Energy Loss Of Protons Research Articles

Contribution of Outer Electron and Inner-Shell Electron to Proton Energy Loss in Liquid Water and DNA

In the present work Drude-dielectric formalism has been used to calculate the effects of contribution of inner and outer-electron shell to energy-loss of protons liquid water H2O and DNA. The results show that the incident protons with energy between (T = 0.05, 0.25, 1, 2, 2.5 MeV) are very efficient in producing secondary electrons in dry DNA, which are able to produce strand breaks and could be very effective for the biological damage of malignant cells. The PSPEC, Stopping power, average energy transfer, ∆E and ionization energy have been calculated taking in the consideration the Sub-shells of each elements in DNA and H2O, Fourier energy density ρ (q), Charge exchange and Screening effects ᴧ. Good agreement achieved with the previous work [1].

Contribution of Outer Electron and Inner-Shell Electron to Proton Energy Loss in Liquid Water and DNA

In the present work Drude-dielectric formalism has been used to calculate the effects of contribution of inner and outer-electron shell to energy-loss of protons liquid water H2O and DNA. The results show that the incident protons with energy between (T = 0.05, 0.25, 1, 2, 2.5 MeV) are very efficient in producing secondary electrons in dry DNA, which are able to produce strand breaks and could be very effective for the biological damage of malignant cells. The PSPEC, Stopping power, average energy transfer, ∆E and ionization energy have been calculated taking in the consideration the Sub-shells of each elements in DNA and H2O, Fourier energy density ρ (q), Charge exchange and Screening effects ᴧ. Good agreement achieved with the previous work [1].

Band structure effects in the energy loss of low-energy protons and deuterons in thin films of Pt

We have investigated experimentally and by computer simulations the energy-loss and angular distribution of low energy (E<10keV) protons and deuterons transmitted through thin polycrystalline platinum films. The experimental results show significant deviations from the expected velocity dependence of the stopping power in the range of very low energies with respect to the predictions of the Density Functional Theory for a jellium model. This behavior is similar to those observed in other transition metals such as Cu, Ag and Au, but different from the linear dependence recently observed in another transition metal, Pd, which belongs to the same Group of Pt in the Periodic Table. These differences are analyzed in term of the properties of the electronic bands corresponding to Pt and Pd, represented in terms of the corresponding density of states. The present experiments include also a detailed study of the angular dependence of the energy loss and the angular distributions of transmitted protons and deuterons. The results are compared with computer simulations based on the Monte Carlo method and with a theoretical model that evaluates the contributions of elastic collisions, path length effects in the inelastic energy losses, and the effects of the foil roughness. The results of the analysis obtained from these various approaches provide a consistent and comprehensive description of the experimental findings.

Radiotherapy Improvements by Using Au Nanoparticles.

Au nanoparticles can be prepared inside biological solutions and incorporated in special molecules for their transport through blood, drugs and proteins up to the tumour sites or directly injected in their volume when it is possible. The Au nanoparticles are biocompatible and can be accepted locally in the organism also at relatively high concentrations. The use of Au nanoparticles injected in the tumour site enhances significantly the effective atomic number of the medium, depending on the used concentration, and consequently the proton and electron energy loss and the X-ray absorption coefficient determining an increment of the local absorbed dose during radiotherapy. Traditional radiotherapy using electrons, X-rays and gamma rays, and innovative protontherapy can benefit the increment of the effective atomic number of the tissue in the presence of Au-nanoparticles embedded in the tumour volume with an adaptive up-take procedure. This method decreases the dose released to the healthy tissues permitting a better cantering of the irradiated targets and shielding the healthy tissue placed behind the tumour. The presented theoretical study approach permits to evaluate an enhancement of the radiotherapy dose of the order of 1 % using 60 MeV protons, of the order of 10% using 6 MeV electrons and of the order of 100 % using 100 keV X-ray photons. Here, we also disccused for patents relaed to the topic.

The use of Parr temperature within the Lindhard dielectric function

SynopsisThe Parr distribution function is used within the Lindhard-Levine dielectric response function to calculate the energy loss of protons on the rare gases. This distribution is a function of the local temperature, which depends on the local kinetic energy. Present results compare quite well with the first Born approximation at high energies and open the way to use the Wigner distribution function.

