Acceleration Of Polarized Protons Research Articles

Enhanced polarized proton acceleration driven by femtosecond laser pulses irradiating a micro-structured solid–gas target

Herein, we propose a scheme based on collision-less shock acceleration (CSA) involving the use of composite targets comprising a micro-structured foil and a pre-polarized gas for obtaining high-energy polarized proton beams. Femtosecond laser pulses irradiate a microwire-array (MWA) target and efficiently heat the dense plasma, which moves toward the dilute plasma. Shocks are then introduced in the pre-polarized gas to accelerate upstream spin-polarized protons to relativistic velocities. Based on particle-in-cell simulations with added spin dynamics, protons with energies of 30–300 MeV are produced, and the polarization rate of protons in the high-energy region exceeds 90%. The simulations demonstrate an evident increase in the temperature and number of hot electrons owing to the presence of MWA structures, which increase both the longitudinal electric field strength associated with the shock and the energy of the reflected protons. During CSA, the bipolar magnetic field driven by hot-electron currents demonstrates a weak effect on the polarization level of the accelerated protons, resulting in a high polarization rate. The relationship between the energy of the polarized proton beam and the hot-electron temperature enables an optimization of the micro-structured target and other target components to enhance proton quality via the CSA process.

Polarized proton acceleration in ultraintense laser interaction with near-critical-density plasmas.

The production of polarized proton beams with multi-GeV energies in ultraintense laser interaction with targets is studied with three-dimensional particle-in-cell simulations. A near-critical density plasma target with prepolarized proton and tritium ions is considered for the proton acceleration. The prepolarized protons are initially accelerated by laser radiation pressure before injection and further acceleration in a bubblelike wakefield. The temporal dynamics of proton polarization is tracked via the Thomas-Bargmann-Michel-Telegdi equation and it is found that the proton polarization state can be altered by both the laser field and the magnetic component of the wakefield. The dependence of the proton acceleration and polarization on the ratio of the ion species is determined and it is found that the protons can be efficiently accelerated as long as their relative fraction is less than 20%, in which case the bubble size is large enough for the protons to obtain sufficient energy to overcome the bubble injection threshold.

On the Possibility of Acceleration of Polarized Protons in the Synchrotron Nuclotron

One of the main tasks of the NICA project is to produce colliding beams of polarized protons. It is planned to accelerate polarized protons from the source to the maximum energy in the existing proton synchrotron. We consider all depolarizing spin resonances in the Nuclotron and propose methods to overcome them.

Acceleration of Polarized Protons up to 3.4 GeV/c in the Nuclotron at JINR

To preserve proton polarization in the Nuclotron up to 13.5 GeV/c, it is enough to use a partial solenoid snake with maximal field integral of 25 Tm that allows one to eliminate crossings of the most dangerous intrinsic and integer spin resonances. The insertion of weak field integral is sufficient to preserve the proton polarization up to 3.4 GeV/c. This momentum corresponds to the first intrinsic resonance. To preserve polarization during crossings of five integer spin resonances, it is possible to choose crossing rates that correspond to either the fast or the slow resonance crossings. Another possibility is a deliberate increasing of the resonance strength. To eliminate depolarization during protons injection into the Nuclotron, a scheme of matching of the polarization with a vertical direction is presented. During the run in February-March 2017, the three measurements of the proton polarization at kinetic energies of 0.5 GeV, 1 GeV and 2 GeV were made that allow one to obtain the integer spin resonances strengths.

Optimal axes of Siberian snakes for polarized proton acceleration

Accelerating polarized proton beams and storing them for many turns can lead to a loss of polarization when accelerating through energies where a spin rotation frequency is in resonance with orbit oscillation frequencies. First-order resonance effects can be avoided by installing Siberian Snakes in the ring, devices which rotate the spin by 180 degrees around the snake axis while not changing the beam's orbit significantly. For large rings, several Siberian Snakes are required. Here a criterion will be derived that allows to find an optimal choice of the snake axes. Rings with super-period four are analyzed in detail, and the HERA proton ring is used as an example for approximate four-fold symmetry. The proposed arrangement of Siberian Snakes matches their effects so that all spin-orbit coupling integrals vanish at all energies and therefore there is no first-order spin-orbit coupling at all for this choice, which I call snakes matching. It will be shown that in general at least eight Siberian Snakes are needed and that there are exactly four possibilities to arrange their axes. When the betatron phase advance between snakes is chosen suitably, four Siberian Snakes can be sufficient. To show that favorable choice of snakes have been found, polarized protons are tracked for part of HERA-p's acceleration cycle which shows that polarization is preserved best for the here proposed arrangement of Siberian Snakes.

Design Study of a Normal Conducting Helical Snake for AGS

A new normal conducting snake magnet is being fabricated for the alternate gradient synchrotron (AGS) at Brookhaven National Laboratory (BNL). In the Relativistic Heavy Ion Collider (RHIC) project, a superconducting type helical dipole magnets had been developed and it performed successfully in high-energy polarized proton acceleration. The new AGS helical snake has the same basic magnetic structure but is more complicated. To achieve no beam shift and no beam deflection in one magnetic device, helical pitches and rotating angles were carefully calculated. Compared to a superconducting magnet, a normal warm magnet must have a large cross-sectional area of conductors which make it difficult to design a magnet with large helical pitch. We developed a modified window frame structure to accommodate the large number of conductors. Its three dimensional magnetic field was simulated by using OPERA3D/TOSCA.

