Intense Proton Beam Research Articles

Efficient production and diagnostics of MeV proton beams from a cryogenic hydrogen ribbon

A solid hydrogen thin ribbon, produced by the cryogenic system ELISE (Experiments on Laser Interaction with Solid hydrogEn) target delivery system, was experimentally used at the PALS kJ-laser facility to generate intense proton beams with energies in the MeV range. This sophisticated target system operating at cryogenic temperature (∼ 10 K) continuously producing a 62 μm thick target was combined with a 600 J sub-nanosecond laser pulse to generate a collimated proton stream. The accelerated proton beams were fully characterized by a number of diagnostics. High conversion efficiency of laser to energetic protons is of great interest for future potential applications in non-conventional proton therapy and fast ignition for inertial confinement fusion.

Incidence and Predictors of Pericardial Effusion After Chemoradiation Therapy for Locally Advanced Non-Small Cell Lung Cancer

Findings from Radiation Therapy Oncology Group (RTOG) 0617 suggested that collateral radiation to the heart may contribute to early death in patients receiving chemoradiation therapy for non-small cell lung cancer (NSCLC); however, reports of cardiac toxicity after thoracic radiation therapy (RT) remain limited. Because pericardial disease is the most common cardiac complication of thoracic RT, we investigated the incidence of and risk factors for pericardial effusion (PCE) in patients enrolled in a phase 2 prospective randomized study of intensity modulated RT versus proton therapy for locally advanced NSCLC. From July 2009 through April 2014, 201 patients were prospectively treated with proton beam therapy or intensity modulated RT to 60 to 74Gy with concurrent chemotherapy. The primary endpoint (grade ≥2 PCE) was diagnosed on review of follow-up images. Clinical characteristics and cardiac dose-volume parameters associated with PCE were identified via Cox proportional hazards modeling and recursive partitioning analysis of null Martingale residuals. Reproducibility was evaluated in a separate retrospective cohort of 301 patients. The cumulative incidence rates of PCE among patients in the trial were 31.4% at 1year and 45.4% at 2years, with a median time to PCE of 8.9months. Several cardiac dose-volume parameters (eg, V20 [volume receiving ≥20Gy] to V65 [volume receiving ≥65Gy]) predicted PCE, but heart volume receiving ≥35Gy (HV35) was the most strongly associated, with a cutoff volume of 10%.On multivariate analysis, HV35>10% independently predicted PCE (hazard ratio [HR], 2.14; P=.002), a finding that maintained reproducibility in the retrospective validation cohort. Other factors associated with PCE included receipt of adjuvant chemotherapy (HR, 2.82; P<.001) and prior cardiac disease (HR, 1.68; P=.020). PCE was common after RT for NSCLC, occurring in nearly half of patients even after moderate radiation doses to the heart. Adjuvant chemotherapy may increase the risk of PCE, and HV35>10% may identify patients at risk of development of this cardiac toxicity.

Neutron spectral fluence measurements using a Bonner sphere spectrometer in the development of the iBNCT accelerator-based neutron source

The neutron spectral fluence of an accelerator-based neutron source facility for boron neutron capture therapy (BNCT) based on a proton linac and a beryllium target was evaluated by the unfolding method using a Bonner sphere spectrometer (BSS). A 3He-proportional-counter-based BSS was used with weak beam during the development of the facility. The measured epithermal neutron spectra were consistent with calculations. The epithermal neutron intensity at the beam port was estimated and the results gave a numerical target for the enhancement of the proton beam intensity and will be used as reference data for measurements performed after the completion of the facility.

First Experiments at the CW-Operated RFQ for Intense Proton Beams

First Experiments at the CW-Operated RFQ for Intense Proton Beams

Splitting of a high-energy positively-charged particle beam with a bent crystal

The possibility of high-energy positively-charged particle beam splitting by means of a short bent axially oriented silicon crystal was recently reported in an experiment carried out at CERN SPS H8 extracted line with a 400GeV/c proton beam. Here, we investigate more deeply such a possibility focusing our attention on the efficiency of beam splitting and its modulation for different crystal-to-beam orientations. New experimental results confirm the possibility of modulating the 400GeV/c proton beam intensity in different planar channels by adjusting the orientation of the crystal. Furthermore, an analysis of the beam splitting efficiency vs. the curvature of the crystal was carried out through simulation, highlighting that there exists a bending radius for which the efficiency is maximal.

