acceleration of the polarized proton beam in the ags with multiple partial siberian snakes

Acceleration of the polarized proton beam in the AGS with multiple partial Siberian snakes

Junpei Takano

1. Spin Physics

We have “the proton spin crisis”.Proton spin is not equal to “two up quarks” + “down quark”.

The proton spin depends on the gluon??

up quark

down quark

gluon

Proton spin

BNL has the polarized proton accelerator complex.

RBRC researches the polarization of the gluonfrom this high energy polarized protons collision.

1. Spin Physics

BRAHMS & PP2PP (p)

STAR (p)PHENIX (p)

AGS

LINAC BOOSTER

Pol. Proton Source500 A, 300 s

Spin RotatorsSolenoid Snake

Siberian Snakes

200 MeV Polarimeter

AGS pC CNI PolarimeterAC Dipole

RHIC pC Polarimeters

Absolute Polarimeter (H jet)

RHIC

Siberian Snakes

Cold Snake

Warm Snake

2. Acceleration of polarized proton beam

LINACBOOSTERPol. Proton Source

500 A, 300 s

200 MeV Polarimeter

2. Acceleration of polarized proton beam

80% polarized proton is provided

No depolarization in this sections

BRAHMS & PP2PP (p)

STAR (p)PHENIX (p)

Spin Rotators

Siberian Snakes

RHIC pC PolarimetersAbsolute Polarimeter (H jet)

RHIC

Siberian Snakes

2. Acceleration of polarized proton beam

All depolarizing resonances are overcomeby Full (100%) Siberian Snakes

AGSSolenoid Snake (5%)

AGS pC CNI Polarimeter

AC Dipole

Cold Snake (1.5~2.5T, 5~15%)

Warm Snake (1.5T, 5.89%)

2. Acceleration of polarized proton beam

AGS Partial Snakes

AGS has imperfection res. and intrinsic res.

Imperfection res.νs (spin tune) = Gγ = integerwhere G = (g-2)/2 = 1.7928 in the proton case

Weak partial snake is enough to overcomebefore 2004: solenoid snake → Coupling res.after 2004: warm snake

Intrinsic res.νs = Gγ = kP±νy

where k is integer, P is super periods (P=12 for AGS),νy is vertical tune (~8.95 in AGS)

by using AC dipole or strong partial snakecold snake was installed in 2005

Coupling res.νs = Gγ = kP±νx (νx=8.6 in AGS)

3. Siberian Snake for overcoming depol. res.

Warm Snake2. Acceleration of polarized proton beam

Cold Snake2. Acceleration of polarized proton beam

Formula of spin tune and Siberian snake strengthcosπνs ＝ cos(δ/2) cosπGγwhere δ is the angle which snake can tilt

3. Siberian Snake for overcoming depol. res.

3. Siberian Snake for overcoming depol. res.

0 10 20 30 40 504

6

8

10

12

14

16

18

20

22

24Sn

ake

stre

ngth

[%

]

G

CSNK_1.5T CSNK_2.0T CSNK_2.5T SSNK WSNK

Snake strength of the AGS partial Siberian snakes

Snake strength depends on the beam energy.

Injection Extraction

20 25 30 35 40 45 50-0.002

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014A

sym

met

ry

G

RUN4 RUN3

36+v

48-v36-v 24+v

12+v

-7.2% +1.5% +4.6% -0.5% -8.2%

-17.5%-8.3%-6.9%-13.4%N/A

RUN4

RUN3

3. Siberian Snake for overcoming depol. res.

3. Siberian Snake for overcoming depol. res.

Total asymmetry drop at the intrinsic res. In RUN4 = -1.6%Total asymmetry drop at the intrinsic res. In RUN3 = -46.1%

Polarization at the AGS flat top in RUN3 = 40%Polarization at the AGS flat top in RUN4 = 50%

The warm snake increases the polarization 25%

Results of RUN4

Locations of the snakes in the AGS

Cold Snakeat A20

Warm Snake at E20

4. Double partial snakes scheme

1/3 of the ring

Merit 1: making the spin tune gap bigger at the intrinsic resonances

Merit 2: decreasing the spin mismatch at the injection and extraction

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

37 38 39 40 41 42 43 44 45 46 47Ggamma

spin

tun

e

WSNK+CSNKWSNKIntrinsic res.

4. Double partial snakes scheme

Large spin tune gap Gγ= 3k k: integerIntrinsic res. νs = Gγ= 12k±νy

48-νy 36+νy

WSNK=6%CSNK=10%

Extraction energy

Large spin tune gap

4. Double partial snakes scheme

Spin tune around injection energy and first intrinsic resonance

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

4 5 6 7 8 9 10Ggamma

spin

tun

e

WSNK+CSNKWSNKIntrinsic res.

