Embed Size (px)
DESCRIPTION
Beam Energy Determination via Spin Dancing. Review Spin Precession In The CEBAF Accelerator Two Hall Spin Dance Single Hall Spin Dance Study of systematics underway by SULI student . Spin Precession At CEBAF. Example CEBAF Setup. - PowerPoint PPT Presentation
Citation preview
Douglas Higinbotham - 12 June 2013
Beam Energy Determinationvia Spin Dancing
• Review Spin Precession In The CEBAF Accelerator• Two Hall Spin Dance• Single Hall Spin Dance• Study of systematics underway by SULI student
Douglas Higinbotham - 12 June 2013
Spin Precession At CEBAF
Douglas Higinbotham - 12 June 2013
Example CEBAF SetupSelect a beam energy and Wien angle based on physics requirements of the Halls (63.5 MeV Injector Energy and 565 MeV Per Linac Per Pass)
• Machine setup with balanced or energy match linacs.• Hall C required polarization (GEP-III) and Hall’s A & B requested polarization.
Douglas Higinbotham - 12 June 2013
Imbalanced Linacs
• With imbalanced the linacs, we were able to boost the polarization.• 10 MeV was removed from the North linac and 10 MeV was added to the South linac.
Needed to give Hall A & C high polarization without changing the beam energy for Hall B. (63.5 MeV Injector Energy and 555 MeV & 575 MeV Per Linacs)
Douglas Higinbotham - 12 June 2013
Magic CEBAF Energy (2.12 GeV/pass)
A
B
C
South Linac
-37,5168°
37,5°
1st 2.12 GeV2nd 4.23 GeV3rd 6.35 GeV4th 8.46 GeV5th 10.6 GeV
1st Pass
-1
-0,5
0
0,5
1
-180 -130 -80 -30 20 70 120 170
Wien Angle (°)
Inje
cted
Lon
gitu
dina
l % o
f Po
lariz
atio
n Hall A, 1Hall B, 1
Hall C, 1
3rd Pass
-1
-0,5
0
0,5
1
-180 -130 -80 -30 20 70 120 170
Wien Angle (°)In
ject
ed L
ongi
tudi
nal %
of
Pola
rizat
ion Hall A, 3
Hall B, 3
Hall C, 3
4th Pass
-1
-0,5
0
0,5
1
-180 -130 -80 -30 20 70 120 170
Wien Angle (°)
Inje
cted
Lon
gitu
dina
l % o
f Po
lariz
atio
n Hall A, 4
Hall B, 4
Hall C, 4
2nd Pass
-1
-0,5
0
0,5
1
-180 -130 -80 -30 20 70 120 170
Wien Angle (°)
Inje
cted
Lon
gitu
dina
l % o
f Po
lariz
atio
n Hall A, 2Hall B, 2Hall C, 2
5th Pass
-1
-0,5
0
0,5
1
-180 -130 -80 -30 20 70 120 170
Wien Angle (°)
Inje
cted
Lon
gitu
dina
l % o
f Po
lariz
atio
n Hall A, 5Hall B, 5Hall C, 5
At 2.12 GeV per pass, the passes give full polarization the all three of the current halls.
Douglas Higinbotham - 12 June 2013
Measurements of Angle Between Halls
• Doesn’t matter how accelerator gives the beam energy (balanced, imbalanced, off-crest, etc.)
• The electron g-factor is one of the most precisely measured values in physics, with its uncertainty beginning at the twelfth decimal place.
Douglas Higinbotham - 12 June 2013
Energy By Precession Differences
Repeat this same result at 11 GeV has a factor of two better sensitivity; so can be better then 4 or 5E-4 level absolute.
Of course, Hall A and C give smallest errors since the opening angle between them is twice as large as A and B or B and C.
J. M. Grames et al., Phys. Rev. ST Accel. Beams 7 (2004) 042802.
Douglas Higinbotham - 12 June 2013
Measurement of total precession• At 11 GeV, the beam processes ~20k degrees
before arriving in Hall A.• 2 MeV of beam energy change (balanced) is a
5 degree change in the precession.• Sine wave phase can be determined to the
degree level with Compton (~8 hrs)• That would be 9E-5 !! dE/E even with just a
single hall • BUT accelerator systematics have to be under
control (Summer project underway)
Douglas Higinbotham - 12 June 2013
Energy From Total Precession
Nice agreement between the Hall A and C high polarimeters.
NOTE: The Hall A and C polarimeters receive more attention to systematics then the Hall B polarimeter due to the requirements of the experiments (e.g. Qweak, HAPPEX, etc.).
(e.g. possibility that there is a small angular misalignment of the Hall B polarimeter)
Even so, full spread these results is only 2 MeV ( 5648 +/- 1 MeV) which already 2E-4 level.
J. M. Grames et al., Phys. Rev. ST Accel. Beams 7 (2004) 042802.
Douglas Higinbotham - 12 June 2013
New Spin Calculator AppSULI Student Gina Mayonado
Douglas Higinbotham - 12 June 2013
Summary• Looking for multiple ways to determine the energy of the beam with high precision and accuracy.
• ARC Energy Measurements once fully operational during 6 GeV provided:o 5E-4 dE/E non-invasive o 2E-4 dE/E invasiveo 12 GeV Magnet Measurements have been completedo Magnets within 1E-4 of each other.
• Another technique that can hit this level of precision is spin dancingo Hall A & C Dancing minimizes systematic errors o Single Hall Dance at 11 GeV seems promising but systematically challenging
