claudia höhne - gsi darmstadt, germany cbm collaboration
DESCRIPTION
Concept for a RICH detector for the CBM experiment at the future accelerator facility FAIR at GSI in Darmstadt. Claudia Höhne - GSI Darmstadt, Germany CBM collaboration. Outline. context of the RICH detector CBM @ FAIR CBM physics requirements for RICH detector - PowerPoint PPT PresentationTRANSCRIPT
Concept for a RICH detector for the CBM experiment at the future accelerator facility
FAIR at GSI in Darmstadt
Claudia Höhne - GSI Darmstadt, Germany
CBM collaboration
Claudia Höhne 5th International Workshop on RICH Counters 2004
Outline
• context of the RICH detector
• CBM @ FAIR
• CBM physics
• requirements for RICH detector
• design of RICH detector
• mirrors
• photodetector
• radiator
• simulations
• summary - outlook - future plans
Claudia Höhne 5th International Workshop on RICH Counters 2004
SIS 100 Tm
SIS 300 Tm
U: 35 AGeV
p: 90 GeV
Facility for Antiproton and Ion Research
„next generation“ accelerator facility:
• double-ring synchrotron
• simultanous, high quality, intense primary and secondary beams
• cooler/ storage rings (CR, NESR, HESR)
Ion and Laser induced plasmas: High energy density in matter
Compressed Baryonic Matter
Cooled antiproton beam: hadron spectroscopy
Structure of nuclei far from stability
CBM @ FAIR
Claudia Höhne 5th International Workshop on RICH Counters 2004
nuclei
hadronic phase
SPS
RHIC
lattice QCD : Fodor / Katz, Nucl. Phys. A 715 (2003) 319
SIS300
dilute hadron gasdense baryonic medium
Investigation of the phase diagram of strongly interacting matter
• high T, low B
top SPS, RHIC, LHC
• low T, high B
SIS
• intermediate range ?
low energy runs SPS, AGS
SIS 300 @ GSI !
Critical point?
Deconfinement?
Highest baryon densities
→ in medium properties of hadronsrestoration of chiral symmetry?
CBM physics
Claudia Höhne 5th International Workshop on RICH Counters 2004
CBM experiment
• tracking, vertex reconstruction: radiation hard silicon pixel/strip detectors (STS) in a magnetic dipole field
• electron ID: RICH & TRD (& ECAL) suppression 104
Compressed Baryonic Matter experiment
• hadron ID: TOF (& RICH)
• photons, 0, : ECAL
• high speed DAQ and trigger
Claudia Höhne 5th International Workshop on RICH Counters 2004
RICH detector in CBM
• radiator with high threshold (th > 40) → p,th ~ 5-6 GeV/c, 90% of e reached at 12-13 GeV/c
• sufficient radiator length for generation of Cherenkov photons (N >> 10), small radiation length, good UV transparency of radiator gas
• low material budget (holds for all detector parts) to minimize secondary interactions and in particular e+e- pairs from -conversion
• large, continuous mirror-surface with excellent optical properties
• fast photodetectors (107 Hz) with wide detection range, high qe, high granularity
• precise measurement of e+e- pairs from the decay of mesons within a large acceptance (-suppression ~ 10-4–10-3)
• improve /K separation at higher momenta (kaon ID by TOF quickly deteriorates above 4 GeV/c)
task of RICH detector
detector requirements
Claudia Höhne 5th International Workshop on RICH Counters 2004
RICH design
• 2.2m long gas radiatorgas vessel with beam pipe in the center
• 2 mirror and 2 photo-detector planes (vertically separated)
• mirror: Be+glass, R=450cm2 x (450cm x 175cm)
• photo-detector: PMT planeshielded by magnet yoke2 x (280cm x 140cm)
• support structures preferably from side
Claudia Höhne 5th International Workshop on RICH Counters 2004
RICH mirror (IHEP Protvino, Russia)
beryllium
glass
heater
High temperature (~600C)
• spherical mirror, R=450cm
• Be hexagons (3mm thick, maximum diameter 60cm, 1.3kg) covered with 0.5mm glass→ 1.25% of X0
• glass polishing, Al covering, SiO2 coating → 92% total reflectivity in wide wavelength range
• excellent optics, no degradation and radiator gas pollution due to long exposition in a radiation hard environment expected
production: assembly:
Claudia Höhne 5th International Workshop on RICH Counters 2004
RICH mirror
prototype available:
• optical surface roughness h = 1.6nm (after glass polishing, Al covering and SiO2 coating)→ diffuse reflection of only 12% of total for = 150nm
• image diameter of a point source D0 = 0.4mm (contains 95% of reflected light)
→ angular deviation from nominal curvature = 0.03mrad
Be plate for LHCb Be-mirror prototype
Claudia Höhne 5th International Workshop on RICH Counters 2004
PMTs (IHEP Protvino + Moscow Electrolamp)
PMT FEU-Hive
• K2CsSb photo-cathode, 25% quantum efficiency at = 410nm
• to be covered with transparanet WLF film (p-theraphenyl) → 22% qe for wide range
• ~90% geometrical efficiency
Claudia Höhne 5th International Workshop on RICH Counters 2004
PMT FEU-Hive
• external PMT diameter 6mm photo-cathode diameter 5mm → ~105 channels per detector plane
• length 6cm
• high voltage ~ 2kV
• effective number of dynodes 12
• amplification 106
→ effective operation in one-photoelectron regime
• power dissipation 40mW
• noise current ~ 3000 e-/s
• capacitance 10-15 pF
• dynamical range of signal charge Q = (0.25-25) 106 e-
• average signal time ~ 1ns
Claudia Höhne 5th International Workshop on RICH Counters 2004
radiator
• no window between radiator and photo-detectors: He, N2, CH4
fluorescence? CH4 as quenching gas in mixture?
