Linear gas stopping cells have been used for nearly two decades to slow down projectile fragments at the National Superconducting Cyclotron Laboratory, now the Facility for Rare Isotope Beams, for experiments with low-energy and reaccelerated beams. In order to efficiently stop and rapidly extract light to medium-mass fast ions, a cyclotron gas-stopper has been constructed. It uses a cyclotron-type magnet and a helium-gas filled stopping chamber to slow down the injected beam. RF ion guides transport the stopped ions to the center of the magnet and axially through the bore before acceleration to <60 keV. Following successful offline tests, the cyclotron stopper was moved to an experimental vault and connected to a new momentum-compression beam line. Beam transport to and into the cyclotron stopper was tested with stable beams. Using 46K fragments, the first successful stopping and extraction of a high-energy beam with the cyclotron stopper was demonstrated.

Linear gas stoppers filled with helium have become a common tool to convert high energy rare isotope beams into low-energy beams. The National Superconducting Cyclotron Laboratory (NSCL) has designed and fabricated a new cryogenic gas stopper to maximize efficiency and beam rate capability in order to increase scientific reach at the facility. The Advanced Cryogenic Gas Stopper (ACGS) will increase extraction efficiency, reduce transport time, reduce molecular contamination of the isotope of interest, and minimize space charge effects. A novel 4-phase Radio Frequency wire-carpet generates a traveling electrical wave for fast ion transport, cryogenic cooling of the helium gas chamber reduces unwanted molecular formation, and the new planar geometry with the wire-carpet in the mid-plane of stopper alleviates space charge effects. Prototype testing of ACGS components have shown wire-carpet transport efficiencies greater than 95% and transport speeds up to 100 m/s. This presentation will show the first online tests with radioactive beams and report the efficiencies of the ACGS.

The NSCL has successfully used linear gas stopping cells for more than a decade to slow down near-relativistic projectile fragments to energies of tens of keV; first for experiments at low energy and later for reacceleration to Coulomb-barrier energies. In order to stop and rapidly extract light and medium-mass fast ions, which are difficult to efficiently thermalize in linear gas cells, a gas-filled, reverse cyclotron has been constructed. The device uses a cyclotron-type magnet and helium gas in a liquid-nitrogen (LN) cooled stopping chamber to confine and slow down the injected beam. The stopped ions are transported to the center of the magnet by an RF-carpet system, extracted axially through the bore with an ion conveyor and accelerated to < 60 keV energy for delivery to the users. For magnet commissioning and low-energy ion tests, the cyclotron gas stopper was constructed in a location that did not allow connection to the NSCL high-energy beamlines. However, all other components have been installed for the device. Efficient ion transport has been demonstrated with ions from a movable alkali source with the magnet energized. An experimental vault is being prepared to allow the connection of the cyclotron gas stopper to the NSCL beamline. The design for a dedicated momentum-compression beam line, similar to the ones feeding the existing linear gas cells (1,2), is complete and the components are under construction. Offline tests have ended and moving the cyclotron stopper to its destination has begun.

Rare isotopes are produced at the National Superconducting Cyclotron Laboratory NSCL by projectile fragmentation at energies of≈100MeV/u. TheNSCL has successfully used linear gas stopping cells for more than a decade to decelerate projectile fragments to the keV range; first for experiments at low-energy and more recently for reacceleration. A novel reverse-cyclotron has been constructed by the NSCL based on a superconducting sectored-cyclotron magnet and LN2-cooled He gas to confine and slow down the fragments. Efficient stopping is predicted even for light ions that are difficult to thermalize in linear gas cells. The thermalized ions are transported to the center by a radial RF-carpet system, extracted through the yoke with an ion conveyor and accelerated to <60 keV for delivery to users. Measured field profiles have confirmed field calculations. The cryogenic beam-stopping chamber has been installed inside the magnet. The RF ion-guiding components have been tested successfully offline and are being prepared for low-energy ion-transport tests inside the magnet.

The Michigan State University cyclotron gas-stopper magnet generates a strong focusing cyclotron magnetic field that permits an ion beam of up to 100 MeV/u to enter the magnet and have most of its energy reduced by low-pressure helium gas. The magnet has two superconducting coil cryostats mounted within warm iron poles and a warm split iron return yoke. The coils are connected in series using room temperature cables. The peak magnet stored energy is 3.5 MJ. The magnet has been tested to its full operating current of 180 A. During tests, the magnet discharged inadvertently three times. Two low-current discharges caused the magnet current to decay through the power supply system. A discharge at 180 A quenched the magnet, because the quench protection system caused the magnet to discharge across a 1.25-Ω resistor. This fired the cold quench protection diodes within the cryostat, quenching both coils. The magnetic field in the gap was measured as the magnet discharged. For the two low-current discharges, the magnetic field followed the current in the external magnet circuit. During a quench, the magnetic field decay rate was much slower than the external circuit current decay rate.

