1. Sotiris Vlachos
BGV Status and Plans

2. The BGV core Team BE-BI-BL LHCb M. Ferro-Luzzi B. Dehning C. Barschel
A. Alexopoulos
E. Bravin
B. Würkner
Q. Veyrat
S. Vlachos
(+ considerable support from
the BE-BI community)
LHCb
M. Ferro-Luzzi
C. Barschel
O. Girard
G. Haefeli
P. Hopchev
R. Jacobsson
A. Kuonen
M. Rihl
(+ considerable support from
the LHCb community)
Full collaborator list:
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3. Demonstrator built around Beam 2, in Pt4
Beam Gas Vertex Detector Non destructive beam size measurement for HL-LHC not limited by accelerator luminosity
Tracks from beam-gas interactions to reconstruct beam spot, 10-8 mbar injected at interaction volume
Should allow beam spot size (and hence ε) measurements with precision <10% (5 minutes integration time)
Demonstrator built around Beam 2, in Pt4
Expect first real-time beam profile measurements for 2017 pp runs
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4. Beta functions in LHC point 4
at ~ -220m , beam 2 has x  y  150 m
at 7TeV and N  2.5μm, beam  0.22 mm
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5. More information
Details on detector requirements and description of subsystems can be found at: 9--BITechBoard.pdf (BE-BI TB presentation Nov 2015) In addition all BGV information can be found in the dedicated twiki page :
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6. DETECTOR STATUS
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7. BGV Status and Plans Summary
Demonstrator Status
Detector fully commissioned
SciFi detector planes
Read-out chain and CPU farm
Trigger system
Control and DAQ s/w
Cooling system functional, -25℃
Dead channels ~ 0.3%
Gas injection system operational
Several data-taking campaigns during 2016 with various beam conditions
Off-line analysis in good progress
Next steps
Offline analysis: high precision track and vertex reconstruction
Implement analysis software in the BGV online CPU farm for real-time beam profile measurement
Establish data logging and measurement publishing towards CCC
Further upgrades for BGV demonstrator:
Faster trigger electronics + extra scintillators for optimal Beam2 identification
Additional fast detector plane (time resolution ~40ps) for z profile reconstruction
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8. BGV Control and Operation
A typical entry from the BGV e-log:
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9. (i.e. 25ns coincidence window)
BGV Trigger
Veto Counters
L0 Counters
(i.e. 25ns coincidence window)
1500V
1800V
Scintillator Relative timing
Scintillator Amplitudes
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10. BGV read-out TELL1 : Cluster finder (zero-suppression)
HLT farm : Full reconstruction program
Currently reading out non zero suppressed data to define optimal algorithms
(hence R/O rate limited to ~ 1KHz)
Full (16 blades) HLT farm and ZS data will allow a DAQ rate of ~1MHz
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11. Cooling System
Julabo Chiller in service tunnel and all piping to BGV detector installed. Detector currently -25℃
Cooling fluid leak rate < 200ml/month : Can safely operate between TSs
Next steps:
Incorporate Chiller control in BGV WinCC system for monitoring and data logging
Dry Air interlock
Cooling system Upgrade if lower temperatures are needed:
Install closed circuit for C6F14 with heat exchanger and secondary cooling with chiller
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12. DATA ANALYSIS
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13. Estimation of beam spot size
Three methods under study to analyze BGV data
Approximate beam-gas vertices by finding close-by tracks (fastest approximation)
Use track and impact parameter correlations to measure beam position and width (accurate measurement without vertex fitting)
Exact vertex reconstruction(most precise method)
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14. Track reconstruction – Real data
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15. Distance of closest approach (DOCA)ɸ
d (Distance Of Closest Approach) x y
REAL DATA
This is a x-y projection of the beam-gas interaction volume.
