summary tg-10 mc & background xiang liu for tg-10
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Summary TG-10MC & Background
Xiang Liufor TG-10
Last Collab. Meeting
Gerda Collab. , Jun 27-29, 2005 Last Collaboration meeting
Joint MC force from Gerda & Majorana.
Generator, physics processes, material, management, etc.
mjgeometry mjio
gerdaiogerdageometry
Detailed simulation of Gerda.
Complete event MC information.
trajectories: all particles in GEANT4 simulation.
hits: energy deposits from particles in sensitive volume.
Radioactive backgrounds, muon veto, neutron.
Outline
Gerda Collab. , Jun 27-29, 2005 outline
Achievement since then:
1) MaGe update
2) Gerda related: Background & Calibration sources
3) R&D related: H-M crystals, LArGe
4) Verification (Comparison) with SHIELD
5) Analysis: Pulse shape simulation & analysis
Summary & Outlook
MaGe Ready!
Gerda Collab. , Jun 27-29, 2005 1) Further MaGe development
An internal note describing MaGe is ready.
First official version soon, MaGe ready for users.
Version releasing procedure being established.
MaGe ready to answer questions from other TGs!
2) Gerda Background & Calibration
Gerda Collab. , Jun 27-29, 2005 2) Gerda Background
Top scintillator veto & water cerenkov veto of cosmic muon C. Tomei (LNGS)
Water Cerenkov veto & optimization of PMT M. Knapp (Tuebingen), A. Klimenko (Dubna)
Cerenkov veto, fine tuning GEANT4 & energy threshold M. Bauer (Tuebingen)
Transportation shielding S. Belogurov
Radioactive bg. (Phase I) S. Schoenert
Radioactive bg. (Phase II) K. Kroeninger (MPI Munich)
Ra contamination in water L. Pandola (LNGS)
Calibration source for Gerda K. Kroeninger
muon
radioactive
calibration
Analysis of bkgd contributions from support structure (Phase-I)
Co-60: 1.4 ·10-4
Bi-214: 5.1 ·10-5
Tl-208: 1.4 ·10-4
Co-60: 3.1 ·10-5
Bi-214: 1.3 ·10-5
Tl-208: 7.5 ·10-5
Co-60: 1.6 ·10-5
Bi-214: 1.2 ·10-5
Tl-208: 5.8 ·10-5
MaGe Geant4 MC: probabilities per decay to deposit energy at Q in 1 keV energy bin
Using our limits for Cu, PTFE and SiRate in roi: <1.5·10-3 / (keV kg year)
Gerda Collab. , Jun 27-29, 2005 2) Gerda Background – radioactive bg.
Radioactive bg. (Phase-II)
Source Activity Suppr. FactorBkg. Index
[10-3 cnts/kg/keV/y]
60Co (holder) ? (0.7 – 2.4)·10-5 ?
208Tl (holder) 9 μBq/kg 1.2 ·10-4 0.3
214Bi (holder) 25 μBq/kg 2.5 ·10-5 0.2
68Ge (crystal) 58 /kg/year 2.2 ·10-4 0.8
208Tl (surface) 80 /surface/year 1.2 ·10-4 0.03
210Pb (surface) 1 μBq/surface 0.6 ·10-5 0.04
60Co (cyrstal) 15 /kg/year 4.7 ·10-5 0.07
226Ra (cable) < 26 μBq/kg 1.2 ·10-4 <1
2νββ T1/2 = 1.74·1021 y < 10-6 < 0.45
K. Kroeninger, L. Pandola
800 M. Radon in water tank generated, not a issue.
Gerda Collab. , Jun 27-29, 2005 3) Gerda Calibration
Gerda Calibration Source
Source inside container
>1k events in photon peak in each segment
K. Kroeninger
60Co, 22Na and 88Y, good candidates
Summary Background & Calibration
Gerda Collab. , Jun 27-29, 2005 2) Gerda Background & Calibration
Top veto & water Cerenkov veto of cosmic muon Phase-I prefers Top veto below penthouse (4.4 10-4 cnts/kg.y.keV) Phase-II Cerenkov veto necessary (<3 10-5)
Cerenkov veto seems efficient, more developement by A. Klimenko, M. Bauer & M. Knapp.