SU‐C‐204‐04: Patient Specific Proton Stopping Powers Estimation by Combining Proton Radiography and Prior‐Knowledge X‐Ray CT Information

Purpose:The material relative stopping power (RSP) uncertainty is the highest contributor to the range uncertainty in proton therapy. The purpose of this work is to develop a robust and systematic method that yields accurate, patient specific, RSP by combining 1) pre‐treatment x‐ray CT and 2) daily proton radiograph of the patient.Methods:The method is formulated as a linear least‐square optimization problem (min||Ax‐B||2). The parameter A represents the pathlength crossed by the proton in each material. The RSPs for the materials (water equivalent thickness (WET)/physical thickness) are denoted by x. B is the proton radiograph expressed as WET crossed. The problem is minimized using a convex‐conic optimization algorithm with xi&lt;xi+1 constraint. The Gammex RMI‐465 phantom, with 13 material inserts, is used to investigate the optimal RSPs. The proton radiograph (B) is produced using Geant4 simulation. The matrix A is computed by calculating proton trajectories through the CT with the cubic‐spline approach. Geant4 RSPs are used as reference and the clinical HU‐RSP calibration curve is used as comparison. The convergence is investigated as a function of the number of angles and protons used. The radiographs angle which yield the most accurate RSPs are investigated.Results:Optimization with 9 angles and 104 protons/angle yields precise RSP (&lt;0.75%) for all materials, except plastic lung (1.5%). Average deviation relative to Geant4 RSP is 0.5% and 3.5% using HU‐RSP. Using more than two angles or more than 4×103 proton does not further increase the RSP estimate accuracy. The insert distance to the beam initial plane is related to the RSP error for this insert material. Specific filters are applied on the proton angle and energy loss to remove nuclear interaction artefacts.Conclusion:The proposed formulation of the problem with prior knowledge x‐ray CT demonstrates serious potential to increase the accuracy of present RSP estimates.

Gold nanoparticles enhancing protontherapy efficiency.

The insertion of gold nanoparticles in biological liquids, tissues and organs permits to increase the equivalent atomic number of the medium that, if used as target to be irradiated by ionizing radiation, permits an increment of the absorbed dose. No toxic nanoparticles, such as the Au, can be injected in the cancer tissues at different concentrations before using a localized treatment that uses energetic proton beams for radiotherapy. Due to the high density and atomic number of the used gold nanoparticles, the absorbed radiation dose can be increased to about a factor six per cent using relatively low concentration of nanoparticles injectable as solution in the tumor tissue. This means to reduce the exposition to ionizing radiation or to increase the dose to the tumor site. Simulation programs of proton energy loss in tissues, using SRIM Code, are employed to evaluate the Bragg peak enhancing in presence of Au nanoparticles, so it will be presented and discussed. Some research findings and patents in the gold nanoparticle preparation and application to Medicine are reviewed in the present paper.

Handling missing data for the identification of charged particles in a multilayer detector: A comparison between different imputation methods

Identification of charged particles in a multilayer detector by the energy loss technique may also be achieved by the use of a neural network. The performance of the network becomes worse when a large fraction of information is missing, for instance due to detector inefficiencies. Algorithms which provide a way to impute missing information have been developed over the past years. Among the various approaches, we focused on normal mixtures’ models in comparison with standard mean imputation and multiple imputation methods. Further, to account for the intrinsic asymmetry of the energy loss data, we considered skew-normal mixture models and provided a closed form implementation in the Expectation-Maximization (EM) algorithm framework to handle missing patterns. The method has been applied to a test case where the energy losses of pions, kaons and protons in a six-layers’ Silicon detector are considered as input neurons to a neural network. Results are given in terms of reconstruction efficiency and purity of the various species in different momentum bins.

