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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 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.

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.

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.

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.

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.

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

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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.

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.

Narrow-bandwidth photon beams in the x-ray and γ-ray energy ranges are expected to be applied in various fields. An energy recovery linac (ERL)-based laser Compton scattering (LCS) source employing a laser enhancement cavity can produce a high-flux and narrow-bandwidth photon beam. We conducted the first experiment of an ERL-based LCS source in combination with a laser enhancement cavity. We obtained LCS photons with an energy of 6.95±0.01 keV by colliding an electron beam of 20 MeV with a laser of 1064 nm wavelength. The photon flux at the interaction point was evaluated to be (2.6±0.1)×10^{7} photons/s with an average beam current of 58 μA and an average laser power of 10 kW. The energy bandwidth was evaluated to be 0.4% (rms) with an opening angle of 0.14 mrad. The technologies demonstrated in this experiment are applicable for future ERL-based LCS sources.

Background: The semiquantitative Clinical Frailty Scale (CFS) is a simple tool to assess patients’ frailty and has been shown to correlate with mortality in elderly patients even when evaluated by nongeriatricians. The aim of the current study was to determine the prognostic value of CFS in patients who underwent transcatheter aortic valve replacement. Methods: We utilized the OCEAN (Optimized Catheter Valvular Intervention) Japanese multicenter registry to review data of 1215 patients who underwent transcatheter aortic valve replacement. Patients were categorized into 5 groups based on the CFS stages: CFS 1-3, CFS 4, CFS 5, CFS 6, and CFS ≥7. We subsequently evaluated the relationship between CFS grading and other indicators of frailty, including body mass index, serum albumin, gait speed, and mean hand grip. We also assessed differences in baseline characteristics, procedural outcomes, and early and midterm mortality among the 5 groups. Results: Patient distribution into the 5 CFS groups was as follows: 38.0% (CFS 1-3), 32.9% (CFS4), 15.1% (CFS 5), 10.0% (CFS 6), and 4.0% (CFS ≥7). The CFS grade showed significant correlation with body mass index (Spearman’s ρ=−0.077, P =0.007), albumin (ρ=−0.22, P P P P P Conclusions: In addition to reflecting the degree of frailty, the CFS was a useful marker for predicting late mortality in an elderly transcatheter aortic valve replacement cohort.

We report and discuss high-flux generation of circularly polarized γ-rays by means of Compton scattering. The γ-ray beam results from the collision of an external-cavity-enhanced infrared laser beam and a low emittance relativistic electron beam. By operating a non-planar bow-tie high-finesse optical Fabry-Perot cavity coupled to a storage ring, we have recorded a flux of up to (3.5 ± 0.3) × 108 photons per second with a mean measured energy of 24 MeV. The γ-ray flux has been sustained for several hours. In particular, we were able to measure a record value of up to 400 γ-rays per collision in a full bandwidth. Moreover, the impact of Compton scattering on the electron beam dynamics could be observed resulting in a reduction of the electron beam lifetime correlated to the laser power stored in the Fabry-Perot cavity. We demonstrate that the electron beam lifetime provides an independent and consistent determination of the γ-ray flux. Furthermore, a reduction of the γ-ray flux due to intrabeam scattering has clearly been identified. These results, obtained on an accelerator test facility, warrant potential scaling and revealed both expected and yet unobserved effects. They set the baseline for further scaling of the future Compton sources under development around the world.

This paper describes new scheme for obtaining a differential signal to lock an optical cavity at a resonance peak. This scheme utilizes a unique property of non-planar cavities; due to an additional phase factor originated from the geometric configuration of the optical path, the two circular polarizations produce two resonance peaks. An ideal signal that crosses zero at the resonance peaks can be obtained using a simple setup consisting of a polarizing beam splitter and photo-diodes. The principle and the results of an experiment are also presented.

Background Solitary bone only metastasis (SBOM) is a rare condition in which metastasis is limited to a single skeletal lesion originating from a previously treated or controllable primary lesion. The study objective was to evaluate the clinical features and survival regarding this rare condition and to clarify its treatment strategy. Methods A total of 1453 patients with bone metastasis registered in our hospital database were enrolled. To assess the primary and/or metastatic lesion we used plain X-ray images, CT, MRI and FDG-PET scans as well as bone scans. Results Among the patients, only 27 (1.8%) had SBOM. The primary cancers responsible for SBOM were lung in seven patients, breast in five, kidney in four, prostate in two, uterus in two and other types in seven. Treatment of SBOM involved resection in four patients, radiotherapy only in 17, radiotherapy in combination with zoledronate in six and chemotherapy with zoledronate in one. Local recurrence did not develop in the four cases treated with resection. However, in-field recurrence was found in 4 of 22 (18%) patients who underwent radiotherapy. All three patients who received >40 Gy did not develop in-field recurrence. The overall and event free survival rates at 5 years were 63% and 41%, respectively. Conclusions Solitary bone only metastasis should be treated with wide resection or long-course radiotherapy at doses 40–50 Gy to achieve long lasting local tumor control.

