Optical diagnostics of negative ion beam transport

A diagnostic complex for monitoring the position, propagation direction, and angular distribution dispersion of a particle beam planned for application in the Boron Neutron Capture Therapy facility is described in this paper. For the beam position and direction, the precision is, respectively, 0.1 mm and 1 mrad at 10 mA CW H- beam with energy of about 35 keV and a diameter of the order of 10 mm. The energy spread and angular divergence were measured within the accuracy of about 100 eV and 3 mrad, respectively. The acceptable precision of about 1 mm for the beam position is obtained at a relatively short exposure to 10 ms. To increase the radiation intensity of the beam, the addition of various gases was studied. The addition of gas decreases the beam width and increases the negative ions stripping.

Development of continuous wave high voltage negative ion beam injector for tandem accelerator

A vacuum-insulated tandem accelerator, delivering the continuous wave 8 mA, 2 MeV proton beam, is operated regularly at the Budker Institute of Nuclear Physics, where a 10 mA, 25 keV negative ion injector is used. Recently, a new injector with an upgraded negative ion source and beam preacceleration has been developed to increase the tandem accelerated current. The transport line of the new injector is composed of a bending magnet with 90° ion beam turn, an acceleration tube for negative ion acceleration to the energy up to 150 keV, and a 0.6 m long transport section. The H^- ion beam production, its acceleration, and transport were studied at a test stand, which is equipped with electrical and optical diagnostics. The data on 14 mA, 133 keV continuous wave negative ion beam production and transport are presented. The undesirable coacceleration of secondary electrons, produced in the acceleration tube, was recorded as well. The coaccelerated electrons' current contributed up to 2% of the total accelerated beam at the operational vacuum in the low energy beam transport. The coaccelerated electrons were removed from the beam with a magnetic filter. The numerical modeling of the beam transport was carried out. A reasonable agreement between the modeled and experimental data was obtained.

Study of continuous wave 33 keV H- beam transport through the low energy beam transport section

The transport of a continuous wave 33 keV negative ion beam through the low energy beam transport section, designed for beam injection into the tandem accelerator, was studied. The continuous wave H^- beam, produced by the Penning surface-plasma source with hollow cathodes and cesium addition, was separated and focused by the 90° bending magnet and then transported through the 0.8 m long transport tube, equipped with beam electrical and optical diagnostics. The beam current was measured by a water-cooled Faraday cup at the transport tube exit. Beam sizes and profiles were measured by CCD cameras looking into the beam from the back and sides. The additions of hydrogen, argon, and xenon to the transport tube and to the bending magnet chamber in the pressure range of 10^-6 to 10^-4 Torr were tested. The influence of gas addition on the beam space charge compensation and beam transport was studied. A mechanism for the H^- beam focusing due to space charge overcompensation and beam compression by the positive charge, produced with positive ion accumulation in the beam, is discussed.

A comparative study of LaBr3(Ce(3+)) and CeBr3 based gamma-ray spectrometers for planetary remote sensing applications

The recent availability of large volume cerium bromide crystals raises the possibility of substantially improving gamma-ray spectrometer limiting flux sensitivities over current systems based on the lanthanum tri-halides, e.g., lanthanum bromide and lanthanum chloride, especially for remote sensing, low-level counting applications or any type of measurement characterized by poor signal to noise ratios. The Russian Space Research Institute has developed and manufactured a highly sensitive gamma-ray spectrometer for remote sensing observations of the planet Mercury from the Mercury Polar Orbiter (MPO), which forms part of ESA's BepiColombo mission. The Flight Model (FM) gamma-ray spectrometer is based on a 3-in. single crystal of LaBr3(Ce(3+)) produced in a separate crystal development programme specifically for this mission. During the spectrometers development, manufacturing, and qualification phases, large crystals of CeBr3 became available in a subsequent phase of the same crystal development programme. Consequently, the Flight Spare Model (FSM) gamma-ray spectrometer was retrofitted with a 3-in. CeBr3 crystal and qualified for space. Except for the crystals, the two systems are essentially identical. In this paper, we report on a comparative assessment of the two systems, in terms of their respective spectral properties, as well as their suitability for use in planetary mission with respect to radiation tolerance and their propensity for activation. We also contrast their performance with a Ge detector representative of that flown on MESSENGER and show that: (a) both LaBr3(Ce(3+)) and CeBr3 provide superior detection systems over HPGe in the context of minimally resourced spacecraft and (b) CeBr3 is a more attractive system than LaBr3(Ce(3+)) in terms of sensitivities at lower gamma fluxes. Based on the tests, the FM has now been replaced by the FSM on the BepiColombo spacecraft. Thus, CeBr3 now forms the central gamma-ray detection element on the MPO spacecraft.

