RPC and LST at High Luminosity Review the Babar muon detector configuration after 2005 Extrapolations based on background studies Large uncertainties Possible future improvements Hawaii Super B Factory Workshop January 19-22, 2004 Giancarlo Piredda, INFN-Rome 11/24/2018 Giancarlo Piredda

Forward Endcap Upgrade 2002 Gap #19 (new) RPC belt 5x2.54cm brass plates (Gaps 8,10,12,14,16) 10cm steel double gap RPC Easy access 11/24/2018 Giancarlo Piredda

RPC Upper Limits on the Hit Rate Set by electronics Strip signal held in FEC for 12.5 ms (deadtime) max rate 80 kHz/strip corresponding to about 30 Hz/cm2 Set by the streamer mechanism Depending from the local RPC material and operating point believed to be somewhat lower but not much different than the electronics limit RPC damage Degradation is also likely to start at similar values 11/24/2018 Giancarlo Piredda

Aging – Graphite Layer Above 0.6 C/cm2 surface resistance rises rapidly 11/24/2018 Giancarlo Piredda

Aging – Bakelite Resistance J. Va’vra 4*10^11 Wcm Above 0.5 C/cm2 bakelite resistance starts increasing Could be alleviated by flowing humid gas 11/24/2018 Giancarlo Piredda

Counting rates in the forward endcaps Rate=A*I_HER+B*I_LER+C*LUMI R.Messner Outer Layer rates follow LER beam losses Inner Layer rates due to Luminosity and HER Special run Usually layer 15 is off 11/24/2018 Giancarlo Piredda

Background is not uniform in the cross-section Layer 11 Layer 1 Layer 15 Layer 14 11/24/2018 Giancarlo Piredda

R.Messner 1C/cm2 1 year Lumi 6 12 18 20 35 10**33 11/24/2018 Giancarlo Piredda

11/24/2018 Giancarlo Piredda

Relevant remarks With the present rates and the present set-up the outermost layers are not safe. Layer 14 rate is about 100 kHz/RPC which corresponds to 100 mA and to an integrated charge of 0.1 C/cm2 per year The bulk contribution comes from the LER Shielding is necessary to allow full exploitation of outermost layers Layer 1 (middle) rate is about 40 kHz/RPC , could reach dangerous doses near the beam line needs further investigation and possibly dedicated shielding 11/24/2018 Giancarlo Piredda

Shielding The LER beamline on the forward is almost unshielded Planning for 20 cm steel wall (engineering project ready and approved) Based on the effect of almost the same amount of steel in between layer 15 and 12, the background rate reduction is estimated to be a factor between 5 and 30 (say 20 in average) A test wall (16” by 32”) installed in Oct 2003 and proven to be effective Installation foreseen in Summer 2004 shut-down 11/24/2018 Giancarlo Piredda

Shielding Wall 11/24/2018 Giancarlo Piredda

Layer 15 projection with and without the shield wall Integrated Charge/cm**2 Linear Scale R.Messner Wall starts July 2004 11/24/2018 Giancarlo Piredda

The after 2005 muon detector Barrel equipped with LST Forward and (Backward) EndCap (and “Belts”) equipped with RPC Shielding wall will be there The annual charge will be of the order of .05 C/cm2 at 0.3*10^35 lumi in the worst case (layer 1 without additional shielding). In any case the two outermost layers could be easily replaced (with RPC or LST). 11/24/2018 Giancarlo Piredda

Conclusions Extrapolations made on Pep-II ‘adiabatic’ upgrade (up to 0.35*10^35cm^-2s^-1) Need full simulation for having more reliable predictions RPC forward endcap could stand high luminosity with appropriate shielding. Further improvement on the accumulated charge still possible (alternate gas mixture) 11/24/2018 Giancarlo Piredda

...and LST Dec 2002 - LST choice for IFR Barrel Nov 2003 - Module design finalized Jan 2004 - Production starts Aug 2004 - Installation of 2/6 sextants Aug 2005 - Installation of remaining 4 sextants Very Large Effort 11/24/2018 Giancarlo Piredda

LST Tube Design The tube design has evolved into: Single-layer with a large cell (15 x 17mm) 8 wires/tube, 2 wires ganged together Readout wires for “f” coordinate eliminate cathode strips for f readout ground plane with embedded signal transmission line fabricated at Slac Transverse (“z”) coordinate readout via cathode strips z-strips planes fabricated at SLAC Tubes dimensions: ~ 20 x 154 x 3580 mm Tubes are manufactured and assembled in Italy (PolHiTech) QA/QC and Module Assembly in Princeton and OSU DAQ electronics includes FIFO buffer allowing multiple hit in the 12 ms trigger latency. 11/24/2018 Giancarlo Piredda

LST rates Maximal rate 100 Hz/cm Extrapolation as follows - 30 Hz/cm at 2*10^35 cm^-2s^-1 (3% occupancy) - 150 Hz/cm @ 10^36 (30% ) - Not uniform in depth Aging souldn’t be a problem... 11/24/2018 Giancarlo Piredda

In the Barrel annual dose less than 10 mC/cm Well below the ‘dangerous’ 100 mC/cm border 11/24/2018 Giancarlo Piredda

11/24/2018 Giancarlo Piredda

Conclusion No problem expected for the Barrel LST at luminosity up to a few 10^35cm^-2s^-1. New detector supposed to have a long and safe life Plan to study avalanche mode for high rate (forward endcap) environment. 11/24/2018 Giancarlo Piredda