mA CW Research Articles

The High Beam to Power Efficiency Investigation of Miniaturized Microwave Ion Source

A miniaturized 2.45 GHz microwave ion source (MIS) with plasma chamber of ϕ30 mm × 40 mm that has the ability to produce more than 20 mA CW hydrogen ion beam with 180 W microwave power has been built at Peking University (PKU) 5 years ago1. A hibrid discharge principle has been proposed on this kind of MIS2. Recently, under the structure of this MIS, factors such as input power, pressure, magnetic field configuration and the size of plasma chamber have been investigated. Based on this research, a more compact 2.45 GHz microwave ion source with inner diameter of 24 mm has been developed. A 32.5 mA hydrogen ion beam was obtained with only 100 W microwave power.

Performance Investigations of InAs/InP Quantum-Dash Semiconductor Optical Amplifiers with Different Numbers of Dash Layers.

We present here a performance comparison of quantum-dash (Qdash) semiconductor amplifiers (SOAs) with three, five, eight, and twelve InAs dash layers grown on InP substrates. Other than the number of Qdash layers, the structures were identical. The eight-layer Qdash SOA gave the highest amplified spontaneous emission power (4.3 dBm) and chip gain (26.4 dB) at 1550 nm, with a 300 mA CW bias current and at 25 °C temperature, while SOAs with fewer Qdash layers (for example, three-layer Qdash SOA), had a wider ASE bandwidth (90 nm) and larger 3 dB gain saturated output power (18.2 dBm) in a shorter wavelength range. The noise figure (NF) of the SOAs increased nearly linearly with the number of Qdash layers. The longest gain peak wavelength of 1570 nm was observed for the 12-layer Qdash SOA. The most balanced performance was obtained with a five-layer Qdash SOA, with a 25.4 dB small-signal chip gain, 15.2 dBm 3 dB output saturated power, and 5.7 dB NF at 1532 nm, 300 mA and 25 °C. These results are better than those of quantum well SOAs reported in a recent review paper. The high performance of InAs/InP Qdash SOAs with different Qdash layers shown in this paper could be important for many applications with distinct requirements under uncooled scenarios.

Plasma simulation and optimization for a miniaturized antenna ECR ion source

At Peking University (PKU), a miniaturized 2.45 GHz antenna permanent magnet electron cyclotron resonance (PMECR) ion source, capable of generating a several-mA H+ beam, was produced and tested. The dimensions of the plasma chamber were ∅30 mm ×40 mm, and the entire size of the ion source (including the extraction system) supply was ∅150 mm ×160 mm. A 4.5 mA CW H+ beam was extracted at 35 kV with 200 W of microwave power supplied by a compact microwave generator with a coaxial cable. For a better understanding and optimization of the miniaturized ion source, plasma simulations were conducted to research the electromagnetic coupling of the antennas and the generation of ECR plasmas. The experimental and simulation results of the H+, H2+, and H3+ fractions of cylindrical-type and “T”-type antenna microwave ion sources were presented and compared. Based on a series of comparisons between the experimental and simulation results, the impedance of the miniaturized antenna ECR ion source plasma and the real pressure in the plasma chamber were accurately calculated. An optimized microwave coupling system was designed for the new miniaturized antenna ECR ion source. From the plasma simulation results, the transmission efficiency of microwaves increased from 32% to 89% (coupled to plasma), 15 mA H+ @ 150 W can be expected in the future.

Design and study of a continuous wave RFQ for the BISOL high intensity deuteron driver linac

A high intensity four-vane continue wave (cw) RFQ for the Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac has been designed. This RFQ will accelerate the 25 mA cw deuteron beam the 3.0 MeV with an operating frequency of 162.5 MHz. Three beam dynamics design schemes based on different strategies have been proposed and detailed comparisons, including tolerance study and error analysis, are performed to evaluate them. The final design of RFQ can achieve the requirements with a length of 5.29 m and the transmission of 99.1%. The inter-vane voltage is ramped from 60 kV to 75 kV and the maximum Kilpatrick factor is 1.42, which is very modest and beneficial to cw operation mode. The RFQ electromagnetic design is carried out based on the full-length 3D model, including vane modulation, undercuts, π-mode stabilization rods (PSLs) and tuners. The requirements of correct work frequency and voltage ramp are fulfilled by varying vane width and adjusting undercuts. In addition, the π-mode stabilization rods (PSLs) are inserted and optimized to increase mode separation and enhance voltage stabilization. The rf power loss and effective shunt impendence are 118 kW and 210 kΩ⋅m, respectively. In addition, multi-physics analysis of the cavity, based on the electromagnetic codes CST MWS, HFSS and ANSYS, has been carried out to check the cooling system, the temperature rise and deformation of the cavity, as well as the frequency shift in the cw operation. Finally, the frequency sensitivities to cooling water temperature are studied to obtain water temperature tuning coefficients, which will be used for fine tuning of the RFQ cavity during operation.

