An overview of the LHCb RICH detectors

An overview of the LHCb RICH detectors

An overview of the LHCb RICH detectors

RICH 2007Trieste

15-20 Oct 2007

Neville HarnewUniversity of Oxford

On behalf of the LHCb RICH Collaboration

2 RICH 2007 15-20 October, Trieste N. Harnew

Outline of the talk

The LHCb Experiment The RICH status

RICH1 RICH2

The Hybrid Photon Detector (HPD) project RICH2 commissioning RICH calibration Performance Summary


The LHCb Detector

AcceptanceVertical 250mradHorizontal 300mradto 10 mrad

Two RICH detectors provide/K/p identification

Forward spectrometer (running in pp collider mode). A dedicated B-physics experiment at the LHC


LHCb detector in place,commissioning is well underway….

RICH1RICH2


C4F10 gasn=1.0014 Up to ~70 GeV/c

CF4 gasn=1.0005 Beyond ~100 GeV/c

Silica Aerogeln=1.03 1-10 GeV/c

The RICH Radiators

Aerogel C4F10 CF4

5.3 24.0 18.4RICH1:

25250 mrad vertical25 300 mrad horizontal

RICH2: 15100 mrad vertical,

15 120 mrad horizontal

Expected photon yields – for isolated saturated particles


The LHCb RICH Detectors

1m

4m


RICH1 schematic : “vertical” geometry

4m

Upper Magnetic Shielding Protects HPDs from B field, supports upper HPDs

Spherical Mirrors Lightweight carbon fibre mirrors 1.5% radiation length

Glass Planar Mirrors

Beryllium beampipe

(defines RICH1 inner acceptance)

VELO Exit Window 2mm aluminium.. Sealed to gas enclosure. No RICH entrance window.

Photon detector plane 14 by 7 Hybrid Photon Detectors (HPDs)

Quartz Window

Gas Enclosure supports mirrors and aerogel, contains C4F10

RICH1 Exit Window Carbon fibre & PMMI foam

Sealed direct to the beampipe.

Lower Photon detector plane Mounted on lower shield

Lower Magnetic Shielding mounted on cavern floor, supports lower HPDs and Gas Enclosure


RICH1 Magnetic shielding RICH1 picture gallary

Gas Enclosure before installation

Trial installation of the HPD box

Gas enclosure and mirrors installed in LHCb pit

Beryllium beampipe, VELO exit window and seal and planar mirrors


The RICH1 Mirrors

Carbon Fibre Mirrors: 1.5% radiation lengthGlass planar mirrors

Spherical mirrors

See talk by Fabio Metlica


16 aerogel tiles for RICH1. Produced by Boreskov Institute of Catalysis Novisibirsk

200x200x50 mm tiles – the largest ever

n=1.03 ; gives /K separation up to ~10 GeV/c

Exceptional clarity C ~ 0.005 m4cm-1

[I/I0 = A exp –(Ct/4) for thickness t]

Excellent homogeneity (n-1)/(n-1) <1%

Tiles have undergone extensive ageing studies

The RICH1 Aerogel Radiator

Test installation into RICH1

See talk by Tito Bellunato and poster by Davide Perego


RICH2 schematic : “horizontal” geometry

8m

Magnetic Shields protect the HPD planes

Flat Mirrors each made from 20 square glass segments

HPD planes of 9 by 16 HPDs

Gas Enclosure Contains CF4 gas radiator and the optical system

Spherical Mirrors each made from 21 glass hexagonal segments

RICH2 entrance / exit windows carbon fibre and foam sandwich


RICH2 to the pit-Nov 2005 Mirrors aligned to 150

rad before move After move, mirror

movement ~100 rad Stability & alignment

verified. No need to re-align in situ

cf. RICH-2 Cherenkov angle resolution ~ 700 rad


Pixel Hybrid Photon Detectors

Pixel HPDs developed in collaboration

with industry (Photonis-DEP lead

partner)

Combines vacuum technology with

silicon pixel readout ( Quartz window

with S20 photocathode).

484 HPDs occupy a total area of 3.3m2

with 2.5 x 2.5 mm granularity

Factor 5 demagnification @ 20kV.

