1. Final Focus Synchrotron Radiation
M. Sullivan
for the
JLEIC Collaboration Meeting
Mar , 2016

2. JLEIC Collaboration Meeting Mar. 2016
Outline
Brief Introduction
Beam parameters
SR from the final focus elements
Synchrotron Radiation backgrounds
Results from 3 accelerator options
Total photons and power from FF SR
Smaller IP beam pipe?
Summary
Conclusion
JLEIC Collaboration Meeting Mar. 2016

3. JLEIC Collaboration Meeting Mar. 2016
Accelerator
The EIC accelerator design(s) have large beam energy range(s) for both beams
5-20 GeV for e-
GeV for the ions
This flexibility must be carefully observed when designing IR details
SR for the electron beam is a good example
JLEIC Collaboration Meeting Mar. 2016

4. Electron IR Parameters
JLEIC current baseline design parameters
Electron beam
Energy range GeV
Current (5/10 GeV) 3/0.7 A
Beam-stay-clear beam sigmas
Emittance (x/y) (5 GeV) (14/2.8) nm-rad
Emittance (x/y) (10 GeV) (56/11) nm-rad
Betas
x* = 10 cm x max = 300 m
y* = 2 cm y max = 325 m
Final focus magnets
Name Z of face L (m) k G (10 GeV-T/m)
QFF
QFF
QFFL
JLEIC Collaboration Meeting Mar. 2016

5. JLEIC Collaboration Meeting Mar. 2016
Ion IR Parameters
Proton/ion beam
Energy range GeV
Beam-stay-clear beam sigmas
Emittance (x/y) (60 GeV) (5.5/1.1) nm-rad
Betas
x* = 10 cm x max = m
y* = 2 cm y max = m
Final focus magnets
Name Z of face L (m) k G (60 GeV)
QFF
QFF
QFFL
JLEIC Collaboration Meeting Mar. 2016

6. Final Focus SR backgrounds
We need to check background rates for various machine designs
The large JLEIC flexibility (5-10 GeV for electrons) makes building a single IR beam pipe challenging
The 5 GeV e- design has the highest beam current
The 10 GeV design has the highest SR photon energies and the largest beam emittance
JLEIC Collaboration Meeting Mar. 2016

7. JLEIC Collaboration Meeting Mar. 2016
Final Focus Sources
Generic Final Focus optics
The X focusing magnets are outside of the Y focusing magnets
For flat beams the magnets do not fight each other
Round beam optics have much stronger magnets making them much larger SR sources
JLEIC is closer to round
JLEIC Collaboration Meeting Mar. 2016

8. JLEIC Collaboration Meeting Mar. 2016
Beam pipe Surfaces
We have chosen 4 Beam pipe surfaces to monitor
Upstream beam pipe inside the final focus elements (-3 m to -4 m)
Central IP beam pipe mask at (-1 to -2 m)
Important for calculating forward scattering
Central beam pipe (3 cm radius) (upstream section 0 to -50 cm)
Central beam pipe (downstream section +50 cm to 0)
JLEIC Collaboration Meeting Mar. 2016

9. JLEIC Collaboration Meeting Mar. 2016
Baseline Optics
JLEIC Collaboration Meeting Mar. 2016

10. JLEIC Collaboration Meeting Mar. 2016
Option 1
JLEIC Collaboration Meeting Mar. 2016

11. JLEIC Collaboration Meeting Mar. 2016
Option 2
JLEIC Collaboration Meeting Mar. 2016

12. Beam pipe and beam distribution
In order to compare pineapples to pineapples we have kept the beam pipe design constant between optics options
For SR monitoring we trace beam particles out to 10  in x and 25  in y with a beam tail distribution
Program used is SYNC_BKG. Originally QSRAD created by Al Clark of LBL (~1983). Designed exclusively for FF SR.
JLEIC Collaboration Meeting Mar. 2016

13. JLEIC Collaboration Meeting Mar. 2016
Cases Studied
We have looked at 12 different cases:
3 Optics designs
Original
Option 1
Option 2
2 beam energies
10 GeV
5 GeV
2 emittances
Regular (56/11 nm 10 GeV and 14/2.8 nm 5 GeV)
Reduced (39/7.7 nm 10 GeV and 9.8/2.0 nm 5 GeV)
JLEIC Collaboration Meeting Mar. 2016