Investigation on the energy loss in low energy protons interacting with hydrogen plasma

Energy loss of protons with energy 100 keV penetrating the partially ionized hydrogen plasma target was measured. The plasma target was created by electric discharge in the hydrogen gas, the state of the plasma target was diagnosed by using the laser interferometry method: the free electron density is up to 1016 cm-3, temperature is about 1-2 eV, and the plasma target may exist at the microsecond level. It is found that the energy loss of protons is closely related to the free electron density, and the energy loss data enable us to infer the value of the Coulomb logarithm (10.8) for the stopping power of the free electrons. This agrees well with the theoretical prediction which is 4.3 times higher than that given by the Bethe formula for neutral hydrogen, which is a little bigger than Hoffmann's result but much smaller than Jacoby's result. Comparing our result with Hoffmann's, the energy we used is only 100 keV, much lower than 1.4 MeV/u, and the low-energy regime we applied could be the cause of the increase in the enhancement factor. However, in the comparison between our result and the Jacoby's, the effective charge for protons is almost constant, unlike the Kr+ impact in wihch the enhanced ion charge state induces the giant enhancement factor. Compared to the gas target, the energy loss enhancement factor in plasma target is 2.9.

Recent results from telescope array

The Telescope Array (TA) is an experiment to observe Ultra-High Energy Cosmic Rays (UHECRs). TA's recent results, the energy spectrum and anisotropy based on the 6-year surface array data, and the primary composition obtained from the shower maximum Xmax are reported. The spectrum demonstrates a clear dip and cutoff. The shape of the spectrum is well described by the energy loss of extra-galactic protons interacting with the cosmic microwave background (CMB). Above the cutoff, a medium-scale (20 degrees radius) flux enhancement was observed near the Ursa-Major. A chance probability of creating this hotspot from the isotropic flux is 4.0 sigma. The measured Xmax is consistent with the primary being proton or light nuclei for energies 10^18.2 eV - 10^19.2 eV.

Energy loss of charm quarks from J/ψ production in cold nuclear matter

J/ψ suppression in p-A collisions is studied by considering the nuclear effects on parton distribution, energy loss of beam proton and the finial state energy loss of color octet cc̄. The leading-order computations for J/ψ production cross-section ratios RW/Be(xF) are presented and compared with the selected E866 experimental data with the cc̄ remaining colored on its entire path in the medium. It is shown that the combination of the different nuclear effects accounts quite well for the observed J/ψ suppression in the experimental data. It is found that the J/ψ) suppression on RW/Be(xF) from the initial state nuclear effects is more important than that induced by the energy loss of color octet cc̄ in the large xF region. Whether the cc̄ pair energy loss is linear or quadratic with the path length is not determined. The obtained cc̄ pair energy loss per unit path length α=2.78±0.81 GeV/fm, which indicates that the heavy quark in cold nuclear matter can lose more energy compared to the outgoing light quark.

Braking formula for electrons of relativistic speed

From the theory of Moller [Moller, Chr. 1931. Uber den Stos zweier Teilchen unter Berucksichtigung der Retardation der Krafte. Zeitschrift f. Phys. 70: 786–795] the energy loss of electrons with relativistic speeds passing through matter is derived. The energy loss per centimeter of distance reaches a minimum at about 96% of the speed of light and increases again at higher speeds; for electrons of several billion Volt it is about 4 million Volt per centimeter of water. A table of the theoretical energy loss for electrons and protons of various speeds is given.

Forward–backward correlated secondary electron emission depending on the emergence angle of 1 MeV/u light ions

The statistical distributions of the number of forward- and backward-emitted secondary electrons (SE’s) from a thin carbon foil have been measured simultaneously in coincidence with foil-transmitted 1H+, 4He2+ and 6Li3+ at a fixed velocity of 1MeV/u. The emergence angles of the projectiles, θem, were varied from 0 to 2 [mrad] for H+ and from 0 to 1 [mrad] for He2+ and Li3+ ions. Irrespective of ion species, measured total SE yields, that is, the average number of simultaneous emitted electrons per projectile, increase with increasing θem both in the forward and backward directions. This trend is consistent with the calculated θem-dependent energy losses of protons penetrating a thin carbon foil. As for the forward- or backward-emitted SE yields, we have obtained a negative forward–backward(F–B) correlation, except for the θem=0.0 [mrad] emergence of H+ projectiles where a positive correlation has been observed. The negative F–B correlation becomes prominent with increasing the atomic number of the projectile, Zp. In addition, this correlation appears to become slightly stronger with increasing θem. The observed F–B correlation and its Zp- and θem-dependences are interpreted from the point of view of production of high energy internal SE’s.

