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High-degree atrioventricular block (HAVB) or complete heart block (CHB) is a common complication associated with transcatheter aortic valve replacement (TAVR). However, some patients with HAVB/CHB recover with time. The results of electrophysiological studies (EPSs) using permanent pacemaker implantation (PPI) in patients with suspicious HAVB/CHB are considered controversial.This study aimed to evaluate whether HAVB/CHB induction at the bedside using a temporary pacemaker can predict recurrence in patients who had recovered from HAVB/CHB after TAVR.We enrolled a total of 11 patients who had recovered from HAVB/CHB and evaluated their electrophysiology using right ventricular pacing and/or procainamide administration.HAVB/CHB induction was positive. Three patients tested positive for HAVB/CHB, whereas 8 tested negative. The ejection fraction and the interval between HAVB/CHB onset and EPS were found to be significant. HAVB/CHB positive patients underwent PPI. A patient with a balloon-expandable valve tested positive just before recovery of CHB, but tested negative 5 days later and was included in the negative group. The 4 patients who tested negative received a cardiovascular implantable electric device (CIED). We observed HAVB/CHB in 2 patients who had previously tested positive after 3 months. Among those who tested negative, those with CIED had no HAVB/CHB, and others showed neither HAVB/CHB on electrocardiogram nor experienced syncope or sudden death.Our EPS revealed that HAVB/CHB induction may predict HAVB/CHB recurrence after TAVR. Valve type and EPS timing may affect the results.

The development of a high-power EUV light source is very important in EUV lithography to overcome the stochastic effects for higher throughput and higher numerical aperture (NA) in the future. We have designed and studied a high-power EUV free-electron laser (FEL) based on energy-recovery linac (ERL) for future lithography. We show that the EUV-FEL light source has many advantages, such as extremely high EUV power without tin debris, upgradability to a Beyond EUV (BEUV) FEL, polarization controllability for high-NA lithography, low electricity consumption, and low construction and running costs per scanner, as compared to the laser-produced plasma source used for the present EUV lithography exposure tool. Furthermore, the demonstration of proof of concept (PoC) of the EUV-FEL is in progress using the IR-FEL in the Compact ERL (cERL) at the High Energy Accelerator Research Organization. In this paper, we present the EUV-FEL light source for future lithography and progress in the PoC of the EUV-FEL.

AimsThe aim of this study is to evaluate the clinical results of operative intervention for femoral metastases which were selected based on expected survival and to discuss appropriate surgical strategies.MethodsFrom 2002 to 2017, 148 consecutive patients undergoing surgery for femoral metastasis were included in this study. Prognostic risk assessments were performed according to the Katagiri and revised Katagiri scoring system. In general, the low-risk group underwent resection and reconstruction with endoprosthetic replacement (EPR), while the high-risk group underwent internal fixation (IF) and radiation therapy. For the intermediate-risk group, the operative choice depended on the patient’s condition, degree of bone destruction, and radio-sensitivity. Overall survival, local failure, walking ability, and systemic complications were evaluated.ResultsA total of 83 patients underwent EPR (low-risk, 23%; intermediate-risk, 60%; high-risk, 17%) and 65 patients underwent IF (low-risk, 0%; intermediate-risk, 32%; high-risk, 68%). The one-year survival rate was 71% for EPR and 15% for IF (p < 0.001). The one-year local failure-free survival was 93% for EPR and 67% for IF, and the two-year and five-year local failure-free survival for EPR were both 88% (p = 0.016). Although the ambulatory rate was 99% for EPR and 60% for IF, the median time to ambulation was shorter in the IF (EPR, 28 days, interquartile range (IQR) 25 to 35; IF, 23 days, IQR 18 to 28; p < 0.001) The cause of non ambulation was mainly due to progression of cancer (89%). The rate of systemic complications was comparable between the two groups (EPR, 18%; IF, 22%; p = 0.598).ConclusionSelective use of EPR where survival is expected to be good offers correspondingly good long-term results. IF is less invasive with shorter treatment period, which is beneficial for patients with short-term expected survival. Prognosis is an important indicator in selecting operative procedures for femoral metastasis. Cite this article: Bone Joint J 2020;102-B(3):285–292