The two coils of the cyclotron gas-stopper magnet at Michigan State University (MSU) were each cooled down and filled with liquid helium made from 300-K gas separately using three PT415 coolers in the fall of 2014. The magnet was first powered in late 2014. During the process of powering the magnet, discharges occurred because the interlock system caused the magnet to discharge. As the magnet was powered to higher currents, the coil positions were changed using the cold mass support adjustments to ensure that forces on the cold mass supports were within the design limits. The force pattern on the cold mass supports was expected to change as the iron pole pieces saturated. Changes in the coil inductance were expected and observed as the iron pole pieces saturated. This paper describes the process that brings the magnet current up to its full current.

The design of a compact all-permanent magnet electron cyclotron resonance (ECR) ion source injector for the ReAccelerator Facility (ReA) at the Michigan State University (MSU) National Superconducting Cyclotron Laboratory (NSCL) is currently being carried out. The ECR ion source injector will complement the electron beam ion trap (EBIT) charge breeder as an off-line stable ion beam injector for the ReA linac. The objective of the ECR ion source injector is to provide continuous-wave beams of heavy ions from hydrogen to masses up to 136Xe within the ReA charge-to-mass ratio (Q/A) operational range from 0.2 to 0.5. The ECR ion source will be mounted on a high-voltage platform that can be adjusted to obtain the required 12keV/u injection energy into a room temperature radio-frequency quadrupole (RFQ) for further acceleration. The beam line consists of a 30kV tetrode extraction system, mass analyzing section, and optical matching section for injection into the existing ReA low energy beam transport (LEBT) line. The design of the ECR ion source and the associated beam line are discussed.

The cyclotron gas-stopper magnet at Michigan State University consists of two superconducting coils, each in its own cryostat. The two cryostats are mounted in the two warm iron poles of a sector cyclotron magnet used to control the orbit of heavy ions as the particle energy is being removed by circulating the ions through helium gas. Because the two poles of the magnet must be separated to install the gas chamber and beam extraction system, the magnet coils cannot be connected together. As a result, the magnet cold mass support system must carry the forces pushing the magnet into the iron pole as well as any decentering forces that occur from coil placement errors. The cold mass support system for each magnet coil consists of six compression supports that support magnet forces in the axial direction. In addition, there are three radial supports to center the coil axis coaxial with the axis of the iron poles. This paper presents an analysis of the superconducting magnet cold mass support system, which must be designed to have a spring constant that is higher than the magnet force constant at the full design current for the magnet.

Linear gas stopping cells have been used "successfully at NSCL to slow down ions produced by projectile fragmentation from the 100 MeV/u to the keV energy range. These 'stopped beams' have first been used for low-energy high precision experiments and more recently for NSCLs re-accelerator ReA. A gas-filled reverse cyclotron is currently under construction by the NSCL to complement the existing stopping cells: Due to its extended stopping length, efficient stopping and fast extraction is expected even for light and medium-mass ions, which are difficult to thermalize in linear gas cells. The device is based on a 2.6 T maximum-field cyclotron-type magnet to confine the injected beam while it is slowed down in approximate to 100 mbar of LN2-temperature helium gas. Once thermalized, the beam will be transported to the center of the device by a traveling-wave RF-carpet system, extracted along the symmetry axis with an ion conveyor and miniature RF-carpets, and accelerated to a few tens of keV of energy for delivery to the users.The superconducting magnet has been constructed on a 60 kV platform and energized to its nominal field strength. The magnet's two cryostats use 3 cryo-refrigerators each and liquid-nitrogen cooled thermal shields to cool the coil pair to superconductivity. This concept, chosen not to have to rely on external liquid helium, has been working well. Measurements of axial and radial field profiles confirm the field calculations. The individual RF-ion guiding components for low-energy ion transport through the device have been tested successfully. The beam stopping chamber with its 0.9 m-diameter RF carpet system and the ion extraction system are being prepared for installation inside the magnet for low-energy ion transport tests. (C) 2016 Elsevier B.V. All rights reserved.

