Heavy-Ion Beam Acceleration of Two-Charge States from an Ecr Ion Source

This paper describes a design for the front end of a superconducting (SC) ion linac which can accept and simultaneously accelerate two charge states of uranium from an ECR ion source. This mode of operation increases the beam current available for the heaviest ions by a factor of two. We discuss the 12 MeV/u prestripper section of the Rare Isotope Accelerator (RIA) driver linac including the LEBT, RFQ, MEBT and SC sections, with a total voltage of 112 MV. The LEBT consists of two bunchers and electrostatic quadrupoles. The fundamental frequency of both bunchers is half of the RFQ frequency. The first buncher is a multiharmonic buncher, designed to accept more than 80% of each charge state and to form bunches of extremely low longitudinal emittance (rms emittance is lower than 0.2 keV/u nsec) at the output of the RFQ. The second buncher is located directly in front of the RFQ and matches the velocity of each charge-state bunch to the design input velocity of the RFQ. We present full 3D simulations of a two-charge-state uranium beam including space charge forces in the LEBT and RFQ, realistic distributions of all electric and magnetic fields along the whole prestripper linac, and the effects of errors, evaluated for several design options for the prestripper linac. The results indicate that it is possible to accelerate two charge states while keeping emittance growth within tolerable limits.Comment: LINAC2000, MOD0

Multiplicities of secondaries in interactions of 1.8 GeV/nucleon Fe-56 nuclei with photoemulsion and the cascade evaporation model

A nuclear photographic emulsion method was used to study the charge-state, ionization, and angular characteristics of secondaries produced in inelastic interactions of Fe-56 nuclei at 1.8 GeV/nucleon with H, CNO, and AgBr nuclei. The data obtained are compared with the results of calculations made in terms of the Dubna version of the cascade evaporation model (DCM). The DCM has been shown to satisfactorily describe most of the interaction characteristics for two nuclei in the studied reactions. At the same time, quantitative differences are observed in some cases

Target fragments in collisions of 1.8 GeV/nucleon Fe-56 nuclei with photoemulsion nuclei, and the cascade-evaporation model

Nuclear photographic emulsion is used to study the dependence of the characteristics of target-nucleus fragments on the masses and impact parameters of interacting nuclei. The data obtained are compared in all details with the calculation results made in terms of the Dubna version of the cascade-evaporation model (DCM)

Long-Wave Instability of Advective Flows in Inclined Layer with Solid Heat Conductive Boundaries

We investigate the stability of the steady convective flow in a plane tilted layer with ideal thermal conductivity of solid boundaries in the presence of uniform longitudinal temperature gradient. Analytically found the stability boundary with respect to the long-wave perturbations, find the critical Grashof number for the most dangerous among them of even spiral perturbation.Comment: in Russian, 18 pages, 5 figures, submited to Appl. mechanics and physics, RAS Siberian brunch, Novosibirsk, Russia; Key words: advective flow, oblique layer, a longitudinal temperature gradient, long-wave instabilit

Advanced surface treatments for medium-velocity superconducting RF cavities for high accelerating gradient continuous-wave operation

Nitrogen-doping and furnace-baking are advanced high-Q0 recipes developed for 1.3 GHz TESLA-type cavities. These treatments will significantly benefit the high-Q0 linear accelerator community if they can be successfully adapted to different cavity styles and frequencies. Strong frequency- and geometry- dependence of these recipes makes the technology transfer amongst different cavity styles and frequencies far from straightforward, and requires rigorous study. Upcoming high-Q0 continuous-wave linear accelerator projects, such as the proposed Michigan State University Facility for Rare Isotope Beam Energy Upgrade, and the underway Fermilab's Proton Improvement Plan-II, could benefit enormously from adapting these techniques to their beta_opt = 0.6 ~650 MHz 5-cell elliptical superconducting rf cavities, operating at an accelerating gradient of around ~17 MV/m. This is the first investigation of the adaptation of nitrogen doping and medium temperature furnace baking to prototype 644 MHz beta_opt = 0.65 cavities, with the aim of demonstrating the high-Q0 potential of these recipes in these novel cavities for future optimization as part of the FRIB400 project R&D. We find that nitrogen-doping delivers superior Q0, despite the sub-GHz operating frequency of these cavities, but is sensitive to the post-doping electropolishing removal step and experiences elevated residual resistance. Medium temperature furnace baking delivers reasonable performance with decreased residual resistance compared to the nitrogen doped cavity, but may require further recipe refinement. The gradient requirement for the FRIB400 upgrade project is comfortably achieved by both recipes.Comment: 16 pages, 5 figure

CERN PS laser ion source development

CERN, together with ITEP and TRINITI (Russia), is developing a CO2 laser ion source. The key design parameters are: 1.4 1010 ions of Pb25+ in a pulse of 5.5 ms, with a 4-rms emittance of 0.2 10-6 rad m, working at a repetition rate of 1 Hz. This device is considered as one candidate source for LHC heavy ion operation. The status of the laser development, the experimental set-up of the source consisting of the target area and its illumination, the plasma expansion area and extraction, beam transport and ion pre-acceleration by an RFQ, will be given

Science Requirements and Conceptual Design for a Polarized Medium Energy Electron-Ion Collider at Jefferson Lab

This report presents a brief summary of the science opportunities and program of a polarized medium energy electron-ion collider at Jefferson Lab and a comprehensive description of the conceptual design of such a collider based on the CEBAF electron accelerator facility.Comment: 160 pages, ~93 figures This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC05-06OR23177, DE-AC02-06CH11357, DE-AC05-060R23177, and DESC0005823. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purpose