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ATLAS Forward Protons: Fast Time-of-Flight Detectors Michael Rijssenbeek – Stony Brook University for the ATLAS Forward Proton group. Quartic - the ATLAS Forward Proton Fast ToF Detector see also next talk: Diamond detectors by Gabriele Chiodini ( Universita del Salento ). - PowerPoint PPT Presentation
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17JUL13 1
ATLAS Forward Protons:Fast Time-of-Flight
DetectorsMichael Rijssenbeek – Stony Brook Universityfor the ATLAS Forward Proton group
• Quartic - the ATLAS Forward Proton Fast ToF Detector
see also next talk: Diamond detectors by Gabriele Chiodini (Universita del Salento)
2AFP Time-of-Flight
ATLAS Forward Timing Detectors
Collaborating Institutions:Canada: U Alberta (CFD, HPTDC), U Toronto (Detector mounting); France: Saclay (SAMPIC RO chip)Germany: U Giessen (Radiators)Italy: Lecce, Roma2 (Diamond R&D)Portugal: Lisbon U (Trigger)
USA: U Texas at Arlington (Detectors, MCP-PMT), Oklahoma State U (RO – Optoboards), U New Mexico (Irradiation), SLAC (Readout), Stony Brook U (Electronics, Readout, RPs)
AFP Time-of-Flight Project Leader: Andrew Brandt (UTA)
Many Thanks to all my colleagues for fruitful collaboration and help!
17JUL13
3AFP Time-of-Flight
AFP – ATLAS Forward ProtonsAFP measurements:• Tag and measure momentum of intact protons from interactions
seen in the central ATLAS detector• Soft QCD (Diffraction) in special low/medium-luminosity runs
– avoid backgrounds from additional interactions in the same BX μ≃1• cross sections are rather high: many pb’s• need clean interactions in ATLAS, i.e. low pile-up
– need ~3 weeks-equivalent of data taking at μ≃1 (or ~1 week at μ≃3 ?)• at μ>1, require proton time-of-flight measurement to correlate forward
protons with interaction vertex measured in central ATLAS detector σt=30 ps ⇔ σz=7 mm
• Hard Central Diffraction in standard running (μ~50)– huge background from pile-up: 1 proton per side in each BX from soft
QCD (Single Diffraction, etc.)• pile-up suppression requires precise proton time-of-flight measurement.• any increase spatial and temporal granularity improves efficiency and
rejection17JUL13
AFP
206
AFP
214
AFP
214
AFP
206
4AFP Time-of-Flight
Fast Time-of-FlightMain CEP background: overlap of SD protons with non-diffractive events = ‘pile-up’ backgroundReduce by:– central mass matching:
• Mcentral = MAFP = (s ξLeft ξRight)½
– ToF:• zvtx = c(tLeft – tRight)/2
• E.g.: σt = 10 ps σzvtx = 2.1 mm
–not a new idea; FP420:
17JUL13
σt =20 ps: 0.1σt =10 ps: 0.5MX >800: 0.05
5AFP Time-of-Flight
Diffractive Protons in AFPNumber of protons per 100 fb–1 (~1 LHC yr) per Si pixel (50 μm × 250 μm):
– Proton energy loss ξis related to x:
– Central Mass M is related to both protons’ energylosses ξ1, ξ2 :
17JUL13
AFP 1 22
e.g. 0.01 160 GeV
beamM p
M
----- detector area
(20 mm × 20 mm)
6AFP Time-of-Flight
Hamburg Beam PipeATLAS design: Be floor and windows in Al structure• Tilted windows (11) minimize beam coupling and losses• Beryllium windows and floor, and Al structure
minimize interactions and multiple scattering• Ample space for tracking and timing devices
Results of detailed RF simulations:• Impedance Zlong is at the level of 0.5%/station at 1 mm from the beam
• Similar for Ztrans
• Power loss (heating) is manageable ~30 W, mostly in conical sections• Bellows are not yet included, but we are confident we can minimize
their effect17JUL13
ALUMINUM - AUSTENITIC STEEL FLANGEs
ALUMINUM
BERYLLIUM
450 mm
thin
AFP Time-of-Flight
AFP Roman Pot & StationAFP Pot adaptation from TOTEM design–shown with a possible timing detector …
Copy RP Station design of ALFA & TOTEM:–Ample operational experience –Known cost and construction & installation procedures
17JUL13 7
AFP Pot
beamAFP timing
TOTEM horizontal RP
station(beam view)
8AFP Time-of-Flight
Major Development Challenges
• MCP-PMT Rate and Lifetime: – Have tube capable of 5 MHz and 5 C/cm2 (equivalent to 50
fb–1 !) – expect further 2-3× improvement
• HPTDC board capable of 15 MHz• 5 ps resolution CFD• Clock Distribution Circuit <5 ps
• All achieved !
