Yu N Filatov

Polarized deuterons and protons at NICA@JINR

The novel scheme of proton and deuteron polarization control in the NICA collider at Dubna is proposed. By means of two Siberian Shakes with solenoid magnetic field the beam spin tune is shifted to the “zero” spin resonance vicinity, whereas manipulation of the polarization is realized by “weak” field solenoids. The scheme makes it possible to obtain any desired direction of the polarization in the both MPD and SPD detectors for any sort of the particles. The possibility of the beam polarization control in the orbit plane at any azimuth of the collider magnetic arcs exists also. The last gives necessary flexibility of optimal matching the beam polarization at injection into collider and at the polarimetery monitor points.

Polarized hadrons beams in NICA project

The report is dedicated to the problem of formation and maintenance of polarized proton and deuteron colliding beams in the collider of Nuclotron-based Ion Collider Facility (NICA). The NICA project is under development at JINR presently. The schemes of polarized proton and deuteron beams acceleration in the superconducting synchrotron Nuclotron and formation of both longitudinal and transverse particle polarization in the collider are presented. The problems of long term conservation of the beams polarization in the collider are discussed as well.

High-precision measurement of the polarized hadron beam energy in circular accelerator

A method for the high-precision measurement of the hadron polarized beam energy in circular accelerators by measuring the spin precession frequencies is offered. The problem of the particles energy measurement with accuracy better, than the beam energy spread, first of all, is connected with influence of synchrotron oscillations on spin motion. The given method develops the well-known method of high-precision measurement of electron-positron beams mean energy in case of a wide spin frequency spread.

Acceleration of polarized protons and deuterons in the ion collider ring of JLEIC

The figure-8-shaped ion collider ring of Jefferson Lab Electron-Ion Collider (JLEIC) is transparent to the spin. It allows one to preserve proton and deuteron polarizations using weak stabilizing solenoids when accelerating the beam up to 100 GeV/c. When the stabilizing solenoids are introduced into the collider’s lattice, the particle spins precess about a spin field, which consists of the field induced by the stabilizing solenoids and the zero-integer spin resonance strength. During acceleration of the beam, the induced spin field is maintained constant while the resonance strength experiences significant changes in the regions of “interference peaks”. The beam polarization depends on the field ramp rate of the arc magnets. Its component along the spin field is preserved if acceleration is adiabatic. We present the results of our theoretical analysis and numerical modeling of the spin dynamics during acceleration of protons and deuterons in the JLEIC ion collider ring. We demonstrate high stability of the deuteron polarization in figure-8 accelerators. We analyze a change in the beam polarization when crossing the transition energy. PRESERVATION OF ION POLARIZATION IN FIGURE-8 ACCELERATORS A characteristic feature of JLEIC [1] is its figure-8shaped rings [2]. Such a ring topology is transparent to the spin: the combined effect of arc fields on the spin in an ideal collider lattice reduces to zero after one particle turn on the design orbit, i.e. any orientation of the particle spin at any orbital location repeats from turn to turn. To preserve the polarizations of the proton and deuteron beams during acceleration from 8 GeV/c to 100 GeV/c in the ion collider ring, it is sufficient to use a weak solenoid with a field integral of 1.2 Tm, which does not perturb the design orbit and has practically no effect on the beam’s orbital parameters [3-10]. The solenoid then stabilizes longitudinal spin polarization at its location. A solenoid with the indicated field integral allows one to induce a spin tune � of 10-2 for protons and 310-3 for deuterons, i.e., when a particle with a vertical spin makes one turn on the design orbit, its spin tilts by an angle of �� from its initial orientation. For polarization stability, one must ensure that the spin tune � induced by the solenoid significantly exceeds [3-6] the strength of the zero-integer spin resonance �: � ≫ �. The resonance strength is the average spin field �⃗ (the zero-integer Fourier harmonic of the spin perturbation without a stabilizing solenoid) determined by deviation of the trajectory from the design orbit due to machine element errors and beam emittances. In the absence of a solenoid, the spin precesses by an angle of �� about the �⃗ direction in one particle turn. The resonance strength consists of two parts: a coherent part arising due to additional transverse and longitudinal fields on a trajectory deviating from the design orbit and an incoherent part associated with the particles’ betatron and synchrotron oscillations (beam emittances) [8, 9] �⃗ = �⃗ ��h + �⃗ ��� , ���h ≫ ���� In practice, the coherent part ���h significantly exceeds the incoherent one ���� . The coherent part does not cause beam depolarization and only results in a simultaneous rotation of the polarization about the field determined by the strength and alignment errors of collider elements. In principle, the direction and size of the coherent part of the resonance strength can be measured and taken into account for polarization control. To preserve the polarization, it is then sufficient to satisfy a weaker condition: � ≫ ���� . CALCULATION OF ZERO-INTEGER SPIN RESONANCE STRENGTH IN JLEIC Figure 1 shows  functions of the JLEIC collider lattice in the acceleration mode [11] used in our spin dynamics calculations. The origin of the coordinate frame is located at the colliders IP. Figure 1 also indicates the location of the solenoid stabilizing the spin during acceleration. The difference from the collision mode [12] where functions in the IP region reach 2.5 km is that, in the acceleration mode, the functions in the detector section do not exceed 150 m. Figure 1: functions of the ion collider ring. ___________________________________________ * Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. WEPIK038 Proceedings of IPAC2017, Copenhagen, Denmark ISBN 978-3-95450-182-3 3014 Co py rig ht

Superconducting racetrack booster for the ion complex of MEIC

The current design of the Medium-energy Electron-Ion Collider (MEIC) project at Jefferson lab features a single 8 GeV/c figure-8 booster based on super-ferric magnets. Reducing the circumference of the booster by switching to a racetrack design may improve its performance by limiting the space charge effect and lower its cost. We consider problems of preserving proton and deuteron polarizations in a superconducting racetrack booster. We show that using magnets based on hollow high-current NbTi composite superconducting cable similar to those designed at JINR for the Nuclotron guarantees preservation of the ion polarization in a racetrack booster up to 8 GeV/c. The booster operation cycle would be a few seconds that would improve the operating efficiency of the MEIC ion complex.

Preservation and control of the proton and deuteron polarizations in the proposed electron-ion collider at Jefferson Lab

We propose a scheme of preserving the proton and deuteron beam polarizations during acceleration and storage in the proposed electron-ion collider at Jefferson Lab. This scheme allows one to provide both the longitudinal and transverse polarization orientations of the proton and deuteron beams at the interaction points of the figure-8 ion collider ring. We discuss questions of matching the polarization direction at all stages of the beam transport including the pre-booster, large booster and ion collider ring.

Polarized proton beam acceleration at the Nuclotron with the use of the solenoid Siberian Snake

The possibility of polarized protons acceleration up to 6 GeV at the Nuclotron is analyzed. Proton beam acceleration by application of full and partial Siberian Snakes are considered. Compensation of the betatron coupling introduced by the solenoids is done by a compact insert of quadrupoles with a certain symmetry of their tilt angles around the orbit direction. Such a scheme has a shorter total length of the quadrupoles than the known compensation schemes. The Snakes installed within one, 3.2 m long, or two, 2 × 3.2 m long, straight sections of the Nuclotron lattice are considered.