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Background Dependent on existing deep to superficial perforating venous branches, the WavelinQ EndoAVF System is a novel technique used to create an arteriovenous fistula (AVF) between ulnar or radial veins and concomitant arteries for dialysis access. We sought to examine a single center’s success rates and short-term follow-up using this device. Methods All consecutive patients undergoing placement of a WavelinQ AVF from October 2018 to July 2019 were included. Preoperative/intraoperative variables including demographics, preoperative/postoperative duplex ultrasonography, success rate of procedure, and subsequent endovascular/surgical procedures were obtained. Descriptive statistics and comparison of groups requiring subsequent intervention were performed. Results Thirty-five patients underwent placement of the WavelinQ AVF, with 32 (91%) patients having at least one documented follow-up. These patients were predominantly male (23/32, 72%) with an average age of 60.2 and 23 of 32 (72%) patients were on dialysis. Initial fistula creation success rate was 100%. Average procedural length was 120 min, fluoroscopy time 9.6 min, and contrast usage 52.2 mL. Eight of 32 (25%) patients had perioperative complications (3 hematomas, 3 contrast extravasations, 1 resolved vessel spasm all resolving spontaneously, and 1 pseudoaneurysm requiring surgical repair). Thirteen of 32 (41%) patients underwent subsequent endovascular interventions to assist with maturation [9/32 (28%) branch coiling, 5/32 (16%) angioplasty/stenting, and 3/32 (9%) access thrombectomy] and 4 of 32 (13%) patients required subsequent surgical interventions (1 pseudoaneurysm repair, 1 revision of fistula, and 2 definitive AVF creation in thrombosed grafts). The majority of accesses (30/32, 94%) were ulnar–ulnar fistulas and overall patency at average follow-up of 73 days was 88% (28/32) with average brachial artery inflow volume of 1,078 cc/min and average cephalic vein (18/32) outflow volume of 447 cc/min. Eleven of 23 (48%) patients on dialysis were successfully using the EndoAVF at follow-up. Conclusions The WavelinQ AVF system has a high initial procedural success rate, although a significant portion of patients require subsequent endovascular procedures to aid in maturation. Further work on determining factors predictive of need for reintervention is necessary.

With increased social isolation due to COVID-19, social media has been increasingly adopted for communication, education, and entertainment. We sought to understand the frequency and characteristics of social media usage among general surgery trainees.General surgery trainees in 15 American training programs were invited to participate in an anonymous electronic survey. The survey included questions about demographics, frequency of social media usage, and perceptions of risks and benefits of social media. Univariate analysis was performed to identify differences between high users of social media (4-7 h per week on at least one platform) and low users (0-3 h or less on all platforms).One hundred fifty-seven of 591 (26.6%) trainees completed the survey. Most respondents were PGY3 or lower (75%) and high users of social media (74.5%). Among high users, the most popular platforms were Instagram (85.7%), YouTube (85.1%), and Facebook (83.6%). YouTube and Twitter were popular for surgical education (77.3% and 68.2%, respectively). The most reported benefits of social media were improving patient education and professional networking (85.0%), where high users agreed more strongly about these benefits (P = 0.002). The most reported risks were seeing other residents (42%) or attendings (17%) with unprofessional behavior. High users disagreed more strongly about risks, including observing attendings with unprofessional behavior (P = 0.028).Most respondents were high users of social media, particularly Instagram, YouTube, and Facebook. High users incorporated social media into their surgical education while perceiving more benefits and fewer risks of social media.

We report high-power microwave oscillation of a 94 GHz gyrotron, contributing to the study on air breakdown plasma in Microwave Rocket. The gyrotron is demountable, adopting a diode magnetron injection gun and a built-in quasi-optical mode converter, installed in a compact superconducting magnet with a bore diameter of 100 mm. In this study, microwave signal was detected using a pyroelectric detector and a liquid thermograph sheet at the beam voltage of 40 kV and beam current of about 20 A. Besides, air breakdown plasma, useful for the thrust generation of Microwave Rocket, was successfully ignited at atmospheric pressure. The observed plasma's filamentary structure at the propagation velocity of 720 m/s was different from 170 GHz, which indicates a frequency dependence of the plasma structure.

To realize the GW-class power source for Microwave Rocket, the cost reduction of gyrotrons is one of the solutions to lower the threshold to realize the beam station. In this study, a sub-MW-class gyrotron which adapted a smaller bore diameter of the superconducting magnet was designed and developed. The output power, pulse duration, and frequency are respectively 600 kW, $100\ \mu\mathrm{s}$ , and 94 GHz. The electron current is driven by a charged capacitor bank and in-house IGBT switches. The gyrotron tube was aligned with the superconducting magnet to achieve high electric efficiency.

