Two electron lenses (e-lenses) have been in operation during the 2015 RHIC physics run as part of a head-on beam-beam compensation scheme. While the RHIC lattice was chosen to reduce the beam-beaminduced resonance-driving terms, the electron lenses reduced the beam-beam-induced tune spread. This has been demonstrated for the first time. The beam-beam compensation scheme allows for higher beam-beam parameters and therefore higher intensities and luminosity. In this paper, we detail the design considerations and verification of the electron beam parameters of the RHIC e-lenses. Longitudinal and transverse alignments with ion beams and the transverse beam transfer function measurement with head-on electronproton beam are presented.

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Deuteron and gold beams have been accelerated to a collision energy of 6 = 200 GeVfa in the Rehtivistic Heavy Ion Collider (RHIC), providing the fkst asymmetric-species collisions of this complex. Necessaxy changes for this mode of operation include new ramping software and asymmetric crossing angle geometries. This paper reviews machine pedormance, problem encountered and their solutions, and accomplishments during the 16 weeks oframp-up and operations.

The independence of the spin tune of the momentum is a critical requirement for a full spin flip using the RHIC spin flipper. We show how the spin chromaticity can be corrected with a minimum impact on the RHIC optics and how the correction improves the spin flip.

There is significant interest in RHIC heavy ion coIlisions at , , h =5-50 GeV/u, motivated by a search for the QCD phase transition critical point. The lowest energies are well below the nominal RHIC gold injection fi = 19.6GeVIu. There are several challenges that face RHIC operations in this regime, including longitudinal acceptance, magnet field quality, lattice control, and luminosity monitoring. We report on the status of work to address these challenges, including results from beam tests of low energy RHIC operations with protons and gold.