IBS for RHIC operation below transition energy and various RF systems

Technical Report · Wed Feb 27 04:00:00 EST 2013

DOI:https://doi.org/10.2172/1069355· OSTI ID:1069355

Fedotov, Alexei ^[1]

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1. Brookhaven National Laboratory (BNL), Upton, NY (United States). Relativistic Heavy Ion Collider (RHIC)

Following first successful runs in RHIC at low energies for physics (Beam Energy Scan I) there is a strong interest in further low-energy RHIC operation in the range of γ=4-10 but with higher luminosity (Beam Energy Scan II). An electron cooling was proposed to increase luminosity at these low energies. Both transverse and longitudinal Intra-beam Scattering (IBS) can be counteracted with electron cooling. In addition, the phase-space density of the hadron beams can be further increased by providing stronger cooling. Unfortunately, the defining intensity limitation for low energies in RHIC is expected to be the space charge. Experimental studies of the space-charge effects and beam lifetime in RHIC were reported. Additional limitations at low energies and their possible mitigations were discussed. It was suggested that better luminosity performance may be expected by using lower frequency RF system and longer bunches compared to the baseline 28 MHz RF, which is being used for RHIC operation with heavy ions. Recently, even lower frequency RF of 4.5 MHz was proposed for future low-energy RHIC operation. Although low-frequency RF systems in RHIC (either 9 or 4.5 MHz) seem to address possible limitations of beam lifetime observed at low energies, the resulting ion beam temperatures in beam rest frame get further from an equilibrium which lead to a much stronger longitudinal IBS. This would put stronger requirement on electron cooling system under consideration. However, operation below transition energy allows us to exploit an IBS feature that drives the transverse and longitudinal beam temperatures towards equilibrium by minimizing the longitudinal diffusion rate using larger longitudinal beam emittance and larger RF voltage. Such studies were performed before to explore IBS redistribution at low energies for the 28 and 56 MHz RHIC RF systems. This Note presents results of similar studies for newly proposed 4.5 and 9 MHz RF systems.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States). Relativistic Heavy Ion Collider (RHIC)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1069355
• Report Number(s): BNL--99841-2013-IR; KB0202011
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
relativistic heavy ion collider