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 and testing of radio frequency modulated electron Gun at VECC, Kolkata

A superconducting electron linac (e-Linac) photo-fission driver is under construction at VECC for the upcoming rare isotope beam facility called ANURIB. The first stage consists of an injector linac based on 1.3 GHz superconducting radio frequency technology designed for accelerating 10 MeV, 2 mA CW electron beam. An rf modulated thermionic electron gun (E-Gun) has been developed and tested for this injector linac. The E-Gun will allow continuous beam operation up to 300 keV with around 3 pC charge per pulse at 650 MHz. Electron beam with RF modulation is extracted from the gun and intensity, energy, size of the DC beam as well as trans-conductance of the electron source are measured. The design of some major components for the electron gun and low energy beam transport line is discussed and results of beam tests are presented.

Development and beam commissioning of a continuous-wave window-type radio-frequency quadrupole

The radio-frequency quadrupole (RFQ) group at Peking University has built a window-type RFQ, operating at 162.5 MHz in continuous-wave (cw) mode. It is designed to accelerate a 50 mA deuteron beam from 50 keV to 1 MeV with a vane length of 1.809 m. The cavity was fabricated in two segments using 100% oxygen-free electronic (OFE) copper. Using an iterative assembly and measurement procedure for the precise alignment of the two segments, we reduced the assembly errors to within $\ifmmode\pm\else\textpm\fi{}0.05\text{ }\text{ }\mathrm{mm}$. The radio frequency (rf) measurements of the whole cavity show excellent rf properties, with the measured intrinsic Q-value of 8962, which equates to 96% of the simulated value for OFE copper. We also investigated field fluctuations caused by misalignment between the two segments, and studied their impact on the beam transmission using beam dynamics simulations. During field tuning, we compiled a set of unique tuning rules for the window-type RFQ. After tuning, the maximal field unflatness of the single quadrant is within $\ifmmode\pm\else\textpm\fi{}2%$, and the asymmetry of the four quadrants is within $\ifmmode\pm\else\textpm\fi{}1%$. During rf conditioning, the cw power of the cavity reached 55 kW within 32 hours, and we have recorded nearly seven hours of stable running at a cw power of 50 kW. The measured bremsstrahlung spectrum shows that the accelerator needs 49.9 kW to generate the intervane voltage of 60 kV, with a specific shunt impedance of $130.5\text{ }\text{ }\mathrm{k}\mathrm{\ensuremath{\Omega}}\text{ }\mathrm{m}$. An ${\mathrm{H}}_{2}^{+}$ ion beam extracted from an electron cyclotron resonance ion source was used for the beam commissioning, because deuteron beam acceleration will bring a serious radiation field. We achieved stable and robust acceleration of about 1.5 mA cw ${\mathrm{H}}_{2}^{+}$ beam for one hour.

Detailed study of RF properties of cold models for CW window-type RFQ

A 50 mA CW deuteron RFQ is being built for a joint 973 project between Peking University and the Institute of Modern Physics. This RFQ adopts a high-frequency window-type structure. To study its RF properties and to validate the reliability of an electromagnetic simulation, two full-length aluminum models with tuners were built in succession. RF measurements were obtained from the test bench and compared to the simulations, including frequencies, quality factors, and electric fields of different modes and the field in aperture. Through field tuning, the maximal field unflatness for a single quadrant and the average asymmetry of four quadrants were reduced from 8.7% and $$\pm \,$$ 3.6% to 5.8% and $$\pm \,$$ 1.7%, respectively. Moreover, a tuning method of adjusting the gap distance between the endplates and the vanes was also studied in this paper.

