Engineering topics

Hock, Kiel

Publications and source records attributed to Hock, Kiel.

4 records

DOE OSTI2023

Commissioning results of the BNL Alternating Gradient Synchrotron booster AC dipole

Here, an AC dipole has been installed in the AGS booster as part of polarized beam developments for the future Electron Ion Collider (EIC). This will allow preserving helion beam polarization through two intrinsic resonances during acceleration to an energy corresponding to |$Gγ$| = 10.5. AC dipoles can preserve polarization by forcing the beam to undergo large amplitude vertical betatron oscillations. These coherent oscillations cause all particles to sample the strong horizontal fields of quadrupoles, and result in a full spin flip. In preparation for the AC dipole being used for polarized helions, it was first commissioned with polarized protons. The proton extraction energy was raised to allow protons to cross $Gγ$ = 0 + $v_y$ = 4.8087. As an artifact of the experiment using polarized protons, the booster settings for bunch extraction interfered with the coherent oscillations and limited the maximum coherent amplitude. This interference will be well separated in the case of polarized helions. Polarized protons crossed the $Gγ$ = 0 + $v_y$ intrinsic resonance with a full spin flip through use of the AC dipole. Simulations of the resonance crossing using Zgoubi accurately predict the polarization relative to the coherent amplitude.

43 PARTICLE ACCELERATORS↗

DOE OSTI2023

Helions below |Gγ| = 10.5 in AGS

Polarized helion collisions are part of the Electron Ion Collider physics program. The required intensity at collision is 1.2×10 11 at 70% polarization. The EBIS source is expected to provide 2×10 11 helions/bunch at 80% polarization. To reach the EIC requirements, the AGS at extraction will need 1.5×10 11 helions/bunch and negligible polarization loss. A critical point for polarization loss in the injectors is the AGS injection energy, which can occur at either |Gγ| = 7.5 or |Gγ| = 10.5. Injection at |Gγ| = 7.5 will result in 80% beam loss and 2.5% polarization up to |Gγ| = 10.5.

43 PARTICLE ACCELERATORS↗

DOE OSTI2023

Stripping Foils at the RHIC Injectors: A History

Stripping foils are used throughout Collider-Accelerator Department to strip ions of unwanted electrons. This is done in stages throughout the complex to optimize the transmission of particles. For polarized protons, they are injected into the AGS Booster as H-, and then stripped to H+. For ions from the tandem source, there are two stripping foils: one at the center and the other at the end of the tandem. The tandem foils will not be covered in this document. For ions out of the EBIS source, there is no use of stripping foils upstream of injection into the Booster. All ions that are not fully stripped in Booster are stripped further in the Booster to AGS (BTA) transfer line stripping foil assembly. Finally, any ions that are not fully stripped in the AGS are either stripped in the AGS to RHIC transfer line stripping foil, or as they are being dumped in the AGS by the plunging stripping foil (PSF) dependent on the particles intensity and charge. The BTA foil is the workhorse of the complex, having to provide the desired charge state of ions as light as O, and as heavy as Uranium. Optimizing the stripping efficiency to the desired charge state, while minimizing the energy lost and emittance growth from transiting the foil, requires careful consideration of the foil materials and thicknesses. This paper serves an overview of stripping foils at C-AD, with a review of foils from the construction of the AGS Booster to now.

43 PARTICLE ACCELERATORS↗

DOE OSTI2020

Imperfection resonance crossing in the AGS Booster

Polarized helions are part of the spin physics program for the EIC, allowing collisions of polarized neutrons with polarized electrons. Helion imperfection resonances are 2.4 times closer than protons. Helions cross two intrinsic resonances (|Gγ| = 12 - ν γ and |Gγ| = 6 + ν γ ) and six imperfection resonances |Gγ| = 5, 6, 7, 8, 9, and 10) in the Booster as they are accelerated to extraction at |Gγ| = 10.5. In this same range of γ, protons cross two imperfection resonances (|Gγ| = 3, and 4) and are extracted from the Booster prior to crossing the |Gγ| = 0 + ν γ . Preliminary benchmarking simulations are performed using protons crossing the |Gγ| = 3 and 4 imperfection resonances, results of which are compared to experimental data. The settings used for protons are extrapolated to the helion case to show there is sufficient corrector strength to preserve polarization at each imperfection resonance up to extraction.

43 PARTICLE ACCELERATORS↗