Cylindrical Target Research Articles

High energy density physics effects predicted in simulations of the CERN HiRadMat beam–target interaction experiments

Experiments have been done at the CERN HiRadMat (High Radiation to Materials) facility in which large cylindrical copper targets were irradiated with 440 GeV proton beam generated by the Super Proton Synchrotron (SPS). The primary purpose of these experiments was to confirm the existence of hydrodynamic tunneling of ultra-relativistic protons and their hadronic shower in solid materials, that was predicted by previous numerical simulations. The experimental measurements have shown very good agreement with the simulation results. This provides confidence in our simulations of the interaction of the 7 TeV LHC (Large Hadron Collider) protons and the 50 TeV Future Circular Collider (FCC) protons with solid materials, respectively. This work is important from the machine protection point of view.The numerical simulations have also shown that in the HiRadMat experiments, a significant part of thetarget material is be converted into different phases of High Energy Density (HED) matter, including two–phase solid–liquid mixture, expanded as well as compressed hot liquid phases, two–phase liquid–gas mixture and gaseous state. The HiRadMat facility is therefore a unique ion beam facility worldwide that is currently available for studying the thermophysical properties of HED matter. In the present paper we discuss the numerical simulation results and present a comparison with the experimental measurements.

In situ assessment of the roughness of a uniformly eroded cylindrical magnetron target

We present an experimental approach for the in situ characterization of the surface roughness of an eroded magnetron target based on the reflectance pattern of a laser beam. The surface of the eroded region was modeled as a random arrangement of tilted plane facets with large surface extensions as compared to the wavelength of the laser. A simple algorithm was used to reconstruct surface profiles form the reflected intensity values from the eroded surface. The surface profiles of Al, Cu and Ti targets were reconstructed under high vacuum conditions without disturbing the processing parameters of the magnetron sputtering plant. From these generated profiles, the roughness parameters, root mean square roughness, correlation length, skewness and kurtosis of different target materials were calculated by this in situ technique. The results measured with this in situ technique are in good agreement with comparable measurements using a mechanical profilometer outside the sputtering system. However, some deviation was observed for surfaces with higher roughness and mean tilt angles. This method can be used for in situ monitoring of sputter targets to extract the surface features which may correlate with thin film properties and may precede dangerous events like target melting or other catastrophic failures.

Simulation of microexplosion hydrodynamics in heavy ion fusion reactor chamber with wetted first wall

Thermonuclear fusion flare, fireball expansion, and evaporation of the liquid-film chamber wall are simulated by combining two one-dimensional (1D) codes DEIRA and RAMPHY. The considered process is divided into two phases: the DEIRA code is used to simulate the fast ignition and burn of a cylindrical target with DT fuel and a lead tamper, while the RAMPHY code is applied to describe the subsequent quasi-spherical expansion of the fireball. By the end of the first phase, the neutron and X-ray output from the target as well as the debris motion are determined. The fast ions are practically fully absorbed by the lead tamper of the fusion target. At the second stage, which starts with the arrival of the main shock at the target surface, the fireball expansion and the behavior of the wall liquid film are considered. The fireball front propagates with a velocity close to the self-similar value. The liquid film is first evaporated by the X-ray pulse, and then by the heat flux generated when the fireball collides with the primary vapor layer. Mechanical loading on the liquid film remains within the 100-MPa range.

A curved edge diffraction-utilized displacement sensor for spindle metrology.

This paper presents a new dimensional metrological sensing principle for a curved surface based on curved edge diffraction. Spindle error measurement technology utilizes a cylindrical or spherical target artifact attached to the spindle with non-contact sensors, typically a capacitive sensor (CS) or an eddy current sensor, pointed at the artifact. However, these sensors are designed for flat surface measurement. Therefore, measuring a target with a curved surface causes error. This is due to electric fields behaving differently between a flat and curved surface than between two flat surfaces. In this study, a laser is positioned incident to the cylindrical surface of the spindle, and a photodetector collects the total field produced by the diffraction around the target surface. The proposed sensor was compared with a CS within a range of 500 μm. The discrepancy between the proposed sensor and CS was 0.017% of the full range. Its sensing performance showed a resolution of 14 nm and a drift of less than 10 nm for 7 min of operation. This sensor was also used to measure dynamic characteristics of the spindle system (natural frequency 181.8 Hz, damping ratio 0.042) and spindle runout (22.0 μm at 2000 rpm). The combined standard uncertainty was estimated as 85.9 nm under current experiment conditions. It is anticipated that this measurement technique allows for in situ health monitoring of a precision spindle system in an accurate, convenient, and low cost manner.