Objectives Major depression is associated with increased morbidity and mortality in vascular surgery patients. The US Preventive Services Task Force and American Heart Association recommend routine depression screening for adults, especially those with cardiovascular disease. Since routine depression screening has not been implemented in most vascular surgery clinics across the nation, we sought to determine the feasibility of depression screening and understand the prevalence and predictors of depression in patients presenting to a single institution’s vascular surgery clinic over a 4 month period. Methods From June to September 2020, vascular surgery clinic patients were administered a 26-item survey that included validated scales for depression (PHQ-9), pain, frailty, alcohol dependence, and nicotine dependence. Although not validated, the Rosenberg Self-Esteem Scale was also administered. Patient charts were reviewed for demographic information and medical history. 9-digit patient zip codes were used to determine Area Deprivation Index, a measure of socioeconomic status. Univariate and multivariate analyses were performed to understand the factors associated with increased depression prevalence in the study population. Results A total of 140 (36.4%) of 385 patients met study inclusion criteria. 35.7% of them screened positive for mild to severe depression (PHQ-9 scores ≥5). On univariate analysis, major depression was significantly associated with lower socioeconomic status ( p = 0.007), higher frailty ( p < 0.001), lower self-esteem ( p < 0.001), higher daily pain ( p < 0.001), health problems that interfere with social activities ( p < 0.001), fatigue ( p < 0.001), unmarried status ( p = 0.031), and lack of primary care provider ( p = 0.048). Multivariate analyses significantly predicted higher frailty (B= 0.487, p = 0.007) and lower self-esteem (B= −0.413, p < 0.001) in patients with depression. Depression was not associated with gender, age, employment status, smoking status, alcohol use, or type of vascular disease. Coclusions More than one-third of vascular surgery clinic patients have comorbid depression. Higher frailty and lower self-esteem are significant risk factors for depression. Prevention and early identification of frailty may improve outcomes. Depression screening in vascular surgery clinics is feasible and could be useful in determining which patients may benefit from more frequent follow-up and monitoring for associated comorbidities. Vascular surgeons may play an important role in screening for depression and referring patients for psychotherapy and/or pharmacotherapy.

Introduction Screening for peripheral artery disease (PAD) with the ankle-brachial index (ABI) test is currently not recommended in the general population; however, previous studies advocate screening in high-risk populations. Although providers may be hesitant to prescribe low-dose rivaroxaban to patients with coronary artery disease (CAD) alone, given the reduction in cardiovascular events and death associated with rivaroxaban, screening for PAD with the ABI test and accordingly prescribing rivaroxaban may provide additional benefits. We sought to describe the cost-effectiveness of screening for PAD in patients with CAD to optimize this high-risk populations’ medical management. Methods We used a Markov model to evaluate the ABI test in patients with CAD. We assumed that all patients screened would be candidates for low-dose rivaroxaban. We assessed the cost of ABI screening at $100 per patient and added additional charges for physician visits ($100) and rivaroxaban cost ($470 per month). We used a 30-day cycle and performed analysis over 35 years. We evaluated quality-adjusted life years (QALYs) from previous studies and determined the incremental cost-effectiveness ratio (ICER) according to our model. We performed a deterministic and probabilistic sensitivity analyses of variables with uncertainty and reported them in a Tornado diagram showing the variables with the greatest effect on the ICER. Results Our model estimates decision costs to screen or not screen at $94,953 and $82,553, respectively. The QALYs gained from screening was 0.060, generating an ICER of $207,491 per QALY. Factors most influential on the ICER were the reduction in all-cause mortality associated with rivaroxaban and the prohibitively high cost of rivaroxaban. If rivaroxaban cost less than $95 per month, this would make screening cost-effective based on a willingness to pay threshold of $50,000 per QALY. Conclusions According to our model, screening patients with CAD for PAD to start low-dose rivaroxaban is not currently cost-effective due to insufficient reduction in all-cause mortality and high medication costs. Nevertheless, vascular surgeons have a unique opportunity to prescribe or advocate for low-dose rivaroxaban in patients with PAD to improve cardiovascular outcomes.

