JLab, Newport News, Virginia, USA
Northern Illinois University, DeKalb, Illinois, USA
DESY, Hamburg, Germany
SLAC, Menlo Park, California, USA
ODU, Norfolk, Virginia, USA
JINR, Dubna, Russia
Texas A&M University, College Station, Texas, USA
Old Dominion University, Norfolk, Virginia, USA
Science and Technique Laboratory Zaryad, Novosibirsk, Russia
ANL, Argonne, Illinois, USA
The Medium-energy Electron Ion Collider (MEIC) at JLab is designed to provide high luminosity and high polarization needed to reach new frontiers in the exploration of nuclear structure. The luminosity, exceeding 1033 cm-2s−1 in a broad range of the center-of-mass (CM) energy and maximum luminosity above 1034 cm-2s−1, is achieved by high-rate collisions of short small-emittance low-charge bunches made possible by high-energy electron cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3He) can be easily preserved and manipulated due to the unique figure-8 shape of the collider rings. A fully consistent set of parameters have been developed considering the balance of machine performance, required technical development and cost. This paper reports recent progress on the MEIC accelerator design including electron and ion complexes, integrated interaction region design, figure-8-ring-based electron and ion polarization schemes, RF/SRF systems and ERL-based high-energy electron cooling. Luminosity performance is also presented for the MEIC baseline design.
ANL, Argonne, Illinois, USA
A higher-harmonic cavity is planned for the proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice to increase the bunch length, improve the Touschek lifetime and increase the single-bunch current limit. We have investigated a range of options including 3rd, 4th, and 5th harmonics of the main radio frequency (RF) system, as well as configurations with and without external RF power couplers. The current baseline is a single 4th harmonic superconducting cavity with adjustable RF couplers and a slow tuner which provide the flexibility to operate over a wide range of beam currents. The cavity is designed to provide 0.84 MV at 1408 MHz for the nominal 6 GeV, 200 mA electron beam, and 4.1 MV main RF voltage. In this paper, we discuss the harmonic cavity parameters based on analytical calculations of the equilibrium bunch distribution and make comparisons to other options.
ANL, Argonne, Illinois, USA
AES, Medford, New York, USA
ANL, Argonne, Illinois, USA
The Proton Improvement Plan II at FNAL relies upon a 162.5 MHz superconducting half-wave resonator cryomodule to accelerate H− beams from 2.1 to 10 MeV. This cryomodule contains 8 resonators with 8 superconducting solenoid magnets interspersed between them. X-Y steering coils are integrated with a package of the superconducting solenoid magnets. The center of the solenoids is located within ~50 cm of the high surface magnetic field of the half-wave resonators and in this study we assess whether or not magnetic flux generated by this magnet is trapped into the half-wave resonators niobium surface and increases the RF losses to liquid helium. To test this we assembled a solenoid with a 162.5 MHz half-wave resonator spaced as they will be in the cryomodule. We measured the quality factor of the cavity before and after the cavity quenched as a function of field level in the coils. No measurable change in the quality factor was observed. In this paper, we will present details of the measurements and discuss the magnetic field map.
ANL, Argonne, USA
ANL, Argonne, Illinois, USA
An Electron Beam Ion Source charge breeder (EBIS-CB) has been developed to breed CARIBU radioactive beams at ATLAS and is in the final stages of off-line commissioning. Within the next year, the EBIS-CB will replace the existing ECR charge breeder to increase the intensity and improve the purity of reaccelerated radioactive ion beams. Integration of the new EBIS-CB requires: a. Building a compact fully electrostatic low energy beam transport line (LEBT) from CARIBU to the EBIS-CB that satisfies the spatial constraints and ensures the successful ion seeding into the EBIS trap. b. Modifications to the existing ATLAS LEBT to purify the EBIS beams by q/A selection and accommodate the injection of the charge bred ions into ATLAS. In this paper, we will describe the beam line design and present beam dynamics simulation results.
ANL, Argonne, Illinois, USA
Illinois Institute of Technology, Chicago, Illlinois, USA
In 2015 an electron beam ion source (EBIS) will be installed at the ATLAS facility to charge breed radioactive beams from the Californium Rare Isotope Breeder Upgrade (CARIBU). Currently an ECR ion source is used to charge breed CARIBU beams. The EBIS will provide beams with much less contamination and higher breeding efficiencies. In preparation for its installation at ATLAS the EBIS has been successfully commissioned offline. The EBIS was configured in the offline facility to closely mimic the conditions expected in the ATLAS installation, so commissioning results should be representative of its performance with CARIBU. The EBIS breeding efficiency was tested with pulses of 133Cs1+ from a surface ionization source, and for multiple operational modes maximum breeding efficiencies greater than 25% could be achieved. After transmission losses the total efficiency of the system was 15-20%. The contaminants were expectedly very low for a UHV system with nominal pressures of ~1 – 3 x 10-10 Torr.
ANL, Argonne, Illinois, USA
Substantial research and development related to CW proton and ion accelerators are being performed at ANL. A normal conducting CW RFQ and a 4K cryomodule with seven quarter-wave resonators (QWR) and SC solenoids have been developed, built, commissioned and operated as an upgrade of the CW ion linac, ATLAS, to achieve higher efficiency and beam intensities. The new CW RFQ and cryomodule were fully integrated into ATLAS and have been in routine operation for more than a year. Currently we are engaged in development of the first cryomodule for a CW H linac being built at FNAL. This work is well aligned with the development of a 1 GeV 25 MW linac as the driver of a sub-critical assembly for near-term spent nuclear fuel disposal. A 2K cryomodule with eight 162.5-MHz SC half wave resonators (HWR) and eight SC solenoids is being developed for FNAL and scheduled for commissioning in 2017. The testing of the first 2 HWRs demonstrated remarkable performance. Experience with the development and reliable operation of new copper and superconducting accelerating structures is an essential precursor for advanced, reliable future large scale high power CW accelerators.