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Giorgio Bellettini, Seul ITRP meeting, August 11, 2004

Cold versus Warm, parameters impacting LC reliability and efficiency contribution to the discussion on risk factors. Giorgio Bellettini, Seul ITRP meeting, August 11, 2004. Klystrons in Cold and Warm ( s = 500 GeV). TESLA : 572 klystrons, peak power 10MW.

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Giorgio Bellettini, Seul ITRP meeting, August 11, 2004

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  1. Cold versus Warm, parameters impacting LC reliability and efficiencycontribution to the discussion on risk factors Giorgio Bellettini, Seul ITRP meeting, August 11, 2004

  2. Klystrons in Cold and Warm(s = 500 GeV) TESLA : 572 klystrons, peak power 10MW. Acceleration efficiency: 1 klystron feeds 36 cavities providing 850 MeV accelerating voltage to beam NLC : 4064 Klystrons, peak power 75MW. Acceleration efficiency: 8 klystrons feed 24 cavities providing 1000 MeV accelerating voltage to beam ~8 times more klystrons (modulators, SLEDs) in Warm. Power on beam : TESLA 226 KW/meter, NLC 42,900 KW/meter after bunch compression Power density on beam ~ 200 times larger in Warm The klystron string of the Warm might turn out not be reliable enough The power density of the Warm might turn out to fatigue the structures

  3. Power efficiency in Cold and Warm (*) (s = 500 GeV) • Total AC power for 2 linacs (cryo included) TESLA 95 MW, NLC 150 MW • Total plug to RF to linac beams efficiency: TESLA ~23%, NLC ~9% • Total lab AC power TESLA 140 MW, NLC 195 MW (**) • Total beam to site power efficiency TESLA ~16%, NLC ~7%. • The excess power of the Warm is an economical and a social risk. • (*)ILCTRC Second Report (2003), Chapter 2, tables 3.6 and 3.19 megatables • (**) Fermilab power ~ 55MW. Difference is ~FNAL.

  4. Delivering luminosity for physics The general risk factors in delivering useful luminosity for physics were discussed in the section on Energy and Luminosity. A particular attention should be given to energy scans since they would be essential to study the properties of new particles.

  5. Energy scanning with Cold and Warm(s = 500 GeV) NLC: Beam bypasses at 50 and 150 GeV in each Linac. In measurements at intermediate energies beams will have to travel along a varying number of off-cavities before getting to the closest bypass. Besides tuning of the external beam lines, re-tuning of the linac optics will be necessary each time since magnets will have gone through different cycles. TESLA: RF gradients and magnet fields will be reduced to reduce the energy. The same scaling law of the magnet fields will be valid at all energies. Taking data at many energies might turn out to be very laborious with Warm.

  6. Backup slides follow

  7. Parameter table

  8. Parameter table

  9. Efficiency of structures and cavities Efficiency and site power limitations are driving the beam power of the LC design. The main difference between the NC and SC designs lies in their plug-to-beam power efficiency. The difference in efficiency is related in part to the amount of losses in the wall. The wall loss can be calculated from the unloaded gradient and the shunt impedance. A wall loss factor, hwall, can be derived from the beam power (beam-current x accelerating voltage/m) and the wall loss. *The Carnot “penalty” factor of 500 for the 2K operation is included. ** Shunt Imp. def. for TESLA incl.2.

  10. Total linac efficiency Total Linac Efficiency *Includes 332 W/m at the plug of dynamic RF loss in couplers and HOM absorbers.

  11. Plug to power efficiency of cold and warm WARM, ILC-TRC second Report, page 79 note LC RF = 167 MW in resp. to questions, plug-to-beam eff ~ 8% COLD, ILC-TRC Second Report, pag. 36 LC (cryo+RF) = 98 MW in resp. to questions, eff ~23%. US study cryo+RF=110.4 MW, plug-to-beam eff ~ 20%

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