Control system for the new RIKEN 28-GHz superconducting electron cyclotron resonance ion source for SRILAC

A new RIKEN 28-GHz superconducting electron cyclotron resonance ion source (SC-ECRIS) has been installed for the superconducting RIKEN linear accelerator (SRILAC). The new SC-ECRIS control system mainly consists of programmable logic controllers (PLCs) embedded with the Experimental Physics and Industrial Control System. To improve the reliability as compared with previous control systems, two types of PLC central processing units, sequential and Linux, have been installed in the same unit. Past experience has shown that new types of designs that can rapidly respond to system scalability are key. By connecting PLC stations using star-topology field buses, their rapid and cost-effective response to system changes is realized for the new devices. Furthermore, a unique data acquisition system employing a 920-MHz-band radio was developed to measure analog data such as the temperature at the high-voltage stage.

High intensity vanadium beam for synthesis of new superheavy elements with well-controlled emittance by using "slit triplet"

To provide a very powerful vanadium (V) beam with an intensity of at least 6 particle μA for synthesizing a new superheavy element (SHE) with atomic number Z = 119, we have developed a high-temperature oven (HTO) system to evaporate the metallic V powder inside the new superconducting (SC) electron cyclotron ion source. We successfully extracted a V¹³⁺ beam with a maximum beam intensity of 600 eμA with 2.8-kW microwave power and 900-W heating power of the HTO. Furthermore, from a systematic study of the dependence of the beam intensity on the microwave power and the HTO power, we successfully produced a V¹³⁺ beam of 300 eμA at a consumption rate of 3 mg/h, allowing a one-month duration continuous beam to carry out the SHE synthesis. In addition, to avoid serious damage to newly introduced SC acceleration cavities by beam losses, the beam should be transported with a well-controlled emittance. To efficiently limit the beam emittance, we employed a slit triplet consisting of three pairs of slits installed around the focus point of the low-energy beam transport. The first result of the emittance reduction was observed by a pepper-pot type emittance meter as a function of the acceptance of the slit triplet.

Progress in high-temperature oven development for 28 GHz electron cyclotron resonance ion source

We have been developing a high-temperature oven using UO2 in the 28 GHz superconducting electron cyclotron resonance ion source at RIKEN since 2013. A total of eleven on-line tests were performed. The longest operation time in a single test was 411 h, and the consumption rate of UO2 was approximately 2.4 mg/h. In these tests, we experienced several problems: the ejection hole of a crucible was blocked with UO2 and a crucible was damaged because of the reduction of tungsten strength at high temperature. In order to solve these problems, improvements to the crucible shape were made by simulations using ANSYS.

Control system renewal for efficient operation in RIKEN 18 GHz electron cyclotron resonance ion source

A RIKEN 18 GHz electron cyclotron resonance ion source (18 GHz ECRIS) is used as an external ion source at the Radioactive Ion Beam Factory (RIBF) accelerator complex to produce an intense beam of medium-mass heavy ions (e.g., Ca and Ar). In most components that comprise the RIBF, the control systems (CSs) are integrated by the Experimental Physics and Industrial Control System (EPICS). On the other hand, a non-EPICS-based system has hardwired controllers, and it is used in the 18 GHz ECRIS CS as an independent system. In terms of efficient and effective operation, the 18 GHz ECRIS CS as well as the RIBF CS should be renewed using EPICS. Therefore, we constructed an 18 GHz ECRIS CS by using programmable logic controllers with embedded EPICS technology. In the renewed system, an operational log system was developed as a new feature, for supporting of the 18 GHz ECRIS operation.

Note: Effect of hot liner in producing 40,48Ca beam from RIKEN 18-GHz electron cyclotron resonance ion source

In order to produce a high-intensity and stable (48)Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we have begun testing the production of a calcium beam using a micro-oven. To minimize the consumption rate of the material ((48)Ca), we introduced the "hot liner" method and investigated the effect of the liner on the material consumption rate. The micro-oven was first used to produce the (48)Ca beam for experiments in the RIKEN radioisotope beam factory, and a stable beam could be supplied for a long time with low consumption rate.

