Meeting on Debuncher Cavity 3. June 2010

present: A.K. Bhattacharyya, P. Baudrenghien, M. Vretenar, R. Wegner, C. Carli

ZTT optimisation of debuncher cavity

• RW showed that one can gain around 13% in shunt impedance when removing the water cooling channels (thinner walls between the cells) and optimising the shape of noses within the material limits. (slides in EDMS)
• The decision was taken that we keep the standard PIMS geometry, which considerably reduces the construction and design effort.

coupling factor (power coupler)

• RW said that it should be possible to adjust the power coupler for a coupling factor of 2, which would give a Q_loaded value of around 6000. Together with a 40 us period and 20 mA beam current the power consumption seems to come down to the n x 10 kW range (exact number still to be confirmed).

LLRF simulations

• (slides in EDMS)
• AKB showed that the energy ramping cavities be operated with 20 mA and a 20 us period, without driving a 1.3 MW klystron into saturation. However, there is little margin left for LLRF to operate in these conditions.
• The frequency detuning in the cavities is now taken into account but it does not change the overall behaviour.
• If necessary one can still reduce the linac energy to get a steeper rise time in the ramping cavities. For the moment, however, we assume that the average energy stays at 160 MeV. This means that the cavity design will be made for this assumption.

PSB simulations

• CC showed various methods to deal with longer injection periods (40 us instead of 20 us), e.g: injection only every 2nd turn, lower current (20 mA), or injecting over 40 us with falling or rising voltage instead of using 20 us "up" and 20 us "down" per ring. (slides in EDMS)
• It seems that all these methods are feasible and that the expected longitudinal filamentation of the last method quickly disappears (after a few 100 turns)

Actions:

• CC: verify behaviour of transverse phase space when using a 40 us "single sweep" injection into PSB rings.
• CC: verify number of foil hits and cross-check additional emittance growth via scattering.
• RW/AKB: consolidate cavity parameters.
• dont forget: to foresee a 50-70 kW circulator so that the solid state amplifier powering the debuncher does not get damaged.
• CC: long term: test different wave shapes for injection. Now we are assuming a triangular voltage rise/fall, but we should try to use the other extreme: sinusoidal.
• AKB/PB: consolidate simulations.

Next Meeting:

29. June, 9:00 in 354-1-001 -- FrankGerigk - 04-Jun-2010