Polarimetry Design Updates

1
Polarimetry Design Updates
IPBI Meeting 6 April 05 Ken Moffeit
- Dispersion in upstream chicane -
20mrad extraction line 0.75 mrad beam stay
clear location of Synchrotron Radiation Stripe
Detector Comments about Shielding Number of
Cells for Cerenkov Detector Better R22 etc
- 2mrad extraction line R22 issues Energy
and Polarimeter Chicanes - aligning the
Compton IP Comments about surveying and
tolerance for direction at Compton IPs.
2
Upstream Polarimeter with Dispersion 5 mm
3
Upstream Polarimeter Emittance Growth versus
Dispersion

• Dispersion 5mm gt 20mm
• 2 is 16 times larger
• R(20mm) R(5mm)/4
• R3 (20mm) R3 (5mm)/32
• Emittance(20mm) 45 Emit (5mm)

Slide from Ray Arnold
4
Emittance Growth versus Dispersion
Mark Woodley
30
For eta20mm 500 GeV beam Short bend has
pole-tip field of 5.4 kG Long bend is half of
that. Magnets ok for higher dispersion.
20
Horizontal Emittance Growth
10
0
0
20
10
Chicane Dispersion (mm)
5
Upstream Polarimeter with dispersion 10 mm
6
Space for Laser Beam Insertion/exit

• Only 1.4 meters between the inner dipoles is
  unacceptable. Peter Schuler needs a nominal 8
  meters of space (or 14 meter between magnet
  centers) for the laser beam insertion/exit.
• This is to accomodate a crossing angle of 10
  mrad, and keep the optics away from any
  synchrotron radiation.
• These conditions accomodate a vertical beam
  crossing, but retain a minimal magnet gap height
  of only 20 mm for all dipoles.

7
10 mm dispersion and 8m for laser input
8
20 mrad Extraction Line
Eight Cerenkov Cells 1 cm wide Six cover the
region between 36 GeV (12 cm from beam line)
25.1 GeV (17.8 cm) And 2 outside the kinematic
limit
Location of Synchrotron Detector
Cerenkov Detector Shielding issues Cells closest
to beam pipe will see Synchrotron Radiation
(below 10 MeV?)
9
LCWS Mar 05 Yuri Nosochkov
Improved R22 Optics
Original Optics
Good
bad
10
Yuri Nosochkov (5 April 05)
LCWS Improved R22 Optics
Most Recent Optics
Not Good gt Lose 1cm at Cerenkov Det 1st Cell
starts at 13 cm instead of 12 cm 2 mrad
synchrotrotron swipe barely gets out of 0.75 mrad
beam stay clear
Good
11
2mrad extraction line R22 issues Energy and
Polarimeter Chicanes
Optics Improvement R22 1.3 now Need R22 0.5
Expand 2 mrad section to include Energy
chicane Polarimeter chicane
12
Aligning the Compton IP
Precision surveying should be good to lt50 micro
radians
Can precision gyroscopes be used to achieve
better accuracy? Perhaps lt25 micro radians