1. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping 1  Recall descoping scenarios for 235 and 200 MChF:  Tiziano: https://indico.cern.ch/event/399337/session/0/contribution/0/material/slides/2.pdf https://indico.cern.ch/event/399337/session/0/contribution/0/material/slides/2.pdf  CSC does not replace CFEBs by DCFEBs in ME3/1 and ME4/1  Expected to save 2.5 MChF  Allowed because L1A rate limited to 300 kHz, luminosity <5E34  Previously shown curves show data loss is “acceptable” (<1%)  In this presentation:  A more detailed look shows additional data losses, less savings, and more risk than previously documented  Also, comments on the CSC degradation scenario to be used for simulation studies of descoping

2. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  Based on limited analog storage in SCA chips of CFEBs (96 cells at 50 ns)  In ME3/1 and ME4/1, expect ~6% if L1A is 700 kHz and L=7.5E34, but <1% data loss under descoped conditions 300 kHz and L=5E34 2 SCAs 8 Cap Delay Cap Storage (Poisson) Cap Digization (Queue) Beam Crossing preLCT L1A·LCT 0.46  sec2.74  sec 26  sec Transfer to DMB Complete Caps can be used for storage when all others in use For HL-LHC this is the main capacitor usage Simple Model CFEB Capacitor Storage ME4/1: 7.5E34 & 750 kHz ME4/1: 5E34 & 300 kHz

3. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  Data from CFEBs in to DMB can exceed the capacity of the 1 Gbps optical link from DMBs to the DAQ system  This results in the system going out of sync and CSC needing to request re-sync from cDAQ. The rate grows with luminosity: 3 ~2 kHz resyncs !  Therefore DMBs and DDUs need replacement for ME3/1 and ME4/1 regardless  The 2.5 MChF descoping savings comes from naively taking ~2/3 of the expected total cost for 3 stations  Careful costing shows that in fact only 1.6 MChF is saved by descoping CFEB electronics of ME3/1 and ME4/1 but replacing DMB and DDU

4. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  Not (yet) reflected in the data loss curves: 1. 8  13 (14) TeV muon stub occupancy factor 2. Engineering safety factor (especially the large luminosity extrapolation) 3. Effect of new beam pipe and IR layout for LS3 4

5. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  CFEB stub occupancy - how to scale?  As n CH in Min Bias? (below) – small effect  As charged particles > P T ? (Data for 3, 9 GeV thresholds at right) – larger effect  We must try to measure it in CFEBs at B=3.8T before end of July 5 CMS-QCD-10-008_Figure_007-a.png CMS-FSQ-12-026_Figure_007.png

6. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  Especially the large extrapolation in luminosity required… safety factor of 50% does not seem excessive 6 5E341E34

7. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  New beam pipe  Replace stainless by Aluminum 2219 to reduce radioactivity activation  Will rates in CSC chambers go up or down?  Would like to have “before” and “after” cross-sections of Point 5 region to gain some intuition…  Perhaps BRIL can tell us about the differences in charged and neutral particle fluences in CSC system before end of July?? 7 Phase 2 TP Figs. 11.9, 11.11

8. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  Overall: if the product of these three rate factors is >1.5, the situation for CFEBs at 5E34 will be similar to what the data loss plots show for L>7.5E34  Data losses will again be large (>6%) and rapidly climbing 8

9. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  The data loss curves are steep functions of luminosity, and as mentioned, subject to some uncertainty in rate  Motivation for the CFEB replacement depends mainly on better quantifying those data loss factors, not the simulation studies  There are other potential sources of CSC inefficiency that can be considered in sim studies to help motivating additional forward stations (GE2/1, RE3/1, RE4/1):  Aging of the electronics (15% loss in ME1/1 during Run 1)  Aging of the chambers (they will vary in their radiation tolerance) – note the recent scare about 4% gain loss in some ME1/1 during 2012 running that could have been aging, but was then traced to HV drift  Choose to take 15% loss of chambers, for all chamber types 9

10. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping 1. If it was MUCH larger, we would have to fix it 2. Normal electronics degradation in Run 1 was 1%/year. Can be fixed at long shutdowns, but maybe no access in LS3 (thus about 7% by middle of Run 4). The back half of chambers are pretty inaccessible even with access. 3. Electronics is getting older. One example: outer chambers will still have the problematic LV connectors that caused most of the 15% of non-working ME1/1 in Run 1 4. Radiation-induced aging will affect inner chambers more, but is due to electrochemical processes that will not be uniform due to chamber construction variation 10

11. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  The CSC data loss plot shown in the TP was insufficient  Did not include the limitations of the 1 Gbps optical fibers from DMB to DDU  We can include the plot of resync rate in the Scoping Document to explain that DMBs and DDUs need to be replaced for all three stations ME2/1 ME3/1 and ME4/1  The CSC descoping savings are overestimated, it is 1.6 MChF, not 2.5 MChF  More careful costing (0.4 M difference), plus needed replacement of DMB and DDU (0.5 M difference)  We have a couple of action items for July:  Measure the increase in CSC rates at 13 TeV and 3.8T  Understand qualitatively the change in CSC rates due the new beam pipe, IR layout of new TAS and quads on rates 11

12. GMM, 05-Jul-2015 Jay Hauser Another look at CSC ME3/1, ME4/1 descoping  Data loss plots – Stan Durkin & Ben Bylsma  Detailed costing – Darien Wood  TC review of MEx/1 electronics replacement (28-May- 2015) https://indico.cern.ch/event/394374/https://indico.cern.ch/event/394374/  Phase 2 Technical Proposal  http://cms.cern.ch/iCMS/analysisadmin/cadilines?line=TDR-15-002 http://cms.cern.ch/iCMS/analysisadmin/cadilines?line=TDR-15-002  Section 4.2.4.2 “CSC replacement of cathode front-end…”  Section 11.6 “Beam pipe” 12