Engineering aspects of the Detector interface

1. Engineering aspects of the Detector interface Knut Skarpaas VIII

2. Detector interfaces • Collider hall • Final magnet supports • Assembly Sequence

3. Collider Hall Geometry • Detector Size • Currently modeling structure for small US design • Small detector has a strong following • Magnet support for last quads fairly rigid • Compact package reduces deflections • Detector group is further along on this design • We are in continuous contact with many of the detector working groups

4. Collider Hall /Detector Assembly Procedure • Assembly staged during beamline commissioning • Must shield detector assembly area from the beam • Movable barrier • Temporary support for beamline • Must act like detector • Final focus assembly dependent on magnet support method • Cantilever • Support tube • Access to Detector Sub-components • Vertex detector • Central tracker • Endcaps may be captive • Segment endcaps

5. Magnet support options • Design goals for various support options • Minimize deflections • Minimize unsupported span • Put support near critical deflection points • Put support near massive items • Current cantilever option has support near mask centroid • Maximize moment of inertia (minimize sag) • Tubular support advantageous • Will need access ports to work on / install magnets • Minimize mass supported by tube • Some mask forces may be transferred to the doors

6. Design goals for various support options cont. • Material requirements • Minimize radiation length of material near Interaction Point • Cantilever design has no material at IP • Radiation hard design • Adhesives / polymers may degrade • Interface with required detector components • Vertex detector in bore (if support tube) • If cantilever, support vertex detector from mask tips or from central tracker • Masks (held by cantilever or inside support tube) • Tungsten masks are massive • 2500 lb requires support for door opening • Central tracker hugs outer bore (or masks) • Pass through steel in door

7. Design goals for various support options cont. • Door opening to be minimized to reduce Br near quads • Clearances • Assembly clearances • Allow for gravitational deflections • Current cantilever deflects .16” with door open • Seismic clearance • Site specific • Services • Vertex cables in bore (if support tube) • Cooling for vertex detector • Vertex detector requires 170k nitrogen gas • Foam or vacuum insulated lines • Foam lines are large (2”) • Luminosity monitor cables / cooling • In bore for most options

8. Assembly sequence • Must be able to put detector together first time • Must be able to access various components for servicing • Minimize time to get to buried components • Vertex servicing • Central tracker servicing

9. Allow for magnet positioning • Coarse adjust • First time alignment • Remote alignment to remain within fine adjustment range • Magnet Coarse Adjustment options • Actuation • Screw • Ramp • Cam • Bellows or piston with liquid or gas • Piezo • Drive style • Motor (stepper or servo) • Can not be used in high magnetic field • Drive shafts can transmit torque into bore • Wind up problems can be eliminated with proper gear boxes • May contribute too much heat / vibration • Motor (hydraulic / pneumatic) (rotary or linear) • Seals may be a problem in high radiation areas • Gas may be too compressible • Hydraulic fluid may not be radiation hard • Vibration and heat can be low • Peizo • Stroke may not be sufficient for the coarse adjust

10. Fine adjust • Get to final magnet location • Active positioning • Needs to be radiation hard • Non-magnetic • Fine Adjustment Options • Due to the fast response, and non-magnetic properties of piezo electric actuators, this is our current choice

11. Interferometer compliant • Several configurations possible • Maximize stability / minimize detector penetrations • Holes / windows in support allow sight to magnets • Vacuum / gas transport lines • Vacuum requires a joint to the stabilized object • Transport lines can transmit vibration • If vacuum is used with windows, windows may shift beam • Gas is nice, but index of refraction changes with temperature • Heat from electronics may shift beam

12. Support tube: • Tube passes through detector • Support styles possible: • Simple – Simple • Deflection is maximum & stress is high in center • The center is a bad place for high stress since it has a smaller moment of inertia and requires minimal material • Fixed – Rolling • Deflection is smaller & stress is high on ends • Fixed-Intermediate Support- Intermediate Support-Rolling • Tricky stress allocation • Central tracker group does not like this option • They would like to put detectors near the inner masks