Efficient cesiation in RF driven surface plasma negative ion source

Experiments on hydrogen negative ions production in the large radio-frequency negative ion source with cesium seed are described. The system of directed cesium deposition to the plasma grid periphery was used. The small cesium seed (∼0.5 G) provides an enhanced H(-) production during a 2 month long experimental cycle. The gradual increase of negative ion yield during the long-term source runs was observed after cesium addition to the source. The degraded H(-) production was recorded after air filling to the source or after the cesium washing away from the driver and plasma chamber walls. The following source conditioning by beam shots produces the gradual recovery of H(-) yield to the high value. The effect of H(-) yield recovery after cesium coverage passivation by air fill was studied. The concept of cesium coverage replenishment and of H(-) yield recovery due to sputtering of cesium from the deteriorated layers is discussed.

Effect of plasma grid bias on extracted currents in the RF driven surface-plasma negative ion source

Extraction of negative ions from the large inductively driven surface-plasma negative ion source was studied. The dependencies of the extracted currents vs plasma grid (PG) bias potential were measured for two modifications of radio-frequency driver with and without Faraday screen, for different hydrogen feeds and for different levels of cesium conditioning. The maximal PG current was independent of driver modification and it was lower in the case of inhibited cesium. The maximal extracted negative ion current depends on the potential difference between the near-PG plasma and the PG bias potentials, while the absolute value of plasma potential in the driver and in the PG area is less important for the negative ion production. The last conclusion confirms the main mechanism of negative ion production through the surface conversion of fast atoms.

Inductively driven surface-plasma negative ion source for N-NBI use (invited)

The long-pulse surface-plasma source prototype is developed at Budker Institute of Nuclear Physics for negative-ion based neutral beam injector use. The essential source features are (1) an active temperature control of the ion-optical system electrodes by circulation of hot thermal fluid through the channels, drilled in the electrode bodies, (2) the concaved transverse magnetic field in the extraction and acceleration gaps, preventing the electrons trapping and avalanching, and (3) the directed cesium deposition via distribution tubes adjacent to the plasma grid periphery. The long term effect of cesium was obtained just with the single cesium deposition. The high voltage strength of ion-optical system electrodes was improved with actively heated electrodes. A stable H(-) beam with a current ∼1 A and energy 90 keV was routinely extracted and accelerated.

High voltage holding in the negative ion sources with cesium deposition

High voltage holding of the large surface-plasma negative ion source with cesium deposition was studied. It was found that heating of ion-optical system electrodes to temperature >100 °C facilitates the source conditioning by high voltage pulses in vacuum and by beam shots. The procedure of electrode conditioning and the data on high-voltage holding in the negative ion source with small cesium seed are described. The mechanism of high voltage holding improvement by depletion of cesium coverage is discussed.

