Optimum Target Thickness Research Articles

Design of a multi-carrier X-ray source for communication with energy modulation information.

X-ray communication is a kind of space communication technology which uses X-ray as information carrier. In order to improve the information transmission capacity, communication rate and anti-interference ability of X-ray communication, we proposes to design a novel multi-target X-ray source. The source is composed of a fast switching module of light channels based on FPGA technology and four photoelectric X-ray tubes with different target materials: Cr, Fe, Ni, and Cu. Using Geant4 software, we determined the optimal target thickness for each material, which enabled us to fully leverage the characteristic X-rays for multi-channel signal modulation transmission. Moreover, using CST software for particle trajectory simulation and optimization of the electron beam revealed that at a tube voltage of 20 kV, the focus area measures approximately 1.2 mm×1.2 mm. The simulations show that four kinds of spectra with high distinctiveness can be generated from the Cr, Fe, Ni, and Cu targets. Within a single modulation period, these spectra can be combined in various ways to create 16 different X-ray spectra signals, thereby increasing the number of communication elements and enhancing the information transmission rate.

Water-window x-ray emission from laser-produced Au plasma under optimal target thickness and focus conditions.

Optimal laser irradiation conditions for water-window (WW) x-ray emission (2.3-4.4nm) from an Au plasma are investigated to develop a laboratory-scale WW x-ray source. A minimum Au target thickness of 1 µm is obtained for a laser intensity of ∼10^{13} W/cm^{2} by observing the intensity drop in the WW spectra. Au targets produced by thermal evaporation are found to have a higher conversion efficiency than commercial foil targets for WW x-ray radiation. In addition, optimal laser spots for fixed laser energies (240 and 650mJ) are found for an Au target ∼1mm in front of the focal point, where suitable conditions for plasma temperature and plume volume coupling are achieved. The mechanism of the optimal target thickness and spot size can be well explained using a radiation hydrodynamic simulation code.

Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities

Laser-driven ion sources are a rapidly developing technology producing high energy, high peak current beams. Their suitability for applications, such as compact medical accelerators, motivates development of robust acceleration schemes using widely available repetitive ultraintense femtosecond lasers. These applications not only require high beam energy, but also place demanding requirements on the source stability and controllability. This can be seriously affected by the laser temporal contrast, precluding the replication of ion acceleration performance on independent laser systems with otherwise similar parameters. Here, we present the experimental generation of >60 MeV protons and >30 MeV u−1 carbon ions from sub-micrometre thickness Formvar foils irradiated with laser intensities >1021 Wcm2. Ions are accelerated by an extreme localised space charge field ≳30 TVm−1, over a million times higher than used in conventional accelerators. The field is formed by a rapid expulsion of electrons from the target bulk due to relativistically induced transparency, in which relativistic corrections to the refractive index enables laser transmission through normally opaque plasma. We replicate the mechanism on two different laser facilities and show that the optimum target thickness decreases with improved laser contrast due to reduced pre-expansion. Our demonstration that energetic ions can be accelerated by this mechanism at different contrast levels relaxes laser requirements and indicates interaction parameters for realising application-specific beam delivery.

Target cooling options for DARIA compact neutron source

The extensive heat release in the target is the primary limiting factor for a CANS neutron output. CANS DARIA has been chosen to operate using a 13 MeV proton beam providing up to 40 kW of power, which requires an effective target cooling solution. It was found that beryllium provides the best neutron yield while staying in solid state, which makes it the most effective option for the target material. With an optimal beryllium target thickness of 1.1 mm, the proton Bragg peak lies outside of the beryllium layer, but 9.21 MeV per incident proton are still dissipated inside the beryllium. Two cooling options are considered and analysed with PHITS calculations: multilayer targets and rotating targets. The use of proton beams with energies above 13 MeV on beryllium leads to tritium generation, which is not desirable. Any lower energy leads to a decreased neutron yield, but a simpler cooling solution. Therefore, an option to reduce the proton beam energy is also considered.

