Proton Energy Interval Research Articles

Dosimetry calculations of involved and noninvolved organs in proton therapy of liver cancer: a simulation study

Radiation for targeting liver tumors can be challenging because of the damage that it can cause to sensitive organs such as heart and kidney. To calculate the dose received by noninvolved organs, a modeling of the patient’s entire body is necessary. Therefore, in this study, a human Oak Ridge National Laboratory-Medical Internal Radiation Dose phantom was used for liver proton therapy simulation. The results show that the optimum proton energy interval covering the whole tumor was in the range of 90–120 MeV. A spread-out Bragg peak was built by adding Bragg peaks to cover the liver tumor volume, and beam parameters recommended by the International Commission on Radiation Units and Measurements (ICRU) were evaluated. The flux of secondary particles was calculated on the surface of the tumor, and two-dimensional dose distributions for protons, neutrons and photons were shown. Finally, the total doses of protons, photons and neutrons in tumor and 14 noninvolved organs were calculated. The results indicated that the ratio of received dose to the normal tissue of the liver concerning the spherical tumor of 2 cm in radius was approximately 0.01. This ratio for organs such as gall bladder, heart and kidney was approximately 8.4 × 10−5, 5.1 × 10−5 and 2.34 × 10−5. Secondary particles such as neutrons and photons deposit their energies to organs located far from the treatment volume, thus increasing the risk of secondary cancers. The research results indicated that the secondary particles dose was quite small in liver proton therapy. All the calculations were performed using Monte Carlo N-Particle Transport Code (MCNP).

Proton and deuteron activation measurements at the NPI and future plans in SPIRAL2/NFS

The proton- and deuteron-induced reactions are of a great interest for the assessment of induced radioactivity of accelerator components, target and beam stoppers as well as isotope production for medicine. In the present work, the deuteron-induced reaction cross sections on zinc were investigated by stacked-foil activation technique with deuteron beam of 20 MeV energy from the cyclotron U-120M of NPI CAS Řež. Also the proton activation cross section measurement of iron is presented. The comparison of present results to data of other authors and to predictions of evaluated data libraries is discussed. The investigation shall continue for higher proton and deuteron energy interval 20–35 MeV at SPIRAL2/NFS facility using a charged particle irradiation chamber with pneumatic transport system to measure isotopes and isomers with half-lives in minutes-regions.

Calculation of energy deposition, photon and neutron production in proton therapy of thyroid gland using MCNPX

In this study, the MCNPX code has been used to simulate a proton therapy in thyroid gland, in order to calculate the proton energy deposition in the target region. As well as, we have calculated the photon and neutron production spectra due to proton interactions with the tissue. We have considered all the layers of tissue, from the skin to the thyroid gland, and an incident high energy pencil proton beam. The results of the simulation show that the best proton energy interval, to cover completely the thyroid tissue, is from 42 to 54 MeV, assuming that the thyroid gland has a 14 mm thickness and is located 11.2mm under the skin surface. The most percentage of deposited energy (78%) is related to the 54 MeV proton energy beam. Total photon and neutron production are linear and polynomial second order functions of the proton energy, respectively.

Tentative level diagram of146Pm below 1.1 MeV

The level scheme of the doubly odd nucleus146Pm was investigated by means of in-beam spectroscopy. The146Nd(p, n) reaction in the 3.5–8 MeV proton energy interval on enriched targets has been used to populate the exited states of146Pm. High resolutionγ-ray spectra using Ge(Li) and hyperpure Ge detectors and conversion electrons with a mini-orange spectrometer were measured. Withγ-exitation functions andnγ-coincidences usingnγ-discriminated NE231 neutron detectors transitions in146Pm were identified,γγ-coincidences gave information aboutγ-cascades. With these data a level scheme of 38 levels below 1.1 MeV exitation energy has been deduced including 73 transitions. For 12 transitions experimental conversion coefficients have been evaluated, which agree with the expected values forM1/E2-transitions.

Studies of the gamma-strength function and low energy levels in 65Ga using the (p, γ) average resonance method

The 64Zn(p, γ) 65Ga reaction has been studied in the proton energy ranges E p = 2.0–2.9 and 3.3–4.3 MeV. Using a three-crystal pair spectrometer, gamma-ray spectra of primary transitions were measured throughout this proton energy interval in steps of about 20 keV. An average gamma ray spectrum for each energy region was formed by adding all the relevant individual spectra after adjustment due to the change of the proton energy. In the excitation energy range 0.0–3.7 MeV 50 levels, of which 20 are new, were observed. The gamma strength function was deduced from the average intensities of the primary gamma-rays. The absolute value of the strength function was found to be 5–10 times smaller than that expected from the extrapolation of the lorentzian shape of the El giant resonance.

The measurement of the asymmetry of tensor-polarized deuteron electrodisintegration at 180 MeV electron energy

The nucleon emission asymmetry in → d(e, pn)e′ reaction was measured using the tensor-polarized deuterium jet target in the VEPP-2 electron storage ring. At the present experimental accuracy, the results for the proton energy interval E p = 12–100 MrmMeV do not contradict the nonrelativistic calculations.

