1. Emittance Growth in the SPPS Chicane P. Emma, P. Krejcik, C. O’Connell, M. Woodley; SLAC, H. Schlarb, F. Stulle; DESY

2. 14-meter chicane compressor in linac at 1/3-point (9 GeV) Damping Ring (   30  m) 1.1 mm  z  50  m  z  12  m  z  6 mm SLAC Linac 1 GeV 30 GeV 30 GeV FFTBRTL Short Bunch Generation in the SLAC Linac 30 kA 80 fsec FWHM see H. Schlarb talk on Friday

3. Chicane Parameters 14.3 m

5. Last Y-chamber was copper coated to limit resistive-wake. Small ‘tweaker’ quads included to control residual x-dispersion.

6. CSR simulations with 1D model (good agreement with 3D-model studied by F. Stulle) fwhm/2.35  35  m 9 kA

7. CSR simulations (1D) ~10% ~20% ISR = incoherent synch. rad.

8.  1 (deg) Chicane energy constant to <5 MeV rms Wakefield energy-loss scans to confirm bunch length…

9. Bunch length confirmed with strong wakefield -induced energy loss of 1870-m of SLAC linac:  z  50  m.

10. 62  m rms bunch length Bunch length is also measured with transverse deflecting rf :  z  50 to 70  m  y 2 (arb) rf phase (deg) 28 GeV 50  m

11. Dispersion is first measured by energy variations correlated with BPM readings

12. Four wire-scanners within 60 m of end of chicane — used to measure x - emittance.  x = 5 m Emittance measured with precision of 2-4%, over <1 hour.

13. Finally, residual x -dispersion (and its angle) is precision minimized using ‘tweaker’ quads in the chicane.

14.  x through chicane effects emittance growth… → was matched and verified:  x (m) xxxx xxxx Matched: Matched:47.2-2.031.000 Measured: Measured: 50.6  1.7 -2.17  0.08 1.002  0.003

15. All 4 individual beam sizes with asymmetric-gaussian fits wire-3 wire-1wire-2wire-4 chicane-OFFchicane-ONchicane-OFFchicane-ON wire-1 wire-2 wire-4wire-3  x = 263  m  x = 335  m  x = 80  m  x = 90  m  x = 113  m  x = 142  m  x = 205  m  x = 245  m

16. Chicane ON Chicane OFF  x = 27.6  0.6  m  x = 34.2  0.7  m

17. Emittance: Chicane ON and OFF Bend-plane emittance data is consistent with calculations and sets upper limit on CSR effect

18. Attempt to measure emittance vs. pre-chicane rf phase (chicane ON & OFF) minimum bunch length here at  1 =  19.5°, but initial emittance not constant with  1 chicane ON chicane ON chicane OFF chicane OFF chicane ON chicane ON chicane OFF chicane OFF

19.  Difficult to vary rf phase and also keep initial emittance constant  have no clear emittance vs. phase scans  Bunch length not measured simultaneously with emittance  up to ~1 hour delay (frequently much less)  Many emittance measurements made in various conditions  no large un-explained growth seen across chicane  Vertical emittance typically not measured for this experiment due to time constraint in optimizing initial y-emittance  Data is consistent with CSR and ISR effects, but no direct radiation measurements were made Final Comments