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The DIRC projects of the
PANDA experiment at FAIR
Klaus Föhl on behalf of
RICH2007 Trieste
18 October 2007
Cherenkov Group
Cracow? - Dubna? - Edinburgh - Erlangen - Ferrara - Giessen - Glasgow - GSI - Vienna
HESR
Nuclei Far From Stability
Compressed Nuclear Matter
High Energy Density in Bulk
Antiprotons
Hadron spectroscopy
- Charmonium spectroscopy
- Gluonic excitations (hybrids, glueballs)
Charmed hadrons in nuclear matter
Double -Hypernuclei
include transparency on HESR?
HESR
High Energy Storage Ring
Storage

Np = 5×1010, Pbeam= 1.5-15 GeV/c;
High

luminosity mode:
Δp/p = 10-4, stochastic cooling,
( ≥ 3.8 GeV/c)
L = 1032 cm-2s-1;
High

density target:
pellet 4×1015 atoms/cm2, cluster jet,
wire;
High

ring for p:
precision mode:
Δp/p = 3×10-5, electron cooling,
( ≤ 8.9 GeV/c)
L = 1031 cm-2s-1.
from RESR
Circumference 574 m
A View of PANDA
AntiProton ANnihilations at DArmstadt
A View of PANDA
AntiProton ANnihilations at DArmstadt
•
High Rates
–
•
KS0, Y, D, …
•
e±, μ±, π±, K, p,…
•
γ,π0,η
Forward capabilities
–
Charged particle ID
–
Magnetic tracking
EM. Calorimetry
–
Vertexing
–
•
2 107 interaction/s
•
•
leading particles
Sophisticated Triggers
A View of PANDA
AntiProton ANnihilations at DArmstadt
HERMES-Style RICH
4 instead of 2 mirrors
token figures
DIRC Principles
and lower p threshold solid DIRC
K
p
n=1.47

n photons
text
for 15 deg angle kaons
photons as function of p
20
10
nominal n=1.47 limit
better drawing
0
p [GeV/c]
TOP principles
PANDA Target Spectrometer
Acceptance for
p+p -> ygh @ 15 GeV
Endcap
Barrel
Endcap

hermetic PANDA detector needs
a compact Cherenkov detector
→ DIRC principle
Barrel
Target Spectrometer
two areas – two detector geometries
Barrel-DIRC
Barrel DIRC
2-dimensional
imaging type
Barrel
2D+t or 2+1D design
Barrel DIRC at BaBar/SLAC

