From roth et al 2001 fast ignition by

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Unformatted text preview: f their higher stopping power with respect to protons. Calculations by Honrubia et al. (2009) showed that, different from the proton-based scheme, ions with a narrow energy spread E =E would allow one to lower the ignition threshold: for E =E ¼ 0:1, E ig < 10 kJ might be obtained. This feature might also relieve the need to place the ion producing foil in ´ a reentrant cone, yielding a simpler target design (Fernandez et al., 2009). The estimated parameters for a C ignitor beam are 400–500 MeV energy per ion, * 10% efficiency, and E =E < 0:2. To achieve such values, mechanisms such as RPA (see Sec. IV.A) or BOA (see Sec. IV.C) might be more suitable than TNSA. Progress in related research was recently reported by Hegelich et al. (2011), where separate experiments approaching the three above mentioned requirements are described. A fourth and so far unexplored issue might be the need to focus the ion beam. Another approach (Naumova et al., 2009) to ion-driven FI is based on RPA in the hole boring regime (see Sec. IV.A.1). In such a scheme, different from the above described ones, ion acceleration occurs in situ by direct interaction of an ultraintense, circularly polarized laser with the corona of the fusion plasma. Tikhonchuk et al. (2010) reported calculations with this scheme, assuming direct acceleration of deuterons and characterizing possible high gain regimes with E ig ’ 12–17 kJ. This corresponds to an overall ignition energy >100 kJ and a required laser intensity exceeding 1022 W cmÀ2 . FI by laser-accelerated ions was investigated theoretically in several other works.27 Integrated FI studies, on the route to ignition-class experiments, could be performed in either the electron or the ion approach in 27 See, e.g., Shmatov (2003, 2008, 2011), Barriga-Carrasco, Maynard, and Kurilenkov (2004), Ramis and Ramrez (2004), Hosseini Motlagh, Mohamadi, and Shamsi (2008), and Badziak et al. (2011). Rev. Mod. Phys., Vol. 85, No. 2, April–June 2013 Hadron therapy is the radiotherapy technique that uses protons, neutrons, or carbon ions to irradiate cancer tumors. The use of ion beams in cancer radiotherapy28 exploits the advantageous energy deposition properties of ions as compared to more commonly used x rays (see Fig. 3): the range for a proton or ion is fixed by its energy, which avoids irradiation of healthy tissues at the rear side of the tumor, while the well-localized Bragg peak leads to a substantial increase of the irradiation dose in the vicinity of the stopping point. The proton energy window of therapeutical interest ranges between 60 and 250 MeV, depending on the location of the tumor (the required carbon ion range extends up to 400 MeV=nucleon). The typical dose of a treatment session is in the 1–5 gray range, and typical currents are 10 nA for protons and 1.2 nA for singly charged carbon ions. Ion beam therapy has proven to be effective and advantageous in a number of tumors and several clinical facilities, empl...
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This document was uploaded on 09/28/2013.

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