The Michigan State University (MSU) cyclotron gas stopper magnet is a warm iron superconducting cyclotron dipole. The desired field shape is obtained by the pole iron profile. Each coil of the two halves is in a separate cryostat and connected in series through a warm electrical connection. The entire system is mounted on a high voltage platform, and is cooled using six two-stage 4.2 K pulse tube coolers. This paper presents the progress on the magnet fabrication, cooling, and current testing.

ReA3 E=0.085 QWR cryomodule is the third cryomodule for the superconducting LINAC of ReA3 reaccelerated beam facility, which will bring the maximum beam energy to 3 MeV/u for heavy ions. This cryomodule consists of 8 E=0.085 QWR cavities and 3 9T superconducting solenoids and operates at 4K. Qualification of cavities and FPCs and the construction of cold mass was completed in 2013. The installation of the module was completed this summer. Functioning not only as an important part of the ReA3 facility, cryomodule 3 also serves as a test bed for FRIB driver Linac and demonstrated the technology needed for FRIB CMs. Here we report the construction, installation and testing of the E=0.085 cryomodule and the development of the critical components.

The magnet for the cyclotron gas stopper is a newly designed, large warm-iron superconducting cyclotron sector gradient dipole. The maximum field in the centre (gap = 0.18 m) is 2.7 T. The outer diameter of magnet yoke is 4.0 m, with a pole radius of 1.1 m and B*rho = 1.8 T m. The fabrication and assembly of the iron return yoke and twelve pole pieces is complete. Separate coils are mounted on the return yokes that have a total mass of about 167 metric tons of iron. This paper illustrates the design and the fabrication process for the cyclotron gas-stopper magnet that is being fabricated at MSU.

The Facility for Rare Isotope Beams under construction and the existing National Superconducting Cyclotron Laboratory at Michigan State University will provide exotic low-energy rare isotope beams (KeV-MeV) by stopping relativistic fragments produced by projectile fragmentation at high energies (< 50 MeV/u). The stopped radioactive ions using the cyclotron gas stopper magnet system will feed the existing program centered on precision mass measurements of exotic nuclei and laser spectroscopy. Later on, stopped radioactive ions will be available as reaccelerated low-energy beams (< 15 MeV/u) using compact linear accelerator currently under construction. The cyclotron gas stopper magnet is a warm iron superconducting cyclotron sector dipole. The maximum field in the gap (0.18 m) is 2.75 T. The outer diameter of the magnet yoke is 4.0 m, with a pole radius of 1.1 m and Br = 1.8 T m. The desired field shape is obtained by a pole profile. Each coil of the two halves is in a separate cryostat and connected in series through a warm electrical connection. The entire system is mounted on a high voltage platform, and will be cooled by six cryocoolers. This paper presents the magnet design and discusses various design aspects of the magnet.

The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is currently constructing the new rare isotope reaccelerator facility, ReA3. The new facility will provide unique low-energy rare isotope beams by stopping fast rare isotopes in gas stopping systems, boosting the charge state in an Electron Beam Ion Trap (EBIT) and reaccelerating them in a compact superconducting linac [1,2,3]. The rare isotope beams will be produced initially by the existing Coupled Cyclotron Facility (CCF) at NSCL and later by Facility for Rare Isotope Beams (FRIB), currently being designed at MSU [4]. The ReA3 accelerator system consists of a Low Energy Beam Transport (LEBT), a room temperature RFQ and a superconducting linac utilizing superconducting quarter wave resonators. An achromatic High Energy Beam Transport and distribution beam lines towards the new ReA3 experimental area will deliver the reaccelerated rare isotope beams to the multiple target station. Beams from ReA3 will range from 3 MeV/u for heavy nuclei such as uranium to about 6 MeV/u for ions with A<50. The commissioning of the EBIT, RFQ and two cryomodules of the linac is currently underway. The accelerator system design and status of commissioning of ReA3 and future plan will be presented.

Rare isotopes are produced at the NSCL by projectile fragmentation at energies on the order of 100 MeV/u for a wide range of research. In order to provide these exotic ions to low-energy high precision experiments such as the Penning-trap mass spectrometer LEBIT and the collinear laser spectroscopy setup, or to the NSCL's re-accelerator (ReA), the beam must be slowed down into the eV range by solid degraders and interaction with buffer gas. A novel gas-filled reverse cyclotron is currently under construction by the NSCL and will complement a recently installed linear gas-filled cell. The new device is based on a 2.6 T maximum-field cyclotron-type three-sectored magnet to confine the injected beam while it is slowed down in approximate to 100 mbar of high-purity helium gas, cooled to liquid-nitrogen temperature. Once thermalized, the beam is transported to the center of the device by a novel RF-carpet system, extracted along the symmetry axis and accelerated to a few tens of keV of energy for delivery to the users.The device has been characterized in numerous simulations with full 3D models of its magnetic field. The beam transport has been modeled from the fragment separator to the point where they reach thermal energies. The simulations indicate that very efficient stopping and fast extraction will be possible even for light and medium-mass ions, which are difficult to efficiently thermalize in linear gas cells. Construction of the device is well underway and initial tests are planned for later this year. The design and the predicted performance of the machine is discussed and its construction status is given. (C) 2013 Elsevier B.V. All rights reserved.