Medical students and residents often evaluate training sites in vascular surgery with minimal exposure to those programs. We sought to identify factors associated with vascular surgery trainee satisfaction in relation to their current work environment and how they made their rank list.All integrated residents and fellows currently in United States vascular training programs were queried using an anonymous electronic survey for variables of their current training environment, factors that influenced their rank order list, and satisfaction. Questions were graded on a Likert scale. Continuous, ordinal, and categorical variables were respectively analyzed using the two-sample t-test, Mann-Whitney U-test/Wilcoxon rank sum test, and Fisher's exact test.A total of 166 of 517 (32%) trainees completed the survey with equal distribution across postgraduate years. Respondents reported high rates of satisfaction with their training program overall (84%), including 88% (n = 83) of residents and 78% (n = 56) of fellows. Several work environment variables were associated with both resident and fellow satisfaction including program-funded trips for conferences and presentations (P = 0.027 for residents; P = 0.001 for fellows), diversity of operative cases (P = 0.024; P 0.001), perception of a strong supportive social network at the hospital (P = 0.006; P = 0.001), and perception of appreciation by attending surgeons (P 0.001; P 0.001). Fellows who felt appreciated by nursing staff (P = 0.047), ancillary staff (P = 0.013), and patients were more likely to be satisfied (P = 0.011); however, this was not true for integrated residents. Social outings with nontrainee family and friends were associated with satisfaction for fellows (P = 0.002) but not integrated residents (P = 0.138), whereas social outings with vascular trainees were associated with satisfaction for integrated residents (P = 0.047) but not fellows (P = 0.375). Similarly, satisfied integrated residents were more likely to have close relationships with their vascular cotrainees (P = 0.035) than fellows (P = 0.349). No rank list factors were found to be predictive of current trainee satisfaction for integrated residents. Rank list factors associated with fellow satisfaction included recommendation of the institution from a mentor (P 0.001), success of program graduates (P = 0.002), faculty (P = 0.014), perceived program prestige (P = 0.040), and amount of early operative exposure (P = 0.042).Vascular surgery trainees report a high level of satisfaction with their training program. Fellow satisfaction was more dependent on the perception of their workplace peers than integrated residents. Satisfied integrated residents were more likely to have close relationships with their vascular cotrainees than fellows.

Supplemental Material, Appendix_A for Factors Associated With Medication Adherence in Vascular Surgery Patients by Hataka R. Minami, Mark S. Zemela, Adam C. Ring, Michael S. Williams and Matthew R. Smeds in Vascular and Endovascular Surgery

Thermal conductive plates in devices such as power modules for automobiles require materials which has performances such as high thermal conductivities and acceptable electric breakdown strengths. To this end, herein polymethylmethacrylate (PMMA)/hexagonal boron nitride (h-BN) composite materials with the flaky surface of h-BN oriented parallel to the thickness direction are fabricated by an electrostatic adsorption method. To investigate the influence of the molding temperature and measurement temperature on the composites, DC breakdown tests and thermal conductivity measurements are performed. In addition, conduction current measurements are used to estimate the volume resistivity. As the molding temperature increases, the DC breakdown strength decreases and the thermal conductivity increases. Additionally, the DC breakdown strength decreases as the measurement temperature increases. These results suggest that thermal processes might lead to breakdown and the thermal conductivity slightly decreases as the measurement temperature increases. The effect of the negative temperature dependence of the thermal conductivity in h-BN is greater than that of the positive temperature dependence in PMMA. Further, the volume resistivity decreases as the h-BN content increases, and the estimated volume resistivity with a 60% h-BN content is about 60 GΩ•cm.

This paper describes the results of the experiments performed on Tandem Mirror device GAMMA 10/PDX mainly using a new “divertor simulation experimental module (D-module)” installed on one of the end mirror exits which is specially designed to investigate the physics of plasma detachment. The additional ICRF heating in the anchor-cells, connected to both ends of the central-cell, significantly increases the density in the both cells, which attained the generation of the highest particle flux up to 1023 particles/s m2 at the end-mirror exit. H2 and noble gas injection to enhance the radiation cooling in D-module was performed and a remarkable reduction of the electron temperature (from few tens eV to

In the GAMMA 10 tandem mirror, divertor simulation experiments that utilize particle flux toward the west end region (called end-loss flux) have been implemented. Since a positive correlation has b...

Development of an electron cyclotron heating (ECH) mirror antenna and MW gyrotrons for power modulation experiments in GAMMA 10 has been started in order to generate and control the high heat flux and to make the edge-localized mode (ELM)-like intermittent heat load pattern for divertor simulation studies. A peak heat flux of more than 10 MW/m2 on the GAMMA 10 axis has been obtained during ECH injection within the available power of ECH. This value almost corresponds to the steady-state heat load of the divertor plate of ITER. However, we need a substantial upgrade of the heating power to approach the ITER level ELM energy density. We carry out a design study for a mirror antenna and higher power gyrotrons in order to generate higher intermittent heat flux in GAMMA 10 tandem mirror for future divertor simulation studies.