Preparation and quality control of a new porphyrin complex labeled with 45Ti for PET imaging

This study aims to produce and quality control of a new porphyrin complex labeled with 45Ti for PET imaging, so at the first step, the cross-section of 45Sc(p,n)45Ti was investigated by TALYS-1.6 and the optimal target thickness and theoretical yield were calculated by SRIM code. The purified 45Ti was labeled with the anticancer agent of tetrakis (pentafluorophenyl) porphyrin (TFPP). The radiochemical purity and the percentage of labeling were evaluated by radiation layer chromatography then the division coefficient of [45Ti]-TFPP was calculated. The dual coincidence imaging system was used for imaging 1 and 2 h after injection [45Ti]-TFPP to rats. Immediately after imaging, the mean percent injected dose per gram and specific activity of different tissues including blood, heart, lungs, stomach, liver, bone, kidney, spleen, intestine, muscle, feces, and skin were measured. The yield of 45Ti production was measured 468 MBq/μAh and the labeling rate was observed more than 98%. The highest activity was observed in the liver (%ID/g = 2.27%, 1 h) and spleen (2.2%, 1 h), respectively, because of the high lipophilic of 45Ti-TFPP. SPECT images showed a significant uptake of radiopharmaceuticals in the abdomen. The labeling rate of 45Ti-TFPP was high and this compound has the potential for clinical application in different ways than PSMA, it can be joined with photodynamic therapy (Severin et al., 2015).

Monte Carlo simulation of the effective Sherman function for electron polarimetry in the few-MeV energy range

The effective analyzing power in Mott scattering was computed with a Monte Carlo simulation and compared to experimental results for electron-beam energies between 1.0 and 3.5 MeV. The dependence on target thickness and beam energy was analyzed, and possible parametrizations were discussed. The optimal target thickness and scattering angle for the measurement of polarization transfer in Møller scattering were determined.

Advancements in the fabrication and characterization of actinide targets for superheavy element production

The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material.

Acceleration of 60 MeV proton beams in the commissioning experiment of SULF-10 PW laser

We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility (SULF). The peak power reaches 2.4 PW on target without the last amplifying during the experiment. The laser energy of 72 ± 9 J is directed to a focal spot of approximately 6 μm diameter (full width at half maximum) in 30 fs pulse duration, yielding a focused peak intensity around 2.0 × 1021 W/cm2. The first laser-proton acceleration experiment is performed using plain copper and plastic targets. High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4 μm via target normal sheath acceleration. For plastic targets of tens of nanometers thick, the proton cut-off energy is approximately 20 MeV, showing ring-like or filamented density distributions. These experimental results reflect the capabilities of the SULF-10 PW beamline, for example, both ultrahigh intensity and relatively good beam contrast. Further optimization for these key parameters is underway, where peak laser intensities of 1022–1023 W/cm2 are anticipated to support various experiments on extreme field physics.

Optimization of target thickness and investigation on the effect of heat treatment on the ballistic performance of aluminium alloy 7075 targets against hard steel core projectile

Optimization of target thickness and influence of heat treatment condition on the high velocity impact response of aluminium alloy 7075 targets have been determined. Both experimental and numerical studies were conducted using a 7.62 mm hard steel core projectile. The numerical simulation used a 7.62 mm Ogival nose shaped projectile with a target thickness ranging from 20 to 26 mm. High velocity impact experiments on T651 and solution treated targets, with rolled plate thicknesses ranging from 21 to 25 mm were carried out to validate the numerical findings. The microhardness of the targets was measured using Vicker's microhardness tester and fractographs were examined using a scanning electron microscope. The projectile penetrated regions were analyzed using light microscopy. A good correlation between the numerical and experimental ballistic behaviour of aluminium alloy 7075 targets was observed and an optimum target thickness of 21 and 24 mm was observed for the T651 and solution treated targets to prevent the projectile's penetration. It was also noted that, after the projectile's impact, solution treated targets had higher microhardness compared to T651 condition targets. This is due to higher work hardening of solution treated targets near the penetration channel. Even though T651 targets have a lower depth of penetration compared to solution treated targets, ‘splintering’ failure of the T651 targets is observed. In contrast, ‘petalling’ and ‘plugging’ kinds of failures were noticed on the solution treated targets. Thus, solution treatment of ballistic targets may enhance the ballistic limit of armoured vehicles.

