A beam optics study of the biomedical beam line at a proton therapy facility

A biomedical beam line has been designed for the experimental area of a proton therapy facility to deliver mm to sub-mm size beams in the energy range of 20-50 MeV using the TRANSPORT/TURTLE beam optics codes and a newly-written program. The proton therapy facility is equipped with a 230 MeV fixed-energy cyclotron and an energy selection system based on a degrader and slits, so that beam currents available for therapy decrease at lower energies in the therapeutic beam energy range of 70-230 MeV. The new beam line system is composed of an energy-degrader, two slits, and three quadrupole magnets. The minimum beam sizes achievable at the focal point are estimated for the two energies of 50 and 20 MeV. The focused FWHM beam size is approximately 0.3 mm with an expected beam current of 20 pA when the beam energy is reduced to 50 MeV from 100 MeV, and roughly 0.8 mm with a current of 10 pA for a 20 MeV beam.     

New gas concentration measurement system for the PANDA containment test facility

The increased use of computational fluid dynamics code for analysis and design purposes demands high quality experimental data to validate the simulation codes. Experimental data of fluid stratification and stratification break-up phenomena are generated in the frame of OECD/SETH-2 project at the PANDA facility. A new gas concentration measurement system is presented that is based on speed of sound measurements. Speed of sound in gas mixtures is a unique function of the temperature and the fractions of the components and therefore can be used to compute the fractions in varying compositions. The speed of sound is measured indirectly measuring the time of flight of an ultrasound pulse between two ultrasound transducers. The 30 transducers employed proved to be able to withstand the unfavorable conditions inside the facility with temperatures of up to 110 °C and steam that may condense. A frame rate (1 frame = each transducer has been excited) of 1.6 Hz and a helium fraction resolution of 1.5% in steam are achieved.     

Irradiation effects of a 10 MeV neutron beam on a Nd-Fe-B permanent magnet

The effects of irradiation of a Nd-Fe-B permanent magnet by fast neutrons was investigated. The decrease in measured magnetic flux density at the center of the magnets were 0.6%, 6.9%, 25.2% and 47.3% after continuous irradiation of 1.1 kGy, 3.7 kGy, 5.6 kGy and 7.4 kGy, respectively. On the other hand, the decrease due to non-continuous irradiation, in which the magnet was first irradiated at 3.7 kGy, then irradiated again at 3.7 kGy nine months later, was 14% smaller than that of continuous irradiation, even for the same total dose. The temperature coefficient of the magnetization did not change with irradiation. Some radioactive materials, such as ¹⁴⁷Nd, ¹⁵¹Pm, and ⁵⁴Mn, were detected in the magnet after irradiation.     

Fracture behavior of austenitic stainless steels irradiated in PWR

Fracture behavior of cold-worked 316 stainless steels irradiated up to 73 dpa in a pressurized water reactor was investigated by impact testing at −196, 30 and 150 °C, and by conventional tensile and slow tensile testing at 30 and 320 °C. In impact tests, brittle IG mode was dominant at −196 °C at doses higher than 11 dpa accompanying significant decrease in absorbed energy. The mixed IG mode, which was characterized by isolated grain facets in ductile dimples, appeared at 30 and 150 °C whereas the fracture occurred macroscopically in a ductile manner. The sensitivity to IG or mixed IG mode was more pronounced for higher dose and lower test temperature. In uniaxial tensile tests, IG mode at a slow strain rate appeared only at 320 °C whereas mixed IG mode appeared at both 30 and 320 °C at a fast strain rate. A compilation of the results and literature data suggested that IG fracture exists in two different conditions, low-temperature high-strain-rate (LTHR) and high-temperature low-strain-rate (HTLR) conditions. These two conditions for IG fracture likely correspond to two different deformation modes, twining and channeling.     

The first performance of the facility for testing ITER CC conductor short sample

A new facility had been set up to test the low temperature properties of the short sample of the small-size cable-in-conduit conductor (CICC). The facility consisted of the background magnet which could provide 7 T centric magnetic field, a 50 kA superconducting transformer which provided sample current, a 500 W/4.5 K helium refrigerator which produced both the liquid helium (LHe) and supercritical helium (SHe). An ITER CC conductor short sample was prepared and measured in this testing system. T_cs of 7.02 K (@4.1 T, 10 kA) and I_c of 8.9 kA (@4.1 T, 7.06 K) were measured.     

