The ISAC post-accelerator
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The ISAC post-accelerator R. E. Laxdal · M. Marchetto
Published online: 13 November 2013 © Springer Science+Business Media Dordrecht 2013
Abstract The acceleration chain of the ISAC facility boosts the energy of both radioactive and stable light and heavy ions for beam delivery to both a medium energy area in ISAC-I and a high energy area in ISAC-II. The post-accelerator comprises a 35.4 MHz RFQ to accelerate beams of A/q ≤ 30 from 2 keV/u to 150 keV/u and a post stripper, 106.1 MHz variable energy drift tube linac (DTL) to accelerate ions of A/q ≤ 6 to a final energy between 0.15 MeV/u to 1.5 MeV/u. A 40 MV superconducting linac further accelerates beam from 1.5 MeV/u to energies above the Coulomb barrier. All linacs operate cw to preserve beam intensity. Keywords ISAC · ISAC-I · ISAC-II · pre-buncher · RFQ · Chopper · Stripping foil · DTL · Superconducting linac · Post accelerator
1 Introduction In the ISAC-I facility 500 MeV protons from the cyclotron at up to 100 μA impinge on one of two production targets to produce radioactive isotopes [1, 2]. The isotopes migrate in a short heated tube to an adjoining source where they are ionized and accelerated off the biased platform. Typical source geometries include a surface source and a FEBIAD source while laser ionization is used to enhance ionization of certain species. The resulting beam is mass-separated and transported in the low energy beam transport (LEBT) electrostatic beamline to either the low energy experimental area or through a series of room temperature accelerating structures (RFQ, DTL) to the ISAC-I medium energy experimental area [3]. The 35.4 MHz RFQ accelerates ions with 3 ≤ A/q ≤ 30 from 2 keV/u to 150 keV/u and the 106.1 MHz
ISAC and ARIEL: The TRIUMF Radioactive Beam Facilities and the Scientific Program. R. E. Laxdal (B) · M. Marchetto Accelerator Division, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada e-mail: [email protected]
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R.E. Laxdal, M. Marchetto
Fig. 1 Overview of the ISAC facility at TRIUMF. The ISAC II linac is superconducting while in ISAC I the RFQ and the DTL are room temperature accelerators
DTL accelerates ions with A/q ≤ 6 to energies fully variable from 117 keV/u to 1.8 MeV/u. To reduce the required acceleration voltage the charge state of the ions is increased by passing the beam through a thin carbon foil in the medium energy beam transport (MEBT) between the RFQ and the DTL. The accelerated beam can also be transported to the ISAC-II 40 MV Superconducting Linear Accelerator (SC-linac) for acceleration above the Coulomb barrier and delivered to the ISAC-II high energy area. The ISAC electron cyclotron resonance (ECR) charge breeder [4], CSB1, installed downstream of the ISAC mass-separator, is used to boost the charge state of masses with A > 30 to allow acceleration in the RFQ. The accelerator chain is shown in Fig. 1. The eight meter long RFQ structure [5] (Fig. 2) is composed of nineteen split ring resonators supporting the four electrodes.The RFQ does not have a bunching section; the beam is pre-bunched a
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