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. 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 enoughThe power density of the Warm might turn out to fatigue the structures

Power efficiency in Cold and Warm (*) (s = 500 GeV)

Total AC power for 2 linacs (cryo included) TESLA 95 MW, NLC 150 MWTotal 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.

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.

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.

Backup slides follow

TESLA JLC (C) JLC/NLC CLIC

RF Frequency in Main Linac (GHz) 1.3 5.7 11.4 30

Loaded Gradient (MV/m) 23.8 31.5 50 150

Q Unloaded 1010 9772 ~9024 ~3625

Shunt Impedance (M/m) 107 54.1 81.2 ~23.5

Klystron Peak Power (MW) 9.7 50 75 50

RF Pulse – before/after compr. (s) 1370/1370 2.8/0.55 1.6/0.4 16.7/0.13

Filling Time (s) 420 0.285 0.120 0.03

Total No. of Modulators 572 4276 508 448

Total No. of Klystrons 572 4276 4064 448

Cavity/Structure Length (m) 1.04 1.8 0.9 0.5

Total No. of Structures/Cavities 20592 8552 12192 7272

Plug to Beam Efficiency (%) 23.3 6.2 8.8 9.3

Parameter table

TESLA JLC (C) JLC/NLC CLIC

RF Frequency in Main Linac (GHz) 1.3 5.7 11.4 30

Design Luminosity (·1034cm-2sec-1) 3.4 1.4 2.5/2 2.1

Linac Repetition Rate (Hz) 5 100 150/120 200

No. of Particles per Bunch (·1010) 2 0.75 0.75 0.4

No. of Bunches per Pulse 2820 192 192 154

Bunch Separation (nsec) 337 1.4 1.4 0.67

Bunch Train Length (sec) 950 0.267 0.267 0.102

Beam Power per Beam (MW) 11.3 5.8 8.7/6.9 4.9

Unloaded Gradient (MV/m) 23.8 41.8 65 172

Loaded Gradient (MV/m) 23.8 31.5 50 150

Norm Emitt, x,y, after DR (10-6m-rad) 8/0.02 3/0.02 3/0.02 1.8/0.005

Two-Linac-Length (km) 30 17.1 13.8 5

Total Site AC Power (MW) 140 233 243/195 175

Parameter table

m

W

z

EP

S

accW

2

CWbeam

beamwall fPP

P

Wall Loss Factor at 500 GeV cmWall Loss Factor at 500 GeV cm TESLATESLA NLCNLC CLICCLIC

Loaded, Average Gradient (MV/m)Loaded, Average Gradient (MV/m) 23.823.8 5050 150150

Average Bunch Train Current (mA)Average Bunch Train Current (mA) 9.59.5 868868 972972

Peak RF Power/m at Beam (kW/m)Peak RF Power/m at Beam (kW/m) 226226 4290042900 145757145757

Peak RF Power Loss in Wall (kW/m)Peak RF Power Loss in Wall (kW/m)**** 0.110.11 3079030790 270000270000

Wall Power Loss Factor Wall Power Loss Factor wallwall 0.80*0.80* 0.580.58 0.350.35

Efficiency and site power limitations are driving the beam Efficiency and site power limitations are driving the beam power of the LC design. The main difference between the power of the LC design. The main difference between the NC and SC designs lies in their plug-to-beam power NC and SC designs lies in their plug-to-beam power efficiency. The difference in efficiency is related in part to efficiency. The difference in efficiency is related in part to the amount of losses in the wall. The wall loss can be the amount of losses in the wall. The wall loss can be calculated from the unloaded gradient and the shunt calculated from the unloaded gradient and the shunt impedance. A wall loss factor, impedance. A wall loss factor, wallwall, can be derived from the , can be derived from the

beam power (beam-current x accelerating voltage/m) and beam power (beam-current x accelerating voltage/m) and the wall loss.the wall loss.

**The Carnot “penalty” factor of 500 for the 2K operation is included. ** Shunt Imp. def. for TESLA incl.2.The Carnot “penalty” factor of 500 for the 2K operation is included. ** Shunt Imp. def. for TESLA incl.2.

Efficiency of structures and cavities

Total Linac EfficiencyTotal Linac Efficiency

auxRFstructtot

Total Efficiency at 500 GeV cmTotal Efficiency at 500 GeV cm TESLATESLA NLCNLC CLICCLIC

RF Pulse (total/total-filling) (RF Pulse (total/total-filling) (s)s) 1370/951370/9500

0.4/0.280.4/0.28 0.13/0.10.13/0.1

Structure Efficiency (wout wall-loss&load) (%)Structure Efficiency (wout wall-loss&load) (%) 7070 7070 7777

Struct.Eff. (incl. wall-loss and 8% load) Struct.Eff. (incl. wall-loss and 8% load) struct struct (%)(%) 57*57* 3838 ~25~25

Modulator Efficiency (%)Modulator Efficiency (%) 8585 8080 8585

Klystron Efficiency (%)Klystron Efficiency (%) 6565 5555 6565

Pulse-Transmission / Compression Eff. (%)Pulse-Transmission / Compression Eff. (%) 9898 7575 7272

RF System Efficiency RF System Efficiency RF RF (%)(%) 5454 3333 4040

Auxiliary Average Static Plug Power (kW/m)Auxiliary Average Static Plug Power (kW/m) 0.30.3 0.580.58 ~0.4~0.4

Beam Duty Factor (fBeam Duty Factor (freprepflatflat), (%)), (%) 0.480.48 0.00340.0034 0.0020.002

Auxiliary System Efficiency Auxiliary System Efficiency aux aux (%)(%) 7878 7272 ~90~90

Total Efficiency Total Efficiency tot tot (%)(%) 2424 99 1010**Includes 332 W/m at the plug of dynamic RF loss in couplers and HOM absorbers. Includes 332 W/m at the plug of dynamic RF loss in couplers and HOM absorbers.

Total linac efficiency

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%