A new HVE 6 MV AMS system at the University of Cologne

CologneAMS is the new Centre for Accelerator Mass Spectrometry (AMS) at the University of Cologne. It will operate a dedicated AMS system designed to measure all standard cosmogenic nuclides (¹⁰Be,¹⁴C,²⁶Al,³⁶Cl, ⁴¹Ca,¹²⁹I) and which uses a 6 MV Tandetron™ accelerator equipped with an all solid-state power supply, foil and gas stripper. The system also enables a sensitive detection of heavy ions up to ²³⁹U and ²⁴⁴Pu. The high-energy mass-spectrometer consists of a 90 degree magnet with a radius of 2 m and a mass-energy product of 351 AMU MeV to allow the detection of ²⁴⁴Pu⁵⁺ up to the maximum terminal voltage of 6 MV. This magnet is followed by an electrostatic energy analyzer and a switching magnet that can transport the rare isotope beam into various beamlines. The switching magnet forms a third analyzing element which is needed especially for the sensitive detection of heavy elements. So far two beamlines are equipped with their own detection system. One of these lines is used for suppression of isobaric background in the case of the analysis of e.g. ³⁶Cl. This is accomplished by an absorber foil which generates a Z-dependent energy loss in combination with a momentum/charge-state selection via a 120 degree magnet that features up to 30 mrad acceptance for efficient beam transport.In this contribution we will introduce the new Centre, the layout and specific characteristics of the AMS system as well as the main topics of the future scientific work to be performed at CologneAMS.     

Conceptual design of the FAST load assembly

Fusion advanced studies torus (FAST) is a proposal for a satellite facility which can contribute the rapid exploitation of ITER and prepare ITER and DEMO regimes of operation, as well as exploiting innovative DEMO technology. FAST is a compact (R₀ = 1.82 m, a = 0.64 m, triangularity δ = 0.4) machine able to investigate non-linear dynamics effects of alpha particle behaviours in burning plasmas [1], [2] and [5]. The project is based on a dominant 30 MW of ion cyclotron resonance heating (ICRH), 6 MW of lower hybrid (LH) and 4 MW of electron cyclotron resonance heating (ECRH). FAST operates at a wide range [3] and [4] of parameters, e.g., in high performance H-mode (B_T up to 8.5 T; I_P up to 8 MA) as well as in advanced Tokamak operation (I_P = 3 MA), and full non-inductive current scenario (I_P = 2 MA). Helium gas at 30 K is used for cooling the resistive copper magnets [6]. That allows for a pulse duration up to 170 s. To limit the TF magnet ripple ferromagnetic insert have been introduced inside the vacuum vessel (VV). Ports have been designed to also accommodate up to 10 MW of negative neutral beam injection (NNBI). Tungsten (W) or liquid lithium (L-Li) have been chosen as the divertor plates material, and argon or neon as the injected impurities to mitigate the thermal loads.     

Chemical interaction of yttrium aluminosilicate glass with CeO2, UO2 and PuO2 at high temperatures

The thermal interaction of yttrium aluminosilicate glass with cerium, plutonium and uranium oxides at temperatures up to 1200 °C has been studied by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD), and secondary electron microscopy (SEM). The glass, a candidate for joining and sealing advanced fuel cladding materials, such as silicon carbide (SiC), undergoes a recrystallization process above 1000 °C providing a mixture that exhibits two melting points at 1379 and 1410 °C. Samples containing glass and actinide oxide mixtures did not form new phases, nor did the actinide oxides influence the recrystallization behavior of the glass.     

