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The iBNCT project aims to develop “iBNCT001,” a demonstration device of the linac-based neutron irradiation facility for boron neutron capture therapy (BNCT) application. iBNCT001 generates an epithermal neutron beam by irradiating 8 MeV protons accelerated by a linac onto a beryllium target. Currently, the linac can drive an average proton current of 2.1 mA. Several experiments were performed using a water phantom to confirm the main physical characteristics of the neutron beam produced at the irradiation position. The measurement results demonstrated that the maximum thermal neutron flux achievable in the phantom volume was approximately 1.36 × 10 9 cm − 2 s − 1 when a normal beam collimator with a 120 mm diameter was used. This neutron beam intensity was sufficient to complete the irradiation within 30 min using the BNCT approach. In addition to normal beam collimators, extended collimators that protrude 100 mm from the wall were developed. By using an extended collimator, it is possible to prevent interference of the patient’s body with the wall when irradiating head and neck cancers. The measurement results for the extended collimator demonstrated that irradiation with the collimator could be completed within 1 h when the neutron beam is generated with an average proton current of 2.1 mA.

To resolve the drawback of conventional thyratron switches, development of a semiconductor high voltage switch utilizing a 13 kV class SiC-MOSFET developed by Tsukuba Power Electronics Constellations (TPEC) is proceeding. At first, the device evaluation test was carried out with a resistive load circuit. With the conditions of drain voltage of 10 kV and load resistance of 1 kΩ, turn on loss Eon, turn off loss Eoff, rise time Tr and fall time Tf were 1.7 mJ, 1.1 mJ, 64 ns, and 75 ns, respectively. Thereafter, the 2s-12p switch array was designed and assembled, where 12 MOSFETs are equally aligned on a circle shaped circuit board and two circuit boards are stacked in series. An 18 kV-318 A-1 us pulse with a rise time of 289 ns in the short pulse switching test were successfully demonstrated. Moreover, switching tests of 2nd generation MOSFET that has a twice larger device area was conducted. As a result, 60 % reduction of on-resistance was confirmed.

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.

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.

The J-PARC Main Ring (MR) has supplied the high-intensity proton beam for the T2K long-baseline neutrino experiment since 2010. The present beam power is 510 kW and the total number of protons on the target reaches $3.64\times10^{21}$. To observe charge-conjugation and parity-transformation (CP) violation in the lepton sector with high accuracy, more protons need to be delivered to the T2K target. The project to upgrade the beam power to 1.3 MW started as a mid-term plan of the MR. In parallel to preparing a full technical design report, the technical designs of hardware upgrades using new technologies and all accelerator components that are necessary to deliver the 1.3-MW beam power are summarized and consolidated in this short paper. Further, this paper includes beam dynamics studies and simulation results for handling $3.3\times 10^{14}$ protons per pulse (ppp) without significant beam loss in the ring and transport lines. The Hyper-Kamiokande (HK) project has recently been approved, and construction has started; the MR upgrade and HK project will work together efficiently to study the CP violation.

The linac-based neutron source “iBNCT” developed by the Tsukuba team has been shown to generate a large intensity of neutrons. To confirm the applicability of the device to BNCT, several characteristic measurements have been implemented. In a water phantom experiment, when the accelerator was operated with an average current of 1.4 mA, the maximum thermal neutron flux was approximately 7.8 × 108 (cm-2s-1). From estimation of the stability of the linac, the results demonstrate its applicability to actual treatment.

Japan Proton Accelerator Research Complex (J-PARC) has started the beam delivery at 2009 to the experimental facilities which are the neutrino experimental facility (T2K), the hadron experimental facility and the material and life science facility (MLF). However J-PARC had two big troubles during last three years: First one was induced by the Great East Japan Earthquake happened in March 2011 and the second one was caused by the radioactive material leakage from hadron experimental facility in May 2013. The damage to the accelerators from both troubles has been fixed by the effort of members. As a result J-PARC has resumed the beam delivery to users. The achieved beam power for T2K is 240 kW which is one third of design value of 750 kW. In this report, the status of the accelerator operation of J-PARC is described. Furthermore it is also described the measurement of the extinction level for the physics experiment.

