The document describes the physics case of the PAX experiment using polarized antiprotons, which has recently been proposed for the new Facility for Antiprotons and Ions Research (FAIR) at GSI--Darmstadt. Polarized antiprotons provide access to a wealth of single-- and double--spin observables, thereby opening a new window to physics uniquely accessible at the HESR. The polarized antiprotons would be most efficiently produced by spin--filtering in a dedicated Antiproton Polarizer Ring (APR) using an internal polarized hydrogen gas target. In the proposed collider scenario of the PAX experiment, polarized protons stored in a COSY--like Cooler Storage Ring (CSR) up to momenta of 3.5 GeV/c are bombarded head--on with 15 GeV/c polarized antiprotons stored in the HESR. This asymmetric double--polarized antiproton--proton collider is ideally suited to map, e.g., the transversity distribution in the proton. The proposed detector consists of a large--angle apparatus optimized for the detection of Drell--Yan electron pairs.

Antiproton--Proton Scattering Experiments with Polarization

The paper describes the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at a beam kinetic energy of 49.3 MeV in COSY. The implementation of a low-$\ensuremath{\beta}$ insertion made it possible to achieve beam lifetimes of ${\ensuremath{\tau}}_{b}=8000\text{ }\text{ }\mathrm{s}$ in the presence of a dense polarized hydrogen storage-cell target of areal density ${d}_{t}=(5.5\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}\phantom{\rule{0ex}{0ex}}1{0}^{13}\text{ }\text{ }\mathrm{atoms}/{\mathrm{cm}}^{2}$. The developed techniques can be directly applied to antiproton machines and allow the determination of the spin-dependent $\overline{p}p$ cross sections via spin filtering.

Toward polarized antiprotons: Machine development for spin-filtering experiments

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 acceleration of polarized electrons, positrons, protons and ions in strong laser and plasma fields is a very attractive option to obtain polarized beams in the multi-MeV range. Recently, there has been substantial progress in the understanding of the dominant mechanisms leading to high degrees of polarization, in the numerical modelling of these processes and in their experimental implementation. This review article presents an overview on the current status of the field, on the concepts of polarized laser-plasma accelerators and of the beam polarimetry.

/pdf/generation-of-polarized-particle-beams-at-relativistic-laser-4zwtiu1ohh.pdf

Generation of polarized particle beams at relativistic laser intensities

The High-Energy Storage Ring (HESR) is part of the upcoming International Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt. An important feature of this new facility is the combination of powerful phase-space cooled beams and thick internal targets (e.g., pellet targets) to reach the demanding requirements of the internal target experiment PANDA in terms of beam quality and luminosity. In this paper the status of the preparatory work for the HESR at the FZ Julich is summarized. The main activities are beam dynamics simulations and hardware developments for HESR in combination with accelerator component tests and beam dynamics experiments at the Cooler Synchrotron COSY.

/pdf/the-high-energy-storage-ring-hesr-110zpsk2r1.pdf

The high-energy storage ring ( hesr )

For the Cooler Synchrotron COSY at the Research Center Julich a superconducting linear accelerator will replace the existing cyclotron which presently serves as an injector for COSY. The new injector will have to deliver polarized H - ions and polarized D - ions for injection into COSY with an energy of at least 50 MeV. The number of particles accepted in COSY is to be risen up to the space charge limit, which is a significant improvement especially for polarized ions. The polarized ions will be generated in a colliding beams source with magnetic extraction and subsequent electrostatic deflection. After the RFQ stage (up to 2.5 MeV/u) the particles will be fed into the LINAC section which consists of about 44 independently phased super- conducting 2-gap resonators. The ions are finally guided to the COSY injection point. The main characteristics of the LINAC operation will be 2 mA peak current, 2 Hz repetition rate, 500 us ion source pulse length. A facility description is given and designs are discussed. The status of the project is reported.

/pdf/a-superconducting-injector-linac-for-cosy-41gnixxtay.pdf

A superconducting injector linac for cosy

The High-Energy Storage Ring (HESR) of the future International Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt is planned as an antiproton storage ring in the momentum range from 1.5 to 15 GeV/c.1,2 The HESR is being designed and built by a consortium consisting of IKP at Forschungszentrum Julich, TSL at Uppsala University, and GSI Darmstadt. An important feature of this new facility is the combination of phase-space cooled beams and thick internal targets (e.g. pellet targets) which results in demanding beam parameter requirements for two operation modes: high luminosity mode with peak luminosities of up to 2 · 1032cm-2s-1 and high resolution mode with a relative momentum spread in the order of a few times 10-5. To reach these beam parameters one needs a very powerful phase-space cooling utilizing high-energy electron cooling and high-bandwidth stochastic cooling. In this paper different beam dynamics issues like closed orbit correction, performance of cooled beams interacting with internal targets and luminosity considerations are discussed.