The annealing behavior of Cu nanoparticles in Ar-ion implanted spinel

Magnesium aluminate spinel crystals (MgAl₂O₄ (1 1 0)) deposited with 30 nm Cu film on surface were implanted with 110 keV Ar-ions to a fluence of 1.0 × 10¹⁷ ions/cm² at 350 °C, and then annealed in vacuum condition at the temperature of 500, 600, 700, 800 and 900 °C for 1 h, respectively. Ultraviolet-visible spectrometry (UV-VIS), scanning electron microscopy (SEM), Rutherford backscattering (RBS) and transmission electron microscopy (TEM) were adopted to analyze the specimens. After implantation, the appearance of surface plasmon resonance (SPR) absorbance peak in the UV-VIS spectrum indicated the formation of Cu nanoparticles, and the TEM results for 500 °C also confirmed the formation of Cu nanoparticles at near-surface region. In annealing process, The SPR absorbance intensity increased at 500 and 700 °C, decreased with a blue shift of the peak position at 600 and 800 °C, and the peak disappeared at 900 °C. The SPR absorbance intensity evolution with temperature was discussed combined with other measurement results (RBS, SEM and TEM).     

Two-phase minor loss in horizontal bubbly flow with elbows: 45° and 90° elbows

The present study investigates the geometric effects of a 45° elbow on the pressure drop due to the minor loss in horizontal bubbly flow. A round glass tube with inner diameter of 50.3 mm is employed as a test section, along which a 45° elbow is installed at L/D = 353.5 from the two-phase mixture inlet. In total, 15 different flow conditions are examined. The local static pressures are measured at four axial locations at L/D = 197, 342, 363 and 419 from the two-phase mixture inlet. The effect of the elbow is clearly demonstrated in the pressure data along the axial direction. In the data analysis, the pressure data previously acquired with a 90° elbow is also utilized as well. The conventional Lockhart-Martinelli correlation with parameter C = 30 predicts the overall two-phase frictional pressure loss between the inlet and exit of the test section relatively well for both the 90° and 45° elbow experiments. However, it fails to predict the pressure loss across the elbows, because the existing model does not account for the additional loss due to the flow restrictions. In view of this, a new correlation analogous to Lockhart and Martinelli’s is developed for the two-phase frictional pressure loss across the elbows. The new correlation with the parameter C = 65 and the minor loss factors of k = 0.58 and k = 0.35 for the 90° and 45° elbows, respectively, yields the best fit to the data. The average percent differences between the predictions made by the new correlation and the data are ±2.1% and ±1.3% for 90° and 45° cases, respectively.     

Interferences in electron emission from O2 by 30 MeV O impact

Interference structures in the ejected electron spectra for 30 MeV O^5,8+ + O₂ are investigated. The measured electron yields were studied for electron energies from 5 to 400 eV and observation angles of 30°, 60°, 90°, 120° and 150° with respect to the incident beam direction. Experimental molecular cross-sections were normalized to theoretical molecular one-center cross-sections revealing oscillatory structures suggestive of secondary interferences as evidenced by the independence on the observation angle. An oscillation interval for 30 MeV O^5,8+ + O₂ of Δk ∼ 4 a.u. is found, a value two times larger than that previously observed for 3 MeV H⁺ + N₂. No obvious evidence for primary Young-type interferences was seen.     

The Singapore high resolution single cell imaging facility

The Centre for Ion Beam Applications, National University of Singapore has recently expanded from three state-of-the-art beam lines to five. Two new beam lines have been constructed: A second generation proton beam writing line, and a high resolution single cell imaging facility. Both systems feature high demagnification lens systems based on compact Oxford Microbeams OM52 lenses, coupled with reduced lens/image distances.The single cell imaging facility is designed around OM52 compact lenses capable of operating in a variety of high demagnification configurations including the spaced Oxford triplet and the double crossover Russian quadruplet. The new facility has design specifications aimed at spatial resolutions below 50 nm, with a variety of techniques including STIM, secondary electron and fluorescence imaging, and an in-built optical and fluorescence microscope for sample imaging, identification and positioning.Preliminary tests using the single space Oxford triplet configuration have indicated a beam spot size of 31 × 39 nm in the horizontal and vertical directions respectively, at beam currents of ∼10,000 protons per second. However, a weakness in the specifications of the electrostatic scanning system has been identified, and a more stable scanning system needs to be implemented before we can fully realize the optimum performance. A single whole fibroblast cell has been scanned using 1.5 MeV protons, and a median fit to the proton transmission energy loss data has shown that proton STIM gives excellent details of the cell structure despite the relatively poor contrast of proton STIM compared with alpha STIM.     

