Bird`s IP view of limits of conventional e{sup +}e{sup {minus}} linear collider technology Page: 4 of 13
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Table I.
Long Bunch Train Working Parameter List for a 250 and 500 GeV NLC
General Parameters
500 GeV 1 TeV
Parameter CM Energy CM Energy Comments
E 250 GeV 500 GeV Beam Energy
Lo 6 x 1033 1.2 x 1034 Luminosity
LH 9 x 1033 2.0 x 1034 w/Enhancement
2 Lia 15km 15km Total X-Band Linac Length
E 50 MV/m 100 MV/m Accelerating Gradient
frf 11.4 GHz 11.4 GHz rf Frequency
N 0.65 x 1010 1.3 x 1010 Particles/Bunch
nB 90 67 Number of Bunches
sB 1.4 ns 1.4 ns Bunch Spacing
f 180 Hz 120 Hz Bunch Trains/second
Pbem 4 MW 8 MW Average Beam Power at IP
P 90 MW 140 MW Modulator Wall-Plug Power for Both Linacs
a, 300 nm 425 nm Variable
ay 3 nm 2 nm &7 scaling
a, 100 100 s Bunch Length
S 2 x 10-3 2 x 10-3 Intra-bunch Energy Spread
2 x 10-3 2 x 10-3 Bunch-to-bunch Energy Centroid Deviationonly remaining free factor, , will be limited by stability considerations and normalized
emittance limits. If we require the luminosity to scale as the square of the energy and to equal
10 cm s then L must equalN
efficiency; (iii) ( ); and (iv) the inverse of the vertical spot size. For the NLC 1 TeV
<a,
3 18 34 -2 -l
parameter set for which Y = 10 and L = 1.7 x 10 cm sec , we have
5 N 16 1
P = 1.4 x 10, t, =0.12, = 3 x 10 , and =0.7 x 109.
<a, <->>Long Bunch Train
Table 2.
Working Parameter List for a 250 and 500 GeV NLC
IP Region500 GeV 1 TeV
Parameter CM Energy CM Energy Comments
a, 300 nm 425 rim variable -+ x%
ay 3nm 2nm , scaling
ex 10-11 1/2 x 10-11 'r,= 5 x 10-6 meter-rad
ey 10-3 1/2 x 1013 yEy= 5 x 10-8 meter-rad
p( 10mm 40mm Forax,2x Vj scaling
(3y 100 3 101
axiy 30,30 grad 15,20 srad IP Divergent Angle
a. 100 100 Bunch Length
Od 3 mrad 4.2 mrad Bunch Diagonal Angle
6- 2 x 10-3 2 x 10-3 Energy Spread
Dx .08, 8.3 .04, 8.8 Disruption Parameter
Op .25 mrad .17 mrad Maximum Disruption Angle at Beam Energy
Y (upsilon) 0.1 0.28 Beamstrahlung Parameter
SB .03 .077 Mean Energy Loss to Beamstrahlung 'ys
0.9 1.1 Number of Photons per Electron
Nhad .04 .34 Number of Hadronic Events per Bunch Crossingt
Nts .001 .03 Number of Mini-jet Events per Bunch Crossingt
tCalculated following arguments of Chen, Barklow, and Peskin.
IP Re7ion26 2 -2 -i
L =10 y m s 5Putting this together with the luminosity formula [Eq. (2)] one arrives at
N 1
y3 = 0.5 x 10~14p1_,>( )( )(3)
Limits on Luminosity Factors
The P 11 (= 2P.) Limit
(4)
The product of four factors must increase with the cube of the energy to achieve an acceptable
design for a higher-energy machine. These factors are: (i) the wall-plug power; (ii) theThe wall-plug-to-beam efficiency achievable with present conventional rf technology is about
6%. The 1-TeV technology efficiency is projected to be 12%. This gain is achieved by going to
a gridded klystron, or improving modulator efficiency. We take as a "foreseeable" technology
an efficiency of 19% which would be achieved by eliminating the SLED pulse compression6
ss5A19
11-94
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Irwin, J. Bird`s IP view of limits of conventional e{sup +}e{sup {minus}} linear collider technology, article, November 1, 1994; Menlo Park, California. (https://digital.library.unt.edu/ark:/67531/metadc669976/m1/4/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.