Phase locking the spin precession in a storage ring

This letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97 GeV/$c$ bunched and polarized deuteron beam in the Cooler Synchrotron (COSY) storage ring in order to control both the precession rate ($\approx 121$ kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a one standard deviation range of $\sigma = 0.21$ rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles

Investigation of Possibilities to Measure the Deuteron Electric Dipole Moment at Storage Rings

The interest in electric dipole moment (EDM) experiments is highly motivated by the problem of matter-antimatter asymmetry in our universe. New sources of CP-violation are needed to explain that phenomenon properly. An EDM of an elementary particle is a perfect candidate to search for these sources because its existence requires CP-violation beyond the Standard Model to be detected. New experiments for the EDM of charged hadrons are proposed. These experiments require a new type of storage ring to be built. Since an EDM could be as small as 10-29 e·cm, a fantastic precision should be achieved. The main cause that limits a potential sensitivity of future experiments are systematic errors. This thesis investigates possible ways to minimize various systematic errors for two versions of a new storage ring and for the precursor experiment, which will be performed by the JEDI (Jülich Electric Dipole moments Investigations) collaboration at the existing Cooler Synchrotron COSY. To study the impact of the systematic errors a large number of spin-orbit tracking simulations were performed in the newly developed program MODE. Two approaches for using a new storage ring were studied: the frozen and the quasi-frozen spin method. In addition, the precursor experiment at COSY was studied. The results of a test run conducted in 2014 made possible to benchmark and adjust the accelerator model and improve the simulation environment. One of the main quantities that defines the sensitivity is the spin decoherence, which takes place at any storage ring. The finite size of the bunch in all three directions, radial, vertical and longitudinal causes the particles’ spins to decohere. Using an RF cavity and a combination of sextupoles allows one to maximize the time during which the spins stay parallel to each other in the horizontal plane. The main source of systematic error is the misalignment of the elements inside the ring. For a dedicated storage ring, it was proposed to launch two beams in opposite directions (clockwise and counter-clockwise) to average out its impact. For the precursor experiment, the frequency mismatch between an RF Wien filter device that will be used and the frequency of the spin rotation is harmful. All error sources were thoroughly studied and the sensitivity limits were calculated. The EDM limit, which can currently be reached on the future experiments, is of the order of 10$^{-25}$ ─ 10$^{-26}$ e·cm. With the present situation at COSY, the accuracy of the precursor experiment is expected to be of the order of 10$^{-19}$ e·cm

Investigation of Lattice for Deuteron EDM Ring

The quasi-frozen spin (QFS) concept of a storage ring for deuteron EDM measurement is based on the fact that the anomalous magnetic moment has a small negative value. Due to this fact, the rotation of spin in two parts of ring with the magnetic and electric fields relative to the momentum can compensate each other. In contrast to the concept of frozen spin we have the freedom to choose the ring parameters and also greatly simplified lattice. We consider two possible options for the lattice based on QFS concept and compare them with the frozen spin lattice proposed by BNL. In the first QFS option, we use completely separate electric and magnetic parts that form a structure. In the second option, we suggest using only two magnetic arcs with two straight sections having the straight elements with magnetic and electric fields. The straight elements have a horizontal electric field of 120 kV/cm and a vertical magnetic field of 80 mT. They provide the compensation for the spin rotation in the arc and at the same time allow having straight electric plates without the higher orders field. This scheme could be tested in the COSY ring at FZ Jülich to prove the quasi-frozen spin concept

Systematic Errors Investigation in Frozen and Quasi-Frozen Spin Lattices of Deuteron EDM Ring

The search for the electric dipole moment (EDM) in the storage ring raises two questions: how to create conditions for maximum growth of the total EDM signal of all particles in bunch, and how to differentiate the EDM signal from the induced magnetic dipole moment (MDM) signal. The T-BMT equation distinctly addresses each issue. Because the EDM signal is proportional to the projection of the spin on the direction of the momentum, it is desirable to freeze the spin direction of all particles in a bunch along momentum. It can be successfully implemented in the Quasi Frozen (QFS) and Frozen (FS) Spin structures. However, in case of magnet misalignments, the induced MDM signal may arise in the same plane as the EDM signal and thereby prevent its registration. In this paper, we analyze the effect of errors together with the spin-tune decoherence of all particles in the bunch for FS and QFS options

Quasi-Frozen Spin Concept of Deuteron Storage Ring as an Instrument to Search for the Electric Dipole Moment

One of the possible arguments for the breaking of CP invariance is the existence of non-vanishing electric dipole moments (EDM) of elementary particles. Currently, the Jülich Electric Dipole Moment Investigation (JEDI) collaboration works under the conceptual design of the ring specifically for search of the deuteron electrical dipole moment (dEDM). The proposed Quasi-Frozen Spin concept differs from the Frozen Spin concept in that the spin of the reference particle is alternately deflected by a few degrees in different directions relative to momentum in the electric and magnetic parts of the ring. The QFS concept will allow using the existing COSY ring as pilot facility. The paper presents conceptual approach to ring design based on results of a study of spin decoherence and systematic errors, as well as the sensitivity estimation of the method to the determination of EDM