InP solid state detector and the observation of low energy solar neutrinos

A large volume radiation detectors using a semi-insulating Indium Phosphide (InP) wafer have been developed for Indium Project on Neutrino Observation for Solar interior (IPNOS) experiment. The volume has achieved to 20mm3 , and this is world largest size among the detector observed gammas at hundred keV region. Although the depletion layer, most of charge are generated by an induction, and the charge collection efficiency achieves 50 to 60%, which is determined by the detector thickness and the carrier drift length (Ld = 120μm). The energy resolution is obtained by 25%. We measured actual backgrounds from 115 In beta decay, and also the effect of radiative Bremsstrahlung from those betas. No significant event was found in the measurement and the radiation such as Bremsstrahlung from InP detector could be negligible

Development of a method for measuring rare earth elements in the environment for future experiments with gadolinium-loaded detectors

Demand to use gadolinium (Gd) in detectors is increasing in the field of elementary particle physics, especially in neutrino measurements and dark matter searches. Large amounts of Gd are used in these experiments. To assess the impact of Gd on the environment it is becoming important to measure the baseline concentrations of Gd. Such measurement, however, is not easy due to interference by other elements. In this paper a method for measuring the concentrations of rare earth elements, including Gd, is proposed. In the method, inductively coupled plasma-mass spectrometry is utilized after collecting the dissolved elements in chelating resin. Results of the ability to detect anomalous concentrations of rare earth elements in river water samples in the Kamioka and Toyama areas are also reported

Supernova burst and relic neutrino sensitivity studies in the Hyper-Kamiokande Korean sites

Hyper-Kamiokande is a next-generation water Cherencov detector for neutrino physics. Its large volume (260 kton × 2) allows Supernova burst (SN) neutrino and Supernova Relic Neutrino (SRN) search much more promising than current Super-Kamiokande detector (50 kton). With an alternative plan of locating one of the two identical detectors to Korea, better physics sensitivities are expected because of less muon flux and its spallation isotopes due to more overburden in Korean candidate sites than Japanese Hyper-Kamiokande site (Tochibora). According to our study using simple MC 102 SRN events (5.2 sigma) in a Korean site and 71 SRN events (4.2 sigma) in the Japanese site are expected for 10 years of operation for one detector. Sensitivity studies using a full MC will be performed in the near future

Influence of Soya Oil Blended with Fish Oil on Growth Performance and Lipid Profile of Red Sea Bream Pagrus major

Continuous increase in fish feed prices due to deterioration of fish oil sources and quality catalyzes intensive research efforts to study alternatives for dietary fish oil such as soya oil.  Being rich in linolenic acid (C18:2n-6), soya oil has a competitive edge as an arachidonic acid (ARA) precursor. A 50-day feeding trial was conducted to evaluate the effects of dietary soya oil as a substitute for fish oil on growth performance and lipid composition of juvenile red seabream, Pagrus major.  Four types of iso-nitrogenous experimental diets formulated in this feeding trial consisted of 100% fish oil (10F), 80% fish oil and 20% soya oil (8F2S), 60% fish oil and 40% soya oil (6F4S), and finally, 40% fish oil and 60% soya oil (4F6S). All diets were fed to triplicate groups of 15 red seabream with an initial mean weight of 4.9 ± 0.1 g twice daily to apparent satiation. Our results demonstrated that inclusion of soya oil as a lipid source to partially replace fish oil in red seabream diet led to the highest body weight gain (BWG) in 10F (837.2 ± 2.2%), followed by 8F2S (786.9 ± 38.3%), 6F4S (764.6 ± 5.2%) and 4F6S (682.0 ± 17.2%), respectively, without any significant differences among 10F, 8F2S and 6F4S. Soya oil inclusion also gradually decreased BWG and specific growth rate (SGR); both BWG and SGR in 4F6S were significantly lower than other treatments. Feed conversion ratio (FCR) and feed intake (FI) showed no significant differences among treatments. Survival rate of all treatments exceeded 90% although the hepatosomatic index (HSI) in 4F6S was significantly higher than other treatments and serum glutamic-oxaloacetic transaminase (GOT) increased gradually with a higher inclusion of soya oil. Lipid deposition in the whole body was the highest in fish fed with dietary 10F and decreased in relation to the elevated concentration of soya oil in diets. The ventral muscles had doubled the amount of lipid deposition as compared to dorsal muscles. Dominance of saturates among total fatty acid composition particularly C16:0, was similarly observed in the dorsal and ventral muscles as well as the liver. Saturates, monoenes, n-3 and ratio of n-3/n-6 observed have a similar gradient degradation in the dorsal and ventral muscles and the liver. An inverse relationship of inclusion level of soya oil on eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) in both dorsal and ventral muscles including the liver was also observed. In conclusion, diets not exceeding 40% soya oil are suitable as fish oil replacement in the diet of juvenile red seabream without significantly affecting the overall growth performance of this fish. Keywords: Pagrus major, red seabream, soya oil, growth performances, lipid profile ABSTRAK Kenaikan harga makanan ikan yang berterusan akibat kekurangan sumber dan juga kualiti minyak ikan, telah menggalakkan lebih banyak penyelidikan untuk mengkaji minyak soya sebagai sumber alternatif kepada minyak ikan. Kekayaan sumber asid linolenik (C18:2n-6) telah menjadikan minyak soya sebagai pelopor kepada asid arakidonik (ARA). Satu kajian pemakanan selama 50 hari telah dijalankan untuk menilai kesan pemakanan dengan menggunakan minyak soya ke atas tumbesaran dan komposisi lemak dalam ikan merah, Pagrus major juvenil. Empat jenis diet kajian iso-nitrogenus telah diformulasikan dalam kajian ini; yang terdiri daripada 100% minyak ikan (10F), 80% minyak ikan dan 20% minyak soya (8F2S), 60% minyak ikan dan 40% minyak soya (6F4S), dan 40% minyak ikan dan 60% minyak soya (4F6S). Semua diet telah diberikan dua kali sehari sehingga kenyang kepada sejumlah 15 ekor ikan merah dengan purata berat awal 4.9 + 0.1 g secara triplikat. Keputusan menunjukkan bahawa penggunaan minyak soya sebagai sumber lemak untuk menggantikan sebahagian sumber minyak ikan dalam ikan merah telah memberikan BWG dalam perlakuan 10F (837.2 + 2.2%), diikuti dengan 8F2S (786.9 + 38.3%), 6F4S (764.6 + 5.2%) dan 4F6S (682.0 + 17.2%), masing-masing, tanpa perbezaan yang bererti di antara perlakuan 10F, 8F2S and 6F4S. Penggunaan minyak soya juga mengurangkan BWG dan SGR secara perlahan-lahan; kedua-dua BWG and SGR dalam perlakuan 4F6S menunjukkan nilai rendah yang bererti berbanding perlakuan yang lain. Nisbah penukaran makanan (FCR) dan kadar pengambilan makanan (FI) telah menunjukkan tiada perbezaan yang bererti di antara semua perlakuan. Kadar kemandirian untuk semua perlakuan adalah melebihi 90% walaupun indeks hepatosomatik (HSI) dalam perlakuan 4F6S adalah lebih tinggi secara bererti berbanding perlakuan yang lain, dan serum glutamik-oksaloasetik transaminase (GOT) pula berkurangan dengan penambahan minyak soya. Pengumpulan lemak di keseluruhan tubuh adalah tertinggi dalam ikan yang diberi makanan 10F dan berkurangan dengan penambahan kepekatan minyak soya dalam diet. Kandungan lemak pada otot ventral juga telah meningkat sebanyak dua kali ganda berbanding dengan pada otot dorsal. Kandungan saturat dari jumlah komposisi asid lemak terutamanya C16:0 adalah lebih dominan pada otot dorsal, otot ventral dan hati. Saturat, monoene, n-3 dan nisbah n-3/n-6 telah menunjukkan kecerunan degradasi yang sama pada otot dorsal, otot ventral dan hati. Peningkatan minyak soya menyebabkan kesan songsang terhadap aras asid eikosapentanoik (EPA) and asid dokosaheksanoik (DHA) di kedua-dua otot dorsal dan ventral dan juga hati. Sebagai kesimpulan, diet yang mengandungi minyak soya tidak melebihi 40% adalah paling sesuai sebagai pengganti minyak ikan tanpa memberi kesan yang bererti kepada tumbesaran ikan merah juvenil. Kata kunci: Pagrus major, ikan merah, minyak soya, tumbesaran, profil lipid

