J. Sandberg

Simulations of the AGS MMPS storing energy in capacitor banks

The Brookhaven AGS Main Magnet Power Supply (MMPS) is a thyristor control supply rated at 5500 Amps, +/-9000 Volts. The peak magnet power is 50 MWatts. The power supply is fed from a motor/generator manufactured by Siemens. The generator is 3 phase 7500 Volts rated at 50 MVA. The peak power requirements come from the stored energy in the rotor of the motor/generator. The motor generator is about 45 years old, made by Siemens and it is not clear if companies will be manufacturing similar machines in the future. We are therefore investigating different ways of storing energy for future AGS MMPS operations. This paper will present simulations of a power supply where energy is stored in capacitor banks. Two dc to dc converters will be presented along with the control system of the power section. The switching elements will be IGCTs made by ABB. The simulation program used is called PSIM version 6.1. The average power from the local power authority into the power supply will be kept constant during the pulsing of the magnets at +/-50 MW. The reactive power will also be kept constant below 1.5 MVAR. Waveforms will be presented.

The active filter voltage ripple correction system of the Brookhaven AGS Main Magnet Power Supply

The Brookhaven AGS is a strong focusing accelerator which is used to accelerate protons and various heavy ion species to an equivalent proton energy of 29 GeV. Since the late 1960s it has been serving high energy physics (HEP-proton beam) users of both slow and fast extracted beams. Since the late 1980s slowly extracted heavy ion beams have been added for fixed target physics experiments (HIP). Beginning in 1996 fast extracted beams will be commissioned in preparation for injection into the RHIC accelerators. This paper, and a companion paper, describe the improvements to the Main Magnet Power Supply (MMPS) so that it enables a more flexible operation of the AGS, enhances its reliability, and also improves the MMPSs ultimate performance specifications. One of the major areas for the latter is the fixed target program operating off the AGS slow extracted beam lines. The active filter, by improving the MMPS output ripple, is instrumental in the improvement of the ultimate duty factor of the extraction beam spill.

Multiphase Transformer Effect and Harmonic Response Analysis of Accelerator Power System

Accelerator main dipole magnet system magnetic field regulation depends on its transmission line characteristic properties and its power supply system regulations. In addition, the main magnet AC power transformer configuration has indirect impact on the field quality of dipole magnet. A large accelerator main magnet system consists of hundreds, even thousands, of dipole magnets. They are linked together under selected configurations to provide uniform dipole fields when powered. When all dipole magnets are linked together in a synchrotron, they become a coupled pair of very high order complex ladder networks due to magnet parasitic capacitance, leakage resistance, and conductor resistance. In this study, we present multiphase transformer effect and harmonic response analysis of AGS main magnet system.

Overview of the ags cold snake power supplies and the new RHIC sextupole power supplies

The two rings in the Relativistic Heavy Ion Collider (RHIC) were originally constructed with 24 sextupole power supplies, 12 for each ring. Before the start of run 7, 24 new sextupole power supplies were installed, 12 for each ring. Individual sextupole power supplies are now each connected to six sextupole magnets. A superconducting snake magnet and power supplies were installed in the Alternating Gradient Synchrotron (AGS) and commissioned during RHIC run 5, and used operationally in RHIC run 6. The power supply technology, connections, control systems and interfacing with the quench protection system for both these systems will be presented.

Large scale distributed parameter model of main magnet system and frequency decomposition analysis

Large accelerator main magnet system consists of hundreds, even thousands, of dipole magnets. They are linked together under selected configurations to provide highly uniform dipole fields when powered. Distributed capacitance, insulation resistance, coil resistance, magnet inductance, and coupling inductance of upper and lower pancakes make each magnet a complex network. When all dipole magnets are chained together in a circle, they become a coupled pair of very high order complex ladder networks. In this study, a network of more than thousand inductive, capacitive or resistive elements are used to model an actual system. The circuit is a large-scale network. Its equivalent polynomial form has several hundred degrees. Analysis of this high order circuit and simulation of the response of any or all components is often computationally infeasible. We present methods to use frequency decomposition approach to effectively simulate and analyze magnet configuration and power supply topologies.

Analysis and simulation of main magnet transmission line effect

A main magnet chain forms a pair of transmission lines. Pulse-reflection-caused voltage and current differentiation throughout the magnet chain can have adverse effect on main magnet field quality. This effect is associated with magnet system configuration, coupling efficiency, and parasitic parameters. A better understanding of this phenomenon will help us in new design and existing system upgrade. In this paper, we exam the transmission line effect due to different input functions as well as configuration, coupling, and other parameters.

