Stored beams of polarized protons, electrons, or deuterons can be spin flipped by sweeping an rf dipole's or solenoid's frequency through an rf spin resonance. Fitting such data to the modified Froissart-Stora equation's spin resonance strength ${\mathcal{E}}_{\mathrm{FS}}$ gave very large deviations from the $^{*}\mathcal{E}_{Bdl}$ obtained from each rf magnet's $\ensuremath{\int}{B}_{rms}dl$. We recently varied an rf dipole's frequency sweep range $\ensuremath{\Delta}f$, and the momentum spread $\ensuremath{\Delta}p/p$ and betatron tune ${\ensuremath{\nu}}_{y}$ of stored $1.85\text{ }\text{ }\mathrm{GeV}/c$ polarized deuterons. We found a sharp constructive interference when ${\ensuremath{\nu}}_{y}$ was near an intrinsic spin resonance. Moreover, over large $\ensuremath{\Delta}f$ and $\ensuremath{\Delta}p/p$ ranges, ${\mathcal{E}}_{\mathrm{FS}}$ was about 7 times smaller than the predicted $^{*}\mathcal{E}_{Bdl}$.

Unexpected reduction of rf spin resonance strength for stored deuteron beams

http://inspirehep.net/record/1494498/files/Thesis_MRosenthal.pdf

Experimental Benchmarking of Spin Tracking Algorithms for Electric Dipole Moment Searches at the Cooler Synchrotron COSY

The unpolarised differential cross section and the two deuteron tensor analysing powers Axx and Ayy of the � dp →{ pp}sn charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were obtained for small momentum transfers to a {pp}s system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27 GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters Cx,x and Cy,y that were carried out in the � dp →{ pp}sn reaction at 1.2 and 2.27 GeV. The values obtained for the proton analysing power A p also suggest the need for a radical re-evaluation of the neutron-proton elastic scattering amplitudes at the higher energy. It is therefore clear that such measurements can provide a valuable addition to the neutron-proton database in the charge-exchange region.

/pdf/the-neutron-proton-charge-exchange-amplitudes-measured-in-2gxfvjlotw.pdf

The neutron-proton charge-exchange amplitudes measured in the dp → ppn reaction

We recently analyzed all available data on spin-flipping stored beams of polarized protons, electrons, and deuterons. Fitting the modified Froissart-Stora equation to the measured polarization data after crossing an rf-induced spin resonance, we found 10--20-fold deviations from the depolarizing resonance strength equations used for many years. The polarization was typically manipulated by linearly sweeping the frequency of an rf dipole or rf solenoid through an rf-induced spin resonance; spin-flip efficiencies of up to $99.9%$ were obtained. The Lorentz invariance of an rf dipole's transverse $\ensuremath{\int}Bdl$ and the weak energy dependence of its spin resonance strength $\mathcal{E}$ together imply that even a small rf dipole should allow efficient spin flipping in 100 GeV or even TeV storage rings; thus, it is important to understand these large deviations. Therefore, we recently studied the resonance strength deviations experimentally by varying the size and vertical betatron tune of a $2.1\text{ }\text{ }\mathrm{GeV}/c$ polarized proton beam stored in COSY. We found no dependence of $\mathcal{E}$ on beam size, but we did find almost 100-fold enhancements when the rf spin resonance was near an intrinsic spin resonance.

Unexpected enhancements and reductions of rf spin resonance strengths

COSY electronic cooling is used after charge-exchange injection of H– or D– to produce the required emittance and momentum spread in the beam after the beam is accelerated. The cooled and accelerated beam is then used for experimental applications, such as, fast or slow extraction for experiments onto an external target. Methods for setting up the electronic-cooling system and limiting the ion-beam intensity are discussed.

Current Status of the COSY Electron Cooler (Jülich, Germany)

At COSY, electron cooling is used after stripping injection of H- or D- ions in order to prepare phase-space-dense ion beams before acceleration to a requested energy. The electron-cooled beam has been successfully applied for specific external experiments. The achievable beam intensity is limited by instabilities during the cooling process. Besides initial losses after injection, as long as the beam has still large emittances, the self-excitation of coherent betatron oscillations is the dominating beam loss mechanism. Perspectives for possible improvements are briefly addressed.

Present Performance of Electron Cooling at Cosy-J\"ulich

This report is dedicated to investigation of the beam parameter evolution in the experiments with internal target . In calculations of the proton and deuteron beams we concentrated an cluster, atomic beam, storage cell and pellet targets at ANKE experiment mainly. In these calculations electron and stochastic cooling, intrabeam scattering, scattering an the target and residual gas atoms are taken into account . Beam parameter evolution is investigated in the long-term time scale, up to one hour, at different beam energies in the range from 1 .0 to 2.7 GeV for proton beam and from 1 to 2 .11 GeV for deuteron beam. The results of numerical simulations of the proton and deuteron beam parameters at different energies obtained using new version of BETACOOL program (elaborated at the first stage of this work [1]) are presented . Optimum parameters of the electron cooling system are estimated . The COSY experiment requirements can be satisfied even when electron cooling time is rather long . That allows to apply an electron cooling system with circulating electron beam [2] . Such a system has potentially low cost in comparison with other possibilities . At the energy range from 500 keV to 1 .5 MeV only longitudinal magnetic field can provide an effective focusing of an intensive electron beam. The electron beam acceleration can be produced both by induction acceleration of electrons or using an RF electron LINAC. Specific limitations of such a cooling system are discussed . Preliminary design of the electron cooling system with circulating electron beam is described in the report . This report contains also preliminary program of experiments at LEPTA (Low Energy Particle Toroidal Accumulator), which are aimed to study the problems of electron cooling system with circulating electron beam. Presently the construction of LEPTA ring is in the final stage at JINR and experiments with circulating beam will be started the next year .

/pdf/electron-cooling-application-for-luminosity-preservation-in-11ped2wccw.pdf

Electron cooling application for luminosity preservation in an experiment with internal targets at COSY

Results of experimental studies of the electron cooling of a proton beam at COSY (Juelich, Germany) and an ion beam at HIMAC (Chiba, Japan) are presented. Intensity of the ion beam is limited by two general effects: particle loss directly after the injection and development of instability in a deep cooled ion beam. Methods of the instability suppression, which allow increasing the cooled beam intensity, are described.

Intensive Ion Beams in Storage Rings with Electron Cooling

Electron cooling and slow extraction

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