Performance of MACACO Compton telescope for ion-beam therapy monitoring: first test with proton beams

In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing 22Na and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3–5 mm resolution. The two-layer Compton telescope was employed to measure radiation emitted from a beam of 150 MeV protons impinging on a cylindrical PMMA target. Bragg-peak shifts were achieved via adjustment of the PMMA target location and the resulting measurements used during image reconstruction. Reconstructed Bragg peak profiles proved sufficient to observe peak-location differences within 10 mm demonstrating the potential of the MACACO Compton Telescope as a monitoring device for ion-beam therapy.

An Airborne Ultrasonic Imaging System Based on 16 Elements: 150 kHz Piezopolymer Transducer Arrays—Preliminary Simulated and Experimental Results for Cylindrical Targets Detection

This paper describes the design and fabrication of a 16-element transducer array for airborne ultrasonic imaging operating at 150 kHz, that can operate both at close range (50 mm) in the near field of a synthetic aperture, and up to 250 mm. The proposed imaging technique is based on a modified version of the delay and sum algorithm implemented with a synthetic aperture where each pixel amplitude is determined by the integration of the signal obtained by the coherent summation of the acquired signals over a delayed window with fixed length. The image reconstruction methods using raw data provides the possibility to detect targets with smaller feature size on the order of one wavelength because the coherent signals summation over the selected window length while the image reconstruction methods using the summation of enveloped signals increases the amplitude response at the expenses of a lower spatial resolution. For the implementation of this system it is important to design compact airborne transducers with large field of view and this can be obtained with a new design of hemi-cylindrical polyvinylidene fluoride film transducers directly mounted on a printed circuit board. This new method is low cost and has repeatable transducer characteristics. The complete system is compact, with a modular architecture, in which eight boards with dual ultrasonic channels are mounted on a mother board. Each daughter board hosts a microcontroller unit and can operate with transducers in the bandwidth 40–200 kHz with on-board data acquisition, pre-processing and transfer on a dedicated bus.

SU-F-T-606: Monte Carlo Evaluation of Tissue Inhomogeneity Corrections in the Treatment of Liver Cancer Patients Using Stereotactic Body Radiotherapy

Purpose: To evaluate the dosimetric performance of X-ray Voxel Monte Carlo(XVMC) algorithm in effort to clinically validate Monte Carlo-approach in heterogeneous liver phantom and liver SBRT plans. Methods: An anthropomorphic RPC liver phantom incorporating a liver structure with two cylindrical targets and organs-at-risk (OARs) was used in phantom validation. Subsequently, five patients with metastatic liver cancer were treated using heterogeneity-corrected pencil-beam(PB-hete)algorithm were analyzed following RTOG-1112 criteria .ITV was delineated on MinIP and OARs were contoured on MeanIP images of 4D-CT. PTV was generated from ITV with 5-10mm uniform margin. Mean PTV was 81.3±46.4cc. Prescription was 30–45Gy in 5 fractions, with at least PTV(D95%)=100%. Hybrid SBRT plans were generated with noncoplanar/3D-conformal arcs plus static-beams at Novalis-TX consisting of HD-MLC and 6MV-SRS. SBRT plans were re-computed using XVMC algorithm utilizing identical beam-geometry, MLC-positions, and monitor units and subsequently compared to clinical PB-hete plans. Results: Our results using RPC liver motion phantom validation were all compliance with MD Anderson standards. However, compared to PB-hete, average target volume encompassed by the prescribed percent isodose (Vp) was 9.1% and 8.5% less for PTV1 and PTV2 with XVMC. For the clinical liver SBRT plans, PB-hete systematically overestimated PTV dose (D95, Dmean and D10) within ±2.0% (p<0.05) compared to XVMC. Mean value of Vp was about 3.8% less with XVMC compared to PB-hete (ranged 2.9–5.7% (p<0.003)). However, mean liver dose (MLD) was 3.2% higher (p<0.003), on average, with XVMC compared to clinical PB-hete (ranged −1.0to−3.9%). OARs doses were statistically insignificant. Conclusion: Results from our XVMC dose calculations and validation study for liver SBRT indicate small-to-moderate under-dosing of the tumor volume when compared to PB-hete. Results were consistent with phantom validation and patients plans. However, Vp was less by up to 5.7% for some liver SBRT patients with XVMC–suggesting under-dosing of the target volume and overdosing of MLD by up to 3.9% occurred with PB-hete plan. These differences between PB-hete and XVMC dose calculations may be of clinical interest.

