Direct Plasma Injection Research Articles

Extraction of ion beam from laser ion source for direct plasma injection scheme

Laser ion sources are expected to be used in various applications of heavy ion beam technology. The plasma direct injection scheme (DPIS) is a method in which ion beams extracted from a laser ion source are directly injected into a radio frequency quadrupole (RFQ) linear accelerator. In this study, a new shape of the plasma electrode with a concave surface for the DPIS was proposed to inject a converging beam to a cavity of RFQ accelerator. This approach allows the use of a large-diameter extraction electrode, which is not limited by the aperture of the RFQ electrode rods. The DPIS, using the concave surface electrode, was employed to accelerate C6+ ion beams. The results indicated that both the beam current and the number of ions increased nearly twice with the proposed electrode shape compared to values obtained with the conventional electrode. This enhancement corresponded to the increased extraction area of the beam.

Demonstration of an intense lithium beam for forward-directed pulsed neutron generation

As an alternative to research nuclear reactors, a compact accelerator-driven neutron generator that uses a lithium beam driver could be a promising candidate since it produces almost no undesired radiation. However, providing an intense lithium-ion beam has been difficult, and it has been thought that the practical application of such a device would be impossible. The most critical problem of insufficient ion fluxes has been solved by applying a direct plasma injection scheme. In this scheme, a pulsed high-density plasma from a metallic lithium foil generated by laser ablation is efficiently injected and accelerated by a radio-frequency quadrupole linear accelerator (RFQ linac). We have obtained a peak beam current of 35 mA accelerated to 1.43 MeV, which is two orders of magnitude higher than a conventional injector and accelerator system can deliver.

Neutron generator based on intense lithium beam driver.

We are proposing a compact neutron generator based on a Li beam driver. The proposed neutron generator comprises a laser ion source, a radio-frequency quadrupole linear accelerator (RFQ linac), a drift tube linac, and a target containing protons. In the generator, the lithium ion is used as a projectile instead of protons to utilize the kinematic focusing technique. The technique enables us to enhance the neutron flux without increasing the beam energy, which is important to develop a clean compact neutron generator. Moreover, the combination of a laser ion source and a RFQ linac with the direct plasma injection scheme will provide several tens of mA of a fully ionized lithium beam, which is much higher than that of conventional heavy ion sources comparable with proton drivers. Neutrons are generated by the nuclear reaction of the lithium ions and protons in the beam target. In this paper, we reported the current status of the development. For RFQ, we designed the RFQ rods to accelerate 40 mA of 7Li3+. We fabricated and installed the rods into a cavity, and, as a first test, accelerated 10 mA of C6+ successfully.

A visible to NIR emission conversion of CdS[sbnd]Ag2S by insertion of graphene oxide (GO) as template using direct atmospheric plasma injection

In this research GO-CdSAg2S nanohybrids were synthesized using a direct plasma injection in liquid phase for the first time. The luminescence properties of hybrid materials were investigated and compared to the same composite structure synthesized by microwave irradiation as a rapid and efficient tool. X-ray diffraction measurements revealed that CdS -Ag2S nanoparticles are formed on GO sheets with fine structural sizes. Energy dispersive x-ay spectroscopy showed the uniform distribution of Ag2S and CdS on GO sheets. TEM images showed the decoration of GO sheets with CdSAg2S particles with average sizes about 12 nm. Optical absorption analysis obtained size of CdS and Ag2S about 5 nm and 3 nm, respectively in analogy with TEM results. It means that the sole particles of CdS and Ag2S were not formed individually on GO sheets. Luminescence spectroscopy revealed that visible to near IR emission conversion can take place by addition of GO as template and using atmospheric plasma as treatment tool. The NIR emission peak is located around 745 nm.

Film formation from HMDSO: comparison of direct plasma injection with afterglow injection using an atmospheric pressure dielectric barrier discharge

The afterglow of a dielectric barrier discharge plasma was used for the film formation from Hexamethyldisiloxane (HMDSO) on silicon wafers. The process gas was argon with varying admixtures of HMDSO and oxygen. The silicon wafers were analyzed using white light interferometry and ATR-FTIR to characterize film volume and composition, respectively. The topology of deposited films was compared to a flow model to link the film thickness to flow velocity. Results show that deposition only occurs where flow velocity is low. Maximum film volume was observed at an oxygen admixture of 0.05 vol.%, while oxygen depletion for lower admixtures and plasma quenching at higher oxygen contents reduce the film formation. Additionally, film deposition depends on the residence time in the region where active species promote dissociation and on the density of active species in this region. Afterglow injection of HMDSO yields film deposition comparable to direct plasma injection with respect to volume and composition, eliminating the need of direct plasma treatment and preventing unwanted reactor deposition.

