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.     

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.     

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.     

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.     

Design and experimental results of feedback control of Ohmic-heating transformer magnetic flux by LHCD power in HT-7 Tokamak

In order to make a research on long pulse or even steady state operation with non-inductive drive in plasma discharge, a new feedback control scheme instead of the previous one has been designed and operated in HT-7 [HT-7 team presented by J. Li, et al., Plasma Phys. Control. Fusion 42 (2) (2000) 135-146] Tokamak experiment, 2004. Consumption of iron-core transformer magnetic flux (MFT) is feedback controlled for the first time by power of lower hybrid current drive (LHCD) P_LH, when the Ohmic-heating circuit current can maintain the plasma current I_P constant with another feedback control loop, which make MFT evolve at alternating-change state to avoid flux saturation. Plasma current I_P can be maintained steadily up to 120 s in this operation mode at reduced plasma parameters (I_P ≈ 50-100 KA, average density , P_LH = 100-200 KW). Design and experimental results are presented in the paper, which including control model analysis, configurations of control system and MFT feedback control experiments in HT-7. The high voltage power supply (HVPS) of LHCD is the main controller that regulates the LHCD power into the plasma to control the MFT.     

Design of an ion extractor system for a prototype ion source experiment for SST-1 neutral beam injector

An ion extractor system has been designed for the steady state superconducting tokamak (SST-1) neutral beam injector (NBI) for an experiment using a prototype ion source with fully integrated regulated high voltage power supply (RHVPS) and data acquisition and control system (DACS) developed at Institute for Plasma Research (IPR) to obtain experience of NB operation. The extractor system is capable of extracting positive hydrogen ion beam of ∼10 A current at ∼20 kV. This paper presents the beam optics study for detailed design of an ion extraction system which could meet this requirement. It consists of 3 grid accel-decel system, each of the grid has 217 straight cylindrical holes of 8 mm diameter. Grids are placed on a specially designed G-10 block; a fiber reinforc plastic (FRP) isolator of outer diameter of 820 mm and 50 mm thickness. Provisions are made for supplying high voltage to the grid system through the embedded feed-throughs. Extractor system has been fabricated, mounted on the SST-1 neutral beam injector and has extracted positive hydrogen ion beam of 4 A at 20 kV till now.     

Progress of in-air microbeam system at the Wakasa Wan Energy Research Center

Modifications of an in-air microbeam system at the Wakasa Wan Energy Research Center designed to improve its performance are described. In the previous setup, a silicon nitride membrane (area: 1 × 1 mm²; thickness: 100 nm) was used for the beam exit window and the distance between the window and the sample was restricted to ?1.7 mm. Due to this restriction, the beam spot size obtained using the previous setup was 13 × 13 μm². To reduce the beam spot size, the beam exit window was replaced by a silicon nitride membrane (area: 3 (horizontal) × 2 (vertical) mm²; thickness: 200 nm). In this setup, the sample can be moved as close as 0.7 mm to the window, enabling a beam spot size of 7 × 6 μm² to be achieved. An additional Si-PIN X-ray detector was installed to estimate the relative number of beam particles. It detects X-rays from the beam exit window. The number of the X-rays from the beam exit window (which is proportional to the number of beam particles) is used for quantitative analysis and for online monitoring of the beam current. This system has the potential to be used for simultaneous particle-induced X-ray emission (PIXE) and particle-induced gamma-ray emission (PIGE) measurements and for studying dental medicine.     

Measurement of L X-ray fluorescence cross-sections for elements with 45 ? Z ? 50 using synchrotron radiation at 8 keV

The L shell fluorescence cross-sections of the elements in range 45 ? Z ? 50 have been determined at 8 keV using Synchrotron radiation. The individual L X-ray photons, Ll, Lα, Lβ_I, Lβ_II, Lγ_I and Lγ_II produced in the target were measured with high resolution Si(Li) detector. The experimental set-up provided a low background by using linearly polarized monoenergetic photon beam, improving the signal-to-noise ratio. The experimental cross-sections obtained in this work were compared with available experimental data from Scofield [1] and [2] Krause [3] and [4] and Scofield and Puri et al. [5] and [6].These experimental values closely agree with the theoretical values calculated using Scofield and Krause data, except for the case of Lγ, where values measured of this work are slighter higher.     

