Summary of MDI meeting, 2 -4 pm, 11 September, Cambridge (Draft)
(1) Magnet Coil Support
We can design the support with proper strength, i.e. earth quake proof of 0.15G and 0.3G in Europe and Japan, respectively, even coil-support for 2G can be designed. The Ti-alloy should be studied.
(2) Platform
The platform has been proposed for simple and robust solution of the push-pull operation as well as good isolation against earthquake and vibration by Alan. There will be about 10 times operations of push pull in a year. The detector system must be secure and stable in these operations.
ILD takes advantage of platform in order to design the detector.
Since the second detector must adopt the platform scheme, it is an issue to be discussed in the MDI/BDS contacts for IDAC.
(3) Wall between two detectors
If the both detectors are self-shielded. the wall should not be needed. We may need some kind of boundary.
In the IR interface document,
"The off-beamline detector is shifted in transverse direction to a garage position, located 15m from the IP. "
So, we can use the 15m transverse space from the detector center if it is self-shielded. The space would be 15 minus a width of wall for non self-shielded detector.
(4) Stray field
The 200 Gauss tolerance of ILD will be re-considered. In the present DESY design, there is a stray field of 550Gauss at R=7.4m . The CMS has 1,000 Gauss just outside of the detector.
An effect on the second detector should be taken into account.
(5) Square support tube
The square one has more rigid than the round one assuming that the size of square is the same as the diameter of round one with the same thickness, material. In this assumption, the square one has larger inner space for cables. Also, endcap calorimeters prefer the square shape in the engineering design.
Two supporting systems were proposed, i.e. both has a fixed point outside of detector with different second fixtures (1) on the iron-endcap with sliding rails or (2) several rods from the coil in front of the tube.
Matthieu prefers the second system for more independent scheme, i.e. decoupled the endcap opening.
At this Cambridge meeting, we will not chose the square or round tube.
Adrian pointed out in his presentation that tungsten tube was needed for neutron shield in the endcap calorimeters.
Tungsten mask can be put innermost part of the calorimeters.
(6) Next meeting
11am-1pm, 12 September
We will continue to discuss the MDI issues, e.g. the stray field, tail catcher for 6.7 absorption length of ECAL and HCAL with the coil+cryostat, CMS style assembly, background estimation in ILD ( pairs, synchrotron radiations, muons, beam gas and mini-jets ), 2 platforms each for 2 detectors, 8 v.s. 12 of iron barrel structure, ...