Synthesis of CdS Quantum Dots Using Direct Plasma Injection in Liquid Phase

In this work, we introduce a new method using non-equilibrium atmospheric pressure plasma jet (N-APPJ) for the synthesis of semiconductor quantum dots in liquid media with low power consumption at room temperature. In this method, the solution containing CdSO4, Na2S2O3 and thioglycolic acid (TGA) was treated by N-APPJ. Firstly, the key role of plasma applied voltage on the power consumption and the produced plasma reactive species was considered. We then continue to demonstrate that the optical properties such as absorption and photoluminescence of cadmium sulfide quantum dots (QDs) can carefully be controlled with the plasma parameters. Here, the effects of two major plasma parameters such as the plasma applied voltage and treatment time on the size of CdS QDs were investigated. The size of nanoparticles increases with the increase of the voltage and treatment time. It was also displayed that the change of the concentration of Na2S2O3 and TGA in the solution had no significant effect on the size of QDs in plasma method. Finally, X-ray diffraction, X-ray fluorescence spectrometry and transmission electron microscopy were employed to determine the composition, size and crystallinity of prepared CdS QDs.

Design of four-beam IH-RFQ linear accelerator

The multi-beam acceleration method is an acceleration technique for low-energy high-intensity heavy ion beams, which involves accelerating multiple beams to decrease space charge effects, and then integrating these beams by a beam funneling system. At the Tokyo Institute of Technology a two beam IH-RFQ linear accelerator was developed using a two beam laser ion source with direct plasma injection scheme. This system accelerated a carbon ion beam with a current of 108mA (54mA/channel×2) from 5 up to 60keV/u.In order to demonstrate that a four-beam IH-RFQ linear accelerator is suitable for high-intensity heavy ion beam acceleration, we have been developing a four-beam prototype. A four-beam IH-RFQ linear accelerator consists of sixteen RFQ electrodes (4×4 set) with stem electrodes installed alternately on the upper and lower ridge electrodes.As a part of this development, we have designed a four-beam IH-RFQ linear accelerator using three dimensional electromagnetic simulation software and beam tracking simulation software. From these simulation results, we have designed the stem electrodes, the center plate and the side shells by evaluating the RF properties such as the resonance frequency, the power loss and the electric strength distribution between the RFQ electrodes.

High power acceleration of an HSC type injector for cancer therapy**Supported by National Natural Science Foundation of China and One Hundred Person Project of CAS

A hybrid single cavity (HSC) linac, which is formed by combining a radio frequency quadrupole (RFQ) and a drift tube (DT) structure into one interdigital-H (IH) cavity, is fabricated and assembled as a proof of principle injector for cancer therapy synchrotron, based on the culmination of several years of research. The HSC linac adopts a direct plasma injection scheme (DPIS), which can inject a high intensity heavy ion beam produced by a laser ion source (LIS). The input beam current of the HSC is designed to be 20 mA C6+ ions. According to numerical simulations, the HSC linac can accelerate a 6-mA C6+beam, which meets the requirement of the needed particle number for cancer therapy (108–9 ions/pulse). The HSC injector with the DPIS method makes the existing multi-turn injection system and stripping system unnecessary, and can also bring down the size of the beam pipe in existing synchrotron magnets, which could reduce the whole cost of synchrotron. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured Q equal to 91% of the simulated value. A C6+ ion beam extracted from the LIS was used for the HSC commissioning. In beam testing, we found the measured beam parameters agreed with simulations. More details of the measurements and the results of the high power test are reported in this paper.

Iron plasma generation using a Nd:YAG laser pulse of several hundred picoseconds

We investigated the high intensity plasma generated by using a Nd:YAG laser to apply a laser-produced plasma to the direct plasma injection scheme. The capability of the source to generate high charge state ions strongly depends on the power density of the laser irradiation. Therefore, we focused on using a higher power laser with several hundred picoseconds of pulse width. The iron target was irradiated with the pulsed laser, and the ion current of the laser-produced iron plasma was measured using a Faraday cup and the charge state distribution was investigated using an electrostatic ion analyzer. We found that higher charge state iron ions (up to Fe(21+)) were obtained using a laser pulse of several hundred picoseconds in comparison to those obtained using a laser pulse of several nanoseconds (up to Fe(19+)). We also found that when the laser irradiation area was relatively large, the laser power was absorbed mainly by the contamination on the target surface.