WSNK=8.4%CSNK=16%

0+νy

Injection energy

Large spin tune gap

4. Double partial snakes scheme

SSD at Ggamma=4.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 L20L20 A20 E20C20

WSNK = 8.4%

Spin mismatch

Injection energy

Vertical component at L20 = 0.991

SSD at Ggamma=46.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 L20L20 A20 E20C20

4. Double partial snakes scheme

Vertical component at H10 = 0.996

Spin mismatch

WSNK = 6% Extraction energy

SSD at Ggamma=4.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 L20L20 A20 E20C20

4. Double partial snakes scheme

Spin mismatch

CSNK = 16% Injection energy

Vertical component at L20 = 0.969

SSD at Ggamma=46.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 L20L20 A20 E20C20

4. Double partial snakes scheme

Spin mismatch

CSNK = 10% Extraction energy

Vertical component at H10 = 0.988

SSD at Ggamma=4.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 L20L20 A20 E20C20

4. Double partial snakes scheme

Spin mismatch

CSNK = 16%, WSNK = 8.4% Injection energy

Vertical component at L20 = 0.992

SSD at Ggamma=46.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 L20L20 A20 E20C20

4. Double partial snakes scheme

Spin mismatch

CSNK = 10%, WSNK = 6% Extraction energy

Vertical component at H10 = 0.998

4. Double partial snakes scheme

Ver. comp. WSNK1.5T CSNK2.5T W1.5T+C2T

Injection 0.991 0.969 0.992

Extraction 0.996 0.988 0.998

WSNK only: small spin mismatchCSNK only: spin mismatch comes worseWSNK + CSNK: small spin mismatch

Stronger CSNK makes spin mismatch bigger.

Cold Snake Strength (%)

0 5 10 15 20 25 30 35

Asy

mm

etry

(*1

0-3)

52

54

56

58

60

62

64

66

Asymmetry at Gγ=4.5 (Injection energy)

5. Results of RUN5

Calculated curve

Spin mismatch were measured at injection energy

5 10 15 20 25-0.10

-0.05

0.00

0.05

0.10R

aw A

sym

met

ry

Ggamma

RUN4(WSNK+ACdipole) RUN5(WSNK+CSNK2T) RUN5(CSNK2.5T)

12+v

0+v

5. Results of RUN5

Effect of AC dipole

25 30 35 40 45 50

-0.02

-0.01

0.00

0.01

0.02R

aw A

sym

met

ry

Ggamma

RUN4(WSNK+ACdipole) RUN5(WSNK+CSNK2T) RUN5(CSNK2.5T)

36+v

36-v

5. Results of RUN5

Effect of AC dipole

CSNK15%

WSNK5%

CSNK10%

WSNK5%

CSNK15%

WSNK0%

AC dipole

WSNK5%

_x ( mm-mrad) 12 11 13 25

_y( mm-mrad) 13 15 13 10

Vert. aperture limit No No Yes Limited at 0+

Hori. aperture limit Yes Yes No No

Polarization 52.5% 56.4% 55.1% 57.6%

Intensity (1011) 0.4 0.7 1 1

Difficulty intensity intensity Raise Qy 0+ V. aperture

5. Results of RUN5

All intrinsic resonances are overcome by the Cold Snake without AC dipole

5. Results of RUN5

2002 2003 2004 20050

10

20

30

40

50

Pola

riza

tion

[%

]

2002 2003 2004 20050

100

200

300

400

500

600

Figu

re o

f M

erit

(L

P4 )

Polarization in RHIC100GeV vs. 100GeV

AGSSolenoid Snake (I10)

Cold Snake (A20) Warm Snake (E20)

If the Solenoid Snake is movedfrom I10 to I20....

6. Three partial snakes scheme

6. Three partial snakes scheme

SSD at Ggamma=4.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 I20 L20L20 A20 E20 I10C20

CSNK = 16%, WSNK = 8.4%, SSNK = -7.6% Injection energy

No spin mismatch

6. Three partial snakes scheme

SSD at Ggamma=4.5

-1.2-1

-0.8-0.6-0.4-0.2

00.20.40.60.8

11.2

AGS location

spin

com

pon

ent

n_x

n_y

n_z

C15 H10 I20 L20L20 A20 E20 I10C20

No spin mismatch

CSNK = 10%, WSNK = 6%, SSNK = 4% Extraction energy

6. Three partial snakes scheme

0%

10%

injection

extraction

ramp upS

SN

K s

tren

gth

%

-7.6%

4%

The current at injection is negative for no spin mismatch.Then the current should be turned to positive for making spin tune large, but the bipolar PS is needed in this case.

6. Three partial snakes scheme

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

4 5 6 7 8 9 10

Ggamma

spin

tun

e WSNK+CSNK+SSNKWSNK+CSNKWSNKIntrinsic res.

CSNK=16%WSNK=8.4%SSNK= 10%

Large spin tune gap

Injection energy

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

40 41 42 43 44 45 46 47

Ggamma

spin

tun

e WSNK+CSNK+SSNKWSNK+CSNKWSNKIntrinsic res.

6. Three partial snakes scheme

CSNK=10%WSNK=6%SSNK= 4%

Large spin tune gap

Extraction energy

7. Summary

Warm Snake has been installed in RUN4 Polarization was improved to 50% at extraction of AGS

Cold Snake has been installed in RUN5 2snakes scheme had been worked All intrinsic resonances are overcome by Cold Snake Spin mismatch at injection was measured

3snakes scheme for no spin mismatch was calculated3snakes scheme can help the spin tune gap larger

Special thanks

L. Ahrens, M. Bai, E. D. Courant, J. W. Glenn, H. Huang, F. Lin,A. U. Luccio, W. W. MacKay, T. Roser, N. Tsoupas, J. Woodsand all members in Main Control Room in BNL

M. Okamura / RIKEN

T. Hattori / TITECH