MEASUREMENTS OF THE FIRST RF PROTOTYPE OF THE SPIRAL2 SINGLE BUNCH SELECTOR
Setup & tests of prototype bars
1
Scan ~100 bar entry positions with laser • diode measures transmitted intensity (relative to reference intensity) • determine attenuation length (Λ) by aiming laser down length of bar (correct for Fresnel) • determine reflection coefficient (R) by bouncing laser off bar surfaces for 80 cm long bar 31 internal reflections for bar faces, 15 for sides • calculate R from mean transmitted intensity (T) at the Brewster angle • calculate surface roughness (σ) using scalar theory of scattering S e t u p & t e s t s o f p r o t o t y p e b a r s PANDA Barrel DIRC PANDA Barrel DIRC Optical Properties of Bars for the PANDA Barrel Optical Properties of Bars for the PANDA Barrel DIRC DIRC Grzegorz Kalicy GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany Roland Hohler, Dorothee Lehmann, Klaus Peters, Georg Schepers, Carsten Schwarz, Jochen Schwiening DIRC D I R C T h e P A N D A E x p e r i m e n t a t F A I R The PANDA Experiment at FAIR PANDA Barrel DIRC designed as a Fast Focusing DIRC. Basic approach similar to BABAR-DIRC. Important improvements: • Focusing optics remove size of bar from Cherenkov angle resolution term. • Faster timing (100 ps or better) allows partial correction of chromatic effects. • Compact multi-pixel photon detectors allow smaller expansion region. Surface Roughness Surface Roughness DIRC Principle DIRC Principle DIRC: Detection of Internally Reflected Cherenkov light A charged particle traversing a radiator with refractive index n() with v/c > 1/n() emits Cherenkov photons on a cone with half opening angle If n > 2 some photons are always totally internally reflected for 1 tracks. Radiator and light guide: Long, rectangular Synthetic Fused Silica bars. Photons exit via focusing lens into expansion region. Imaging on MCP-PMT array DIRC is intrinsically a 3-D device, measuring: x, y and time of Cherenkov photons, defining c c t propagation of photon. K 53.28, DPG Spring Meeting, Mainz, May 2012 [email protected] Work supported by EU FP6 grant, contract number 515873, DIRACsecondary-Beams, and EU FP7 grant, contract number 227431, HadronPhysics2, and the Helmholtz Graduate School for Hadron and Ion Research HGS-HIRe. Setup & tests of prototype bars Bar with 532nm laser beam Example: scan of bar sides at 532nm Attenuation length Λ = (385 ± 204) m N = 15 reflections T = 0.9914 ± 0.0019a R = 0.99961 ± 0.00016 Surface roughness: σ = (15 ± 3) Å (all errors dominated by systematics) Detector Surface Fused Silica Radiator Particle Track Cherenkov Photon Trajectories Focusing Optics PANDA: antiProton ANnihilation at DArmstadt PANDA Barrel DIRC DESIGN P A N D A B a r r e l D I R C D E S I G N Measured coefficient of total internal reflection for prototype bar for three wavelengths compared to expectation from scalar theory of scattering Radiator bars Photon detectors and electronics Map of transmitted intensity T Number of reflections for track perpendicular to the bar Bar with 532 nm laser beam Motion - Controlled Setup Motion - Controlled Setup Measurements of coefficient of total internal reflection (R) and bulk attenuation (Λ) of radiator bars at multiple laser wavelengths → determine quality of surface finish with few Å accuracy. Radiator bars Photon detectors and electronics Bar boxes Geant Cherenkov photon tracking in event display • More than 200 internal reflections possible before photon will exit the bar. • To transport 90% of internally reflected photons down the bar reflectivity at the level of 0.9995 is needed. Cherenkov photons Particle track Particle identification (PID) for PANDA will be performed by several specialized detectors. For target spectrometer: • Barrel DIRC (3σ π/K separation for momentum range 0.5 - 3.5 GeV/c) • Endcap Disk DIRC • Time-of-Flight system • dE/dx of tracking system Momentum distribution in barrel region is an excellent match to DIRC range. Endcap Disk DIRC (5 o – 22 o ) Barrel DIRC (22 o –140 o ) Next steps: • Expand wavelength range using a UV laser (266 nm). • Measure prototype bars from additional vendors. • Qualify the production and polishing processes of the different bar manufacturers. Mirror PID for PANDA PID for PANDA AT AT FAIR FAIR Expansion volume Wavelength [nm] Reflection Coefficient Number of internal reflections Counts
description
p. Optical Properties of Bars for the PANDA Barrel DIRC. Particle Track. Focusing Optics. Fused Silica Radiator. Grzegorz Kalicy GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany - PowerPoint PPT Presentation
Transcript of Setup & tests of prototype bars
Scan ~100 bar entry positions with laser
• diode measures transmitted intensity (relative to reference intensity)
• determine attenuation length (Λ) by aiming laser down length of bar (correct for Fresnel)
• determine reflection coefficient (R) by bouncing laser off bar surfaces
for 80 cm long bar 31 internal reflections for bar faces, 15 for sides
• calculate R from mean transmitted intensity (T) at the Brewster angle
• calculate surface roughness (σ) using
scalar theory of scattering
Setu
p &
tests
of p
roto
typ
e b
ars
PANDA Barrel DIRCPANDA Barrel DIRC
Optical Properties of Bars for the PANDA Barrel DIRCOptical Properties of Bars for the PANDA Barrel DIRCOptical Properties of Bars for the PANDA Barrel DIRCOptical Properties of Bars for the PANDA Barrel DIRCGrzegorz Kalicy
GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany
Roland Hohler, Dorothee Lehmann, Klaus Peters, Georg Schepers, Carsten Schwarz, Jochen Schwiening
DIR
C
DIR
C
Th
e P
AN
DA
Exp
erim
en
t at F
AIR
Th
e P
AN
DA
Exp
eri
men
t at
FA
IR
PANDA Barrel DIRC designed as a Fast Focusing DIRC.