This paper describes the recent results of divertor simulation research toward the realization of the detached plasma using the end-mirror of a large tandem mirror device. The additional ion cyclotron range of frequency heating in the anchor-cells for higher particle flux generation significantly increases the density, which attained the highest particle flux up to 1.76 × 1023 particles/·m2 at the end-mirror exit. Massive gas injection (H2 and noble gases) into the divertor simulation experimental module (D-module) was performed, and a remarkable reduction of the electron temperature on the target plate was successfully achieved associated with the strong reduction of particle and heat fluxes in D-module. Two-dimensional images of Hα emission in D-module observed with a high-speed camera showed strong emission in the upstream region and significant reduction near the target plate. These results clarified the effect of radiation cooling and formation of detached plasma due to gas injection. It is a...

At the Plasma Research Center at University of Tsukuba, development of megawatt gyrotrons is being performed as a collaborative electron cyclotron heating (ECH) study with some research organizatio...

This paper describes the results of characterization of high heat and particle fluxes produced at the end-cell of the large tandem mirror GAMMA 10 and of the initial plasma-irradiation experiments. In the case of ICRF plasmas, the heat flux of 0.8 MW/m and the particle flux of 4 × 10/m s were achieved at the end-mirror exit. The heat flux increases with the ICRF power and has a linear relationship with the stored energy. Direct ion energy analysis clarified that the parallel ion temperature can be controlled from 100 eV to 400 eV by changing the ICRF power. Additional plasma heating using another ICRF system in the anchor-cell significantly increases the particle flux, which gives a clear prospect of generating the higher particle flux by applying additional ICRF heating in the neighboring cells. The initial results of the plasma-gas-material interactions on a new V-shaped tungsten target were also reported. © 2013 Elsevier B.V. All rights reserved.

GAMMA 10/PDX project is the development of the mirror devices to aim the fusion-reactor relevant research using the potential control and the end loss as the particle and heat fluxes for transport,...

Divertor simulation study has been started as a new research plan, by making best use of a large linear plasma device. The experiment of generating the plasma flow with high heat and particle flux was successfully performed at an end-mirror exit of the GAMMA 10 tandem mirror. In typical hot-ion-mode plasmas, the heat-flux density of 0.6 MW/m2 and the particle-flux density of 1022 particles/s m2 were simultaneously achieved in the case of only ICRF heating and superimposing the 300 kW ECH pulse attained the peak value of the net heat-flux up to 8 MW/m2 on axis. The above experimental results and the simulation analysis of ICRF heating using the Fokker-Planck code give a clear prospect of generating the required performance for divertor studies by building up the plasma heating systems to the end-mirror cell. Detailed behavior of the plasma flow and the future research plan are also described. © 2010 Elsevier B.V. All rights reserved.

The latest development achievements in the University of Tsukuba of over-1 MW power level gyrotrons required in present-day fusion devices, GAMMA 10, Large Helical Device (LHD), QUEST, Heliotron J and NSTX, are presented. The obtained maximum outputs are 1.9 MW for 0.1 s on the 77 GHz LHD tube and 1.2 MW for 1 ms on the 28 GHz GAMMA 10 one, which are new records in these frequency ranges. In long-pulse operation, 0.3 MW for 40 min at 77 GHz and 0.54 MW for 2 s at 28 GHz are achieved. A new programme of 154 GHz 1 MW development has started for high-density plasma heating in LHD. On the first 154 GHz tube, 1.0 MW for 1 s is achieved. As a next activity of the 28 GHz gyrotron, an over-1.5 MW gyrotron is designed and fabricated to study the multi-MW oscillation. The possibility of 0.4 MW continuous wave and 2 MW level output in operations of a few seconds, after the improvements of output window and mode converter, is shown. Moreover, a new design study of dual-frequency gyrotron at 28 and 35 GHz has started, which indicates the practicability of the multi-purpose gyrotron. © 2013 IAEA, Vienna.

The suppression of the potential fluctuation was clearly observed by a gold neutral beam probe (GNBP) during the higher potentials and positive electric fields driven by electron cyclotron heating. The particle flux evaluated from the phase difference between the potential and density fluctuations measured by GNBP showed the radial outward flux and correlates with the decrease in the stored energy. When flux is suppressed by the potential formation, the quick plasma stored energy increase is observed.

