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.
DESIGN STUDY OF A PARTIAL SNAKE FOR THE AGS
A superconducting helical dipole magnet, which will help preserve the polarization of a proton beam in the Alternate Gradient Synchrotron (AGS), has been proposed. Replacing an existing solenoid type Siberian Snake with the helical magnet, the strength of the remaining intrinsic resonances, which are due to transverse coupling, can be reduced. This magnet has a field of 3 T and an effective length of 2 m. Field shape and multipole components obtained by 3D field calculations are discussed. Also, the cooling system for this magnet is studied.
Helical Partial Snake for the AGS
The success of the Partial Siberian Snake in the AGS has paved the way to ever increasing polarization of proton beams at high energy, up to 50% polarization at 21 GeV during the last polarized proton run. The latest improvement made toward reaching this level of performance was the introduction of an oscillating dipole field during acceleration. This magnet is used to induce a coherent betatron oscillation at a frequency near the betatron tune, enhancing the resonance strength and generating spin flip as the beam crosses four strong intrinsic resonances. It has been observed that much of the remaining depolarization occuring in the AGS is associated with transverse coupling resonances, whereby depolarizing resonances are seen not only when the vertical tune is at an integer relation with Gγ, but when the horizontal tune is as well. And, in fact, a major source of the transverse coupling is the strong solenoidal field of the Partial Siberian Snake. To combat the transverse coupling inherently produced by a solenoidal magnetic field, we have investigated the use of a helical dipole magnet in the AGS to generate a Partial Snake. Helical magnets will also generate some degree of transverse coupling, but it is shown below that the level of the coupling is dramatically reduced by this configuration. Unlike the helical dipole magnet Snakes to be used in RHIC, which each consist of four 2.4 m long superconducting, 4 Tesla magnets, the AGS Partial Snake would be composed of a single normal conducting helix with steering magnets on either side. The use of one helix with surrounding dipole magnets as a Snake has been proposed previously[1], but in the context of a full Snake (180◦ spin rotation). Here, we propose a solution where the spin rotation is some small fraction of 180◦, and which fits in the allotted straight section space of the AGS.