13. Cantilever: • Tube is installed from each tunnel • May be mounted to a pier extending into pit • While running, support is near mask CG • Simple – Simple • Deflection is maximum when door is open • Deflection good while running • Fixed – Simple • Deflection is smaller but stress is high on one end

14. Detector / final focus options: • Option 1 • SLD style detector • Pro: Quick access /easy detector shapes • Con: Large pit / unstable magnets • Option 2 • SLD like detector with reduced door opening • Concrete pillar under magnets (except last 2) • Last 2 magnets on short cantilever or held by door • Door supports trimmed on outside (doors may need counter weight) • Pro: Quick access /easy detector shapes • All but last two magnets are on “bedrock” • Con: Last magnets rely on detector for stability (but could be actively isolated)

15. Detector / final focus options cont.: • Option 3 • BaBar like detector split door • Concrete pillar under magnets (except last 1) • Cantilever last magnet and mask • Door supports trimmed on outside (doors may need counter weight toward IP) • Pro: Quick access • Con: ECAL and HCAL must be split to remove (may require difficult rigging) • Option 4 • SLD like detector (cut off outer feet) • Key shaped pit • Roll detector to open • Fixture to open (to hold cantilever) • Pro: Stable / all but last magnet on bedrock • Con: Complicated pit / many cables to deal with / vac. dis-connect • Long down time to get to vertex detector

16. Detector / final focus options cont.: • Option 5 • Central detector spool package with Small detector layout • Top splits in middle (iron and HCAL move to sides) • Spool cranes out • Shake spool • Pro: Stable • Con: Complicated pit / hard to get inside spool / vac. dis-connect / tricky wiring

17. Assembly Procedures(Small detector / cantileveredsupports) • Assemble detector on shielded side of pit • Beam line commissioning happens using the real doublets on the other side of the pit with a temporary support • Remove EM magnets on pier and pull doublet back into tunnel • Rotate the detector to become parallel to the beam line • Roll the detector into place (including doors) • Slide cantilevered support tubes through doors • Make up vacuum and transfer load of masks from detector to the support tube

18. Vibration Issues • Since the extent of vibration amplification varies widely with various geometries, emphasis until this point has been put on solidifying the detector geometry • Detector revisions occur biannually • As detector shapes and magnet styles become more stable, vibration isolation methods will be explored further • Several possible vibration isolation scenarios are being considered • Under all conditions, local noise must be isolated from the detector • Local traffic minimized • Pumps on isolators on separate slabs • Well thought out plumbing and other services

19. Vibration Issues Continued • Find a stable site and make all components rigid • Many problems could arise if we do not have a “Plan B” (and the site becomes noisy) • Have a rigid detector and a floating (active / passive / both) magnet support • A permutation of this option may be the most practical for a large detector • Float the entire detector (or a large portion of it) on a gas suspension system • A possible air system has been considered which incorporates a variable natural frequency which allows adjustment for detector mass changes • Communication has begun with the LIGO group • Work is currently being done at LIGO to stabilize a several hundred kilogram mass to 1 nm • The LIGO system currently stabilizes a mass to a level several orders of magnitude better than NLC requirements. However, the system used is not currently practical for a physics detector. (Their frequency requirements are also different)

20. Thermal Issues • A high degree of positional stability requires a thermally stable environment • Detector will most likely be under a thick (~6’ thick) concrete lid for radiation protection reasons • Large thermal masses should aid thermal stability • Thermal excursions happen slowly and require a coarse adjustment range for the movers • Tunnels which connect to pit are fairly cool at this point • Should not be a large heat source (and may be sealed from pit) • Tunnel temperature is set by local cooling tower capacities • Have looked at wet bulb maximums at several sites

21. Conclusions • Detector design is still undergoing changes • We are in contact with key people in many detector working groups • One of the more popular detector choices is being structurally modeled currently • Several issues will be studied and prototyped in the near future • Vibration isolation options will be pursued