Photon source term after single collision in targets of silicon, copper and lead for 50-500 keV X-ray beams.

Single-scattered X-ray doses at 1 m from silicon, copper and lead targets were calculated using an analytical point-kernel method considering the self-absorption, and the calculated values were compared with detailed results of a Monte Carlo calculation with respect to the emission angle. In the calculations, a slab slanted at 3° to the beam axis was used for silicon in addition to the cylindrical targets for the three materials, and the slab geometry showed the largest doses. The analytical calculations were underestimated compared with the Monte Carlo calculations by less than 24% for silicon and 40% for copper, particularly at large-angle scattering, which was attributable to the buildup effect of the single-scattered X-rays in the targets. By considering the buildup effect, the difference from Monte Carlo results decreased to less than 20%. For lead, the influence of fluorescent X-rays produced by the source beam was dominant in the backward direction, which was also calculated analytically. The simple analytical program can be applied to any target size and shape by considering self-absorption and the buildup effect, both of which inform the simple dose estimation method.

On-site calibration method for outdoor binocular stereo vision sensors

Using existing calibration methods for binocular stereo vision sensors (BSVS), it is very difficult to extract target characteristic points in outdoor environments under complex light conditions. To solve the problem, an online calibration method for BSVS based a double parallel cylindrical target and a line laser projector is proposed in this paper. The intrinsic parameters of two cameras are calibrated offline. Laser strips on the double parallel cylindrical target are mediated to calibrate the configuration parameters of BSVS. The proposed method only requires images of laser strips on the target and is suitable for the calibration of BSVS in outdoor environments. The effectiveness of the proposed method is validated through physical experiments.

Modeling 2-D Lens-Based Forward-Scan Sonar Imagery for Targets With Diffuse Reflectance

Sonar images are formed by transmitting acoustical pulses and measuring the reflected sound power from the scene surfaces. The recorded signal by a sonar device encodes information about the shape and material properties of these surfaces. In this paper, we present a detailed derivation of an image model for a new class of high-resolution lens-based 2-D forward-looking sonar systems, when the diffuse reflectance of scene/target can be characterized by the Lambertian model. A simplified single patch model is generalized to account for the finite pulse width of the transmitted beam and the simultaneous arrival of scattered signals from multiple patches at the same range in a given azimuthal direction. Validating the model using intensity measurements of isolated cylindrical targets, we then demonstrate application for multipath reflections from bottom surfaces with cylindrical and spherical targets.