17JUL13
9AFP Time-of-Flight
AFP Fast Time-of-FlightQUARTIC concept: Mike Albrow for FP420 (joint ATLAS/ CMS effort) (2004) based on Nagoya Detector. – Initial design (~2006):
4 trains of 8 Q bars: 6mm × 6mm ×100mm
– mounted at Cherenkov angle θČ 48°≃
– Isochronous – Cherenkov light reaches tube at ~same time for each bar in a train
– arrival time of proton is multiply measured: bar + readout resolution less stringent!• e.g 30 ps / bar 11 ps for train of 8 bars
2011 DOE Advanced Detector Research award for electronics development:
17JUL13
proton
Č ph
oton
s
MCP-PMT
trains
1 2 3 4
θČ
SMApigtails
PA-b Programmable Gain Amp CFD Daughter Board
HPTDC Board8-Channel Preamplifier (PA-a)
Detector & PMT R&D: U Texas at Arlington (A. Brandt et al.); Electronics R&D: Stony Brook (M.R. et al)
AFP Time-of-Flight
Electronics Layout Phase 0Baseline layout (8×8 channels/side):
if the CFD is sufficiently radiation-hard, it can be located at 214 m
if the HPTDC is sufficiently radiation-tolerant, it can be located at 214 m
17JUL13 10
QuarticFeed
through
(32 ch REDEL-HV)8× HV
64× Signal
8× Temp
2× Pressure
(SMA)
(μD)
AFP2crate
SignalsAtt
DCS
Trigger
RR13 ?crate
USA15cratesTrigger (LMR600)
TDCToT
OptoBoard
DCSDCS
BOC-RODor RCE
CTF
DCS
iseg HV
LV+6V 5A
(50 Ω)CFDToT
LE
Data
LV+6V 20A
DCS
PA-a
PA-b
214 m 214 m 240 m 0 m
11AFP Time-of-Flight
Beam Test – FNAL 2012 (A.Brandt, UTA)
30 mm long Quartz bar // beam read by SiPM: σt ≃ 10 ps for a SiPM (CFD only!)– excellent resolution! – not very radiation hard
2 mm wide × 6 mm deep (in beam direction) Quartz bar positioned at 48° with beam (Cherenkov angle),read by 10 μm pore MCP-MAPMT– single bar: σt ≃ 20 ps (CFD only!)
• 4 bars at 48° (~32 mm): expect ~10 ps
– single bar with HPTDC: σt ≃ 26 ps• 6 bar train measurement (Test Beam): ~11 ps
– rad hard tube (no degradation seen yet up to 5 C)
Multiple measurements ‘tunable’ resolution, size, and interaction length …
17JUL13
SiPM1 – SiPM3
SiPM3 – Qbar3
12AFP Time-of-Flight
MCP-PMT Life Time (A.Brandt, UTA)
• Historically MCP-PMT’s have not been extremely robust, their performance (QE) degrades from positive ion feedback
• UTA Formed a collaboration with Arradiance and Photonis for coating …
17JUL13
12
Hamamatsu ion barrier SL10
Arradiance 10 (25) m pore Planacon
15
16
17
18
19
20
215E4 Gain
1E5 Gain
Laser Rate (MHz)
δt (
ps)
20 ps single bar resolution at 5MHz proton rate (10 pe per proton) at 5E4 gain; x3-5 better with 10 m pore tube
• Lehman et al. (Panda): As of 5/13 no loss in QE with Q>5 C/cm2!
