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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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Polarimetry design updates
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.

Ken Moffeit



Upstream Polarimeter Emittance Growth versus Dispersion

  • Dispersion 5mm > 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

Ken Moffeit


Emittance growth versus dispersion
Emittance Growth versus Dispersion

Mark Woodley

30%

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.

20%

Horizontal Emittance Growth

10%

0

0

20

10

Chicane Dispersion (mm)

Ken Moffeit



Space for laser beam insertion exit

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.

Ken Moffeit



20 mrad extraction line
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?)

Ken Moffeit


Lcws mar 05 yuri nosochkov
LCWS Mar 05Yuri Nosochkov

Improved R22 Optics

Original Optics

Good

bad

Ken Moffeit


Yuri nosochkov 5 april 05
Yuri Nosochkov (5 April 05)

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

Good

Ken Moffeit


2mrad extraction line r22 issues energy and polarimeter chicanes
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

Ken Moffeit


Aligning the compton ip
Aligning the Compton IP Chicanes

Precision surveying should be good to <50 micro radians

Can precision gyroscopes be used to achieve better accuracy?

Perhaps <25 micro radians

Ken Moffeit


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