ATLAS Forward Protons: A (10)
Picosecond Window on the Higgs Boson
Andrew Brandt, University of Texas at Arlington
A picosecond is a trillionth of a second.
This door opens ~once a second, if it opened
every 10 picoseconds it would open a hundred
billion times in one second (100,000,000)
Light can travel 7 times around the earth in
one second but can only travel 3 mm in 10 psec
Yes, I know it’s a door, not a window!
January 12, 2010
Andrew Brandt SLAC Seminar
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Outline
Part I: Introduction to ATLAS Forward Proton
(AFP) proposal and physics motivation
 Part II: Details of the AFP fast timing system
January 12, 2010
Andrew Brandt SLAC Seminar
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ATLAS Forward Protons (AFP)
AFP: Proposes to use double proton tagging in conjunction
with the ATLAS detector as a means to measure properties of
Higgs (quantum numbers+mass) and other new physics
NEW
Central Exclusive Production (QCD)
Central Exclusive Production (QED)
3
CEP: Momentum lost by protons goes entirely into mass of central system
Central Exclusive Higgs
AFP concept: adds new ATLAS sub-detectors at 220 and 420 m
upstream and downstream of central detector to precisely measure the
scattered protons to complement ATLAS discovery program.
These detectors are designed to run at a luminosity of 1034 cm-2s-1 and
operate with standard optics (need high luminosity for discovery physics)
beam
420 m
LHC magnets
p’
AFP Detector
220 m
H
p’
You might ask: “Why build a 14 TeV collider and have 99% of your energy taken
away by the protons, are you guys crazy or what??”
The answer is “or what”!—ATLAS is always (or at least for a few weeks last
December) losing energy down the beam pipe, we just measure it accurately!!!
Note: the quest for optimal S/B
Ex. The leading discovery channel for light4 SM
can take you to interesting places: Higgs, H , has a branching ratio of 0.002!
SM Higgs Branching Ratio
• We know (we think)
that the Higgs gives
particles mass through MH= 140 GeV
Br ( H  bb )  Br ( H  WW *)
their coupling to the
Higgs field
• Theory constraints
imply that the Higgs is
“light” < 200 GeV
(not soooo light)
Br ( H   )  0.002
•Various channels
contribute discovery
sensitivity depending on
the exact Higgs mass
Andrew Brandt SLAC Seminar
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AFP Evolution
• 2000 Khoze, Martin, Ryskin (KMR): Exclusive Higgs prediction
Eur.Phys.J.C14:525-534,2000, hep-ph/0002072
• 2003-2004: joint CMS/ATLAS FP420 R&D collaboration forms
• 2005 FP420 LOI presented to LHCC CERN-LHCC-2005-0254
“LHCC acknowledges the scientific merit of the FP420 physics
programme and the interest in exploring its feasibility”
• 2006-2007 Significant R&D funding in UK, modest funding in U.S.
and other countries, major technical progress, RP220 formed
• 2008 RP220 and AFP420 merge to form AFP, R&D continues,
Cryostat design finalized with CERN, LOI to ATLAS submitted
• 2009 “AFP year in review”, FP420 R&D document published in
J. Inst (2009_JINST_4_T10001)
• Nov. 2009 ATLAS approves AFP to develop a Technical Proposal
January 12, 2010
Andrew Brandt SLAC Seminar
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Who is AFP?
Institute
University of Alberta
Charles University, Prague
Institute of Physics
IRFU-SPP, CEA Saclay
Justus-Liebig-Universität Giessen
Calabrian University
Institute of Nuclear Physics, Cracow
Glasgow University
Manchester University
Cockcroft Institute/Manchester University
Rutherford Appleton Laboratory - PPD
Rutherford Appleton Laboratory - EID
University College, London
University of Texas at Arlington
State University of New York (StonyBrook)
Country
Canada
Czech Republic
Czech Republic
France
Germany
Italy
Poland
UK
UK
UK
UK
UK
UK
USA
USA
Other institutions have expressed interest—there is plenty to do!
January 12, 2010
Andrew Brandt SLAC Seminar
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What is AFP?