Operates at the LHC bunch crossing

frequency (40MHz)

Encapsulated 32x32 pixel silicon

sensor Bump-bonded binary readout

chip

200-600 nm wavelength coverage


HPD qualification

Two Photon Detector Test Facilities (PDTFs) have qualified all 550 HPDs produced by Photonis/DEP.

98% of tubes have passed the selection criteria.

Excellent response, QE, dark counts, ion feedback etc.

See talk by Stephan Eisenhardt


The HPD readout chain

All HPDs arranged in columns with ancillary front-end electronics

LV & HV boards power the HPDs

Level-0 boards pass triggered data to the Level-1 off-detector board via an ~100m optical link

Level-1 off-detector receives and zero-suppresses the data and passes to the DAQ

HPD column assembly


RICH2 Commissioning

Laser photon source. Hit

map of 2.4M channels.

RICH2 is complete and

running

10kV applied.

See talk by Carmelo D’Ambrosio

Most of columns have been up to 20kV. Operating RICH2 has now become a routine and safe task.

10 failed HPDs disconnected (out of 288) – these will be replaced The detector control/safety systems (DCS and DSS) are operational RICH2 is ready for global commissioning.


Detector control system in place

HPD boxtemperature

HPD boxhumidity

<- 5 days ->

Cooling pressure over 60 days

Light level

<- 5 days ->

See talk by Mario Sannino

University Genoa


RICH calibration procedures in place

Calibration & alignment systems use projected test patterns: Corrections to HPD

trajectories for magnetic field.

RICH alignment monitoring.

Calibration & alignment also with tracks (data): Alignment with tracks. Refractive index monitoring. Cherenkov angle resolution

from isolated rings. Particle ID calibration with

D*’sSee talk by Antonis Papanestis

Test pattern

with B=0

B=0 and B=30G


RICH performance (testbeam)

Pixel map of a C4F10 ring integrated with ~50k events over 3 HPDs (preliminary)

Performance of the RICH system has been verified in a 80 GeV/c charged particle beam at CERN SPS. C4F10 ~1m radiator length.

Realistic 25 ns beam structure

Final RICH hardware and DAQ

RICH specifications for photon yield and θc resolution have been verified.

C4F10 run

See talk by Sean Brisbane


PID Performance Ring finding

- The algorithm uses tracks, and performs a global likelihood fit to particle hypotheses across both RICH detectors.

– K separation

- Excellent efficiency and low mis-ID rate

See talk by Claus Buszello


Summary and prospects

LHCb RICH has excellent particle ID - crucial for the B physics programme of LHCb

RICH1 installation almost complete

Ready for commissioning at end of year

Innovative carbon fibre mirror and aerogel technology

RICH2 is almost commissioned

Ready for global commissioning

Hybrid Photon Detectors provide excellent single photon sensitivity. Performance is excellent

LHCb expects its first physics data in 2008, with stable running in 2009. We look forward to data-taking with a completed RICH system !


Spare slides


RICH Performance

Aerogel C4F10 CF4

Chromatic 2.4 0.9 0.5

Emission Point

0.4 0.8 0.4

Pixel 0.5 0.5 0.2

Track 0.5 0.5 0.2

Overall 2.5 1.4 0.7

Single Cherenkov photon angle resolution (mrad)

number of photoelectrons

Aerogel C4F10 CF4

5.3 24.0 18.4

Chromatic Uncertainty

The uncertainty due to the dependence of the refractive index on the wavelength of the photon Emission point Error

The uncertainty due to the assumption the photon was emitted at the centre of the track

Pixel Uncertainty

The uncertainty due to the limited resolution of the pixel detectors

Tracking Uncertainty

The uncertainty due to the limited accuracy of the tracking stations

Combining Uncertainty

The CU, EPE and PE are independent but the TU is not and so does not reduce with higher statistics


HPD test results


Magnetic Distortion calibration

B┴

B║

Magnetic fields distort the electron trajectories of the HPDs.

We should expect significant distortions in the LHCb RICHes (max 24 Gauss in RICH1) .

Tubes are individually shielded in mumetal cylinders to mitigate these effects.

Below: RICH2 projection system

Axial Transverse


LHC “approved” schedule - Aug 2007

Documents

An overview of the LHCb RICH detectors