Beam diagnostics of an ECR ion source on LIPAc injector for prototype IFMIF beam accelerator

The IFMIF accelerator facility consists of 2 identical linacs, each accelerating a 125 mA CW deuteron beam up to the energy of 40 MeV. In order to reach these unprecedented performances, the Linear IFMIF Prototype Accelerator (LIPAc) is under installation and commissioning at the International Fusion Energy Research Centre (IFERC) in Rokkasho, Japan, in the framework of the IFMIF/EVEDA project, which is part of the Broader Approach (BA) agreement between Japan and EU. The accelerator is designed to validate components up to 125 mA CW deuteron beam at 9 MeV. The accelerator components of LIPAc have been designed and manufactured mainly by European Institutes. The injector and superconducting linac, RFQ, MEBT, Diagnostics Plate, HEBT and beam dump have been developed respectively by CEA-Saclay, INFN-Legnaro and CIEMAT-Madrid and were delivered to Rokkasho between 2013 and 2016. The commissioning of the injector with beam started in November 2014. This paper dealt with the experimental data obtained with the beam diagnostics of the injector. The electrical measurements of the beam intensity on the beam stopper were compared with calorimetric measurements. The beam profiles measured with a CCD camera and a custom image-intensified CID camera are also addressed. The analysis of beam emittance and ion species fractions from data obtained with an Allison scanner is described and the results of species fraction measurements are compared with those obtained by using a deported spectrometer. Finally, the analysis of beam space potential from data obtained with a 4-Grid analyser is presented.

The Soreq Applied Research Accelerator Facility (SARAF): Overview, research programs and future plans

The Soreq Applied Research Accelerator Facility (SARAF) is under construction in the Soreq Nuclear Research Center at Yavne, Israel. When completed at the beginning of the next decade, SARAF will be a user facility for basic and applied nuclear physics, based on a 40 MeV, 5 mA CW proton/deuteron superconducting linear accelerator. Phase I of SARAF (SARAF-I, 4 MeV, 2 mA CW protons, 5 MeV 1 mA CW deuterons) is already in operation, generating scientific results in several fields of interest. The main ongoing program at SARAF-I is the production of 30 keV neutrons and measurement of Maxwellian Averaged Cross Sections (MACS), important for the astrophysical s-process. The world leading Maxwellian epithermal neutron yield at SARAF-I ($5\times 10^{10}$ epithermal neutrons/sec), generated by a novel Liquid-Lithium Target (LiLiT), enables improved precision of known MACSs, and new measurements of low-abundance and radioactive isotopes. Research plans for SARAF-II span several disciplines: Precision studies of beyond-Standard-Model effects by trapping light exotic radioisotopes, such as $^6$He, $^8$Li and $^{18,19,23}$Ne, in unprecedented amounts (including meaningful studies already at SARAF-I); extended nuclear astrophysics research with higher energy neutrons, including generation and studies of exotic neutron-rich isotopes relevant to the rapid (r-) process; nuclear structure of exotic isotopes; high energy neutron cross sections for basic nuclear physics and material science research, including neutron induced radiation damage; neutron based imaging and therapy; and novel radiopharmaceuticals development and production. In this paper we present a technical overview of SARAF-I and II, including a description of the accelerator and its irradiation targets; a survey of existing research programs at SARAF-I; and the research potential at the completed facility (SARAF-II).

Alignment of beam position monitors in cryomodule of CADS injector II

Significant temperature difference (300–77 K or even 4 K) can cause large deformations and displacements of the beam position monitors (BPMs), which affect BPMs measurement resolution or even cause their malfunction in cryogenic situations. In this paper, to check the offset from the mechanical to electrical center in low temperature (77 K), Fourier’s law and finite element method are used to simulate cryo-deformation. Laser tracker and micro-alignment telescope are employed in combined BPM calibration, installation and monitoring. The calibration error is <0.02 mm, and the installation and monitoring precision are 0.06 mm and 0.01 mm, respectively. The monitored cryo-deformation agrees well with the simulation results. These indicate that the combined alignment can improve performance of the BPM system. All these guaranteed the success of running the 9.55 MeV@2.14 mA cw protons.

High-brightness semipolar (2021¯) blue InGaN/GaN superluminescent diodes for droop-free solid-state lighting and visible-light communications.

