POLARIZATION MEASUREMENTS AND ABSOLUTE POLARIZATION VALUES EVOLUTION DURING PROTON BEAM ACCELERATION IN THE RHIC ACCELERATOR COMPLEX A.Zelenski, T.Roser, BNL. POLARIZATION MEASUREMENTS AND ABSOLUTE POLARIZATION VALUES EVOLUTION DURING PROTON BEAM ACCELERATION IN THE RHIC ACCELERATOR COMPLEX
POLARIZATION MEASUREMENTS AND ABSOLUTE POLARIZATION VALUES EVOLUTION DURING PROTON BEAM ACCELERATION IN THE RHIC ACCELERATOR COMPLEXA.Zelenski, T.Roser, BNL
POLARIZATION MEASUREMENTS AND ABSOLUTE POLARIZATION VALUES EVOLUTION DURING PROTON BEAM ACCELERATION IN THE RHIC ACCELERATOR COMPLEX
Absolute polarization measurements at different beam energies are very important for the understanding of the polarization evolution and polarization losses during acceleration and transport in the RHIC accelerator chain: Source-Linac-Booster-AGS-RHIC. In the RHIC complex there are two absolute proton polarimeters: the elastic proton-Carbon polarimeter at 200 MeV beam energy and theCNI H-jet polarimeter at 24-255 GeV in the RHIC ring.
The polarization transport simulations show that depolarization occurs a the edge of the beam and that the polarization of the beam core at the center of the 2-dimensional beam intensity profile should be preserved during acceleration. Polarization profile measurements by the scanning p-Carbon CNI polarimeters in the AGS and RHIC provide experimental data that support these expectations. In addition, an estimate for the upper limit of depolarization at the edge of the beam distribution was deduced from the absolute polarization measurements at 200 MeV and at 100 and 255 GeV.
Polarization facilities at RHIC.
Design goal - 70% Polarization L max = 1.6 1032 s-1cm-2 50 < √s < 500 GeV
RHIC pC “CNI” polarimeters
Pol. H- ion source
AGS pC “CNI” polarimeter
200 MeV polarimeter
BOOSTER, 2.5 GeV
Layout of the 200 MeV proton polarimeter, (2010)
Record 12.6∙1016 atoms/s
Atomic Beam intensity.
H-jet thickness at the collision point-1.2 ∙1012 atoms /cm2
Carbon Wire Target
Gas Jet Target
Beam Cross Section
The target ladder.
<P>=Pjet-average polarization measured by H-jet or p-Carbon polarimeter
in a sweep mode. P0-maximum polarization in the beam center.
For RH ≈ RV = R and small: P0 = Pjet (1+R)2 ;
Pcoll. = Pjet (1+ ½R)
Bazilevskiy, Roser, Fisher
About +/-3-5% errors, mostly systematic on all above numbers.
About 3-5% errors, mostly systematic on all above numbers.
Polarization profile R might be underestimated due to rate effects (AGS) and target deformation (largest effects at 255 GeV).
For RH ≈ RV = R , P0= 0.80, <P> =Pjet= 60%
R ~ 0.15 - upper limit on R.
Pcoll ~ 64.5%-upper limit
For R=0.1→ PpC~ 63%
PpC~ 63% < Pcoll < 64.5%
Maximum P0 ~ 80%-source polarization
(81% X 0.99 ~ 80%-for Yellow, 81% X 0.96 ~78% for Blue).
For R<<1 corrections for double spin asymmetry are small ~ (RV2 +RH2)/8.
P0=80% - Red line
P0=70% - Blue line
Pjet- black line
low limit on Pcoll
For P0=55 %, maximum
R=0.1, Pcoll.pC~ 58%
Pjet=58%< PpC.coll~61%≤ Pexp.coll < 63%
<P> ~ 71 × (1- ½ 0.08) ~ 68 %
AGS to RHIC Transfer:
Blue: <P> × 0.96 ~ 65.4%, P0 =76.8 %
Yellow: <P> × 0.99 ~ 67.5%, P0 =79%