Design study of a normal conducting helical snake for AGS
A new normal conducting snake magnet is being fabricated for the alternate gradient synchrotron (AGS) at Brookhaven National Laboratory (BNL). In the Relativistic Heavy Ion Collider (RHIC) project, a superconducting type helical dipole magnets had been developed and it performed successfully in high-energy polarized proton acceleration. The new AGS helical snake has the same basic magnetic structure but is more complicated. To achieve no beam shift and no beam deflection in one magnetic device, helical pitches and rotating angles were carefully calculated. Compared to a superconducting magnet, a normal warm magnet must have a large cross-sectional area of conductors which make it difficult to design a magnet with large helical pitch. We developed a modified window frame structure to accommodate the large number of conductors. Its three dimensional magnetic field was simulated by using OPERA3D/TOSCA.
Exploration of horizontal intrinsic spin resonances with two partial Siberian snakes
Two partial Siberian snakes were used to avoid all the spin imperfection and vertical intrinsic resonances in the alternating gradient synchrotron (AGS) at Brookhaven National Laboratory. However, the horizontal betatron motion can cause polarization loss resulting from the nonvertical stable spin direction in the presence of two partial snakes. This type of resonance, called a horizontal intrinsic spin resonance, was observed and systematically studied in the AGS. A simplified analytic model and numerical simulation have been developed to compare with experimental data. Properties of the horizontal intrinsic resonance are discussed.
Spectroscopy of high rate events during active interrogation
Abstract Pulsed accelerators are being used for radiographic inspections in homeland security applications. Adding spectroscopic detection capability enables additional information to be extracted but challenges signal processing hardware. This work compares two approaches to cost-effective digital spectroscopy systems designed to handle these high rate scenarios. In the first system, the signal from a PMT is directly digitized and then deconvolved on a PC using standard techniques. Bypassing the preamplifier, this system can handle high count rates (>10 6  cps) from an LaCl 3 detector with no dead time and an energy resolution of 5% at 1.33 MeV. Spectra acquired from fission product gamma rays between interrogation pulses are shown. At higher rates, this approach is limited by the DAQ transfer rate to the PC. Instead, we tested a fast ADC (125 MSPS) and an FPGA that performed onboard, real-time digital signal processing (DSP). The energy spectrum is generated on the FPGA board during the measurement and transferred later. This system was tested in nuclear resonance fluorescence (NRF) experiments. Resonance peaks from NRF reactions are shown.