Measurements of relative thick target yields for PIGE analysis on light elements in the proton energy interval 2.4–4.2 MeV

In order to extend the energy range of the systematic investigation on relative thick target yields performed by ANTTILA et al2 for 1≤Ep≤2.4 MeV bombarding energies, gamma spectra and yield data are presented for elements Z=3–9, 11–17, 19–21 in the energy range 2.4≤Ep≤4.2 MeV and the results are discussed from the point of view of PIGE analysis.

Proton capture byN15above the giant dipole resonance

The proton capture cross sections to the ground and excited states of /sup 16/O have been measured at several angles in the proton energy interval between 18 and 40 MeV. The ground state angular distribution, which shows a significant E1-E2 interference effect above 40 MeV, results in reasonable agreement with semidirect capture calculations. Transitions to final bound and unbound 1p-1h states in /sup 16/O having a dominant 1p/sub 1/2//sup -1/ hole have also been measured. Resonances built on these residual states have been systematically observed above E/sub p/ = 20 MeV; the possible interpretation of these states as giant dipole resonances built on excited states is discussed.

Proton capture by 11B above the giant resonance

The cross sections for proton capture by 11B to the ground and excited states of 12C have been measured in the proton energy interval between 18 and 43 MeV. The ground-state cross section shows good agreement with theoretical calculations including correlations. Capture photons have also been observed to all the residual 1p-1h states of 12C having a dominant 1 p −1 3 2 hole: the corresponding cross sections systematically show a giant resonance whose energy increases with the increasing excitation energy of the “background” level. The resonances at 27.4, 31, 33.2, 37 and 43 MeV, seem to show observable interference effects.

Possible calibration errors for 81Rb 81 mKr generators due to a dual production route of 81Rb

A quantitative description is given for the 81Rb activity during and after production of 81Rb via the bombardment of krypton gas with protons, involving the direct reaction 82Kr( p, 2n) 81Rb and the indirect reaction 82Kr(p, 2n) 81 m Rb ▪ 81Rb. The ratio of the yields of both reactions has been determined experimentally for the proton energy interval 24 → 23 MeV. A calculation is given of the possible errors in the calibration of 81 Rb 81 m Kr generators, when the delayed production of 81Rb via the decay from the parent radionuclide 81 m Rb is not properly accounted for.

Gamma-ray strength function measurement for 63Cu

The 62Ni(p, γ) 63Cu reaction has been studied in the proton energy range E p = 1.9–2.4 MeV. Using a three-crystal pair spectrometer, γ-ray spectra of primary transitions have been measured throughout this proton energy interval in steps of about 4 keV. An average γ-ray spectrum was formed by adding all the individual spectra after proper adjustment as a result of the alterations in proton energy. From the average intensities of the primary γ-rays the γ-ray strength function for energies between 5 and 8 MeV was deduced. It was found that the values of the γ-ray strength function, in the region investigated, display a much steeper slope than the giant dipole resonance predicts.

Investigation of the γ-ray strength function in 51V by means of the average resonance method

A three-crystal pair spectrometer has been used to study the 50Ti(p, γ) 51V reaction for E p = 2.1–2.5MeV and2.6–3.1MeV The γ-ray spectra were measured throughout the proton energy interval in steps of about 15 keV. These spectra were added to get only one averaged spectrum. The intensities of high-energy γ-transitions populating the low-excited states of 51V have been determined. The intensities of the γ-rays to final states with known J π values were tested against theoretical calculations based on the Hauser-Feshbach theory with good results. The γ-ray strength function for energies lower than 11 MeV has been evaluated from the measured average intensities of primary γ-rays.

A scattering chamber for use with cooled large area lithium-compensated silicon radiation detectors

A scattering chamber designed to be used with large area, lithium-compensated silicon radiation detectors has been constructed. The chamber has provision for cooling a circular array of detectors to 77°K to achieve shorter charge collection time and better energy resolution than could be obtained with room temperature operation. The apparatus was designed to be used with the NBS 180-MeV synchrotron in photoproton experiments in the 2–35 MeV proton energy interval.