A high-brightness, droop-free, and speckle-free InGaN/GaN quantum well blue superluminescent diode (SLD) was demonstrated on a semipolar (2021¯) GaN substrate. The 447-nm emitting SLD has a broad spectral linewidth of 6.3 nm at an optical power of 123 mW. A peak optical power of 256 mW was achieved at 700 mA CW injection current. By combining YAG:Ce phosphor, SLD-generated white light shows a color-rendering index (CRI) of 68.9 and a correlated color temperature (CCT) of 4340 K. The measured frequency response of the SLD revealed a -3 dB bandwidth of 560 MHz, thus demonstrating the feasibility of the device for both solid-state lighting (SSL) and visible-light communication (VLC) applications.

Study of medium beta elliptical cavities for CADS*Supported by National Natural Science Foundation of China (91426303)

The China Accelerator-Driven Sub-critical System (CADS) is a high intensity proton facility to dispose of nuclear waste and generate electric power. CADS is based on a 1.5 GeV, 10 mA CW superconducting (SC) linac as a driver. The high energy section of the linac is composed of two families of SC elliptical cavities which are designed with geometrical beta 0.63 and 0.82. In this paper, the 650 MHz β=0.63 SC elliptical cavity is studied, including cavity optimization, multipacting, high order modes (HOMs) and generator RF power calculation.

Developmental plasticity of brain circuits for navigational behavior

Event Abstract Back to Event Developmental plasticity of brain circuits for navigational behavior Ying Shing Chan1*, F P. Botelho1, C W. Ma1, W Shi1 and Daisy K. Shum1 1 University of Hong Kong, School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, China With the use of graviceptive behavior as the readout, we have revealed the postnatal period critical for switching on the vestibular nucleus (VN) circuitry for display of such innate behavior in rats. Neonatal perturbation of the VN with agonist, antagonist, or neuromodulators of GABA-mediated transmission effected shifts in the time frame for postnatal emergence of the graviceptive behaviors. The perturbation exerted lasting impacts on spatial map formation in relay stations of the vestibular system as well as navigational behavior into adulthood. Zooming into the mechanism with use of brainstem slices of postnatal rats, we found modulations of pre-/post-synaptic efficacy of GABA-A receptor-mediated transmission among VN interneurons following treatment with endocannabinoid or BDNF. Altogether, tuning the vestibular network for spatial coding during a postnatal period of plasticity is critical for the expression of innate sensori-motor behaviors in young rats and the learning of navigational behavior in adults. Acknowledgements HKRGC-GRF 761812, 762313, N_HKU735/14 Keywords: BDNF, plasticity, vestibular nucleus, GABA-A, graviceptive behavior Conference: 14th Meeting of the Asian-Pacific Society for Neurochemistry, Kuala Lumpur, Malaysia, 27 Aug - 30 Aug, 2016. Presentation Type: Symposium 1: Motor Control and Sensorimotor Integration: Circuitry and Plasticity Topic: 14th Meeting of the Asian-Pacific Society for Neurochemistry Citation: Chan Y, Botelho FP, Ma CW, Shi W and Shum DK (2016). Developmental plasticity of brain circuits for navigational behavior. Conference Abstract: 14th Meeting of the Asian-Pacific Society for Neurochemistry. doi: 10.3389/conf.fncel.2016.36.00008 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Jul 2016; Published Online: 11 Aug 2016. * Correspondence: Prof. Ying Shing Chan, University of Hong Kong, School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, Hong Kong, Hong Kong SAR, China, yschan@hku.hk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ying Shing Chan F P Botelho C W Ma W Shi Daisy K Shum Google Ying Shing Chan F P Botelho C W Ma W Shi Daisy K Shum Google Scholar Ying Shing Chan F P Botelho C W Ma W Shi Daisy K Shum PubMed Ying Shing Chan F P Botelho C W Ma W Shi Daisy K Shum Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

SARAF Phase I linac operation in 2013–2014

Phase I of the SARAF superconducting RF linac is under operation at the Soreq Nuclear Research Center. The present status of Phase I main components is reported, as well as, the beam operation experience accumulated in 2013–2014. The latter include acceleration of a 2 mA and 1.6 mA CW proton beams at energies of 2 MeV and 3.9 MeV correspondingly and 1 mA pulsed, duty cycle of few %, deuteron beams up to 5.6 MeV. The recent experiments include operation of intense CW proton beams on the liquid lithium target.

