MSU/NSCL, East Lansing
The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is currently constructing its new reaccelerated beam facility- ReA3. ReA3 will provide world-unique low energy rare isotope beams by stopping fast, separated rare isotopes in a gas-stopper, and then reaccelerating them in a Linear Accelerator. ReA3 will provide pioneering beams for research in one of the pillars of the next-generation rare isotope facility FRIB that will be hosted at MSU. The main components of ReA3 are a linear cryogenic gas cell to stop the fast beams produced by the existing coupled cyclotron facility, an Electron Beam Ion Trap (EBIT) to boost their charge states, a compact accelerator using a room temperature RFQ and a superconducting linac, and an achromatic beam transport line for delivery to the new experimental area. Beams from ReA3 will range in energy from 0.3 to 6 MeV/u. The maximum energy is 3 MeV/u for heavy nuclei such as uranium, and 6 MeV/u for ions with A<50. The overall design for ReA3 will be presented emphasizing on the ongoing construction and tests of its various components.
Goethe Universität Frankfurt/IAP, Frankfurt
MSU/NSCL, East Lansing
ECR and EBIS have become well-known ion sources for most heavy ion accelerator projects. The basic difference arises from the method, how energy is provided to create dense energetic electrons: An ECR uses microwave heating of a magnetically confined plasma, while in an EBIS the energy comes from a power supply to accelerate an electron beam and focus it to high density in a strong solenoidal magnetic field. Basically ECR sources are dc sources of heavy ions but the afterglow extraction also provides intense mA pulses in ms. In contrast to this EBIS sources provide an intense ion pulse in 1-100 μs and therefore find application in feeding synchrotrons. This determines most of the accelerator applications: ECR sources have very successfully extended the range (and life) of cyclotrons, while EBIS has found application at high energy facilities. For radioactive beam facilities, both kind of sources are in use. ECR sources in the trapping mode (ECRIT) perform the ionization (charge breeding) of high intensity primary beams, while EBIS can reach higher charge states at lower emittance, which provides an improved signal to noise ratio for rare isotopes.
MSU/NSCL, East Lansing
GSI, Darmstadt
Goethe Universität Frankfurt/IAP, Frankfurt
Funding: Work supported by the BMBF.
The GSI accelerator facility provides highly charged ion beams up to U92+ at the energy of 400 MeV/u. These are cooled and decelerated down to 4 MeV/u in the Experimental Storage Ring. Within the Heavy Ion Trap facility HITRAP the ions are decelerated further down. The linear decelerator comprises a 108/216 MHz doubledrift- buncher, a 108 MHz-IH-structure, a spiral-type rebuncher, and an RFQ-decelerator with an integrated debuncher providing energy spread reduction. Finally the beam is injected with the energy of 6 keV/u into a Penning trap for final cooling. The decelerator is installed completely and first sections have been successfully commissioned. For commissioning of the individual sections different ion species, e.g. 64Ni28+, 20Ne10+, 197Au79+ were used. Each section was studied with comprehensive beam diagnostics to measure energy, emittance, intensity, transverse profiles, and bunch structure of the beam. The report gives an overview of the beam dynamics, the decelerator structures, and some results of the different commissioning runs.