The standard treatment for extraskeletal myxoid chondrosarcoma is wide excision. However, extraskeletal myxoid chondrosarcoma is often located in the deep layers of the extremities and pelvis, so functional impairment due to wide resection is unavoidable in many cases. In addition, the efficacy of radiotherapy and chemotherapy has not been defined, so no treatment method is established for unresectable cases. Here we report a case involving a man in his late 60s with extraskeletal myxoid chondrosarcoma of the pelvis who responded to proton beam radiotherapy with intra-arterial chemotherapy and did not require surgery. The patient maintained a complete response for more than 7 years. The findings from this case suggest that definitive irradiation can be an alternative to wide resection for cases of extraskeletal myxoid chondrosarcoma in which severe disability cannot be avoided after resection or when the tumour is inoperable due to its size and location.

Background Chondroblastomas are rare, benign, locally aggressive lesions that appear in the epiphysis. Surgery for femoral head chondroblastoma (FHCB) is difficult. Conventional treatment with curettage via a drilled tunnel along the femoral neck can damage the growth plate and is associated with high local recurrence rates. The trapdoor procedure, which directly facilitates lesion access from the femoral head articular surface, can reduce local recurrence and avoid growth plate damage, although it requires surgical dislocation. Little is known about the long-term results of this direct articular surface approach, and there are no case reports on trapdoor procedures without dislocation. Case presentation We report two cases (patients aged 12 and 15 years) of FHCB presented with coxalgia treated using the trapdoor procedure without surgical dislocation. Both surgeries were performed with patients in the semi-lateral position. The hip joint was exposed via an anterior approach, and a capsulotomy was performed at the superior rim of the acetabulum, followed by the external rotation of the hip joint. With a fine osteotome, a rectangular flap (trapdoor) was opened on the cartilage surface in the lateral non-weight-bearing area, and curettage of the lesion followed by bone and/or bone substitute grafting was performed. Subsequently, the trapdoor was replaced in its original position. There has been no local recurrence or femoral head aseptic necrosis after more than 6 and 12 years for patients 1 and 2, respectively. Both patients had musculoskeletal tumor society scores of 100% at follow-up and are enjoying a normal active life. Conclusions This direct femoral head approach without dislocation may be a simple treatment alternative for FHCB.

Multi-stack chips comprised of sapphire and Nd3+:YAG crystals with variable doping concentration were made by surface activated bonding technology. By use of sophisticated amplification setup for end-pumped solid-state laser, >2J operation with nanosecond pulses was obtained under room temperature.

An ERL(energy recovery linac)-based EUV-FEL can provide EUV power of more than 1 kW for multiple scanners to overcome stochastic noise and to achieve higher throughput. An IR-FEL project started at the KEK cERL for the purpose of developing high-power IR lasers for high-efficiency laser processing, and it can demonstrate proof of concept of the EUV-FEL for future lithography. We will briefly review the EUV-FEL and present construction and commissioning of the cERL IR-FEL including future work.

High-degree atrioventricular block (HAVB) or complete heart block (CHB) is a common complication associated with transcatheter aortic valve replacement (TAVR). However, some patients with HAVB/CHB recover with time. The results of electrophysiological studies (EPSs) using permanent pacemaker implantation (PPI) in patients with suspicious HAVB/CHB are considered controversial.This study aimed to evaluate whether HAVB/CHB induction at the bedside using a temporary pacemaker can predict recurrence in patients who had recovered from HAVB/CHB after TAVR.We enrolled a total of 11 patients who had recovered from HAVB/CHB and evaluated their electrophysiology using right ventricular pacing and/or procainamide administration.HAVB/CHB induction was positive. Three patients tested positive for HAVB/CHB, whereas 8 tested negative. The ejection fraction and the interval between HAVB/CHB onset and EPS were found to be significant. HAVB/CHB positive patients underwent PPI. A patient with a balloon-expandable valve tested positive just before recovery of CHB, but tested negative 5 days later and was included in the negative group. The 4 patients who tested negative received a cardiovascular implantable electric device (CIED). We observed HAVB/CHB in 2 patients who had previously tested positive after 3 months. Among those who tested negative, those with CIED had no HAVB/CHB, and others showed neither HAVB/CHB on electrocardiogram nor experienced syncope or sudden death.Our EPS revealed that HAVB/CHB induction may predict HAVB/CHB recurrence after TAVR. Valve type and EPS timing may affect the results.

