1. The 2008 SPS electron cloud transmission experiment: first results F. Caspers, E. Mahner, T.Kroyer Acknowledgements to B. Henrist, J.M. Jimenez, J.M. Laurent, TS/MME workshop & cleaning teams, VAC colleagues Outline  Layout  Basics and history  First results during scrubbing run  Conclusion and outlook Tuesday 01 st of July 2008, SPSU, CERN

2. 2F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Basic layout for microwave transmission setup (SPS 2008) Principle idea: “When electromagnetic waves are transmitted through a not too dense plasma, they experience a phase shift and possibly a small attenuation” 14.4 m 33.1 m Antenna1 Antenna2 (excitation)Antenna3 dipole quad F. Caspers, T. Kroyer 2008 is similar to the 2004 setup

3. 3F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Some basics and history (1)

4. 4F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Some basics and history (2)

5. 5F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Some basics and history (3)

6. 6F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Some basics and history (4)

7. 7F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Some basics and history (5)

8. 8F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Some basics and history (6) The presently used setup in BA5 is rather similar, except that we have dedicated button like PU‘s and kickers with a circulator after the hybrid and rather narrow-band filters (40 MHz) with steep slopes. The filters are centered at 2.5 GHz. We used this time as receiver a conventional spectrum analyzer and a vector spectrum analyzer.

9. 9F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (2) SPS super-cycle 17656 Display from a conventional spectrum analzyer. The phase modulation is in the small peaks, which +/- 44 kHz away from the center. The beam induced signal are the two bigger peaks next to the center line.

10. 10F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (1) Display from a conventional spectrum analzyer. The phase modulation is in the small peaks, which are +/- 44 kHz away from the center. The beam induced signal are the two bigger peaks next to the center line. In this display one can see the true width of the carrier, the modulation sideband and the beam signals. SPS super-cycle 17651

11. 11F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (3) SPS super-cycle 17568-69 CW signal on Time axis is from top to bottom, intensity is color coded.

12. 12F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (4) SPS super-cycle 17585-87 CW signal off-on-off-on

13. 13F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (5) Shift of CW frequency SPS super-cycle 17606-08

14. 14F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (6) SPS super-cycle 17601-03 Higher harmonics of the modulation sidebands since the modulation is rather rectangular than sinewave

15. 15F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (6) SPS super-cycle 17552 Expanded view of one modulation sideband vs time. Time axis is from top to bottom, intensity is color coded.

16. 16F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (7) SPS super-cycle 17641 Intensity of the modulation sideband vs time in logarithmic scale

17. 17F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Preliminary measurement results in 2008 - scrubbing run (7) SPS super-cycle 17650 Intensity of the modulation sideband vs time in linear scale

18. 18F. Caspers, E. Mahner, T. KroyerSPSU 2008-07-01 Conclusion and Outlook The intermodulation problem observed in 2003 (experiments in BA2) has been eliminated using a proper RF setup with highly selective filters at the frontend, both, for excitation and on the pickup side. First electron cloud transmission experiments performed during the 2008 SPS scrubbing run in June have shown very promising results in BA5. The presence of electron clouds was identified simultaneously with button pickups. Microwave transmission over a full LHC arc at cryogenic temperature has been already successfully demonstrated around 7 GHz. The technique discussed here can be directly applied for integral electron cloud diagnosticss over a full arc in the LHC. For this purpose the installed in situ reflectometer couplers at the end of each arc could be used. Many thanks to Christian Carli for lending us the real-time spectrum analyzer and contributing during data taking.