The linac-base neutron source “iBNCT” developed by the Tsukuba team has begun to generate a large intensity of neutrons. To confirm the applicability of the device to BNCT, several characteristic measurements have been implemented. In a water phantom experiment, when the accelerator was operated with an average current of 1.4 mA, the maximum thermal neutron flux was approximately 7.8 × 108 (n/cm2/s). Results demonstrate the stability of the linac over time, showing its promising potential for future patient treatment.

Boron neutron capture therapy (BNCT) is emerging as the next-generation radiation therapy, thanks to the recent technological advancements in the accelerator-based neutron source. In the iBNCT project headed by the University of Tsukuba, a linac-based BNCT device is being developed. The demonstrator of the iBNCT device commenced its operations in 2016. This paper reports the various experiments and measurements performed on the iBNCT device to confirm the physical characteristics of the neutron beam emitted from the beam aperture of the device. We evaluated the neutron energy spectrum at the beam aperture experimentally using the Bonner sphere detector method. The results demonstrated that the device emits the epithermal neutron beam corresponding with the energy spectrum assumed in the design phase. Furthermore, we performed experiments using a water phantom that simulates a human body whereby we measured the profiles of both thermal neutron flux and gamma-ray dose rate on the beam axis in the phantom. The results demonstrated that the iBNCT neutron beam has sufficient intensity applicable to clinical studies of the BNCT. In order to apply the iBNCT device to real-time therapy, we perform the device development on a continuous basis to further improve the stability performance as well as to increase proton current.

In the Japan Proton Accelerator Research Complex (J-PARC) linac, negative hydrogen beams are accelerated from 190 MeV to 400 MeV by twenty-one Annular-ring Coupled Structure (ACS) accelerating cavities. The input coupler of the ACS high-beta cavity, which is the 21st accelerating cavity (ACS21) in the order of beam acceleration, had a comparatively larger value of the Voltage Standing Wave Ratio (VSWR) than those of the other ACS cavities. To adjust the VSWR of the ACS21, we designed and fabricated a rectangular waveguide with a capacitive iris which conduces to a better matching between the cavity and the waveguide. In the 2018 summer maintenance period, we installed the newly fabricated waveguide to the ACS21 in the position between the input coupler and the RF window. Consequently, the VSWR of the ACS21 was successfully decreased to the target value which leads to the critical coupling under the nominal accelerating condition with 50-mA peak beam current., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

A disk and washer (DAW) coupled cavity linac (CCL) has been developed for a middle velocity part in a muon linac at the J-PARC E34 experiment. It will accelerate muons from v/c = 0.3 to 0.7 at an operational frequency of 1296 MHz. In this poster, the cavity designs, beam dynamics designs, and the cold-model measurements will be presented., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

In boron neutron capture therapy, it is important to evaluate the dose administered to a patient's body outside the tumour area. The exposure dose is evaluated by calculation; however, the calculated value must be validated using a measured value. The dose evaluations based on the measured neutron spectrum are investigated. Multi-foil activation, combined with a LiCaAlF6 scintillation detector and an imaging plate, is proposed as a measurement method. The proposed method can measure the neutron spectrum at various points quickly.

Impedance matching of RF windows that minimizes the RF reflection is necessary to prevent localized standing waves between an RF window and a cavity, which may cause thermal and/or multipactoring issues. It has been observed that the impedance matching condition of the pillbox-type RF window, checked by voltage standing wave ratio (VSWR) measurement, depends on the manufacturing lot of the window ceramic disk made of 95% purity Al2O3. The present report proposes new procedures for impedance matching as follows: (i) The relative dielectric constant of the ceramic window is directly measured using the resonant frequency of a cavity made by temporarily combining the pillbox part of the RF window and two short-circuiting plates. (ii) The dimensions of the pillbox section including the ceramic disk are fixed on the basis of the measured relative dielectric constant. To confirm this procedure, three RF windows were fabricated using the same type of ceramic material, and successful impedance matching of these windows was performed ( VSWR 1.05 ). The measured results also suggest that the relative dielectric constant increases linearly with increasing density and that the impedance matching condition is mainly affected by variations of the relative dielectric constant due to shrinkage of the alumina during sintering.

