Cross-check of the DIMAD beam tracking calculations for
the 2mrad extraction line – Sophie Cavalier
Extraction in the 2mrad scheme is a difficult task : the disrupted beam has to pass through a quadrupoles and a sextupole off-axis and then through the pocket fields of another quadrupole and sextupole. After that, it is barely separated from the incoming beam and is transported through 2 quadrupoles and a bending magnet whose apertures must be large enough to accommodate also the beamstrahlung. In the latter 2 large aperture quads, the incoming beam goes through a hole in the iron where the field must be very small. It is expected that these magnets will be designed as so-called "Panofsky" quadrupoles. Some verification of the feasibility of this scheme have been made and tracking results obtained recently by R. Appleby with DIMAD were reproduced and checked.
FCAL sensor developments – Abdenour Lounis
The BeamCal sensor will be exposed to very high radiation levels. Parameters of some materials are studied like diamond or epitaxial silicon and effects of high radiation are presented. A test of irradiation of some of these materials was performed in Darmstadt and first result are presented too.
Some other considerations and issues for these detector schemes were also mentioned:
• Use thin detector to minimize the dose received by the sensor.
• Integrate electronics on detector to reduce noise.
• Use 3D detector.
Limitation to minimum IP spot size from the Oide effect – Marie Thorey
Synchrotron radiation emitted by the beam during the focusing in the quadrupoles of the final doublet disrupts the emittance of the beam due to overfocusing of the particles once they have lost the corresponding energy. This disruption implies that the beam size has a lower limit. The different steps of the derivation presented in the original publication by K. Oide were reviewed in this talk. Plots of the beam size at the IP as a function of the beta function were shown for a simplified line and for the ILC one, with and without the synchrotron radiation in the final doublet, and using both the theoretical formulae from Oide's paper and the tracking and simulation of synchrotron radiation available in MAD. A relatively good agreement was found between both, even though the final doublet parameters do not satisfy some of the approximations used in Oide's theoretical computation. The minimum spot size is found to be around 3 nm for the ILC parameters, independent of the beam energy. Both ATF2 and ILC vertical spot sizes are larger than this limit.
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