focussing disc dirc design for panda
DESCRIPTION
Focussing disc DIRC design for PANDA. Klaus F öhl 18 July 2007 LHCb RICH Group meeting at Edinburgh. HESR. Rare-Isotope Beams N-N Collisions at High Energy Ion Beam Induced Plasmas Antiprotons. Nuclei Far From Stability Compressed Nuclear Matter High Energy Density in Bulk - PowerPoint PPT PresentationTRANSCRIPT
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Focussing disc DIRC design for PANDA
Klaus Föhl
18 July 2007
LHCb RICH Group meeting at Edinburgh
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Rare-Isotope BeamsN-N Collisions at High EnergyIon Beam Induced PlasmasAntiprotons
Nuclei Far From StabilityCompressed Nuclear MatterHigh Energy Density in BulkHadron Spectroscopy
HESR
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Core programme of PANDA (1)
• Hadron spectroscopy– Charmonium spectroscopy– Gluonic excitations (hybrids, glueballs)
• Charmed hadrons in nuclear matter
• Double -Hypernuclei
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Core programme of PANDA (2)
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PANDA Side View
Pbar AND A
AntiProton ANihilations at DArmstadt
• High Rates– 107 interaction/s
• Vertexing– KS
0, Y, D, …
• Charged particle ID– e±, μ±, π±, K, p,…
• Magnetic tracking
• EM. Calorimetry– γ,π0,η
• Forward capabilities– leading particles
• Sophisticated Trigger(s)
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PANDA Detector
beam
Top View
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PANDA Detector
beam
Top View
RICH
Barrel-DIRC
Endcap Disc DIRC
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fused silicaradiator
Cherenkov Detectors in PANDA
• HERMES-style RICH
• BaBar-style DIRC
• Disc DIRC4 instead of 2 mirrors
front viewside view
* measurement
* measurement
2-dimensionalimaging type
one
-dim
ens
iona
lim
agin
g D
IRC
typ
e
*
*
*
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Focussing & Chromatic Correction
focussingelement
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Focussing & Chromatic Correction
higherdispersionglass
SiO2 amorphous fused silica
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Focussing & Chromatic Correction
higherdispersionglass
two boundarysurfaces to turncorrection mostlyangle-independent
different curvatures required
curvature iscompromise
internalreflection angleindependent of
light never leaves dense optical medium good for phase space
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Focussing disc DIRCfocal plane of focussing lightguide withrectangular photon detector pixels
foca
l pla
ne c
oord
. [m
m]
lightguide number
lightguide “200mm”
LiF
SiO2
SiO2
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Light Generation
• radiator thickness– number of photons
• transparency– wide wavelength range (eV) – high statistics
• material dispersion– either narrow w. band– or correction required
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Particle Path Stragglingx
( ) x standard deviation of x
angle information of upstream trackingis 0.57 off( ) x
Cherenkov ring
Cherenkov ring image is blurredby 0.38 ( ) x
reduce radiator thickness, reduce X0
2 sigma envelopes
K
fused silica, thickness??
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Light Propagation10 mrad
individual angle variations: = Pixel / sqrt(N)1 mrad
about 50-100 reflections
length 400mm, =400nm d=1mm (approximately)
d
Fresnel Zone
rough surface causing path length differences and phase shifts
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Expansion Volume advantageousperipheral tracks createlocal high photon density
the further outward,the more radial the light paths
increasingparticle angle
rim proximity
performance does drop towards disc perimeter
outer limit ofacceptancecoverage
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Focussing Lightguides
• short focal plane 50mm• ~1mm pixels needed• optical errors exist• thicker plate a problem
• focal plane 100mm• pixel width 2-3mm• benign optics• thicker plate ok
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Light Detection
• detector geometry• magnetic field (~1T)• photon rate (MHz/pixel)• light cumulative dose • radiation dose
photon detection is a problem still to be solved
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Focussing disc DIRC
focussing is better than 1mmover the entire linechosen as focal plane
light stays completelywithin mediumall total reflectioncompact designall solid materialflat focal plane
radiation-hard “glass”RMS surface roughnessat most several Ångström
LiF for dispersion correction
has smaller |dn/d| than SiO2
foca
l pla
ne c
oord
. [m
m]
lightguide number
lightguide “200mm”
rectangularpixel shape
LiF
SiO2
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Momentum Thresholds
fused silica n=1.47
aerogel n=1.05
K
K p
p
total internal reflection limit
n=1.47
K p
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Detector Performance
z_from_target[mm]= 2000disc_radius[mm]= 1100disc_thickness[mm]= 10nzero[1/mm]= 14 (0.4eV)LiF corrector plate
radiation_length[mm]= 126B [Tesla] = 2momentum[GeV/c]= 5beta= 0.98
n_lightguides= 192lightguidewidth= 25lightguidelength= 65 (from apex)lightguide focal plane = [32,80]lightguide pixel size= 1
simulation example with 2 fit analysisshort lightguide 125mm, focal plane 48mm
p2-p1= 4x(1/2 + 2/2)
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In brief
• fused silica radiator disc, around the rim:– LiF plates for dispersion correction– internally reflecting focussing lightguides
• one-dimensional imaging DIRC• radiator with very good RMS roughness required• perfect edges (as in the BaBar DIRC) not needed• number-of-pixels ~ p4
• stringent requirements for photon detectors
• two alternative designs, one DIRC, one RICH• two examples of material testsworking on Cerenkov detectors for PANDA:Edinburgh, GSI, Erlangen, Gießen, Dubna, Jülich, Vienna, Cracow, Glasgow
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Time-of-Propagation designM. Düren, M. Ehrenfried, S. Lu, R. Schmidt, P. Schönmeier
single photonresolution~30-50psneeded
[deg]
t [p
s]
relevant for ToP
idea:reflect somephotonsseveralpath lengths
mirr
ors
reflective hole
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Proximity Focussing design
design variationwith mirror andthe expansionvolume upstreamradiator placed closer to EMC
C6F14CsI + GEM
suggestion Lars Schmitt: combine tracking and PID
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Material Test (1)
Testing transmission and total internal reflectionof a fused silica sample (G. Schepers and C. Schwarz, GSI)
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Material Test (2)
Irradiation test at KVISchott LLF1 HTglass sample
(B. Seitz, M. Hoek, Glasgow)
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Thank you for listening
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Backup Slides
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Particle ID & Kinematicspp KK T=5,10,15 GeV/c
pp DD D K T=6.6 GeV/c
pp i.e. charmonium production
need to measure two quantities:
dE/dxenergymomentumvelocitymomentum (tracking in magnetic field)velocity (Cherenkov Radiation)momentum (tracking in magnetic field)velocity (Cherenkov Radiation)
if mass known, particle identified
K K K
K evenor K
--
--
+ +
+ +
+ +
+ +
+ +
-
- +
+
distinguish and K (K and p) ...
D
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Focussing Lightguides
no LiF plate
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Time-of-Propagation
TOP =30ps N0=344 n0=7.64/mm
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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
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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
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Proximity Focussing
C6F14+
CsI+GEM
radiator 15mmexpansion 135mm[no] mirror
beware: no reality factors included yet