A new muon-pion collection and transport system design using superconducting solenoids based on CSNS**Supported by National Natural Science Foundation of China (11527811)

A new muon and pion capture system is proposed for the China Spallation Neutron Source (CSNS), currently under construction. Using about 4% of the pulsed proton beam (1.6 GeV, 4 kW and 1 Hz) of CSNS to bombard a cylindrical graphite target inside a superconducting solenoid, both surface muons and pions can be acquired. The acceptance of this novel capture system - a graphite target wrapped up by a superconducting solenoid - is larger than the normal muon beam lines using quadrupoles at one side of the separated muon target. The muon and pion production at different capture magnetic fields was calculated using Geant4. The bending angle of the capture solenoid with respect to the proton beam was also optimized in simulation to achieve more muons and pions. Based on the layout of the muon experimental area reserved at the CSNS project, a preliminary muon beam line was designed with multi-purpose muon spin rotation areas (surface, decay and low-energy muons). Finally, high-flux surface muons (108/s) and decay muons (109/s) simulated by G4beamline will be available at the end of the decay solenoid based on the first phase of CSNS. This collection and transport system will be a very effective beam line at a proton current of 2.5 μA.

Modes of targets in water and on sand driven by modulated radiation pressure of focused ultrasound

In a previous work, we had shown that low frequency flexural modes of a circular plate could be excited using modulated radiation pressure generated by focused ultrasound [J. Acoust. Soc. Am. 137, 2439 (2015)]. Recently, we conducted another experiment where we examined plate, spherical, and cylindrical targets with a larger, higher power focused ultrasound, transducer operated at a carrier of 0.5 or 1.5 MHz that was capable of producing much stronger acoustic radiation pressures. A laser vibrometer was acquired to obtain quantitative measurements of the surface velocity of the targets to facilitate analysis of the radiation force generated on the targets as well as the pressure levels of the target sound emissions. The vibrometer was able to identity modes as well as measure mode shape. Furthermore, we were able to estimate the amount of radiation force that was driving the targets by using the vibrometer measurements to calculate their radiation loading from the water. We were also able to measure the r...

Ultrasonic scattering at 25 kilohertz in air by a hexagonal array of slender long rigid rods arranged to form a porous cylindrical target

Experiments were performed in the USNA Acoustics Lab using 30 cycle transient-bursts at 25.8 kHz in air (c = 340 m/s, ρ = 1.2 kg/m3) to measure the backscattering of the ultrasonic pulse from a hexagonal array of stainless steel rods (diam d = 0.089 cm, length l = 91 cm). The lattice parameter was a = 0.22 cm. To construct the array, the rods were placed within the holes of two 30.5 cm square thin perforated aluminum sheets suspended 88 cm apart. A third non-perforated sheet hung 1 cm below prevented the rods from falling through. The diameter of the cluster was D = 10 cm. The filling fraction of the lattice was f = 0.15.The transmitting array (located 1.5 m from the cluster) was an eight-element discrete ring of diam 5.5 cm that produced an interference null at + /− 10 degrees and a −10 dB down minor lobe at + /− 17 degrees. A single 1 cm diam receiver element was located at the center of the ring. In a strip-map configuration, the transmitted beam translated 60 cm across the target recording echoes at 1 cm increments. The target’s effective speed and density were 0.93c and 1.35ρ, respectively. See D. Torrent et. al. [Phys. Rev. Lett., 96, 204302 (2006)].

Spectral imaging using forward-viewing spectrally encoded endoscopy.

Spectrally encoded endoscopy (SEE) enables miniature, small-diameter endoscopic probes for minimally invasive imaging; however, using the broadband spectrum to encode space makes color and spectral imaging nontrivial and challenging. By careful registration and analysis of image data acquired by a prototype of a forward-viewing dual channel spectrally encoded rigid probe, we demonstrate spectral and color imaging within a narrow cylindrical lumen. Spectral imaging of calibration cylindrical test targets and an ex-vivo blood vessel demonstrates high-resolution spatial-spectral imaging with short (10 μs/line) exposure times.

Therapeutic analysis of high-dose-rate (192)Ir vaginal cuff brachytherapy for endometrial cancer using a cylindrical target volume model and varied cancer cell distributions.

