14/07/2008 Massimo Benettoni PMTs need replacement. SOB volume reduction is desirable. detectors: PMT Hamamatsu H8500 detectors resolution allows smaller SOB Non focusing option (lower cost / known option): SOB filled with "liquid" (high purity water...or...) PMTs outside the liquid volume of SOB, facing fused silica windows distance between PMTs and bar wedges: 0.8 m (vs 1.2 m of Babar SOB) Overall view angle unchanged: ° Ave. windows inclination: 26.3°wrt vertical plane, 63.7° wrt beam direction Dirc SOB Non focusing (backup) solution

14/07/2008 Massimo Benettoni Dirc SOB Possible Design items Partition of the SOB with septums, to avoid full emptying and refilling in case of maintenance: No partition: about 3.6 m 3 (50% of Babar) Partition: allows up to 12 sectors, 300 l each Quartz windows dimensions: could be as large as each door of the SOB could be limited by production capabilities and by quartz strength and deformation. Minimizing dead space: Large windows to minimize septums As thin as possible septums and flanges/frame best matching of windows dimensions wrt PMT granularity (52x52 mm 2 ). PMTs packing frame and support

14/07/2008 Massimo Benettoni Dirc SOB SOB partition: feasible? If septums are feasible and desireable, the SOB volume could be divided in 2.. to 12 sectors of same volume. Each window/sector could be open and closed independently. BUT: Barboxes clearance =15 mm, “wedges enclosure” gap = 2 mm. Septums surfaces should be reflective, precise, thin …. and PMTs are outside SOB volume. PROS: small volume to drain/refill, leaks easier/faster opening/closing CONS:redesign of barboxes add dead space between barboxes, new barboxes extraction tool, more dead space, tracks reconstr.

14/07/2008 Massimo Benettoni Dirc SOB SOB doors without partition one shared volume as Babar, 3.6 m 3 Possible more than 2 doors: PROS: lighter, less stiffness requirements CONS: more sealings, additional devices for open /close, more interface flanges thus dead space Two doors as Babar seem best solution should be feasible in one piece (outer diameter 3.6m) could be light (400 kg of s-steel frame, 200 kg of windows, 300 kg of PMts)

14/07/2008 Massimo Benettoni Dirc SOB Windows dimensions and PMTs layout Simplest baseline:12 quartz windows Best fitting with a trapezoidal PMTs packed array: 18 rows, from 8 to 16 PMTs each 216 PMTs per each of the 12 windows PMTs for the full SOB (Babar SOB:11800 PMTs). “Indented sides” trapezoid: h=52*18=936 mm, b=52*8=416 mm B=52*16=832 mm. Best fitting requires to increase windows inclination from 63.75° to 69°. PMTs area 58.4 dm2 (PMTs geom. efficiency 89%) trapezoid area inscribing the array = 63.3 dm2 PMTs area lost for flanges: at least/about dm2 Trapezoid area not active due granularity: dm2 A good solution could give = 57.2 dm2 active region out of 63.3 dm2 of surface Geometric acceptance: 57.2/63.3 = 90% (maximum)

14/07/2008 Massimo Benettoni (example of 12 trapezoidal windows) Min. thickness about 15 mm to stand: hydrostatic pressure up to 0.35 atm PMTs and quartz gravity. Other contributes (still neglected): Stress induced by sealing (local compression along borders) Seismic loads … Possible more stringent requirements on deformation/displacement Material specs? E.g.: E= 70Gpa, Strenght=50 Mpa (up to 100 Mpa) Poisson=0.17 Need contacts with producers (Zygo, Corning, QPC, Thermo Syndicate, Hereaus) Dirc SOB Windows dimensions vs strength