Report from IRENG'07 workshop at SLAC —— Olivier Dadoun and Matthieu Joré (LAL)
ILC Interaction Region Engineering Design Workshop 07 was held on Sep17th to 21th at SLAC. The IRENG 07 goals are to prepare EDR in 2010; review and advance the subsystems in Interaction Region; define the detectors needs and review the push-pull solutions. In this meeting, some detectors, such as LDC, GLDc, SiD are discussed and also the end cap design; some issues for the forward region (final doublet QD0, vacuum, forward calorimetry); push-pull and IR-Hall design. Several interfaces have been defined, such as IR Hall design and Crane capacity (in cavern& on surface). Another part of the meeting was on backgrounds estimation. This is important to assess the global performances and can impact basic geometries. They were talks about the upstream and downstream sources of backgrounds and about masking schemes. Main upstream sources arise from synchrotron radiation from the beams and secondary particles from the beam-beam interaction stopped on apertures near the IP, nearby masks and magnets. Main downstream sources arise through backscattering from lost disrupted beam particles and beamsstralhung photons in the extraction channels and subsequent transport lines. Interaction with the residual gas does not seem problematic for a residual gas pressure of 10 nTorr. A collaborative plan was set up to pursue further background studies as comprehensively as possible, for the different detector concepts and extraction line designs.
Impact of non-linearity on vertical emittance in ATF shared extraction line magnets ---- Maria del Carmen Alabau (IFIC (Valencia) - LAL (Orsay))
Studying the effect of the non-linearities of the magnets shared with the DR on the vertical emittance is necessary in the ATF extraction line, including QM6X and QM7X quadrupoles and the BS1X, BS2X and BS3X septum magnets. Cross-checks of the multipolar field expansion obtained at SLAC for QM7X were performed by fitting the POISSON field map in one dimension, around the nominal horizontal offset and for different vertical offsets. Tracking studies including the resulting multipolar components are going on with different beam offsets to estimate the impact on the vertical emittance of the beam. The results show that effects are seen even without including higher order multipoles, due to the small sextupole components in some of the bends and resulting linear x-y coupling effects. With higher-order multipoles included, mm-level offsets are also seen to cause significant effects. This work is continuing.
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