Experimental results and strength model identification of pure iridium

Intense and high energy proton beams are impacted with fixed materials (targets) in order to produce new particles and secondary beams at CERN. In some of these targets, the requirement of reaching high yield production of secondary particles points out to the use of high density materials. The interaction of the beam with the atoms and nuclei of these materials produce extremely fast depositions of energy, highly soliciting them from thermo-structural point of view due to subsequent rise of temperature and pressure waves. Iridium is a good candidate material since exhibits very high density, high melting point, good strength and stability at high temperature, and resistance to thermal shock.The main goal of this study is the investigation of the mechanical behaviour at different temperatures and strain-rates in tensile loading condition of pure iridium. A series of tests at room temperature at different strain-rates (from 10−3 s−1 up to 104 s−1) was performed in order to obtain information about strain and strain-rate sensitivity of the material. In addition, a series of tests at different temperatures in both quasi-static and high strain-rate loading conditions was performed in order to obtain information about the thermal softening of the material (from room temperature up to 1250 °C). The experimental data were used to identify a strength model able to predict the material behaviour over wide ranges of variation of the variables of interest.

The impact of proton beam therapy on blood cell count nadir during neoadjuvant chemoradiation therapy for esophageal cancer.

137 Background: To analyze the blood cell count nadir, particularly grade 4 hematologic toxicities, in patients with esophageal cancer who were treated with neoadjuvant chemoradiation (nCRT) with either Proton Beam Therapy (PBT) or Intensity Modulated Radiation Therapy (IMRT) in a propensity-matched pair analysis. Methods: Esophageal cancer patients (n = 480) treated from 2005-2016 with nCRT with (n = 167) or without (n = 313) induction chemotherapy (ICT) were analyzed. White blood cell, neutrophil, lymphocyte and platelet counts nadir during ICT and CRT were obtained, and graded according to the CTCAE v.4.0. Univariate and multivariable logistic regression models to identify factors associated with increased risk of grade 4 lymphopenia were fitted. By propensity score matching, 136 PBT cases and 136 propensity score matched IMRT controls were selected for comparison. Results: In the entire study cohort during CRT (n = 480), 2 (0.4%), 1 (0.2%), 159 (33%), and 2 (0.4%) patients experienced grade 4 leukopenia, neutropenia, lymphopenia and thrombocytopenia, respectively. This is not seen in patients who received ICT (n = 167), as only 0 (0%), 2 (1.2%), 1 (0.6%) and 0 (0%) patients experienced grade 4 leukopenia, neutropenia, lymphopenia and thrombocytopenia during the ICT phase. Multivariable analyses identified older age (p = 0.0139), larger planning tumor volume (PTV) (p = 0.0213), distal vs upper/mid tumor location (borderline significance, p = 0.0779) and IMRT vs PBT (p &lt; 0.0001) as factors associated with increased risk of grade 4 lymphopenia during CRT. Among the 272 propensity-matched patients treated with either PBT or IMRT, 24 (17.6 %) and 55 (40.4 %) patients experienced grade 4 lymphopenia, respectively (p &lt; 0.001). Grade 4 lymphopenia correlates with poorer survival (p = 0.0587), lower progression free survival (p = 0.0384) and distant metastatic recurrence (p = 0.0185). Conclusions: The use of PBT may be an important modifying factor in altering the incidence of grade 4 lymphopenia during CRT in esophageal cancer. The dosimetric factors that can modulate this risk is a subject of continued investigation.

Nuclear microprobe performance in high-current proton beam mode for micro-PIXE

The performance of a nuclear microprobe is dominantly determined by the brightness of the injected ion beam. At Jožef Stefan Institute (JSI), negative hydrogen ion beams are created in a multicusp ion source and injected into a 2MV tandetron accelerator. The output characteristics of the multicusp ion source were tuned in order to obtain matching proton beam intensities for the ion accelerator and for the object slits as well. For the optimal focusing of the proton beam in a high-current mode (I>100pA) to the sub-micrometer dimensions, dedicated thin nanostructures with sharp edges have been manufactured. Set of nanostructures was micromachined by focused ion beam (FIB) at film reference material, produced by Institute for Reference Materials and Measurements (IRMM) and constituted of 57μg/cm2 of titanium on vitreous carbon substrate. The proton beam profiles were measured by beam scans across the nanostructures over long measuring times, indicating eventual slow drifts of the sample from a reference beam direction. Overall, proton beam dimensions of 600nm were obtained, demonstrating appropriate stability for micro-PIXE (micro-Particle Induced X-ray Emission) at sub-micrometer resolution for elemental analysis of biological tissue samples prepared in a freeze-dried state or in a frozen-hydrated state. The resulting performance required for micro-PIXE analysis in a high current mode with a 3MeV proton beam is presented.