1) Impressive array of rad-hard edgeless 3D silicon detectors (same
sensors to be used in IBL upgrade) with resolution ~10 m, 1rad
2) Timing detectors with ~10 ps resolution for overlap background
rejection (SD+JJ+SD)—more on this in Part Deux
3) New Connection Cryostat at 420m
4) “Hamburg Beam Pipe” instead of Roman Pots
AFP is a rather vanilla name for this precision instrument:
I prefer VF3DSPDwithPST!
(Very Forward 3-D Silicon Proton Detector with Picosecond Timing)
For more information: e-mail me at brandta@uta.edu
or better yet, come to bonus session Su Dong has arranged
at 3 pm
January 12, 2010
Andrew Brandt SLAC Seminar
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AFP in Pictures
Timing
to reject
Newdetectors
connection
cryostat
where protons
and
Movable beam pipe background
with integrated
movable
system
from3-D
different
houses 3-D silicon andcentral
beam
pipecome
houses
Test Beam
interactions in same bunch crossing
timing detectors
silicon and timing detectors
proton
1 Cryostat (warm-cold transition)
2 Support table for movable beampipe
3 Detector station
4 Vacuum valve
January 12, 2010
Andrew Brandt SLAC Seminar
QUARTIC
9
What does AFP Provide?
Acceptance >40% for wide
range of resonance mass
Combination of 220
and 420 is key to
physics reach!
420420
420220
220220
• Mass and rapidity of
centrally system
M  12 s
1
y  ln(1 /  2 )
2
• where 1,2 are the
fractional
momentum loss of
the protons (ex. =0
for elastic proton)
• Mass resolution of
3-5 GeV per event
Allows ATLAS to use LHC as a tunable s glu-glu or  collider
10
while simultaneously pursuing standard ATLAS physics program
What is Special about CEP?
Typical
Higgs
Production
+
“
pp  gg  H +x
”
=
“
”
CEP
Higgs
pp p+H+p
• Extra “screening ” gluon conserves color, keeps proton intact (and reduces your )
• CEP defined as ppp+X+p , where protons are scattered at small angles, but remain
intact, with all of their lost energy going towards production of the system X
• Central system produced in Jz=0++ (C-even, P-even) state, this results in di-quark
production being suppressed
• More importantly: if you observe any resonance (for ex. Higgs), you
automatically know its quantum numbers are 0++
January 12, 2010
Find a CEP resonance and you have
measured its quantum numbers!!
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Does CEP Process Exist?
CDF
says
yes!
1) Observation of Exclusive Dijets : (CDF) PR D77, 052004 (2008)
σ(excl, jetETmin = 15 GeV) 112+84-50 pb. In agreement with
ExHuME MC which incorporates Khoze, Martin, Ryskin (KMR)
model for CEP (x3 theor. uncertainty)
Why we care: same diagram as Higgs but with u/d loop
instead of top loop
2) Observation of Exclusive χc : (CDF) PRL 102, 242001 (2009)
dσ/dy(y=0) = 76 +/- 10 +/- 10 pb. Prediction (KMRS) = 90 pb
Why we care: same diagram as Higgs but with c loop instead of top loop
These support the prediction of KMR for standard model Higgs at the LHC (3 fb @ 120 GeV)
Phenomenological Studies
of BSM Higgs
Since the KMR SM Higgs cross section prediction is pretty small: ~3fb, most
of the recent theoretical work has focused on BSM Higgs, which can lead to
enhanced cross sections for pp  pHp H  bb
1) MSSM (H->bb, H->ττ, H->WW*)
– Heinemeyer, Khoze, Ryskin, Stirling, Tasevsky, Weiglein [Eur.Phys.J.C53:231-256,2008]
– Cox, Loebinger, Pilkington [JHEP 0710:090,2007]
2) NMSSM (H->4τ)
– Forshaw, Gunion, Hodgkinson, Papaefstathiou, Hodgkinson, Pilkington [JHEP 0804:090,2008]
3) CP-violating Higgs sector (H->bb, H->ττ)
– Ellis, Lee, Pilaftsis [Phys.Rev.D71:075007,2005]
– Cox, Forshaw, Lee, Monk, Pilaftsis [Phys.Rev.D68:075004,2003]
4) Triplet Higgs (H->bb)
– Chaichian, Hoyer, Huitu, Khoze, Pilkington [JHEP 0905:011, 2009]
I will go through a few details of MSSM
and then get back to the SM Higgs
January 12, 2010
Andrew Brandt SLAC Seminar
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MSSM Higgs sector
• In order to implement electroweak symmetry breaking into the MSSM,
two Higgs doublets (H1, H2) are needed.