Success in design and construction of a compact, high-brightness accelerator system is strongly related to the production of ultra-short electron beams. Recently, the approach to generate short electron bunches or pre-bunched beams in RF guns directly illuminating a high quantum efficiency semiconductor photocathode with femtosecond laser pulses has become attractive. The measurements of the photocathode response time in this case are essential. With an approach of the interferometer-type pulse splitter deep integration into a commercial Ti:Sa laser system used for RF guns, it has become possible to generate pre-bunched electron beams and obtain continuously variable electron bunch separation. In combination with a well-known zero-phasing technique, it allows us to estimate the response time of the most commonly used Cs2Te photocathode. It was demonstrated that the peak-to-peak rms time response of Cs2Te is of the order of 370 fs, and thereby, it is possible to generate and control a THz sequence of relativistic electron bunches by a conventional S-band RF gun. This result can also be applied for investigation of other cathode materials and electron beam temporal shaping and further opens a possibility to construct wide-range tunable, table-top THz free electron laser.

Adlayers of ZnOEP were prepared on reconstructed Au(100)-(hex) and unreconstructed Au(100)-(1 x 1) surfaces by immersing into a benzene solution containing ZnOEP molecules, and the adlayer structures were characterized byscanning tunneling microscopy (STM). A hexagonally arranged ZnOEP array was formed on an Au(100)-(hex) surface, whereas a rectangularly arranged ZnOEP array was found on an Au(100)-(1 x 1) surface. The adlayer structure of ZnOEP was dependent upon the underlying Au atomic arrangements. Furthermore, an investigation of the spuramolecular assembly for these modified surfaces was carried out by using an open-cage C 6 0 derivative (opened C 6 0 ). A supramolecular assembled adlayer with a 1:1 composition of opened C 6 0 /ZnOEP was formed on Au(100)-(hex), whereas aggregates of opened C 6 0 were found on the ZnOEP-modified Au(100)-(1 x 1) surface. Electrochemical responses of opened C 6 0 were significantly influenced by underlying ZnOEP arrays. This finding suggests that precise control of underlying ZnOEP adlayers with the Au atomic structure is important to recognize the opened C 6 0 on them.

Model-independent analysis (MIA) methods are generally useful for analysing complex systems in which relationships between the observables are non-trivial and noise is present. Principal Component Analysis (PCA) is one of MIA methods allowing to isolate components in the input data graded to their contribution to the variability of the data. In this publication we show how the PCA can be applied to digitised signals obtained from a cavity beam position monitor (CBPM) system on the example of a 3-cavity test system installed at the Accelerator Test Facility 2 (ATF2) at KEK in Japan. We demonstrate that the PCA based method can be used to extract beam position information, and matches conventional techniques in terms of performance, while requiring considerably less settings and data for calibration.

We demonstrated the operation of a high finesse optical cavity without utilizing an active feedback system to stabilize the resonance. The effective finesse, which is a finesse including the overall system performance, of the cavity was measured to be $394,000 \pm 10,000$, and the laser power stored in the cavity was $2.52 \pm 0.13$ kW, which is approximately 187,000 times greater than the incident power to the cavity. The stored power was stabilized with a fluctuation of $1.7 \%$, and we confirmed continuous cavity operation for more than two hours. This result has the potential to trigger an innovative evolution for applications that use optical resonant cavities such as compact photon sources with laser-Compton scattering or cavity enhanced absorption spectroscopy., Comment: 5 pages, 7 figures

As part of the positron source R&D for future $e^+-e^-$ colliders and Compton based compact light sources, a high finesse non-planar four-mirror Fabry-Perot cavity has recently been installed at the ATF (KEK, Tsukuba, Japan). The first measurements of the gamma ray flux produced with a such cavity using a pulsed laser is presented here. We demonstrate the production of a flux of 2.7 $\pm$ 0.2 gamma rays per bunch crossing ($\sim3\times10^6$ gammas per second) during the commissioning.

Arthroscopic partial menisectomy followed by cyst decompression is currently recommended for treatment of a meniscal cyst. However, it is doubtful whether partial menisectomy should be performed on cysts communicating with the joint in cases without a meniscal tear on its surface since meniscal function will be sacrificed. In this report, a meniscal cyst arising from the posterior horn of the medial meniscus without meniscal tear on its surface was resected using an arthroscopic posterior trans-septal approach. A 59 year-old male presented to our hospital with popliteal pain when standing up after squatting down. Magnetic resonance imaging revealed a multilobulated meniscal cyst arising from the posterior horn of the medial meniscus extending to the posterior septum with a grade 2 meniscal tear by Mink's classification. The medial meniscus was intact on the surface on arthroscopic examination. The meniscal cyst and posterior septum were successfully resected using a posterior trans-septal approach without harming the meniscus. This is the first report on a meniscal cyst being resected using an arthroscopic posterior trans-septal approach with a 9-month follow-up period.

