• Y. Luo, M. Bai, J. Beebe-Wang, J. Bengtsson, R. Calaga, W. Fischer, A.K. Jain, N. Malitsky, S. Peggs, F.C. Pilat, V. Ptitsyn, G. Robert-Demolaize, T. Satogata, S. Tepikian, D. Trbojevic
  BNL, Upton, Long Island, New York
• R. Tomás
  CERN, Geneva

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

In the article we review the nonlinear beam dynamics from nonlinear magnetic fields in the Relativistic Heavy Ion Collider. The nonlinear magnetic fields include the magnetic field errors in the interaction regions, chromatic sextupoles, and sextupole component from arc dipoles. Their effects on the beam dynamics and long-term dynamic apertures are evaluated. The online measurement and correction methods for the IR nonlinear errors, nonlinear chromaticity, and horizontal third order resonance are reviewed. The overall strategy for the nonlinear effect correction in the RHIC is discussed.

• F.C. Pilat, M. Bai, D. Bruno, P. Cameron, K.A. Drees, V. Litvinenko, Y. Luo, N. Malitsky, G.J. Marr, A. Marusic, V. Ptitsyn, T. Satogata, S. Tepikian, D. Trbojevic
  BNL, Upton, Long Island, New York

The reduction of beta* beyond the 1m design value at RHIC has been consistently achieved over the last 6 years of RHIC operations, resulting in an increase of luminosity for different running modes and species. During the recent 2007-08 deuteron-gold run the reduction to 0.70 from the design 1 m achieved a 30% increase in delivered luminosity. The key ingredients in allowing the reduction have been the capability of efficiently developing ramps with tune and coupling feedback, orbit corrections on the ramp, and collimation at injection and on the ramp, to minimize beam losses in the final focus triplets, the main aperture limitation for the collision optics. We will describe the operational strategy used to reduce the b*, at first squeezing the beam at store, to test feasibility, followed by the operationally preferred option of squeezing the beam during acceleration, and the resulting luminosity increase obtained in the Cu-Cu run in 2005, Au-Au in 2007 and the deuteron-Au run in 2007-08. We will also include beta squeeze plans and results for the upcoming 2009 run with polarized protons at 250 GeV.

• V. Ptitsyn, A.J. Della Penna, V. Litvinenko, N. Malitsky, T. Satogata
  BNL, Upton, Long Island, New York

Funding: Work performed under US DOE contract DE-AC02-98CH1-886

During the course of last RHIC runs the beta-functions at the collision points (beta*) have been reduced gradually to 0.7m. In order to maximize the collision luminosity and ensure the agreement of the actual machine optics with the design one, more precise measurements and control of beta* value and beta* waist location became necessary. The paper presents the results of the implementation of the technique applied in last two RHIC runs. The technique is based on well-known relation between the tune shift and the beta function and involves precise betatron tune measurements using BBQ system as well as specially developed knobs for beta* and beta* waist location control.

• T. Satogata, L. A. Ahrens, M. Bai, J.M. Brennan, D. Bruno, J.J. Butler, K.A. Drees, A.V. Fedotov, W. Fischer, M. Harvey, T. Hayes, W. Jappe, R.C. Lee, W.W. MacKay, N. Malitsky, G.J. Marr, R.J. Michnoff, B. Oerter, E. Pozdeyev, T. Roser, F. Severino, K. Smith, S. Tepikian, N. Tsoupas
  BNL, Upton, Long Island, New York

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

There is significant interest in RHIC heavy ion collisions at center of mass energies of 5-50 GeV/u, motivated by a search for the QCD phase transition critical point. The low end of this energy range is nearly a factor of four below the nominal RHIC injection center of mass energy of 19.6 GeV/u. There are several operational challenges in the low-energy regime, including harmonic number changes, longitudinal acceptance, magnet field quality, lattice control, and luminosity monitoring. We report on the results of beam tests with protons and gold in 2007–9, including first RHIC operations at √{(s_NN)=9.2} GeV and low-energy nonlinear field corrections at √{(s_NN)=5} GeV.

• N. Malitsky, J. Shah
  BNL, Upton, Long Island, New York
• N. Hasabnis
  Stony Brook University, Stony Brook

Funding: Work performed under auspices of the U.S. Department of Energy under Contract No. DE-AC02-98CH10886 with Brookhaven Science Associates, LLC

This paper presents a new extension to EPICS, approaching the Data Distributed Service (DDS) interface based on the Channel Access protocol. DDS is the next generation of the middleware industrial standards, bringing a data-centric publish-subscribe paradigm to distributed control systems. In comparison with existing middleware technologies, the data-centric approach is able to provide a consistent consolidated model supporting different data dissemination scenarios and integrating many important issues, such as quality of service, user-specific data structures, and others. The paper considers different features of the EPICS-DDS layer in the context of the accelerator high-level environment and introduces a generic interface addressing various types of accelerator toolkits and use cases.