RADI—A RF source size-scaling experiment towards the ITER neutral beam negative ion source

IPP Garching is currently developing a negative hydrogen ion RF source for the ITER neutral beam system. The source demonstrated already current densities in excess of the ITER requirements (>200 A/m² D⁻) at the required source pressure and electron/ion ratio, but with only small extraction area and limited pulse length. A new test facility (RADI) went recently into operation for the demonstration of the required (plasma) homogeneity of a large RF source and the modular driver concept.The source with the dimension of 0.8 m × 0.76 m has roughly the width and half the height of the ITER source; its modular driver concept will allow an easy extrapolation in only one direction to the full size ITER source. The RF power supply consists of two 180 kW, 1 MHz RF generators capable of 30 s pulses. A dummy grid matches the conductance of the ITER source. Full size extraction is presently not possible due to the lack of an insulator, a large size extraction system and a beam dump.The main parameters determining the performance of this “half-size” source are the negative ion and electron density in front of the grid as well as the homogeneity of their profiles across the grid. Those will be measured by optical emission and cavity ring down spectroscopy, by Langmuir probes and laser detachment. These methods have been calibrated to the extracted current densities achieved at the smaller source test facilities at IPP for similar source parameters. However, in order to get some information about the possible ion and electron currents, local single aperture extraction with a Faraday cup system is planned.     

Guiding and blocking of highly charged ions through a single glass capillary

Highly charged ions produced in an electron beam ion trap, I^q+, q = 10-50, were transmitted through a tapered glass capillary having diameter of at the end. We found that for a particular beam current, there exists an optimum tilting angle of the capillary in which a steady output of ions is observed, while for smaller angles, the ion counts first rise, then gradually decay on a time scale of minutes. In the case of steady transmission, the charge state distribution is found to be slightly towards the lower side.     

Real-time measurement and feedback control of ion temperature profile and toroidal rotation using fast CXRS system in JT-60U

A fast charge exchange recombination spectroscopy (CXRS) system has been developed for the real-time measurement and feedback control of ion temperature (T_i) profile and toroidal rotation velocity (V_t) in JT-60U. In order to control T_i and V_t in real-time, the charge exchange recombination spectroscopy with high time resolution, the real-time processor system, and the real-time control system have been developed. Utilizing this system, real-time control of the T_i gradient between r/a ∼ 0.25-0.5 has been demonstrated with neutral beams at high beta plasmas (normalized beta β_N ∼ 1.6-2.8). The strength of the internal transport barrier is controlled. Moreover, the real-time control of V_t has been demonstrated from counter (anti-parallel to the plasma current, I_p) to co (parallel to the I_p) direction. Then the behavior of edge localized mode (ELM) is changed by controlling the V_t.     

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.     

Guiding of argon ions through a tapered glass capillary

We report results from our recent experiments on guiding of Ar⁸⁺ ions through a single tapered glass capillary with an inlet diameter of 1 mm, an outlet diameter of 0.15 mm and a length of 45 mm. The profile width of the transmitted ion beam and the guiding power of the used glass capillary has been measured at a kinetic energy in the range of 8 keV up to 60 keV using a position sensitive detector. The charge up of the capillary and the evolution of the guiding effect is shown for a tilt angle of Ψ = 4°. The charge up of the inner walls of the tapered glass capillary causes a compression of the incident ion beam by a factor of 8. We found high guiding angles and small profile width of the transmitted ion beam in comparison to the transmission of highly charged ions through nanocapillaries in thin foils. A suppression of the transmission at small tilt angles and low kinetic energies has been observed.     

