Achieving 99.9% Proton Spin-Flip Efficiency At Higher Energy With A Small rf Dipole

Abstract

We recently used a new ferrite rf dipole to study spin flipping of a 2:1 GeV=c vertically polarized proton beam stored in the COSY Cooler Synchrotron in Jülich, Germany. We swept the rf dipole's frequency through an rf-induced spin resonance to flip the beam's polarization direction. After determining the resonance's frequency, we varied the frequency range, frequency ramp time, and number of flips. At the rf dipole's maximum strength and optimum frequency range and ramp time, we measured a spin-flip efficiency of 99:92 0:04%. This result, along with a similar 0:49 GeV=c IUCF result, indicates that, due to the Lorentz invariance of an rf dipole's transverse R Bdl and the weak energy dependence of its spin-resonance strength, an only 35% stronger rf dipole should allow efficient spin flipping in the 100 GeV BNL RHIC Collider or even the 7 TeV CERN Large Hadron Collider. [7,8]. Many polarized scattering experiments require frequent spin-direction reversals (spin flips), while the polarized beam is stored, to reduce their systematic errors. Spin resonances [9,10] induced by either an rf solenoid or rf dipole can produce these spin flips in a well controlled way [11][12][13][14][15][16][17][18][19][20][21].An rf dipole was earlier used [19] to spin flip 120 MeV (490 MeV=c) polarized protons stored in the IUCF Cooler Ring with a 99:93 0:02% spin-flip efficiency. At very high energy, the spin-flip efficiency with an rf dipole should become almost independent of energy, mostly due to the Lorentz invariance of a magnet's transverse R Bdl [22]; this invariance is quite important for very high energy polarized proton rings [23]. To confirm this we recently used an rf dipole to study the spin flipping of 2:1 GeV=c polarized protons stored in the COSY ring.In any flat storage ring or circular accelerator with no horizontal magnetic fields, each proton's spin precesses around the vertical fields of the ring's dipole magnets. The spin tune s , which is the number of spin precessions during one turn around the ring, is proportional to the proton's energywhere G g ÿ 2=2 1:792 847 is the proton's gyromagnetic anomaly and is its Lorentz energy factor. The vertical polarization can be perturbed by an rf dipole's horizontal rf magnetic field. This perturbation can induce an rf depolarizing resonance, which can flip the spin direction of the stored polarized protons [11][12][13][14][15][16][17][18][19][20][21]; the resonance's frequency iswhere f c is the protons's circulation frequency and k is an integer. Adiabatically ramping the rf magnet's frequency through f r can flip each proton's spin. The Froissart-Stora equation [9] relates the beam's initial polarization P i to its final polarization P f after crossing the resonance,the ratio f=t is the resonance crossing rate, where f is the ramp's full-frequency range during the ramp time t. The resonance strength is given bywhere e is the proton's charge, p is its momentum, and R B rms dl is the rf dipole's rms magnetic field integral. The apparatus used for this experiment, includin...

Electromagnetic Simulation and Design of a Novel Waveguide RF Wien Filter for Electric Dipole Moment Measurements of Protons and Deuterons

“…A prototype RF Wien filter, based on an already existing RF dipole with radial magnetic field [13,14], was recently developed and used at COSY. (The use of RF dipoles and solenoids to manipulate stored polarized beams is discussed in [15].)…”

Narrow Spin Resonance Width and Spin Flip with an rf-Bunched Deuteron Beam

“…A horizontal magnetic field can perturb the particle's stable vertical polarization creating a spin resonance [12][13][14]. Rf magnets can induce rf spin resonances [15][16][17][18][19][20][21][22]. A proton's rf-induced spin resonance's frequency is…”

Higher Order Spin Resonances in a2.1−GeV/cPolarized Proton Beam

“…The experiment's apparatus, including the COSY storage ring [20,21], EDDA detector [22,23], electron cooler [24], low energy polarimeter (LEP) [25], injector cyclotron, and polarized ion source [26][27][28], were shown in Fig. 1 of Ref [29]. The beam from the polarized H − ion source was accelerated by the cyclotron to 45 MeV and then strip-injected into COSY.…”