Synchrotron-based high-pressure research in materials science Page: 3 of 8
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2.3.2 Ionization Cooling
As part of the International Scoping Study of a Neutrino Factory , the performance of the various
cooling channel designs was compared. As a result of that comparison, the so-called "Feasibility
Study 2" (FS2) channel  was found to perform the best. When coupled with a proton driver
providing 4 MW of 5-15 GeV protons (in 2 ns bunches), this channel, illustrated schematically in Fig.
2, meets the requirement of 102 useful muon decays per 107 s year. The channel transmits both muon
signs simultaneously, interleaved at different phases of the 201-MHz rf system. It is worth noting that
the actual implementation of such a channel, such as that being built for the Muon Ionization Cooling
Experiment (MICE) , is considerably more complicated than the simple "physicist's view"
illustrated in Fig. 2.
The baseline scheme adopted for the IDS-NF (see Fig. 3) comprises a pre-acceleration linac that
increases the beam energy to 0.9 GeV. This is followed by a pair of "dog-bone" Recirculating Linear
Accelerators (RLAs) that raise the energy from 0.9-3.6 GeV and from 3.6-12.6 GeV, respectively.
The last stage of acceleration, from 12.6-25 GeV, is provided by a non-scaling Fixed-Field,
Alternating Gradient (FFAG) ring. Optics for the linac, the RLAs, the required injection chicanes, and
the transfer lines have been completed .
The last system, the non-scaling FFAG ring, presents several technical challenges. First, there is
a strong coupling between the longitudinal and transverse dynamics that is important for the emittance
values of interest to a muon FFAG. Different amplitude particles have different flight paths and thus
different flight times. The result is that large-amplitude particles slip out of phase with the rf and are
not fully accelerated. Using sextupoles to effect a partial chromatic correction has been shown  to
ameliorate the problem and appears workable.
The second challenge concerns injection and extraction into the densely packed FFAG ring.
Progress on this topic has recently been reported by Pasternack , though the kicker and septum
magnet specifications remain daunting.
SC 106 A/mm2
Lii 201.25 MH-
I I I
0 25 50 100 125 150 cm
Fig. 2: Schematic of FS2 cooling channel.
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Chen, Bin; Lin, Jung-Fu; Chen, Jiuhua; Zhang, Hengzhong & Zeng, Qiaoshi. Synchrotron-based high-pressure research in materials science, article, June 1, 2016; (digital.library.unt.edu/ark:/67531/metadc932011/m1/3/: accessed September 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.