Development of a proton accelerator for the JAERI Neutron Science Project

Akaoka, N.; Chishiro, E.; Hasegawa, K.; Ichihara, Masahiro; Ikegami, Machiko; Ito, Taku; Kinsho, Michikazu; Kusano, Joichi; Minehara, Eisuke; Mizumoto, M.; Mukugi, K.; Noda, F.; Oguri, H.; Ouchi, Nobuo; Sawada, J.; Takeda, Osamu; Tomisawa, T.; Yokomizo, H.

doi:10.1109/pac.1999.792365

Cited by 1 publication

(1 citation statement)

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“…The fabrication of a bulk-Nb cavity generally begins with the deep-drawing of a plate of pure Nb (RRR 200-300) to form 'half-cells' which are then machined (trimmed), assembled into multicell cavities by EB welding, and carefully surface treated, e.g. [4,12], see also section 4.2. To avoid the EB welding step DESY has investigated the fabrication of seamless bulk Nb cavities by the hydroforming of seamless spun-and deep-drawn Nb tubes [13].…”

Section: Srf Cavity Materials and Fabricationmentioning

confidence: 99%

Magnesium diboride superconducting RF resonant cavities for high energy particle acceleration

Collings

Sumption

Tajima

2004

Supercond. Sci. Technol.

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Arguments in support of any particular superconducting coating must be framed in terms of its fundamental thermodynamic properties. The superconducting transition temperature, Tc, determines the surface resistance, and thus the Q of the cavity. This must remain sufficiently high that the system can be driven at the required field gradients and frequencies without leading to excessive power loss. In this regard the 39 K Tc of MgB2 is advantageous. With an anticipated maximum accelerating field, EaccMAX, of 77 MV m−1 and a BCS surface resistance, RsBCS (4 K, 500 MHz), of 2.5 n Ω as discussed later, MgB2 represents an interesting possibility as a coating for SRF cavities. In addition, the higher Hc2 of MgB2 than Nb results in a slightly lower estimated trapped flux sensitivity. Recent measurements of an MgB2 film at the Los Alamos National Laboratory (LANL) have shown an RF surface resistance lower than that of Nb at 4 K, which is proof-of-principle evidence of the attractiveness of MgB2. Our calculations are based conservatively on 4 K operation at 500 MHz. However, with a Tc of 39 K, MgB2-coated cavities should be less susceptible to thermal breakdown than low-Tc ones. Superconducting materials for use at GHz frequencies at voltage gradients >40 MV m−1, a recently cited target, will require both low Rs (high Tc) and high Hsh values. With a Tc of 39 K, MgB2 clearly has the potential to reduce RsBCS if the films are well prepared and free from defects and particles. Additionally, while the Hc1 for MgB2 is relatively low, the superheating critical field, Hsh, is higher than that of Nb. Currently, there is some debate about the exact roles of Hc1 and Hsh in the determination of Eacc limits. However, the higher values of Hsh for MgB2 do suggest the possibility of enhanced Eacc values. The exact roles of Hc1 and Hsh should be further investigated. Techniques exist that may enable cavity-like structures to be internally coated with a MgB2 film.

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Section: Srf Cavity Materials and Fabricationmentioning

confidence: 99%