F. Pilat

Beam based measurements of field multipoles in the RHIC low beta insertions and extrapolation of the method to the LHC

The multipolar content of the dipoles and quadrupoles is known to limit the stability of the beam dynamics in superconducting machines like RHIC and even more in LHC. The low-beta quadrupoles are thus equipped with correcting coils up to the dodecapole order. The correction is planned to rely on magnetic measurements. We show that a relatively simple method allows an accurate measurement of the multipolar field aberrations using the beam. The principle is to displace the beam in the non-linear fields by local closed orbit bumps and to measure the variation of sensitive beam observables. The resolution and robustness of the method are found appropriate. Experimentation at RHIC showed clearly the presence of normal and skew sextupolar field components in addition to a skew quadrupolar component in the interaction regions. Higher-order components up to decapole order appear as well.

RHIC POLARIZED PROTON NEW WORKING POINT COMMISSIONING

The RHIC 2003 polarized proton run showed a limitation on the luminosity due to the beam-beam effect at a betatron tune working point of (0.225,0.235). The integer parts of the horizontal and vertical betatron tunes are 28 and 29, respectively. The polarization transmission efficiency was also compromised because of the tight tune space due to the snake resonances. It was decided to explore the RHIC pp luminosity capability as well as the polarization capability with new working points during the RHIC pp 2004 Run. The working point (0.690.0.685) at a RHIC stored energy of 100GeVk was found to ameliorate the beam-beam effect, and also improve the polarization transmission efficiency as well as polarization lifetime during store. This paper reports the commissioning efforts and results of the new working point commissioning during the latest RHIC polarized proton run.

Polarized proton acceleration at the Brookhaven AGS and RHIC

Polarized proton beam has been accelerated and stored at 100GeV in Relativistic Heavy Ion Collider (RHIC) to study spin effects in the hadronic reactions. The essential equipment includes four Siberian snakes and eight spin rotators in two RHIC rings, a partial snake in the AGS, fast relative polarimeters, and ac dipoles in the AGS and RHIC. This paper summarizes the performance of RHIC as a polarized proton collider and of AGS as the injector to RHIC.

First Polarized Proton Collisions at RHIC

We successfully injected polarized protons in both RHIC rings and maintained polarization during acceleration up to 100 GeV per ring using two Siberian snakes in each ring. Each snake consists of four helical superconducting dipoles which rotate the polarization by 180{sup o} about a horizontal axis. This is the first time that polarized protons have been accelerated to 100 GeV.