GLD experimental hall and detector assembly Y.Sugimoto KEK 27 Sep. 2006

Background Experimental hall, detector assembly procedure, and iron yoke design are being re- considered Motivations are; Conventional facility (CF) construction schedule shown in Vancouver Distance between beam line and a wall increased from 12m to 12.5m due to change of crossing angle (2mrad+20mrad  14mrad +14mrad) Information about “Air-pad”

CF schedule

Underground experimental hall gets ready for detector construction at t=t 0 +4y11m  It would be impossible to start experiment at t=t 0 +7y Surface assembly hall can be ready at t=t 0 +3y If detectors are assembled on surface, we could get ready for experiment earlier than underground assembly by 1.5y or more

Surface assembly options Pure CMS-like assembly Detector is segmented into several large pieces ( <2000 ton /segment) (5 barrel rings and 3x2 endcap disks in case of CMS) Detector assembly and test are done on surface, then disassembled again and lowered to the underground experimental hall by 2500 ton gantry crane The large segments are moved by “air-pads” underground (no large crane in the experimental hall) Modified CMS-like assembly Detector is segmented into few tens of medium size pieces (<300 ton/segment) – Barrel yoke will be segmented into 24 (12(  )x2(r)) pieces Detector segments are pre-assembled on surface and lowered to the u.g. exp. hall by 300 ton movable overhead crane Final assembly and checkout of the detector are done underground

Barrel : 5 rings Endcap : 3 disks x2 CMS

Air pads for CMS

Possible drawback of two options Pure CMS Solenoid is supported by the central barrel ring  Thicker cryostat wall  Larger detector size Gaps between rings  More leakage field Precision of rings ?  Uniformity of B-field ? More number of iron slabs and more muon detector modules  Schedule and cost Job duplication on surface and underground  Schedule and cost Larger access shaft (  ~20m)  Schedule and cost Modified CMS More jobs underground  Schedule? Final construction of iron return yoke Solenoid installation and test Muon detector installation 300 ton cranes both on surface and underground  Cost Assembly procedure of heavy (~300 ton) pieces ?

Impact on detector/hall design Less jobs in the experimental hall than totally underground assembly scheme  Smaller hall size For modified CMS-style assembly, less iron allows smaller crane Barrel of the DOD design; ~8300 ton  400 ton crane is necessary if divided into 24 (12(  )x2(r)) A new iron yoke design is made; ~6100 ton  300 ton crane is OK Larger leakage field of the new design is compensated by additional coils

New iron yoke design Barrel 4.5<R<7.2m, 8x25cm+1x30cm iron + 8x5cm gap |Z|<4.45m (35cm shorter than DOD design) Endcap 0.4<R<7.2m with pole tip of 0.4<R<2.5m 4.5<Z<7.5m with pole tip of 4.2<Z<4.5m 10x25cm + 1x30cm iron + 10x5cm gap 5cm gap between barrel and endcap Leakage field 70 G (44 G for DOD design) at Z=10m Compensation coils at Z=10m and 12.5m can make it 10m

New iron yoke design “Air-pad” developed for LHC experiments allows free movement of heavy detectors If the barrel part of GLD can move both in z-direction and x-direction, Experimental hall width can be smaller (32m  25m) Detector can be placed at the center of the hall (in z- direction) Because of smaller detector size and slightly larger distance between the beam line and a wall, endcaps can be open normally (not like a door), and consequently, endcap calorimeters can be supported by endcaps

New iron yoke design

New experimental hall design Assumptions: New GLD geometry (R=7.2m, Z=7.5m) Modified CMS-like assembly scenario Temporary floor of the beam line for the BDS pre- commissioning has a width of 3 m Width of concrete shield used for the pre-commissioning is 3 m Nothing should be placed at the bottom of the access shaft Five large segments (Barrel and 4 halves of endcap) should have >1.5 m clearance around them for crane and human access

Discussion on the hall size Hall width 25m width would be necessary { 7.5m (detector) + 2.5m (crane access for concrete shielding) + 2.5m ( 3 cable chains (two for endcap halves and one for barrel)) } x2 =25m Hall height Less than 35m could be possible, depending on the shape of the vaulted ceiling This will be studied by CF group of GDE (Concept groups will provide information on the height of crane hook and crane capacity)

Cable chains for CMS