ion polarization control in meic rings using small magnetic fields integrals. pstp 13 v.s. morozov...

V.S. Morozov et al., Ion Polarization Control in MEIC Rings Using Small Magnetic Fields Integrals.Ion Polarization Control in MEIC Rings Using Small Magnetic Fields Integrals. PSTP 13PSTP 13, University of Virginia, Charlottesville, VA, USA, September 9-13, 2013

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Ion Polarization Control in MEIC Rings Using Ion Polarization Control in MEIC Rings Using Small Magnetic Field IntegralsSmall Magnetic Field Integrals

Ya.S. Derbenev 1, F. Lin1, V.S. Morozov 1, Y. Zhang 1,

A.M. Kondratenko 2, M.A. Kondratenko 2 and

Yu.N. Filatov 3,4

1 Jefferson Lab, Newport News, VA2 Science and Technique Laboratory Zaryad, Novosibirsk, Russia

3Joint Institute for Nuclear Research, Dubna, Russia 4Moscow Institute of Physics and Technology, Dolgoprydny, Russia

University of Virginia, Charlottesville, VA, USASeptember 9 - 13, 2013

The XVth International Workshop on Polarized Sources, Targets and

Polarimetry (PSTP 2013)


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1. Introduction

2. Polarization preservation during acceleration in the pre-booster and large booster

3. Deuteron polarization control scheme with “small” solenoids for the collider

4. Proton polarization control with “small” radial fields in the collider

5. Compensation of the 0th harmonic of the spin perturbation in the collider ring. Spin response function and its suppression in the interaction points.

6. Conclusions

Outline


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Schematic Layout of Medium-Energy Electron-Ion Collider (MEIC) at Jefferson Lab

Warm large booster(up to 20 GeV/c)

Warm 3-12 GeV electron collider ring

Medium-energy IPs withhorizontal beam crossing

Injector

12 GeV CEBAF

Prebooster

SRF linac

Ionsource

Cold 20-100 GeV/cproton collider ring

Three Figure-8 rings stacked vertically


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Major Components of MEIC Ion Complex

The MEIC ion beam polarization design requirements are:

• High polarization (over 70%) for protons or light ions (d, 3He++, and possibly 6Li+++).• Both longitudinal and transverse polarization at all IPs.• Sufficiently large lifetime to maintain high beam polarization.• Spin flipping at a high frequency.

to high-energycollider ring

Ionsource

SRF linacPrebooster

(accumulator ring)

Large booster Medium-energy collider ring

Cooling Cooling


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The figure-8 structure provides unique capabilities for manipulating the beam polarization• In an ideal structure (without perturbations) all solutions are periodic• It has an energy-independent (zero) spin tune• It allows control of the beam polarization with small fields without orbit perturbation• It eliminates depolarization problem during acceleration• It becomes possible to efficiently control the polarization of a beam of particles with any

anomalous magnetic moment including particles with small anomalous moments, such as deuterons

• Makes possible ultra-high precision experiments with polarized beams

Spin Motion in “Figure-8” Rings


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Control of Polarization during Acceleration

B||L of only 3 Tm provides deuteron polarization stability up to 100 GeV.

A conventional ring at 100 GeV would require B||L of 1200 Tm or BL of 400 Tm.

The polarization is stable if w0 (w0 is the «zero» spin resonance strength)


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Acceleration and Spin Matching in MEIC

Pre-booster

(1 solenoid)0.785 / 3.83 0.06 / 0.28 60 0.003 / 0.01

Large booster

(1 solenoid)3.83 / 20 0.28 / 1.5 120 0.003 / 0.01

/

(GeV/c)

inj extp p ( ) / ( )

(T m)

sol sol inj sol sol extB L B L

(cm)solL /deut prot

Conventional ~20 GeV accelerators require ~ 70 T m for protons and

~250 T m for deuteronssol solB L


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Control of Deuteron Polarization in Collider Ring

y

yz

sin

)sin(1

yz

sin

sin2

Gy

is the spin rotation angle between the solenoids

is the orbit rotation angle between the solenoids is the angle between the polarization and velocity directions

21, zz are the spin rotation angles in the solenoids

A scheme for obtaining any polarization direction

B

LBG i

zi||1

)( maxminopt

G

Beam injected longitudinally polarized, accelerated and then desired spin orientation adjusted


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Control of Deuteron Polarization in Collider Ring

(B||L)1,2 (Tm) vs. p (GeV/c)

longitudinal polarization radial polarization

(B||L)1

(B||L)2


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Control of Proton Polarization in Collider Ring

Last two arc dipoles(BL)i (Tm) vs. p (GeV/c)

longitudinal polarization radial polarization(BxL)1

(BxL)2

(BxL)3

(BxL)4


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Control of Proton Polarization in Collider RingVertical excursion of the reference orbit


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Spin Response Function

• Zero-harmonic spin resonance strength can be calculated using spin “response function”

• Response function is determined by the accelerator’s design lattice and represents the spin response to a-function perturbation at an azimuthal angle :

dipole

• Such a dipole generates the following strength of the zero-harmonic resonance:

0 ( )dipolew G F

• For a flat figure-8 orbit, the response function is given by2 2

( )4sin( )

y y y yi i i i

y y y y y yy

GF e f K e f d e f K e f d

where0

y yG K d

is the spin rotation angle in the collider’s bending dipoles,

0

expyy

y

Rf d

R

is the Floquet function

and y y are the vertical betatron function and betatron tune

m

dipoledipole mh )2(2


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Response Function in Collider Ring

is the periodic response function describing effect of any radial fields and allowing one to calculate the zero-resonance strength.

)(F

IP

IP

IR

Highest error sensitivity in the IR’s but error control requirements high anyway for dynamic reasons.


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Response Function and Zero Spin Resonance Strength

yB

L

x

Byk

• The total zero-harmonic resonance strength:

is composed of coherent part due to closed orbit excursion due to transverse and longitudinal emittance

• The coherent part

arises due to radial fields from dipole roll vertical quadrupole misalignment

•

., coherentemittanceemittancecoherent0 wwwww

coherentw

emittancew

kkk FGw 0

orbk

2 3rms rms 0 00.1mrad, 0.02mm ~ 10 , ~ 10

P Dy w w


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Compensation of Zero-Harmonic Spin Resonance Strength

• In the linear approximation, the zero-harmonic spin resonance strength is determined by two components of the spin perturbation lying in the ring’s plane:

zx wiwww coherent0

and can be compensated by correcting devices whose spin rotation axis lies in the same plane

-3 -40 emittance 0 0~ | | ~ 10 , | | ~ 10P Dw w w w

insertion for spin control

insertion for strength compensation

insertion for strength compensation

insertion for spin control

• With compensation of the “coherent” component of the spin resonance:


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Conclusions

Schemes were developed for MEIC figure-8 rings that• eliminate depolarization problem during acceleration• allow control of the beam polarization with small fields without significant orbit

perturbation• efficiently control the polarization of particles with any anomalous magnetic

moment including those with small anomalous moments, such as deuterons• allow adjustment of polarization orientation in either of the two straights• allow single-turn as well as multi-turn spin-flipping schemes• make possible ultra-high precision experiments with polarized beams

Future plans• optimization of the developed schemes• integration into the ring lattices• validation by spin tracking• development of spin-flipping techniques


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http://www.jlab.org/conferences/eic2014/index.html

ion polarization control in meic rings using small magnetic fields integrals. pstp 13 v.s. morozov...

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