8 degrees of
freedom
3 are absorbed from the
H mechanism and give
masses to W± and Z (as
for SM Higgs)
5 physical
Higgs
bosons

2 CP even (h, H), 1 CP odd (A) and 2 charged H±

The MSSM Higgs sector (at tree level) is determined by 2 free
parameters: MA and tanβ=v2/v1 ( the ratio of the vacuum expectation values of
the 2 Higgs doublets)
Courtesy of Giorgos Dedes Seminar : Physik am Large Hadron Collider (LHC)
January 12, 2010
Andrew Brandt SLAC Seminar
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MSSM and CEP
Models with extended Higgs sectors, such as the MSSM, typically
produce a light Higgs (h) with SM-like properties and a heavy
Higgs (H) which decouples from Gauge boson. This implies:
•no HVV coupling (V=W, Z)
R=(MSSMH)/(SMH)
tan  H→bb, mhmax,
• no weak boson fusion
μ = 200 GeV
• no HZZ
R=300
• big enhancement in
H  bb
H  
• pseudoscalar A does not
couple to CEP
mA (GeV)
For the MSSM and related models, AFP is likely to provide the only
way to determine the Higgs quantum #’s and the coupling to b-15
quarks, and will provide an excellent mass measurement.
MSSM Higgs discovery/exclusion
• Heinemeyer et al.
studied CEP
coverage of MSSM
parameter space in
mA-tan plane.
• Plots show the 5σ
contours for the light
Higgs scalar boson
(above) and heavy
(below) for 60fb-1 and
600fb-1.
• For large tan , Tevatron
can already exclude part
of the region.
h/H→bb, mhmax, μ = 200 GeV
TeV
LEP
5 contours, Hbb
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Observing Higgs in the MSSM
Cox. et.al. (JHEP 0710:090,2 007)
Better pileup rejection
• Pick: tan=40, mA=120 GeV, mh=120 GeV (MSSM h/SM H =8) and do detailed
analysis including experimental efficiencies determined using TDR resolutions.
January 12, 2010
Andrew Brandt SLAC Seminar
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H4 in the NMSSM
• NMSSM Higgs sector consists of 3 neutral scalars and 2 neutral
pseudo-scalars (and charged Higgs).
• Most ‘natural’ part of parameter space results in light scalar Higgs
(~100 GeV) Haa (`a’ is lightest pseudo-scalar)
• Preferred decay of pseudo-scalar is a (thus two a’s4 taus).
• ATLAS standard search channels are difficult and likely
cannot measure the Higgs quantum numbers
• Predict approx 7 CEP events after ~100fb-1 with no appreciable
background (JHEP 0804:090,2008). (Trigger on e tau decays)
• BONUS: information from forward protons gives good
pseudo-scalar mass measurement!
January 12, 2010
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HWW* in the SM and MSSM
• Cox et.al. (Eur.Phys.J.C45:401407,2006) showed that the semileptonic decay of SM HWW* was
Enhancement with respect to SM
possible for 130< mH <200GeV,
using single muon/electron
triggers for 30fb-1 of data.
• Also have golden fully leptonic
decay channel: small signal but
negligible background.
• Note: in the MSSM, cross section
can be enhanced for lighter Higgs
boson in the WW* channel as well
by up to a factor of 4 relative to SM
cross section.
January 12, 2010
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AFP Internal Studies
• AFP manpower primarily dedicated to detector R&D and technical studies, however…
• We performed ATLFast and Full Sim studies over the last few years to validate
the predictions choosing 120 GeV for H  bb and 160 GeV for H  WW *
•We validated the exclusivity cuts needed to reduce the overlap background, including
tracking rejection with full detector simulation, trigger studies etc., but I can’t tell you
about that yet!
January 12, 2010
Andrew Brandt SLAC Seminar
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Central Exclusive Photon-Photon
Does it exist? Yes. Q.E.D. (a little Latin humor)
Exclusive two-photon processes are characterized by
exchange of virtual photons from protons. Photon fusion
results in a system X of particles centrally produced and
two intact protons, scattered at small angles.[1]
For pair production, significant crosssections (fb-level) are expected [2], with
clean and unambiguous final states.