Observation of higher-order snake resonances in polarized proton acceleration in RHIC.

Higher-order and coupled snake resonances were observed during the 2002 polarized proton run in RHIC. Strong depolarization was observed when the fractional part of the vertical betatron tune approached 1/4, and when the fractional part of the horizontal tune approached 3/14. Because of the closed orbit error, each snake resonance splits into two. From the width of the observed snake resonances, we can derive the strength of the imperfection spin resonance. Our results appear consistent with the measured closed orbit error.

Proton-carbon CNI polarimeter for RHIC

A new polarimeter has been developed using proton carbon elastic scattering in CNI region for high energy proton polarimetry at RHIC. The analyzing power of the reaction measured by AGS experiment 950 and the first polarized proton acceleration commissioning results are presented.

Analytical field calculation of helical coils

Various helical coils such as helical dipole magnets, multifilamentary superconductors and superconducting strands have something in common with the helical structure. In this paper, we discuss the analytical calculation for the magnetic field of helical coils. In addition, the comparison between the analytical and numerical calculations is presented for simple helical coils. In particular, the helical multipole coefficients are introduced for helical dipole magnets, which are essential components of Siberian Snakes and spin rotators for polarized proton acceleration at Relativistic Heavy-Ion Collider (RHIC). The relation between the field homogeneity and helical multipoles is also studied. Finally, the analytically and numerically calculated and measured results of the magnetic field at the middle of the slotted helical dipole prototypes with the half-length for RHIC are compared. In this paper, the end effects of helical dipoles is not treated.

Spin-depolarization mechanisms due to overlapping spin resonances in synchrotrons.

We studied depolarization mechanisms of polarized-proton acceleration in high-energy accelerators with snakes and found that the perturbed spin tune due to the imperfection resonance plays an important role in beam depolarization at snake resonances. We also found that [ital even]-order snake resonances exist in the overlapping intrinsic and imperfection resonances. Due to the perturbed spin tune of imperfection resonances, each snake resonance splits into two. Thus the available betatron tune space becomes smaller. Some constraints on polarized-beam colliders were also examined.

Depolarizing Resonance Correction in Polarized Proton Beam Acceleration up to 5.0 GeV at the KEK PS

The research and development of polarized proton acceleration is being carried out at the KEK 12 GeV proton synchrotron. This paper describes the phenomena encountered in accelerating a polarized proton beam up to 5.0 GeV. Besides conventional methods for correcting depolarizing resonance, an adiabatic resonance crossing with pulsed quadruple magnets has been successfully applied to correct strong intrinsic resonances. At present, 90% of the linac polarization has been preserved in the booster synchrotron with reduced accelerating rf voltage to avoid the depolarization by synchrotron oscillation. In the main ring, 90% and 50% of the booster beam polarization was preserved at 3.5 GeV and 5.0 GeV, respectively. The KEK PS is the first cascaded synchrotron which has demonstrated a polarized proton beam.

A REVIEW OF POLARIZED PROTON BEAM TECHNIQUES AND A REPORT ON THE WORKSHOP ON POLARIZED BEAMS

This paper first introduces the basic techniques for polarized proton beams : spin flip, resonance jumps, Siberian Snakes, etc., and then concludes with a report on the Workshop on Acceleration and Storage of Polarized Protons and Electrons in Very Large Machines.

THE FIRST ACCELERATION TEST OF POLARIZED PROTONS IN KEK PS BOOSTER

Depolarization of the polarized proton beam accelerated in the 500 MeV booster was investigated as the first step of polarized proton acceleration in the KEK proton synchrotron. Beam polarization was measured in the 20 MeV beam transport line from the linac to the booster and in the main ring at the injection energy of 500 MeV. About 40 % of the linac beam polarization was kept in the main ring.

The Possibility of Acceleration of Polarized Protons in the Brookhaven AGS

The unexpected importance of high energy spin effects and the success of the 12 GeV Argonne ZGS in jumping many intrinsic and imperfection depolarizing resonances suggests that polarized proton acceleration should be tried at higher energy. The 1977 Ann Arbor Workshop concluded that it might be possible to jump depolarizing resonances in strong focusing synchrotrons. During the past year we have evaluated the possibility of accelerating polarized protons in the Brookhaven AGS. We found that for about $2 million one could obtain a polarized ion source, fast resonance jumping magnets, and 3 polarimeters which should allow acceleration of 1011 to 1012 polarized protons to 23 GeV/c with about 70% polarization or to 26 GeV/c with about 50% polarization.

Acceleration of Polarized Protons and Deuterons in a Tandem Accelerator

Acceleration of Polarized Protons and Deuterons in a Tandem Accelerator

Acceleration of Polarized Protons with Strong-Focusing Linear Accelerators

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