DOCA is calculated in 3-d and hence one obtains also a
POCA (Point of Closest approach) : (x,y,z)
Calculation done with respect to (0,0,z)
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16. Beam-gas interactions POCA z-distribution
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17. DOCA based vertex approximation
Vertex seed : a pair of tracks with relative DOCA < 1mm
Add tracks with relative DOCA < 1mm and form new seed until list of tracks is exhausted
Use each track only once
Monte-Carlo Simulation
(1,1) with σ = 0.15mm
Real Data
Blue: Generated, Black: Reconstructed (x,y)
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18. Beam position and DOCA-ɸ correlation
Real primary vertex position (instead of (0,0)) ɸ
DOCA y0
DOCA = x0sin(ɸ) – y0cos(ɸ) x0
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19. Simulation results DOCA vs ɸ
Beam spot (0,0)
x = mm
y = mm
Beam spot (1,1)
x = 0.84 mm
y = 0.81 mm
Note: Outliers cause underestimation of (x,y). Need better fitting function or calibration
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20. Real Data measurement: DOCA vs ɸ
NO ERROR ESTIMATION GIVEN
PRELIMINARY
Beam spot ~(o.01mm, 0.01mm)
NOTE: No alignment corrections implemented yet
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21. DOCA correlation vs σbeam
The event-by-event displacement due to finite σbeam affect all particles of a beam-gas interaction in the same way. Hence their DOCAs are correlated: <DOCA1DOCA2> = (σx2+σy2)cos(ɸ1-ɸ2)/2 + (σy2-σx2)cos(ɸ1+ɸ2)/2 σx (σy) being the beam spot variance along x (y) Assuming σx = σy : <DOCA1DOCA2> = (σbeam2)cos(ɸ1-ɸ2) Correlation does not depend on DOCA resolution (assuming all tracks come from the interaction vertex)
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22. DOCA correlation → σbeam
Monte Carlo Simulation
Real Data
NO ERROR ESTIMATION GIVEN
PRELIMINARY
Generated σbeam = 0.15mm
Fitted σbeam = 0.2mm
REAL DATA Fitted σbeam = 0.2mm
(Above distribution is yet an other indication of reconstructed tracks far from the interaction vertex)
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23. Analysis Next steps
Refine tracking performance – reduce outliers, improve efficiency
Use MC samples to estimate error and systematics on beam spot size and position estimation
Study detector coverage and method efficiency
Implement all necessary alignment corrections
Increased statistics and z-segmentation
In addition: Verify zero-suppression algorithm to be implemented in h/w
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24. Plans for 2017
Collect large data samples (with correct timing and trigger settings)
Optimize beam spot measurement
Implement measurement algorithm in HLT farm
Set-up communication with CCC
Increase number of CPU blades in HLT farm to allow for real-time measurements
Finalize ZS algorithm and program it in VHDL
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25. BGV UPGRADES
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26. BGV Upgrades Trigger Upgrade
New front-end electronics
CF discriminators
VME logic board for coincidence in narrow time window
Additional Scintillators Downstream to identify B2 (and separate from B1)
Additional fast detectors: MicroMegas based strip detector with ~40ps time resolution to allow reconstruction of beam bunch along z
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27. BGV Trigger Upgrade L0 Counters Veto Counters L0 Confirm
New trigger electronics
CF Discriminators
Delay and coincidence logic (~10ns coincidence window)
Additional scintillators (L0 confirm)
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28. MicroMegas ps detector
For reconstructing the z profile of a beam bunch : need ~60ps resolution
MM: small amplification gap ( μm)
fast signals (~ 1 ns)
short recovery time (~50 ns)
high rate capabilities (> MHz/cm2)
high gain (up to 105 or more)
Time resolution already achieved: <50ps
Anode can be in the form of wide (~cm) strips to match the BGV geometry
To be placed possibly at the L0 confirm support frame
For more details see BE-BI seminar:
MicroMegas detector applications for beam diagnostics
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29. Summary BGV H/W fully deployed – commissioned Beam spot reconstruction
Encouraging first results
Expected optimal resolution with full vertex reconstruction
Open issues:
Transport offline code to online system
Communication with CCC
BGV upgrades and deployment for B1
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30. BackUp
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31. 24/11/2016
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32. Radiation monitoring
6 PIN Diodes measuring directly on detector modules
Expected dose ~10Gy/year
(more details:
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33. BGV module Test Beam Measurements
Courtesy: O. Girard - EPFL
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34. DOCA – phi projection MC(1,1)
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