Offers a novel possibility for the search of
BSM particles
[1] K. Piotrzkowski, Phys.Rev.D63(2001) 071502:
Tagging two-photon production at LHC
[2] Louvain photon group, arXiv: 0908.2020,
High-energy photon interactions at the LHC
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Anomalous Quartic Gauge Couplings
Event counting: for AFP trigger on 2 high pT leptons (WW)
95% CL limits for the AQGC
for L=30fb-1:
LEP
(Opal)
ATLAS
no AFP 1)
ATLAS
w/AFP 2)
aoW /  2 2 x 10-2 2 x 10-5
2.6 x 10-6
acW /  2 4 x 10-2 3.2 x 10-5
9.4 x 10-6
 >103 improvement over LEP
limits, and 3-8x ATLAS w/o AFP
•The inclusion of AFP is critical for rejection of background from partonparton production of W pairs. (cross-section x BR x lepton acceptance = 1pb)
•Potentially sensitive to Higgsless models or other new physics
1)
2)
P.J. Bell, arXiv:0907.5299
22
C. Royon, E. Chapon, O. Kepka, arXiv:0909.5237 ; O. Kepka,, C. Royon, (DAPNIA, Saclay) Phys. Rev.
D78:073005,2008.
Charged SUSY Production
• Photon-photon production of charged SUSY pairs
investigated in arXiv:0806.1097.
• Benchmark points consistent with WMAP data examined.
• Fully leptonic final states considered:
– Two forward protons measured in forward detectors
– Two leptons with opposite charge. (pTe > 10GeV, pT > 7GeV).
5 discovery with
25 fb-1 for light
SUSY scenarios
23
N.Schul and K.Piotrzkowski, arXiv: 0806.1097, Detection of two-photon exclusive production of susy pairs at the LHC
But Wait, There’s More…
• CEP dijets: measure unintegrated PDFs and can be used to calibrate
jet energy scale
• Diffraction: extends studies at HERA and Tevatron on dPDFs, survival
probabilities (relevant to VBF)
• Hard SD and DPE: dijets - sensitive to gluon dPDFs
SD B-meson -sensitive to gluon dPDFs
SD W/Z - sensitive to quark dPDFs
SD Top – because we can
• p: jet production to study the factorisation breaking in direct and
resolved processes observed by H1, extend to xp<0.1
• single top: measure CKM matrix element V_tb
• anomalous single-top: study anomalous single-top coupling
• Odderon interaction in 
• Charged Higgs in 
January 12, 2010
Andrew Brandt SLAC Seminar
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AFP Summary
AFP will provide ATLAS with a new sub-detector enabling a rich
complementary physics program (our physics is your physics)
Central Exclusive Production (QCD)
• With sufficient luminosity, BSM Higgs bosons can be observed in
CEP in a variety of mainstream models, many of them non-trivial for
standard ATLAS techniques
• The WW* channel looks very promising for SM Higgs of 130 GeV or above.
• CEP provides excellent mass resolution
• Observing CEP Higgs determines quantum numbers (0++)
Central Exclusive Production (QED)
• Superb anomalous quartic gauge coupling sensitivity could uncover new physics
• Complementary SUSY sensitivity .
Plus a variety of SM physics and speculative physics. Note: theoretical
investigations of AFP capabilities are still in early stages.
January 12, 2010
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FP420/AFP Fast Timing
WHO?
UT-Arlington (Brandt), Alberta, UC-
WHY?
Background Rejection for Diffractive Higgs
London, Prague, Saclay, Stonybrook,
Giessen, Manchester, Fermilab, Louvain,
Kansas
Ex: Two b-jets from one interaction and two protons from another
How?
How Fast?
