Richard york - Academia.edu (original) (raw)
Papers by Richard york
Aps April Meeting Abstracts, 2005
The national superconducting cyclotron laboratory at michigan state university
Nuclear Physics News, 2002
ABSTRACT The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University ha... more ABSTRACT The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University has constructed and operates two superconducting cyclotrons for research in nuclear science, accelerator and instrumental physics. The K500, the world's first superconducting cyclotron, was commissioned in 1982 and the K1200, the world's most powerful cyclotron, was commissioned in 1988. Heavy-ion beams across the entire periodic table produced in a pair of ECR ion sources and accelerated to energies on the order of 100 MeV/A are delivered to a modern and versatile complement of experimental apparatus, including the new S800 high-resolution superconducting magnetic spectrograph now undergoing initial testing. The diverse variety of beams are used for studies of the quantum-statistical properties of hot nuclei, the liquid-gas phase transition in nuclear matter, and for nuclear structure research, particularly with radioactive ion beams from the A1200 fragment separator. The NSCL provides radioactive nuclear beams out to the limits of stability on both the neutron-rich and the proton-rich sides of the valley of stability. The laboratory is also used for multi-disciplinary research in astrophysics, condensed matter physics, geophysics, medicine, and biology. The NSCL has recently proposed a major upgrade of its facility based on coupled operation of the two cyclotrons. The upgrade will provide large increases in beam intensities for radioactive beam production and increased energies of the heaviest beams.
Bulletin of the American Physical Society, Feb 1, 2010
The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the "const... more The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the "construction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society." A heavy-ion driver linac will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. Experiments can be done with rare isotope beams at velocities similar the driver linac beam, at near zero velocities after stopping in a gas cell, or at intermediate velocities (0.3 to 12 MeV/u) through reacceleration. An overview of the design proposed for implementation of the DOE national users facility FRIB on the campus of Michigan State University will be presented.
IEEE Transactions on Appiled Superconductivity, 2005
several avenues are being explored to improve and advance the use of SRF. Modifications to the sh... more several avenues are being explored to improve and advance the use of SRF. Modifications to the shape and heat transfer characteristics of existing designs are being studied to increase the accelerating gradient and reduce the cryogenic losses. Also, a new type of cavity based on the TM01p waveguide mode is presented that has the potential to improve high current linear accelerators or the use of advanced materials such as Nb 3 Sn or high-T c superconductors.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
The Rare Isotope Accelerator (RIA) will accelerate heavy ions to >400 MeV/u using an array of sup... more The Rare Isotope Accelerator (RIA) will accelerate heavy ions to >400 MeV/u using an array of superconducting cavities. A proposed linac design based on harmonics of 80.5 MHz will require six cavity types to cover the entire velocity range: three quarter wave resonators, one spoke cavity (half wave resonator), and two 6-cell elliptical cavities. A prototype 322 MHz niobium spoke with optimum velocity of 0.28c has been fabricated. Each spoke would generate over 1 MV at 4 K for acceleration from v/c=0.20 to 0.40. Details of the design and experimental study are presented.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
The Rare Isotope Accelerator (RIA) driver linac will produce >400 MeV/u proton through uranium be... more The Rare Isotope Accelerator (RIA) driver linac will produce >400 MeV/u proton through uranium beams using many types of superconducting accelerating cavities such as quarter wave, spoke, and elliptical cavities. A cryomodule design that can accommodate all of the superconducting cavity and magnet types is presented. Alignment of the cold mass uses a titanium rail system, which minimizes cryomodule size, and decreases both the tunnel cross-section and length. The titanium rail is supported from the top vacuum plate by an adjustable trilink, which is similar to existing Michigan State University magnet technology. A prototype cryomodule is under construction for testing 805 MHz, v/c=0.47, sixcell niobium cavities in realistic operating conditions. Details of the design and progress to date are presented.
