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Takeuchi, Yusuke*; Tojo, Junji*; Yamanaka, T.*; Nakazawa, Yuga*; Iinuma, Hiromi*; Kondo, Yasuhiro; Kitamura, Ryo; Morishita, Takatoshi; Cicek, E.*; Ego, Hiroyasu*; et al.
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.562 - 564, 2022/10
A muon linac is under development for future muon g-2/EDM experiments at J-PARC. The linac provides a 212 MeV muon beam to an MRI-type compact storage ring. After the initial acceleration using the electrostatic field created by mesh and cylindrical electrodes, the muons are accelerated using four types of radio-frequency accelerators. To validate the linac design as a whole, end-to-end simulations were performed using General Particle Tracer. In addition, error studies were performed to investigate the effects on beam and spin dynamics of various errors in the accelerator components and input beam distribution. This paper describes the results of the end-to-end simulations and error studies.
Yee-Rendon, B.
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.310 - 313, 2022/10
Accelerator-driven subcritical systems (ADS) offer an advantageous option for the transmutation of nuclear waste. ADS employs high-intensity proton linear accelerators (linacs) to produce spallation neutrons for a subcritical reactor. Besides the challenges of any megawatt proton machine, ADS accelerator must operate with stringent reliability to avoid thermal stress in the reactor structures. Thus, ADS linacs have adopted a reliability-oriented design to satisfy the operation requirements. This work provides a review and the present status of the ADS linacs in the world.
Nakazawa, Yuga*; Iinuma, Hiromi*; Iwata, Yoshiyuki*; Cicek, E.*; Ego, Hiroyasu*; Futatsukawa, Kenta*; Kawamura, Naritoshi*; Mibe, Tsutomu*; Mizobata, Satoshi*; Otani, Masashi*; et al.
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.275 - 278, 2022/09
We conducted a high-power test of a prototype cavity of a 324-MHz inter-digital H-mode drift tube linac (IH-DTL) for the muon g-2/EDM experiment at J-PARC. This prototype cavity (short-IH) was developed to verify the fabrication methodology for the full-length IH cavity with a monolithic DT structure. After 40 h of conditioning, the short-IH has been stably operated with an RF power of 88 kW, which corresponds to 10% higher accelerating field than the design field (E0) of 3.0 MV/m. In addition, the thermal characteristics and frequency response were measured, verifying that the experimental data was consistent with the three-dimensional model. In this paper, the high-power tests of this IH-DTL for muon acceleration are described.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.180 - 183, 2022/09
The Japan Atomic Energy Agency (JAEA) has proposed an accelerator-driven subcritical system (ADS) to efficiently reduce high-level radioactive waste generated at nuclear power plants. One of the challenging R&D aspects of ADS is the reliability of the accelerator. In preparation for the full-scale design of the CW proton linac for the JAEA-ADS, we are now prototyping a low-beta (around 0.2) single spoke cavity. Since there is no experience in Japan in manufacturing a superconducting spoke cavity, prototyping and performance testing of the cavity is essential to ensure the feasibility of the JAEA-ADS linac. In the Japanese fiscal year 2021, we have started welding cavity parts together. By preliminarily examining the electron beam welding conditions, each press-formed niobium part was joined with a smooth welding bead. At present, we have fabricated the cavity's body part.
Fuwa, Yasuhiro; Moriya, Katsuhiro; Takayanagi, Tomohiro
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.364 - 367, 2022/09
MEBT1 (Medium Energy Beam Transport 1) of the J-PARC LINAC is a 3 MeV beam transport system located between the RFQ (Radio Frequency Quadrupole) and DTL (Drift Tube Linac). In the MEBT1, the beam-optical matching for injection into DLT and chopping for injection into acceleration phase of 3 GeV synchrotron, located downstream to the LINAC, are performed. The characteristics of MEBT1 are an important factor in determining the beam quality in the J-PARC accelerator facility. To achieve beam power of 1 MW and beyond, improving the stability and reliability of MEBT1 is an important development issue. The application of permanent magnets to the beam focusing system to the MEBT1 is under consideration to achieve improved stability and reliability. In this presentation, we report the design of focusing magnets using permanent magnet material and the results of the lattice study of MEBT1 with permanent magnets.
Tamura, Jun; Kondo, Yasuhiro; Morishita, Takatoshi; Naito, Fujio*; Otani, Masashi*
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.177 - 179, 2022/09
Various types of cavity structures are typically used in hadron linacs, depending on the energy range of the beam particle. This is especially the case in a normal-conducting linac, because the cavity's acceleration efficiency varies with the velocity of the synchronous particle. For low-energy proton acceleration, while Alvarez drift-tube linacs (DTLs) are the most prevalent, TE-mode accelerating structures, which could also be called H-mode structures, are also widely used immediately after an initial radiofrequency quadrupole linac (RFQ). At present, the representative structures of TE modes are interdigital H-mode (IH) DTL and crossbar H-mode (CH) DTL, which are based on the TE11-mode pillbox cavity and TE21-mode pillbox cavity, respectively. In this presentation, acceleration efficiency of TE-mode structures including higher-order TE-modes such as TE31 and TE41 was comparatively reviewed with Alvarez DTL. This study shows that IH-DTL and CH-DTL have a larger shunt impedance than Alvarez DTL for proton acceleration below 10 MeV, and furthermore for the TEm1-mode structures, the rotational symmetry of the electric field improves with increasing angular index m.
Kondo, Yasuhiro; Kitamura, Ryo; Fuwa, Yasuhiro; Morishita, Takatoshi; Moriya, Katsuhiro; Takayanagi, Tomohiro; Otani, Masashi*; Cicek, E.*; Ego, Hiroyasu*; Fukao, Yoshinori*; et al.
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.636 - 641, 2022/09
The muon linac project for the precise measurement of the muon anomalous magnetic and electric dipole moments, which is currently one of the hottest issues of the elementary particle physics, is in progress at J-PARC. The muons from the J-PARC muon facility are once cooled to room temperature, then accelerated up to 212 MeV with a normalized emittance of 1.5 
mm mrad and a momentum spread of 0.1%. Four types of accelerating structures are adopted to obtain the efficient acceleration with a wide beta range from 0.01 to 0.94. The project is moving into the construction phase. We already demonstrated the re-acceleration scheme of the decelerated muons using a 324-MHz RFQ in 2017. The high-power test of the 324-MHz Interdigital H-mode (IH) DTL using a prototype cavity was performed in 2021. The fabrication of the first module of 14 modules of the 1296-MHz Disk and Washer (DAW) CCL will be done to confirm the production process. Moreover, the final design of the travelling wave accelerating structure for the high beta region is also proceeding. In this paper, the recent progress toward the realization of the world first muon linac will be presented.