January 12, 2010
Use time difference between protons
to measure z-vertex and compare
with tracking z-vertex measured
with silicon detector
10 ps or better (to get x20 rejection)
Andrew Brandt SLAC Seminar
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Ultra-fast Timing Issues
Time resolution for the full detector system:
1. Intrinsec detector time resolution
2. Jitter in PMT's
3. Electronics (AMP/CFD/TDC)
4. Reference Timing
•
•
•
•
•
3 mm =10 ps
Radiation hardness of all components of system
Lifetime and recovery time of tube
Backgrounds
Multiple proton timing
January 12, 2010
Andrew Brandt SLAC Seminar
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Timing System Requirements
• 10 ps or better resolution
• Robust: capable of operating with little or no
intervention in radiation environment (tunnel)
• High efficiency
• Acceptance over full range of proton x+y
• Segmented (multi-proton timing)
• Two main options:
1) one very precise measurement (GASTOF)
2) multiple less precise measurements (QUARTIC)
January 12, 2010
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FP420/AFP Timing
Two types of Cerenkov detector are
employed:
QUARTIC – two QUARTIC
detectors each with 4 rows of 8
fused silica bar allowing up to a
4-fold improvement over the
single bar 40 ps measurement
GASTOF – a gas Cerenkov
detector that makes a single 10
ps measurement
Both detectors use Micro
Channel Plate PMTs
(MCP-PMTs)
January 12, 2010
Andrew Brandt SLAC Seminar
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Micro-Channel Plate
Photomultiplier Tube
(MCP-PMT)
e
-
+
+
photon
Faceplate
Photocathode
Photoelectron
Dual MCP
DV ~ 200V
DV ~ 2000V
Gain ~ 106
MCP-PMT
DV ~ 200V
Anode
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ATLAS Solution: Option 2)
• Choosing multiple measurements with modest
resolution on 30-40 ps scale simplifies requirements
in all phases of system
1) We have a readout solution for this option (later)
2) We can have a several meter cable run to a lower
radiation area where CFD’s can be located, while
TDC’s can be located even further away (the cable
distortion is much more significant for sub-10 ps
measurement)
3) Segmentation is natural for this type of detector
January 12, 2010
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QUARTIC Ray Tracing
15mm Quartz/75 mm air
~ 5 pe’s accepted in 40 ps
20 ps
90mm Quartz
~ 10 pe’s accepted in 40 ps
40 ps
40 ps
32
QUARTIC Prototype
Note: prior to June 2008 test beam, results marginal for QUARTIC 15mm bar:
80 ps/bar 80% efficient; allows you to reach close to 20 ps, but not 10 ps
HC
HH
HE
Testing long bars 90 mm (HE to HH) and mini bars 15 mm (HA to HD)
Long bars more light from total internal reflection vs. losses from
reflection in air light guide, but more time dispersion due to n()
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QUARTIC Timing 2008 CERN TB
Npe=(area/rms)2
56.6/1.4=40 ps/bar
using Burle 64
channel 10 m
pore tube including
CFD!
Dt
 t  ( t1 )2  ( t2 )2  2 t1
so if 1  2 then  t1   t / 2
Time difference between two 9 cm quartz bars after Louvain constant fraction
implies a single bar resolution of 40 ps for about 10 pe’s (expected 10 pe’s from
34
simulations). Need to demonstrate N (more later)
(a)All tracks
(b)Tracks with
(Bonn Silicon
Telescope)
a Quartz
bar on
6mm
(c)
Efficiency
Shape
due to
veto
counter
with 15mm
diameter
hole
Events
QUARTIC Efficiency CERN TB
6 mm
Use tracking
(b)/(a) to
determine that
QUARTIC bar
efficiency is
high and
uniform
35
Strip #
Timing Progress in 2009
•
•
•
•
Established UTA Picosecond Test Facility (PTF) for laser tests
Developed in depth understanding of MCP-PMT performance
Investigated rate and lifetime issues
Formed collaborations with Arradiance, Photek, and Photonis
(including submission of UK and UTA funding proposals)
• Built a new prototype detector
• Validated readout electronics
• Albrow obtains 20-30 ps for a single 90 mm QUARTIC bar with
single channel Photek 3 m pore PMT (T979 at FNAL)
January 12, 2010
Andrew Brandt SLAC Seminar
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Rate and Current Limits
• The baseline QUARTIC detector could see rates of up to 15 MHz in the
hottest 6mm x 6mm pixel of the MCP-PMT. If the current:
Anode Current = proton frequency x number of photo-electrons
generated by each proton x charge x gain
I  R Npe e G
is too high (~10% of strip current) the tube saturates (gain is reduced)
• To keep the current at tolerable levels, lower gain and less pe’s are
desirable, but precise timing requires as many pe’s as possible (and
conventional wisdom also indicated that high gain was necessary*).