Proceedings of the 2005 Particle Accelerator Conference
The Rare Isotope Accelerator (RIA) driver linac will use a superconducting, cw linac with indepen... more The Rare Isotope Accelerator (RIA) driver linac will use a superconducting, cw linac with independently phased superconducting rf cavities for acceleration and utilize beams of multiple-charge-states (multi-q) for the heavier ions. Given the acceleration of multi-q beams and a stringent beam loss requirement in the RIA driver linac, a new beam dynamics code capable of simulating nonlinearities of the multi-q beam envelopes in the longitudinal phase space was developed. Using optimization routines, the code is able to maximize the linearity of the longitudinal phase space motion and thereby to minimize beam loss by optimizing values for the amplitude and phase of the cavities for a given accelerating lattice. Relative motion of the multi-q beams is also taken into account so that superposition of the beam centroids and matching of their Twiss parameters are automatically controlled. The new tuning procedure and its benefit on the performance of the beam dynamics in the longitudinal plane are discussed in the paper.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
Optics of the CEBAF CW superconducting accelerator
ABSTRACT
Perturbation Effects in the CEBAF Beam Transport Systems
ABSTRACT
A three-dimensional (3D) particle-in-cell (PIC) code based on the template potential concept (1-6... more A three-dimensional (3D) particle-in-cell (PIC) code based on the template potential concept (1-6) has been upgraded by inclusion of a fully parameterized model for 3D space charge force calculations. The dynamics of a bunched 3D beam were studied for FODO channels having a conducting chamber with an arbitrary elliptical symmetry. The simulation results were in a good agreement with conventional 3D PIC models, but were obtained with ten to one hundred shorter computational times.
Preliminary RF testing has been done on a 2.45 GHz single-cell elliptically-shaped niobium cavity... more Preliminary RF testing has been done on a 2.45 GHz single-cell elliptically-shaped niobium cavity filled with liquid helium. Low-field results indicate little or no in- crease in the power dissipation, consistent with predictions and measurements in the literature. The frequency shift with pressure for the cavity filled with saturated liquid is about 100 times greater than when the cavity is under vac- uum, consistent with published values of liquid He permit- tivity as a function of temperature. An accelerating gradi- ent of about 5 MV/m was reached at a bath temperature of 2.4 K and a bath pressure of 1.4 bars.
As superconducting niobium cavities achieve higher gra- dients, it is anticipated they will reach... more As superconducting niobium cavities achieve higher gra- dients, it is anticipated they will reach a performance limit as the peak surface magnetic field approaches the critical magnetic field. Low loss (1) and reentrant (2) cavity de- signs are being studied at CEBAF, Cornell, DESY, and KEK, with the goal of reaching higher gradients via lower surface magnetic field, at the expense of higher surface electric field. At present, cavities must undergo chemical etching and high-pressure water rinsing to achieve good performance. It is not clear whether this can be done ef- fectively and reliably for multi-cell low loss or reentrant cavities using traditional techniques. A half-reentrant cav- ity shape has been developed with RF parameters similar to the low loss and reentrant cavities, but with the advantage that the surface preparation can be done easily with existing methods. Two 1.3 GHz prototype single-cell half-reentrant cavities have been fabricated; the non-reentrant wall angle i...
We have built a 161 MHz, b=0.16 superconducting Quarter Wave Resonator with steering correction f... more We have built a 161 MHz, b=0.16 superconducting Quarter Wave Resonator with steering correction for the low beta section of RIA. This bulk niobium, double wall cavity, compatible with both separate vacuum between beam line and cryostats or unified one, was designed in collaboration between MSU-NSCL and LNL. The design is suitable for extension to other frequencies, e.g. to obtain the 80.5 MHz, beta=0.085 cavity required in RIA. The shaped drift tube allows correction of the residual QWR steering that can cause emittance growth especially in light ions; this could make this resonator a good alternative to Half-Wave resonators in high intensity proton-deuteron linacs, like the SPES injector project at LNL. First test results will be presented.
The Facility for Rare Isotope Beams (FRIB), a Department of Energy (DOE) national user facility t... more The Facility for Rare Isotope Beams (FRIB), a Department of Energy (DOE) national user facility to provide intense beams of rare isotopes for nuclear science researchers, is currently being established on the campus of Michigan State University (MSU). A superconducting driver linac will deliver cw beams of stable isotopes with an energy of >200 MeV/u at a beam power of 400 kW. Highly charged ions will be produced from an Electron Cyclotron Resonance Ion Source (ECRIS) with a total extraction current of several mA. Multiple charge states of heavier ions will be accelerated simultaneously to meet the final beam power requirement. The FRIB driver linac lattice design has been developed and end-to-end beam simulations have been performed to evaluate the machine performance. An overview of the beam dynamics is presented.
Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167)
The Ion Cyclotron Resonance Accelerator (ICRA) is ideally suited for the production of radioisoto... more The Ion Cyclotron Resonance Accelerator (ICRA) is ideally suited for the production of radioisotopes or neutrons. The general theory of the ICRA and the designs of and simulation results for a proof-of-principle, one MeV ICRA and a 10 MeV ICRA for isotope or neutron production are presented.