Pro-gastrin-releasing peptide (ProGRP) is an established tumor marker of small cell lung cancer. The purpose of this study was to determine if ProGRP could serve as a tumor marker for the Ewing sarcoma family of tumors (ESFTs). Sixteen patients with ESFTs (mean age 32 years) were included in this study. As a control group, 42 patients with other tumor types that clinically or pathologically mimic ESFTs were also analyzed. Pre-treatment serum ProGRP and neuron-specific enolase (NSE) levels, the relationships between these levels, and tumor volume were investigated. In addition, serial changes in the serum or plasma ProGRP (6 patients) and NSE levels (5 patients) were measured over the course of treatment. Pre-treatment serum ProGRP levels were higher than the normal range in 8 of 16 patients; for these eight patients, ProGRP levels positively correlated with tumor volume (R = 0.99). In the control group, ProGRP levels were within the normal range, except for the two patients. Changes in ProGRP levels during treatment were consistent with tumor volume. Serum NSE levels were elevated in 14 of 16 patients with ESFTs and 8 of 42 patients with other tumor types. The range of NSE elevation was much smaller compared to that of ProGRP. Our data indicate that ProGRP is superior to NSE in terms of specificity. Serum ProGRP levels were elevated in half of the patients with ESFTs and reflected therapeutic response. ProGRP is a reliable tumor marker for the diagnosis of ESFTs and evaluation of treatment response.

An 8-MeV linear proton medical accelerator designed with a high RF duty operation is being developed at Ibaraki Neutron Medical Research Center for iBNCT (Ibaraki - Boron Neutron Capture Therapy). The reliability and stability of the cooling water control system has become one of the most important issues in realizing the medical application of the accelerator, which is designed considering high performance and low costs. However the previous cooling water control system with a commercial PID (Proportional–Integral–Differential) controller could not meet the operation requirements of the medical accelerator. Therefore, a new intelligent cooling water controller is successfully developed by application of Fast Feed-forward for Future (FFF). The detailed design of the intelligent cooling water control system and its great efficacy in improving accelerator operation is described in this paper. The stability of the cooling water temperature is improved greatly from the previous ± 0 . 30 ° C to the current ± 0 . 03 ° C. Moreover, the response time of cooling water control is decreased dramatically from the previous 5 min to approximately 20 s. Precise operation and an excellent auto-tuning of the RFQ (Radio Frequency Quadrupole LINAC) cavity are realized by using this stable and intelligent water control system. The beam transmittance is also improved slightly after a fine scan experiment with different settings of RF devices under stable acceleration operation. Finally, the RF startup time is also reduced by using this intelligent cooling water control system. Now the iBNCT accelerator operation is greatly improved with a very high reliability and stability. The accelerator will be operated as a practical medical therapy in late 2019. The technology developed in this intelligent cooling water control system will be very useful for the development of similar accelerators with high performance and low cost.

Following an era of the use of several drug-coated balloons in angioplasty, “leave nothing behind” and stentless strategies have been gaining attention. In stentless strategies, it is necessary to avoid major dissections and limit flow. Balloon dilation is an important step in vessel preparation. In this study, we report a novel predilation technique. We performed prolonged balloon inflation for >10 min after normal ballooning in a procedure to treat an occluded lesion in the superficial femoral artery (SFA). We used a guide extension catheter to avoid foot ischemia and obtained better angiographic results than those using short duration balloon inflation. We named this technique “Ultra-Long Inflation in SFA Stenosis and Occluded Lesions Using Guide Liner” or “Ultra SOUL.” The Ultra SOUL technique may be considered a useful option in balloon dilation.

At Ibaraki Neutron Medical Research Center, an 8-MeV proton linear accelerator is being developed for iBNCT (Ibaraki - Boron Neutron Capture Therapy), with the aim of achieving the highest possible performance at a low cost. In this accelerator, there are two RF cavities driven by only one high-power klystron as the RF source. A digital low-level RF system has been successfully implemented for the iBNCT accelerator, with very good RF field regulation. An effective multipurpose and smart tuner controller was also developed. Finally, a novel auto-startup technology for two cavities with one RF source was successfully developed. The time required for the RF startup process is greatly reduced from the conventional time of 30 min, to less than 1 min. The good stability and fast response achieved by using this technology make it suitable for the medical use of iBNCT accelerators. This technology will be extremely useful in the development of similar accelerators.