We performed a photon generation experiment by laser-Compton scattering at the KEK-ATF, aiming to develop a Compton based polarized positron source for linear colliders. In the experiment, laser pulses with a 357 MHz repetition rate were accumulated and their power was enhanced by up to 250 times in the Fabry-Perot optical resonant cavity. We succeeded in synchronizing the laser pulses and colliding them with the 1.3 GeV electron beam in the ATF ring while maintaining the laser pulse accumulation in the cavity. As a result, we observed 26.0 +/- 0.1 photons per electron-laser pulse crossing, which corresponds to a yield of 10^8 photons in a second., Comment: 3 pages, 5 figures, Preprint submitted to TIPP09 Proceedings in NIMA

An optical sensor system composed of a single photodetector and a laser scanning system with on algorithm to calculate the posture are proposed. The principle of this sensor is to observe the distortion of the circular trajectory of laser on the measured plane, and it is possible to obtain the information on the spatial posture based on the fundamental coordinate of the sensor. This information is calculated by using a new integrating method of the trajectory signals, and it matches well with the manipulating signal of a robot with the function of a path control. Basic experiments to verify this sensor were conducted and the validity of this sensor and algorithm was confirmed.

3 pp. (2007)., International Linear Collider (ILC) interaction region beam sizes and component position stability requirements will be as small as a few nanometers. It is important to the ILC design effort to demonstrate that these tolerances can be achieved - ideally using beam-based stability measurements. It has been estimated that RF cavity beam position monitors (BPMs) could provide position measurement resolutions of less than one nanometer and could form the basis of the desired beam-based stability measurement. We have developed a high resolution RF cavity BPM system. A triplet of these BPMs has been installed in the extraction line of the KEK Accelerator Test Facility (ATF) for testing with its ultra-low emittance beam. A metrology system for the three BPMs was recently installed. This system employed optical encoders to measure each BPM's position and orientation relative to a zero-coefficient of thermal expansion carbon fiber frame and has demonstrated that the three BPMs behave as a rigid-body to less than 5 nm. To date, we have demonstrated a BPM resolution of less than 20 nm over a dynamic range of +/- 20 microns.

Author(s): Wolski, Andrzej; Ross, Marc C.; Woodley, Mark D.; Nelson, Janice; Honda, Yosuke | Abstract: Orbit Response Matrix (ORM) analysis is a technique used to diagnose and correct optics errors in storage rings. We report the results obtained from the use of ORM analysis at the KEK-ATF to reduce the equilibrium vertical emittance. Measurements of the vertical beam size using a laser wire indicate that the vertical emittance was successfully reduced from 12 pm to around 6 pm (at a bunch charge of 7e9 particles) using ORM analysis.

We present the measurement results of electron beam emittance in the Accelerator Test Facility damping ring operated in multibunch modes. The measurements were carried out with an upgraded laser wire beam profile monitor. The monitor has now a vertical wire as well as a horizontal one and is able to make much faster measurements thanks to an increased effective laser power inside the cavity. The measured emittance shows no large bunch-to-bunch dependence in either the horizontal or vertical directions. The values of the vertical emittance are similar to those obtained in the single-bunch operation. The present results are an important step toward the realization of a high-energy linear collider.

In 2011, two SR sources of KEK, PF-ring and PF-AR, needed to change the operation schedule because of the unprecedented earthquake on March 11. Though the injector linac and the storage rings suffered a serious damage, temporary recovery was accomplished quickly and the trial operation started in May. The regular user operation could be resumed in October 2011. In the restoration work after the earthquake, some old vacuum components were removed from PF-ring. This work fortunately brought an effect of settling the quadrupole-mode longitudinal instability. For the top-up injection of PF-ring, the pulsed sextupole magnet has been used instead of the conventional kicker magnets since 2011. The hybrid-fill mode in place of the single-bunch mode has become available. Recently, the 10-Hz orbit switching for the tandem circularly polarized undulators has been developed for the user operation.

We have developed a 500-kV, 10-mA photocathode DC gun for energy recovery linac (ERL) light sources. A segmented ceramic insulator with guard rings is employed to improve robustness at high voltage operation, because this structure can prevent field emission electrons from directly striking the ceramic surface. We have recently succeeded in applying 500 kV on the ceramics for eight hours without any discharge. This high voltage testing was performed with a simple configuration without NEG pumps, cathode and anode electrodes to mainly study the field emission from a tube supporting the cathode electrode. The same high voltage testing with a full configuration necessary for beam generation was carried out up to 380 kV where some increase of radiation was observed. Up-to-date status of our gun development is presented in detail.