All systems comprising the Japan Proton Accelerator Research Complex (J-PARC), namely, the 400 MeV linac, 3-GeV rapid-cycling synchrotron, and 50-GeV synchrotron, were completed in 2009 and are now being used to supply high-power proton beams to secondary particle users. In order to minimize maintenance and shorten the pump-down and conditioning period, an ultra-high vacuum of 10 −5 Pa or lower is required for the vacuum system. Here we present a review of the surface processing methods employed and the results of outgassing measurements for the components used in the vacuum system made from the following materials: electroformed copper, alumina ceramic, titanium, and stainless steel. The vacuum performance of these materials during accelerator operation is also reported.

Boron neutron capture therapy (BNCT) is one of the hopeful cancer therapies. Until recently, BNCT used the Nuclear fission reactor as a neutron source. However, many usable reactors for BNCT have been terminated and it is hard recently to build the new research reactor in many countries. Thus, a small accelerator which can supply the intense proton beam become a candidate of a neutron source instead of the reactor. Furthermore, it is impossible to install the reactor in a hospital but we can install the accelerator system in the hospital. In this article we describe the basic physics of the linear accelerator and cyclotron for BNCT. An ion source and the target for neutron production are also described briefly.

Toward to the next generation experimental investigation of neutrino physics, the J-PARC accelerator group is now considering several candidates to extend the proton beam power to multi-MW region. One of the major candidates is the adoption of a superconducting proton linac. A neutrino is generated by bombarding a proton beam to a target. In Monte-Carlo simulations with GCALOR or FLUKA2011 package, the generated neutrino flux per proton beam energy monotonously increases with the energy reaching to around 9 GeV, and then saturation is seen in higher energy [1]. Therefore, if we only focus on the efficiency of neutrino generation, it is efficient to improve the average beam current with staying the beam energy to 9 GeV. It motivated us to consider the 9 GeV proton linac for neutrino beam generation. For the study on the design, we assume that the linac is constructed in the KEKB tunnel. As shown in Fig.1, the tunnel is fourfold symmetric structure and its circumference is 3 km. The accelerator cavities are placed only in the straight sections. In the each straight section, beam energy reaches 1.2, 3.8, 6.4 and 9 GeV, respectively. From 1.2 GeV to 9 GeV, ILC type superconducting cavities with two kinds of geometrical beta (βg) are placed. The 2 straight is βg = 0.93, and the 3 to 4 straights are βg = 1.0. In this presentation, we introduce the present accelerator design under the term of construction in the KEKB tunnel.

Muon acceleration will be accomplished by a set of induction cells, where each increases the energy of the muon beam by an increment of up to 30 kilovolts. The cells are arranged in a linear way resulting in total accelerating voltage of 300 kilovolts. Acceleration time in the linac is about hundred nanoseconds. Induction field calculation is based on an electrostatic approximation. Beam dynamics in the induction accelerator is investigated and final beam focusing on specimen is realized by designing a pole piece lens.

Kazuo HASEGAWA*, Hidetomo OGURI, Takashi ITO, Etsuji CHISHIRO, Koichiro HIRANO, Takatoshi MORISHITA, Shinichi SHINOZAKI, Hiroyuki AO, Kiyonori OHKOSHI, Yasuhiro KONDO, Jun TAMURA, Saishun YAMAZAKI, Toshihiko HORI, Fumiaki SATO, Yasuo NEMOTO, Isao KOIZUMI, Nobuo OUCHI, Nobuhiro KIKUZAWA, Akira UENO, Akihiko MIURA, Shinpei FUKUTA, Akinobu YOSHII, Koichi SATO, Akira OZONE, Yuki SAWABE, Yusuke KAWANE, Hiroshi IKEDA, Yuichi ITO, Yuko KATO, Kazuo KIKUCHI, Fumio HIROKI, Toshio TAKAYASU, Tsutomu USAMI, Munetoshi YANAI, Kazuhiko TADOKORO, Kenji OHSAWA, Fujio NAITO, Yong LIU, Zhigao FANG, Takashi SUGIMURA, Kenta FUTATSUKAWA, Kiyoshi IKEGAMI, Masato KAWAMURA, Kesao NANMO, Yuji FUKUI, Tomoaki MIYAO, Tomofumi MARUTA and Akira TAKAGI