Two-dimensional wave-number spectral analysis techniques for phase contrast imaging turbulence imaging data on large helical device

An analysis method for unfolding the spatially resolved wave-number spectrum and phase velocity from the 2D CO2 laser phase contrast imaging system on the large helical device is described. This is based on the magnetic shear technique which identifies propagation direction from 2D spatial Fourier analysis of images detected by a 6 × 8 detector array. Because the strongest modes have wave-number at the lower end of the instrumental k range, high resolution spectral techniques are necessary to clearly resolve the propagation direction and hence the spatial distribution of fluctuations along the probing laser beam. Multiple-spatial point cross-correlation averaging is applied before calculating the spatial power spectrum. Different methods are compared, and it is found that the maximum entropy method (MEM) gives best results. The possible generation of artifacts from the over-narrowing of spectra are investigated and found not to be a significant problem. The spatial resolution Δρ (normalized radius) around the peak wave-number, for conventional Fourier analysis, is ∼0.5, making physical interpretation difficult, while for MEM, Δρ ∼ 0.1.

N-Substituted pyrazole-3-carboxamides as inhibitors of human 15-lipoxygenase

High-throughput screening was used to find selective inhibitors of human 15-lipoxygenase-1 (15-LOX-1). One hit, a 1-benzoyl substituted pyrazole-3-carboxanilide (1a), was used as a starting point in a program to develop potent and selective 15-LOX-1 inhibitors.

3-Substituted pyrazoles and 4-substituted triazoles as inhibitors of human 15-lipoxygenase-1

Investigation of 1N-substituted pyrazole-3-carboxanilides as 15-lipoxygenase-1 (15-LOX-1) inhibitors demonstrated that the 1N-substituent was not essential for activity or selectivity. Additional halogen substituents on the pyrazole ring, however, increased activity. Further development led to triazole-4-carboxanilides and 2-(3-pyrazolyl) benzoxazoles, which are potent and selective 15-LOX-1 inhibitors.

Comparative analysis of continuous-wave surface-plasma negative ion sources with various discharge geometry

Negative ion extraction from continuous-wave (CW) magnetron and semiplanotron discharges was studied and it was compared with that for the source with Penning electrode geometry. The CW negative ion beam up current to 13 mA was extracted from the magnetron source with emission aperture of 3.5 mm in diameter, while the beam with current up to 8 mA was obtained from the semiplanotron source modification. Characteristics of CW magnetron and semiplanotron sources are presented and analyzed.

The 25 mA continuous-wave surface-plasma source of H(-) ions

The ion source with the Penning geometry of electrodes producing continuous-wave beam of H(-) ions with current up to 25 mA was developed. Several improvements were introduced to increase source intensity, reliability, and lifetime. The collar around the emission aperture increases the electrons filtering. The apertures' diameters of the ion-optical system electrodes were increased to generate the beam with higher intensity. An optimization of electrodes' temperature was performed.

Development of a fluorescent intensity assay amenable for high-throughput screening for determining 15-lipoxygenase activity

15-Lipoxygenase-1 catalyzes the introduction of molecular oxygen into polyunsaturated fatty acids to form a lipid hydroperoxide. The authors have developed an assay for the detection of lipid hydroperoxides formed by human 15-lipoxygenase (15-LO) in enzyme or cellular assays using either a 96-well or a 384-well format. The assays described take advantage of the ability of lipid hydroperoxides to oxidize nonfluorescent diphenyl-1-pyrenylphosphine (DPPP) to a fluorescent phosphine oxide. Oxidation of DPPP yields a fluorescent compound, which is not sensitive to temperature and is stable for more than 2 h. The assay is sensitive toward inhibition and robust with a Z' value of 0.79 and 0.4 in a 96- and 384-well format, respectively, and thus amenable for high-throughput screening. The utility of DPPP as a marker for 15-lipoxygenase activity was demonstrated with both enzyme- and cell-based assays for the identification of hits and to determine potency by IC(50) determinations.

Detection of high k turbulence using two dimensional phase contrast imaging on LHD

High k turbulence, up to 30 cm(-1), can be measured using the two dimensional CO2 laser phase contrast imaging system on LHD. Recent hardware improvements and experimental results are presented. Precise control over the lens positions in the detection system is necessary because of the short depth of focus for high k modes. Remote controllable motors to move optical elements were installed, which, combined with measurements of the response to ultrasound injection, allowed experimental verification and shot-to-shot adjustment of the object plane. Strong high k signals are observed within the first 100-200 ms after the initial electron cyclotron heating (ECH) breakdown, in agreement with gyrotron scattering. During later times in the discharge, the entire k spectrum shifts to lower values (although the total amplitude does not change significantly), and the weaker high k signals are obscured by leakage of low k components at low frequency, and detector noise, at high frequency.