Optimization of solenoid based low energy beam transport line for high current H+ beams

A 20 MeV, 30 mA CW proton linac is being developed at BARC, Mumbai. This linac will consist of an ECR ion source followed by a Radio Frequency Quadrupole (RFQ) and Drift tube Linac (DTL). The low energy beam transport (LEBT) line is used to match the beam from the ion source to the RFQ with minimum beam loss and increase in emittance. The LEBT is also used to eliminate the unwanted ions like H2+ and H3+ from entering the RFQ. In addition, space charge compensation is required for transportation of such high beam currents. All this requires careful design and optimization. Detailed beam dynamics simulations have been done to optimize the design of the LEBT using the Particle-in-cell code TRACEWIN. We find that with careful optimization it is possible to transport a 30 mA CW proton beam through the LEBT with 100% transmission and minimal emittance blow up, while at the same time suppressing unwanted species H2+ and H3+ to less than 3.3% of the total beam current.

Electromagnetic and beam dynamics studies of a high current drift tube linac for LEHIPA

We have performed detailed electromagnetic and beamdynamics studies of a 352.21 MHz drift-tube linac (DTL) that will acceleratea 30 mA CW proton beam from 3 to 20 MeV. At such high currents space chargeeffects are important, and therefore the effect of linear as well asnon-linear space charge has been studied (corresponding to uniform andGaussian initial beam distributions), in order to avoid space chargeinstabilities. To validate the electromagnetic simulations, a 1.2 m longprototype of the DTL was fabricated. RF measurements performed on theprototype were in good agreement with the simulations. A detailed simulationstudy of beam halos was also performed, which showed that beyond a currentof 10 mA, significant longitudinal beam halos are excited even for aperfectly matched beam, whereas for a mis-matched beam transverse beam halosare also excited. However, these do not lead to any beam loss within theDTL.

Dynamics of the IFMIF very high-intensity beam

AbstractFor the purpose of material studies for future nuclear fusion reactors, the IFMIF deuteron beams present a simultaneous combination of unprecedentedly high intensity (2 × 125 mA CW), power (2 × 5 MW) and space charge. Special considerations and new concepts have been developed in order to overcome these challenges. The global strategy for beam dynamics design of the 40 MeV IFMIF accelerators is presented, stressing on the control of micro-losses, and the possibility of online fine tuning. Start-to-end simulations without and with errors are presented for the prototype accelerator. Considerations about conflicts between halo and emittance minimization are then discussed in this very high space charge context.

Physics design of a CW high-power proton Linac for accelerator-driven system

Accelerator-driven systems (ADS) have evoked lot of interest the world over because of their capability to incinerate the MA (minor actinides) and LLFP (long-lived fission products) radiotoxic waste and their ability to utilize thorium as an alternative nuclear fuel. One of the main subsystems of ADS is a high energy (∼1 GeV) and high current (∼30 mA) CW proton Linac. The accelerator for ADS should have high efficiency and reliability and very low beam losses to allow hands-on maintenance. With these criteria, the beam dynamics simulations for a 1 GeV, 30 mA proton Linac has been done. The Linac consists of normal-conducting radio-frequency quadrupole (RFQ), drift tube linac (DTL) and coupled cavity drift tube Linac (CCDTL) structures that accelerate the beam to about 100 MeV followed by superconducting (SC) elliptical cavities, which accelerate the beam from 100 MeV to 1 GeV. The details of the design are presented in this paper.

The IFMIF-EVEDA challenges in beam dynamics and their treatment

Abstract One major system of the IFMIF project (International Fusion Materials Irradiation Facility) is its two accelerators producing the neutron flux by accelerating deuteron particles up to 40 MeV against a lithium target. In the first phase called EVEDA (Engineering Validation and Engineering Design Activity), a full scale prototype accelerating particles up to 9 MeV is being studied and constructed in Europe, to be installed in Japan. Two unprecedented performances are required for the IFMIF-EVEDA accelerators: very high power of 5 MW and very high intensity of 125 mA CW. This leads to numerous unprecedented challenges in beam dynamics design and optimisation: harmful losses even for those less than 10−6 of the beam, non-linear dynamics induced by very strong space charge forces, difficulties for equipment and diagnostic implementations in the high compact structure, need of specific tuning strategies in this context. These issues are highlighted in this article, and the ways in which they are addressed are detailed.