J.A. Nolen

The super-FRS project at GSI

The GSI projectile fragment separator FRS has demonstrated with many pioneering experiments the research potential of in-flight separators at relativistic energies. Although the present facility has contributed much to the progress in the field of nuclear structure physics, major improvements are desirable in the future. The characteristics of the proposed next-generation facility at GSI, the Super-FRS, will be presented and compared to other projects. The Super-FRS is a large-acceptance superconducting fragment separator followed by different experimental branches including a combination with a new storage-cooler ring system. This system consists of a collector ring (CR) and a new experimental storage ring (NESR) which allow precision mass and lifetime measurements as well as in-ring reaction studies. The NESR can be operated in combination with an electron ring to measure electron scattering with exotic nuclei. This electron heavy-ion collider will open up new fields for nuclear structure research.

Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identi...

Identification of New Isotopes 125 Pd and 126 Pd produced by In-flight Fission of 345 MeV/nucleon 238 U: First Results from the RIKEN RI Beam Factory

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out in the commissioning experiment of the next-generation in-flight radioactive isotope beam separator BigRIPS at the RI Beam Factory at the RIKEN Nishina Center. Two neutron-rich palladium isotopes 125 Pd and 126 Pd were observed for the first time, which demonstrates the great potential of the RIKEN RI beam factory.

The A1200 projectile fragment separator

Abstract A beam analysis device, the A1200, has been constructed at the National Superconducting Cyclotron Laboratory (NSCL) for routine cyclotron beam analysis. This device can also be used to separate radioactive beams produced by projectile fragmentation. Since the A1200 begins the K1200 cyclotron beam lines, radioactive ions can be delivered to any experimental device. The details of the mechanical and optical designs are presented. In addition some of the planned experiments with the separated radioactive beams are discussed.

Multiple-charge beam dynamics in an ion linac

There is demand for the construction of a medium-energy ion linear accelerator based on superconducting rf (SRF) technology. It must be capable of producing several hundred kilowatts of CW beams ranging from protons to uranium. A considerable amount of power is required in order to generate intense beams of rare isotopes for subsequent acceleration. At present, however, the beam power available for the heavier ions would be limited by ion source performance. To overcome this limit, we have studied the possibility of accelerating multiple-charge-state (multi-Q) beams through a linac. We show that such operation is made feasible by the large transverse and longitudinal acceptance which can be obtained in a linac using superconducting cavities. Multi-Q operation provides not only a substantial increase in beam current, but also enables the use of two strippers, thus reducing the size of linac required. Since the superconducting (SC) linac operates in CW mode, space charge effects are essentially eliminated except in the ECR/RFQ region. Therefore an effective emittance growth due to the multi-charge beam acceleration can be minimized.

Production of radioactive ion beams using the in-flight technique

Reactions with a heavy projectile incident on a light target can be used for the efficient in-flight production of secondary radioactive beams. An overview of this technique is given using data on 17F beams produced via the p(17O, 17F)n and d(16O, 17F)n reactions. With primary 16,17O beam currents of 100 pnA, intensities of up to 2×106 17F/s on target were achieved. Using this beam, the p(17F,α)14O reaction was measured.

Ion plasma sputtering as a method of introducing solid material into an electron cyclotron resonance ion source

A direct ion plasma sputtering effect has been observed in an electron cyclotron resonance ion source and developed into a reliable and simple method for producing ion beams from some solid materials. We describe the ion sputtering technique used with the Argonne Tandem Linac Accelerator System Positive Ion Injector Electron Cyclotron Resonance ion source to produce, to date, stable beams of nickel, silver, tellurium, gold, lead, and bismuth and present the results obtained in test cases.

The neutron radius of 208Pb

Abstract A simple method is presented for calculating the radius of the neutron distribution of a nucleus from the energy of the isobaric analog state and the charge radius. The r.m.s. radius of the neutron distribution of 208Pb is calculated using the experimentally determined r.m.s. charge radius of 5.51 fm and the Coulomb displacement energy of 18.98 MeV. An r.m.s. neutron radius larger than the proton radius by 0.07 ± 0.03 fm is obtained.

Atomic layer deposition of W on nanoporous carbon aerogels

In this study, the authors demonstrate the ability to apply precise, conformal W coatings onto all surfaces of nanoporous carbon aerogels using atomic layer deposition (ALD). The resulting material has a filamentous structure in which the W completely encapsulates the carbon aerogel strands. The material mass increases nonlinearly with W coating, achieving a tenfold increase following ten ALD cycles. The aerogel surface area increases by nearly a factor of 2 after ten W ALD cycles. This conformal metal coating of extremely high aspect ratio nanoporous materials by ALD represents a unique route to forming metal functionalized high surface area materials.

Initial operating experience with the A1200 fragment separator

Abstract A beam analysis device, the A1200, has been constructed at the National Superconducting Cyclotron Laboratory (NSCL) for routine cyclotron beam analysis, and separation of radioactive beams produced from projectile fragmentation. It has been in operation since October 1990. The A1200 begins the NSCL beamlines following the K1200 cyclotron, and hence can transport radioactive ions to any experimental device. Some details of the mechanical and optical designs are presented, along with a discussion of the initial operation.