proton beams. TRACE-3D was used for simulation for defining basic parameters of the beamlines. Based on the studies and results, beam irradiation elements as well as their configuration were designed. The irradiation equipment was designed in the target room to ensure safety from radiation, beam observation and beam current monitoring
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Average fast neutron flux in three energy ranges in the Quinta assembly irradiated by two types of beams

Average fast neutron flux in three energy ranges in the Quinta assembly irradiated by two types of beams

samples were located in the Quinta assembly in order to measure an average high neu- tron flux density in three different energy ranges using deuteron and proton beams from Dubna accelerators. Our analysis showed that the neutron density flux for the neutron en- ergy range 20.8 - 32.7 MeV is higher than for the neutron energy range 11.5 - 20.8 MeV both for protons with an energy of 0.66 GeV and deuterons with an energy of 2 GeV, while for deuteron beams of 4 and 6 GeV we did not observe this.

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Attitude towards E-learning Technology -- A study in Kerala

Attitude towards E-learning Technology -- A study in Kerala

High-strength concrete leads to more economical structures. It also leads to reduction in overall building height and dead load, because of the use of thinner slabs and shallower beams. The reinforced concrete (RC) structural elements such as the peripheral beams in each floor of multi storied buildings, ring beams at the bottom of circular tanks, edge beams of shell roofs, the beams supporting canopy slabs and the helical staircases are subjected to significant torsional loading in addition to flexure. Therefore, for understanding the behaviour of reinforced high strength beam, it is necessary to study the beam under combined bending and torsion.
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Mitochondrial proton leak compensates for reduced oxidative power during frequent hypothermic events in a protoendothermic mammal, Echinops telfairi

Mitochondrial proton leak compensates for reduced oxidative power during frequent hypothermic events in a protoendothermic mammal, Echinops telfairi

FIGURE 4 | Calculation of coupling efficiency that is defined as the respiratory fraction that drives the ATP synthase. (A) Single example how coupling efficiency is assessed per individual. State 3 and proton leak respiration at the state 3 membrane potential (indicated by the dashed line) are required. (B) Coupling efficiency = (state 3—proton leak respiration)/ (state 3 respiration at state 3 membrane potential). 20 ◦ C acclimated (CA, white circles, n = 3) vs. 27 ◦ C acclimated (WA, black circles, n = 4) groups were not significantly different (two-way repeated measures ANOVA). Therefore, the linear regression analysis was performed on the combined data from both acclimation groups; y = −0.012x + 1.077 (ANOVA, P = 0.064). Values are means ± SE.
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Flexural Behaviour of Geopolymer Concrete Beams using Recycled Waste Glass as Fine Aggregate

Flexural Behaviour of Geopolymer Concrete Beams using Recycled Waste Glass as Fine Aggregate

Abstract—Cement substitutes and concrete alternatives are currently on the market to help in creating concrete a very eco- friendly material. In cement concrete production, heating and compounding method need large amounts of energy and emits minacious amounts of CO2 into the atmosphere. There has been an increasing significant interest in the development of cement less concrete called geopolymer concrete. In this study, cement is replaced entirely by ash and GGBS for making of geopolymer concrete. Now a days, the scarcity of river sand can have an effect on the development trade and hence there's a requirement of finding a replacement different material to switch the river sand. Non-reactive recycled waste glass is chosen as alternative to the river sand. Various grades of concrete including M 20, M 40 and M 60 grades are developed in GP concrete and also same proportion is used for making GP concrete with glass aggregate. In geopolymer preparation, NaOH of 8 molarity concentration is used. Flexural behaviour of beams is studied by casting of nine beams of size 125 mm × 200 mm × 1100 mm. The beams are designed as under reinforced sections. Out of nine beams, three beams of M 20, M 40 and M 60 grade conventional cement concrete beams, three beams of GP beams and the remaining three beams are made with RWGFA in GP. Beams are tested under two point loading for flexure. The ultimate load carrying capability of all beams is obtained. The crack and deflections of the beams are studied. The experimental results are compared with finite element modeling using ANSYS software.
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Resonance Production with the LHCb Experiment

Resonance Production with the LHCb Experiment

Abstract. Studies of strange and charm resonance production in the forward region pro- vide important input to the importance to the understanding of QCD models. The latest studies at LHCb of resonance production in both proton-proton and proton-lead colli- sions are presented, with particular emphasis on charmonium production including the production of Z(4430).

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