Dynamic Aperture Calculations for the 2012 RHIC 100 Gev Polarized Proton Run

Abstract

In this article, we summarize the dynamic aperture calculations for the 2012 RHIC 100 GeV polarized proton run. We varied β∗ at the interaction action points, calculated the off-momentum dynamic aperture, and investigated the dependence of dynamic aperture on the proton bunch intensity and the proton beam transverse emittance. Based on the off-line optics model, we also applied second order chromaticity correction in the Yellow ring and compared the calculated dynamic apertures without and with the correction. In the end we compared the off-momentum dynamic apertures with different voltages of 197 MHz Landau RF cavity. INTRODUCTION The βs at the interaction points (IPs) in the recent RHIC 100 GeV polarized proton (p-p) runs were 1.0 m in 2006 run and 0.7 m in 2009 run. In 2009, we observed a poor beam lifetime and a short luminosity lifetime. Simulation and experiment proved that the β∗ = 0.7 m lattice gives a lower dynamic aperture [1]. Since the 2011 RHIC 250 GeV p-p run, to avoid the longitudinal and transverse emittance blow-ups, we began to use a 9MHzRF cavity for beam injection and energy acceleration. At physics store, besides the 28 MHz RF cavities, we turned on the 197 MHz Landau RF cavity to overcome the longitudinal instability. Figure 1 shows the RF momentum acceptance versus the full width bunch length. Here we def ne the full bunch length as 6 σl. In this calculation, we used 20 KV 9 MHz, 350 KV 28 MHz, and 200 KV 197 MHz RF cavities. At the beginning of store, the full proton bunch length was 15 ns, which gave the maximum momentum spread about dp/p0|max = 1.25 × 10 . DA VERSUS β∗ In the preparation for the 2012 RHIC 100 GeV p-p run lattices, we performed numerical simulations based on a 6D weak-strong beam-beam interaction model [2] to decide which β∗ we should adopt for this run. Fig. 2 shows the dynamic aperture as a function of β. In this calculation, the transverse rms emittance is 2.5 mm.mrad. The initial relative momentum deviation is 0.0005. Only 300 KV 28 MHz RF cavities are used. From Fig. 2, the dynamic aperture drops with the decrease of β. The reason is that with a This work was supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. 0.0007 0.0008 0.0009 0.001 0.0011 0.0012 0.0013 0.0014 0.0015 10 11 12 13 14 15 16 17 18 19 dp /p 0 | m ax [1 0 3 ] Full bunch length [ ns ] Figure 1: The RF momentum acceptance versus the full width bunch length.