Electron Cyclotron Resonance Heating (ECRH) has contributed to the achievement of high performance plasma production, high electron temperature plasmas and sustainment of steady-state plasmas in the Large Helical Device (LHD). Our immediate targets of upgrading the ECRH system are 5 MW several seconds and 1 MW longer than one hour power injection into LHD. The improvement will greatly extend the plasma parameter regime. For that purpose, we have been promoting the development and installation of 77 GHz/1-1.5 MW/several seconds and 0.3 MW/CW gyrotrons in collaboration with University of Tsukuba. The transmission lines are re-examined and improved for high and CW power transmission. In the recent experimental campaign, two 77 GHz gyrotrons were operated. One more gyrotron, which was designed for 1.5 MW/2 s output, was constructed and is tested. We have been promoting to improve total ECRH efficiency for efficient gyrotron-power use and efficient plasma heating, e.g. a new waveguide alignment method and mode-content analysis and the feedback control of the injection polarization. In the last experimental campaign, the 77 GHz gyrotrons were used in combination with the existing 84 GHz range and 168 GHz gyrotrons. Multi-frequency ECRH system is more flexible in plasma heating experiments and diagnostics. A lot of experiments have been performed in relation to high electron temperature plasmas by realization of the core electron-root confinement (CERC), electron cyclotron current drive (ECCD), Electron Bernstein Wave heating, and steady-state plasma sustainment. Some of the experimental results are briefly described. © 2009 American Institute of Physics.

In the tandem mirror GAMMA 10, plasma confinement is achieved not only by the magnetic mirror configuration but also by the high potentials at both end regions. Before applying plug–electron cyclotron resonance heating (P-ECH), drift-type fluctuations were observed in the potential and density measurements. The suppression potential and density of these fluctuations were clearly determined by using a gold neutral beam probe (GNBP) system during the potential formation by the application of P-ECH. We studied the relationship between the suppression levels of the potential fluctuations and the effects of potential produced by changing the applied electron cyclotron heating power. Moreover, the particle-flux-related values obtained by examining the phase difference between the potential and density fluctuations were measured by using the GNBP. We clearly show that radial anomalous transport induces radial particle transport, which decreases the stored energy of the plasma.

As the new research plan of Plasma Research Center of the University of Tsukuba, we are planning to start a study of divertor simulation under the closely resemble to actual fusion plasmas environment making an advantage of the GAMMA 10 tandem mirror and to contribute the solution for realizing the divertor in future toroidal systems. In the research plan, the concepts of two divertor devices are introduced. One has an axi-symmetric divertor configuration with separatrix (A-Div.) and the other is a high heat flux divertor simulator by using an end-mirror exit of the large tandem mirror device (EDiv.). Preparative experiments have been successfully started at the end-mirror region of GAMMA 10 and detailed behavior of end-loss particles has been investigated by using newly developed diagnostic instruments. In standard hot-ion mode plasmas (ne0 ~ 2x1018 m-3, Ti0 ~ 5 keV), the heat flux density of 0.8 MW/m2 and the particle flux density of 4x10 22 /s·m2 were observed at 30 cm downstream of the end-mirror exit on the machine axis. It is confirmed that the heat flux density increases in proportion to the applied RF power. Superimposing the ECH pulse induces a remarkable enhancement of heat flux and a peak value in the net heat flux density of 8 MW/m2 was attained during the ECH injection, which almost comes up to the heat load level of the divertor plate of ITER. Two-dimensional visible image measurement of newly installed target plates using highspeed camera revealed a significant difference in the behavior of visible emission from plasma-material interaction. The above results give a clear prospect of generating the required performance and providing useful information for divertor studies in GAMMA 10.

We are planning to start a study of divertor simulation under the closely resemble to actual fusion plasma environment making use of the advantage of open magnetic field configuration and to contribute the solution for realizing the divertor in ITER as a future research plan of Plasma Research Center of the University of Tsukuba. In the research plan, the concepts of two divertor devices are introduced. One has an axi-symmetric divertor configuration with the separatrix which is similar to toroidal divertor of torus systems and the other is a high heat flux divertor simulator by using an end-mirror exit of the existing tandem mirror device. Development of magnetic field configuration for ensuring the MHD stability is under way and a designed example is investigated under the optimal condition for plasma production. Consideration of plasma heating scheme using Fokker-Planck simulation code was successfully performed at both axi-symmetric divertor and end-mirror regions. Preparative experiments using calorimeter, Mach probe and high-speed camera have been started at the end-mirror region and the heat flux density of the level in 1-10 MW m -2 was achieved in standard hot-ion mode plasma-confining experiments, which gives a clear prospect of generating the required heat flux density for divertor studies. © 2010 Elsevier B.V.