Background This study aimed to investigate the trajectory of functional recovery of activities of daily living (ADL) from the time of admission up to hospital discharge, and explored which preoperative and postoperative variables were independently associated with functional decline in ADL at discharge of patients after cardiovascular surgery.Methods and Results:In this observational study, we evaluated ADL preoperatively and at discharge using the Functional Independence Measure (FIM) in patients after cardiovascular surgery. Functional decline in ADL was defined as scoring 1-5 on any one of the FIM items at discharge. Multiple logistic regression was performed to predict the functional decline in ADL at discharge. We found that 18.8% of elective cardiovascular surgery patients suffered from decreased ADL at discharge. The Mini-Mental State Examination (odds ratio (OR): 0.573, 95% confidence interval (CI): 0.420-0.783), gait speed (OR: 0.032, 95% CI: 0.003-0.304) and initiation of walking around the bed (OR: 1.277, 95% CI: 1.103-1.480) were independently associated with decreased ADL at discharge. Conclusions A functional decline in ADL at discharge can be predicted using preoperative measures of cognitive function, preoperative gait speed and postoperative day of initiation of walking. These results show that preoperative cognitive screening and gait speed assessments can be used to identify patients who might require careful postoperative planning, and for whom early postoperative rehabilitation is needed to prevent serious functional ADL deficits.

A disturbance observer (DOB)-based control approach was verified using the low-level radio-frequency systems of superconducting (SC) cavities operated in a continuous wave (CW) mode in a compact energy recovery linac (cERL) at KEK. This approach compensates for both predictable and unpredictable disturbances in a radio frequency (rf) system such as beam loading, Lorentz force detuning, and microphonics. This paper generalizes the DOB method in pulsed SC rf systems in the cERL at KEK. The results show that the pulse-to-pulse stabilities of the rf system are improved as expected by using this control approach. Furthermore, this method is validated by successfully compensating long pulse beam-loading effects in cERL.

Drug-coated balloon (DCB) angioplasty for femoropopliteal (FP) lesions has been available in Japan since 2018. In daily practice, we encountered cases of the slow-flow phenomenon after DCB angioplasty. However, no data regarding the slow-flow phenomenon after DCB angioplasty for FP lesions are available. This study aimed to investigate the frequency, predictors, and effect of the slow-flow phenomenon following DCB angioplasty for FP lesions. This single-center, retrospective, observational study analyzed 88 FP lesions treated by DCB angioplasty between April 2018 and July 2019. Patients were divided into the slow-flow group (n = 7) and non-slow-flow group (n = 81) and were analyzed. The primary endpoint was primary patency at 6 months. The slow-flow phenomenon was observed in seven cases (8.0%). The slow-flow group had higher incidence rates of critical limb ischemia (CLI) (71% vs. 25%, p

An EUV-FEL is one of the promising candidates for the future high power EUV light source of more than 1 kW. While the design study on the FEL light source has been progressed, a most important milestone should be a real demonstration of the high repetition rate ERL-based FEL light production. In FY2019, a real Mid-Infrared FEL (MIR-FEL) project based on the compact ERL in KEK started and the beam commissioning was started from the beginning of March 2020. At the conference, the present results obtained from the MIR-FEL and the expected remained-study-works on future EUV-FEL will be presented.

