Small Isochronous Ring Project at NSCL

    The Small Isochronous Ring Project is under development at the National Superconducting Cyclotron Laboratory.  This web page describes briefly the main physics issues to be addressed by the ring and outlines the ring design.

Motivation

    The longitudinal-radial space charge effect is the main cause of current limitation in high intensity isochronous cyclotrons.  The space charge force increases energy spread within beam bunches and tends to destroy turn separation.  This leads to beam losses and extraction deflector overheating and activation.  The longitudinal space charge effect can also cause beam losses at the transition gamma in proton and heavy-ion synchrotrons.

    There is limited theoretical and experimental knowledge of high-intensity beam dynamics in isochronous accelerators.  To study the space charge in the isochronous regime experimentally, we intend to build a low-cost, low-field, low-energy isochronous ring.

Main physics issues addressed by the ring

    The important issues to be addressed by the ring are the space charge induced vertex motion specific to the isochronous regime, the formation of a self-consistent stable charge distribution by short bunches, the longitudinal break-up of long bunches, the formation of weak beam tails, and the beam halo.

Project overview

    The ring is a small-scale experiment that requires low beam intensities to simulate dynamics of intense beams in large-scale accelerators.

    The requirement of low cost of the project determined the choice of beam parameters: a low energy H₂⁺ or H⁺ beam.  The low beam energy and the high rest mass of the ions give a low particle velocity.  Because the space charge effect scales as 1/v³, the beam of low intensity is required for the experiment.  Besides, the low particle velocity relieves timing requirements on the diagnostics and on the injection-extraction system.

    The low beam energy allows us to use low field, simple design magnets.  Simulations show that the field in the magnets should be at the level of 1000 Gauss to avoid severe problems from stray fields.

MAIN PARAMETERS OF THE RING

Particles H2+ or H+ Energy 20 keV Beam Ipeak 50 µA Magnetic field 1000 Gauss Injection-Extraction Pulsed electrostatic kickers, t = 30 nanosec Diagnostics Fast coaxial Faraday Cup, t = 1 nanosec Circumference 5 m Total mass 400 kg Total power 4 kW

    A 20 keV, 25 µA, 100-1000 nanosecond long H₂⁺ or H⁺ beam is injected into SIR by means of a fast pulsed electrostatic inflector.  A fast semiconductor switch regulates voltage on the inflector.  The output of the switch is matched to the capacitive load of the inflector.  The ring itself consists of four 90° flat-field magnets with the edge focusing.  The edge focusing provides both the vertical focusing and the isochronism in the ring.  The extraction system, which is similar to the injection one, sends the beam to a diagnostic station, which consists of a beam size meter and a fast Faraday cup.  The longitudinal beam profile of the beam is measured by the Faraday Cup with time resolution 1 nanosecond that corresponds to spatial resolution 1.5 mm for H₂⁺ and 2 mm for H⁺.

Related Papers

2005

E. P. Pozdeyev, F. Marti, R. C. York, J. A. Rodriguez, “Experimental Results from the Small Isochronous Ring,” in Proceedings of the 2005 Particle Accelerator Conference, C. Horak, Editor, IEEE Publishing, Piscataway, New Jersey, 2005, p. 159-163.  PDF (JACoW)

E. Pozdeyev, F. Marti, R. C. York, J. Rodriguez, “Future Plans for the Small Isochronous Ring,” in Proceedings of the 2005 Particle Accelerator Conference, C. Horak, Editor, IEEE Publishing, Piscataway, New Jersey, 2005, p. 1778-1780.  PDF (JACoW)

2004

F. Marti, E. Pozdeyev, J. Rodriguez, “Study of Space Charge Effects using a Small Storage Ring that Works in the Isochronous Regime,” in Proceedings of the Seventeenth International Conference on Cyclotrons and their Applications: Tokyo, Japan, October 2004, A. Goto, Editor, Particle Accelator Society of Japan, 2005, p. 430-434.  PDF (JACoW)

J. Rodriguez, F. Marti, E. Pozdeyev, “Control System of the Small Isochronous Ring,” in Proceedings of EPAC 2004 Lucerne: Ninth European Particle Accelerator Conference, J. Chrin et al., Editors, EPS-AG/CERN, Geneva, Switzerland, 2004, p. 830-832.  PDF (JACoW)

J. Rodriguez, F. Marti, R. York, E. Pozdeyev, “Experimental Results of the Small Isochronous Ring,” in Proceedings of EPAC 2004 Lucerne: Ninth European Particle Accelerator Conference, J. Chrin et al., Editors, EPS-AG/CERN, Geneva, Switzerland, 2004, p. 2194-2196.  PDF (JACoW)

J. Rodriguez, F. Marti, E. Pozdeyev, “Beam Diagnostics of the Small Isochronous Ring,” in Proceedings of EPAC 2004 Lucerne: Ninth European Particle Accelerator Conference, J. Chrin et al., Editors, EPS-AG/CERN, Geneva, Switzerland, 2004, p. 2798-2800.  PDF (JACoW)

2003

E. Pozdeyev, R. Fontus, D. Lawton, F. Marti, J. Rodriguez, D. Sanderson, R. C. York, A. Zeller, R. Zink, “Progress Report on the Small Isochronous Ring Project at NSCL,” in Proceedings of the 2003 Particle Accelerator Conference, Joe Chew, Peter Lucas, & Sara Webber, Editors, IEEE Publishing, Piscataway, New Jersey, 2003, p. 138-140.  PDF (JACoW)

J. Rodriguez, E. Pozdeyev, F. Marti, “Initial Experimental Results of the Small Isochronous Ring (SIR),” in Proceedings of the 2003 Particle Accelerator Conference, Joe Chew, Peter Lucas, & Sara Webber, Editors, IEEE Publishing, Piscataway, New Jersey, 2003, p. 2649-2651.  PDF (JACoW)

2002

E. Pozdeyev, F. Marti, J. Rodriguez, R. York, “Small Isochronous Ring Project at NSCL,” in Proceedings of EPAC 2002 Paris: Eighth European Particle Accelerator Conference, T. Garvey et al., Editors, EPS-IGA/CERN, Geneva, 2002, p. 1395-1397.  PDF (JACoW)

E. Pozdeyev, J. Rodriguez, “Computer Simulations of the Beam Dynamics in the Small Isochronous Ring,” in Proceedings of EPAC 2002 Paris: Eighth European Particle Accelerator Conference, T. Garvey et al., Editors, EPS-IGA/CERN, Geneva, 2002, p. 1398-1400.  PDF (JACoW)

J. Rodriguez, E. Pozdeyev, F. Marti, “Injection Line of the Small Isochronous Ring,” in Proceedings of EPAC 2002 Paris: Eighth European Particle Accelerator Conference, T. Garvey et al., Editors, EPS-IGA/CERN, Geneva, 2002, p. 1401-1403.  PDF (JACoW)

2001

Eduard Pozdeyev, “A Small Isochronous Ring for Experimental Study of the Longitudinal Space Charge Effect in Isochronous Cyclotrons,” in Proceedings of the 2001 Particle Accelerator Conference, P. Lucas & S. Webber, Editors, IEEE Publishing, Piscataway, New Jersey, 2001, p. 3549-3551.  PDF (JACoW)