already implemented, known to work
17mm
pinhole imaging design
PANDA barrel DIRC
“only” 7000 PMT
(BaBar 11000 PMT)
smaller BaBar version simply works
Simulations
p+p →J/ψ+Φ √s = 4.4 GeV/c2
kaon efficiency 98%
π misidentification as kaon 1-2%
PANDA barrel DIRC
• R&D for smaller photon detector needs optical
elements instead of pinhole focus
– mirrors
focal plane
two lenses for flat focal plane
– lenses
detector
Oil
H2O
air
SiO2
quartz bar
air
mirrors
PANDA barrel DIRC
fused silica
β=0.69c
close to threshold:
small variations in n(λ)
cause large δΘ
internal note:
sin^2 in Frankcos(Θ)=1 / βn(λ) Tamm Formula..
β=0.72c
internal note:
needs time reference
otherwise only realive colour known..
Time of Propagation (TOP) measurement better 0.5ns
allows to correct dispersion
for high and low momenta→x,y,t→3D-DIRC
X
PANDA Target Spectrometer
two different readout designs
Endcap
Endcap Disc DIRC
Time-of-Propagation
1
+
(1+1)D
Focussing Lightguide
2D + t design
concept
Dispersion Corrections
Solution:
ToP
Solution:
Focussing
relevant
for ToP
Time-of-Propagation design
Giessen: M. Düren, M. Ehrenfried, S. Lu, R. Schmidt, P. Schönmeier
mirrors
single photon
resolution
~30-50ps
needed
larger text
idea:
reflect some
photons
several
path lengths
Giessen contrib expected
Time-of-Propagation design
Giessen: M. Düren, M. Ehrenfried, S. Lu, R. Schmidt, P. Schönmeier
larger text
mirrors give
different path lengths
 self timing
single photon
resolution
~30-50ps
needed
small wavelength band
minimises disp effect
+optimised photocathodes
dichroic mirrors allow
multiband – higher photon
statistics within same rad.
Time-of-Propagation
particle angle ???
time resolution
[eV] = QE*wavelengthband
disc with(out) (black) hole
separation def
Focussing Lightguide
radiator
edge
radiator
text
phi*
theta*
photo
sensor
strips
Focussing & Chromatic Correction
varying curvature required
internal
reflection angle
independent of 
imperfect
focussing as
curvature is
compromise
(but good enough)
two boundary surfaces make
chromatic dispersion correction
angle-independent in first order
light never leaves
dense optical medium
 good for phase space
Focal Plane
(dispersive direction)
1-dimensional readout
rough design – alternative with
Focussing Lightguide
simulation example with 2 fit analysis
short lightguide 125mm, focal plane 48mm
p2-p1= 4x(1/2 + 2/2)
to be reworked
Light Propagation
10 mrad
about 50-100 reflections
individual angle variations:  = Pixel / sqrt(N)
1 mrad
d
Fresnel Zone
length 400mm, =400nm  d=1mm (approximately)
rough surface causing path length differences and phase shifts
Polishing Effectiveness
AFM image
Ferrara,
surface from
GW-Glasgow
Testing transmission and total internal reflection
of a fused silica sample
(G. Schepers and C. Schwarz, GSI)
Radiator Tests
AFM image
Ferrara,
surface from
GW-Glasgow
Testing transmission and total internal reflection
of a fused silica sample
(G. Schepers and C. Schwarz, GSI)
Radiation Hardness
10Mrad
100krad
see talk M.Hoek
neutron irradiation also done
Irradiation test at KVI
Schott LLF1 HT
glass sample
U Edin U Glasgow)
Light Detection
•
•
•
•
•
detector geometry
magnetic field (up to 2T)
photon rate (MHz/pixel)
light cumulative dose
radiation dose
see talk A. Lehmann
looking into MCP, silicon PMTs, HPDs  Erlangen, Giessen et al.
Summary
• Ambitious antiproton physics aims require
novel detectors
• PANDA needs DIRCs for PID
• Several designs with innovative solutions
• R&D in progress
Thank you for listening
DIRC
areas
highlighted
alternative slide
Thank you for listening
Backup Slides
Panda Participating Institutes
more than 300 physicists (48 institutes) from 15 countries
U Basel
IHEP Beijing
U Bochum
U Bonn
U & INFN Brescia
U & INFN Catania
U Cracow
GSI Darmstadt
TU Dresden
JINR Dubna (LIT,LPP,VBLHE)
U Edinburgh
U Erlangen
NWU Evanston
U & INFN Ferrara
U Frankfurt
LNF-INFN Frascati
U & INFN Genova
U Glasgow
U Gießen
KVI Groningen
U Helsinki
IKP Jülich I + II
U Katowice
IMP Lanzhou
U Mainz
U & Politecnico & INFN
Milano
U Minsk
TU München
U Münster
BINP Novosibirsk
LAL Orsay
U Pavia
IHEP Protvino
PNPI Gatchina
U of Silesia
U Stockholm
KTH Stockholm
U & INFN Torino
Politechnico di Torino
U Oriente, Torino
U & INFN Trieste
U Tübingen
U & TSL Uppsala
U Valencia
IMEP Vienna
SINS Warsaw
U Warsaw
Particle ID & Kinematics
pp i.e. charmonium production
D+
K - + +
 -  + +
K - K + +
pp  KK
T=5,10,15 GeV/c
 - + K+ even
or K-  - + + +
distinguish  and K (K and p) ...
if mass known, particle identified
need to measure two quantities:
dE/dx
energy
momentum (tracking in magnetic field)
velocity (Cherenkov Radiation)
pp  DD D  K
T=6.6 GeV/c
