# Presentation: 920767

## Ann Arbor Workshop Highlights

- Experience with Existing Facilities
- AGS depolarization
- Strong Snake
- Weak AGS resonances

## Experience With Existing Facilities (1)

**COSY **(A. Lehrach)
- G(max) = ~ 7; P = 75%
- 50 MeV injection energy;  1e10 protons
- Correction dipoles (spin flip) and tune jump quads,
- Problem: marginal tune jump for strongest intrinsic resonance
**KEK PS **(C. Ohmori)
- 1986 G(max) =   ~ 8.4; P = 40%
- 1988 G(max) = ~ 11.2; P = 25%
- Depolarization in Booster (500 MeV) and PS corrected with sextupole
- Correction dipoles and pulsed quads
- Problem: strong intrinsic resonances, tune jump small

## Experience With Existing Facilities (2)

**1980’s AGS  **(L.A. Ahrens, A.D. Krisch)
- 1986 G(max) = 41.5; P = 45%        60 pi    x,y emittances are exchanged
- 1988 G(max) = 35.5; P = 45%        25 pi
- No Booster;  Intensity about an order of magnitude lower.
- Corrector dipoles and tune jump quads, set-up using polarization info.
- Problem: long tuning time, marginal correctors and tune jump at high Gloss not understood (!)
**1990’s AGS **(TR, H. Huang, M. Bai)
- 2000 G(max) = 46.5; P = 41%
- 2002 G(max) = 46.5; P = 35%
- With Booster, high intensity source
- Partial snake and rf dipole, set-up using beam info.
- Problem: coupling resonances, weak intr. resonances, but loss understood (?)

## Internal Polarimeters

- (C. Ohmori, A. Lehrach, G.M. Bunce)
- KEK (pp elastic [inclusive]): 150 m Carbon target, 220 m polyethylene target, polarization measurement on ramp ( ~ 60 min), ~ 20 min. for 5% measurement
- COSY (pC quasi elastic): 8 m Carbon target, polarization measurement on ramp( 10 - 20 min), few minutes for 5% measurement at flat top
- AGS (old, pC quasi elastic): 7 x 8 m Carbon target (100 m Nylon target), 10 min. for 5% measurement at flat top
- AGS(new, pC CNI): 0.01 m x 500 m Carbon target, polarization measurement on ramp (~ 60 min), 5 seconds for 5% measurement at flat top

## Overcoming AGS Spin Resonances

**	****Imperfection   ****	****Strong Intr.****	****Weak Intr. ****	****Coupl. Res.****	****Set-up info**
- 1980’s 	96 corr. dipoles	10 pulsed quads	10 pulsed quads	N/A	Pol.
- 1990’s	5% solenoid snake	rf dipole	Did nothing	Did nothing	Beam/Pol.
- Plan 1	25% helical snake 	25% helical snake	25% helical snake	N/A	Beam
- Plan 2	5% helical snake	rf dipole	4-8 pulsed quads/	N/A	Beam/Pol.
- 			Intr. spin matching
- Plan 3	5% solenoid snake	rf dipole	4-8 pulsed quads/	Hor. rf dipole (?)	Beam/Pol.
- 			Intr. spin matching

## 25% Partial Snake

- (TR, H. Huang, E.D. Courant, W. MacKay)
- Pro:
**Can overcome depolarization from all resonances**
- (Including sidebands and higher order)
- No tuning based on pol. Measurement
- Con:
- Large perturbation of lattice -> Need additional matching quadrupoles
- Vertical tune close to integer
- Stable spin direction not vertical -> Need injection and extraction spin matching schemes (extraction to RHIC looks OK)
- Never tried before!
- [ Horizontal intrinsic resonance due to horizontal stable spin direction is weak]

## Strong Partial Siberian Snake for AGS 

- A strong partial Siberian snake generates large spin tune gap for G=N. With strong enough snake gap is large enough to cover both imperfection and intrinsic spin resonances.
- Helical snake will not generate coupling spin resonances
- Note: With a strong snake, the stable spin detection will deviate from vertical direction (18 degree for 20% snake).

## Test results with 10% snake at 0 + 

- The difference between the red measurements and blue line is due to the coupling resonance and tilted stable spin direction.
- Good agreement with model.

- AGS injected polarization

- PRELIMINARY

## Modeling of AGS resonances with 20% Snake

**Modeling of AGS resonances with 20% Snake**

- G = 0 + y

- G = 36 + y

- G = 48  y

- “Partial Snake Resonances”
- if sp = n y

- (Tracking by M. Bai)

## ~ 25 % AGS super-conducting helical snake

- 2.6 m

- 15 cm warm bore Helix with changing pitch

## Design of ~ 25% partial snake

- Changing pitch helix
- Horizontal orbit offset
- ~ 4 cm max. excursion
- Central solenoid for coupling correction

## 5% Helical Partial Siberian Snake for AGS 

- Weak helical dipole snake:
- No or little coupling
- Use rf dipole for strong intrinsic resonances
- Use jump or spin matching for weak intrinsic resonances

## AGS normal conducting 5% helical snake

## Full twist helix plus two dipoles

- 1.5 Tesla full twist helix plus two vertical dipoles
- 6 ends -> not enough space

## Design of ~ 5% partial snake

- Changing pitch helix
- with 1.5 T
- ~ 2 cm max. excursion
- -> 1⁄4 of coupling, sextupoles,... of 25%snake
- Central solenoid for coupling correction
- Fits into 10-foot SS (I10)

- - 2

-     2

-   0

- 0.02

- 0.00

- - 0.02

## Overcoming weak intrinsic resonances

**Betatron tune jump**( M. Bai, A.D. Krisch):
- Works well up to  ~ 0.002, rise time: 10 – 100 s
- Possible beam emittance growth
**Harmonic spin matching** (A. Lehrach, V. Ranjbar):
- Tested at COSY. 12 quads in location 15 (and/or 5) -> zero res. strength
-  0.25 tune variations
**Energy jump**:
- Inexpensive, jump speed too small
**Rf spin rotator**: (D.W. Sivers)
- Requires too strong rf magnets

- ~ 300 A

## Proposed Plan

- Build warm helical 5% snake w/o coupling for installation before Run 4
- No coupling resonances (~ + 20 % pol.)
- Install quads in #15 straight sections with power supply before Run 4
- Reduced weak intrinsic resonance strength (~ +10% pol.)
- Explore possibility of using jump quads
- Eliminate depolarization from weak resonances (~ +15%)
- Build cold helical 25% snake w/o coupling for installation before Run 5 or maybe Run 6
- Will take time to commission, large effect on orbit properties
- Can eliminate depolarization from all resonance.
- Only alternative method to overcome strong intrinsic resonances(Intensity effects and other sources of tune spread can effect rf dipole method!)