Beam stability improvement of the HIMAC synchrotron using a feed-forward system for magnet power supplies

In order to realize a precise dose distribution in heavy-ion cancer therapy, high beam stability is required for the accelerator complex. Owing to load fluctuation caused by the upper ring, which is one of the two rings in HIMAC, current dips of ≈5-10 Hz were observed in the power supply for the bending/quadrupole magnet of the other lower ring. The parameters of the beam stability, such as the spill variation, the beam position, and the size, were adversely affected by the current dips. In order to suppress these current dips, we developed a new feed-forward system in the magnet power supply. We verified the performance of the feed-forward system by measuring the suppression of the current dips. We also performed beam experiments to measure the variation of the horizontal tune and the structure of the beam spill, which is slowly extracted by the resonance method. The experimental result showed that the current dips were successfully reduced by the system to ΔI/I ∼ 10⁻⁶. It was also confirmed that the horizontal tune and the spill structure could be stabilized by the current dip suppression.     

Plasma grid design for optimized filter field configuration for the NBI test facility ELISE

Maintenance-free RF sources for negative hydrogen ions with moderate extraction areas (100-200 cm²) have been successfully developed in the last years at IPP Garching in the test facilities BATMAN and MANITU. A facility with larger extraction area (1000 cm²), ELISE, is being designed with a “half-size” ITER-like extraction system, pulsed ion acceleration up to 60 kV for 10 s and plasma generation up to 1 h. Due to the large size of the source, the magnetic filter field (FF) cannot be produced solely by permanent magnets. Therefore, an additional magnetic field produced by current flowing through the plasma grid (PG current) is required. The filter field homogeneity and the interaction with the electron suppression magnetic field have been studied in detail by finite element method (FEM) during the ELISE design phase. Significant improvements regarding the field homogeneity have been introduced compared to the ITER reference design. Also, for the same PG current a 50% higher field in front of the grid has been achieved by optimizing the plasma grid geometry. Hollow spaces have been introduced in the plasma grid for a more homogeneous PG current distribution. The introduction of hollow spaces also allows the insertion of permanent magnets in the plasma grid.     

Large-scale molecular dynamics simulation of sputtering process with glancing-angle Ar cluster impact on 4H-SiC

Large-scale molecular dynamics simulations with two Ar₆₈₈ cluster impacts on a 4H-SiC surface are performed to investigate the mechanism of lateral sputtering caused by two clusters collisions. The two Ar clusters are composed of 688 atoms each (referred as Ar₆₈₈) which are described by a simple Lennard-Jones potential. The initial velocities of both clusters are 2.55 × 10⁴ m/s when the acceleration voltage is 100 keV. The computational volume is 30 nm × 30 nm × 16 nm, which is constructed by 1444608 4H-SiC atoms. At 0.8 ps after the impact from the first Ar cluster on the 4H-SiC surface, a second argon cluster with predetermined incident-angle collides with 4H-SiC surface at a distance of one “diameter” away from the center of the first impact where the term “diameter” refers to the diameter of the footprint of the first impact on 4H-SiC. The incident-angle of the second argon cluster was set at 0°, 60°, or 80° for three different trials. Consequently, in each case the crater formed by the first cluster showed signs of being smeared out by the impact of the second cluster. Especially at the incident-angle of 80° the effects of surface modification were clearly noticeable.     

Panofsky magnet for the beam extraction from the synchrotron using a fast Q-magnet and RF-knockout

The fast control of the beam spill extracted from a synchrotron is a key function for the spot scanning irradiation in cancer therapy application. The authors propose an extraction method which uses the quadruple field of fast response, as well as the RF-knockout. A Panofsky magnet was developed as a quadruple magnet, with a frequency response of around 10 kHz. The Panofsky magnet has a rectangular beam aperture and plate coils attached to the pole face. A model magnet has been manufactured with ferrite, and static and dynamic magnetic fields were measured. From the measurement we observed that the effects of eddy current in the plate coils were large and the uniformity of the magnetic field gradient in the beam aperture was worse than ±5% with a plate thickness of 0.02 cm and a frequency of current of 10 kHz. For the future, in a detailed design the eddy current effects have to be taken into account.     