Optimization of Transmission X-ray Target for Intense Pulsed Electron Beam Accelerators

X-ray sources based on pulsed electron accelerators stimulate the development of bremsstrahlung converter designs. The numerical optimization of transmission-type X-ray targets for maximum X-ray output by pulsed electron beams was carried out in the present work. The targets featured a combination of a heavy element (tungsten or molybdenum) X-ray conversion layer and a titanium membrane that served as the vacuum window, thermal shielding for converter heat, and an electron dump. The energy spectrum of the electron beam generated via explosive emission was analyzed via the space-charge effect, and was utilized for the source sampling algorithm for electron transportation simulation with a Monte Carlo method for X-ray emission analysis. It was revealed that the transmission photon intensity of a mono-material target is primarily affected by the thickness of the target, and there exists an optimal target thickness within which the photon fluence is restricted by insufficient electron stopping; when exceeded, the extra thickness of the X-ray converter target imposes absorption and attenuates the generated X-ray. Analysis on dual-layer targets proved that this optimized converter target thickness, combined with a proper titanium window, produces the highest X-ray photon emissions.

High-performance ion source generated by ultraviolet laser irradiation of Cu crystals

Ultraviolet laser driven radiation pressure acceleration of Cu crystals is investigated by using particle-in-cell simulations. When an ultrathin Cu crystal is irradiated by a circularly polarized pulse with wavelength λ = 72 nm, waist radius w0=4λ, and normalized magnitude a0=20 (energy of 85 mJ), a plasma with a lattice structure is generated first. Then, an acceleration field of 14.2 TV/cm can be induced by the radiation pressure of the ultraviolet pulse in the target, which is about one order of magnitude larger than that of optical lasers for the same a0, and the lattice structure exerts effect on the acceleration only in the vicinity of the optimal target thickness. As a result, a quasi-monoenergetic Cu ion beam of energy of 5 GeV (75 MeV/nucleon), a charge of 0.12 nC, and the emittance of 7×10−9 m rad can be produced, which implies that using ultraviolet lasers instead of optical lasers should turn down the size and emittance of ion sources by orders lower than that of optical lasers. Therefore, a high-performance ion source is produced, which may have potential applications in medical therapy and ion radiography.

Enhanced laser intensity and ion acceleration due to self-focusing in relativistically transparent ultrathin targets

Laser-driven proton acceleration from ultrathin foils is investigated experimentally using F/3 and F/1 focusing. Higher energies achieved with F/3 are shown via simulations to result from self-focusing of the laser light in expanding foils that become relativistically transparent, enhancing the intensity. The increase in proton energy is maximised for an optimum initial target thickness, and thus expansion profile, with no enhancement occurring for targets that remain opaque, or with F/1 focusing to close to the laser wavelength. The effect is shown to depend on the drive laser pulse duration.

Comparison of 192Os(p,n)192Ir and 192Os(d,2n)192Ir Nuclear Reactions for 192Ir Production

