INFN/LNL, Legnaro (PD), Italy
FRIB, East Lansing, Michigan, USA
JLAB, Newport News, Virginia, USA
The superconducting driver and post-accelerator linacs of the FRIB project, the large scale radioactive beam facility under construction at MSU, require the construction of about 400 low-beta Quarter-wave (QWR) and Half-wave resonators (HWR) with four different optimum velocities. 1st and 2nd generation prototypes of β=0.041 and 0.085 QWRs and β=0.53 HWRs have been built and tested, and have more than fulfilled the FRIB and ReA design goals. The present cavity surface preparation at MSU allowed production of low-beta cavities nearly free from field emission. The first two cryostats of β=0.041 QWRs are now in operation in the ReA3 linac. A 3rd generation design of the FRIB resonators allowed to further improve the cavity parameters, reducing the peak magnetic field in operation and increasing the possible operation gradient , with consequent reduction of the number of required resonators. The construction of the cavities for FRIB, which includes three phases for each cavity type (development, pre-production and production runs) has started. Cavity design, construction, treatment and performance will be described and discussed.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.
INFN/LNL, Legnaro (PD), Italy
FRIB, East Lansing, Michigan, USA
The Quarter-Wave Resonators (QWR) section of the FRIB superconducting driver linac is required to accelerate Uranium beam up to 16 MeV/u in two different charge states simultaneously. This puts severe requirements on resonators alignment and field quality, in order to avoid beam losses and emittance growth. In particular, QWR beam steering can cause transverse oscillations of the beam centroid which reduce the linac acceptance and induces emittance growth. We have studied, with an analytical model and with 3D beam dynamics simulations, correction methods for the FRIB QWRs steering. We found that cavity shifting can provide effective steering cancellation in FRIB QWRs without need of cavity shape modifications, and allows to eliminate transverse beam oscillations and to improve beam quality. Calculation and simulation methods and results will be presented and discussed.
Michigan State University designs and establishes FRIB as a DOE Office of Science National User Facility in support of the mission of the Office of Nuclear Physics.
FRIB, East Lansing, Michigan, USA
NSCL, East Lansing, Michigan, USA
BNL, Upton, Long Island, New York, USA
SLAC, Menlo Park, California, USA
For a complex accelerator such as the Facility for Rare Isotope Beams (FRIB), a transfer matrix based online model might not be sufficient for the entire machine. On the other hand, if introducing another modelling tools, physics applications have to be rewritten for all modelling tools. A platform which can host multiple modelling tools would be ideal for such scenario. Furthermore, the model platform along with infrastructure support can be used not only for online applications but also for offline purposes with multi-particle tracking simulation. In order to achieve such a platform, a set of common physics data structures has to be set. XAL's accelerator hierarchy based data structure is a good choice as the common structure for various models. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype is discussed.
IUCF, Bloomington, Indiana, USA
FRIB, East Lansing, USA
Unlike the high energy proton machines, our radiation transport simulation results show that it will be difficult to use traditional BLMs to detect beam losses for FRIB linac, not only due to the low radiation levels from low energy heavy ion beams, but also resulted by the cross talk effect from one part of the machine to another in the folded machine geometry. A device called “Halo Ring” is introduced as a component of the BLM system to substitute the traditional ion chamber in those regions.
FRIB, East Lansing, Michigan, USA
The FRIB linac driver will deliver heavy ion beams up to uranium, with an energy of 200 MeV/u and total power on target of 400 kW. To reach the design power for heaviest ions, multi-charge-state beams will be accelerated simultaneously in this SRF linac. Beam tuning of the linac driver is among the most challenging tasks. In this paper, we discuss the beam tuning strategy, which includes the cavity synchronous phase and acceleration gradient setup, beam trajectory correction, and transverse matching with horizontal-vertical coupled beams as superconducting solenoids are used for transverse focusing in the linac segments.