2007 IEEE Particle Accelerator Conference (PAC), 2007
The Spallation Neutron Source (Oak Ridge), the proposed 8 GeV Proton Driver (Fermilab), and the p... more The Spallation Neutron Source (Oak Ridge), the proposed 8 GeV Proton Driver (Fermilab), and the proposed Rare Isotope Accelerator use multi-cell elliptical SRF cavities to provide much of the accelerating voltage. This makes the elliptical cavity segment the most expensive part of the linac. A new type of accelerating structure called a half-reentrant elliptical cavity can potentially improve upon existing elliptical designs by reducing the cryogenic load by as much as 40% for the same accelerating gradient. Alternatively, with the same peak surface magnetic field as traditional elliptical cavities, it is anticipated that half-reentrant designs could operate at up to 25% higher accelerating gradient. With a half-reentrant shape, liquids can drain easily during chemical etching and high pressure rinsing, which allows standard multi-cell processing techniques to be used. In this paper, electromagnetic designs are presented for three half-reentrant cell shapes suitable for an ion or proton linac (β = 0.47, 0.61 and 0.81, frequency = 805 MHz or 1.3 GHz). The mechanical designs for single-cell prototypes have also been completed.
Two superconducting quarter-wave resonator (QWR) prototypes have been fabricated and tested. They... more Two superconducting quarter-wave resonator (QWR) prototypes have been fabricated and tested. They operate at 80.5 MHz and 161 MHz and are optimised for beta = 0.085 and beta = 0.16, respectively. The prototypes are simplified versions without integrated helium vessels. In the first RF tests, the beta = 0.085 QWR reached a peak surface electric field (Ep) in excess of
Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999
A technique for computing the longitudinal electric fields of a bunched beam propagating inside a... more A technique for computing the longitudinal electric fields of a bunched beam propagating inside a conducting pipe is presented. A beam bunch is represented as a series of discs or slices, and the total electrical field is found by superposition of the fields of individual slices. The results of this technique agree well with other independent algorithms. The primary motivation for developing this technique is to provide efficient space charge calculations for beam dynamics simulation. However, the formalism may be employed in other applications to find electric fields for various beam density distributions in the presence of conducting boundaries.
Aps April Meeting Abstracts, 2005
The national superconducting cyclotron laboratory at michigan state university
Nuclear Physics News, 2002
ABSTRACT The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University ha... more ABSTRACT The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University has constructed and operates two superconducting cyclotrons for research in nuclear science, accelerator and instrumental physics. The K500, the world's first superconducting cyclotron, was commissioned in 1982 and the K1200, the world's most powerful cyclotron, was commissioned in 1988. Heavy-ion beams across the entire periodic table produced in a pair of ECR ion sources and accelerated to energies on the order of 100 MeV/A are delivered to a modern and versatile complement of experimental apparatus, including the new S800 high-resolution superconducting magnetic spectrograph now undergoing initial testing. The diverse variety of beams are used for studies of the quantum-statistical properties of hot nuclei, the liquid-gas phase transition in nuclear matter, and for nuclear structure research, particularly with radioactive ion beams from the A1200 fragment separator. The NSCL provides radioactive nuclear beams out to the limits of stability on both the neutron-rich and the proton-rich sides of the valley of stability. The laboratory is also used for multi-disciplinary research in astrophysics, condensed matter physics, geophysics, medicine, and biology. The NSCL has recently proposed a major upgrade of its facility based on coupled operation of the two cyclotrons. The upgrade will provide large increases in beam intensities for radioactive beam production and increased energies of the heaviest beams.
Bulletin of the American Physical Society, Feb 1, 2010
The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the "const... more The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the "construction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society." A heavy-ion driver linac will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. Experiments can be done with rare isotope beams at velocities similar the driver linac beam, at near zero velocities after stopping in a gas cell, or at intermediate velocities (0.3 to 12 MeV/u) through reacceleration. An overview of the design proposed for implementation of the DOE national users facility FRIB on the campus of Michigan State University will be presented.