The aim of this study is to evaluate the clinical results of operative intervention for femoral metastases which were selected based on expected survival and to discuss appropriate surgical strategies.From 2002 to 2017, 148 consecutive patients undergoing surgery for femoral metastasis were included in this study. Prognostic risk assessments were performed according to the Katagiri and revised Katagiri scoring system. In general, the low-risk group underwent resection and reconstruction with endoprosthetic replacement (EPR), while the high-risk group underwent internal fixation (IF) and radiation therapy. For the intermediate-risk group, the operative choice depended on the patient's condition, degree of bone destruction, and radio-sensitivity. Overall survival, local failure, walking ability, and systemic complications were evaluated.A total of 83 patients underwent EPR (low-risk, 23%; intermediate-risk, 60%; high-risk, 17%) and 65 patients underwent IF (low-risk, 0%; intermediate-risk, 32%; high-risk, 68%). The one-year survival rate was 71% for EPR and 15% for IF (p0.001). The one-year local failure-free survival was 93% for EPR and 67% for IF, and the two-year and five-year local failure-free survival for EPR were both 88% (p = 0.016). Although the ambulatory rate was 99% for EPR and 60% for IF, the median time to ambulation was shorter in the IF (EPR, 28 days, interquartile range (IQR) 25 to 35; IF, 23 days, IQR 18 to 28; p0.001) The cause of non ambulation was mainly due to progression of cancer (89%). The rate of systemic complications was comparable between the two groups (EPR, 18%; IF, 22%; p = 0.598).Selective use of EPR where survival is expected to be good offers correspondingly good long-term results. IF is less invasive with shorter treatment period, which is beneficial for patients with short-term expected survival. Prognosis is an important indicator in selecting operative procedures for femoral metastasis. Cite this article

We demonstrate an experimental methodology for measuring the temporal distribution of pico-second level electron bunch with low energy using radial electric and azimuthal magnetic fields of an accelerating ($$\hbox {TM}_{01}$$ TM 01 mode) radio frequency (RF) cavity that is used for accelerating electron beams in a linear accelerator. In this new technique, an accelerating RF cavity provides a phase-dependent transverse kick to the electrons, resulting in the linear coupling of the trajectory angle with the longitudinal position inside the bunch. This method does not require additional devices on the beamline since it uses an existing accelerating cavity for the projection of the temporal distribution to the transverse direction. We present the theoretical basis of the proposed method and validate it experimentally in the compact-energy recovery linac accelerator at KEK. Measurements were demonstrated using a 2-cell superconducting booster cavity with a peak on-axis accelerating field ($$E_0$$ E 0 ) of 7.21 MV/m.

A high repetition rate EUV-FEL is one of the promising candidates for the future high power EUV light source more than 1 kW for future lithography. The design work on the FEL light source and the stepwise development procedure have been proposed elsewhere. Last fiscal year, KEK obtained a funding entitled "New laser technology development for processing laser" from NEDO to develop the high average power mid-infrared FEL. This FEL corresponds to the important stepwise development for EUV-FEL, too. At the conference, the present status of the project and the relationship of the technical development between present mid-infrared FEL and EUV-FEL will be presented.

Background: Certain patients with critical limb ischemia (CLI) experience significant decline in activities of daily living (ADL) during hospitalization. The prognosis of decline in ADL during hospitalization remains unknown. Methods: A retrospective analysis was performed on collected data of patients with CLI treated by endovascular treatment between April 2007 and December 2015. We evaluated CLI in patients ADL at the time of hospitalization and after discharge using the Barthel index. We classified all patients into patients with decline in ADL and stable in ADL and compared clinical outcomes (cumulative incidence of wound healing, amputation-free survival at 1 year) between the 2 groups. Results: Two hundred and fifty-five consecutive patients with CLI (221 limbs), who underwent successful endovascular intervention, were enrolled in this study. Of all patients, 22 patients were classified into the decline group. The prevalence of wound, Ischemia, foot infection (WIfI) classification high grade was higher in the decline group (30.7% vs 63.6%; P < .01). The wound healing rates were worse in the decline group than in the stable group (40% vs 78% at 1 year; P < .01). The same trends were observed in the amputation-free survival (37% vs 78%; P < .01). After multivariate analysis, decline in ADL was an independent predictor of wound healing and amputation-free survival (odds ratio [OR]: 2.85, 95% confidence interval [CI]: 1.61-3.35, P < .01; OR: 2.46, 95% CI: 1.26-4.53, P = .01). Conclusions: Patients with CLI with decline in ADL during hospitalization were found to have a poor prognosis suggesting that a decline in ADL may affect the clinical outcomes.

