MW-CLASS 800 MeV / n H 2 SC-CYCLOTRON FOR ADS APPLICATION , DESIGN STUDY AND GOALS

This paper addresses an attempt to start investigating the use of the Superconducting Ring Cyclotron (SRC) developed for DAEδALUS experiment for ADS application [1, 2], focusing on the magnet design and its implication for lattice parameters and dynamic aperture performance. INTRODUCTION Accelerator Driven Sub-critical (ADS) fission is a promising candidate basis for nuclear waste transmutation and for nuclear power generation. ADS can use Thorium or depleted Uranium as fuel, operate below criticality, and consume rather than produce long-lived actinides. ADS systems offer several interesting advantages in comparison to traditional critical reactors : 1. ADS provides greater flexibility for the composition and placement of fissile, fertile, or fission product waste within the core, and require less enrichment of fissile content; 2. The core can be operated with a reactivity keff that cannot reach criticality by any failure mode. 3. Coupling the fast neutron spectrum of the spallation drive to fast core neutronics offers a basis for more complete burning of long-lived actinides. 4. ADS designs can provide sufficient thermal mass that meltdown cannot occur from radioactive heat after fission is stopped. Furthermore, if a liquid Thorium fuel is used, much less nuclear waste will be generated and the fuel can be recycled continuously without stoppage of the operation. A modular reactor capable of delivering few hundred MW of electrical power is considered to be one possible type of application of immediate use. In order to drive a ∼GWe fission core, a CW proton beam of >800 MeV and ∼15 MW beam power is sufficient. A previous study of the accelerator performance required for ADS systems [3] concluded that present accelerator performance is approaching those requirements, but accelerator system cost and reliability remain particular concerns. The obvious candidates that can provide intense CW proton beams are isochronous cyclotrons and superconducting linacs. The target system, reactor interface, neutronics performance, and reliability are also important concerns. At current technology level, a target system in the range of 3 to ∗Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Figure 1: Possible arrangement of a pair (out of a series) of 12.5 MW beam power sub-critical units, based on a 10 MW SRC and its two 60 MeV/amu injectors. In case of failure in a cyclotron, it is possible to increase the beam power from the others and maintain a total 12.5 MW per unit [1, 2]. Table 1: Parameters of the SRC. Ion type H 2 Ion mass MeV/c 1876.635 Injection-extraction energy MeV/amu 60.44− 800 Inj. -extr. Bρ T.m 2.283− 9.809 Bρxtr/Bρinj 4.2969 Inj. -extr. βγ 0.3647− 1.567 Injection-extraction radii m 1.99− 4.90 Orbit excursion m 2.935 Max. field on orbit, inj. -extr. T 4− 5.8 Lattice type spiral sector Spiral angle deg. < 12 Number of sectors 8 Qr range (min.-max.) 1.085− 1.927 Qz range (min.-max.) 0.486− 1.161 Number of RF cavities > 6 RF frequency MHz 49.2 Peak voltage MV 1 Energy gain per turn MeV 4.6 5 MW can be developed in few years time for deployment in an ADS facility. Our previous study [4] indicates that a configuration consisting of 3∼5 high power cyclotrons and associated target systems can best meet the requirement of a medium size power generation facility. The present paper addresses an attempt to start investigating the use of the cyclotron developed for DAEδALUS experiment for ADS application, focusing on the magnet design and its implication for lattice parameters and dynamic aperture performance. The Multi-MegaWatt Superconducting Ring Cyclotron (SRC), which has to supply the few MW beam for the DAEδALUS experiment, is shown in Fig. 1. Preliminary parameters are presented in table 1. Proceedings of IPAC2012, New Orleans, Louisiana, USA THPPR064 08 Applications of Accelerators, Technology Transfer and Industrial Relations U03 Transmutation and Energy Production ISBN 978-3-95450-115-1 4121 C op yr ig ht c ○ 20 12 by IE E E – cc C re at iv e C om m on sA tt ri bu tio n 3. 0 (C C B Y 3. 0) — cc C re at iv e C om m on sA tt ri bu tio n 3. 0 (C C B Y 3. 0) The cyclotron complex consists of an injector cyclotron, which accelerates molecular H 2 from injection energy 50 keV/amu about, up to 60 MeV/amu. Raising the injector energy to 80∼120 MeV/amu according to DAEδALUS concerns is now in discussion. The beam is then injected into the SRC along a valley, by one or more superconducting injector magnets and one electrostatic deflector, and accelerated up to 800 MeV/amu by means of a series of 6 RF cavities, 4 single-gap and 2 double-gap. The extraction is performed by insertion of a pyrolytic graphite stripper foil with thickness less than 2 mg/cm. It is possible to use one or two stripper foils depending on the power limitations of the beam dump. -. 2 0.0 0.2 0.4 2. 2.5 3. 3.5 4. 4.5 5. r (m) vs. angle (rad) E = 120.88 MeV 214.06 353.82 571.24 943.95 1611.720 Figure 2: Closed orbits across one of the eight cells of the cyclotron, at six different energies. -. 2 0.0 0.2 0.4 -1 0 1 2 3 4 5 6 Bz (T) vs. Angle (rd) 120.88 MeV 1611.72 MeV Figure 3: Field on closed orbits across a cell, featuring ”shimming” bumps. 0.975 0.9755 0.976 0.9765 0.977 0.9775 0.978 0.9785 0.979 0 200 400 600 80