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
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6 April 05
- 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
Energy and Polarimeter Chicanes
- aligning the Compton IP
Comments about surveying and tolerance for direction at Compton IPs.
Upstream Polarimeter Emittance Growth versus Dispersion
R(20mm) = R(5mm)/4
R3 (20mm)= R3 (5mm)/32
Emittance(20mm) = 45 Emit (5mm)
Slide from Ray Arnold
For eta=20mm & 500 GeV beam:
Short bend has pole-tip field of 5.4 kG;
Long bend is half of that.
Magnets ok for higher dispersion.
Horizontal Emittance Growth
Chicane Dispersion (mm)
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.
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?)
Improved R22 Optics
LCWS Improved R22 Optics
Most Recent Optics
Not Good > 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
R22 ~ 1.3 now
Need R22 ~ 0.5
Expand 2 mrad section to include
Precision surveying should be good to <50 micro radians
Can precision gyroscopes be used to achieve better accuracy?
Perhaps <25 micro radians