Energy-recovery linacs (ERLs) are promising for advanced synchrotron light sources, high-power free electron lasers (FELs), high-brightness gamma-ray sources , and electron–ion colliders. To demonstrate the critical technology of ERL-based light sources, we have designed and constructed a test accelerator, the compact ERL (cERL). Using advanced technology that includes a photocathode direct current (DC) electron gun and two types of 1.3-GHz-frequency superconducting cavities, the cERL was designed to be capable of recirculating low emittance ( ≤ 1 mm ⋅ mrad) and high average-current ( ≥ 10 mA) electron beams while recovering the beam energy. During initial commissioning, the cERL demonstrated successful recirculation of high-quality beams with normalized transverse emittance of ∼ 0.14 mm ⋅ mrad and momentum spread of ∼ 1.2 × 10−4 (rms) at a beam energy of 20 MeV and bunch charge below 100 fC. Energy recovery in the superconducting main linac was also demonstrated for high-average-current continuous-wave beams. These results constitute an important milestone toward realizing ERL-based light sources.

Introduction Radial artery occlusion after puncture is a serious complication of radial artery access for endovascular therapy (EVT). Herein, we show the feasibility of ultrasound-guided trans-occluded radial access (TORA) for EVT after radial artery occlusion. Case We describe the technique performed under ultrasound guidance for EVT for right external iliac artery stenosis in a 73-year-old man with intermittent claudication. Conclusion TORA provides a safe and feasible alternative access after radial artery occlusion.

The mid-infrared range is an important spectrum range where materials exhibit a characteristic response corresponding to their molecular structure. A free-electron laser (FEL) is a promising candidate for a high-power light source with wavelength tunability to investigate the nonlinear response of materials. Although the self-amplification spontaneous emission (SASE) scheme is not usually adopted in the mid-infrared wavelength range, it may have advantages such as layout simplicity, the possibility of producing a single pulse, and scalability to a short-wavelength facility. To demonstrate the operation of a mid-infrared SASE FEL system in an energy recovery linac (ERL) layout, we constructed an SASE FEL setup in cERL, a test facility of the superconducting linac with the ERL configuration. Despite the adverse circumstance of space charge effects due to the given boundary condition of the facility, we successfully established the beam condition at the undulators and observed FEL emission at a wavelength of 20 μm. The results show that the layout of cERL has the potential for serving as a mid-infrared light source.

This paper numerically and experimentally demonstrates the influence of the space charge forces in short electron bunches on the spectrum of coherent transition radiation. To estimate and optimize dimensions of a short electron bunches produced by the KEK LUCX RF gun, ASTRA software was employed. Obtained results indicate that the modification of the femtosecond UV laser pulse transverse profile allows to decrease the space charge forces. The simulation results were confirmed experimentally with the good agreement.

Operational experience of a 500 kV photoemission gun at the compact energy recovery linac (cERL) of the High Energy Accelerator Research Organization is presented. The gun, developed at the Japan Atomic Energy Agency, was found to have failures in two out of the ten-segment ceramic insulator just after installation at cERL. The gun had been operated at 390 kV with eight segments until April 2015 and provided a 0.9 mA beam. An additional two-segment insulator was installed on the top of the existing insulators to recover the high-voltage performance. The gun was then conditioned up to 539 kV and has been operated stably at 500 kV. No discharge caused by the gun itself was observed at 500 kV once the high threshold voltage for stable operation exceeded 500 kV. A dark current of a few picoamperes was generated at 500 kV from a photocathode puck with a semiconducting wafer, while no dark current was observed without a semiconducting wafer. Stable generation of a 500 keV beam with current greater than 0.8 mA was demonstrated for more than two hours.

Accelerator-based terahertz (THz) radiation has been expected to realize a high-power broadband source. Employing a low-emittance and short-bunch electron beam at a high repetition rate, a scheme of coherent diffraction-radiation in an optical cavity layout is proposed. The scheme's stimulated radiation process between bunches can greatly enhance the efficiency of the radiation emission. We performed an experiment with a superconducting linac constructed as an energy recovery linac (ERL) test facility. The electron beam passes through small holes in the cavity mirrors without being destroyed. A sharp THz resonance signal, which indicates broadband stimulated radiation correlated with beam deceleration, was observed while scanning the round-trip length of the cavity. This observation proves the efficient beam-to-radiation energy conversion due to the stimulated radiation process., Comment: 13 pages , 20 figures