Radioactive background inside crystal, cable & supports Sum: ~2 10-3, dominant: Ge68 & Co60 in crystal, Ra226 in support expect pulse shape to help further Ra contamination in water < 2-3 10-4
Calibration source for Gerda Gerda Note ready.
3) R&D: H-M crystals & LArGe
Gerda Collab. , Jun 27-29, 2005 3) R&D
Simulation of existing Hd-Mo detectors & Comparison with measurement C. Tomei (LNGS), O. Chkvorets (MPI-K)
Simulating LArGe at MPIK & Gran Sasso (optical processes) L. Pandola
Compare LArGe simulation with measurement (see TG1 summary) D. Franco (MPI-K)
Teststands at MPI Munich (see pulse shape) K. Kroeninger
Many data verifications!
Gerda Collab. , Jun 27-29, 2005 3) R&D
Simulating Hd-Mo crystals
Det. 1
0.98 kg
1 m
ANG1 ANG3
ANG4ANG2
oldnew
newC.Tomei
Gerda Collab. , Jun 27-29, 2005 3) R&D
Comparison with data Ba133
Performed by O. Chkvorets and S. Zhukov on February 2005 inside the old LENS barrack first and in LUNA 1 barrack
afterwards.
Detectors shielded with 10 cm lead
Radioactive sources: 60Co and 133Ba (also 226Ra)
Gerda Collab. , Jun 27-29, 2005 3) R&D
Co60 comparison
Ratio of gamma lines in data locate bg source positions,
verified by MC (O. Chkvorets in TG1)
General agreement with measurement.
More to be understood.
Simulating LArGe
Gerda Collab. , Jun 27-29, 2005 3) R&D
Simple setup:Goal: complete
simulation of the scintillation photons
Surface reflection.
Scattering & absorption.
Crystal shadowing effects.
Properties of WLS.
All depend on wave-lengths!
LAr scintillation: large yield (40,000 ph/MeV) but in the UV
(128 nm)
L. Pandola
PMT
crystal
reflector and WLS
tank
Gerda Collab. , Jun 27-29, 2005 3) R&D
Optical physicsGeant4 (and then MaGe) is able to produce & track optical photons (e.g. from scintillation or Cerenkov)
Processes into the game:
• scintillation in LAr
• Cerenkov in LAr
• boundary and surface effects
• absorption in bulk materials
• Rayleigh scattering
• wavelenght shifting
The optical properties of materials and of surfaces (e.g. refraction index, absorption length) must be implemented
often unknown (or poorly known) in UV
Refraction index of LAr
Properties of all interfaces (reflectivity,
absorbance)
Absorption length of LAr
Rayleigh length of LAr
Emission spectrum of VM2000 (measured here) and
QE
Gerda Collab. , Jun 27-29, 2005 3) R&D
Output from the simulation
Frequency spectrum of
photons at the PM (to be
convoluted with QE!)
The ratio between the LAr peak and the optical part depends on the WLS QE: critical parameter
Scintillation yield 40,000 ph/MeV
Ar peak
VM2000 emission
Cerenkov spectrum
LArGe set-up at Gran Sasso
Number of crystals columns and plans tunable by macro
( interfaced with the general Gerda geometry tools)
Available in MaGe and ready for physics
studies
The geometry for the LArGe set-up at Gran Sasso has been implemented in
MaGeIt includes the shielding
layers, the cryo-liquid and the Ge crystals
MaGe progress:
physics validation • 2 data sets from:
– 60Co source + 168 g bare crystal in LN (stat: 5.2e10)
– 226Ra source with a 830 g conventional crystal– 2 positions: in the center (statistics 8.5e7) & 60mm away
(statistics 4.0e8)
• LArGe-MPIK: 60Co, 226Ra, 137Cs
• Three tests:– Comparison of the spectral shapes
– Efficiency (# of events in a gamma peak/disintegration)
– Ratio (# of events in a gamma peak/# of events in the gamma peak of reference)
D. Franco
MaGe progress:physics validation
Ra-226 calibration of conventional crystal
Summary on LArGe Simulation
Gerda Collab. , Jun 27-29, 2005 3) R&D
measurement
simulation
analysis presented in this talk is preliminary
Comparison limited by measurement.
but: we show that LAr suppression works
MaGe reproduces the spectra fairly well
SHIELD(JINR,1972)(Nucleons-Pi mesons cascades evolution
up to energy 20 – 30 GeV )
SHIELD(INR RAS,1989)(Kernel had been totally overwritten.