Smaller pores both reduces the current in any one pore and improves
the timing
• With 10 pe’s expected for a QUARTIC bar, if a gain of 5x104 were
possible instead of the canonical 106(!), we would require a maximum
current of about 3 A/cm2, a factor of several higher than standard
MCP-PMT’s, but possible for new generation of Photonis MCP-PMT’s
37
*Stay tuned for laser test results!
Lifetime Issues
Lifetime due to positive ions damaging the photocathode
is believed to be proportional to extracted charge:
Q/year = I*107 sec/year
Q at maximum luminosity is up to 35 C/cm2/yr !
(assuming 5x104 gain!)
Without a factor of 20 reduction in gain, the current and
lifetime issues would make MCP-PMT’s unusable, with it
the rate is borderline, but lifetime off by a factor of 50—
tube dies every week!
Solution: Graduate student camps out in tunnel to exchange
38
tubes as needed. (Sorry Ian)
Lifetime Measurements
N. Kishimoto, et al., Nucl. Instr. and Meth. A 564 (2006) 204.
Relative QE as
function of
wavelength shows
damage is much less
in UV than visible
Barrier
Aluminum ion barrier layer on top
of MCP suppresses positive ions,
increases lifetime by x5 to 6
No barrier
Options for Improved Lifetime MCP-PMT
• Ion barrier, already demonstrated, this promises a factor 5 to 6 lifetime
improvement (at the cost of a 40-50% collection efficiency reduction)
• Electron scrubbing, already demonstrated internally by Photonis, promises
a factor 5 to 10 lifetime improvement
• Z-stack, already demonstrated, this promises a factor of 10 lifetime
improvement (A.Yu. Barnyakov, et al., Nucl. Instr. and Meth. A 598 (2009) 160)
• Arradiance coated MCP’s, to be demonstrated, this promises a factor of 10
or more lifetime improvement (Grants submitted by UTA and Manchester
to fund insertion of Arradiance MCP’s in Photonis and Photek tubes:
“Development of a Long Life Microchannel Plate Photomultiplier Tube for
High Flux Applications through the Innovative Application of Nanofilms”)
• Various combinations of these factors are possible and should give
multiplicative improvement factors, except for the electron scrubbing and
Arradiance coating, which would be expected to be orthogonal
January 12, 2010
Andrew Brandt SLAC Seminar
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Conclusions of Internal Lifetime Note
Combination of lower gain running and higher current tube
implies that expected rates/currents at 1034 are acceptable
with existing technology.
After accounting for lower gain running the discrepancy
factor for the lifetime required for tube to survive 1 LHC
year at 1034 luminosity is about a factor of 50 at 220 m as
current QUARTIC detector design require a 35 C/cm2
MCP-PMT
Pursuing the funding necessary to develop 50x longer life
MCP-PMT’s. Given the different possible lifetime options,
we have no doubt that this can be achieved with MCP-PMT
technology
January 12, 2010
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Laser Test Goals
• Develop flexible laser test facility
• Study properties of MCP-PMT’s
• Optimize electronics
 Some issues to address:
1) How does timing depend on gain ?
2) What is minimum gain for 10 pe’s? Need to validate low gain
operations.
3) What is maximum rate at which tube can operate?
4) Evaluate amp/CFD/TDC choices at detector working point
5) Eventually lifetime tests
January 12, 2010
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PTF
LeCroy Wavemaster
6 GHz Oscilloscope
Hamamatsu
PLP-10
Laser
Power
Supply
Picosecond Test Facility
featuring Undergraduate
Laser Gang (UGLG)
Undergraduate Laser
Youths? (UGLY)
Laser Box
mirror
beam splitter
MCP-PMT
filter
lenses
January 12, 2010
Andrew Brandt SLAC Seminar
laser
43
Timing vs Gain for 10 m Tube
Measured with reference tube using CFD’s and x100
mini-circuits amps, with 10 pe’s can operate at ~5E4 Gain
(critical for reducing rate and lifetime issues) With further
optimization have obtained <25 ps resolution for 10 pe’s.