High power test of an injector linac for heavy ion cancer therapy facilities

A hybrid single cavity (HSC) linac, combined with radio frequency quadrupole and drift tube structure in a single interdigital-H cavity, operates with high rf power as a prototype injector for cancer therapy synchrotron. The HSC adopts a direct plasma injection scheme (DPIS) with a laser ion source. The input beam current of the HSC is designed to be 20 mA ${\mathrm{C}}^{6+}$ ions. According to simulations, the HSC can accelerate a 6-mA ${\mathrm{C}}^{6+}$ beam which meets the requirement of the particle number for cancer therapy ($1{0}^{8\ensuremath{\sim}9}\text{ }\text{ions}/\text{pulse}$). The HSC injector with DPIS makes the existing multiturn injection system and stripping system unnecessary; what is more, it can also bring down the size of the beam pipe in existing synchrotron magnets, which can reduce the whole cost of the synchrotron. Details of the field measurements of the HSC linac and results of the high power test are reported in this paper.

Laser ion source activities at Brookhaven National Laboratory

In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, direct plasma injection scheme (DPIS) and conventional static extraction, are used depending on the application. We optimized and selected a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 × 1010 of C6+ ions using the DPIS. We successfully commissioned a low-charge ion beam provider to the user facilities in BNL. To achieve higher current, higher charge state and lower emittance, further studies will continue.

Simulation study on matching of laser ion source to RFQ linac with direct plasma injection scheme

Simulation study on matching of laser ion source to RFQ linac with direct plasma injection scheme

Generic on-line solid phase extraction sample preparation strategies for the analysis of drugs in biological matrices by LC–MS/MS

In the present work we investigate the integration of a single hardware platform (Prospekt-2) allowing on-line SPE with pre-/post-trapping dilution and direct injection of plasma extracts, and also compare the benefits and challenges of the different approaches for pharmaceutical drugs with heterogeneous physicochemical properties. In the first part, the generic use of on-line SPE with direct plasma injection or after protein precipitation was investigated for the quantitative analysis of talinolol. In the second part, pre-trapping and post-trapping dilution for on-line SPE is discussed for generic method development on an oxadiazole and its major metabolite. Finally, the difference of performance between direct plasma injection vs. off-line liquid–liquid extraction is also described for the quantification of buprenorphine and naltrexone down to 50 and 100pg/ml using a 0.25ml plasma aliquot. All assays were in human plasma and detection was performed by mass spectrometry detection either on simple or triple stage quadrupoles. Regardless of the tested strategy, assays were found linear, with precision and accuracy with <15% for all quality controls samples and <20% for lower limit of quantitation.

Simulation of direct plasma injection for laser ion beam acceleration with a radio frequency quadrupole.

The direct plasma injection scheme (DPIS) has been being studied at Institute of Modern Physics since several years ago. A C(6+) beam with peak current of 13 mA, energy of 593 keV/u has been successfully achieved after acceleration with DPIS method. To understand the process of DPIS, some simulations have been done as follows. First, with the total current intensity and the relative yields of different charge states for carbon ions measured at the different distance from the target, the absolute current intensities and time-dependences for different charge states are scaled to the exit of the laser ion source in the DPIS. Then with these derived values as the input parameters, the extraction of carbon beam from the laser ion source to the radio frequency quadrupole with DPIS is simulated, which is well agreed with the experiment results.

Measurement of beam characteristics from C6+ laser ion source

We developed a C(6+) laser ion source for a heavy-ion accelerator. A carbon target was irradiated with a Q-switched Nd:YAG laser (1064 nm wavelength, 1.4 J maximum laser energy, 10 ns pulse duration) to generate a high-density plasma. The laser ion source employed a rotating carbon target for continuous operation. Ion beams were extracted from the plasma through a drift space using a direct plasma injection scheme [B. Yu. Sharkov, A. V. Shumshurov, V. P. Dubenkow, O. B. Shamaev, and A. A. Golubev, Rev. Sci. Instrum. 63, 2841 (1992)] up to a maximum voltage of 40 kV. We measured the characteristics of the ion beams from the laser ion source and present the results of experiments here.