AGS slow extracted beam improvement

The Brookhaven AGS is a strong focusing accelerator which is used to accelerate protons and various heavy ion species to an equivalent proton energy of 29 Gev. Since the late 1960s it has been serving high energy physics (HEP-proton beam) users of both slow and fast extracted beams. The AGS fixed target program presently uses primary proton and heavy ion beams (HIP) in slowly extracted fashion over spill lengths of 1.5 to 4.0 seconds. Extraction is accomplished by flattopping the main and extraction magnets and exciting a third integer resonance in the AGS. Over the long spill times, control of the subharmonic amplitude components up to a frequency of 1 kilohertz is very crucial. One of the most critical contributions to spill modulation is due to the AGS MMPS. An active filter was developed to reduce these frequencies and its operation is described in a previous paper. However there are still frequency components in the 60-720 Hz sub-harmonic ripple range, modulating the spill structure due to extraction power supplies and any remaining structures on the AGS MMPS. A recent scheme is being developed to use the existing tune-trim control horizontal quadrupole magnets and power supply to further reduce these troublesome noise sources. Feedback from an external beam sensor and overcoming the limitations of the quadrupole system by lead/lag compensation techniques will be described.

The AGS main magnet power supply upgrade

The AGS is a strong focusing, combined function magnet, particle accelerator. The main parameters of the accelerator are a peak operating energy of 29.4 Gev, a peak magnetic field of 11.5 kG, a typical injection field of 0.9 kg, an injection energy of 1.5 Gev, and a maximum pulse repetition rate of 0.6 Hz. The injection is from a rapid cycling Booster synchrotron, which receives either a proton beam from a 200 Mev Linac, or a Heavy Ion beam from a 15 MV Tandem Van de Graaf Accelerator. Flattops of up to 2 seconds can be added to the AGS cycle for slow extracted beam applications. Particles accelerated include protons (mass=1), both polarized and non-polarized, and fully stripped ions up to gold (mass=197). The maximum proton intensity attained thus far is 60/spl times/10/spl circ/13 particles per pulse. Modes of operation for the AGS are full-turn extraction (2.5 usec), slow extraction (1-2 sec), and bunch-by-bunch extraction. These modes are applicable for both protons and heavy ions. The peak apparent power required during acceleration is approximately 70 MVA while the maximum average power needed is less than 7 MW. In order to isolate this large power swing from the local power grid, a motor-generator (MG) set is used as a buffering source. The MG set stores approximately 315 Kilojoules of energy in its rotating mass. As energy is drawn to charge or discharge the ring magnets, the speed of the rotating mass changes in such a manner as to supply the required load power demand. The input to the motor is controlled by a power regulator that forces the input power to be equal to the average losses during each cycle. The line sees nearly a constant load equal to the system losses. The peak power requirements are met by changes in the stored energy of the rotating mass that translates directly into speed variations. Thus, for a fixed operating cycle, the losses during each cycle are reproducible, and the speed oscillates around an average value and is returned to the same value at the beginning of each supercycle.

RHIC power supplies-failure statistics for runs 4, 5 and 6

The two rings in the Relativistic Heavy Ion Collider (RHIC) require a total of 933 power supplies to supply current to highly inductive superconducting magnets. Failure statistics for the RHIC power supplies will be presented for the last three RHIC runs. The failures of the power supplies will be analyzed. The statistics associated with the power supply failures will be presented. Comparisons of the failure statistics for the last three RHIC runs will be shown. Improvements that have increased power supply availability will be discussed. Further improvements to increase the availability of the power supplies will also be discussed.

RHIC power supplies: lessons learned from the 1999-2001 RHIC runs

The Relativistic Heavy Ion Collider (RHIC) was commissioned in 1999 and 2000. The two RHIC rings require a total of 933 power supplies (PSs) to supply currents to highly inductive superconducting magnets. These units function as 4 main PSs, 237 insertion region (IR) PSs, 24 sextupole PSs, 24 Gamma-T PSs, 8 snake PSs, 16 spin rotator PSs, and 620 correction PSs. PS reliability in this type of machine is of utmost importance because the IR PSs are nested within other IR PSs, and these are all nested within the main PSs. This means if any main or IR PS trips off due to a PS fault or quench indication, then all the IR and main PSs in that ring must follow. When this happens, the Quench Protection Assemblies (QPAs) for each unit disconnects the PSs from the circuit and absorb the stored energy in the magnets. Commissioning these power supplies and QPAs was and still is a learning experience. A summary of the major problems encountered during these first three RHIC runs will be presented along with solutions.