Iridium-192 ( 192 Ir ) is a radionuclide currently suggested for brachyteraphy. One of the methods employed to produce high purity 192 Ir is by irradiation of Osmium-192 ( 192 Os) target using cyclotron. The success of 192 Ir radionuclide production in cyclotrons requires deep understanding of irradiation parameters, including particle energy, target preparation and thickness, particle beam curent and irradiation time. Therefore, theoretical calculations of the 192 Ir radioactivity yields should be carried out as a preliminary measure for more efficient 192 Ir production. In this study, 192 Ir production was simulated using the SRIM 2013 program to determine the optimum target thickness while the nuclear cross-section data were extracted from TENDL 2017. Two nuclear reactions for 192 Ir production yield calculations were compared, i.e., 192 Os(p,n) 192 Ir and 192 Os(d,2n) 192 Ir. The radioactivity yields for 192 Os(p,n) 192 Ir nuclear reaction was found to be lower than 192 Os(d,2n) 192 Ir reaction. For proton and deuteron energy of 30 MeV, the maximum radioactivity yield was 6.79 GBq for 192 Os(p,n) 192 Ir and 26.14 GBq for 192 Os(d,2n) 192 Ir. Several radionuclide impurities such as 191m Ir, 190 Ir, 191 Os and 189 Re were predicted to be generated during 192 Os(p,n) 192 Ir reaction for proton incident energy between 1 and 30 MeV; meanwhile, 192 Ir, 191m Ir, 193 Os, 193m Ir, 192m Os and 191 Os radionuclides were expected to contaminate during 192 Os(d,2n) 192 Ir reaction for deuteron energy between 1 and 30 MeV. Results of this study can be used as a reference for future 192 Ir radionuclide production when proton or deuteron beams are considered to be employed. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif"; mso-ansi-language:EN-US; mso-fareast-language:EN-US;}

Design of bremsstrahlung target of 4 MeV flash X-ray machine

Bremsstrahlung converter target is one of the key factors for flash X-ray machine. The bremsstrahlung radiation process in which the electron beam impinges on the target is simulated utilizing the Monte Carlo method, by which the influence of the effective target thickness on the exposure is analyzed, the optimal target thickness and the exposure are also obtained for the 4 MeV flash X-ray machine. The damages of target impacted by the electron beam are compared and discussed for various electron energy deposit density from different sources, such as 12 MeV LIA, Dragon accelerators and 4 MeV flash X-ray machine. The results show that the tantalum distributed target may be the satisfactory solution for the bremsstrahlung target of 4 MeV flash X-ray machine.

The effect of target thickness on the efficiency of high-order harmonics generated from laser-driven overdense plasma target

In this paper, we analytically and numerically studied the impact of the target thickness on the efficiency of laser-plasma based high-order harmonics generation (HHG). The optimal parametric region is acquired where the laser normalized amplitude a0, the target density ne and thickness d0 satisfy the relation: for . In this region, the laser can partially penetrate the target, leading to efficient acceleration of the target. Meanwhile, the target is thick enough to oscillate along the rising edge of the laser without being broken, which guarantees the occurrence of HHG. Both one-dimensional and two-dimensional particle-in-cell simulation results verify our optimal target thickness theory, and a single attosecond pulse with I = 3.0 × 1020 W cm−2 is generated under the driving of 8.6 × 1020 W cm−2 , which is several hundred times more intense than that from a thick target.

Simulations of carbon ion acceleration by 10 PW laser pulses on ELI-NP

AbstractWe present results of 2D particle-in-cell (PIC) simulations of carbon ion acceleration by 10 petawatt (PW) laser pulses, studying both circular polarized (CP) and linear polarized (LP) pulses. We carry out a thickness scanning of a solid carbon target to investigate the ideal thickness for carbon ion acceleration mechanisms using a 10 PW laser with an irradiance of 5 × 1022 W cm−2. The energy spectra of carbon ions and electrons and their temperature are studied. Additionally, for the carbon ions, their angular divergence is studied. It is shown that the ideal thickness for the carbon acceleration is 120 nm and the cutoff energy for carbon ions is 5 and 3 GeV for CP and LP pulses, respectively. The corresponding carbon ions temperature is ~1 and ~0.75 GeV. On the other hand, the energy cutoff for the electrons is ~500 MeV with LP and ~400 MeV with CP laser pulses. We report that the breakout afterburner mechanism is most likely causing the acceleration of carbon ions to such high energies for the optimal target thickness.