Time-of-Propagation
these calculations: =400nm-800nm Quantum Efficiency 30% n0=17.19/mm
per band: n(group)=0.0213 (inspired by [480nm-600nm] n=0.00615
reflective hole
absorbing hole
• single photo timing
crucial
• performance
increase comes with
more tracks in the
time-angle-plane
16 deg
Proximity Focussing design
suggestion Lars Schmitt: combine tracking and PID
design variation
with mirror and
the expansion
volume upstream
radiator placed
closer to EMC
C6F14
CsI + GEM
Cherenkov Detectors in PANDA
• HERMES-style RICH
2-dimensional
• BaBar-style DIRC imaging type
• Disc DIRC
* measurement
4 instead of 2 mirrors
one-dimensional
imaging DIRC type
* measurement
*
*
fused silica
radiator
side view
front view
*
Focussing & Chromatic Correction
focussing
element
Focussing & Chromatic Correction
higher
dispersion
glass
SiO2 amorphous fused silica
Focussing & Chromatic Correction
higher
dispersion
glass
internal
reflection angle
independent of 
different curvatures required
two boundary
surfaces to turn
correction mostly
angle-independent
curvature is
compromise
light never leaves
dense optical medium
 good for phase space
Focussing disc DIRC
focal plane of focussing lightguide with
rectangular photon detector pixels
SiO2
SiO2
focal plane coord. [mm]
LiF
lightguide “200mm”
lightguide number
Expansion Volume advantageous
peripheral tracks create
local high photon density
outer limit of
acceptance
coverage
increasing
particle angle
rim proximity
the further outward,
the more radial the light paths
performance does drop towards disc perimeter
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
Focussing disc DIRC
LiF for dispersion correction
has smaller |dn/d| than SiO2
light stays completely
within medium
all total reflection
compact design
all solid material
flat focal plane
radiation-hard “glass”
RMS surface roughness
at most several Ångström
focal plane coord. [mm]
SiO2
focussing is
better than 1mm
over the entire line
chosen as focal plane
rectangular
pixel shape
lightguide “200mm”
lightguide number
Detector Performance
simulation example with 2 fit analysis
short lightguide 125mm, focal plane 48mm
p2-p1= 4x(1/2 + 2/2)
z_from_target[mm]= 2000
disc_radius[mm]= 1100
disc_thickness[mm]= 10
nzero[1/mm]= 14 (0.4eV)
LiF corrector plate
radiation_length[mm]= 126
B [Tesla] = 2
momentum[GeV/c]= 5
beta= 0.98
n_lightguides= 192
lightguidewidth= 25
lightguidelength= 65 (from apex)
lightguide focal plane = [32,80]
lightguide pixel size= 1
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 tests
working on Cerenkov detectors for PANDA:
Edinburgh, GSI, Erlangen, Gießen, Dubna, Jülich, Vienna, Cracow, Glasgow
Time-of-Propagation design
M. Düren, M. Ehrenfried, S. Lu, R. Schmidt, P. Schönmeier
relevant
for ToP
idea:
reflect some
photons
several
path lengths
t [ps]
mirrors
single photon
resolution
~30-50ps
needed
reflective hole
 [deg]
Focussing Lightguides
no LiF plate
Time-of-Propagation
TOP =30ps N0=344 n0=7.64/mm
Time-of-Propagation
comparison:
hexagon 960mm width or round disc 1100mm radius
TOP =70ps N0=344 n0=17.19/mm
[ref: Markus Ehrenfried, Saclay talk]
hexagon with rectangular hole
t=30ps
hexagon mirror rectangle
circle mirror rectangle
hexagon black rectangle
circle black rectangle
circular with rectangular hole
Proximity Focussing
C6F14+
CsI+GEM
radiator 15mm
expansion 135mm
[no] mirror
beware: no reality factors included yet
Focussing disc DIRC design
for PANDA
Klaus Föhl
18 July 2007
LHCb RICH Group meeting at Edinburgh
Core programme of PANDA (1)
• Hadron spectroscopy
– Charmonium spectroscopy
– Gluonic excitations (hybrids, glueballs)
• Charmed hadrons in nuclear matter
• Double -Hypernuclei
Core programme of PANDA (2)
PANDA Side View
• High Rates
–
•
Vertexing
–
•
•
γ,π0,η
Forward capabilities
–
•
e±, μ±, π±, K, p,…
Magnetic tracking
EM. Calorimetry
–
Pbar AND A
AntiProton ANihilations at DArmstadt
KS0, Y, D, …
Charged particle ID
–
•
•
107 interaction/s
leading particles
Sophisticated Trigger(s)
PANDA Detector
Barrel-DIRC
beam
2-dimensional
imaging type
Top View
Gliederung
• quick FAIR & PANDA overview
• DIRC detectors
– Barrel
– Disc Focussing
– Disc Time-of-Propagation
• Challenges
• Summary
• Gesellschaft für
Schwerionenforschung
in Darmstadt, Germany
• German National Lab for
Heavy Ion Research
• Highlights:
– Heavy ion physics
(i.e.tsuperheavies)
– Nuclear physics
– Atomic and plasma physics
– Cancer research
PANDA Detector
beam
Top View
PANDA Detector
Barrel-DIRC
RICH
beam
Endcap Disc DIRC
Top View
PANDA Detector
Top View
RICH
beam
HERMES-Style RICH
Endcap Disc DIRC
4 instead of 2 mirrors
Acceptance for
p+p -> ygh @ 15 GeV
PANDA detector