Implementation of an operator intervention system for remote control of the RIKEN 28 GHz superconducting electron cyclotron resonance ion source

The control system for the RIKEN 28 GHz superconducting electron cyclotron resonance ion source (28 GHz SC-ECRIS) consists of a distributed control system based on the experimental physics and industrial control system. To maintain the beam quality for the long beam-service time at the radioactive isotope beam factory, beam tuning to prevent subtle changes in the 28 GHz SC-ECRIS conditions is required. Once this is achieved, it should then be possible to check conditions and operate the ion source at any time. We have designed a web-based operational interface to remotely control the ion source, but for access and control from several locations, suitable access security, policies, and methods are required. We thus implemented an operator intervention system that makes it possible to safely access the network externally with the permission of on-site accelerator operators in the control room.

Recent development of RIKEN 28 GHz superconducting electron cyclotron resonance ion source

Over the past two years, we have tried to improve the performance of the RIKEN superconducting electron cyclotron resonance ion source using several methods. For the production of U vapor, we chose the sputtering method because it is possible to install a large amount of material inside the plasma chamber and thus achieve long-term operation without a break, although it is assumed that the beam intensity is weaker than in the oven technique. We also used an aluminum chamber instead of a stainless steel one. Using these methods, we successfully produced ∼180 eμA of U(35+) and ∼230 eμA of U(33+) at the injected radio frequency (RF) power of ∼4 kW (28 GHz). Very recently, to further increase the beam intensity of U(35+), we have started to develop a high temperature oven and have successfully produced a highly charged U ion beam. In this contribution, we report on the beam intensity of highly charged U ions as a function of various parameters (RF power and sputtering voltage) and discuss the effects of these parameters on the beam stability in detail.

Development of a high-temperature oven for the 28 GHz electron cyclotron resonance ion source

We have been developing the 28 GHz ECR ion source in order to accelerate high-intensity uranium beams at the RIKEN RI-beam Factory. Although we have generated U(35+) beams by the sputtering method thus far, we began developing a high-temperature oven with the aim of increasing and stabilizing the beams. Because the oven method uses UO2, a crucible must be heated to a temperature higher than 2000 °C to supply an appropriate amount of UO2 vapor to the ECR plasma. Our high-temperature oven uses a tungsten crucible joule-heated with DC current of approximately 450 A. Its inside dimensions are ϕ11 mm × 13.5 mm. Since the crucible is placed in a magnetic field of approximately 3 T, it is subject to a magnetic force of approximately 40 N. Therefore, we used ANSYS to carefully design the crucible, which was manufactured by machining a tungsten rod. We could raise the oven up to 1900 °C in the first off-line test. Subsequently, UO2 was loaded into the crucible, and the oven was installed in the 28 GHz ECR ion source and was tested. As a result, a U(35+) beam current of 150 μA was extracted successfully at a RF power of approximately 3 kW.

Operational test of micro-oven for 48Ca beam

In order to supply a high-intensity and stable (48)Ca beam from the RIKEN 18-GHz electron cyclotron resonance ion source, we are conducting operational tests of a micro-oven. A mixture of CaO and Al powders is placed into the crucible of the micro-oven and heated to produce metallic calcium by a reductive reaction. The successful production of a calcium beam was confirmed. In addition, we reduced the material consumption rate by using a so-called "hot liner," and we enhanced the beam intensity by applying a negative voltage bias to the micro-oven, the effect of which is similar to the effect of a "biased disk."

Production of a highly charged uranium ion beam with RIKEN superconducting electron cyclotron resonance ion source

A highly charged uranium (U) ion beam is produced from the RIKEN superconducting electron cyclotron resonance ion source using 18 and 28 GHz microwaves. The sputtering method is used to produce this U ion beam. The beam intensity is strongly dependent on the rod position and sputtering voltage. We observe that the emittance of U(35+) for 28 GHz microwaves is almost the same as that for 18 GHz microwaves. It seems that the beam intensity of U ions produced using 28 GHz microwaves is higher than that produced using 18 GHz microwaves at the same Radio Frequency (RF) power.