Distillation of Liquid Xenon to Remove Krypton

A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe = $\sim 3 \times 10^{-12}$ was achieved. This development is crucial in facilitating high sensitivity low background experiments such as the search for dark matter in the universe.Comment: 15 pages, 11 figure

Self-shielding effect of a single phase liquid xenon detector for direct dark matter search

Liquid xenon is a suitable material for a dark matter search. For future large scale experiments, single phase detectors are attractive due to their simple configuration and scalability. However, in order to reduce backgrounds, they need to fully rely on liquid xenon's self-shielding property. A prototype detector was developed at Kamioka Observatory to establish vertex and energy reconstruction methods and to demonstrate the self-shielding power against gamma rays from outside of the detector. Sufficient self-shielding power for future experiments was obtained.Comment: 8 pages, 8 figure

Scintillation-only Based Pulse Shape Discrimination for Nuclear and Electron Recoils in Liquid Xenon

In a dedicated test setup at the Kamioka Observatory we studied pulse shape discrimination (PSD) in liquid xenon (LXe) for dark matter searches. PSD in LXe was based on the observation that scintillation light from electron events was emitted over a longer period of time than that of nuclear recoil events, and our method used a simple ratio of early to total scintillation light emission in a single scintillation event. Requiring an efficiency of 50% for nuclear recoil retention we reduced the electron background to 7.7\pm1.1(stat)\pm1.2 0.6(sys)\times10-2 at energies between 4.8 and 7.2 keVee and to 7.7\pm2.8(stat)\pm2.5 2.8(sys)\times10-3 at energies between 9.6 and 12 keVee for a scintillation light yield of 20.9 p.e./keV. Further study was done by masking some of that light to reduce this yield to 4.6 p.e./keV, the same method results in an electron event reduction of 2.4\pm0.2(stat)\pm0.3 0.2(sys)\times10-1 for the lower of the energy regions above. We also observe that in contrast to nuclear recoils the fluctuations in our early to total ratio for electron events are larger than expected from statistical fluctuations.Comment: 25 pages, 15 figure

Measurement of γ\gamma-ray production via neutron-16^{16}O reaction using a 77 MeV quasi-monoenergetic neutron beam

Understanding of $\gamma$-ray production via neutron interactions on oxygen is essential for the study of neutrino neutral-current quasielastic interactions in water Cherenkov detectors. A measurement of $\gamma$-ray production from such reactions was performed using a 77~MeV quasi-monoenergetic neutron beam. Several $\gamma$-ray peaks, which are expected to come from neutron-${\rm ^{16}O}$ reactions, are observed and production cross sections are measured for nine $\gamma$-ray components of energies between 2 and 8~MeV. These are the first measurements at this neutron energy using a nearly monoenergitic beam.Comment: 16 pages, 20 figures, 4 table