Beam dynamics of the high-energy storage ring (hesr) for fair

At the cooler synchrotron COSY the year 1999 was predominantly determined by the development of vertically polarized proton beams in the whole momentum range from 300 MeV/c up to 3300 MeV/c. Starting with an initial polarization of 80 %, the beam could be accelerated up to maximum momentum with 4 ⋅ 10 9 protons at a polarization level of 75 %. The polarized beam has been used for an internal experiment as well as, after stochastic extraction, at an external target station. Beyond that the following developments were carried out: Electron cooler studies have been performed to increase the proton intensity with a combined cooling stacking injection. The now routinely operating stochastic cooling was upgraded by a fast frequency variable optical notchfilter. It will be employed in supercycles of COSY that allow varying flat top energies from cycle to cycle. Fast kicker beam extraction was investigated for the new experiment JESSICA. Finally, a new broadband cavity came into operation, which allows the simultaneous application of the fundamental frequency and higher harmonics. This report mainly deals with the development of polarized proton beams. At the end a summary of the other important activities is given together with references to contributions to this conference.

The medium energy proton synchrotron cosy

Super-conducting linear accelerator as injector for COSY has to accelerate D and H particles that differ in ratio of mass to charge by a factor of 2. There are two preferable types of linear accelerator structures appropriate for this purpose: multi-gap structure with internal synchronization of gaps working on first and second harmonics, and system with external synchronizing of the different groups of structures with few gaps. For the second type of structure the superconducting cavity is more appropriate due to lot of reasons. We consider two options of linear accelerator based on the super-conducting quarter-wave (QWC) and half-wave cavities (HWC). In both options the accelerator consists of two parts with 160 MHz and 320 MHz radio frequencies correspondingly. Simultaneously the cavities are subdivided into the families with the fixed geometry (or with the constant structure velocity β ). We optimize the number of cavities in each group and each family. We discuss how to optimize for protons and deuterium particles simultaneously. We analyze the 6-dimensional beam dynamics in the real field calculated by MAFIA. The quarter-wave cavity technology is quite developed, but due to the dipole component of magnetic and electrical fields the beam is unstable in the transverse plane. We have developed the special method to compensate this effect. In the half-wave cavities such problem does not exist due to the field symmetry. For the transverse plane we have examined the single, doublet and triplet systems. We have investigated the parametric resonance arising in the longitudinal plane due to the drift space needed for the focusing elements and determine the space limitation. 1 QUARTER-WAVE CAVITY To design the linear accelerator for both options quarterwave and half-wave cavities we integrate numerically the full system of motion equations in 6D phase space with the real field components taken from MAFIA calculations. In common case the transverse components of electrical and magnetic fields can be represented in the region of beam as ) ( / 0 0 0 r r r E E E r r r r − ⋅ ∂ ∂ + = = ) ( / 0 0 0 r r r B B B r r r r − ⋅ ∂ ∂ + = = . Thus, the beam has the dipole mode of motion due to 0 0 , E H and the quadrupole mode because 0 0 / , / r r r r r r r B r E = = ∂ ∂ ∂ ∂ . Due to nonsymmetry in the quarter-wave cavity the dipole compo-200.00 -150.00 -100.00 -50.00 0.00 50.00 -40.00 -30.00 -20.00 -10.00 0.00 10.00 dY/dZ, mrad Y, mm in all cases beam goes in this direction means one cavity Figure 1: X, dX/dZ position of beam for different schemes of compesation. nents 0 0 , E H are not negligible. Simultaneously we should note that in space the dipole component 0 H acts to the beam like a π mode, and 0 E action is like a 0mode. In time the H field is shifted relatively of E field for 90 degrees. All together give the uncompensated transverse kick to the particles. The total effect for all cavities is dramatically bad for the H and D beams and without compensation the bunch is shifted by 200 mm from axis (see fig.1). The method, which one could help to compensate the dipole components, has to be based of RF field, since 0 0 and H E depend on RF phase. Therefore we have analysed the different schemes of the cavities placement [1]. Figure 1 shows the results of the particles tracking in the real field for the option 4 groups of cavities with drift between cryomodules 0.7 m of length. We launch the bunch represented by the empty phase ellipse in the longitudinal plane with the zero initial transverse deviation for x, y, dx/dz, dy/dz and with energy spread % 5 . 1 ± and phase length of bunch 0 15 ± . The rotation of the cavities ( o o o 90 , 90 , 90 , 90 0 − − ) or inversely gives the minimum deviation of the bunch from the axis. The effective emittance growth due to this effect is 10% only. However, during the commissioning we expect the problems with the tuning the quadrupoles and RF fields separately. Therefore we have taken decision to use the half-wave cavities.

https://epaper.kek.jp/e02/papers/weple107.pdf

Some features of beam dynamics in super-conducting linac based on quarter- and half-wave cavities

At the cooler synchrotron COSY, polarized protons and deuterons are accelerated up to 3.65 GeV/c. In a strong‐focusing synchrotron like COSY, imperfection and intrinsic resonances cause polarization losses during acceleration. During the acceleration of polarized protons, five imperfection resonances are crossed. The existing magnet system of COSY allows to overcome all imperfection resonances by exciting adiabatic spin flips without polarization losses. The number of intrinsic resonances depends on the superperiodicity of the lattice. A tune‐jump system consisting of two fast quadrupoles has been developed to handle intrinsic resonances in COSY. Vertically polarized proton beams with more than 75% polarization have been delivered in recent years to internal as well as to external experiment areas at different momenta up to the maximum momentum of COSY. For the acceleration of polarized deuterons, additional correction provisions are not necessary to preserve polarization during acceleration. In this pape...

Overcoming Depolarizing Resonances at COSY

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