J. H. So

Neutrino-Less Double Beta Decay Experiment Using Ca

Search for neutrino-less double beta decay of 100Mo is proposed using active method with Ca 100MoO4 scintillation crystals which show the brightest scintillation light among variety of inorganic scintillation materials containing Mo. Study of X-ray luminescence and scintillation properties such as energy response, number of photoelectrons/keV, absolute light yield, decay time, pulse shape discrimination and radioactive contamination of CaMoO4 crystals grown by the Czochralski method with different conditions are presented. Further R&D of resolution optimization, crystal quality improvement and background reduction are underway. Significant improvement of sensitivity to neutrino-less double beta decay can be achieved by using 10 Mo enriched Ca 100MoO4 crystals with good energy resolution and low background. Further reduction of background induced by 48 Ca two neutrino double beta decay can be achieved by using 48Ca depletion. We are planning to install several kilograms of Ca 100MoO4 crystals depleted in 48Ca at underground laboratory for the neutrino-less double beta decay experiment in the near future.

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AMoRE (Advanced Mo based Rare process Experiment) collaboration is going to use calcium molybdate crystals as cryogenic scintillation detector in a search for neutrinoless DBD of 100Mo isotope. Simultaneous detection of phonons and light will be used to reject internal background. A FWHM resolution of 0.2% in the phonon channel has been achieved with a 0.5 cm3 crystal. Several 40Ca100MoO4 crystals (≈ 0.5 kg) have been developed from enriched 100Mo and depleted 40Ca materials. The light yield of these crystals has been shown to be comparable with reference CaMoO4 scintillators for temperatures ranging down to 8 K. The content of dangerous radioisotopes in the crystals is under measurement. The projected sensitivity of the experiment for a 250 kg × years exposure is lim T1/2 ~ 3 × 1026 years, which corresponds to the effective Majorana neutrino mass mv ~ 0.02 – 0.06 eV.

MoO

Scintillation properties and radioactive contamination of calcium molybdate scintillating crystals depleted in ⁴⁸Ca and enriched in ¹⁰⁰Mo (⁴⁰Ca¹⁰⁰MoO₄ ) have been studied to prepare a ¹⁰⁰Mo-based neutrinoless double beta decay experiment. The prospects of a neutrinoless double beta decay experiment using ⁴⁰Ca¹⁰⁰MoO₄ crystals are discussed.

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The simultaneous measurement of heat and light signals from a 40Ca100MoO4 scintillating crystal was performed at temperatures of tens of milli-kelvin using a scintillating bolometric detector. The crystal was instrumented with a pair of low-temperature detectors, consisting of a metallic magnetic calorimeter for reading the phonon signals and a light detector based on a Ge light absorber, to simultaneously measure the scintillation light and phonon signals. This article presents the principle and performance, such as the event separation capability, of this simultaneous heat/light measurement system.

Scintillation Crystals

The response of CsI(Tl) crystals to nuclear recoils and gammas down to 3 keV has been studied, and it has been demonstrated that the pulse shape discrimination capability for CsI(Tl) is better than that for NaI(Tl). Extensive study of internal background of CsI powder was performed and a lot of efforts have been made to reduce the internal background sources such as 137Cs and 87Rb. The 137Cs concentration of 2 mBq/kg was achieved successfully in the CsI powder using ultra-pure water for whole extraction process. The Rb concentration was successfully reduced to be less than 1 ppb by the recrystallization method. The CsI(Tl) crystal used for the experiment was grown with the ultra-low background CsI powder and a dimension of the CsI(Tl) crystal is 8times8times30 cm3 which corresponds to weight of 8.7 kg. The number of photoelectrons is measured to be about 4-6/keV with a RbCs photocathode PMT. The background of CsI(Tl) crystals were measured in the shielding of 30 cm thick mineral oil, 15 cm thick lead, 5 cm thick polyethylene and 10 cm copper at the 700 m minimum depth of underground laboratory at YangYang Pumped Storage Power Plant in Korea. The WIMP search with low background CsI(Tl) crystals has been carried out by the Korean Invisible Mass Search (KIMS) Collaboration and the lower limit on WIMP-nucleon cross section are reported.

AMoRE experiment: a search for neutrinoless double beta decay of 100Mo isotope with 40Ca100MoO4 cryogenic scintillation detector

Abstract The first phase of the Advanced Mo-based Rare process Experiment (AMoRE-I), an experimental search for neutrinoless double beta decay ( 0 ν β β ) of 100Mo in calcium molybdate ( 40 Ca100MoO4) crystal using cryogenic detection techniques, is in preparation at the YangYang underground laboratory (Y2L) in Korea. A GEANT4 based Monte Carlo simulation was performed for the first-phase AMoRE detector and shield configuration. Background sources such as 238U, 232Th, 235U, and 210Pb from inside the crystals, surrounding materials, outer shielding walls of the Y2L cavity were simulated. The estimated background rate in the region of interest was estimated to be 1.5 × 10 − 3 counts/keV/kg/yr (ckky). The effects of random coincidences between backgrounds and two-neutrino double beta decays of 100Mo as a potential background source were estimated to be 2.3 × 10 − 4 ckky.

Scintillation Properties and Internal Background Study of

We have studied channeling effects in a cesium iodide (CsI) crystal that is similar in composition to the ones being used in a search for Weakly Interacting Massive Particles (WIMPs) dark matter candidates, and measured its energy-dependent quenching factor, the relative scintillation yield for electron and nuclear recoils. The experimental results are reproduced with a GEANT4 simulation that includes a model of the scintillation efficiency as a function of electronic stopping power. We present the measured and simulated quenching factors and the estimated effects of channeling

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We developed a SrCl2 crystal scintillator for 0υ Electron Capture/β+ decay search, and 4π CsI(Tl) tagging detector to reduce the background. This experimental system was installed at the YangYang underground laboratory which is for the WIMP search by KIMS group. The system ran for 60 days and we have finished analyzing for 2 hits back to back coincidence signal selection.

Ca

For the pilot and feasibility studies on the development of beam utilization technologies of PEFP (proton engineering frontier project), the test beam line was installed at the MC-50 cyclotron of KIRAMS (Korea institute of radiological and medical sciences) [1-2]. The energy measurement of proton beam with high accuracy is very important for the some experiments such as radiation hardness test of semiconductor devices for the spacecraft, detector development and test for the nuclear physics, etc. Energy measurement of 35 MeV and 45 MeV proton beam using a 5 mm thick Si(Li) in air was performed. The energy was controlled by Al degrader in the range of 0.02 mm~6.2 mm. The measured value was compared to the results of code simulation using SRIM 2003.

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In order to investigate discrimination between nuclear recoil and electron recoil events for the KIMS-NaI dark matter search experiment, we measured the pulse shapes produced by neutrons and gamma rays in a NaI(Tl) crystal. Relatively good pulse shape discrimination (PSD) power due to high light output of recently developed crystals makes it possible to test whether the annual modulation signal observed by the DAMA/LIBRA experiment is caused by nuclear recoil events. We applied the PSD to underground data taken with a 9.15 kg low-background and high-light-output NaI(Tl) crystal for 134 days. Good agreement between underground data and electron recoil events was observed.