To evaluate high-dose-rate (HDR) vaginal cuff brachytherapy (VCBT) in the treatment of endometrial cancer in a cylindrical target volume with either a varied or a constant cancer cell distributions using the linear quadratic (LQ) model. A Monte Carlo (MC) technique was used to calculate the 3D dose distribution of HDR VCBT over a variety of cylinder diameters and treatment lengths. A treatment planning system (TPS) was used to make plans for the various cylinder diameters, treatment lengths, and prescriptions using the clinical protocol. The dwell times obtained from the TPS were fed into MC. The LQ model was used to evaluate the therapeutic outcome of two brachytherapy regimens prescribed either at 0.5 cm depth (5.5 Gy × 4 fractions) or at the vaginal mucosal surface (8.8 Gy × 4 fractions) for the treatment of endometrial cancer. An experimentally determined endometrial cancer cell distribution, which showed a varied and resembled a half-Gaussian distribution, was used in radiobiology modeling. The equivalent uniform dose (EUD) to cancer cells was calculated for each treatment scenario. The therapeutic ratio (TR) was defined by comparing VCBT with a uniform dose radiotherapy plan in term of normal cell survival at the same level of cancer cell killing. Calculations of clinical impact were run twice assuming two different types of cancer cell density distributions in the cylindrical target volume: (1) a half-Gaussian or (2) a uniform distribution. EUDs were weakly dependent on cylinder size, treatment length, and the prescription depth, but strongly dependent on the cancer cell distribution. TRs were strongly dependent on the cylinder size, treatment length, types of the cancer cell distributions, and the sensitivity of normal tissue. With a half-Gaussian distribution of cancer cells which populated at the vaginal mucosa the most, the EUDs were between 6.9 Gy × 4 and 7.8 Gy × 4, the TRs were in the range from (5.0)(4) to (13.4)(4) for the radiosensitive normal tissue depending on the cylinder size, treatment lengths, prescription depth, and dose as well. However, for a uniform cancer cell distribution, the EUDs were between 6.3 Gy × 4 and 7.1 Gy × 4, and the TRs were found to be between (1.4)(4) and (1.7)(4). For the uniformly interspersed cancer and radio-resistant normal cells, the TRs were less than 1. The two VCBT prescription regimens were found to be equivalent in terms of EUDs and TRs. HDR VCBT strongly favors cylindrical target volume with the cancer cell distribution following its dosimetric trend. Assuming a half-Gaussian distribution of cancer cells, the HDR VCBT provides a considerable radiobiological advantage over the external beam radiotherapy (EBRT) in terms of sparing more normal tissues while maintaining the same level of cancer cell killing. But for the uniform cancer cell distribution and radio-resistant normal tissue, the radiobiology outcome of the HDR VCBT does not show an advantage over the EBRT. This study strongly suggests that radiation therapy design should consider the cancer cell distribution inside the target volume in addition to the shape of target.

Classification of underwater targets from autonomous underwater vehicle sampled bistatic acoustic scattered fields.

One of the long term goals of autonomous underwater vehicle (AUV) minehunting is to have multiple inexpensive AUVs in a harbor autonomously classify hazards. Existing acoustic methods for target classification using AUV-based sensing, such as sidescan and synthetic aperture sonar, require an expensive payload on each outfitted vehicle and post-processing and/or image interpretation. A vehicle payload and machine learning classification methodology using bistatic angle dependence of target scattering amplitudes between a fixed acoustic source and target has been developed for onboard, fully autonomous classification with lower cost-per-vehicle. To achieve the high-quality, densely sampled three-dimensional (3D) bistatic scattering data required by this research, vehicle sampling behaviors and an acoustic payload for precision timed data acquisition with a 16 element nose array were demonstrated. 3D bistatic scattered field data were collected by an AUV around spherical and cylindrical targets insonified by a 7-9 kHz fixed source. The collected data were compared to simulated scattering models. Classification and confidence estimation were shown for the sphere versus cylinder case on the resulting real and simulated bistatic amplitude data. The final models were used for classification of simulated targets in real time in the LAMSS MOOS-IvP simulation package [M. Benjamin, H. Schmidt, P. Newman, and J. Leonard, J. Field Rob. 27, 834-875 (2010)].