Recent progress and near future plan of GAMMA 10 efforts are presented. With high power plug electron cyclotron heating (ECH) up to ~ 400 kW, the ion confining potential of more than 2 kV was confirmed. The drift type low frequency fluctuations were suppressed by the positive radial electric field produced by plug ECH. It is found that the efficient EC heating on mirror devices from a strong B field side requires the minimization of the stray microwave in addition to the 100% X-mode excitation to avoid the enhancement of the ion loss. The development of a gyrotron, the key tool of these ECH experiments, has been made in collaboration with NIFS (National Institute for Fusion Science), More than 1.5 MWfor more than Is has been demonstrated at 77GHz. The plan of the boundary plasma research program with modification of GAMMA 10 is in progress. The new program includes the physics and technology studies of the divertor and SOL plasmas and PWI relevant to torus plasmas like ITER. The high heat flux experiments using the open end mirror throat has been started and we have obtained successful preliminary data, which include the heat flux of 8 MW/m2.

The electron cyclotron resonance heating (ECRH) system on the Large Helical Device (LHD) has been in stable operation for ∼11 yr in numerous plasma experiments. During this time, many upgrades to the system have been made, such as reinforcement of the gyrotron tubes, modification of the power supply depending on gyrotron type, and increase in the number of transmission lines and antennas. These efforts allow the stable injection of millimeter-wave power in excess of 2 MW. In parallel, various transmission components were evaluated, and antenna performance was confirmed at a high power level. The coupling efficiency of the millimeter wave from the gyrotron to the transmission line and the transmission efficiency through the waveguide were further improved in recent years. The feedback control of the wave polarization has also been tried to maximize the efficiency of wave absorption. The gyrotron oscillation frequency was reconsidered in order to extend the flexibility of the magnetic configuration in plasma experiments. The development of 77-GHz gyrotrons with the output of 1 MW per few seconds in a single tube is currently taking place in collaboration with the University of Tsukuba. Two such gyrotron tubes already have been installed and were used for plasma experiments recently. An ECRH system with a capability of the steady operation is required, because the LHD can continuously generate confinement magnetic fields using superconducting magnets. Not only the gyrotron but also the transmission system and components must withstand continuous power operation. Further acceleration of both the power reinforcement and a steady-state capability will allow the sustainment of high-performance plasmas.

A 77-GHz, 1-MW gyrotron is being newly installed in the Large Helical Device not only to enhance the total heating power but also to increase the possibility of controlling the local plasma parameters. Our progress in installing the new gyrotron and evaluating its properties is discussed. We have already finished the installation of the peripheral components, including the transmission line, and conducted a test at 1 MW for a short pulse. Our plan is to operate this gyrotron at a power of up to 1MW for 5 s. The conditioning of the gyrotron has been smoothly conducted, and a gyrotron output power up to 810 kWfor 3.6 s has been achieved so far. The total injected power of electron cyclotron resonance heating to the plasma reached a value of ∼2.5 MW.

The molecular basis of Group A xeroderma pigmentosum was investigated by restriction fragment length polymorphism analysis of PCR-amplified DNA sequences using the two restriction enzymes, endonucleases AlwN I and Hph I. The clones of a patient with Group A xeroderma pigmentosum who had typical symptoms showed a G-C substitution at the 3' splice acceptor site of intron 3. However, of the two atypical Group A xeroderma pigmentosum patients with mild skin lesions and minimal neurological abnormalities, the milder one showed homozygosity for the nonsense mutation of exon 6, while the other patient with slightly greater central nervous involvement was shown to be a compound heterozygote for the splicing mutation of intron 3 and the nonsense mutation of exon 6, thus indicating an allelic heterogeneity in group A xeroderma pigmentosum.

In this paper, detailed results of the heat flux measurements are presented and the improvement of heat flux evaluation method is also discussed. We measured the heat flux in the case that additional heating with electron cyclotron resonance heating (ECRH). The heat flux reaches about 17 MW/m2 in the case with ECRH power 380kW. It is found that solving one-dimensional inverse heat conduction problems provides a possibility of improving time response of the heat flux measurement under the condition of changing heat flux in 20Hz.

