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Zeno, Keith

Publications and source records attributed to Zeno, Keith.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

The 2023 Gold Run in the Injectors

RHIC Run 23 used Gold beam from Tandem with an AGS extraction energy of 9.8 GeV. The same basic setup, 8 single bunch transfers from the Booster and a 12-6 merge in the AGS to provide 4 bunches at extraction, had been used before to deliver Tandem Au to RHIC. But in those cases, it was used for low energy runs (3.85 GeV in 2021 and 5.75 GeV in 2020) where extraction was below transition energy (7.9 GeV). Tandem beam was used for this run because the intensity and stability of EBIS Au did not meet the requirements for RHIC. Physics was first declared in RHIC on May 22 nd and on August 1 st the run was cut short by about 2 months due to a major failure in RHIC. Prior to the advent of EBIS as the preinjector in 2012, 9.8 GeV Tandem Au was regularly delivered to RHIC but the setup in the Booster and AGS was quite different: Four Booster transfers of 6 bunches each were merged into 4 bunches using a 24-12-4 merge scheme. The supercycle length was 6.0 sec before June 29 th when it was extended to 6.6 sec to accommodate EBIS commissioning. The Tandem, Booster, and AGS were on user 1 for the 9.8 GeV setup. Some work with EBIS Au 32+ took place on EBIS, Booster, and AGS user 5 using the standard 9.8 GeV injector setup with a 4 to 1 merge in Booster and a 6-3-1 type merge in AGS. The Siemens motor generator was used for the entire run. An intensity limit of 8.0e9 Au 77+ ions in the AGS was in effect during the run to protect the J7 plunging stripping foil and the Copper absorber of the AGS beam dump. This corresponds to a merged bunch intensity limit of 2.0e9 Au 77+ ions for 4 equal intensity bunches. The per bunch intensity limit can be increased to 2.67e9 by reducing the number of BtA transfers from 8 to 6. There was also a Booster Late intensity limit of 16e9 Au ions in effect to protect the BtA stripping foil from damage due to overheating. Lowering the number of transfers also makes this limit less of a constraint. BtA foil 5, which was installed in 2020 and had not been used regularly prior to this run was used all run and showed no obvious signs of deterioration. In May, a Tandem Au 3.85 GeV setup from 2021 was also re-established on AGS user 2. It was used for APEX on May 24 and July 26. Initial work with 3.85 GeV beam was on May 19. Proton beam was also set up during the run and extracted to W dump on July 10. It was used for APEX on July 12. Although the OPPIS source was used the AGS setup was without snakes.

43 PARTICLE ACCELERATORS↗
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 OSTI2022

The 2022 Polarized Proton Run in the Injectors

The previous polarized proton (PP) run was in 2017. During the start up process this run the injectors were set up in the same configuration using Booster and AGS PPM user 4 (BU4/AU4). Concurrently with this a new setup was established on Booster and AGS user 3 (BU3/AU3) called the split/merge. This new setup splits a single bunch into 2 in the Booster and recombines them on the AGS flattop in an attempt to improve polarization mainly by reducing the transverse emittance growth thought to be associated with higher peak beam current. Although Gold beam from EBIS was used at times in RHIC for LEReC and CeC development, from the injector perspective there is little noteworthy about it and so this note will focus solely on PP. According to the OC log, STAR Physics was first declared on Dec. 22, 2021 and the run ended on April 18, 2022. Initially, BU4/AU4 was used for RHIC. Then the split/merge setup was used from Dec. 27 until the Siemens motor generator failed on Jan. 12 and the Westinghouse motor generator had to be used in its place. The peak dB/dt available using the Westinghouse is half what it is with Siemens so the AGS required a different setup. Since the split/merge setup is more complicated than the standard one, and any benefit from it to polarization had not been demonstrated, a cycle was developed on AU6 for RHIC based on the AU4 setup but with a longer ramp. The split/merge was also set up with Westinghouse on BU3/AU7, but it was never used for RHIC. The switch back to the Siemens occurred on March 8 th once again using BU4/AU4.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

A Comparison of High Intensity Proton Efficiencies for Rf Harmonics 1 and 2

There have been many changes to the Booster setup over the past seven years, but the most fundamental physical change is probably the change from an Rf harmonic of 2 to 1. By looking at the intensity data over this period it is possible to compare the running efficiencies in each case. The harmonic change occurred at the beginning of the 1998 run. Another fundamental, though administrative, change that occurred after the 1998 run was the advent of ALARA alarms that limit the amount of beam loss that is allowed to occur during different parts of the cycle. These ALARA alarm limits also depend on the AGS repetition period since it is the amount of beam energy lost per unit time that is used as the criterion for these alarms. The 1998 h=1 run did not have an ALARA constraint, but subsequent h=1 runs did have that constraint. The highest Booster proton intensity was obtained in the h=2 mode (about 23 Tp). At best, the h=1 mode only yielded about 20 Tp per cycle. Is it because the h=2 setup can produce higher intensity than the h=1 setup that the h=2 intensity was higher, or is it because other factors are responsible? This note seeks to shed some light on this question. In order to compare the two setups (h=1 vs. h=2) intensity scaler data was taken from the setup books over the past seven years. In general, this data was taken when the Booster was in an optimized state. What ‘optimized’ means is not so clearly defined, but would typically mean that the Booster configuration was ‘optimized’ so that it yields the highest intensity late in the AGS given physical and other constraints.

43 PARTICLE ACCELERATORS↗