TRIAC Progress Report - KEK

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successfully employed to measure the 8 Li(α, n) 11 B reaction cross sections. The 8 Li beam with an intensity of 3x10 4 pps on average was injected into the GEM-MSTPC for about 3 days at the TRIAC. Neutron counter GEM-MSTPC 8 Li beam Fig. 3-8. Experimental set-up for the measurements of 8 Li(α,n) cross sections. The beam of 8 Li is counted one-by-one by the MCP and then injected into the GEM-MSTPC, where the occurrence of the reaction (sudden change of the energy loss by recoil 11 B) is identified and the simultaneously emitted neutron is measured by the neutron counter. Although the intensity was limited by the data acquisition rate allowed in the experiment because of unexpectedly low reduction rates of the veto counter installed downstream of the GEM in order to remove beam particles without inducing reactions of our interest (i.e. elastic scattering), the average injection rate is about 10 times larger than that in our previous measurement using the RMS. In the experiment, the width of the pad reduced by a factor of three as compared that in the precious measurement at the RMS (but with the same operating pressure of the active gas) allows narrower beam energy binning, accordingly higher energy resolution for Ecm in the measurement of the excitation function. The picture of the experimental set-up is shown in Fig. 3-8. The trigger for data acquisition was generated from the coincidence of signals of the MCP and the neutron counter wall. Since neutron detectors had significant room background, recorded data were mainly composed of accidental events. In order to identify true reaction events, first of all, it is necessary to search for events with a sudden change in the energy loss along the particle trajectory identified by the 60 MCP
GEM-MSTPC among the accumulated data. Figure 3-9 shows a typical example of true reaction. The data analysis for selecting true reaction events on event-by-event bases is in progress. Fig. 3-9. Typical event pattern of 8 Li(α, n) 11 B reaction. (Left): Energy losses measured by pad (dE/pad) are presented as a function of the number of anode pads, where the beam comes in from the low pad number. (Right): Horizontal (x) and vertical (y) positions of the three-dimensional particle trajectories, where the beam direction was defined as the z-axis (i.e. increasing pad numbers in the figures). Using a stable ion beam of 4 He provided by the TRIAC, the RNB-KJ04 (Spokesperson: H. Makii (JAEA) and H. Miyatake (JAEA), Collaboration: KEK (9), JAEA (5), RIKEN (1), Osaka Univ. (1)) was proposed to directly measure the 12 C(α, γ) 16 O reaction cross sections and determine the strength of electric-dipole (E1) and/or -quadrupole (E2) components in the α-capture cross sections (decaying strength of excited 16 O by emitting γ-rays of corresponding multi-polarities) at stellar energies. The reaction plays an important role at the stage of helium-burning in stellar evolution; its reaction rate determines the mass fraction of 12 C and 16 O after the stellar helium-burning, the abundance of elements from oxygen to iron, and the iron-core mass before 61
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TRIAC Progress Report TRIAC collabo
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i KEK Progress Report 2011-1 June 2
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PREFACE The Tokai Radioactive Ion A
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1. Introduction Following the succe
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maximum available beam power for th
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container of ion source and uranyl
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gaseous and volatile elements (e.g.
Page 15 and 16: = 10.6 m) were 4.5 %, that for 146
Page 17 and 18: with different plasma volumes [2-6]
Page 19 and 20: ECR plasma: We used natural helium
Page 21 and 22: higher efficiency for gaseous eleme
Page 23 and 24: The asymmetric component representi
Page 25 and 26: ut differs from the electron-loss p
Page 27 and 28: consumption in the cavity is less t
Page 29 and 30: measured with Faraday cups, FC1, FC
Page 31 and 32: y turning off the supply of RF powe
Page 33 and 34: Encouraged by the new finding, as t
Page 35: 2-4-4. Development of superconducti
Page 40 and 41: accelerating the radioactive ion be
Page 42 and 43: Fig. 2-29. Photos of the pre-bunche
Page 44 and 45: For the proposed experiment, the po
Page 46: a diagonal direction. The monitors
Page 49: charge state of xenon ions by using
Page 52 and 53: electrode as shown in Fig. 2-40) sh
Page 54 and 55: CO2 (10 %) and 16 kPa, respectively
Page 56 and 57: Although the gain shift of THGEM#3
Page 58 and 59: 3. Experiments at the TRIAC Since t
Page 60 and 61: Fig. 3-1. Schematic view of the det
Page 62 and 63: -element abundances up to the third
Page 64: higher reliability of the experimen
Page 69 and 70: upstream of the pre-buncher, avoidi
Page 72 and 73: The process of nuclear polarization
Page 74 and 75: annealed platinum foil (stopper foi
Page 78 and 79: the observed CP-violating phenomena
Page 80 and 81: offline data analysis, about 1-Mega
Page 82 and 83: Secondary 9 Li ions extracted from
Page 84 and 85: Fig.3-24. γ ray energy spectra coi
Page 86 and 87: In the experiments of RNB-J02/03 (S
Page 88 and 89: atio), a diffusion coefficient was
Page 91 and 92: Although the data for β-LiAl and
Page 93 and 94: In the experiment of RNB-K06 ((Spok
Page 95 and 96: difference spectra, more specifical
Page 97 and 98: Mass, which is one of the most fund
Page 99: gamma rays. 111 In, which decays to
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TRIAC Progress Report - KEK

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