A computational code for the electromagnetic field in the cavity of high-power gyrotrons is developed. The gyrotron mechanism is described by a self-consistent set of equations taking into account the dependence of the axial structure of microwave oscillations on the relativistic electron beam in the cavity. The parameters of the electron beam are calculated using the EGUN electron trajectory code, and the effects of the space charge and the velocity spread of the electron beams are considered. The computational code includes a time-dependent description of the electromagnetic field and a self-consistent analysis of the electron beams. The equations are solved using a second-order predictor-corrector scheme. The calculations of the present study are carried out for a 1-MW gyrotron developed for the GAMMA10/PDX tandem mirror (80 kV, operating mode: TE94 mode, 35.45 GHz). The calculations reveal that, using a triode-type electron gun, stable excitation of the desired mode can be realized in standard startup...

This paper presents an overview of the recent progress of GAMMA 10/PDX project. In the GAMMA 10/PDX project, development of fusion reactor relevant research related to magnetic mirror devices has been conducted. One of the main objectives is divertor simulation studies under the similar condition of actual fusion devices, which contributes to comprehensive development strategy towards the divertor plasma physics and plasma wall interaction (PWI) studies. The recent progress of this research is that an additional plasma heating (ICRF and ECH) significantly increased the ion flux up to 3.3 × 1023 /m2 s at the end-mirror exit, which proved an effectiveness of additional plasma heating for generating high ion flux from the mirror end. Superimposing a short pulse of ECH produces the maximum heat flux of 21 MW/m2 by improving the west plug ECH antenna system, which exceeds the heat-load of ITER divertor plates. In detached plasma formation experiments using the divertor simulation experimental module (D-module)...

Electron cyclotron heating (ECH) power modulation experiments in GAMMA 10 tandem mirror have been carried out in order to generate and control the high heat flux and to make the ELM (edge localized mode) like intermittent heat load pattern for divertor simulation studies. The maximum energy density obtained by the use of present mirror antenna systems is about 0.08 MJ/m2 and is still far lower than that of ITER ELM. To achieve the generation of higher heat flux, the development of a new mirror antenna has carried out in order to concentrate the heating power on the axis. The calculated e-folding radius of power density has been improved from 63 mm for the present mirror to 40 mm for the new mirror antenna.

The high power and long pulse operation of the gyrotron as well as efficient transmission of its output are quite important for achieving improved plasma performances. A 28 GHz 1 MW gyrotron developed for GAMMA 10/PDX achieved an output power of 1.38 MW in 2015 experiment after the power supply was improved. Furthermore, a new 28/35 GHz dual-frequency gyrotron (2 MW 3 s and 0.4 MW CW) for QUEST, NSTX-U, Heliotron J and GAMMA 10/PDX has been fabricated, after the preliminary test of a double-disk sapphire window installed in the gyrotron was performed. In the first experimental test, the oscillation of the main mode was confirmed at a frequency of 28.036 GHz with a Gaussian-like beam and an output power of 1.22 MW.

The 170 GHz gyrotron for ITER demonstrated the stable and steady state 1000s operation with the output power of 0.6 MW and the efficiency of 45% by depressed collector. The remarkable progress was obtained with optimization of a built-in launcher and mirrors for significant reduction of the stray radiation to ∼2% of the output power, improvement of electron beam quality for high oscillation efficiency and control of constant beam current for stable oscillation. The result indicates a promising prospect for development of a I MW-CW-50%, 170 GHz ITER gyrotron.

In GAMMA 10, the upgrade program of high power plug and central ECRH have started for the study of the physics of plasma potential and the demonstration of high plasma performance proving the tandem mirror advantage. A new high power (upgrade) gyrotron has been developed in collaboration with JAEA from 2003 for this purpose and now three upgrade gyrotrons were installed in GAMMA 10. The first gyro torn in 2004 outputted about 500 kW power at the gyrotron window, corresponding to 400kW injection power to plasma. In 2005, the power of 570 kW at the window was obtained from the second one, which was improved mainly in mode converter. These gyrotron were applied to plug cells and a new record value of ion confining potential Φ c = 3 kV was obtained at 470 kW injection, which is four times higher than the previous value before 2003. For the central ECRH system, the upgrade of DC power supply was conducted using the DC power supply from JFT-2M ECH system and the system outputted 400kW at MOU out with the upgrade gyrotron. The central ECRH has been conducted with the combination of the new efficient antenna, transmission line and the upgrade gyrotron, and the initial experiment resulted Te ≥ 500eV.

Generalized scaling laws for the formation of plasma confining potentials are investigated to find the physics essentials common to representative tandem-mirror operational modes in GAMMA 10. These modes are characterized in terms of (i) a high-potential mode and (ii) a hot-ion mode. The potential-formation scalings in these modes are consolidated and generalized on the basis of the consistency with finding of the wider validity of Cohen's strong electron-cyclotron heating (ECH) theory covering over both modes. A plateau-shaped electron distribution function is observed when a plug electron-confining potential is formed in the hot ion mode of GAMMA 10, as predicted in terms of the strong ECH theory.