Clinical trials of the boron neutron capture therapy (BNCT) have been conducted using research reactors. Recent progresses in the accelerator and accelerator-driven-neutron-source technologies have rendered it possible to generate the substantial number of neutrons required for BNCT treatment, using a compact accelerator, which can be installed in a hospital. The University of Tsukuba launched a project for the development of a compact accelerator-based neutron source for BNCT. For this accelerator, we employed a linear particle accelerator (linac) and the energy of the proton beam was 8 MeV. Beryllium was selected as the neutron target material. To generate sufficient neutron intensity by the reaction between 8 MeV protons and beryllium, the linac accelerates a high current of 5 mA or more. As the target system is critical, we developed a beryllium target system with a threelayered structure to avoid target breakage, caused by massive heat load and blistering, within a short period. The linac-based neutron source for the BNCT is almost complete and we succeeded in generating neutrons, in 2015. Currently, several characteristic measurements are being carried out.

The slow cycling main ring synchrotron (MR) is located the furthest downstream in the J-PARC accelerator cascade. It became available for user operation in 2009 and provides high-intensity 30 GeV proton beams for various experiments on particle and nuclear physics. The MR has two beam extraction systems: a fast extraction system for beam delivery to the neutrino beam line of the Tokai-to-Kamioka (T2K) experiment and a slow extraction system for beam delivery to the hadron experimental hall. After a nine-month beam shutdown during the recovery from the Great East Japan Earthquake, the J-PARC facility resumed beam operation in December 2011. The MR delivers a 160–200kW beam to the T2K experiment and a 3.5–6kW beam to users in the hadron experimental hall. In this paper, a brief review of the MR and the recent status of beam operation are presented. Near-future plans for a beam intensity upgrade are also discussed.

A device for the deposition of a radioactive Langmuir-Blodgett (LB) film was developed with the use of: (1) a modified horizontal lifting method, (2) an extremely shallow trough, and (3) a surface pressure-generating system without piston oil. It made a precious radioactive subphase solution repeatedly usable while keeping its radioactivity concentration as high as possible. Any large-size thin films can be prepared by just changing the trough size. Two monomolecular-layers of Y-type films of cadmium [ 3 H] icosanoate and 109 Cd icosanoate were built up as 3 H and 109 Cd β-sources for electron spectroscopy with intensities of 1.5 GBq (40 mCi) and 7.4 MBq (200 μCi), respectively, and a size of 65×200 mm 2 . Excellent uniformity of the distribution of deposited radioactivity was confirmed by autoradiography and photometry.

The required alignment accuracy in the J-PARC linac is 0.1 mm in transverse direction. In the DTL/SDTL section, the fine alignment was carried out by using an optical alignment telescope along with the cavity installation. The displacement of the DTL by the unit tank connection was monitored by a laser tracker to obtain the tolerable displacement between unit tanks. The heights of cavities and magnets were compensated form the local settlement of the linac tunnel.

J-PARC linear accelerator components are now being installed in the accelerator tunnel, whose total length is more than 400 m including the beam transport line to 3GeV synchrotron. A precise alignment of accelerator components is essential for high quality beam acceleration. In this paper, planned alignment schemes for the installation of linac components and watching the long term motion of the building are described. Markings are placed on the floor, which act as a reference for the initial alignment at the installation. For a straight line alignment, the wire position sensor is placed on the offset position with respect to the beam center by a target holder. The hydrostatic levering system is used for watching the floor elevation over the long period.

