RF technology workshop, Amsterdam, October 4

1

• All current activity revolves around 6 lines per
  port
• Initial 6-beamline option still had too high a
  heat load on front mirror
• Main design challenge is reduction of heat load
  through
• Wider waveguides ? Resulting beams lead to lower
  power density
• ? This will help all options since 6 lines per
  port leave more room for this
• Increasing Din ? Spot size increases which
  lowers power density
• ? Only possible in combination with measures to
  limit front mirror size
• Decreasing angle of incidence ? this decreases
  loss factor on mirror
• Only possible with higher launching position
  (not desirable)
• or second front mirror per line

Result 2 options
1 end mirror for 3 beam lines 2 x 3 on 1 option
2 end mirrors per beam line Dogleg option
2
2 x 3 on 1 option
3
2 x 3 on 1 option

• Pros
• Smaller end mirror surface when wider waveguides
  are used. This leads to a lower heat load on the
  end mirror.

• Cons
• Since each end mirror controls three beams,
  there is less freedom in aiming the beams slight
  variation in Alpha / Beta angle.
• Mirrors most likely grow larger in length than
  earlier options with 1 line per mirror.
• Hole in front shield needs to be higher then
  earlier 6-beamline option. However, it can be
  more narrow.
• Placing the components at rear end of the port
  plug will prove to be difficult.

4
Dogleg option
5
Dogleg option

• Pros
• Launching positions can be placed lower and
  closer to the front shield
• Dog leg drastically reduces neutron streaming
  towards rear end of the plug, since waveguides do
  not face the plasma
• Front shield penetration is much smaller
• Mirrors are a lot smaller and are therefore
  easier to handle
• Less problems with placing components in the
  launcher interspace in the rear.
• Cut in lower blanket module is not required
• First mirror after waveguide can be used for
  both upper and lower row
• More flexible design due to increased number of
  parameters
• Scanning range through waveguide can be lower
  (/- 10 deg) for at least three beamlines

• Cons
• 9 Mirrors are required in the front shield,
  which leads to a higher amount of total power
  that needs to be cooled away
• Scanning range measured in degrees is larger
  then with any other option this requires a
  higher degree of accuracy in the steering
  mechanism and mirror surfaces.
• Less shielding can be realised for area above
  the port plug, as compared to previous options.
• ? There is still some room for further
  optimisation

6
Qualitative comparison
Blue 6 beamline option Purple 2 x 3 on 1
option Green Dogleg option
Conclusion When comparing nominal spot sizes on
the absorption plane, it appears that the dogleg
option outperforms all recent launcher options! ?
More time is needed to do exact calculations to
determine the overall performance