Accelerator-based terahertz (THz) radiation has been expected to realize a high-power broad-band source. Employing a low-emittance and short-bunch electron beam at a high repetition rate, a scheme to resonantly excite optical cavity modes of THz spectrum range via coherent diffraction radiation has been proposed. The confocal cavity design is the special case that resonance conditions of all the eigen modes coincide, resulting in realizing broad-band excitation. But in general cases of non-confocal cavities, the resonance condition depends on the mode, and the resonance peak becomes wide and weak. We performed an experiment with a non-confocal cavity as a follow-up experiment of that we have done with a confocal cavity. The result confirmed that the confocal design is the key for a broad-band source., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

International audience; A new method of laser frequency stabilization using polarization property of an optical cavity is proposed. In a standard Fabry–Perot cavity, the coating layers thickness of cavity mirrors is calculated to obtain the same phase shift for sand p-wave but a slight detuning from the nominal thickness can produce sand p-wave phase detuning. As a result, each wave accumulates a different round-trip phase shift and resonates at a different frequency. Using this polarization property, an error signal is generated by a simple setup consisting of a quarter wave-plate rotated at 45°, a polarizing beam splitter and two photodiodes. This method exhibits similar error signal as the Pound–Drever–Hall technique but without need for any frequency modulation. Lock theory and experimental results are presented in this paper. &

A high-intensity pulsed muon beam is becoming available at the at the Japan Proton Accelerator Research Complex (J-PARC). Many experiments to study fundamental physics using this high-intensity muon beam are proposed. An experiment to measure the muon magnetic moment anomaly ($g-2$) and the muon electric dipole moment (EDM) is one of these experiments and it requires a tracking detector for positrons from muon decay. Fine segmentation is required in a detector to tolerate the high rate of positrons. The time resolution is required to be much better than the muon anomalous spin precession period while a buffer depth of a front-end electronics needs to be much longer than the accelerated muon lifetime. Requirements of this detector also meet requirements of a measurement of the muonium hyperfine structure interval at the J-PARC and another experiment to measure the proton charge radius at Tohoku University. We have developed a single-sided silicon strip sensor with a 190 $\mu$m pitch, a front-end electronics with a sampling rate of 200 MHz and a buffer memory depth of 8192, and a data acquisition system based on DAQ-Middleware for the J-PARC muon $g-2$/EDM experiment. We have fabricated detector modules consisting of this sensor and the front-end electronics. Performance of fabricated detector modules was evaluated at a laboratory and a beam test using the positron beam at Tohoku University. The detector is confirmed to satisfy all requirements of the experiments except for the time walk, which will be solved by the next version of a front-end electronics., Comment: 18 pages, 17 figures

Coronary obstruction is a rare (

We aimed to compare the angiographic outcomes between repeat drug-eluting stent (DES) implantation and drug-coated balloon (DCB) treatment for restenotic lesion caused by stent fracture (SF). The treatment of restenotic lesion caused by SF after DES implantation has not been well evaluated. From April 2007 to April 2015, 9320 lesions were implanted with a DES during percutaneous coronary intervention in our hospital; of those, 815 lesions (8.7%) showed restenosis on the follow-up angiogram. The study subjects were 47 consecutive patients with 69 restenotic lesions caused by SF and treated by target lesion revascularization (TLR); of those, 27 patients with 45 lesions were treated with repeat DES during TLR (either a cobalt–chromium or platinum–chromium everolimus-eluting stent or zotarolimus-eluting stent; DES group), and 20 patients with 24 lesions were treated with DCB (DCB group) during TLR. The 12-month cumulative incidence of repeat TLR and predictors of repeat TLR was evaluated. Restenosis and re-restenosis were defined as % diameter stenosis > 50% on the follow-up angiogram. SF was defined as complete or partial separation of the stent strut as assessed by plain fluoroscopy. Baseline characteristics were similar between the groups. The 12-month binary re-restenosis rate and cumulative incidence of repeat TLR between the DES group and DCB group were 44.4% and 37.5% (p = 0.58) and 43.9% and 31.9% (p = 0.31), respectively. On multivariate analysis, a lesion with vessel hinge movement was an independent predictor of repeat TLR (p = 0.02, hazard ratio: 6.54, 95% confidence interval 1.30–32.8). The 12-month repeat TLR rate was high in both groups. After treating restenosis lesions caused by SF after DES implantation, mechanical stress leads to further interventional treatment, regardless of the type of device used.