14. Baseline  from Fanglei Lin e- 2.4 m *=(10,2)cm
0.5 m, 16 T/m, good field r = 4 cm, rinner = 5 cm, router = 10 cm
1 m ion spectrometer 
0.7 m, 44 T/m, good field r = 2 cm, rinner = 3 cm, router = 7 cm
0.7 m, 45 T/m, good field r = 4 cm, rinner = 5 cm, router = 10 cm
Max. x= 4.1 mm
*=(10,2)cm
x= 2.1 mm
x= 3.4 mm
from Fanglei Lin
JLEIC Collaboration Meeting Mar. 2016

15. Option 1  from Fanglei Lin e-
Beam sizes at FFQ locations are calculated using the baseline design emittances
Field gradients are 10 GeV (divided by 5 GeV)
2.6 m e-
0.5 m, 29 T/m, good field r = 4 cm, rinner = 5 cm, router = 11 cm
1 m ion spectrometer 
0.7 m, 44 T/m, good field r = 3 cm, rinner = 4 cm, router = 8 cm
0.9 m, 42 T/m, good field r = 4.5 cm, rinner = 5.5 cm, router = 11 cm
*=(10,2)cm
5 GeV: x,y = (1.6,0.9) mm
10 GeV: x,y = (3.2,1.8) mm
5 GeV: x,y = (2.0,0.8) mm
10 GeV: x,y = (3.9,1.6) mm
5 GeV: x,y = (2.2,0.7) mm
10 GeV: x,y = (4.4,1.4) mm
Note that, beam sizes in the above plot are given at locations with maximum horizontal beta functions (i.e. maximum horizontal beam sizes) in the FFQs. One has to calculate the maximum vertical beam sizes if they are desired.
from Fanglei Lin
JLEIC Collaboration Meeting Mar. 2016

16. Option 2  from Fanglei Lin e-
Beam sizes at FFQ locations are calculated using the baseline design emittances
Field gradients are 10 GeV 
*=(10,2)cm e-
0.5 m, 28 T/m, good field r = 4.5 cm, rinner = 5.5 cm, router = 12 cm
1 m ion spectrometer
0.7 m, 40 T/m, good field r = 3 cm, rinner = 4 cm, router = 8 cm
0.7 m, 46 T/m, good field r = 5 cm, rinner = 6 cm, router = 11 cm
10 GeV: x,y = (2,2) mm
2.4 m
0.3 m, 14 T/m (permanent), good field r = 2 cm, rinner = 3 cm, router = 5 cm
10 GeV: x,y = (3.1,2.2) mm
10 GeV: x,y = (4.9,1.6) mm
10 GeV: x,y = (4.4,1.7) mm
Note that, beam sizes in the above plot are given at locations with maximum horizontal beta functions (i.e. maximum horizontal beam sizes) in the FFQs. One has to calculate the maximum vertical beam sizes if they are desired.
from Fanglei Lin
JLEIC Collaboration Meeting Mar. 2016

17. JLEIC Collaboration Meeting Mar. 2016
Reminder
JLEIC Collaboration Meeting Mar. 2016

18. JLEIC Collaboration Meeting Mar. 2016
Surface a (10 GeV)
10 GeV >10 k >50 k W
Bas. High Emit <.1
Opt 1 High Emit e e
Opt 2 High Emit e e
Bas. Red. Emit
Opt 1 Red. Emit
Opt 2 Red. Emit e e
JLEIC Collaboration Meeting Mar. 2016

19. JLEIC Collaboration Meeting Mar. 2016
Surface a (5 GeV)
5 GeV >10 k >50 k W
Bas. High Emit
Opt 1 High Emit
Opt 2 High Emit e e
Bas. Red. Emit
Opt 1 Red. Emit
Opt 2 Red. Emit e e
JLEIC Collaboration Meeting Mar. 2016

20. JLEIC Collaboration Meeting Mar. 2016
Surface b (10 GeV)
10 GeV >10 k >50 k W
Bas. High Emit e e
Opt 1 High Emit e e
Opt 2 High Emit e e
Bas. Red. Emit e e
Opt 1 Red. Emit e e
Opt 2 Red. Emit e e
JLEIC Collaboration Meeting Mar. 2016

21. JLEIC Collaboration Meeting Mar. 2016
Surface b (5 GeV)
5 GeV >10 k >50 k W
Bas. High Emit e
Opt 1 High Emit e
Opt 2 High Emit e e
Bas. Red. Emit e
Opt 1 Red. Emit e
Opt 2 Red. Emit e e
JLEIC Collaboration Meeting Mar. 2016

