6 June 2002Andrea Bressan University-INFN Trieste1 COMPASS RICH-1 on behalf of the COMPASS RICH Group

6 June 2002 Andrea Bressan University-INFN Trieste 1

COMPASSCOMPASSRICH-1RICH-1

on behalf of theon behalf of theCOMPASS RICH GroupCOMPASS RICH Group


Plan of the talkPlan of the talk

• COMPASS for pedestrians• Rich-1 Parameters• Detector Components

• Radiator• Mirrors• Quartz Windows• Photon-Detectors• Front-End electronics

• Performances in 2001-Run• Conclusions and outlook


COMPASS ProgramCOMPASS Program

Nucleon structure • Gluon polarization

G(x) • Flavour-dependent

helicity functions q(x)• Transverse-spin

distribution functions Tq(x)

• Spin-dependent fragmentation (D

q)

Spectroscopy• Primakov reactions

• Polarizability of and K

• Glueballs and hybrids• Charmed mesons and

baryons• Semileptonic decays• HQET• Observe double-charmed

baryons


G MeasurementsG Measurements

• Single out g fusion graphs– Heavy quark lines (cc)– High transverse momentum

• Experimentally:– DIS + D0 (e.g. via ++K-)– DIS + D* (+D0)– DIS with high Pt hadrons

• Asymmetries measure G– A D AN ~ D Ag G/G

g

N(p)

hadrons

'' kμ

kμ

'kkq

c

c


Polarized beams and polarized nucleon targets

hadron beams (up to 300 GeV energy)

Particle identification

Complex apparatus to allow a wide range of measurements

High-rate capabilities

Large dynamical range (angles and momenta)

COMPASS ExperimentCOMPASS Experiment


2001 Apparatus2001 Apparatus

Spectrometer Magnet 1+tracking

Spectrometer Magnet 2

RICH1

Polarised Target

Calorimetry-1

Calorimetry

Muon Wall

Muon Wall

SPS 160 GeV beam


RICH-1 ParametersRICH-1 Parameters

Main requests from the experiment:1. /K separation up to ~ 60 GeV/c2. Large angular acceptance: 250mrad 200mrad (V)

3. Minimize materials

Design:• Radiator: C4F10, length: ~ 3m• Mirrors:

• Spherical, focal length 3.3 m• Reflectance > 80% for > 165nm• Total surface

• Photon detectors: MWPC’s with CsI photocathodes,out of acceptance / total surface 5.3 m2

• Read-out electronics:• Analog read-out/ 83 K channels• average occupancy 5%• max data rate 2.5 Gb/sec in spill

Material Budget:• Total 22.5% of X0

• Mirrors 5.5%• Radiator 10.5%


Measured ParametersMeasured Parameters

0.0

0.2

0.4

0.6

0.8

1.0

6.0 6.5 7.0 7.5 8.0Photon Energy (eV)

Quartz Transparency

C4F10 Transparency

Mirror Reflectivity

CsI Quantum Efficiency

Single Photon Efficiency

2002) exp. tionthermaliza (gas Deg0.2%1n

Δn FC of T

0.25%1n

ΔnWeight FC

)literature (from 1.2%1n

ΔnDispersion Chromatic

104

104

Contribution to n


VESSELVESSEL

1

10

100

1000

28-Jul-2001 16-Sep-2001 5-Nov-2001 25-Dec-2001

Con

tam

inat

ion

(ppm

)

1

10

100

1000

28-Jul-2001 16-Sep-2001 5-Nov-2001 25-Dec-2001

Conta

min

atio

n (

ppm

)O2 H2O

Excellent Gas Tightness of the Vessel10 ppm Contamination of O2 at 4m3/h 0.2 l/hat 1 mbar overpressure

Flushing the vessel with N2

1

10

100

1000

10000

100000

0 2000 4000 6000 8000

Time (min)

Oxigen Content (ppm)


2001 Mirror Mounting2001 Mirror Mounting

Dedicated talk: S. Costa, ”The mirror system of COMPASS RICH-1”


Mirror Wall-ChecksMirror Wall-Checks

—reflectance of 2 test mirrors measured after 2 year in RICH-1 vessel:

—No degradation above 165 nm

mirror n. 2mirror n. 2

mirror n. 5mirror n. 5

wave lengthwave length

wave lengthwave length

refl

ecti

vity

refl

ecti

vity

refl

ecti

vity

refl

ecti

vity

20002000

20012001

20022002

2000 = immediately after coating2000 = immediately after coating

20020000

2002200220012001


CC44FF1010 Gas RADIATOR Gas RADIATOR

Good Bottle

0.00

0.20

0.40

0.60

0.80

1.00

150 170 190 210 230

Wavelenght (nm)

Tran

smis

sion

(%

)

Starting value

100h cleaning

Bad Bottle

0.00

0.20

0.40

0.60

0.80

1.00

150 170 190 210 230Wavelenght (nm)

