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Some thoughts about QD0 in the tunnel Lau Gatignon

Some thoughts about QD0 in the tunnel Lau Gatignon. Not a complete list, just to trigger discussions. Why QD0 inside detector?. L* = 3.5 m gives potentially largest luminosity This is the most challenging in terms of QD0 strength, stabilization and integration difficulties

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Some thoughts about QD0 in the tunnel Lau Gatignon

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  1. Some thoughts about QD0 in the tunnelLau Gatignon Not a complete list, just to trigger discussions

  2. Why QD0 inside detector? • L* = 3.5 m gives potentially largest luminosity • This is the most challenging in terms of QD0 strength, stabilization and integration difficulties • If you can make this solution plausible, all other solutions should a fortiori be possible • L* = 8 m seemed to be ruled out because of unrealistic prealignment constraints (2 mm) • Therefore we concentrated on this solution for the Conceptual Design Report. • Note: 4 QD0 magnets are needed Some thoughts about QD0 in the tunnel

  3. Why QD0 in the tunnel? • The double QD0 support tube plus anti-solenoid eats up a significant part of the forward acceptance in the case of shorter L*. • The shorter L* is different for CLIC_SiDand CLIC_ILD, leading to severe complications for either MDI or BDS. • End-coils allow to shorten the detector length to 12 (= ± 6) m,therefore L* = 6 m can be considered instead of 8 m. • For L* = 6 m the pre-alignment tolerance becomes 8mm, (almost) ok.Also the radiation environment is easier for stabilisation and alignment • Stabilization becomes easier, as well as the anti-solenoidand many integration issues. (Therefore more realistic to reach Lnom?) • Only 2 QD0 magnets are needed (same L* by definition) Some thoughts about QD0 in the tunnel

  4. So the questions are • How much luminosity does one loose (on paper)? • How much acceptance can one gain (on paper)? • How serious is the luminosity loss with respect to the difficulties to keep it stable inside the detector environment, i.e. are thereeffective luminosity losses due to such issues for the short L* ? • What is the net balance between luminosity and acceptance in terms of the physics reach? These questions deserve proper answers ! Some thoughts about QD0 in the tunnel

  5. What are the steps • What is the potential gain in acceptance, i.e. which systems have to be maintained in the detector region and can they be moved • How much luminosity do we loose, what are the QD0 and QF1 parameters: gradient, length, aperture, co-habitation with spent beam • Once the new detector acceptance has been defined, the physics can decide what luminosity loss can be tolerated. MDI BDS LCD Some thoughts about QD0 in the tunnel

  6. More in practical terms for Step 1 (MDI) • How large must the anti-solenoid be, keeping in mind that it must cover the spent beam as well. Note that QD0 is no longer there to shield the main solenoid field in this region. • Must the IP feedback remain inside the detector, and if so, where? • Is there a better location for Beamcal and Lumical • The vacuum system is probably simplified, but do we need valves inside the detector volume and what is their position and size. Does the vacuum pressure requirement change with the longer lever arm? Some thoughts about QD0 in the tunnel

  7. More about step 1 • Do we still need a pre-isolator and, if so, should it be modified? • Are there impacts on the backgrounds, e.g. does the argument for a thick vacuum tube remain valid? • Are the arguments for radiation shielding still valid, do we still need PAC-rings? • How do we have to modify the integration studies for the pre-alignment? Some thoughts about QD0 in the tunnel

  8. Detector Detector Integration Lever arm Radiation Space Forces Some thoughts about QD0 in the tunnel

  9. A starting point (for discussion)? Some thoughts about QD0 in the tunnel

  10. Some thoughts about QD0 in the tunnel

  11. Final remarks • The LCD work depends on the conclusions for the acceptance in the L* = 6 m solution • The BDS work is significant amount of work, it is important and will take too long to have us waiting for this • On the other hand, in my view there is nothing that prevents us from starting the MDI bit! • Many of the ongoing studies remain useful for both the short and longer L* solutions. Some thoughts about QD0 in the tunnel

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