JLAB, Newport News, Virginia, USA
DESY, Hamburg, Germany
A key feature of the Medium-energy Electron-Ion Collider (MEIC) at Jefferson Lab is high polarization (over 80%) of the electron beam at all collision points for the particle physics program. The equilibrium electron polarization is arranged to be vertical in the arcs of the figure-8 collider ring of the MEIC and anti-parallel to the arc dipole magnetic fields, in order to take advantage of the preservation of polarization by the Sokolov-Ternov (S-T) effect. Longitudinal polarization is achieved at collision points by utilizing energy-independent universal spin rotators each of which consists of a set of solenoids and dipoles placed at the end of an arc. The equilibrium beam polarization and its lifetime depend on competition between the S-T effect and radiative depolarization. The latter must be suppressed by spin matching. This paper reports on investigations of polarization in the MEIC electron collider ring and a preliminary estimate of beam polarization from calculations using the code SLICK.
Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
JLAB, Newport News, Virginia, USA
Muons, Inc, Batavia, USA
The conceptual design of the Medium-energy Electron-Ion Collider (MEIC) at Jefferson Lab relies on an ultra-small beta-star to achieve high luminosities of up to 1034 cm-2s−1. A low-beta insertion for interaction regions unavoidably induces large chromatic effects that demand a proper compensation. The present approach of chromatic compensation in the MEIC collider rings is based on a local correction scheme using two symmetric chromatic compensation blocks that includes families of sextupoles, and are placed in a beam extension area on both sides of a collision point. It can simultaneously compensate the first order chromaticity and chromatic beam smear at the IP without inducing significant second order aberrations. In this paper, we investigate both the momentum acceptance and dynamic aperture in the MEIC ion collider ring by considering the aberration effects up to the third order, such as amplitude dependent tune shift. We also explore the compensation of the third order effects by introducing families of octupoles in the extended beam area.
Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Supported in part by US DOE STTR grant DE-SC0006272.
JLAB, Newport News, Virginia, USA
Paul Scherrer Institut, Villigen, Switzerland
MIPT, Dolgoprudniy, Moscow Region, Russia
Science and Technique Laboratory Zaryad, Novosibirsk, Russia
The nuclear physics program envisaged at the Medium-energy Electron-Ion Collider (MEIC) currently being developed at the Jefferson Lab calls for collisions of 3-11 GeV/c longitudinally polarized electrons and 20-100 GeV/c, in equivalent proton momentum, longitudinally or transversely polarized light ions. In this paper, we present a scheme based on figure-8 shaped booster and collider rings that provides the required ion polarization arrangement in the MEIC's ion collider ring.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
JLAB, Newport News, Virginia, USA
DESY, Hamburg, Germany
JINR, Dubna, Russia
Old Dominion University, Norfolk, Virginia, USA
Science and Technique Laboratory Zaryad, Novosibirsk, Russia
ANL, Argonne, USA
SLAC, Menlo Park, California, USA
This paper will report the recent progress in the conceptual design of MEIC, a high luminosity medium energy polarized ring-ring electron-ion collider at Jefferson lab. The topics and achievements that will be covered are design of the ion large booster and the ERL-circulator-ring-based electron cooling facility, optimization of chromatic corrections and dynamic aperture studies, schemes and tracking simulations of lepton and ion polarization in the figure-8 collider ring, and the beam-beam and electron cooling simulations. A proposal of a test facility for the MEIC electron cooler will also be discussed.
JLAB, Newport News, Virginia, USA
In this paper, we present the current design of the large booster ring for the Medium Energy Electron-Ion Collder (MEIC) at JLab. The booster ring takes 3 GeV protons or ions of equivalent energy from a pre-booster ring, and accelerates them to 20 GeV for protons or equivalent energy for light to heavy ions before sending them to the ion collider ring. The present design calls for a figure-8 shape of the ring for superior preservation of ion polarization. The ring is made of warm magnets and shares a tunnel with the two collider rings. Acceleration is achieved by warm RF systems. A linear optics has been designed with the transition energy above the highest beam energy in the ring so crossing of transition energy will be avoided. Preliminary beam dynamics studies including chromaticity compensation, analyses of dynamic aperture, working point and high order effects are also presented in this paper.