• th > 40, UV transmittance, radiation length!
• ideal would be an easy handling (gas system)
n th c p,th th X0
He 1.000035 119.5 0.48° 16.7 GeV/c ~ 50nm 5300m
N2 1.000298 41 1.4° 5.72 GeV/c ~ 80nm 304m
CH4 1.000444 33.6 1.7° 4.68 GeV/c 145nm 650m
60%N2 + 40%CH4 1.000356 37.5 1.53° 5.25 GeV/c 145nm 386m
40%He + 60%CH4 1.0002804 42.2 1.36° 5.9 GeV/c 145nm 999m
Claudia Höhne 5th International Workshop on RICH Counters 2004
Simulation (GEANT3)
• CBM detector simulation framework GEANT 3, GEANT 4
• implementation of RICH detector
• Cherenkov properties of materials from HADES, literature
beam
2m3.
3m
4.7m
Gasbox: 250 m aluminum
• study basic properties of current detector concept
• prove feasibility of desired -suppression
• optimize geometrical design, optical layout
Claudia Höhne 5th International Workshop on RICH Counters 2004
rings() - polar angle, azimuth angle
• no diffusion at reflection
• no magnetic field, no multiple scattering
→ eccentricity for large
= 80o 60o 40o
20o
= 5o
10o 15o
20o 25o
30o 35o
one quarter of mirror/ photodetector:
Imaging properties of mirror
optimize optical design of detector!
Claudia Höhne 5th International Workshop on RICH Counters 2004
Single particles
radiator 40%He+60%CH4
• e/ separation (depending on radiator) up to 11-14 GeV/c
• identification from 5-7 GeV/c to 11-14 GeV/c
• diameter of ring 10.6-12 cm ≈ 17-20 PMTs
• wide acceptance covered
single e- acceptance
Claudia Höhne 5th International Workshop on RICH Counters 2004
figure of merit
Cherenkov spectrum for N2
40%He + 60%CH4
min N N0 [cm-1] NPMT
120nm 33 292 25
200nm 23 204 18
250nm 15 138 11
300nm 11 93 8
N= 1.3 NPMT
Importance of continuation of the development of PMTs with large qe in the UV range!
Claudia Höhne 5th International Workshop on RICH Counters 2004
UrQMD event35 AGeV central Au+Au
about 40 rings/event:
• 33 electrons (~13 from primary vertex)
• 7 pions
• 0.1 muons
Claudia Höhne 5th International Workshop on RICH Counters 2004
UrQMD event
35 AGeV central Au+Auz-coordinates of track vertices for particles detected in RICH:
• target (z = 0cm) - 125m Au
• 7 STS – 2x100m, 5x200m Si (z = 5,10,20,40,60,80,100 cm)
• beampipe (z ~ 20-30 cm)
• magnet yoke (z ~110-140 cm)
optimize CBM detector layout to further suppress e+e- pairs from -conversion!
Claudia Höhne 5th International Workshop on RICH Counters 2004
misidentification
first estimation
• assume 100% ring finding, match closest track to a certain ring
• large number of charged tracks per event, additional information available from TRD, TOF
ideal tracking 1% momentum resolution
Claudia Höhne 5th International Workshop on RICH Counters 2004
summary - outlook - future plans
optimize detector layout (optics system!)
continue RICH R&D (radiator, mirror, PMT)
concept of RICH detector for the CBM experiment introduced
2006/2007 RICH prototype 2006/2007
2007/2008 beam tests of RICH prototype 2007/2008
2008/2009 final RICH design
2009/2010 RICH production
- 2012 installation, commissioning, beam!