44
Timing vs. Number of PE’s
45
40
Time Resolution (ps)
35
30
HV 2350
25
HV 2450
20
HV 2650
HV 2750
15
HV 2850
10
5
0
0
20
40
60
80
100
120
#PE
No dependence of timing on gain if sufficient amplification!
45
Transit Time Spread for Burle 64
Channel Planacon (10 m pores)
• Jerry Va’vra has measured 32 ps for TTS (SLAC-PUB-13573) so we
should have about 10 ps (32/10 for 10 pe’s! )
• This is true only if you ignore 2nd backscattering peak
January 12, 2010
Andrew Brandt SLAC Seminar
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UTA Transit Time Spread for Burle
64 Channel Planacon (10 m pores)
testing/modelling of response
of PMT to late light and
evolution of timing from
one to several pe’s in progress
Current/area for 10 m Tube
Relative Gain vs. Calculated Output Current
1.2
Relative Gain
1.0
0.8
0.6
0.4
0.2
0.0
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
Calculated Output Current (μA/cm2)
January 12, 2010
Andrew Brandt SLAC Seminar
Last 2 points are
0.4 and 2.0
μA/cm2; we need
to reach about 3
μA/cm2 at 1034
Photonis has
made Planacon
with 10x higher
current
capability which
would meet our
rate requirements
(even with
1.0E+01
saturation we still
obtain the same
48
time resolution!!!)
New Multi-Channel Laser Setup
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Andrew Brandt SLAC Seminar
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Rate Tests
1.20
Normalized Pulse Height
1.00
XoX
0.80
ooX
Xoo
0.60
ooo
0.40
oooooooo
0.20
0.00
1.0E+03
1.0E+04
1.0E+05
1.0E+06
1.0E+07
Laser Frequency (Hz)
No rate dependence on number of pixels hit (that’s a good thing!)
January 12, 2010
Andrew Brandt SLAC Seminar
50
Beam vs Fiber
Fiber
timing
not as good, butAndrew
allows
us SLAC
flexibility
January
12, 2010
Brandt
Seminarfor some characterization
51 tests
SQRT(N)?
From averaging
time of four
measurements
on event-byevent basis
If single fiber gives 35 ps
then 4 fibers should give
17 ps; but note that with
many fibers plugged in,
individual pixel gets light
leaking from neighboring
channel, need to test
that this effect is
reproduced in test beam
52
Components of AFP Fast Timing System
Mini-circuits ZX60
3 GHZ or equivalent
QUARTIC:
Photonis planacon
10 m pore 8x8 or
equivalent Photek
MCP-PMT
Louvain Custom
CFD (LCFD)
HPTDC
board
(Alberta)
Reference
HV/LV
UTA QUARTIC/PMT Development
Timing
Stonybrook
AMP to
HPTDC
Optomodules/
ROD
Ref. time
SLAC
+LLNL
<1 ps !
Manchester/UCL
LCFD
ZX60 3 GHz amplifier
Louvain developed
LCFD (Louvain Constant
Fraction Discriminator)
mini-module approach
tuned LCFD mini-module
to Burle and Hamamatsu rise
times; 12 channel NIM unit
Excellent performance : <10 ps
resolution for 4 or more pe’s
Remote control
for threshold
January 12, 2010
Andrew Brandt SLAC Seminar
54
Alberta HPTDC board
12 ps resolution with
pulser. Successfully tested
at UTA laser test stand
with laser/10 m
tube/ZX60 amp/LCFD
LCFD_Ch01_No12_spe, high level light, May 6, 2009, UTA laser test
RMS resolution = 13.7 ps
6000
5000
counts
4000
3000
2000
1000
January 12, 2010
13.7 ps
with
split
LCFD
signal
0
800
810
820
830
840
850
bin number
860
870
55
880
890
900
Fast Timing Summary
• Have tested detectors and electronics chain
capable of ~10 ps timing
• R&D still in progress to optimize all
components (and reduce rate/pixel)
• Prototype system test beam including readout
planned for this summer
• PMT lifetime is an ongoing issue, but pursuing
options with vendors that seem likely to
provide solutions on 3 year timescale (prior to
max luminosity)
January 12, 2010
Andrew Brandt SLAC Seminar
56
AFP allows ATLAS to cover all
the possibilities!
January 12, 2010
Andrew Brandt SLAC Seminar
57