Exploratory study for the production of Sc beams at the ISOL facility of MYRRHA preliminary thermal investigations

This paper reports on the start-up of an exploratory study for optimising an ISOL-target geometry towards isotopes production at driver-beam energies in the range of 100 MeV. A 1D algorithm that determines the optimal target thickness, as well as a partially algorithmic method that combines the particle-transport calculations with thermo-mechanical simulations have been developed. Further developments are planned in order to integrate an isotope-release model, as well as to provide a degree of automation, in order to facilitate optimisation. In the future this will allow easier determination of the optimal target design for the production of a specific isotope. To illustrate the optimisation process, the exploratory study for the production of scandium beams at an ISOL facility with a 100 MeV proton driver-beam is presented.

Design Study and Fabrication of the Target/Ion Source to Generate a Li-8 Beam

The Korea Multi-purpose Accelerator Complex (KOMAC) has developed a target/ion source (TIS) to generate a Li-8 radioactive isotope beam. The basic concept of the TIS is that the Li isotope is produced at a beryllium-oxide target irradiated by a 100-MeV proton beam, and Li atoms are ionized at a surface ionization ion source (SIS). Various numerical studies were conducted to design the TIS. The FLUKA code was utilized to estimate the Li-8 production rate and to find an optimum target thickness. Also, a simple Monte Carlo code was developed to estimate the ionization efficiency of the SIS. In addition, a zero-dimensional power balance model of the TIS was developed, and a three-dimensional finite-element method was applied to obtain detailed thermal analysis results. On the basis of the thermal analysis, the related design and operation parameters were determined. The TIS designed by using various numerical studies was fabricated and tested. The TIS will be irradiated by a proton beam and generate Li-8 beam for β-NMR facility.

Tungsten Target Optimization for Photon Fluence Maximization of a Transmission-Type Flat-Panel X-Ray Source by Monte Carlo Simulation and Experimental Measurement

The cold cathode flat-panel X-ray source is a new type of X-ray source with advantage of smaller footprint and lower-dose imaging than current sources. In this paper, we optimized the thickness of the anode target of a flat-panel X-ray source to maximize the photon fluence of X-rays generated from the device. Utilizing EGSnrc-based Monte Carlo code, X-ray fluence was calculate from the simulated photons deposited in the virtual detector. These results revealed an optimal target thickness at a specific anode voltage to maximize the output of X-ray intensity. For experimental validation, tungsten thin film anodes with different thicknesses were prepared, and a flat-panel X-ray source was fabricated using a ZnO nanowire cold cathode. A figure of merit was introduced to characterize the output efficiency of the X-rays. The experimental results agree well with the simulation results, showing an optimal tungsten-target thickness of 1200 nm at an anode voltage of 40 kV. Using a flat-panel X-ray source with the optimized anode thickness, we took X-ray absorption images of both biological and nonbiological subjects, and high-resolution images were demonstrated.

Numerical studies of acceleration of thorium ions by a laser pulse of ultra-relativistic intensity

One of the key scientific projects of ELI-Nuclear Physics is to study the production of extremely neutron-rich nuclides by a new reaction mechanism called fission-fusion using laser-accelerated thorium (232Th) ions. This research is of crucial importance for understanding the nature of the creation of heavy elements in the Universe; however, they require Th ion beams of very high beam fluencies and intensities which are inaccessible in conventional accelerators. This contribution is a first attempt to investigate the possibility of the generation of intense Th ion beams by a fs laser pulse of ultra-relativistic intensity. The investigation was performed with the use of fully electromagnetic relativistic particle-in-cell code. A sub-μm thorium target was irradiated by a circularly polarized 20-fs laser pulse of intensity up to 1023 W/cm2, predicted to be attainable at ELI-NP. At the laser intensity ~ 1023 W/cm2 and an optimum target thickness, the maximum energies of Th ions approach 9.3 GeV, the ion beam intensity is > 1020 W/cm2 and the total ion fluence reaches values ~ 1019 ions/cm2. The last two values are much higher than attainable in conventional accelerators and are fairly promising for the planned ELI-NP experiment.