# Presentation: 118588

## News from AGS Polarized Protons Run

- Haixin Huang
- Mar. 19, 2004

- H. Huang

## Depolarizing Resonances in the AGS  

**Imperfection Resonances**
-      arising from sampling of error fields, fields due to closed orbit errors, etc.
-              G=n (integer)   G=5,6,...46	partial snake
-          **Intrinsic Resonances**
-               arise from sampling of focusing fields due to finite beam emittance.
-               G=kPy
-               Strong ones: G=0+y,12+y,36y; AC dipole
-               Weak ones: G=24y,48-y      crossing speed as fast as possible
-          **Coupling Resonances**
-                 horizontal betatron motion coupled to the vertical betatron motion by
-                 some coupling elements: solenoid
-                 G=kPx   G=0+x,12+x,36x	Crossing speed as fast as possible Polarization after passing an isolated resonance with strength  and crossing speed  =Gd/d is given by  Froissart-Stora Formula:
-             Pf/Pi=2exp[-||2/(2)]-1
-               ||2/(2)<<1, Pf/Pi1;
-               ||2/(2)>>1, Pf/Pi-1.

- Haixin Huang

## AGS Helical Warm Snake

- Funded by RIKEN.
- With the new warm snake, coupling between the two transverse motions are greatly reduced. We don’t need to compromise snake strength anymore.
- The commission of the new warm helical snake started March 5 with proton beam.
- Magnet has been run in the ring at 2700A.

- Haixin Huang

## AGS closed orbit  with snake on 

**Snake**

**Orbit  in the snake**
**With full current**
**(from Junpei)**

- Haixin Huang

## AGS tunes with snake on/off 

******x**** =8.82,  ********y**** =8.687 **

**Snake on:**
******x**** =8.88,  ********y**** =8.741**

**AGS tunes with snake on/off**

- Haixin Huang

## AGS intensity with snake on/off 

**Snake off**

**Snake on**

**Better life time**

- Haixin Huang

## Job List 

- Establish beam in AGS extraction with good intensity. 
- Calibrate the Gauss Clock Counts for the new main magnet function to set the timing of AC dipole pulses. 
- Careful tune optics to give healthy AC dipole pulses to overcome four strong intrinsic resonances, which include vertical and horizontal tunes, vertical and horizontal chromaticities. 
- Adjust the driving tunes for all four ac dipole pulses to maximize the ac dipole driving field. 
- Correct orbit with the helical snake on and minimize the coupling with skew quads. 
- Booster harmonic scan to eliminate polarization loss in the Booster. 
- AC dipole pulse timing scan at various resonances.
- Fine tune the ac dipole pulses to eliminate emittance growth if any.
-  Correct 8th and 9th harmonics along the ramp.

- Haixin Huang

## Polarization at G=7.5 

- Polarization at G=7.5 was measured as 77+-1.8(stat)+-4.7(sysm)% with E880 polarimeter. The sign is flipped from injection as expected. If assuming the analyzing power is proportional to 1/p, the polarization at injection can also be estimated.
- G=4.5 is better than G=4.7 or better polarization from the source?

| Energy | Polarization  | 200MeV Polarization | Pol. Last year |
| --- | --- | --- | --- |
| 7.5 | (77.0+-1.8+-4.7)% | (71.4+-0.6)% | (73.6+-0.4+-4.5)% |
| 4.5/4.7 | (-74.1+-1.4+-4.5)% | (72.3+-0.7)% | (-71.5+-1.9+-4.5)% |

- Haixin Huang

## Difference this year 

- Of course the new warm snake. Much less coupling from this snake. There are several benefits:
- We can run the snake as strong as we want without concerning the  coupling resonances.
- The effect from horizontal dimension is small, so less parameters to worry about (horizontal emittance, horizontal tunes).
- Faster Bdot (faster resonance crossing rate).
- No scraping in the Booster (higher intensity easily)
- CNI polarimeter perform well with the higher intensity.

- Haixin Huang

## Polarization at G=46.5 

- 0.1+-2.5% with snake off, ac dipole on.
- 0.4+-2.5% with snake on, ac dipole off.
- One single comparison between CNI and E880: 32.3+-2.3% vs. 32+-5%.
- With each of the ac dipole on/off measurement(before reaching 44% in AGS, about 30% at the time), the vertical emittance can be estimated.
- It suggests that there is no effect from 36+ y: timing is off, driving tune is off, emittance too large.

| Resonance | Flip Efficiency | Emittance |  |
| --- | --- | --- | --- |
| 0+ y  | -0.600 | 16.2  | Not well corrected? |
| 12+y  | 0.633 | 7  |  |
| 36-y  | -0.198 | 7.5 |  |
| 36+y  | -0.96 | 58 | Not well corrected |

- Haixin Huang

## Polarization at AGS extraction vs. B field 

**Polarization at AGS extraction vs. B field**

**p,B,r,f**

**44%**

**~80G**

**200G~ 1 unit Ggamma**

**55- **y

**39+ **y

- Haixin Huang

## Comment 

- A_N has been raised by 10% from last year.
- The polarization seems more stable comparing to last year.
- The relative shift of plateau between last year and this year is understandable, since the energy is determined by both B field and radius.
- Spin sign should flip every unit of G, or about 200G. In between, when the beam energy stays at weak resonance at 46.3 (55-y ) and 46.7 (39+ y ), beam can be depolarized. This distance should be about 80G. Since this is an incomplete field scan, the full structure is not seen in this plot.
- The plateau of high polarization is smaller this year. This may indicates that the strength of all resonances are enhanced by the new warm snake.

- Haixin Huang

## AGS Parameters  

|  | Last Year | So Far This Year |
| --- | --- | --- |
| Polarization | 45+-2.6% | 44+-2.3% (10% higher AN) |
| Intensity | 0.6*1011 | 1.1*1011 |
| Vertical Emittance | 6  | 7 ? |
| Horizontal Emittance | 12  | 30  |
| Coherence at 0+ | 9.8mm | 10mm |
| Coherence at 12+ | 8mm | 7mm (weaker and shouldn’t) |
| Coherence at 36- | 5.3mm | 5.5mm |
| Coherence at 36+ | 5.5mm | 6mm |
| Snake Strength | 4% early 5% later | 8% injection, 6% top |

- Haixin Huang

## What Else Will We Do?

- Timing scan for each resonance.
- Optimize the coherence at each intrinsic resonance, the coherence monitor just available on Tuesday.
- Avoid emittance blow up if any ( no vertical profile measurement before today); minimize vertical emittance.
- Higher extraction energy? (to increase resonance crossing rate at 36+, but it is less an issue if no coupling resonance around)
- Correct orbit along the ramp. (less important with 6% snake and little coupling)
- Ramp measurement to make sure there is no drop of polarization at 36+ and find out where we lose polarization.
- Use the new foil in LTB to reduce the emittances.
- Explore relation between polarization and both horizontal and vertical emittances.
- Explore relation between polarization and beam intensity.
- Explore multiple bunch injection scheme.

- Haixin Huang