Depth profiles of production yields ofnatPb(p, xn)206,205,204,203,202Bi reactions using 100-MeV proton beam

In this study, results of the experimental study on the depth profiles of production yields of 206,205,204,203,202 Bi radio-nuclei in the natural Pb target irradiated by a 100-MeV proton beam are presented. Irradiation was performed at proton linac facility (KOMAC) in Korea. The target, irradiated by 100-MeV protons, was arranged in a stack consisting of natural Pb, Al, Au foils and Pb plates. The proton beam intensity was determined by activation analysis method using 27 Al(p, 3p1n) 24 Na, 197 Au(p, p1n) 196 Au, and 197 Au(p, p3n) 194 Au monitor reactions and also using dosimetry method by a Gafchromic film. The production yields of produced Bi radio-nuclei in the natural Pb foils and monitor reactions were measured by gamma-ray spectroscopy. Monte Carlo simulations were performed by FLUKA, PHITS, and MCNPX codes and compared with the measurements in order to verify validity of physical models and nuclear data libraries in the Monte Carlo codes. A fairly good agreement was observed between the present experimental data and the simulations by FLUKA, PHITS, and MCNPX. However, physical models and the nuclear data relevant to the end of range of protons in the codes need to be improved.

Target characterizations for direct measurement of the 13C(α, n)16O reaction at LUNA 400

The 13 C(α , n)16 O reaction is the main neutron source for the s-process in low mass AGB stars. Although several direct measurements have been performed, no dataset reaches the Gamow window due to the low cross section. Moreover a dominant component of systematic uncertainty comes from target behaviour under beam irradiation.This work presents a detailed characterization of enriched 13 C targets in order to test reproducibility and uniformity of the evaporation method, stability and purity of targets under a high intensity proton beam (100-200 uA) for the study of this reaction at the Laboratory for Underground Nuclear Astrophysics (LUNA) facility installed at Laboratori Nazionali del Gran Sasso (LNGS, INFN). A procedure to evaluate the target thickness and to monitor its degradation is discussed and preliminary results are presented.

The LHC vacuum system: Commissioning up to nominal luminosity

The Large Hadron Collider (LHC), currently under operation at CERN, is colliding intense proton beams at the highest energy frontier up to ∼14 TeV in the centre of mass. This superconducting storage ring is at the origin of the discovery in 2012 of the so-called ‘Higgs’ Boson explaining the origin of the mass of weak bosons W+,W− and Z also discovered at CERN in 1983. The arc vacuum system, which operates at cryogenic temperatures, consists of a 1.9 K cold bore which houses a 5–20 K beam screen. Beam collisions are performed inside a Non-Evaporable-Getter coated vacuum system located in long straight sections held at room temperature. These vacuum systems were designed to be stable under ion bombardment, to cope with intense VUV synchrotron radiation flux and to mitigate beam induced multipacting effects. In this paper, the LHC beam vacuum system design is recalled. Its operation, challenges and achieved performances during the commissioning phase will be discussed in detail.

Reaching record-low [formula omitted] at the CERN Large Hadron Collider using a novel scheme of collimator settings and optics