First experimental results from 2 MeV proton tandem accelerator for neutron production

A 2 MeV proton tandem accelerator with vacuum insulation was developed and first experiments are carried out in the Budker Institute of Nuclear Physics (Novosibirsk). The accelerator is designed for neutron production via reaction (7)Li(p,n)(7)Be for the boron neutron-capture therapy of the brain tumors, and for explosive detection based on 9.1724 MeV resonance gamma, which are produced via reaction (13)C(p,gamma)(14)N, absorption in nitrogen.

Direct current H(-) source for boron neutron capture therapy tandem accelerator

One year experience of dc H(-) source operation at 2 MeV tandem accelerator is described. The source delivers H(-) ion beams with controlled current in the range of 1-8 mA and energy up to 25 keV. Normalized 1 rms emittance for 8 mA beam is less than 0.2 pi mm mrad. Negative ions are produced on the cesiated anode of the Penning discharge, driven by plasma injection from the hollow cathode inserts.

Uncoated quartz resonator as a universal biosensor

We studied dynamic processes in drying drops of model protein-salt solutions, using an uncoated quartz resonator as a biosensor. To measure these processes we developed a method based on recording the dynamics of the Acoustic-Mechanical Impedance (AMI) of a drop as it dried on the surface of a quartz resonator oscillating at a resonant frequency of 60 kHz. The aim of this work was to highlight the role of some components of serum in self-organization processes. Human serum albumin (HSA), fibronectin (Fn), immunoglobulin G (IgG), immunoglobulin M (IgM), bovine serum albumin (BSA), sodium chloride (NaCl), Potassium Chloride (KCl), and nonionic surfactant O(CH(2)CH(2))(n)CH(2)CH(2)OH were used as components of the tested solutions. It was shown that dynamics of the AMI in drying drops were closely related to liquid composition. This approach allowed us to distinguish with good accuracy solutions in which one or more components (proteins or salts) were replaced by other components with the same mass concentration. We assumed that these differences were due to different surface properties and native functions of proteins, and different positions of salts in the Hofmeister line. Our preliminary work demonstrated that the dynamics of phase transitions in drying drops of serum could be used as an informative parameter for medical diagnostics. In this study, we highlight some positions in this cause-effect chain.

An exceptionally bright flare from SGR 1806–20 and the origins of short-duration γ-ray bursts

Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.

Maps of subsurface hydrogen from the high energy neutron detector, Mars Odyssey

After 55 days of mapping by the High Energy Neutron Detector onboard Mars Odyssey, we found deficits of high-energy neutrons in the southern highlands and northern lowlands of Mars. These deficits indicate that hydrogen is concentrated in the subsurface. Modeling suggests that water ice-rich layers that are tens of centimeters in thickness provide one possible fit to the data.

Biological activities of lipoteichoic acid and peptidoglycan-teichoic acid of Bacillus subtilis 168 (Marburg)

To evaluate the suitability of Bacillus subtilis as a production host of heterologous proteins for pharmaceutical purposes, we assessed the biological activity of this bacterium and its major cell envelope components, lipoteichoic acid (LTA) and peptidoglycan-teichoic acid complex (PG-TA) in several eukaryotic effector assays. LTA and PG-TA were found to be non-toxic for mice and guinea-pigs in a short-term toxicity assay. PG-TA was weakly pyrogenic and weakly mitogenic. Both LTA and PG-TA acted as immunologic adjuvants in mice and when injected in mice, also caused an increase in the number of granulocyte-monocyte colony-forming cells in the bone marrow probably via stimulation of production of granulocyte-macrophage colony-stimulating factor.