• >10× improvement over typical tube 1C~10 fb-1
• expect 3× more with next version
13AFP Time-of-Flight
T958 DAQ FNAL 2012
17JUL13
2 3 4 5 6 7 Avg
Using a 20-ch, 20 GHz, 40 GS/s (25ps/point) 500k$ LeCroy 9Zi scope! Thanks for the loan LeCroy !
Time difference between SiPM and average of 6 Q-bars: σt = 20 ps (SiPM: σt =14-15 ps) (A. Brandt, UTA)
14AFP Time-of-Flight
Timing System ResolutionReached and extrapolated timing resolution:– Currently at 11-12 ps (Fall 2012 Test beam) with 6 bars; – ultimate performance of this system is probably about 8 ps
17JUL13
Component σt (ps)
Current
σt (ps)
Projected
Action
Radiator/MCP-PMT(~10 pe’s with 10 µ pore MCP)
19 17 Optimize radiator
CFD 5 5 Larger dynamic range HPTDC 18 <9 New HPTDC chipReference Clock 3 3 -Total/bar 27 20Total/ detector (6 ch) 11 8 -
15AFP Time-of-Flight
Time of Flight in Roman Pot• Bend the Quartic bars by 90°
–disadvantage: loose light in the bend–advantage: extra degree of freedom in
projecting the bar onto the MA-PMT !
• Note: the Quartic concept is modular; –make ‘trains’ of ‘arbitrary’ length (limited by λint) choose σt
–choose granularity: make trains of arbitrary width• beam test: 2 mm wide bar has same resolution as a 6 mm wide bar
–optimize ToF detector’s size vs. σt vs. λint!
• Possibility: make the light guide part of the bar into a mirrored air-guide!–reduce amount of material exposed to particles–reduce dispersion compared to quartz
17JUL13
16AFP Time-of-Flight
Quartz vs. Air Light Guide …Simulations by Libor Nozka (Prague):• run 0: straight Q-bar 150 mm long• run 5: Bent Q-Bar 30/120 mm with mirror
on elbow (R=90%)• run 6: Q-bar 30 mm + bent Air guide
120 mm with mirror on elbow (R=90%)
(R = reflectivity of air guide)
17JUL13
straight Q-bar 15 cm
bent Q-bar 3+12 cm Q-bar 3 cm + bent airguide12
cm
ns
ns ns
this design gives σt 20≃ ps in beam test
17AFP Time-of-Flight
Diffractive Protons in AFPNumber of protons per 100 fb–1 (~1 LHC yr) per Si pixel (50 μm × 250 μm):
– Proton energy loss ξis related to x:
– Central Mass M is related to both protons’ energylosses ξ1, ξ2 :
17JUL13
detector area (20 mm × 20
mm)
1 22
e.g. 0.01 160 GeV
beamM p
M
18AFP Time-of-Flight
Efficiency & BackgroundsRoyon, Sampert confirm pixellation of ~10 rows is adequate:– inefficiency per train:
17JUL13
7 trains:2, 6×3.25 mm
10 trainsof 2 mm width
20 trainsof 1 mm width
19AFP Time-of-Flight
New Nuclear Interaction Studies
Concerns:–Scattering in first (upstream) station
• this destroys proton which will neither be tracked nor timed global inefficiency
• In case where this proton was kinematically disallowed it might create another proton inside the 2nd station’s acceptance
–Scattering in the thin ‘floor’, spraying ‘sideways’ into the detector inside
–At 14 TeV find about λInt≃2% per Q-bar (~8 mm of quartz)• 15% of events have an interaction by bar 8• These interactions have a high multiplicity
–Too many particles in quartz bar (shower) would saturate amps• dynamic range about 8-10• O(10s) particles, which would saturate amps and cause that bar (and
following) timing to be mismeasured– Time over Threshold functionality allows some recovery …
All above influence the timing detector optimization17JUL13
Tom Sykora et al.