Polarization in the Elastic Scattering of Protons from Carbon and Nitrogen

The polarization of protons elastically scattered from nitrogen and carbon has been measured using double-scattering techniques. The polarization was determined for nitrogen at a scattering angle of 48\ifmmode^\circ\else\textdegree\fi{} c.m. in the proton-energy interval 12.6 to 13.6 MeV. The polarization resulting from elastic proton scattering with nitrogen targets had a constant value of -0.60\ifmmode\pm\else\textpm\fi{}0.10 in the incident proton-energy interval 8.2 to 11.8 MeV. The polarization from carbon, however, varied markedly with energy at most scattering angles. [Example: $P({50\ifmmode^\circ\else\textdegree\fi{}}_{\mathrm{lab}},12.9 \mathrm{MeV})=\ensuremath{-}0.8$, $P(50\ifmmode^\circ\else\textdegree\fi{},13.2)=\ensuremath{-}0.4$, and $P(50\ifmmode^\circ\else\textdegree\fi{},13.5)=\ensuremath{-}0.7$.] At numerous angles between 20\ifmmode^\circ\else\textdegree\fi{} and 140\ifmmode^\circ\else\textdegree\fi{}, polarization measurements from carbon covered the range of energies from 12.8 to 13.4 MeV. The angular distributions of polarization (and cross section) are in general quite sensitive to small changes in energy; the 12.95- and 13.25-MeV angular distributions even differ in shape significantly for $\ensuremath{\theta}>90\ifmmode^\circ\else\textdegree\fi{}$. The energy-averaged (12.8- to 13.4-MeV) angular distribution for the polarization of protons scattered from carbon was compared with optical-model calculations.

Radiochemical study of nuclear reactions leading to π-meson production

A radiochemical method has been used to study ( p, π ±) and ( p, pπ +) reactions with medium weight target nuclei. A marked rise in the cross-sections of these reactions was observed for incident protons having energies between 110 and 480 MeV and the cross-sections reached values of about 10 −30 cm 2/nucleon in the proton energy interval 480–660 MeV. Similar reactions with heavy elements could not be detected and attempts to identify the products of the reaction Cu( p,2 π- ±) also failed. The possible occurrence of ( p, π ±) reactions with nucleon complexes is discussed.

Secondary nuclear reactions induced in tin by fast protons

Nuclear reactions in which spallation products are captured by the target nucleus have been studied by the radio-chemical method. The excitation functions of secondary reactions leading to product nuclei having charges 2 or 3 units greater than that of the target nuclei have been obtained from measurements of the yields of isotopes of tellurium (Z = 52) and iodine (Z = 53) formed in the 170–660 MeV proton bombardment of tin (Z = 50). The cross-sections of these reactions increase with increasing proton energy: for Ep = 170 MeV, σ(α, xn) and σ(Li, xn) are 18·5 ± 5 and 0·17 ± 0·1 μbarns, respectively; for Ep = 660 MeV, these cross-sections are 50 ± 6·5 and 1·6 ± 0·5 μbarns, respectively. The cross-sections for the capture of lithium nuclei by tin obtained in this work are in good agreement with the results for similar reactions with copper, tin, and lead over a comparable proton energy interval but they are 50 times less than the cross-sections found by Marquez and Perlman. The observed secondary reaction cross-sections for the capture of lithium nuclei can be accounted for only by supposing that the lithium nuclei are emitted with energies greater than they could acquire as a result of fission or evaporation of the target nucleus. Secondary reactions of the type (α, xn) can be accounted for by assuming that the m-particles are emitted as a result of the evaporation process.

Energy Dependence ofF19+pReactions

Excitation functions have been obtained for the ${\mathrm{F}}^{19}(p, \ensuremath{\alpha}\ensuremath{\pi}){\mathrm{O}}^{16}$, ${\mathrm{F}}^{19}(p, {\ensuremath{\alpha}}_{0}){\mathrm{O}}^{16}$, ${\mathrm{F}}^{19}(p, \ensuremath{\alpha}\ensuremath{\gamma}){\mathrm{O}}^{16}$, and ${\mathrm{F}}^{19}(p, {p}^{\ensuremath{'}}\ensuremath{\gamma}){\mathrm{F}}^{19}$ reactions for proton energies of 1.2 to 5.4 Mev. The marked similarity of the pair and long-range alpha excitation functions is noted and in the proton energy interval 1.35 to 2.33 Mev the differences between the yields are explained by the penetration factors for alpha particles emitted from the excited states of ${\mathrm{Ne}}^{20}$. The average reaction cross section has been obtained for the ${\mathrm{F}}^{19}$+$p$ reactions by averaging the excitation functions over one-half Mev intervals. The result is compared to the cross section given by the continuum theory.

FAST NEGATIVE HYDROGEN IONS

A proton beam was directed through hydrogen gas at low pressure and magnetic analysis of the emergent beam showed that an appreciable fraction of the beam was transformed into negative hydrogen ions. After the beam had traversed a sufficient layer of gas, the ratio of negative hydrogen ions to protons reached an equilibrium value which was a maximum of 22.2% at 8.5 kev. The proton energy interval investigated extended from 4 to 70 kev.In this interval the electron loss cross section for negative hydrogen ions was measured and found to vary from 6.3 × 10−16 sq. cm. at 4.2 kev. to 2.5 × 10−10 sq. cm. at 70.3 kev. The electron capture cross section for protons in hydrogen was measured over the same interval and the results agreed substantially with those of other workers. The electron capture cross section for neutral atoms was also determined by combining present results for the negative ion loss cross section and for the equilibrium ratio of H− to H+ with the values of Bartels and of Montague and Ribe for the ratio of neutral atom loss cross section to the proton capture cross section.