Comparison of Endcap CID-PID

Klaus Föhl

PID meeting 27/3/2007

panda-meeting Genova

• Focussing Lightguides

• Time-of-Propagation

• Proximity Focussing

Focussing Lightguides

focalplanecoord.[mm]

lightguide number

Focussing Lightguides

• short focal plane 50mm• ~1mm pixels needed• optical errors exist• thicker plate a problem• 125mm disc-PMT

• focal plane 100mm• pixel width 2-3mm• benign optics• thicker plate ok• 200mm disc-PMT

Focussing Lightguides

no LiF plate

Focussing Lightguides

no LiF plate

LiF plate

performance decreasedue to poor phi resolutionfor particle track near the edge,partial remedy to be investigated

N.B. only rough matching of current geometry

homework: for photon areaof large angle tracksincrease phi resolutionby subdividing pixel length

all calculations: =300nm-600nm Quantum Efficiency 20% n0=15.28/mm

optimisation within the sum rule 6K pixels

Time-of-Propagation

• already investigated– excess radius– pixelisation effectfall-off at larger angle

• to investigate– rectangular hole– different hole coatingsproper ray-tracing– several outer shapes– path ambiguties (with similar travel time)

r=900mm and 1100mm

r=900mm (23deg equivalent) 30ps512 pixels256 pixel128 pixel

notrelevant

notrelevant

Time-of-Propagation

hexagon with rectangular hole

ToP disc Gießen DesignSaclay version:hexagonal shaperectangular black hole

reflective hole absorbing hole

8 degphoton number corresponding to 54 tracks

Time-of-Propagation

TOP =70ps N0=344 n0=17.19/mm[ref: Markus Ehrenfried, Saclay talk]

hexagon with rectangular hole

circle black rectangle

circle mirror rectangle

hexagon mirror rectangle

hexagon black rectangle

circular with rectangular hole

comparison:hexagon 960mm width or round disc 1100mm radius

t=30ps

Time-of-Propagation

• single photo timing crucial

• performance increase comes with more tracks in the time-angle-plane

reflective hole absorbing hole

16 deg

these calculations: =400nm-800nm Quantum Efficiency 30% n0=17.19/mm per band: n(group)=0.0213 (inspired by [480nm-600nm] n=0.00615

Proximity Focussing

design variationwith mirror andthe expansionvolume upstreamradiator placed closer to EMC

Proximity Focussing

C6F14+CsI+GEM

radiator 15mmexpansion 135mm[no] mirror

Proximity Focussing

detection plane needs to be largerthan the radiator size to catch allphotons on the possible cones

ormirrors at the fringesto fold Cherenkov coneback onto the active area

design variationwith mirror andthe expansionvolume upstreamradiator placed closer to EMC

Performance comparison

focussing lightguide

ToP

C6F14+CsI+GEM

radiator 15mmexpansion 135mm[no] mirror

Performance comparison

radiatorX0[]@QEn0 [1/mm]N0

N0*sin^2*geometry

pixels

photon rate..per area..per pixel

Focussing15mm SiO2

12%300nm-600nm@20%15.28225/cos12166

6K

4E9 1/s1.25E6 1/s/cm^20.66E6 1/s/pixel

ToP20mm SiO2

16%400nm-800nm@30%17.19344/cos185100 (75)

1K (?)

6E9 1/s4.5E6 1/s/cm^2 (100%)6E6 (?) 1/s/pixel

Proximity15mm C6F10

7% (+window)

4024-40

3E4 – 1.2E5

2.4E8 1/s~1E4 1/s/cm^2

Cherenkov photons N=d*n0*sinC^2=N0*sinC^2 lightguide PMT 128* 25cm2 2E7 interactions/s ; multiplicity 6 ; Endcap region ~50% in CM 6E7 particles/s

Time-of-Propagation

Proximity Focussing

Proximity Focussing

Proximity Focussing

Photon yield – visible photons

phot

ons p

rodu

ced

in ra

diato

r

plus CsI

quantum efficiency

absorption plusquantum efficiency

20mm

10mm

curves show photon yield for an energy intervalstarting at E_photon=5.4eV

r.home.cern.ch/r/richrd26/www/hmpid/richsim.htmlmaterial properties from RICHSIM web page at CERN

Simulation ingredients

• proper Cherenkov photons number and colour

• refractive index dispersion– Cherenkov angles– Snell's law

• absorption length• quantum efficiency• statistical analysis

• normal incidence particles only maths simplification

• no angular straggling• liquid without vessel• no detector pixels

(assumed to be small)

• Fresnel formula simplified (Brewster angle being close)

• perfect mirror

Simplifications & Approximations

C6F14

CsI mirr

or

Hit pattern

response shape(1000 particles)

photons1 particle=0.99

The particle distance is the average of the photon radial distancesresulting from one charged particle. Particle distance mean and sigmaare computed for samples of 1000 events =1 and 1000 events =0.99and sigma separation & 4-limit derived.

Performance comparison

focussing lightguide

ToP

C6F14+CsI+GEM

radiator 15mmexpansion 135mm[no] mirror

potential edge effects

detection plane needs to be largerthan the radiator size to catch allphotons on the possible cones

ormirrors at the fringesto fold Cherenkov coneback onto the active area

design variationwith mirror andthe expansionvolume upstreamradiator placed closer to EMC

performance – radiator width

angle dependence

preliminary and approximate calculation

source of material properties

• material data used is shown left and below

• from a RICHSIM web page at CERN

r.home.cern.ch/r/richrd26/www/hmpid/richsim.html

material transmission

radiator thickness

Comparison of Endcap PID

Time-of-Propagation

TOP =30ps N0=344 n0=7.64/mm