Results of RIKEN superconducting electron cyclotron resonance ion source with 28 GHz

We measured the beam intensity of highly charged heavy ions and x-ray heat load for RIKEN superconducting electron cyclotron resonance ion source with 28 GHz microwaves under the various conditions. The beam intensity of Xe(20+) became maximum at B(min) ∼ 0.65 T, which was ∼65% of the magnetic field strength of electron cyclotron resonance (B(ECR)) for 28 GHz microwaves. We observed that the heat load of x-ray increased with decreasing gas pressure and field gradient at resonance zone. It seems that the beam intensity of highly charged heavy ions with 28 GHz is higher than that with 18 GHz at same RF power.

First results from the new RIKEN superconducting electron cyclotron resonance ion source (invited)

The next generation heavy ion accelerator facility, such as the RIKEN radio isotope (RI) beam factory, requires an intense beam of high charged heavy ions. In the past decade, performance of the electron cyclotron resonance (ECR) ion sources has been dramatically improved with increasing the magnetic field and rf frequency to enhance the density and confinement time of plasma. Furthermore, the effects of the key parameters (magnetic field configuration, gas pressure, etc.) on the ECR plasma have been revealed. Such basic studies give us how to optimize the ion source structure. Based on these studies and modern superconducting (SC) technology, we successfully constructed the new 28 GHz SC-ECRIS, which has a flexible magnetic field configuration to enlarge the ECR zone and to optimize the field gradient at ECR point. Using it, we investigated the effect of ECR zone size, magnetic field configuration, and biased disk on the beam intensity of the highly charged heavy ions with 18 GHz microwaves. In this article, we present the structure of the ion source and first experimental results with 18 GHz microwave in detail.

Measurement of plasma potential of liquid-He-free superconducting electron cyclotron resonance ion source

The plasma potential of liquid-He-free superconducting electron cyclotron resonance ion source was measured as a function of minimum strength of mirror magnetic field (B(min)) and gas pressure with the method based on the retarding electric field. We observed that the plasma potential decreased with increasing B(min) up to 0.5 T and then gradually increased again. The plasma potential increased with increasing gas pressure. When we add the O(2) gas to the Ar plasma (gas mixing method), plasma potential gradually decreased with increasing the O(2) gas pressure.

New superconducting electron cyclotron resonance ion source for RIKEN RI beam factory project

For RIKEN radio isotope beam project, we started to construct the new superconducting electron cyclotron resonance ion source (SC-ECRIS), which has an operational frequency of 28 GHz, in 2007. The main feature of this ion source is that we can produce large size of resonance zone with six sets of solenoid coils. Before starting, we intensively studied the effect of several key parameters of ECRIS (magnetic field configuration, microwave power density, negatively biased disk) on the plasma. In this article, we describe the effect of key parameters on the plasma and detailed structure of the new SC-ECRIS.

Production of U beam from RIKEN 18 GHz electron cyclotron resonance ion source

For the RIKEN radio isotope factory (RIBF) project, we produced the multicharged uranium beam with two methods. To produce lower charge state U ion beams (14+-20+) we used the UF(6) gas as an ionized gas. The typical beam intensity of U(14+-20+) was 2-1 particle microA at the extraction voltage of 14 kV. To produce higher charge state U ion beam (U(35+)), we chose the sputtering method. The beam intensity was 70 particle nA at the extraction voltage of 5.4 kV. Using this method, we successfully produced multicharged U beam continuously for one month without break for RIBF commissioning.

[Detection methods for drug-resistant bacteria in routine examination--MRSA]

Since methicillin-resistant Staphylococcus aureus(MRSA) is resistant not only to methicillin but also to multiple species of antibacterial drugs, there are cases where infections with MRSA are difficult to treat. For laboratory identification of MRSA, S. aureus is first identified, then an oxacillin (MPIPC) sensitivity test, PCR detection of the S. aureus mecA gene and an agglutination test using the latex sensitized with an anti-PBP-2' monoclonal antibody are usually utilized. However, the detection of MRSA does not necessarily indicate MRSA infection, and many cases only demonstrate MRSA colonization. Thus, a clinical investigation is indispensable for establishing the diagnosis of MRSA infection. In addition, recent reports also suggested a current trend toward decreasing sensitivity to Bactroban(MUP, mupirocin, an anti-intranasal MRSA antibacterial drug). Taking these into consideration, surveillance of the trend in patient's sensitive to various species of antibacterial drugs including MUP must continue further.