The Large Hadron Collider (LHC) at CERN is built to collide intense proton beams with an unprecedented energy of 7TeV. The design stored energy per beam of 362MJ makes the LHC beams highly destructive, so that any beam losses risk to cause quenches of superconducting magnets or damage to accelerator components. Collimators are installed to protect the machine and they define a minimum normalized aperture, below which no other element is allowed. This imposes a limit on the achievable luminosity, since when squeezing β* (the β-function at the collision point) to smaller values for increased luminosity, the β-function in the final focusing system increases. This leads to a smaller normalized aperture that risks to go below the allowed collimation aperture. In the first run of the LHC, this was the main limitation on β*, which was constrained to values above the design specification. In this article, we show through theoretical and experimental studies how tighter collimator openings and a new optics with specific phase-advance constraints allows a β* as small as 40cm, a factor 2 smaller than β*=80cm used in 2015 and significantly below the design value β*=55cm, in spite of a lower beam energy. The proposed configuration with β*=40cm has been successfully put into operation and has been used throughout 2016 as the LHC baseline. The decrease in β* compared to 2015 has been an essential contribution to reaching and surpassing, in 2016, the LHC design luminosity for the first time, and to accumulating a record-high integrated luminosity of around 40 fb−1 in one year, in spite of using less bunches than in the design.

On intense proton beam generation and transport in hollow cones

Proton generation, transport and interaction with hollow cone targets are investigated by means of two-dimensional PIC simulations. A scaled-down hollow cone with gold walls, a carbon tip and a curved hydrogen foil inside the cone has been considered. Proton acceleration is driven by a 1020 W·cm−2 and 1 ps laser pulse focused on the hydrogen foil. Simulations show an important surface current at the cone walls which generates a magnetic field. This magnetic field is dragged by the quasi-neutral plasma formed by fast protons and co-moving electrons when they propagate towards the cone tip. As a result, a tens of kT Bz field is set up at the cone tip, which is strong enough to deflect the protons and increase the beam divergence substantially. We propose using heavy materials at the cone tip and increasing the laser intensity in order to mitigate magnetic field generation and proton beam divergence.

Direct measurement of low-energyNe22(p,γ)Na23resonances

The $^{22}$Ne(p,$\gamma$)$^{23}$Na reaction is the most uncertain process in the neon-sodium cycle of hydrogen burning. At temperatures relevant for nucleosynthesis in asymptotic giant branch stars and classical novae, its uncertainty is mainly due to a large number of predicted but hitherto unobserved resonances at low energy. Purpose: A new direct study of low energy $^{22}$Ne(p,$\gamma$)$^{23}$Na resonances has been performed at the Laboratory for Underground Nuclear Astrophysics (LUNA), in the Gran Sasso National Laboratory, Italy. Method: The proton capture on $^{22}$Ne was investigated in direct kinematics, delivering an intense proton beam to a $^{22}$Ne gas target. $\gamma$ rays were detected with two high-purity germanium detectors enclosed in a copper and lead shielding suppressing environmental radioactivity. Results: Three resonances at 156.2 keV ($\omega\gamma$ = (1.48\,$\pm$\,0.10)\,$\cdot$\,10$^{-7}$ eV), 189.5 keV ($\omega\gamma$ = (1.87\,$\pm$\,0.06)\,$\cdot$\,10$^{-6}$ eV) and 259.7 keV ($\omega\gamma$ = (6.89\,$\pm$\,0.16)\,$\cdot$\,10$^{-6}$ eV) proton beam energy, respectively, have been observed for the first time. For the levels at 8943.5, 8975.3, and 9042.4 keV excitation energy corresponding to the new resonances, the $\gamma$-decay branching ratios have been precisely measured. Three additional, tentative resonances at 71, 105 and 215 keV proton beam energy, respectively, were not observed here. For the strengths of these resonances, experimental upper limits have been derived that are significantly more stringent than the upper limits reported in the literature. Conclusions: Based on the present experimental data and also previous literature data, an updated thermonuclear reaction rate is provided in tabular and parametric form. The new reaction rate is significantly higher than previous evaluations at temperatures of 0.08-0.3 GK.

Radiation damage and thermal shock response of carbon-fiber-reinforced materials to intense high-energy proton beams

A comprehensive study on the effects of energetic protons on carbon-fiber composites and compounds under consideration for use as low-Z pion production targets in future high-power accelerators and low-impedance collimating elements for intercepting TeV-level protons at the Large Hadron Collider has been undertaken addressing two key areas, namely, thermal shock absorption and resistance to irradiation damage.