IEEE Transactions on Appiled Superconductivity, 2005
several avenues are being explored to improve and advance the use of SRF. Modifications to the sh... more several avenues are being explored to improve and advance the use of SRF. Modifications to the shape and heat transfer characteristics of existing designs are being studied to increase the accelerating gradient and reduce the cryogenic losses. Also, a new type of cavity based on the TM01p waveguide mode is presented that has the potential to improve high current linear accelerators or the use of advanced materials such as Nb 3 Sn or high-T c superconductors.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
The Rare Isotope Accelerator (RIA) will accelerate heavy ions to >400 MeV/u using an array of sup... more The Rare Isotope Accelerator (RIA) will accelerate heavy ions to >400 MeV/u using an array of superconducting cavities. A proposed linac design based on harmonics of 80.5 MHz will require six cavity types to cover the entire velocity range: three quarter wave resonators, one spoke cavity (half wave resonator), and two 6-cell elliptical cavities. A prototype 322 MHz niobium spoke with optimum velocity of 0.28c has been fabricated. Each spoke would generate over 1 MV at 4 K for acceleration from v/c=0.20 to 0.40. Details of the design and experimental study are presented.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
The Rare Isotope Accelerator (RIA) driver linac will produce >400 MeV/u proton through uranium be... more The Rare Isotope Accelerator (RIA) driver linac will produce >400 MeV/u proton through uranium beams using many types of superconducting accelerating cavities such as quarter wave, spoke, and elliptical cavities. A cryomodule design that can accommodate all of the superconducting cavity and magnet types is presented. Alignment of the cold mass uses a titanium rail system, which minimizes cryomodule size, and decreases both the tunnel cross-section and length. The titanium rail is supported from the top vacuum plate by an adjustable trilink, which is similar to existing Michigan State University magnet technology. A prototype cryomodule is under construction for testing 805 MHz, v/c=0.47, sixcell niobium cavities in realistic operating conditions. Details of the design and progress to date are presented.
Proceedings of the 2005 Particle Accelerator Conference
The Rare Isotope Accelerator (RIA) driver linac will use a superconducting, cw linac with indepen... more The Rare Isotope Accelerator (RIA) driver linac will use a superconducting, cw linac with independently phased superconducting rf cavities for acceleration and utilize beams of multiple-charge-states (multi-q) for the heavier ions. Given the acceleration of multi-q beams and a stringent beam loss requirement in the RIA driver linac, a new beam dynamics code capable of simulating nonlinearities of the multi-q beam envelopes in the longitudinal phase space was developed. Using optimization routines, the code is able to maximize the linearity of the longitudinal phase space motion and thereby to minimize beam loss by optimizing values for the amplitude and phase of the cavities for a given accelerating lattice. Relative motion of the multi-q beams is also taken into account so that superposition of the beam centroids and matching of their Twiss parameters are automatically controlled. The new tuning procedure and its benefit on the performance of the beam dynamics in the longitudinal plane are discussed in the paper.
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)
Optics of the CEBAF CW superconducting accelerator
ABSTRACT
Perturbation Effects in the CEBAF Beam Transport Systems
ABSTRACT
A three-dimensional (3D) particle-in-cell (PIC) code based on the template potential concept (1-6... more A three-dimensional (3D) particle-in-cell (PIC) code based on the template potential concept (1-6) has been upgraded by inclusion of a fully parameterized model for 3D space charge force calculations. The dynamics of a bunched 3D beam were studied for FODO channels having a conducting chamber with an arbitrary elliptical symmetry. The simulation results were in a good agreement with conventional 3D PIC models, but were obtained with ten to one hundred shorter computational times.
Preliminary RF testing has been done on a 2.45 GHz single-cell elliptically-shaped niobium cavity... more Preliminary RF testing has been done on a 2.45 GHz single-cell elliptically-shaped niobium cavity filled with liquid helium. Low-field results indicate little or no in- crease in the power dissipation, consistent with predictions and measurements in the literature. The frequency shift with pressure for the cavity filled with saturated liquid is about 100 times greater than when the cavity is under vac- uum, consistent with published values of liquid He permit- tivity as a function of temperature. An accelerating gradi- ent of about 5 MV/m was reached at a bath temperature of 2.4 K and a bath pressure of 1.4 bars.
As superconducting niobium cavities achieve higher gra- dients, it is anticipated they will reach... more As superconducting niobium cavities achieve higher gra- dients, it is anticipated they will reach a performance limit as the peak surface magnetic field approaches the critical magnetic field. Low loss (1) and reentrant (2) cavity de- signs are being studied at CEBAF, Cornell, DESY, and KEK, with the goal of reaching higher gradients via lower surface magnetic field, at the expense of higher surface electric field. At present, cavities must undergo chemical etching and high-pressure water rinsing to achieve good performance. It is not clear whether this can be done ef- fectively and reliably for multi-cell low loss or reentrant cavities using traditional techniques. A half-reentrant cav- ity shape has been developed with RF parameters similar to the low loss and reentrant cavities, but with the advantage that the surface preparation can be done easily with existing methods. Two 1.3 GHz prototype single-cell half-reentrant cavities have been fabricated; the non-reentrant wall angle i...