With a low emittance and short-bunch electron beam at a high repetition rate realized by a superconducting linac, stimulated excitation of an optical cavity at the terahertz spectrum range has been shown. The electron beam passed through small holes in the cavity mirrors without being destroyed. A sharp resonance structure which indicated wide-band stimulated emission via coherent diffraction radiation was observed while scanning the round-trip length of the cavity.

Nowadays, the generation of narrow-bandwidth, high brightness, and tunable X-rays via laser-Compton scattering (LCS) is expected for many scientific and industrial applications. In this paper, we will show that the energy recovery linac (ERL)-based LCS X-ray source can be applied to an X-ray imaging of biological specimens.

Quasi-monochromatic X-rays with high brightness have a broad range of applications in fields such as life sciences, bio-, medical applications, and microlithography. One method for generating such X-rays is via inverse Compton scattering (ICS). X-ray generation experiments using ICS were carried out at the superconducting RF test facility (STF) accelerator at KEK. A new beam line, newly developed four-mirror optical cavity system, and new X-ray detector system were prepared for experiments downstream section of the STF electron accelerator. Amplified pulsed photons were accumulated into a four-mirror optical cavity and collided with an incoming 40 MeV electron beam. The generated X-rays were detected using a microchannel plate (MCP) detector for X-ray yield measurements and a new silicon-on-insulator (SOI) detector system for energy measurements. The detected X-ray yield by the MCP detector was 1756.8±272.2 photons/(244 electron bunches). To extrapolate this result to 1 ms train length under 5 Hz operations, 4.60×10 5 photons/1%-bandwidth were obtained. The peak X-ray energy, which was confirmed by the SOI detector, was 29 keV, and this is consistent with ICS X-rays.

We have been developing optical resonant cavities for laser-Compton scattering experiment at the Accelerator Test Facility in KEK. The main subject of the R&D is to increase laser pulse energy by coherently accumulating the pulses in an optical resonant cavity. We report previous results, current status and future prospects, including a new idea of an optical resonant cavity., 8 pages, 5 figures. Proceedings of the 7th International Conference "Charged & Neutral Particles Channeling Phenomena Channeling 2016"

Realization of a short bunch beam by manipulating the longitudinal phase space distribution with a finite longitudinal dispersion following an off-crest acceleration is a widely used technique. The technique was applied in a compact test accelerator of an energy-recovery linac scheme for compressing the bunch length at the return loop. A diagnostic system utilizing coherent transition radiation was developed for the beam tuning and for estimating the bunch length. By scanning the beam parameters, we experimentally found the best condition for the bunch compression. The RMS bunch length of 250 ± 50 fs was obtained at a bunch charge of 2 pC. This result confirmed the design and the tuning procedure of the bunch compression operation for the future energy-recovery linac (ERL).

Investigation of coherent Smith-Purcell Radiation (SPR) spectral characteristics was performed both experimentally and by numerical simulation. The measurement of SPR spectral line shapes of different diffraction orders was carried out at KEK LUCX facility. A pair of room-temperature Schottky barrier diode (SBD) detectors with sensitivity bands of $60-90$~GHz and $320-460$~GHz was used in the measurements. Reasonable agreement of experimental results and simulations performed with CST Studio Suite justifies the use of different narrow-band SBD detectors to investigate different SPR diffraction orders. It was shown that monochromaticity of the SPR spectral lines increases with diffraction order. The comparison of coherent transition radiation and coherent SPR intensities in sub-THz frequency range showed that the brightnesses of both radiation mechanisms were comparable. A fine tuning feasibility of the SPR spectral lines is discussed., Comment: 7 pages, 7 figures, 3 tables

A beam position monitor (BPM) with the nanometer-scale position resolution and the decay time of approximately 20 ns is developed as an interaction point BPM, to verify the nanometer stabilization of the International Linear Collider beam trains at the Accelerator Test Facility (ATF), High Energy Accelerator Research Organization (KEK). The developed low- $Q$ cavity BPM consists of a one-cell sensor cavity and a one-cell reference cavity. An electronic system is developed, based on the beam test results, to process the signals from the BPM. The beam position resolution of the low- $Q$ cavity BPM with the electronics system is measured at the ATF2 beam line of KEK, and the results of the beam tests conducted on the developed low- $Q$ cavity-type BPM are described.