22. JLEIC Collaboration Meeting Mar. 2016
Surface c (10 GeV)
10 GeV >10 k >50 k W
Bas. High Emit e e
Opt 1 High Emit e
Opt 2 High Emit
Bas. Red. Emit e
Opt 1 Red. Emit
Opt 2 Red. Emit <0.01
JLEIC Collaboration Meeting Mar. 2016

23. JLEIC Collaboration Meeting Mar. 2016
Surface c (5 GeV)
5 GeV >10 k >50 k W
Bas. High Emit
Opt 1 High Emit
Opt 2 High Emit <0.01
Bas. Red. Emit
Opt 1 Red. Emit
Opt 2 Red. Emit <0.01
JLEIC Collaboration Meeting Mar. 2016

24. JLEIC Collaboration Meeting Mar. 2016
Surface d (10 GeV)
10 GeV >10 k >50 k W
Bas. High Emit e e
Opt 1 High Emit e e
Opt 2 High Emit e e
Bas. Red. Emit e e
Opt 1 Red. Emit <0.01
Opt 2 Red. Emit e e
JLEIC Collaboration Meeting Mar. 2016

25. JLEIC Collaboration Meeting Mar. 2016
Surface d (5 GeV)
5 GeV >10 k >50 k W
Bas. High Emit <0.01
Opt 1 High Emit <0.01
Opt 2 High Emit e
Bas. Red. Emit <0.01
Opt 1 Red. Emit <0.01
Opt 2 Red. Emit e
JLEIC Collaboration Meeting Mar. 2016

26. JLEIC Collaboration Meeting Mar. 2016
Some results
Difficult to get an IR beam pipe much smaller than a 3cm radius.
Calculated the number of photons that penetrate the beam pipe
For a 1mm thick pipe of Be and 10 and 25 um of Au inner layer
Estimated incident angle of photons is 14 mrad
Then about 2% of the incident photons penetrate
Need to know how long the central pipe needs to be (assuming right now ±50 cm)
Shorter pipes are easier to shield
JLEIC Collaboration Meeting Mar. 2016

27. Photon Energy plot (10 GeV)
Surface d
10 um Au
3.16105
4.49103
JLEIC Collaboration Meeting Mar. 2016

28. Photon Energy plot (10 GeV)
Surface d
25 um Au
3.16105
2.74103
JLEIC Collaboration Meeting Mar. 2016

29. Photon Energy plot (5 GeV)
Surface d
10 um Au
1997
6.5
JLEIC Collaboration Meeting Mar. 2016

30. Total SR power and photons from upstream FF quads (10 GeV)
Photons Power(W)
Baseline High Emit 
Option 1 High Emit 
Option 2 High Emit 
Baseline Red. Emit 
Option 1 Red. Emit 
Option 2 Red. Emit 
JLEIC Collaboration Meeting Mar. 2016

31. Total SR power and photons from upstream FF quads (5 GeV)
Photons Power(W)
Baseline High Emit 
Option 1 High Emit 
Option 2 High Emit 
Baseline Red. Emit 
Option 1 Red. Emit 
Option 2 Red. Emit 
JLEIC Collaboration Meeting Mar. 2016

32. Surface d Option 1 (10 GeV) Smaller IP beam pipe
10 GeV >10 k >50 k W
Opt 1 HE 3 cm e e
Opt 1 HE 2.5 cm e e
Opt 1 HE 2 cm e e
Photon rates go up almost x10 for each 5mm decrease in radius
JLEIC Collaboration Meeting Mar. 2016

33. Where does it come from? For surface d
JLEIC Collaboration Meeting Mar. 2016

34. JLEIC Collaboration Meeting Mar. 2016
Summary
Based on this initial study of SR backgrounds
Option 1 looks to be the most promising
Reduced beam emittance is a big winner
Masking can probably be further optimized
5 GeV beam is much easier
Emittances are smaller
Photon critical energies are lower
JLEIC Collaboration Meeting Mar. 2016

35. JLEIC Collaboration Meeting Mar. 2016
Conclusions
SR for the JLEIC IR looks controllable but needs further study
Especially more information from the detector group about what they need at very low angles
Also need feedback from detector people as to what are acceptable background rates for the inner trackers
How many photons/collision going into the inner detectors are OK before occupancy or radiation damage occurs
There is always more to do…
JLEIC Collaboration Meeting Mar. 2016