Basic approach similar to BABAR-DIRC.
Important improvements:
• Focusing optics remove size of bar from Cherenkov angle resolution term.
• Faster timing (100 ps or better) allows partial correction of chromatic effects.
• Compact multi-pixel photon detectors allow smaller expansion region.
Surface RoughnessSurface Roughness
DIRC PrincipleDIRC Principle
DIRC:
Detection of Internally Reflected Cherenkov light
A charged particle traversing a radiator with refractive index n() with v/c> 1/n()
emits Cherenkov photons on a cone with half opening angle
If n > 2 some photons are always totally internally reflected for 1 tracks.
Radiator and light guide: Long, rectangular Synthetic Fused Silica bars.
Photons exit via focusing lens into expansion region.
Imaging on MCP-PMT array
DIRC is intrinsically a 3-D device, measuring: x, y and time
of Cherenkov photons, defining cc tpropagation of photon.
HK 53.28, DPG Spring Meeting, Mainz, May [email protected] Work supported by EU FP6 grant, contract number 515873, DIRACsecondary-Beams, and EU FP7 grant, contract number 227431, HadronPhysics2, and the
Helmholtz Graduate School for Hadron and Ion Research HGS-HIRe.
Setu
p &
tests
of
pro
toty
pe b
ars
Bar with 532nm laser beam
Example: scan of bar sides at 532nm
Attenuation length Λ = (385 ± 204) m
N = 15 reflections
T = 0.9914 ± 0.0019a
R = 0.99961 ± 0.00016
Surface roughness: σ = (15 ± 3) Å
(all errors dominated by systematics)
DetectorSurface
Fused SilicaRadiator
ParticleTrack
Cherenkov Photon Trajectories
FocusingOptics
PANDA:
antiProton ANnihilation at DArmstadt
PA
ND
A B
arr
el D
IRC
DES
IGN
PA
ND
A B
arre
l DIR
C D
ES
IGN
Measured coefficient of total internal reflection for prototype bar for three wavelengths
compared to expectation from scalar theory of scattering
Radiator bars
Photon detectors and electronics
Map of transmitted intensity T
Number of reflections for track perpendicular to the bar
Bar with 532 nm laser beam
Motion - Controlled SetupMotion - Controlled Setup
Measurements of coefficient of total internal reflection (R) and bulk attenuation (Λ) of radiator bars
at multiple laser wavelengths
→ determine quality of surface finish with few Å accuracy.
Radiator bars
Photon detectors and electronics
Bar boxes
Geant Cherenkov photon tracking in event display
• More than 200 internal reflections possible before photon will exit the bar.
• To transport 90% of internally reflected photons down the bar reflectivity at the level of 0.9995 is needed.
Cherenkov photons
Particle track
Particle identification (PID) for PANDA will be performed by several specialized
detectors.
For target spectrometer:
• Barrel DIRC (3σ π/K separation for momentum range 0.5 - 3.5 GeV/c)
• Endcap Disk DIRC
• Time-of-Flight system
• dE/dx of tracking system
Momentum distribution in barrel region is an excellent match to DIRC range. Endcap Disk DIRC (5o – 22o)
Barrel DIRC(22o –140o)
Next steps:
• Expand wavelength range using a UV laser (266 nm).
• Measure prototype bars from additional vendors.
• Qualify the production and polishing processes of the different bar manufacturers.
Mirror
PID for PANDA PID for PANDA AT AT FAIR FAIR
Expansion volume
Wavelength [nm]
Ref
lect
ion
Co
effi
cien
t
Number of internal reflections
Co
un
ts
