G. Finocchiaro – INFN LNF XI SuperB General Meeting DCH-I parallel session LNF, 1 December 2009

Things to Discuss in This Meeting Backgrounds (R. Cenci’s talk in DCH-II on Wed.) Mechanical design Cell and gas optimization DCH Geometry optimization – DCH length (M.Rama in DGWG-II on Wed. morning) Electronics: FEE & DAQ design (G. Felici, later in this session) Progress in Lab. work (this session, DCH-II tomorrow) White paper – sections, who writes what – costing update 12/1/09G. Finocchiaro2

The Big ? : Background in the DCH 12/1/09G. Finocchiaro3

The Big ? (cont.) 12/1/09G. Finocchiaro4

Varying the DCH design: stepped endplate I have implemented a possible stepped endplate (a.k.a. “wedding cake”) design in gdml Aside from stringing issues, one concern with this option is debris production from particles produces at the I.P. on localized material (the steps) Plan to study the effect of various bkg sources ASAP 12/1/09G. Finocchiaro5

6/10 Mechanical Quenching Prevent multiplication in selected regions along the sense wire “Straightforward” endplate design and construction (at least, much simpler than tapered endplates) Need to work out details of how to attach plastic tube to feed- though Principle proved on small prototype What else should we do do be convinced there’s no downside? – e.g. testing on a full-scale prototype 1 or 2 layers in the TRIUMF prototype? 17 June 2009 sense wire “good physics track” plastic collar ionization in very forward region

Drift cell optimization 1-liner drift cell design guidelines uniformity ⇑ material ⇓ - obviously, contradictory ;( (As well-known) B A B AR uses hex cells “symmetric” and with low F:S ratio (2:1) but… mandatory Super-Layer structure, with guard wires 7104 sense 20  m ∅, 704 clearing 120  m ∅, 6400 guard 80  m ∅, field 120  m ∅ Overall material budget relatively high 12/1/09G. Finocchiaro7

Drift cell and gas optimization First attempt at a specific square-cell layout 44 measuring layers AA UV UV UV UV A (11 SL with 4 layers each) h=12mm w=  ×6mm (in first 8 A layers w=  ×3mm) 7696 sense 20  m ∅, 1520 guard 80  m ∅, field 80  m ∅ Lighter gas mixtures: (as well known) BABAR used 80%He-20%iC 4 H 10 KLOE uses 90%He-10%iC 4 H 10 In (*) the use of 80%He-20%CH 4 in a large prototype chamber, obtaining 90  m spatial resolution, is reported 12/1/09G. Finocchiaro8 (*) NIMA436 (1999) 336

Drift cell-gas mixture comparison 12/1/09G. Finocchiaro9  (g/cm 3 ) X0(g/cm 2 )X0(m) 80%He-20%iC 4 H E %He-20%iC 4 H 10 -hex9.98E %He-20%iC 4 H 10 -sqr8.78E %He-10%iC 4 H E %He-10%iC 4 H 10 -hex7.67E %He-10%iC 4 H 10 -sqr6.46E %He-20%CH E %He-20%CH 4 -hex6.33E %He-20%CH 4 -sqr5.13E Potential for good reduction of pT measurement error, especially at low momentum Need for simulation work, operational experience (with low-CH 4 content mixture) and more detailed cell design PRELIMINARY

Sensitivity to machine background photons crucial for rate budget He and iC 4 H 10 have small photon absorption cross section in the 10keV region More on gas mixtures: Photon absorption 12/02/0910G. Finocchiaro [Data from

Photon absorption (cont.) 12/02/0911G. Finocchiaro CH 4 and DME also have small cross section CO 2 and CF 4 not as good – should be used only in very small amounts

White paper… 1 st order approximation: copy section titles from the BABAR TDR Update of cost estimates Define schedule, assign writing tasks 12/1/09G. Finocchiaro12

AOB? 12/1/09G. Finocchiaro13