Molecular epidemiological investigation using a randomly amplified polymorphic DNA assay of Burkholderia cepacia isolates from nosocomial outbreaks

We experienced two Burkholderia cepacia outbreaks over a 1-year period. During this period, 28 B. cepacia isolates were obtained from clinical specimens, and 2 were obtained from environmental specimens (i.e., from a nebulizer solution and a nebulizer tube). These 30 isolates were subjected to the PCR-based randomly amplified polymorphic DNA (RAPD) assay as well as to pulsed-field gel electrophoresis (PFGE). In the first outbreak, in which eight patients hospitalized in the Trauma and Critical Care Center were involved, the RAPD assay revealed that all 20 isolates obtained from clinical specimens and the 2 isolates from environmental specimens had identical DNA profiles. These RAPD data enabled us to pinpoint a possible source and to take countermeasures to prevent further spread of the epidemic-causing strain. In the second outbreak, two consecutive B. cepacia infection/colonization cases were seen in the surgery ward. The RAPD profiles of four isolates obtained were again identical, but they were distinct from those seen in the first outbreak, clearly indicating that the second outbreak was not related to the first. Thus, our experience demonstrated that the RAPD assay is a useful and reliable tool for epidemiological studies of B. cepacia isolates from nosocomial outbreaks. Since the RAPD assay could provide discriminatory potential and reproducibility comparable to those of the widely used PFGE assay with less complexity and in a shorter time, the introduction of the RAPD assay into hospital microbiology laboratories as a routine technique may help prevent nosocomial outbreaks.

[The in vitro antibacterial activity of cefozopran against clinically isolated bacteria]

The in vitro antibacterial activity of cefozopran (CZOP) against recent clinical isolates was evaluated and compared with those of ceftazidime (CAZ), cefpirome (CPR), cefepime (CFPM), cefotaxime (CTX), sulbactam/cefoperazone (S/C), imipenem (IPM), oxacillin (MPIPC), and flomoxef (FMOX). MIC80 values of CZOP for methicillin-susceptible Staphylococcus aureus (MSSA, n = 41), methicillin-resistant Staphylococcus aureus (MRSA, n = 57), Streptococcus pneumoniae (n = 45), Enterococus faecalis (n = 49), Enterobacter cloacae (n = 50), Citrobacter freundii (n = 45), Serratia marcescens (n = 45), and Pseudomonas aeruginosa (n = 100) were 1, 32, 2, 16, 4, 1, 0.25, 8 micrograms/ml, respectively. CZOP was more active than CPR against P. aeruginosa and exhibited similar activity to CPR against other species. CZOP was especially active against S. marcescens with MIC values lower than 1 microgram/ml against all strains tested. CZOP was similarly active to or more active than CFPM against all species except for C. freundii. CZOP was not active against MRSA. Thus, we investigated the in vitro combination effects of CZOP/vancomycin (VCM) and CZOP/arbekacin (ABK) using the checkerboard method. The interaction between CZOP and VCM ranged from additive activity (0.5 < FIC index < or = 1.00, n = 37) to synergistic activity (FIC index < 0.50, n = 1), except for one strain showing indifference (1.00 < FIC index < or = 2.00). The interaction between CZOP and ABK ranged from additive activity (n = 22) to synergistic activity (n = 1). These date suggest the potential effect of combination therapy of (CZOP) and VCM or ABK against MRSA. The combined therapy is suggested to be useful to reduce side effects in patients with impared renal function, to reduce the administration dose of VCM or to treat infections of sites where achievable drug concentrations are lower than those commonly achieved in the bloodstream. We also investigated the combination effects of CZOP/AMK and CZOP/GM against CZOP-resistant P. aeruginosa (MIC > 16 micrograms/ml). The combination of CZOP/AMK showed additive activity (n = 9) to synergistic activity (n = 2). The combination of CZOP/GM showed additive activity (n = 5). These results suggest that combinations of CZOP with AMK or GM are effective in treating P. aeruginosa.