We have built a 161 MHz, b=0.16 superconducting Quarter Wave Resonator with steering correction f... more We have built a 161 MHz, b=0.16 superconducting Quarter Wave Resonator with steering correction for the low beta section of RIA. This bulk niobium, double wall cavity, compatible with both separate vacuum between beam line and cryostats or unified one, was designed in collaboration between MSU-NSCL and LNL. The design is suitable for extension to other frequencies, e.g. to obtain the 80.5 MHz, beta=0.085 cavity required in RIA. The shaped drift tube allows correction of the residual QWR steering that can cause emittance growth especially in light ions; this could make this resonator a good alternative to Half-Wave resonators in high intensity proton-deuteron linacs, like the SPES injector project at LNL. First test results will be presented.
The Facility for Rare Isotope Beams (FRIB), a Department of Energy (DOE) national user facility t... more The Facility for Rare Isotope Beams (FRIB), a Department of Energy (DOE) national user facility to provide intense beams of rare isotopes for nuclear science researchers, is currently being established on the campus of Michigan State University (MSU). A superconducting driver linac will deliver cw beams of stable isotopes with an energy of >200 MeV/u at a beam power of 400 kW. Highly charged ions will be produced from an Electron Cyclotron Resonance Ion Source (ECRIS) with a total extraction current of several mA. Multiple charge states of heavier ions will be accelerated simultaneously to meet the final beam power requirement. The FRIB driver linac lattice design has been developed and end-to-end beam simulations have been performed to evaluate the machine performance. An overview of the beam dynamics is presented.
Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167)
The Ion Cyclotron Resonance Accelerator (ICRA) is ideally suited for the production of radioisoto... more The Ion Cyclotron Resonance Accelerator (ICRA) is ideally suited for the production of radioisotopes or neutrons. The general theory of the ICRA and the designs of and simulation results for a proof-of-principle, one MeV ICRA and a 10 MeV ICRA for isotope or neutron production are presented.
2007 IEEE Particle Accelerator Conference (PAC), 2007
The Spallation Neutron Source (Oak Ridge), the proposed 8 GeV Proton Driver (Fermilab), and the p... more The Spallation Neutron Source (Oak Ridge), the proposed 8 GeV Proton Driver (Fermilab), and the proposed Rare Isotope Accelerator use multi-cell elliptical SRF cavities to provide much of the accelerating voltage. This makes the elliptical cavity segment the most expensive part of the linac. A new type of accelerating structure called a half-reentrant elliptical cavity can potentially improve upon existing elliptical designs by reducing the cryogenic load by as much as 40% for the same accelerating gradient. Alternatively, with the same peak surface magnetic field as traditional elliptical cavities, it is anticipated that half-reentrant designs could operate at up to 25% higher accelerating gradient. With a half-reentrant shape, liquids can drain easily during chemical etching and high pressure rinsing, which allows standard multi-cell processing techniques to be used. In this paper, electromagnetic designs are presented for three half-reentrant cell shapes suitable for an ion or proton linac (β = 0.47, 0.61 and 0.81, frequency = 805 MHz or 1.3 GHz). The mechanical designs for single-cell prototypes have also been completed.
Two superconducting quarter-wave resonator (QWR) prototypes have been fabricated and tested. They... more Two superconducting quarter-wave resonator (QWR) prototypes have been fabricated and tested. They operate at 80.5 MHz and 161 MHz and are optimised for beta = 0.085 and beta = 0.16, respectively. The prototypes are simplified versions without integrated helium vessels. In the first RF tests, the beta = 0.085 QWR reached a peak surface electric field (Ep) in excess of
Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366), 1999
A technique for computing the longitudinal electric fields of a bunched beam propagating inside a... more A technique for computing the longitudinal electric fields of a bunched beam propagating inside a conducting pipe is presented. A beam bunch is represented as a series of discs or slices, and the total electrical field is found by superposition of the fields of individual slices. The results of this technique agree well with other independent algorithms. The primary motivation for developing this technique is to provide efficient space charge calculations for beam dynamics simulation. However, the formalism may be employed in other applications to find electric fields for various beam density distributions in the presence of conducting boundaries.