1. 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

2. 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

3. 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

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

5. 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

6. 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

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

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

9. 11/24/2018
Giancarlo Piredda

10. 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

11. 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

12. Shielding Wall
11/24/2018
Giancarlo Piredda

13. 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

14. 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

15. 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

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

17. 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

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

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

20. 11/24/2018
Giancarlo Piredda

21. 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