Detectors for LHC crystal tests
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![Page 1: Detectors for LHC crystal tests](https://reader035.fdocuments.us/reader035/viewer/2022062720/56813518550346895d9c6e22/html5/thumbnails/1.jpg)
Detectors for LHC crystal tests
L.Burmistrov, G.Cavoto, F.Iacoangeli, F.Murtas,V.Puill
INFN & LAL Apr 24th 2013
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Summary
• LHC BLM– Ionization chamber, they come “for free” anytime
you install a new object on the accelerator.
• Detector for channeled beam in vacuum– Cherenkov light based detector
• Diamond BLM
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Concept• Use a well polished quartz Cherenkov radiator to intercept channeled beam
– 1 cm thick • BTF measurements:
– Cherenkov light in 0.5 mm quartz fiber:» 0.3 pe/0.3mm/mip with SiPM (40% QE) -> 10 pe/mip» Validation of Leonid’s G4 simulation!
• 100 particles channeled/bunch -> percent level measurement!– See Leonid’s presentation
• Quartz bar in vacuum– Need to design vacuum-air interface to bring light outside
• Attach silica fibers (in air) to the quartz bar– Bring light far away from beam pipe (few m) to a PMT– Bring PMT signal very far (hundred m) to electronics
• Motorization and beam pipe insert similar to goniometer – Retractable finger
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Orientation
Relative angle particle-fiber axis
Nov 12 BTF measurements:
LEONI FiberTechALL SILICAAS 400/440 UVPI external diameter : 0.465 mmcore diameter : 0.400 mmCladding Diameter : 0.440 mmCladding doping: FlourineCoating Material : polyamideNA = 0.22attenuation: 0.008dB/m
46 deg should be optimal to collect “direct” light
Overall difference due to SiPM – fiber optical coupling
Might we need a rotation stage to orient the bar ? (it could be good in case of high Z ions!)
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Device layoutSee Leonid’s presentation
Geant 4 simulation good to assess the feasibility.Each optical interface need a specific hardware test
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Vacuum-air interface
quartz
Sketching quartz support and flange
To be inserted in a mechanicalsystem similar to piezo-gonio.
Realizing in a single piece-Fiber bundle-Fiber bundle +viewport-Fiber bundle + viewport +finger[LEONI]
viewport
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Detector location A.Lechner slidesDec 2012
Max Dose (close to pipe)100 kGy/year 1014 neutron/cm2/year (thermal neutron)
Moving detector (PMT) to a far location (on the ceiling?)Readout electronics can be hundred meters away (need coaxial cables for signal and HV supply)
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Readout sketch
COAXIAL cable
Metal dynode or Multi-ChannelPlate [expensive but <100 ps resolution! ]20% QE in blu-UV regionRequire quartz window (to be transparent to blue)
See Veronique’s slides
Photodetector: PMT
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Rad hard silica optical fiberALL SILICAAS600/660UVST tr Core 600μm ± 2%Cladding 660mm ± 2%ACRYLATE Coating 770μm ± 3%Buffer 920μm ± 5%
Attenuation @350nm <=0,06dB/m
Operational in 200-1200 nm range
18 rad/s (0.3 rad/s LHC worst)
NB: Silica quartz fiber have good attenuation in blu-UV but expensive (10 eur/m!)
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Radiation resistance of PMT
– Metal dynode PMT: rad hard – Quartz window OK• Same for the radiator ?
– A custom HV partitor system should be done • Redo standard Hamamatsu with rad hard passive
components
Need PMT irradiation test (proton at PSI)
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Effect of radiation on PMT window
From Hamamatsu’s PMT handbook.Glass Window must be absolutely avoided instead.
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Background/noise • Scattered particles hitting the radiator
– Produce Cherenkov light too– Use two “veto” radiator (subtract light seen there) : – need (at least) three identical channel
• em. noise induce by beam ?
• Is synchronization with machine available ? Is RF signal available at the electronics location ?
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“On board” calibration tools
– LED light• Measures the
stability of the gain
• Inject light into the bar – use one special optical fiber– Does not depend on the stability of the LED!!!
– Inject light at two point of the bar • Measure attenuation length variation of the bar
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Crucial tests
– Optical interface are critical to preserve the Cherenkov photons• Need dedicated hardware test ! Simulation cannot be
trusted…
– Such device require an accurate validation at • BTF (beam of bunched electron – 500 MeV)
– Can simulate the arrival of 1-10-1000 mip within 2ns.– Absolute calibration possible with mips
• SPS – Test the full device is SPS with circulating beam– Is this compatible with LHC schedule ?
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Diamonds• Observe fast losses close to crystal– Need fast electronics
• Reuse some R&D done for GEM
– Install on the exterior of the goniometer device– It might be useful to follow fine crystal movements
• Reuse diamond detector used in UA9
Test at BTF in June
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Cabling…
• Two Cherenkov devices – (3HV + 3 signal)x2 coaxial cables.– 1 (or 2) cables for LED PS• Low attenuation coaxial cables• They should run from the detector location to some
UJxx area
• 4 diamond sensors– 1+1 * 4 coaxial cables
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Comments
• Need a final decision on crystal and detector (absorber) location
• Crucial tests for Cherenkov– Choice of PMT/ irradiation test– Design of interfaces and test– Calibration with extracted beam