Tuning of the accelerating field of the DTL first tank for the Japan Proton Accelerator Research Complex (J-PARC) has been done. The first DTL tank consists of 75 full drift tubes, 37 post-couplers and 10 fixed tuners. The resonant frequency of the tank is 324 MHz. An uniform accelerating field has been achieved by the fine adjustment of the post-couplers and the fixed tuners. The field stabilization by the post-couplers against perturbations has been confirmed also. In order to achieve the stabilized-uniform distribution of the average field for each accelerating gap, the following techniques have been applied for the post-coupler tuning: (1) non-uniform insertion length of the post-coupler from the tank wall; (2) increment of the diameter of several post-couplers. The recipe of the fine post-coupler tuning is described.

The construction of the initial part of the J-PARC linac has been started at KEK for beam tests before moving to the JAERI Tokai campus, where J-PARC facility is finally to be constructed. The RFQ and MEBT (Medium Energy Beam Transport) have already been installed at KEK, and the beam test has been performed successfully. In this paper, the experimental results of the beam tests are presented together with simulation results with a 3D PIC (Particle-In-Cell) code.

The present status of the development of the 1-GeV proton linac for the Japanese Hadron Project is reported. The linac is composed of an H/sup -/ ion source, a 432-MHz RFQ (radio-frequency quadrupole) linac (3 MeV), a 432-MHz drift-tube linac (148 MeV), and a 1296-MHz high- beta linac (1 GeV). An electroforming method for sealing a 432-MHz drift tube was developed. Results of field measurement are presented for a cold model of a drift-tube linac. The high- beta linac is described in detail. A study of an annular-coupled structure indicates that this structure is promising for the project. >

In a large ring with extremely heavy beam loading, such as a B-factory, it is possible that the accelerating mode, itself, gives rise to a longitudinal coupled-bunch instability. In order to solve this problem, T. Shintake (1993) has proposed to attach a TE015-mode storage cavity to an accelerating cavity. It has subsequently been shown that the system can be put into practical use if a coupling cavity is added in between the two cavities. The three-cavity system, which is now referred to as an accelerator resonantly coupled with an energy storage (ARES), is under development for the KEKB.

The HOM absorber for the normal conducting RF cavity of the KEK B-factory (KEKB) was designed. Sixteen bullet-shape sintered SiC (silicon carbide) ceramics are used for HOM absorption. The HOM power to be handled will be about 10 kW per cavity, corresponding to about 1 kW per absorber. A prototype of SiC absorber was made to verify the performance as a HOM absorber in vacuum. The high power test was carried out successfully using a pulsed klystron (f=1296 MHz). The design of the HOM absorber and the results of the high power test are discussed.

The input coupler for the normal conducting RF cavity of the KEK B-factory (KEKB) was designed comprising a disk-type coaxial ceramic window and a door-knob transition. We designed two different types of window structure; one is a choke-type structure and the other is a under- and over-cut structure. The fabrication of two types of coupler is underway in order to confirm the RF properties.

KEK B-Factory (KEKB) was terminated in 2010 after achieving the world record luminosity of 2.11 × 1034 cm−2s−1. This paper describes the design features, performance, and operation results of the KEKB RF systems, which include a lot of original RF technologies and methods to store an electron/positron beam over 1 A stably. To cope with beam instabilities caused by large beam currents, two new types of normal and superconducting (SC) cavities with large stored energy were developed and successfully operated. For a new beam colliding scheme called crab crossing, two SC crab cavities were introduced and boosted the peak luminosity. Performance of these cavities is reported, along with the lowlevel and high-power RF systems, and the cryogenic system for the SC cavities. The status of the RF system upgrade towards SuperKEKB, which aims at a luminosity of 8.0 × 1035 cm−2s−1, is briefly described. © The Author(s) 2013. Published by Oxford University Press on behalf of the Physical Society of Japan. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department. Copyright © 2013 The Physical Society of Japan Other Oxford University Press sites: Oxford University Press

