Detectors for LHC crystal tests

L.Burmistrov, G.Cavoto, F.Iacoangeli, F.Murtas,V.Puill

INFN & LAL Apr 24th 2013

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

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

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!)

Device layoutSee Leonid’s presentation

Geant 4 simulation good to assess the feasibility.Each optical interface need a specific hardware test

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

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)

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

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!)

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)

Effect of radiation on PMT window

From Hamamatsu’s PMT handbook.Glass Window must be absolutely avoided instead.

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 ?

“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

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 ?

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

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

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