8 MeV electron irradiation effect on the dielectric and optical properties of iminodiacetic acid doped ferroelectric triglycine sulphate crystals

Single crystal of iminodiacetic acid (5 mol%) doped Tri Glycine Sulphate (IDATGS) was grown by slow evaporation from its aqueous solution at constant temperature, using solution growth method. The dielectric constant (ε′) and pyroelectric current (I_P) were measured over the temperature range of 30-60 °C in the ferroelectric direction. The measured values of ε′ and I_P were found to be smaller compared to pure triglycine sulphate (TGS) crystal parameters. But increased transition temperature was observed for doped crystals. Curie Weiss constants C_P and C_f in the paraelectric and ferroelectric phases were also determined. The doped crystal was irradiated with graded dosages from 5 to 80 kGy of electron beam from 8 MeV Microtron at room temperature and radiation effects on optical and dielectric properties were studied. The UV-Vis absorption spectrum indicates that the UV lower cutoff shifts towards the higher wavelength region (red shift) and the optical band gap is found to be decreasing with the increase of electron dose. It is also observed that the electron irradiation effects in pure and doped TGS were found to be long lasting. The dielectric study shows that there is a gradual reduction in dielectric constant at T_C and shifting of Curie temperature towards lower temperature region with the increase in electron radiation dose. The material figures of merit were found increased after the crystal was irradiated. Induced changes in the physical and optical properties due to irradiation may help one to tailor the device quality and characteristics.     

Measurement of thermal neutron cross-sections and resonance integrals for Hf(n,γ)Hf and Hf(n,γ)Hf reactions at the Pohang neutron facility

The thermal-neutron cross-sections and the resonance integrals for the ¹⁷⁹Hf(n,γ)^180mHf and the ¹⁸⁰Hf(n,γ)¹⁸¹Hf reactions have been measured by the activation method. The high purity Hf and Au metallic foils within and without a Cd shield case were irradiated in a neutron field of the Pohang neutron facility. The gamma-ray spectra from the activated foils were measured with a calibrated p-type high-purity Ge detector.In the experimental procedure, the thermal neutron cross-sections, σ₀, and resonance integrals, I₀, for the ¹⁷⁹Hf(n,γ)^180mHf and the ¹⁸⁰Hf(n,γ)¹⁸¹Hf reactions have been determined relative to the reference values of the ¹⁹⁷Au(n,γ)¹⁹⁸Au reaction, with σ₀ = 98.65 ± 0.09 barn and I₀ = 1550 ± 28 barn. In order to improve the accuracy of the experimental results, the interfering reactions and necessary correction factors were taken into account in the determinations. The obtained thermal neutron cross-sections and resonance integrals were σ₀ = 0.424 ± 0.018 barn and I₀ = 6.35 ± 0.45 barn for the ¹⁷⁹Hf(n,γ)^180mHf reaction, and σ₀ = 12.87 ± 0.52 barn and I₀ = 32.91 ± 2.38 barn for the ¹⁸⁰Hf(n,γ)¹⁸¹Hf reaction. The present results are in good agreement with recent measurements.     

Optimal ion beam,target type and size for accelerator driven systems: Implications to the associated accelerator power

In interactions of different energetic ions with extended targets hydrogen isotopes are the most effective projectiles for the production of spallation neutrons. It is shown that for every target material and incident ion type and energy there is an optimal target size which results in the escape of a maximum number of spallation neutrons from the target. Calculations show that in an ADS, combination of a beam of 1.5 GeV deuteron projectiles and a uranium target results in the highest neutron production rate and therefore highest energy gain. For fast 1.5 GeV d + ²³⁸U ADS with lead or lead–bismuth eutectic moderator, the required ion beam current is only 38% of that for 1 GeV proton projectiles on lead target. It is shown that for a modular ADS with uranium target and output power of 550 MW_th a 1.5 GeV deuteron beam of current 1.8 mA is required, which is easily achievable with today’s technology. For an ADS with k_eff = 0.98 and output power of 2.2 GW_th, the required beam currents for (a) 1 GeV p + Pb and (b) 1.5 GeV d + U systems are 18.5 and 7.1 mA, respectively.     