20AFP Time-of-Flight
Severe Backgrounds at the LHC
Sources:1. IP: single diffraction pile-up2. secondary interactions in upstream beam elements3. Beam Halo
Low-μ (special) runs: backgrounds are OK– see: ALFA runs at β* = 90 m, 1 km
– OK for the soft diffraction program of AFP
High-μ (standard) runs: backgrounds are very high– see: TOTEM standard-optics runs (Joachim Baechler’s talk)
• evidence that the source is primarily IP and secondary interactions in collimators (1 & 2)
– we are analyzing recently recovered ALFA run at β*=0.55 m (15’ run, 2 Mevts)
– we are simulating the high-μ environment with β*=0.55 m optics …
17JUL13
dominant !
Horizontal RP Rate at 14 s
56-F 45-N 45-F
Rate for 1368 b with beam separation
2 MHz 1 MHz 3 MHz(incl. showers from N)
separation lumi factor
1 / 15.7 1 / 18.6 1 / 22.6
Rate for 1368 b without separation
31 MHz 19 MHz 68 MHz(22.6* 3 MHz)
Rate for 1 bwithout separation
23 kHz 14 kHz 50 kHz
Hits per bxw/o separation
2.0 1.2 4.4(50 kHz/11.2kHz)
Beam conditions (fill # 3288):1.6 x 1011 p/bE = 4 TeVb* = 0.6 men = 2.8 mm radm = 31 (without separation)L = 6.7 x 1033
expected SD rate per arm within acceptance: ~ 0.4 / bx (event rate / bunch crossing)
Revolution frequency: 11.2 kHzaverage crossing rate : 11.2 * 1368 = 15.3 MHzaverage interaction rate (without separation) : 15.3 * 31= 47.4 MHz
Expected ratesafter LS1 are different(L, bunch scheme)
insertion at low β*beam heating – LHC vacuum – RP optimization-
rates
from: Joachim
Baechler’s talk of
yesterday
17JUL13 21
22AFP Time-of-Flight
Summary• AFP has a baseline fast timing detector
–10 ps or better resolution for 8 Q-bars–Long-lifetime MCP-PMT–Electronics
• Optimization in progress:–Needs for μ≃1 physics–Backgrounds and efficiency …–Housing in a Roman Pot ?–Triggering
17JUL13
23AFP Time-of-Flight
Backup Slides
17JUL13
24AFP Time-of-Flight
AFP – HBP plus Tracker …
17JUL13
thin floor sensors
evaporativecooling
readout flex
ATLASA
FP206
AFP
214
AFP
214
AFP
206AFP
AFP Time-of-Flight
AFP POT Modifications • AFP needs changes in the POT design:
– the TOTEM design has a different thin window size, not optimally matched to our acceptance
– the TOTEM floor is a groove in the pot bottom: • requires a bump-out of the tracking sensor, • making it difficult to insert a Quartic detector close to the beam …
• We have more time than TOTEM use to investigate improvements– We should make the AFP pot a bit larger (to ~144 mm) by reducing the 2.5 mm
gap between the bellows and the pot itself to ~1 mm. • Making it even larger than that requires a different ‘Tee’ design and RF calculations will
have to be repeated to validate a larger cylinder. Unless absolutely necessary, I would prefer to keep the pot to 144 mm ID.
– We should investigate alternative pot and window materials, coatings, etc. • e.g., a Be window of 200-400 μm thickness welded to an Al pot (cfr. Daniela) would be a
huge improvement over the current TOTEM pot in terms of conductivity, radiation length (MS), and interaction length.
• Need our own feedthrough plate with the services as we require them, adapting the plate as designed for TOTEM to AFP needs.
• Possibly the plate for the ‘timing’ will be different from the plate for the ‘tracking’17JUL13 25