RF measurements during long MD in Week 27 Monday 4/7/2011

1. RF measurements during long MD in Week 27Monday 4/7/2011 Faraday Cage: T. Argyropoulos, T. Bohl, A. Burov, H. Damerau, J. E. Muller, E. Shaposhnikova, J. Tuckmantel CCC: H. Bartosik, W. Hofle, Y. Papaphilippou, G. Rumolo, B. Salvant, D. Valuch, SPS OP SPSU-BD 14/07/2011

2. General Purpose: Compare the longitudinal parameters of the nominal with the low γt cycle, using the 50 ns LHC beam (1-4 batches) • Voltage adjustments of the 200 MHz RF cavities in both cycles, to obtain similar conditions • Stabilize with double RF system (V800=V200/10 in both cycles) • Studies of PS  SPS transmission • Higher intensities (1.8e11 p/b injected) Super cycle with two nominal magnetic LHC cycles for nominal and low γt optics • Intensities at injection ~ 1.3e11 p/b • Transverse param.  CCC Measurment outline No controlled longitudinal emittance blow-up

3. RF Voltage set up – both cycles Q26: Bucket Area 0.65 eVs at ramp (from high intensity MDs) Q20: Bucket Area 0.6 eVs (sufficient) How to make them comparable? Q26 Q20 τinj~4 ns τinj~4 ns τFB~2.95 ns ε ~ 0.34eVs t ~ 13.9 s t ~ 15.3 s τFB~2.57 ns ε ~ 0.37eVs τFΤ~1.58 ns ε ~ 0.44eVs τFΤ~1.55 ns ε ~ 0.54eVs

4. RF Voltage set up – Q26 • be more close to Q20 • no changes at FB. Cycle is optimized. • keep V high at ramp because we need • it for emitt. blow -up Q26 – 0.65 eVs Q26 – 0.60 eVs τinj~4 ns τinj~4 ns t ~ 13.9 s t ~ 15.1 s τFB~2.57 ns ε ~ 0.37eVs τFB~2.55 ns ε ~ 0.36eVs τFΤ~1.45 ns ε ~ 0.47eVs τFΤ~1.55 ns ε ~ 0.54eVs Unstable later in the cycle because of larger filling factor

5. RF Voltage set up – Q20 • to have the same mismatch at injection • as for Q20 • slightly better for stability • still unstable  need 800 MHz τinj~3.9 ns τinj~4 ns τFB~2.9 ns ε ~ 0.33eVs τFB~2.95 ns ε ~ 0.34eVs t ~ 15.8 s t ~ 15.3 s τFΤ~1.58 ns ε ~ 0.44eVs τFΤ~1.58-1.61 ns ε ~ 0.45eVs

6. Double RF system (V800=V200/10) Q26 Q20 BSM Losses~2-6 % Stable BLM Losses~7-10 % Very unstable, more for Q26

7. PS  SPS transmission in Q26 • Studies of PS  SPS transmission in Q26 : • single batch • nominal Intensity (~1.3e11 p/b injected) • 3 different emittances (εnom < ε1< ε2 ) • 2 different bunch lengths • by changing the voltage in the 3 80 MHz RF cavities in PS (adjusting also the rotation time) • Preliminary results show: • higher ε  better stability •  more losses • higher τ  more losses • Analysis needs to be done.

8. Transmission/losses • SPS page 1 examples for: • Q26 - single batch – double RF – nominal εinj • Similar for Q20 Nominal intensity High intensity   ~1.63e11 p/b ~1.81e11 p/b ~1.26e11 p/b ~1.33e11 p/b ~1.6e11 p/b was achieved for 4-batches at FT • Further analysis needs to be done

9. Comparison Q26-Q20 (4 batches, 2 RFs) • Nominal Intensity (~1.3e11 p/b injected) • Higher Intensity (~1.8e11 p/b injected)

10. Comparison Q26-Q20 (4 batches, 2 RFs) Unstable bunches at the end of the 1st batch at Flat Top

11. Conclusions • Nominal Intensities (~1.3e11 p/b at FT) - losses~2-6 %: • Higher Intensities (~1.6e11 p/b at FT) - Double RF - losses~10 %: • Q20 is stable • Q26 some bunches unstable at flat top • PS  SPS transmission: dependence in εL and τ. • Single RF: Q20 is more stable than Q26 (higher threshold/Energy in the cycle) • Both unstable at the end of the ramp. • Double RF (V800=V200/10 ): Q20 is stable • Q26 some bunches unstable at flat top Future plans • Analysis of the PSSPS transmission data • Changes in 200 MHz RF Voltages to have more similar conditions at ramp: • 1) Increase Q20 or/and 2) decrease Q26 • Emittance blow-up at Q26 to stabilize the beam. • Keep the voltage dips at injections (23 MV) for Q26 voltage program • in the cases of more than 1 batch injections.