1. Final Focus optics for Possible New B-Line
A. Seryi, P. Emma, R. Erickson, T. Fieguth, M. Hogan, et al.
4 October 2004
NLC BDS meeting

2. Sub-picosecond bunch compression
spps g
Final Focus
and
beam dump
FF IP

3. Shielding wall
Shielding wall

4. Notes on Possible New B-Line
sec-30
50-line
B-line
e-meas.
sext.
FF-system starts here B2 B1
Q30
Q31
MAD optics output plot
Slide from
Notes on Possible New B-Line
P. Emma, R. Erickson, T. Fieguth, M. Hogan, A. Seryi, et al. Sep. 29, 2004

5. energy centroid and spread meas.
3 wire-scanner
e-meas. section
energy centroid and spread meas. -I
Dyx,y = 120
Slide from
Notes on Possible New B-Line
P. Emma, R. Erickson, T. Fieguth, M. Hogan, A. Seryi, et al. Sep. 29, 2004

6. Notes on Possible New B-Line
Longitudinal tracking through B-line, but prior to FF-system (SPPS mode at 28.5 GeV)
R56 = -2.3 mm
T566 = -35 mm
Slide from
Notes on Possible New B-Line
P. Emma, R. Erickson, T. Fieguth, M. Hogan, A. Seryi, et al. Sep. 29, 2004

7. Possible New B-line Parameters (SPPS-B)
symbol
SPPS
LCLS
unit
Energy E0 30 14
GeV
Bunch charge Q
3.4 1 nC
Emittance
gex0 (gey)
50 (5)
1 (1) mm
Energy spread (rms)
sE/E0
1.5
<0.1 %
Bunch length (rms) sz
12-40 20
Peak current
Ipk
9-30 kA
ISR ex-growth
Dex/ex 12 2
CSR ex-growth
<10 6*
Chromatic e-growth
Dex/ex (Dey/ey)
40 (40)
0 (0)
Slide from
Notes on Possible New B-Line
P. Emma, R. Erickson, T. Fieguth, M. Hogan, A. Seryi, et al. Sep. 29, 2004

8. NLC Beam Delivery System
Betatron
Collimation
Energy
Final Focus
Final focus with local chromaticity correction

9. New B-Line Final Focus
Same design concept as NLC FF (also adopted for ILC FF)
Local chromaticity correction in FD
Shorter L*, to be compact, but same chromaticity as in ILC
B-Line FF: L*=1m, bY*=0.1mm
ILC FF: L*=4m, bY*=0.4mm
Additional constraints to be compatible with short bunch operation
Limit R56 and T566 terms
The tentative optics shown below is designed with these constraints
The optics is tentative (ver.10), and is being improved

10. New B-Line with sub picosecond bunch compression
New Final Focus

11. (same chromaticity as present ILC parameters)
New FF for B-Line, version SHRTFF10.mad
L*=1m, and IP bx=4mm, by=0.1mm
(same chromaticity as present ILC parameters)

12. Final Doublet of New FF for B-Line, with sextupoles for local chromaticity correction,
optics version SHRTFF10.mad

13. Survey of New B-Line with FF
Optics till FF is in blue, FF optics is in red
z=0 at the end of BLINE0

14. Survey of New B-Line with FF
FF shown in red, dashed line show straight line from FF entrance

15. Evolution of FF optics performance versus version number
with B-Line
Evolution of FF optics performance versus version number
Beam size shown is obtained with Turtle tracking
Versions 8,9,10 include New B-Line bunch compression system

16. Performance of B-Line+FF optics version 10
Beam size shown is obtained with Turtle tracking
Already rather good for LCLS beam,
can be further improved for SPPS beam

17. New B-Line + FF short bunch performance
Complete system (B-Line + FF ver.10):
R56= mm, T566= mm
For beamline up to beginning of FF:
R56= mm, T566= mm
=> FF does not change R56 but ~ doubles T566
=> With SPPS beam (sE~1.5%), bunch length at IP will be lengthened by about 17mm which is still smaller than the SPPS beam goal of sz= 50mm

18. New B-Line + FF tracking cross-checks and Synchrotron Radiation
Tracking of the full system (B-Line + FF ver.10) with Turtle and with Dimad agree to better than 5% in terms of the IP beam size
Effects of SR (tracking by Dimad) on IP size increase:
LCLS beam: Dsx~2.8% , Dsy~0.8%
SPPS beam: Dsx~6% , Dsy~14%
=> SR effects are reasonably small

19. B-line +FF Parameters and Performance
symbol
SPPS
LCLS
unit
Energy E0 30 14
GeV
Bunch charge Q
3.4 1 nC
Emittance
gex0 (gey)
50 (5)
1 (1) mm
Energy spread (rms)
sE/E0
1.5
<0.1 %
Initial rms bunch length
sz0 50 20
Expected FF performance achieved so far (tracking including SR effects):
IP beta function
bx* (by*)
4 (0.1)
IP beam size
sx* (sy*)
4.5 (0.16)
0.45 (0.070)

20. LCLS parameters: sx / y = 0.44 / 0.070 mm
Tracked beam at IP of FF for SPPS and LCLS beam parameters on the same scale
IP beam size of the tracked (SR included) beam in a complete B-Line +FF system :
LCLS parameters: sx / y = 0.44 / mm
SPPS parameters: sx / y = 4.5 / mm
Further optimization of FF optics may allow further reduction of the IP beam size in SPPS case
LCLS beam, zoom in

21. Changes needed in FF optics ver.10
Provide space (3m?) for undulators in the beginning of FF
will lead to some lengthening of the system
Take into account present shield wall
Will shift FF about 7m downstream, if the wall is kept
Can the shield wall be removed or relocated?
Lengthen Final Doublet quads QF1 and QD0 about twice (for 30 GeV beam)
will lead to minor lengthening of overall beamline
Determine length needed for beam dump, if there is space left, use it for FF or undulators
Continue optimization, possibly, further reduce aberrations for SPPS beam
Standardize magnets, possibly use existing
Adjust angles in B-Line to fit to tunnel optimally
Look for ways to reduce T566

22. Survey of New B-Line with FF z=0 at the end of BLINE0
If the shield wall remains, need to lengthen beginning of FF (will also help to create space for undulators)
Note that the top plot is versus z and bottom versus s which are 1-1.5m different => location correspondence is approximate

23. Summary
New B-Line with sub-picosecond bunch compressor and with compact final focus may have the following capabilities in terms of the IP beam size:
sx,y,z~ * 0.16 * 50 mm for 30 GeV SPPS beam
sx,y,z~ 0.45 * 0.07 * 20 mm for 14 GeV LCLS beam