Longitudinal Emittance Measurement CERN Linac-2

1. Longitudinal Emittance Measurement CERN Linac-2 A talks based on archeological findings (Pierre Tetu) Uli Raich CERN AB - BI (Beam Instrumentation) Uli Raich Thanks to R. Scrivens CARE workshop on emittance measurements U. Raich CERN AB/BI

2. Measurement Lines Measurement line LTE/LTL Protons Alvarez Linac RFQ Lead Ions IH structure Measurement line LBE/LBS Proton Linac 200 MHz RF frequence 100 µs pulse length 150 mA current

3. Transverse emittance line Kicker Quadrupole Quadrupole Kicker SEMGrid X’ X’ X’ X’ X’ X X X X X at slit after 1. drift space after 1. quadrupole after 2. drift space after 2. quadrupole CARE workshop on emittance measurements U. Raich CERN AB/BI

4. Transformation in Phase Space Kicker Quadrupole Quadrupole Kicker SEMGrid X’ X’ X’ X’ X’ X X X X X at slit first drift space first quadrupole second drift space Second quadrupol CARE workshop on emittance measurements U. Raich CERN AB/BI

5. Transverse and longitudinal E E φ φ Transverse Phase Space Longitudinal Pase Space X’ X

6. Buncher RF Longitudinal Phase Space Transformation Kicker • Spectrometer produces image of slit on second slit • second slit selects energy slice • first kicker sweep phase space over all energies • buncher rotates energy slice in phase space • at second spectrometer the phase distribution is transformed into an energy distribution analyzed by the second spectrometer • second kicker corrects for first kick Transformer SEMGrid Buncher Kicker Spectrometer magnet E E E E φ φ φ φ at slit first drift space buncher second drift space CARE workshop on emittance measurements U. Raich CERN AB/BI

7. Transverse Emittance measurement Kicker Transformer SEMGrid Buncher Kicker Spectrometer magnet E E E E φ φ φ φ at slit first drift space buncher second drift space CARE workshop on emittance measurements U. Raich CERN AB/BI

8. Photos of the line Kicker SEMGrid Buncher Kicker Spectrometer magnet CARE workshop on emittance measurements U. Raich CERN AB/BI

9. U. Raich CAS Frascati 2008 Beam Diagnostics

10. Calibration • Measurement of transformer signal with kicker “on” compared to intensity distribution on transformer when moving the slit with kicker off • Knowledge of the spectrometer magnet is needed to calculate eV/wire • Adjustment of the buncher phase must be done in such a way that the mean position in φ does not change with buncher on or off • Move the buncher phase by ± 30º and observe the mean displacement, knowing the spectrometer CARE workshop on emittance measurements U. Raich CERN AB/BI

11. Original electronics 12 µs 2 MHz clock Signal from wire 24 bit shift register reference level 0000000111111111100000 CARE workshop on emittance measurements U. Raich CERN AB/BI

12. New(er) Electronics and Software Treatment • 8 channel flash ADCs 40 MHz, 2kByte memory/channel • Measure during 12 µs (480 profiles of all 24 wires) • Average over 5 profiles • The kicker timing allows us to place the measurement slice of 12 µs anywhere within the 100 us beam pulse • The emittance mountain is plotted in pseudo-colors showing the beam intensities • The emittance mountain is cut in 10% slices to determine the surface containing 67% of the beam (this level can be modified) • The phase space surface is calculated and the corresponding emittance value calculated. • All this is done in the front-end computer CARE workshop on emittance measurements U. Raich CERN AB/BI

13. Application Program CARE workshop on emittance measurements U. Raich CERN AB/BI

14. Analyzing Spectrometer + Kicker CARE workshop on emittance measurements U. Raich CERN AB/BI

15. Slit CARE workshop on emittance measurements U. Raich CERN AB/BI

16. Spectrometer CARE workshop on emittance measurements U. Raich CERN AB/BI

17. Transformer CARE workshop on emittance measurements U. Raich CERN AB/BI

18. SEMGrid CARE workshop on emittance measurements U. Raich CERN AB/BI