1. Cold versus Warm, parameters impacting LC reliability and efficiency contribution 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. TESLAJLC (C)JLC/NLCCLIC RF Frequency in Main Linac (GHz)1.35.711.430 Loaded Gradient (MV/m)23.831.550150 Q Unloaded10 9772~9024~3625 Shunt Impedance (M  /m) 10 7 54.181.2~23.5 Klystron Peak Power (MW)9.7507550 RF Pulse – before/after compr. (  s) 1370/13702.8/0.551.6/0.416.7/0.13 Filling Time (  s) 4200.2850.1200.03 Total No. of Modulators5724276508448 Total No. of Klystrons57242764064448 Cavity/Structure Length (m)1.041.80.90.5 Total No. of Structures/Cavities205928552121927272 Plug to Beam Efficiency (%)23.36.28.89.3 Parameter table

8. TESLAJLC (C)JLC/NLCCLIC RF Frequency in Main Linac (GHz)1.35.711.430 Design Luminosity (·10 34 cm -2 sec -1 )3.41.42.5/22.1 Linac Repetition Rate (Hz)5100150/120200 No. of Particles per Bunch (·10 10 )20.75 0.4 No. of Bunches per Pulse2820192 154 Bunch Separation (nsec)3371.4 0.67 Bunch Train Length (  sec) 9500.267 0.102 Beam Power per Beam (MW)11.35.88.7/6.94.9 Unloaded Gradient (MV/m)23.841.865172 Loaded Gradient (MV/m)23.831.550150 Norm Emitt,   x,   y, after DR (10 -6 m-rad) 8/0.023/0.02 1.8/0.0 05 Two-Linac-Length (km)3017.113.85 Total Site AC Power (MW)140233243/195175 Parameter table

9. Wall Loss Factor at 500 GeV cm TESLANLCCLIC Loaded, Average Gradient (MV/m) 23.850150 Average Bunch Train Current (mA) 9.5868972 Peak RF Power/m at Beam (kW/m) 22642900145757 Peak RF Power Loss in Wall (kW/m) ** 0.1130790270000 Wall Power Loss Factor  wall 0.80*0.580.35 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,  wall, 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. Efficiency of structures and cavities

10. Total Linac Efficiency Total Efficiency at 500 GeV cm TESLANLCCLIC RF Pulse (total/total-filling) (  s) 1370/9500.4/0.280.13/0.1 Structure Efficiency (wout wall-loss&load) (%) 707077 Struct.Eff. (incl. wall-loss and 8% load)  struct (%) 57*38~25 Modulator Efficiency (%) 858085 Klystron Efficiency (%) 655565 Pulse-Transmission / Compression Eff. (%) 987572 RF System Efficiency  RF (%) 543340 Auxiliary Average Static Plug Power (kW/m) 0.30.58~0.4 Beam Duty Factor (f rep  flat ), (%) 0.480.00340.002 Auxiliary System Efficiency  aux (%) 7872~90 Total Efficiency  tot (%) 24910 *Includes 332 W/m at the plug of dynamic RF loss in couplers and HOM absorbers. Total linac efficiency

11. Plug to power efficiency of cold and warm WARM, ILC-TRC second Report, page 79 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% note LC RF = 167 MW in resp. to questions, plug-to-beam eff ~ 8%