Optimization of a Beam Shaping Assembly Design for Boron Neutron Capture Cancer Therapy Facility Based on 30 MeV Cyclotron

A series of simulations has been carried out using a Monte Carlo N Particle X code to find out the final composition and configuration of a neutron Beam Shaping Assembly (BSA) to moderate the fast neutron flux which is generated from the thick disk-type beryllium target. The final configuration for neutron BSA design included 35 cm lead as reflector, 39 cm alumina as moderator, 8.2 cm lithium fluoride as fast neutron filter and 0.5 cm boron carbide as thermal neutron filter. Bismuth, lead fluoride, and lead were chosen as the aperture, reflector, and gamma shielding, respectively. The disk-type of beryllium target is 19 cm in diameter with 0.5 cm thickness which is covered by copper plate to hold the water pressured coolant. A higher yield of neutron production requires a higher intensity of proton beams, which generate much heats and causes the target material to melt. Therefore, it is useful to consider the temperature distribution on the target material with flowing water coolant by means of computer modeling while designing the target. ANSYS-Fluent code will be used to estimate the thermal transfer and heat calculation in a solid target during beam irradiation. Epithermal neutron flux in the suggested design were 1,03x10&lt;sup&gt;9&lt;/sup&gt; n/cm&lt;sup&gt;2&lt;/sup&gt; s, with almost all IAEA parameters for BNCT BSA design has been satisfied.

Depth profile of production yields of natPb(p, xn) 206,205,204,203,202,201Bi nuclear reactions

Experimental and simulation studies on the depth profiles of production yields of natPb(p, xn) 206,205,204,203,202,201Bi nuclear reactions were carried out. Irradiation experiments were performed at the high-intensity proton linac facility (KOMAC) in Korea. The targets, irradiated by 100-MeV protons, were arranged in a stack consisting of natural Pb, Al, Au foils and Pb plates. The proton beam intensity was determined by activation analysis method using 27Al(p, 3p1n)24Na, 197Au(p, p1n)196Au, and 197Au(p, p3n)194Au monitor reactions and also by Gafchromic film dosimetry method. The yields of produced radio-nuclei in the natPb activation foils and monitor foils were measured by HPGe spectroscopy system. Monte Carlo simulations were performed by FLUKA, PHITS/DCHAIN-SP, and MCNPX/FISPACT codes and the calculated data were compared with the experimental results. A satisfactory agreement was observed between the present experimental data and the simulations.

Methodology for the structural design of single spoke accelerating cavities at Fermilab

Fermilab is planning to upgrade its accelerator complex to deliver a more powerful and intense proton-beam for neutrino experiments. In the framework of the so-called Proton Improvement Plan-II (PIP-II), we are designing and developing a cryomodule containing superconducting accelerating cavities, the Single Spoke Resonators of type 1 (SSR1). In this paper, we present the sequence of analysis and calculations performed for the structural design of these cavities, using the rules of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC). The lack of an accepted procedure for addressing the design, fabrication, and inspection of such unique pressure vessels makes the task demanding and challenging every time. Several factors such as exotic materials, unqualified brazing procedures, limited nondestructive examination, and the general R&D nature of these early generations of cavity design, conspire to make it impractical to obtain full compliance with all ASME BPVC requirements. However, the presented approach allowed us to validate the design of this new generation of single spoke cavities with values of maximum allowable working pressure that exceeds the safety requirements. This set of rules could be used as a starting point for the structural design and development of similar objects.

Effect of strong solenoidal focusing on beam emittance of low-energy intense proton beam in the SARAF LEBT

Influence of strong solenoidal beam focusing on beam emittance was studied at the SARAF LEBT beam line using 5 mA 20 keV proton quasi-DC beams. The measurements show that within the experimental uncertainties, emittance does not change over the whole focusing range. Detailed beam dynamics simulations were performed to achieve better understanding of the experimental results. The experimental and simulation results are fully consistent with the assumption of nearly full space charge neutralization for the quasi-DC proton beam.

The mechatronic design of a fast wire scanner in IHEP U-70 accelerator

This paper presents the mechatronic design of a fast wire scanner based on a servomotor. The design of the wire scanner is motivated by the need to measure the transverse profile of the high power proton and carbon beams at the IHEP U-70 accelerator. This paper formulates the requirements to the fast wire scanner system for the high intensity proton beam at the U-70 accelerator. The results on the design of electro-mechanical device for the wire scanner with a wire traveling speed 10–20m/s are presented. The solution consists in a brushless servomotor and standard motor control electronics. High radiation levels in the accelerator enclosure dictate the use of a resolver as the position feedback element.