Wear Resistance of TiNx/CFy Coatings Deposited by RF Magnetron Co-Sputtering

TiNx/CFy composite coatings were prepared by RF magnetron co-sputtering using twin cylindrical tube targets with Ar and N2 mixtures. The composition of the coatings deposited at various positions was analyzed by X-ray photoelectron spectroscopy (XPS) and Rutherford back-scattering spectrometry (RBS). The results revealed that the composition of the deposited coatings has a wide range of TiNx and CFy contents at different deposition positions, which leads to different structures and performances. The hardness of the composite coatings increases from 32 to 1603 HV with increasing the TiNx concentration. The static contact angle of water ranges from 20° to 102° and decreases upon the incorporation of more TiNx into the CFy polymer. The presence of the CFy groups enhances the contact angle between the coating and the solutions dropped onto it, which could effectively protect the coating from corrosion and improve the wear resistance properties in high relative humidity (RH). The brittleness of the coatings decreases due to the softness of the CFy component, which can bear most of the load and result in less probability of crack formation. XPS results demonstrate the existence of a Ti (C N) chemical bond in the composite coatings, which improves the wear resistance of the coatings. It is indicated that the wear resistance of the TiNx/CFy coatings is independent of the hardness. However, these properties depend on the uniform structure and the existence of chemical bonding between the TiNx and CFy phases. Moreover, a specific ratio between the soft CFy phase and the hard TiNx phase can produce coatings with good wear resistance.

On the relationship of minimum detectable contrast to dose and lesion size in abdominal CT

CT dose optimization is typically guided by pixel noise or contrast-to-noise ratio that does not delineate low contrast details adequately. We utilized the statistically defined low contrast detectability to study its relationship to dose and lesion size in abdominal CT. A realistically shaped medium sized abdomen phantom was customized to contain a cylindrical void of 4 cm diameter. The void was filled with a low contrast (1% and 2%) insert containing six groups of cylindrical targets ranging from 1.2 mm to 7 mm in size. Helical CT scans were performed using a Siemens 64-slice mCT and a GE Discovery 750 HD at various doses. After the subtractions between adjacent slices, the uniform sections of the filtered backprojection reconstructed images were partitioned to matrices of square elements matching the sizes of the targets. It was verified that the mean values from all the elements in each matrix follow a Gaussian distribution. The minimum detectable contrast (MDC), quantified by the mean signal to background difference equal to the distribution’s standard deviation multiplied by 3.29, corresponding to 95% confidence level, was found to be related to the phantom specific dose and the element size by a power law (R^2 > 0.990). Independent readings on the 5 mm and 7 mm targets were compared to the measured contrast to the MDC ratios. The results showed that 93% of the cases were detectable when the measured contrast exceeds the MDC. The correlation of the MDC to the pixel noise and target size was also identified and the relationship was found to be the same for the scanners in the study. To quantify the impact of iterative reconstructions to the low contrast detectability, the noise structure was studied in a similar manner at different doses and with different ASIR blending fractions. The relationship of the dose to the blending fraction and low contrast detectability is presented.

Segmented beryllium target for a 2 MW super beam facility

Building a proton-beam target from an array of spheres improves shock resistance and cooling compared with a conventional solid cylindrical target.

Verification of Compton scattering spectrum of a 662 keV photon beam scattered on a cylindrical steel target using MCNP5 code

This article focuses on the possible application of a 137Cs low-radioactive source (5mCi) and a NaI(Tl) detector for measuring the saturation thickness of solid cylindrical steel targets. In order to increase the reliability of the obtained experimental results and to verify the detector response function of Compton scattering spectrum, simulation using Monte Carlo N-particle (MCNP5) code is performed. The obtained results are in good agreement with the response functions of the simulation scattering and experimental scattering spectra. On the basis of such spectra, the saturation depth of a steel cylinder is determined by experiment and simulation at about 27mm using gamma energy of 662keV (137Cs) at a scattering angle of 120°. This study aims at measuring the diameter of solid cylindrical objects by gamma-scattering technique.