R. Hettel

The 3 GeV synchrotron injector for SPEAR

A dedicated 3-GeV injector synchrotron for the storage ring SPEAR has been constructed at the Stanford Synchrotron Radiation Laboratory, SSRL. The injector consists of an RF-gun, a 120-MeV linear accelerator, a 3-GeV booster synchrotron, and associated beam transport lines. General design features and special new developments for this injector are presented, together with operational performance.<<ETX>>

The linac and booster RF systems for a dedicated injector for SPEAR

A 120 MeV, 2856 MHz, traveling wave linear accelerator (linac), with a microwave gun, alpha magnet, and chopper, has been built at the Stanford Synchrotron Radiation Laboratory (SSRL) as a preinjector for and along with a 3 GeV, 358.54 MHz, booster synchrotron ring. The resulting injector will be available on demand to fill the Stanford Positron-Electron Accelerator Ring (SPEAR), which is a storage ring now dedicated to synchrotron light production. A description is given of the injectors two separate and different frequency RF systems. Synchronization of the two, non-harmonic systems is achieved through the linacs chopper. Some of the interesting mechanical and electrical details are discussed and the operating characteristics of the linac and ring RF are highlighted.<<ETX>>

Design and performance of the traveling-wave beam chopper for the SSRL injector

A pulsed, split-parallel plate chopper has been designed, built, and installed as part of the preinjector of the Stanford Synchrotron Radiation Laboratory (SSRL) injector. Its function is to allow into the linear accelerator (linac) three consecutive S-band bunches from the long bunch train provided by an RF gun. A permanent magnet deflector (PMD) at the chopper entrance deflects the beam into an absorber when the chopper pulse is off. The beam is swept across a pair of slits at the beam output end when a 7 kV, 10 ns rise-time pulse passes in the opposite direction through the 75 Omega stripline formed by the deflecting plates. Bunches exiting the slits have their trajectories corrected by another PMD, and enter the linac. Beam tests demonstrate that the chopper functions as expected.<<ETX>>

Triggers and timing system for the SSRL 3 GeV injector

The electron beam for the SSRL 3-GeV injector facility is produced in an RF gun. It is chopped by a stripline deflector to form a 1-ns-long beam bunch, injected into and extracted from a single 358-MHz RF bucket in a 10-Hz booster synchrotron, and injected into a preselected 358-MHz bucket in the SPEAR (Stanford Positron-Electron Asymmetric Ring) storage ring. The systems that generate 10-Hz triggers for the linac, beam chopper, and the pulsed and cycling magnets are described.<<ETX>>

The 10 Hz resonant magnet power supply for the SSRL 3 GeV injector

The booster synchrotron for the recently commissioned Stanford Synchrotron Radiation Laboratory (SSRL) injector facility employs a 10 Hz resonant magnet power supply system, or White circuit, as described by M.G. White et al. (1956), to accelerate an electron beam from 120 MeV to 3 GeV. Four major design specifications were required to establish the basic White circuit network: (1) the operating frequency; (2) the method of powering the quadrupoles; (3) the number of resonant cells and their configuration; and (4) the DC and AC power supply configuration. The booster dipole and quadrupole magnets are connected in series within a system of 17 distributed resonant cells driven by a pulsing network. Tracking power supplies driving the trim coils of the two quadrupole families are used to stabilize betatron tunes during energy ramping. The White circuit has proven to be a reliable and relatively simple system to operate during its several months of 2.35 GeV operation.<<ETX>>

Extraction septum magnet for the SSRL SPEAR injector

The Stanford Synchrotron Radiation Laboratory (SSRL) successfully commissioned a 3-3.5-GeV electron injector for the SPEAR storage ring during 1990. The injector operates at a 10-Hz repetition rate and accelerates approximately=10/sup 10/ electrons/s for extraction and transport to SPEAR. The extraction septum magnet is a pulsed Lambertson type which, for reasons of economy, was constructed from the same laminations which form 1/2 of an injector booster synchrotron dipole magnet core block. The excitation coil also utilizes a design in common with the pulse chokes of the booster magnet circuit. The septum magnet is pulsed by an SCR controlled resonant LC circuit with a resonant frequency of 30 Hz.<<ETX>>

Personnel protection and beam containment systems for the 3 GeV injector

The 3-GeV injector is the electron beam source for the Stanford Positron-Electron Asymmetric Ring (SPEAR) storage ring, and its personnel safety system was designed to protect personnel from both radiation exposure and electrical hazards. The personnel protection system (PPS) was designed and implemented with complete redundancy and is a relay-based interlock system completely independent from the machine protection system. Comprehensive monitoring of the system status and control of the injector PPS from the SPEAR control room via the control computer is a feature. The beam containment system (BCS) is based on beam current measurements along the linear accelerators (LINACs) and on beam shut-off ion chambers installed outside the LINAC, at several locations around the booster, and around the SPEAR storage ring. An outline of the design criteria is presented with a more detailed description of the philosophy of the PPS logic and the BCS.<<ETX>>

SPEAR 3 upgrade project: the final year

During April, 2003, the SPEAR 2 storage ring, which served the high energy physics community from 1972 to 1987, and the synchrotron radiation community for an additional 15 years, was removed from its shielding tunnel in order to install the new 3-GeV, 500-mA SPEAR 3 light source. From May to November, SSRL will excavate the tunnel floor and pour a new concrete floor, and then install pre-assembled girders holding magnets, copper vacuum chambers, PEP-II-style rf cavities, and beam line front end components. At the same time, power supply, instrumentation and control, and other ancillary systems will be configured, leading to a commissioning period beginning in November 2003. The progress of accelerator component implementation and installation during the final year of the project will be reviewed.

SPEAR III-a brighter source at SSRL

By replacing the magnets and vacuum chamber for the 3 GeV SPEAR II storage ring, the natural emittance of the machine can be reduced from 130 to 18 nm-rad and the stored current can be raised from 100 to 200 mA with a 50 h lifetime. This configuration increases focused photon flux for insertion device beamlines by an order of magnitude and the photon brightness for future undulators would exceed 10/sup 18/ at 5 keV. Due to a higher critical energy, the photon flux in the 20 keV range for bending magnet beamlines increases by more than two orders of magnitude. We present preliminary SPEAR III design study results and plans to implement the facility upgrade with minimal downtime for SSRL users.

Digital orbit feedback compensation for SPEAR

The global orbit feedback system for SPEAR will be upgraded in 1995 to achieve 30-50 Hz closed loop bandwidth. In this paper, we discuss issues related to measurements of the corrector frequency response, the DC response matrix, digital compensator design, and the impact of sequential BPM sampling. Results from detailed simulations are included.