hermetic PANDA detector needs
a compact Cherenkov detector
→ DIRC principle
calorimeter:
expensive material
Barrel DIRC
C. Schwarz et al.
2-dimensional
imaging type
plate instead of bar?
ongoing work for a more compact readout
PANDA Detector
Top View
2-dimensional
imaging type
Barrel-DIRC
following the BaBar design
beam
Barrel a la Babar
imaging by expansion volume, pinhole “focussing”
PANDA Detector
Top View
beam
Endcap Disc DIRC
Time-of-Propagation
Focussing Lightguide
backup slide
Time-of-Propagation design
M. Düren, M. Ehrenfried, S. Lu, R. Schmidt, P. Schönmeier
relevant
for ToP
idea:
reflect some
photons
several
path lengths
t [ps]
mirrors
single photon
resolution
~30-50ps
needed
reflective hole
 [deg]
Focussing & Chromatic Correction
SiO2 amorphous fused silica
focussing
element
different
dispersion
backup slide
Focussing & Chromatic Correction
higher
dispersion
glass
SiO2 amorphous fused silica
Analysis without external timing
Focussing Lightguide
simulation example with 2 fit analysis
short lightguide 125mm, focal plane 48mm
p2-p1= 4x(1/2 + 2/2)
backup slide
simulation example with 2 fit analysis
short lightguide 125mm, focal plane 48mm
p2-p1= 4x(1/2 + 2/2)
z_from_target[mm]= 2000
disc_radius[mm]= 1100
disc_thickness[mm]= 10
nzero[1/mm]= 14 (0.4eV)
LiF corrector plate
radiation_length[mm]= 126
B [Tesla] = 2
momentum[GeV/c]= 5
beta= 0.98
n_lightguides= 192
lightguidewidth= 25
lightguidelength= 65 (from apex)
lightguide focal plane = [32,80]
lightguide pixel size[mm]= 1
Challenges and Compromises
•
•
•
•
Radiator bulk and surface properties
Radiator thickness
Straggling
Radiation hardness
Light Generation
• radiator thickness
– number of photons
• transparency
– wide wavelength range (eV) – high statistics
• material dispersion
– either narrow w. band
– or correction required
Particle Path Straggling
x
2 sigma envelopes

(x ) standard deviation of  x

K
fused silica, thickness??
Cherenkov ring
angle information of upstream tracking
is 0.57 ( x ) off
Cherenkov ring image is blurred
by 0.38 (x )
 reduce radiator thickness, reduce X0
Material choice for dispersion corr.
LiF sample photo
Irradiation test at KVI
Schott LLF1 HT
glass sample
(B. Seitz, M. Hoek, Glasgow)
Advantages
• wide dynamic range (0.6GeV/c-~6GeV/c)
Momentum Thresholds
p
K

K
K

aerogel n=1.05
p
total internal reflection limit

fused silica n=1.47

p
n=1.47
Thank you for listening