Energy loss of protons and He2+ beams in plasmas

&lt;div&gt; &lt;p&gt;In this work, the stopping power due to free and bound electrons in a plasma target is analyzed for two different kinds of projectile, protons and alpha particles. The stopping of free electrons is calculated using the dielectric formalism, well described in previous literature. In the case of bound electrons, Hartree-Fock methods and oscillator strength functions are used. The ionization degree of the plasma target is calculated using the Saha equation. Differences between the two methods of calculations for bound electrons are shown in noble gases. The influence of ionization is also estimated for argon plasma. Finally, we compare our calculations with two experiments. In the first one the stopping is calculated for protons in polyethylene plasma, and the second one the stopping is obtained for alpha particles in hydrogen plasma. In both cases, a good agreement with the experimental data is found.&lt;/p&gt; &lt;/div&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

TH-C-19A-01: Analytic Design Method to Make a 2D Planar, Segmented Ion Chamber Water-Equivalent for Proton Dose Measurements

Purpose: Quality Assurance (QA) measurements of proton therapy fields must accurately measure steep longitudinal dose gradients as well as characterize the dose distribution laterally. Currently, available devices for two-dimensional field measurements perturb the dose distribution such that routine QA measurements performed at multiple depths require multiple field deliveries and are time consuming. Methods: A design procedure for a two-dimensional detector array is introduced whereby the proton energy loss and scatter are adjusted so that the downstream dose distribution is maintained to be equivalent to that which would occur in uniform water. Starting with the design for an existing, functional two-dimensional segmented ion chamber prototype, a compensating material is introduced downstream of the detector to simultaneously equate the energy loss and lateral scatter in the detector assembly to the values in water. An analytic formalism and procedure is demonstrated to calculate the properties of the compensating material in the general case of multiple layers of arbitrary material. The resulting design is validated with Monte Carlo simulations. Results: With respect to the specific prototype design considered, the results indicate that a graphite compensating layer of the proper dimensions can yield proton beam range perturbation less than 0.1mm and beam sigma perturbation less than 2% across the energy range of therapeutic proton beams. Conclusion: We have shown that, for a 2D gas-filled detector array, a graphite-compensating layer can balance the energy loss and multiple Coulomb scattering relative to uniform water. We have demonstrated an analytic formalism and procedure to determine a compensating material in the general case of multiple layers of arbitrary material. This work was supported by the US Army Medical Research and Materiel Command under Contract Agreement No. DAMD17-W81XWH-04-2-0022. Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the US Army.

SU-E-T-623: Delivery of 3D Conformal Proton-Therapy Fields at Extended Source- To-Axis Distances

Purpose: To evaluate the dosimetric properties of proton dose distributions delivered at extended source-to-skin distances (SSD). Methods: Radiation was delivered with a gantry-mounted proton double scattering system (Proteus 230, IBA). This system has a maximum field diameter of 24 cm at isocenter and a nominal source-to-axis distance of 230 cm. Dose was measured at nominal SSD as well as at -10, +10, +25, +50, +75, and +100 cm for several range and modulation width combinations. Depth dose distributions were measured with a multi-layer ionization chamber (MLIC), and lateral dose distributions with a 2D ionization chamber array as well as with a diode in a water phantom. Results: The maximum field diameter was found to increase from 24.0 cm at nominal SSD to 29.1 cm and 33.3 cm at +50 cm and +100 cm respectively. Field flatness remained below 3% for all SSD. Tilt in the spread-out Bragg peak depth dose distribution increased with SSD up to 0.4 %-per-g/cm2 at +100 cm. The measured range decreased with 1.1×10-3 g/cm2 per centimeter shift in SSD due to proton energy loss in air, very close to the theoretically calculated value of 1.06×10-3 g/cm3. The output and dose rate decrease with the inverse of the SSD squared as expected. Conclusion: Extending the SSD up to 100 cm increases the maximum field diameter from 24.0 cm to 33.3 cm while the dose uniformity remains acceptable.