The ReA reaccelerator is being added to the National Superconducting Cyclotron Laboratory (NSCL) fragmentation facility in order to provide exotic rare-isotope beams, not available at the Isotope Separation On-Line facilities, in the several-MeV/u energy range. The first stage of the NSCL reaccelerator complex, consisting of an EBIT charge breeder, a room-temperature radiofrequency quadrupole (RFQ) accelerator, and superconducting linear accelerator modules, has been completed and is being put into operation. Commissioning of the EBIT has started by extracting charge-bred residual gas ions, ions created from a Ne gas jet directed across the EBIT’s electron beam and ions captured from an external test ion source. Charge-bred ions from the Ne gas jet have been extracted as a pulse and accelerated through the RFQ and the two cryomodules.

Rare isotope beam (RIB) accelerator facilities provide rich research opportunities in nuclear physics in particular for nuclear structure physics, nuclear astrophysics and applied physics. The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is constructing a RIB facility, called ‘ReA3‘. The facility will provide unique low-energy rare isotope beams by stopping RIBs produced in-flight and reaccelerating them in a compact linac. ReA3 comprises gas stopper systems, an Electron Beam Ion Trap (EBIT) charge state booster, a room temperature radio frequency quadrupole (RFQ), a linac using superconducting quarter wave resonators (QWRs) and an achromatic beam transport and distribution line to the new experimental area. Beams from ReA3 will range from 3 MeV/u for heavy ions to about 6 MeV/u for light ions, as the charge state of the ions can be adjusted by the EBIT. ReA3 will initially use beams from NSCL‘s Coupled Cyclotron Facility (CCF). Later ReA3 will provide reacceleration capability for the Facility for Rare Isotope Beams (FRIB), a new national user facility funded by the Department of Energy (DOE) that will be hosted at MSU. The ReA3 concept and status of ReA3 will be presented, with emphasis on the commissioning of the facility, which is underway.

The Facility for Rare Isotope Beams (FRIB) is currently in the preliminary design phase at Michigan State University (MSU). FRIB consists of a driver LINAC for the acceleration of heavy ion beams, followed by a fragmentation target station and a ReAccelerator facility (ReA3). ReA3 comprises gas stopper systems, an Electron Beam Ion Trap (EBIT) charge state booster, a room temperature radio frequency quadrupole (RFQ), a LINAC using superconducting quarter wave resonators and an achromatic beam transport and distribution line to the new experimental area. Beams from ReA3 will range from 3 MeV/u for heavy ions to about 6 MeV/u for light ions. The ReA3 RFQ, which is of the 4 rod type, is designed to accelerate ions with an Q/A of 0.2 to 0.5 from 12 keV/u to 600 keV/u. The RFQ operates at a frequency of 80.5 MHz and power levels up to 120 kW at 10% duty factor. In this paper we will report on commissioning results from the ReA3 RFQ using H2 + and He + beam from an auxiliary ion source.

The Facility for Rare Isotope Beams (FRIB) is currently in the preliminary design phase at Michigan State University (MSU). FRIB consists of a driver LINAC for the acceleration of heavy ion beams, followed by a fragmentation target station and a ReAccelerator facility (ReA3). ReA3 comprises gas stopper systems, an Electron Beam Ion Trap (EBIT) charge state booster, a room temperature radio frequency quadrupole (RFQ), a LINAC using superconducting quarter wave resonators and an achromatic beam transport and distribution line to the new experimental area. Beams from ReA3 will range from 3 MeV/u for heavy ions to about 6 MeV/u for light ions. The ReA3 RFQ, which is of the 4 rod type, is designed to accelerate ions with an Q/A of 0.2 to 0.5 from 12 keV/u to 600 keV/u. The RFQ operates at a frequency of 80.5 MHz and power levels up to 120 kW at 10% duty factor. In this paper we will report on commissioning results from the ReA3 RFQ using H2 and He beam from an auxiliary ion source.