Improved energy resolution of a cyclotron beam for RBS measurements

For RBS (Rutherford Back Scattering) analysis, the quality of the beam is of premium importance because the depth profile resolution of the method is strongly dependent on the energy resolution of the probing beam. A magnetic analyzer, consisting of two 90 left-right bending magnets forming an achromatic doublet has been adapted to the Liege 20 MeV (proton) AVF (Azimuthal Varying Field) cyclotron. The energy resolution of that system has been measured by recording the resonance width of a ³²S(p,p′γ)³²S (3.38 MeV. p⁺ lab. energy). We have obtained a value of ΔE = ± 2 keV, reducing by a factor of 20 the natural dispersion of our cyclotron.We describe our magnetic analyzer system and present the results of our RBS measurements at energies up to 14 MeV α.     

A portable luminescence dating instrument

We describe a portable luminescence reader suitable for use in remote localities in the field. The instrument weighs about 8 kg and is based around a 30 mm bialkali photomultiplier detecting signals through a glass filter centered on 340 nm. Stimulation is by 470 nm blue LEDs (24 W in total) operating in both continuous wave and pulsed mode; photon counting can be gated such that it is active only during the pulse off-period. There are also two bleaching light sources (470 nm, 5 W and 940 nm, 3 W), and the luminescence signals can be regenerated using a cold-cathode 30 kV X-ray tube, delivering ∼0.06 Gy.s⁻¹. The three position sampling device has a heating element under each sampling position, able to heat the sample at 3 °C.s⁻¹ up to at least 250 °C. The sampler can be inserted into unconsolidated sediments, and is designed to prevent exposure of the mineral grains to ambient light during sampling. The performance of the instrument in terms of sensitivity and reproducibility is comparable to that of the standard bench-top laboratory TL/OSL Risø reader.We show that the portable luminescence reader is able to measure accurately an ∼20 Gy quartz burial dose in a natural (unpretreated, no mineral separation) sandy sediment. We also show that, because of the configuration of the measurement head, the portable reader can be used to measure radioluminescence at elevated temperature in the presence of stimulation light; this facility is not available on conventional bench-top instruments. It is concluded that the portable luminescence reader can be used to accurately determine the quartz burial dose in loose sandy sediments in the field, without sample preparation or darkroom facilities.     

Evaluation of aged Incoloy 800 alloy sensitization to intergranular corrosion by means of double loop electrochemical methods and image analysis

In this paper, the sensitization of aged Incoloy 800 alloy to intergranular corrosion has been systemically investigated by double loop electrochemical potentiokinetic reactivation (DL-EPR) technique in combination with oxalic acid etching test and microstructure observation. The DL-EPR results show that the specimens aged at 650 °C and 700 °C for 4 h were intensely sensitized with I_r:I_a value greater than 30% while there was no sensitization phenomenon for the specimens aged at 800 °C for 4 h. It was also found that the degree of sensitization increased gradually with the aging time in the range of 0-10 h at 650 °C, and I_r:I_a value reached the maximum −46% after an aging time of 10 h. However, further increasing aging time decreased the sensitization due to the healing effect incurred by the diffusion of chromium from adjacent grains to chromium-depleted zones. Comparison between two evaluating techniques (the DL-EPR and oxalic acid etching test) has also been conducted.     

The PTB single ion microbeam for irradiation of living cells

At the PTB's ion accelerators, a new microbeam facility is now in operation that is capable of delivering single ions, for example, to the nuclei of individual living cells. The wide range of proton and ⁴He²⁺ ion energies affords LET-values between 3 and 200 keV/μm. A beam diameter of less than 2 μm outside the vacuum system has been measured and a targeting accuracy of better than 2 μm has been determined. In contrast to other microbeam facilities operated for radiobiological research using mechanical collimators in front of the target to define the beam, the PTB facility utilises beam focusing by quadrupole magnets. The microbeam has a unique ion optical design that incorporates a 90° bending magnet in the beam transport system. This design has the advantage of providing a microbeam basically without scattered particles. Every ion reaching the target is detected by a thin scintillating foil and a photomultiplier tube with efficiency close to 100%. Presently up to 1500 single cells per hour can be automatically irradiated with a chosen number of particles. Procedures and results of first cell irradiations are described as an example.