K-shell X-ray fluorescence cross-sections and intensity ratios for some pure metals at 59.5 and 123.6 keV

K-shell X-ray fluorescence cross-sections for some pure metals such as Cr, Fe, Co, Cu, Zn, Ga, Se, Y, Mo, Cd, In, Sn, Te, Ba, Ta, W and Bi have been theoretically and experimentally determined. The Cr, Fe, Co, Cu, Zn, Ga, Se, Y, Mo, Cd, In, Sn, Te and Ba metals were excited by 59.5 keV γ-ray from 50 mCi ²⁴¹Am radioactive source and the Ta, W and Bi targets were excited by 123.6 keV γ-ray from 25 mCi ⁵⁷Co radioactive source. The characteristic K X-rays emitted by samples were detected by using a super Si(Li) detector having a resolution of 150 eV at 5.9 keV. In addition, the I_Kβ/I_Kα intensity ratios for these metals were studied. The obtained experimental values of the K-shell X-ray fluorescence cross-sections and the I_Kβ/I_Kα intensity ratios have been compared with theoretical values. The measured values were in good agreement with theoretical values.     

Measurement of density distribution of a cracking catalyst in experimental riser with a sampling procedure for gamma ray tomography

By scanning a riser the number of the gamma ray trajectories and the beam width involve temporal, spatial and density resolutions as they are closely correlated parameters. Therefore, evaluation of parameters and their interaction quantification, certainly, are required in the imaging process. Measuring the density distribution of the catalyst from the FCC - fluid cracking catalytic process in an experimental riser in single beam tomographic system, density resolution is evaluated and correlated with spatial resolution. The beam width Δs inside riser is measured and a criterion for determining spatial resolution is proposed. Experiments are carried out to demonstrate resolution effects of three Δs values: 3.30 × 10⁻³, 6.20 × 10⁻³ and 12.00 × 10⁻³ m. The gamma beam profile is modeled and a sampling rate according to Nyquist criterion is analyzed. The 4.3%, 8.1% and 15.6% ratios of Δs/R to internal riser radius are correlated to counting time in the sampling procedure. Results are discussed by comparison with values from literature.     

Silkworm eggs: An ideal model for studying the biological effects of low energy Ar ion interaction in animals

The object of the current work was to study low energy Ar⁺ ion beam interactions with silkworm eggs and thus provide further understanding of the mechanisms involved in ion bombardment-induced direct gene transfer into silkworm eggs. In this paper, using low-energy Ar⁺ ion beam bombardment combined with piggyBac transposon, we developed a novel method to induce gene transfer in silkworm. Using bombardment conditions optimized for egg-incubation (25 keV with ion fluences of 800 × 2.6 × 10¹⁵ ions/cm² in dry state under vacuum), vector pBac{3 × P3-EGFPaf} and helper plasmid pHA3pig were successfully transferred into the silkworm eggs. Our results obtained from by PCR assay and genomic Southern blotting analysis of the G1 generations provide evidence that low-energy ion beam can generate some craters that play a role in acting as pathways of exogenous DNA molecules into silkworm eggs.     

Proton sputtering from polycrystalline Al surface interacting with highly charged ions at grazing incidence angle

Sputtering processes of protons from a polycrystalline Al surface interacting with Ar^q+ (q = 3-14) ions at a grazing incidence angle (∼0.5°) were investigated. The intensity of protons (I_H) detected in coincidence with scattered Ar atoms was measured as a function of q. I_H saturated at q ? 10, although it increased rapidly with q at 3 ? q ? 8. The angular distribution of protons with low kinetic energy (?2 eV) began to deviate from the cosine distribution and assumed a rather flat equidistribution as q increased. To analyze the sputtering processes of protons at the grazing incidence angle, a modified model of the “above-surface potential sputtering model” was proposed by considering image acceleration of projectile ions.