The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged (238)U(40+) (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

THE DESIGN OF A COMPACT RFQ NEUTRON GENERATOR

The output and target lifetime of a conventional electrostatic neutron generator are limited by the voltage stand-off capability and the acceleration of molecular species from the ion source. As an alternative, we suggest that the deuterium beam achievable from a compact high intensity ECR source can be injected directly into a compact RFQ to produce a more efficient compact neutron production system. Only the d+ ions are accelerated by the RFQ, which can also produce much higher output energies than electrostatic systems, resulting in a higher neutron output with a longer target lifetime. The direct injection of the beam makes the system more compact than the multielement, electrostatic systems typically used for extraction of the beam and subsequent transport and matching into the RFQ. We have designed and optimized a combined extraction/matching system for a compact high current deuterium ECR ion source injected into a high frequency RFQ structure, allowing a beam of about 12 mA of d+ ions to be injected at a modest ion source voltage of 25 kV. The end wall of the RFQ resonator serves as the ground electrode for the ion source, resembling DPI (direct plasma injection). For this design, we used the features of the code IGUN to take into account the electrostatic field between the ion source and the RFQ end wall, the stray magnetic field of the ECR source, the defocusing space charge of the low energy deuteron beam, and the rf focusing in the fringe field between the RFQ vanes and the RFQ flange.

Iron beam acceleration using direct plasma injection scheme

A new set of vanes of radio frequency quadrupole (RFQ) accelerator was commissioned using highly charged iron beam. To supply high intensity heavy ion beams to the RFQ, direct plasma injection scheme (DPIS) with a confinement solenoid was adopted. One of the difficulties to utilize the combination of DPIS and a solenoid field is a complexity of electro magnetic field at the beam extraction region, since biasing high static electric field for ion extraction, RFQ focusing field, and the solenoid magnetic field fill the same space simultaneously. To mitigate the complexity, a newly designed magnetic field clamps were used. The intense iron beam was observed with bunched structure and the total accelerated current reached 2.5 nC.

Simultaneous Determination of Protein-Free and Total Positron Emission Tomography Radioligand Concentrations in Plasma Using High-Performance Frontal Analysis Followed by Mixed Micellar Liquid Chromatography: Application to [11C]PBR28 in Human Plasma

A two-dimensional liquid chromatographic (LC) system was developed for the determination of protein-free and total (free + bound forms) positron emission tomography (PET) radioligand concentrations in plasma by direct plasma injection. The unbound PET radioligand was first analyzed by high-performance frontal analysis using a short gel-filtration column and phosphate buffered saline solution as the mobile phase. All the collected effluent from the gel-filtration column was then transferred to the second dimension consisting of a monolithic C-18 column and mixed (anionic and nonionic surfactants) micellar eluent for determination of the total PET radioligand concentration. The simultaneous analysis of protein binding and radiometabolism of [(11)C]PBR28 was completed within 11 min without any pretreatment of plasma and employing a single analytical system. This system allowed highly sensitive analysis of total [(11)C]PBR28 with a limit of detection (LOD) of 1.6 becquerel (Bq). The LOD for the determination of unbound [(11)C]PBR28 was 21 Bq. Finally, simultaneous measurements of protein binding and radiometabolism of [(11)C]PBR28 in human plasma were achieved for up to 50 min after radioligand administration.

Development of high intensity linear accelerator for heavy ion inertial fusion driver

In order to verify the direct plasma injection scheme (DPIS), an acceleration test was carried out in 2001 using a radio frequency quadrupole (RFQ) heavy ion linear accelerator (linac) and a CO2-laser ion source (LIS) (Okamura et al., 2002) [1]. The accelerated carbon beam was observed successfully and the obtained current was 9.22mA for C4+. To confirm the capability of the DPIS, we succeeded in accelerating 60mA carbon ions with the DPIS in 2004 (Okamura et al., 2004; Kashiwagi and Hattori, 2004) [2,3]. We have studied a multi-beam type RFQ with an interdigital-H (IH) cavity that has a power-efficient structure in the low energy region. We designed and manufactured a two-beam type RFQ linac as a prototype for the multi-beam type linac; the beam acceleration test of carbon beams showed that it successfully accelerated from 5keV/u up to 60keV/u with an output current of 108mA (2×54mA/channel) (Ishibashi et al., 2011) [4]. We believe that the acceleration techniques of DPIS and the multi-beam type IH-RFQ linac are technical breakthroughs for heavy-ion inertial confinement fusion (HIF). The conceptual design of the RF linac with these techniques for HIF is studied. New accelerator-systems using these techniques for the HIF basic experiment are being designed to accelerate 400mA carbon ions using four-beam type IH-RFQ linacs with DPIS. A model with a four-beam acceleration cavity was designed and manufactured to establish the proof of principle (PoP) of the accelerator.