Brett Parker: Gamma-gamma option IR design
- Brett presented two options for gamma-gamma IR with 3.8m L* and with
field outside of QD0 compensated by two different methods.
- In the first method, the tapered magnet
surrounds the +-10mrad gamma-gamma opening cone.
Geometry and the remaining uncompensated fringe field is shown in the file
The extracted beam coming close to QD0 would see 2400 Gauss field, and the
beam on extracted axis would see less than 300 Gauss. This solution is
tight, but may work with 20mrad crossing angle (a common cryostat would need
to be used), while 25mrad would allow further reduction of the field seen by
the extracted beam. The corresponding excel file
allows one to play with the compensating field.
- In the second method, a compensating
anti-quadrupole is placed on top of QD0. While reduction of the QD0 gradient
is only 1.5%, the external field is compensated to the level of 300 Gauss
for the particles coming near the edge of QD0, thus about ten times better
the previous case. However, due to additional layers, the QD0 is now larger,
so this method would require 25mrad. The
corresponding excel file allows one to play with the compensating field.
Andrei Seryi: Optimization of IR for g-g using DID
- Andrei presented a method to use DID to optimize trajectories of the
outgoing converted beam for g-g case. The field and beam excursion in
the region from IP to the extracted line beginning (3.5m from IP) can be
reduced by a factor of four or better. The IP angle for the incoming
beam increases 1.7 times, and SR beam size growth increase as well, but
this still seem to be tolerable.
- Further studies: need to make post IP tracking of the converted
beam, determine power deposition on IR elements and detector background,
and optimize IR geometry using these three methods.
Andrei Seryi: Crab cavity effects on the Y beam size
- Andrei has shown that crab cavity kick, which creates horizontal
orbit deviation through the FD sextupoles, causes distortion of the
vertical beam size. While this effect is still small for ILC parameters,
the margin is only about a factor of four.