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Analysis of the Spin Flipper Its Future Use - PowerPoint PPT Presentation


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RHIC Spin Flipper Commissiong Results and Future Plans. RSC Meeting, June 17 2002, Mei Bai. RHIC polarized proton setup Spin manipulation using a dipole with horizontal oscillating magnetic field Rhic spin flipper commissioning Future plans. RHIC spin flipper. 12:00 o’clock.

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Presentation Transcript
slide2
RHIC polarized proton setup
  • Spin manipulation using a dipole with horizontal oscillating magnetic field
  • Rhic spin flipper commissioning
  • Future plans
rhic polarized proton setup

12:00 o’clock

BRAHMS & PP2PP (p)

PHOBOS

2:00 o’clock

10:00 o’clock

RHIC

PHENIX (p)

8:00 o’clock

4:00 o’clock

STAR (p)

6:00 o’clock

Siberian snakes

U-line

High Intensity Source

AtR

BAF (NASA)

m g-2

HEP/NP

Pol. Proton Source

LINAC

AGS

Siberian snakes

BOOSTER

TtB line

TANDEMS

Au source

RHIC polarized proton setup
  • Two full snakes apart from each

other by 180 in phase

  • Stable spin direction in which

the spin precesses around is

vertical.

  • Spin precession frequency

and is independent of beam

energy. In RHIC, the two snakes’

axes are perpendicular to each

other and the nominal spin tune

is 1/2.

1,2is the angle between the snake

axis and the beam direction

spin motion in the presence of the ac dipole

y

z

x

Spin motion in the presence of the ac dipole
  • Thomas BMT equation

where

A spin resonance then happens when

The strength of this resonance is

For BmL=100 Gauss-m and 100 GeV/c pp, the resonance

strength is 0.00046.

spin manipulation using ac dipole

y

z

x

Spin manipulation using ac dipole
  • In the frame which rotates at the same frequency as the drive frequency, the stable spin direction becomes

where: and

    • fixed drive frequency

-- measure the spin tune

    • crossing through the resonance

-- spin flipping

where ; time to achieve 99.9% spin flip  1 sec

spin flipper commissioning blue ring

0.5 v

6000

0.49

200,000

200,000

6000

6000

6000

0.47

Spin flipper commissioning ------- Blue Ring
  • Setup:
    • snake:
      • inner current=325.06A
      • outter current=106.11A

the predicted spin tune equals to 0.48.

    • Spin flipper:
      • amplitude:
      • frequency

0.00110.000164

0.001950.0002

Bm

0.000840.0002

turns

  • Conclusions:
    • spin flip efficiency 
    • yellow beam
    • The fact that we measured negative asymmetry after we spin-
    • flipped twice in Blue is very hard to understand. This is also
    • consistent with the fact that the yellow beam was actually fully
    • depolarized. while we were spin flipping the blue beam. This
    • suggests that the yellow beam spin tune is away from 0.5.

m

turns

spin flipper commissioning blue ring continue
Spin flipper commissioning ------- Blue Ring (continue)
  • Effect of Spin tune spread
    • spin tune spread:
      • particles with different betatron oscillation amplitude have different spin precession tune
    • to achieve full spin flip, spin tune spread should be less than the spin flipper tune sweeping range.
  • Spin precession tune too close to

the resonance during the amplitude ramping

spin flipper commissioning yellow ring

0.5 v

6000

0.49

200,000

200,000

6000

6000

6000

0.47

Spin flipper commissioning --------- Yellow Ring
  • Setup:
    • snake:
      • inner current=106.9A
      • outer current=323.5A

predicted spin tune equals to 0.48.

    • Spin flipper:
      • amplitude:
      • frequency:

Bm

turns

m

  • Conclusions:
    • No spin flip was achieved in Yellow. Instead, the yellow beam
    • was partially depolarized. This could be because spin tune with
    • the snake setting of (inner106.9A, outer323.5A) doesn’t equal
    • to 0.48.

turns

problems during rhic pp 2002
Problems during RHIC pp 2002
  • Spin flipper
    • The  0.2mm coherent betatron oscillation caused snake quench twice at injection due to the limitation of the aperture.
    • The resolution of the snake WFG.
  • No spin tune measurement
  • Not enough time
plans for the next run
Plans for the next run
  • Measure the spin flipping efficiency in both blue and yellow ring
    • this allows us to assess how well the spin flipper behaves
    • prefer to do the measurement at store.
    • No new instrumentation is needed provided the RHIC CNI polarimeter will be available
  • Measure the spin precession tune to calibrate the snake setting
    • The alternative way to measure the spin tune by measuring the beam polarization before and after turning on the ac dipole at a fixed frequency is to measure the asymmetry while sweeping the ac dipole frequency. The zero crossing of the measured asymmetry is where the spin tune locates. However, this requires to upgrade the current RHIC CNI polarimeter to allow one to measure the beam polarization continuously in couple of seconds.
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