TRIAC Progress Report - KEK

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The JAEA SC-linac comprises 10 cryostats and 9 magnetic quadrupole doublets set between cryostats. Four super-conducting cavities made of niobium are installed in each cryostat. The cavities are 129.8-MHz two-gap λ/4 resonators. The optimum ion velocity is 10 % of light velocity for all cavities. This linac has large velocity acceptance, since the number of accelerating gap per cavity is only two and RF phase of each cavity can be independently adjusted. The relation between input and output energies were calculated for the cases of q/A = 1/4 and 1/7 under the condition that the gap voltage is 375 kV and the accelerating phase -20 o at first gap. Figure 2-21 shows that the SC-linac can accelerate ions with the injection energies higher than 1.1 MeV/nucloen. When the injecting energy is 1.4 MeV/nucleon, the maximum energy is ~ 7 MeV/nucleon for ions with q/A = 1/4. A designed beam-transport line between IH and SC linacs is 37.71 m in total length, and comprises 19 quadrupole magnets, two 45 o deflection magnets and two 25.96-MHz rebunchers [2-16]. Performances of the beam transport line were examined by means of the beam simulations using MAGIC code [2-17]. The results are shown in Fig. 2-22. The obtained important results are as follows: Beam transmission efficiency from IH entrance to SC linac exit is 67 %. If 129.8-MHz buncher and 259.6-MHz sub-harmonic buncher for injecting the tandem beam into SC linac are used instead of two rebunchers, the efficiency is 40 %. From above results, it is concluded to be a realistic plan to connect the TRIAC to the SC linac by using only existing devices without constructing newly a booster linac and two rebunchers. Test experiments: As mentioned above, a slight modification of acceleration mode of the IH linac, especially final two acceleration stages of the IH linac, has been simulated for higher maximum energy than designed: The higher energy could allow us to further accelerate RI beams by SC-linac without additional equipments related to acceleration, such as re-buncher and pre-booster between the IH and the SC linacs. The simulation was confirmed by a test operation; indeed the maximum energy can be increased from 1.1 to 1.4 MeV/nucleon at the present facility. For the SC-linac where at least 2 MeV/nucleon at the injection is required for the effective acceleration, on the other hand, a 40 Ar 10+ beam injected from the JAEA tandem accelerator was successfully accelerated from 1.4 to 4.53 MeV/nucleon. It should be noted, however, that in this scheme the beam transport and acceleration efficiency of the SC-linac is lower than what is expected in the ideal case. Therefore, the present conclusion resulting from the test experiments and simulations should be taken as a first step for step-by-step realization of the ideal plan. 28
2-4-4. Development of superconducting low-β resonators [2-18] As mentioned earlier for the specification of the post-accelerators at the TRIAC (see subsection 2-4-1), the cavities were modified to match the resonant frequency of the superconducting resonators (129.8-MHz two-gap λ/4 resonators) of the JAEA SC-linac (i.e. from 25.5 to 25.96 MHz, from 51 to 52.92 MHz for the SCRFQ and the IH, respectively), where the injection energy of at least 2 MeV/nucleon is required for the effective acceleration. Therefore, we need a pre-booster between the IH and SC linacs for boosting the output energy of the IH (1.1 MeV/nucleon) to 2 MeV/nucleon, although we have discussed in the previous subsection the possibility to connect the present TRIAC to the SC linac by using only existing devices. We have designed and fabricated a superconducting twin-quarter-wave resonator (Twin-QWR) made of niobium and copper as a pre-booster at the TRIAC. It has 2 drift tubes and 3 acceleration gaps, as shown in Fig. 2-23. The resonant frequency is 129.8 MHz, which is the same for the existing QWRs in the SC linac. The optimum beam velocity βopt (= vopt/c) is 0.06. Fig. 2-23. Cross sectional view of Twin-QWR. 29
Page 1 and 2: TRIAC Progress Report TRIAC collabo
Page 3 and 4: i KEK Progress Report 2011-1 June 2
Page 5 and 6: PREFACE The Tokai Radioactive Ion A
Page 7 and 8: 1. Introduction Following the succe
Page 9 and 10: maximum available beam power for th
Page 11 and 12: container of ion source and uranyl
Page 13 and 14: 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: Encouraged by the new finding, as t
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 67 and 68: GEM-MSTPC among the accumulated dat
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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