Search

A five-cell high current superconducting cavity for the electron cooling project at RHIC has been designed. The 703.75 MHz cavity and cryomodule is under fabrication and nearing completion. The different components of the cryomodule and the status of their fabrication is discussed.

We report detailed investigations of ion charge state enhancement in an alternative metal-vapor-vacuum arc ion source configuration, consisting of two anodes with staggered (but partially overlapping) high current discharges in axial high magnetic field gradients. The experiments demonstrated that driving an additional current in a vacuum arc in a magnetic mirror configuration resulted in substantial ion charge state enhancement. Maximum ion charge states of Pb 6+ and U 8+ were extracted. Results are presented for high charge state uranium beam generation and acceleration in the 27 MHz heavy-ion RFQ LINAC TIPr-1.

A prototype detector for a high resolution electromagnetic calorimeter for the PHENIX experiment at RHIC has been built and tested. The detector consists of a 6 × 5 array of undoped cesium iodide crystals read out with photomultiplier tubes or vacuum phototetrodes. The response for electrons and pions was measured in the momentum range from 50 MeV/ c to 4 GeV/ c in several beam tests at Brookhaven and TRIUMF. The energy resolution for electrons can be parameterized as σ ( E )/ E = 1.8%/√ E ⊕ 0.3%/ E ⊕ 0.8%, where E is in GeV, and the position resolution as σ x (mm) = 4.7/√ E + 0.5. The π/e separation was determined to be in the range from 10 −2 at 100 MeV/ c to a few times 10 −3 at 4 GeV/ c . The time resolution was measured to be 127 ps for 150 MeV/ c electrons after correcting for start counter timing. A laser calibration system is also described, along with the expected performance of the detector in the high multiplicity environment anticipated for relativistic heavy ion collisions at RHIC.

A new ground state source of negative hydrogen ions with polarized nuclei (H−) has been studied at BNL. Extensive developmental research has been aimed at improving each element of H− production: cold H0 beam, spin selection and focusing magnets, and ionizer. These elements have recently been integrated into a source. The performance of each individual element was extremely encouraging. However, larger than expected gas scattering problems arose as elements were being combined. These scattering problems suggest that improvements to ground state polarized sources by cooling the atomic beam may have reached a regime of diminishing returns.

Analysis of the effects of electron backscattering off an EBIS collector surface is presented. Results show that electron backscattering is a much more severe problem than secondary electrons. These electrons can accumulate in an EBIS collector and can eventually re-enter an EBIS. To our knowledge, this is the first time that electron backscattering problems in an EBIS have been considered.

A novel method for production of nuclear polarized negative hydrogen ions by selective neutralization with a laser of negative hydrogen ions in a magnetic field is described. This selectivity is possible since a final state of the neutralized atom, and hence the neutralization energy, depends on its nuclear polarization. Limiting factors are discussed. The main advantages of this scheme are the availability of multiampere negative ion sources and the possibility of neutralizing negative ions with very high efficiency. Possible schemes to implement this method are discussed. An assessment of the required laser power indicates that this method is in principle feasible with today's technology.