1. Analysis of 14/20 mrad Extraction Line Energy Chicane
Matthew Sternberg
ILC BDS/GEANT3
Eric Torrence and Matthew Sternberg
University of Oregon
Thanks to Ken Moffeit & Takashi Maruyama
August 29, 2006

2. Spectrometer Layout
•Detector at secondary focus at polarimeter chicane
•90m from Analyzing Dipole to Detector
•70 MeV/100microns at detector
•Secondary electrons detected by Cherenkov radiation

3. 14/20 mrad Extraction Line

4. Detector Schemes +15 +15 -15 -15 Scheme 1
•At least ± .5mrad to achieve adequate separation from bend radiation
•Minimizes background photons
Scheme 2
•Soft bends must be able to achieve adequate separation between hard photons and detector
•Increases photon yield

5. Simulation Details CS11 file from Seryi 34000 Electrons
• Run using Takashi Maruyama’s Geant3 code
•4000 electrons taken periodically throughout CS11 file
•Beam at nominal energy of 250GeV
•Cartoon Dipoles w/o fringe fields
CS11 file from Seryi
34000 Electrons
Mean Energy 244GeV
RMS in x = 0.66µm
RMS in y = 8.5nm
*Apertures from original deck needed some adjustment

6. 20mr Extraction Line Original Layout
Introduce this as original and then show our actual layout
*The soft bends in this layout were of little use

7. 20mr Extraction Line Simulation Layout
Aiming for +_1/2 mrad wiggle

8. Radiation at Detector Plane
Wiggler Stripe
Measuring separation between bands allows for precise measurement of bending without having to know precise position relative to beam
Radiation from quads
Mention saturation
From Polarimeter Chicane
From Energy Chicane Bends

9. Detector Regions and Backgrounds
Background From Bends
Detector Scheme 1
Split into two slides
Detector Signal for 100µm Bins
Green - Full Signal
Blue - Background from bends
Signal to Noise - Starting at peak signal
20:1

10. Detector Regions and Backgrounds
Background From Bends
Detector Scheme 2
Put in Separation distance between detectors, some tradeoff between S/N /3 mrad.
Detector Signal for 100µm Bins
Green - Full Signal
Blue - Background from bends
Cutting out -1.5cm < x < 1.5cm
Signal to Noise - Starting at peak signal
466:1

11. Do Soft Bends Help? Exaggerated Soft Bend Layout

12. Backgrounds at Detector Energy Weighted
Do Soft Bends Help?
No SB
Exaggerated SB
Background
Peak of Wiggler Signal
Backgrounds at Detector Energy Weighted
Switch 2nd two graphs to center of polarimeter chicane. Point out peak wiggler signal
*Mean
Photon : MeV
Energy
*Mean
Photon : MeV
Energy
•Exaggerated 2.5m 500G SB provides an additional 1.5cm of bending
•Photons in this region are still pretty hard
*Mean value taken after peak of wiggler signal

13. Fitting the Dispersion
Detector Scheme 2
•For each incident electron we measure the separation between the average position of photons in upper and lower bands
•Inverse separation is proportional to energy
Fit from 230GeV to 250GeV
≈ y / d
=> E  1/Separation
Residue Against Incident Electron Energy
Mean = MeV
RMS = MeV
Residue Against Electrons in Middle of Energy Chicane
Mean = MeV
RMS = 15.4 MeV
Describe details of how plots are made. Write down dispersion value I.e mm/MeV not fit details. Write rms in big bold. Try seeing the effect of small deviations in the location of detector plane.

14. Data • Softer wigglers reduce energy loss
Chicane Length
Wiggler Strength
Smallest Wiggler Magnet
Photons entering detector for 1010 e-
Average Photon Energy/RMS
Signal/Noise
*RMS of Residue for Incident e-
26 m
2.5KG
75 cm
2.1x1010
6.3/11.1 MeV
30:1
47.5 MeV
5KG
4.2x1010
466:1
61.5 MeV
28 m
100 cm
2.3x1010
3.2/5.7 MeV
78:1
49.5 MeV
6.0x1010
6.5/11.3 MeV
2381:1
66.6 MeV
30 m
125 cm
2.5x1010
3.2/5.6 MeV
318:1
49.3 MeV
7.7x1010 
69.1 MeV
• Softer wigglers reduce energy loss
• Good s/n achievable, signal yield looks good
• No significant dependence on wiggler parameters
26 m case has SB taking up space. This should be rerun using the full space. Smallest wiggler is 40, should be 75cm.
Need to rerun backgrounds for 2m extension (missing top half).
Residue and fits are done from 240GeV to 250GeV.
Get rid of RMS on photon energy.
Get rid of chicane residue (17 MeV)
*Residue and fits are done from 240GeV to 250GeV range of energies

15. Detector Simulations Estimate photon flux on fibers
Compare X-Line Cherenkov flux to
ESA prototype detector

16. BDSIM Code
SLAC A-line dipoles
14 mRad X-Line

17. Simple detector simulation
100 microns
Si02
Cherenkov condition: cosqC = 1/(bn)
200 keV KE e- in Quartz
5 mm Pb
1 cm Al
Cherenkov production ~ 370 <sin2q> photons/cm

18. Incident Photons Aline X-Line <Eg> = 0.6 MeV
• Preradiator doesn’t help in Aline
• Critical Energy ~ 3 <Eg>

19. Transmitted Electrons
Aline
X-Line
<E> = 1.2 MeV
<E> = 6.5 MeV
Electrons/Photons ~ 0.2%
Very time consuming!

20. Cherenkov angle Aline X-Line <sin2q> = 0.37 <sin2q> = 0.52
2 104 Ch. g/1010 e/fiber
~107 Ch. g/1010 e/fiber

22. Further tests in ESA starting this Fall
Conclusions
Need +/- 0.5 mRad horizontal “bumps”
Soft bends of limited usefulness
Detector resolution looks OK
Need more realistic dipole designs
Photon yield appears to be fine in Xline
Further tests in ESA starting this Fall