Enhancement of AlGaN/GaN High Electron Mobility Transistor Off-State Drain Breakdown Voltage via Backside Proton Irradiation

Proton irradiations from the backside of the AlGaN/GaN high electron mobility transistors (HEMTs) were employed to enhance its off-state drain breakdown voltage. Via holes were fabricated directly under the active area of the HEMTs by etching through the Si substrate for the backside irradiations. The steep drop at the end of proton energy loss profile allows radiation-induced defects to be placed at precise locations within the AlGaN/GaN HEMT structure. Neither degradation of drain current nor enhancement of off-state drain voltage breakdown voltage was observed for the HEMTs irradiated with the proton energy of 225 or 275 keV, for which the defects were put in the GaN buffer. HEMTs with defects placed in the two dimensional electron gas (2DEG) channel region and the AlGaN barrier, using 330 or 340 keV irradiations, not only showed degradations on drain current and extrinsic transconductance but also demonstrated improvements of the off-state drain breakdown voltage.

Enhancement of AlGaN/GaN high electron mobility transistors off-state drain breakdown voltage via backside proton irradiation

Proton irradiation from the backside of the samples were employed to enhance off-state drain breakdown voltage of AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates. Via holes were fabricated directly under the active area of the HEMTs by etching through the Si substrate for subsequent backside proton irradiation. By taking the advantage of the steep drop at the end of proton energy loss profile, the defects created by the proton irradiation from the backside of the sample could be precisely placed at specific locations inside the AlGaN/GaN HEMT structure. There were no degradation of drain current nor enhancement of off-state drain voltage breakdown voltage observed for the irradiated AlGaN/GaN HEMTs with the proton energy of 225 or 275 keV, for which the defects created by the proton irradiations were intentionally placed in the GaN buffer. HEMTs with defects placed in the two dimensional electron gas (2DEG) channel region and AlGaN barrier using 330 or 340 keV protons not only showed degradation of both drain current and extrinsic transconductance but also exhibited improvement of the off-state drain breakdown voltage. The Florida Object Oriented Device and Process Simulator Technology Computer Aided Design finite-element simulations were performed to confirm the hypothesis of a virtual gate formed around the 2DEG region to reduce the peak electric field around the gate edges and increase the off-state drain breakdown voltage.

Numerical investigation of non-ionizing energy loss of proton at an energy range of 300 eV to 1 GeV in silicon

The displacement damage due to non-ionizing energy loss (NIEL) is the main reason of photo-electronic device failure in space radiation environment. The basic mechanisms of NIEL are Coulomb and nuclear interactions of silicon atoms with incident protons at energies ranging from threshold to 1 GeV. In the low energy region where the Coulomb interaction is dominant, the NIEL can be calculated by analytical method and TRIM code. MCNPX/HTAPE3X is used to calculate NIEL when the nuclear elastic and non-elastic interactions between proton and target atoms are significant in the high energy range. The results show that it is reasonable to use MCNPX/HTAPE3X to evaluate the NIEL by recoiling nucleus caused by high energy protons. The combination of analytical method and TRIM code can calculate NIEL induced by Coulomb interaction in low energy range, which gives the NIEL of proton in silicon in an energy range from 300 eV to 1 GeV.

PARSEC: A parametrized simulation engine for ultra-high energy cosmic ray protons

We present a new simulation engine for fast generation of ultra-high energy cosmic ray data based on parametrizations of common assumptions of UHECR origin and propagation. Implemented are deflections in unstructured turbulent extragalactic fields, energy losses for protons due to photo-pion production and electron-pair production, as well as effects from the expansion of the universe. Additionally, a simple model to estimate propagation effects from iron nuclei is included. Deflections in the Galactic magnetic field are included using a matrix approach with precalculated lenses generated from backtracked cosmic rays. The PARSEC program is based on object oriented programming paradigms enabling users to extend the implemented models and is steerable with a graphical user interface.