A stable radioactive source in vacuo was obtained by a modified horizontal lifting method of Langmuir-Blodgett (L/B) film. In spite of the slight consumption of the substrate solution (only 2–2.5 ml) for preparing a 15 mm×25 mm sized L/B film containing four molecular layers of 109Cd icosanoate, the deposition of the film was complete. The reliability of the deposited films by this method was confirmed by their radioactivities, deposition ratios and autoradiographs. The condition to obtain a larger sized homogeneous L/B film (20–25 mm×102 mm) was also examined. Two or four molecular layers of nonradioactive Cd icosanote deposited on the L/B film of 109Cd icosanoate did not influence the intensity of the γ-ray of 88.0 KeV. Concequently, it is possible to obtain the high radioactive source by the deposition of the multilayers of 109Cd icosanoate. Spectra of L2 and L3 conversion electrons from the 109Cd in its built-up film were also determined. In conclusion, the present depositing method for the L/B film i...

The second measurement of the neutrino mass at INS has been carried out. Combining the new data with the result of the first measurement, a preliminary upper limit of 25 eV at the 95% confidence level has been obtained for the neutrino mass from only statistical consideration.

The end-point energy of 3 H β-decay is re-examined and found as E 0 =18582.5±4.1 eV by a new measurement of the electron energy spectrum at INS. Also, an upper limit of the electron anti-neutrino mass is obtained as m ν

The β-spectrum in 3 H decay has measured at INS with an energy resolution of 10–16 eV. The overall response function of the spectrometer system was reliably obtained with a reference 109 Cd source having the same chemical structure as the 3 H source. An upper limit of 32 eV has been obtained for the mass of the electron anti-neutrino with statistical and systematic errors.

Langmuir—Blodgett (L/B) films of tritiated fatty acid were prepared to measure the electron antineutrino mass. The measurement requires that a source should be highly radioactive, homogeneous, very thin, uniform, and nonvolatile in vacuo . With regard to the volatility, the L/B film of fatty acid is, in general, not very stable in vacuo , and desorption of the source molecules results in the main background rates of the measurement and reduces the sensitivity of the mass determination. In the present work, we examined the stability of the L/B film in vacuo , and tried to improve the stability of the film by (i) perfect formation and deposition of metal soap molecules that are more resistant against evaporation than the original fatty acid molecules, and (ii) cooling of the 3 H source with liquid nitrogen in order to reduce the evaporation. Finally, a uniform and highly radioactive 3 H source, which is nonvolatile even at a pressure of 10 −4 Pa, was obtained using the Langmuir—Blodgett film of cadmium [ 3 H]icosanoate (sp act 200,000 Ci/mole).

The Ag KLL Auger spectrum has been measured with an energy resolution of 8 eV. The energies and the intensities of all nine lines are precisely determined with 1–2 orders of magnitude better accuracies than those in the previous experiment. The data obtained are found to be in good agreement with the theoretical calculations.

The energy loss of 18 keV β-rays in a very thin Langmuir-Blodgett film of a chemical compound, arachidic acid, has been studied.

A stable radioactive source in vacuo was obtained by a new depositing method of Langmuir–Blodgett (L/B) film. In spite of the slight consumption of the substrate solution (only 2–2.5 ml) for preparing a 15 mm × 25 mm sized L/B film containing four molecular layers of 109Cd-eicosanoate, the deposition of the film was complete.

Ag KLM and KLN Auger spectra have been measured with a momentum resolution of 0.02%. With this resolution, most of the lines in these transitions are well separated and the complex spectral structure is revealed. Energies and intensities of these lines are precisely determined and compared with the results of the theoretical calculations.

The energy-loss spectra of 18 keV electrons in adsorbed residual gas on Langmuir-Blodgett film, made from arachidic acid (C20H40O2) and cooled at temperatures of -10°C, -35°C and -60°C, were measured through use of an electron source that also acted as an adsorbent. In addition, the amount of adsorbed residual gas was estimated from the energy-loss probability.

Large sized and uniformly deposited 169Yb sources were prepared with the following properties: the intensity variation and the deposited thickness were 2, respectively, for the source sizes of 35×45 mm2 and 20×100 mm2 with the deposited activity of 20-50 µCi, as an energy reference source for the neutrino mass measurement at INS. The technical details of the preparation: the processes of chemical separation and purification, and vacuum-deposition, are here reported.