andrew brandtsept 13 th 2005fp420/cerenkov intro 1 location of lhc in france and switzerland, with...

1Andrew Brandt Sept 13th 2005FP420/Cerenkov Intro

FP420/Cerenkov Intro

Location of LHC in France and Switzerland, with lake Geneva and the Alps in the background

The ATLAS detector is currently being built at UTA and at 100's of other institutions all over the world

Proton-proton collisions at 14 TeV


FP420 = Forward Protons 420m downstream of CMS & ATLASPhysics is p H/WW/ZZ pMeasure p’s with very high precision within 3 mm of beammass and quantum numbers of central state.We are talking ~ 5 microns on track over 10m, and 10 ps timing

Challenges include (detectors ~ 6mm x 24 mm): Tracker, perhaps 10 layers per station, 3 stations, 3D silicon(edgeless, 10um res., fast, rad hard) .... Hawaii/SLAC + BrunelTOF counter, quartz fiber Cerenkov + MCP-PMTs

Vacuum mechanics: Detectors in secondary vacuum, Space constraints (Cryo talk), between beam pipes, not roman pots (Micro talk) High precision movement (microns), reproducibility, fail-safe.


We have LOI to LHCC for R&D project (combined CMS/TOTEM & ATLAS)Unofficially (so far) supportivePlan: R&D now summer/fall 2006. Make choices among options, design arms.Go to CMS & ATLAS to propose that it be an upgrade (not separate project)Hope for installation late 2008/2009

Proposed (Fermilab) test beam scenario:Integrate with the BTeV/CMS tracker in place, with its readout etcMount each (of 2) prototype vacuum chambers, with (rough) vacuum, motionsMicrostation (Helsinki) and Hamburg Pipe (Louvain)with a BTeV/cms tracker layer installed and R/O ... tests motion, reproducibiltyand find problems to solve with mechanics, vacuum etc.

Hopefully will also have some 3D Si detectors to put in beam (with BTeV R/O)

(More) hopefully could have 2 S-TOF counters to test with MCP-PMT R/O


Fermilab Test Beam ... Erik Ramberg in charge

Up to 120 GeV protonsUp to 200K/spill (more than enough!) over ~ 5 mm x 5 mm

Beam diagnostics: 3 MWPC profile monitors 4 layers x-y Silicon strip detectors

BEAMMT6-B ... another area behind

http://www-ppd.fnal.gov/MTBF-w/

BTeV pixel & CMS pixelcurrent users of area A


Some views of present A1 set-up (Sep 8 2005)

Side view, beam from L

2 views of exit


Fast Timing Counters

Counters with ~ 10 ps timing resolution behind tracking 10 ps = 3 mm

1) Check both p’s from same collision (reduce background)2) Get z(vertex) to match with central track vertex3) Tell what part of bunches interacting protons were (F-M-B)

Likely solution:Solid Cerenkov block or fibers (quartz?)MCP-PMT (Micro-Channel Plate PMT) ... or APD?(Cerenkov talk)

Mike A + Jim Pinfold + others interested


Photomultiplier Tube (PMT)

• PMTs consist of a photocathode and a series of dynodes in an evacuated glass enclosure. Photons that strikes the photoemissive cathode emits electrons due to the photoelectric effect. The electrons are accelerated towards a series of additional electrodes called dynodes. These electrodes are each maintained at a more positive potential. Additional electrons are generated at each dynode. This cascading effect creates 105 to 107 electrons for each photon hitting the first cathode depending on the number of dynodes and the accelerating voltage. This amplified signal is finally collected at the anode where it can be measured.


Put at back of 420m (220m?) tracking high precision timing counters.Suggested in Tevatron LOI: Quartz Cerenkov + ~ Microchannel PMTThen said 30 ps(?). Now tested (Japanese Gp) 10 ps

Check that p’s came from same interaction vertex (& as central tracks)

tL tRx

tL

tR

z_vtx

z

t

Know position in eachbunch of interacting p’s.Position-momentum correlation Reduce uncertainty inincoming momenta.

t_int

Potentially valuable e.g. MSSM triplet(Higher cross section & close states)


It’s been done!


Challenging, needs study: (1) 3D ray tracing program, with timesDesign a practical compact detector. Beam test.… great project for interested-in-instrumentation student/postdoc

Geometry?Want max lightin delta-function

ug students at UTAYushu Yao (Alberta) CUT AWAY

Plates or FibersRectangular BlockTilted

oCerenk Cerenk

oi i

For quartz n(λ) ~ 1.54

1 1cos(θ ) = = 0.65; θ =49.5

βn n

1For TIR sin(θ ) = = 0.65; θ = 40.5

n

Can’t putMAPMT in front of 7 TeVprotons!


Cerenkov Project Steps

• Reading, understanding concepts, etc.

• 2-d ray tracing program to determine time distribution of light arrival

• 3-d version

• In parallel: calculate number of pe’s

• Build prototype (budget? readout?)

• Test in testbeam

andrew brandtsept 13 th 2005fp420/cerenkov intro 1 location of lhc in france and switzerland, with...

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