Tra

nsm

issi

on (%

)Starting Value

150 h Cleaning

pre-cleaning material loss: ~7%pre-cleaning material loss: ~7%

• C4F10 pre-cleaning (in liquid phase)

and on-line monitoring of VUV light transmission

• measured through 5 cm of liquid (~ 7 m of gas, 1 bar) scaled to 5 m of gas (mean photon path in vessel)

• In 2001 radiator gas was a mixture C4F10 : N2 = 50 : 50

pre-cleaning material loss: up to 50%pre-cleaning material loss: up to 50%

MC) (from0.87 19n

190.5)(N 8 0.5 )FC (design 30

16.5n

γ

2104

γ

Dedicated talk: P. Fauland, ”The radiator gas and the gas system of COMPASS RICH-1”


RADIATOR GAS, 2002 RADIATOR GAS, 2002 MATERIALMATERIAL

• new C4F10 delivery, 570 Kg

• better quality, polluting contamination:

mainly water• new pre-cleaning

installation: cleaning in gas phase 0.00

0.20

0.40

0.60

0.80

1.00

150 170 190 210 230

WaveLength (nm)

tran

smis

sio

n (g

as, 5

m)

15.02.02

01.03.02

05.03.02

08.03.02

raw materialraw material


Photon DetectorsPhoton Detectors

Basic Design from RD26


Quartz WindowQuartz Window

Quartz n.14

0.0

0.2

0.4

0.6

0.8

1.0

160 170 180 190 200

Wavelenght (nm)

Tra

ns

pa

ren

cy

(%

)


Problems with PDsProblems with PDsPDs electrical instability at high beam rate

(6 over 8 PDs operated at 100-150 V lower than the 2100 V nominal HV)

Actions taken:• hunting the technical problem: local wire defects• 4 refurbished wire planes• 2 new wire planes (wire LUMAMETALL OSRAM)

Status: PDs mounted again on RICH-1 vesselwire defect,wire defect,

diameter 20 diameter 20 mmSetup for anode wire Setup for anode wire

alignment and alignment and solderingsoldering

Detected SparkDetected Spark


Photon Detector Photon Detector MountingMounting

CsI Deposit on PCBCsI Deposit on PCB

PCB Transport SystemPCB Transport System

PCB MountingPCB Mounting

Photon Detector MountingPhoton Detector Mounting

Final InstallationFinal Installation


RICH-1 – READ-OUTRICH-1 – READ-OUT

• analogic read-out system, 84,000 channels with local intelligence (DSP, FPGA in FE BORA board) working

• dead time: limited to 500 ns / event up to trigger rates of 75 KHz

• average noise level: ~ 2000 e- , non homogeneous (2001)

• reinforced ground lines (2002), noise level: ~ 1100 e-

Front End BORA boards Front End BORA boards

mounted on photon detectormounted on photon detector

PC resident control PC resident control board DOLINAboard DOLINA

Dedicated talk: M.L. Crespo, ”The COMPASS RICH-1 Read-Out System”


Noise ReductionNoise Reduction

Sigma

Run 2001=2100 e-

Run 2002=1100 e-

Noise sigma for each pad2001 RunThe shape of the PCB supportIs reproduced

Noise sigma for each pad2002 RunThe shape of the PCB supportAbsent


2001 Data Analysis2001 Data Analysis

Abrided from the Dedicated Poster:P. Schiavon et al, ”RICHONE: a software package for the reduction of COMPASS RICH-1 data”


Integrated EVENTSIntegrated EVENTS

Photon detector (Up)

Photon detector (Down)

Beam halo


Reconstructed RINGReconstructed RING

“Ring event”

The cross indicates the track “image ”The blue dots are the padsThe black dots are the selected clusters


Cherenkov ANGLECherenkov ANGLE(a) Cherenkov angle of photons of the Rich(b) Cherenkov angle of the ring for > 60 GeV particles

Superimposed (yellow) out of time signals

11

ringring

all all

photonsphotons

(b)(a)


(a) Cherenkov angle of Reconstructed Ring(b) Number of Photons of the Reconstructed Ring Superimposed (yellow) out of time signals

Number of PhotonsNumber of Photons

photnsphotnsringring

11.7 photons 13.0 photons

all all all all (a) (b)


Conclusions and OutlookConclusions and Outlook2001 Run:

– All important staffs on the floor – 50% of Radiator Gas in – Front End electronics working satisfactory – Noise figure higher than expected – Electrical Instabilities from PDs

2002 Run: New Staffs– Cooling system for the front-end electronics– Fast Radiator Gas mixing in the vessel– Improved noise– Refurbished and rewired PDs– Full radiator GAS

2002 Run: Still Missing Staffs– Vessel thermalisation

Documents

6 June 2002Andrea Bressan University-INFN Trieste1 COMPASS RICH-1 on behalf of the COMPASS RICH Group