(1) Four-time progress in ion-confining potentials Φ c to 3.0 kV in comparison to Φ c attained 1992-2002 is achieved in the hot-ion mode (T i =several keV). A scaling of Φ c , which favorably increases with plug electron-cyclotron heating (ECH) powers (P PECH ), is obtained. (2) The advance in Φ c leads to a finding of remarkable effects of radially sheared electric fields (dEr/dr) on turbulence suppression and transverse-loss reduction. (3) A weak decrease in Φ c with increasing n c to ∼10 19 m -3 with the recovery of Φ c with increasing P PECH is obtained. (4) The first achievement of active control and formation of an internal transport barrier (ITB) has been carried out with the improvement of transverse energy confinement. Off-axis ECH in an axisymmetric barrier mirror produces a cylindrical layer with energetic electrons, which flow through the central cell and into the end region. The layer, which produces a localized bumped ambipolar potential Φ c , generates a strong E r shear and peaked vorticity with the direction reversal of E r ×8 sheared flow near the Φ c peak. Intermittent vortex-like turbulent structures near the layer are suppressed in the central cell. This results in T e and T i rises surrounded by the layer. The phenomena are analogous to those in tokamaks with ITB. (5) Preliminary central ECH (170 kW, 20 ms) in a standard tandem-mirror operation raises T e0 from 70 to 300 eV together with T ι⊥0 from 4.5 to 6.1 keV, and T i//0 from 0.5 to 1.2 keV with τ P0 =95 ms for Φ c (=1.4 kV) trapped ions. The on-axis particle to energy confining ratio of τ P0 /τ E0 is observed to be 1.7 for Φ c trapped ions (consistent with Pastukhov's theory) and 2.4 for central mirror-trapped ions with 240-kW plug ECH and 90-kW ICH (η ICH ∼0.3; nl c =4.5×10 17 m -2 ). (6) Recently, a 200 kW central ECH with 430 kW plug ECH produces stable central-cell plasmas (T e =600 eV and T i =6.6 keV) with azimuthal E r ×B sheared flow. However, in the absence of the shear flow, hot plasmas migrate unstably towards vacuum wall with plasma degradation.

A high efficiency launcher of quasi-optical (QO) mode converters for high power gyrotrons have been designed and tested. A helical cut launcher radiates the RF power via its straight cut onto the first phase correcting mirror. The launchers have been optimized for the TE31.8 mode at 170 GHz and TE22.6 mode at 110 GHz by numerically optimizing a launcher surface. The helical cut of the launcher has been optimized by taking the taper angle into account. Further more, the amplitude of the surface perturbation have been optimized for improved focusing in order to reduce the diffraction losses at the helical cut. Low power measurement shows a good agreement with the design. High efficiency characteristics of the design have also been calculated on the assumption of frequency downshift due to the thermal expansion of the cavity and stepwise frequency tuning by changing the operating mode. Besides, the possibility of high efficiency launcher for higher mode is discussed, and these results give the prospect to high efficiency long pulse gyrotrons.

In a pulse extension of a high-power gyrotron, a pulse duration was limited by the shift of the oscillation mode caused by a beam current decrease during the shot. The cause of the current decrease is the cathode cooling by the electron beam extraction. To keep the beam current constant, pre-programming control of the input power to the heater was applied. As an initial result, the stable and steady state operation of 1000 s with the output power of 0.2 MW was demonstrated on the 170 GHz gyrotron. Temperatures of the inner components of the gyrotron and cooling waters were constant, and the vacuum pressure was less than 10−5 Pa for 1000 s operation, which gives a prospect for CW operation at the higher power.

The conceptual study of the electron cyclotron heating and current drive (ECH/ECCD) system for a DEMO reactor was carried out. The ECH/ECCD system was considered on the basis of a design of the DEMO reactor by JAERI. The reactor is a low aspect ratio tokamak, and its size and magnetic field are similar to those of ITER. Therefore, many ECH/ECCD technologies developed at 170 GHz for ITER can be applied. Truly continuous operation is needed for DEMO, and the neutron fluence from the plasma is two orders of magnitude higher than that of ITER. An RF launcher that has reliability under the condition of high neutron fluence is, critically, important. For power deposition control in the plasma, a gyrotron frequency tuning system is considered as the primary candidate to realize a simple and robust launching system, but two RF beam steering systems are discussed as alternatives.