Coupling effect on the proton optics from the electron lenses Page: 2 of 9
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June 15, 2010
Coupling effect on the proton optics from the electron lenses
Y. Luo, X. Gu, W. Fischer
Brookhaven National Laboratory, Upton, NY 11973, USA
In this note we calculate the effect of the electron lense solenoids on the proton optics. Electron lenses
e-lenses ) are to be used for head-on beam-beam compensation in the Relativistic Heavy Ion Collider (RHIC).
1 Introduction
Electron lenses are to be used for head-on beam-beam compensation in the polarized proton (pp) runs
to compensate the large tune spread generated by the head-on proton-proton beam-beam interactions at
IP6 and IP8 in the Relativistic Heavy Ion Collider (RHIC) [1]. The main part of an electron lens is a
superconducting solenoid with a longitudinal magnetic field up to 6 T.
In the current design of RHIC head-on beam-beam compensation, there are two e-lenses, one for the
Blue ring called BEL and one for the Yellow ring called YEL. The effective length of these e-lens solenoids
is 2.0 m. They are located 1.5 m away from IP10. The actual operating solenoid field may range from 3 T
to 6 T. Figure 1 shows the layout of RHIC head-on beam-beam compensation at 250 GeV. Figure 2 shows
the locations of e-lenses around IP10.
As we know, solenoids will introduce betetron coupling into the proton linear optics. It will couple the
horizontal orbit into the vertical plane. If there is horizontal dispersion in the solenoid, it will generate
dispersion in the vertical plane. Beside the local coupling effect, the solenoid also will increase the eigen
tune split. To cancel the effects of the two solenoids on the betatron coupling, in the current design of RHIC
head-on beam-beam compensation, the two solenoids will be powered to have opposite magnetic fields.
In the following, we will estimate the e-elenses' effects on the ) and dispersion functions with 100 GeV
and 250 GeV pp run lattices. Table 1 lists some lattice and beam parameters to be used in the following
study.
IP12
*=10m
electron lens d
IP10 IP2
*=10 m P*=10 mn
IP8 PHENIX
(3*=0.5 IN
beam-beam f*=O0m
interaction
IP6STAR
P-=0.5 m
beam-beam interaction
Figure 1: Layout of RHIC head-on beam-beam compensation.1
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Luo, Y.; Gu, X. & Fischer, W. Coupling effect on the proton optics from the electron lenses, report, August 1, 2010; [Upton, New York]. (https://digital.library.unt.edu/ark:/67531/metadc1013964/m1/2/: accessed May 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.