Growth of functionality)
SHIELDHI(INR RAS,1997)(Interactions of nucleons, Pi, K, anti nucleons,
muons, all (A,Z) nuclei. All isotope and chemical compounds, complex geometry)
SHIELD-HIT(INR RAS,KI,2001)(Energies at 1 TeV/A are available)
4) MaGe verification with SHIELDA. Denisov
Inelastic interactionsMSDM generator
(Multy Stage Dynamical Model.Exclusive approach. )
Low energy neutrons transportation
LOENT (ABBN 28 constants)
GeometryImproved CG module
(Combinatorial geometry)
SHIELD is transparent
MaGe
Energy transfer spectrum from muon to hadron shower
SHIELD
Simulation of simple geometry for hadron transportation
MaGe
Comparing with Bugaev - Bezrukov formula
Comparing results and analyzing discrepancies
Proposed comparison
5) Pulse shape simulation & analysis
Gerda Collab. , Jun 27-29, 2005 5) Pulse Shape
Co60
Kevin Kroeninger
Pulse shape simulation
Gerda Collab. , Jun 27-29, 2005 5) Pulse shape
How to simulate PS:
Calculate electric field E with given boundary & bias voltage.
Calculate “weighting field” for each segment (Ramo’s theory).
Hits from MaGe.
Convert hits into electron-hole pairs (1 pair per 3eV).
electric field Drift path.
weighting field along path Induced charge in each segment.
convolute with pre-amp & DAQ effect.
Kevin Kroeninger
Drifting field
Gerda Collab. , Jun 27-29, 2005 5) Pulse shape
• Example: true coaxial n-type detector
Holes
Electrons
Electrons Holes
Local energydeposition
Weighting field
Gerda Collab. , Jun 27-29, 2005 5) Pulse shape
(Slices in z showing x-y plane)
z = 5.1 cm z = 7.7 cmz = 2.6 cm
y
zIMPORTANT: Particles do not move
due to weighting field
• Example: true coaxial detector with 6 φ- and 3 z-segments
Pulse Shape simulated
Gerda Collab. , Jun 27-29, 2005 5) Pulse shape
• Full simulation of true coaxial 6-fold segmented detector
electrode electrode electrode
electrode electrode electrode
core
Cha
rge
Time
Rising time
R
Left-right asymmetry
Rising time comparison
Gerda Collab. , Jun 27-29, 2005 5) Pulse shape
Risetime [ns]
Pulse Shape analysis “Mexico hat”
Gerda Collab. , Jun 27-29, 2005 5) Pulse shape
• Examples of mexican hat filter for different widths
Distinguish power to some extent
Summary on Pulse Shapes “R&D”
Gerda Collab. , Jun 27-29, 2005 5) Pulse shape
Data-taking:
more ways of taking single- & multi-site events?
PS simulation:
first procedure established, describes reasonably measurement
(general shapes, rising time etc).
PS analysis:
“Mexico hat” proof of principle.All under developing!
Gerda Collab. , Jun 27-29, 2005 summary
Summary of summary
MaGe in good shape.
Background under control, water cerenkov veto ongoing.
Comparison with H-M crystal measurement helps understanding bg.
LArGe simulation improved by measurement.
Verification from other MC packages, FLUKA, SHIELD
Pulse shape simulation & analysis started.
Gerda Collab. , Jun 27-29, 2005 Outlook
Group activity outlook:
LNGS: L. Pandola, C. Tomei.
Cerenkov veto, LArGe scintillation.
MPI-K: D. Franco, M. De Marco
LArGe comparison with data.
Tuebingen: M. Bauer, M. Knapp Dubna: A. Klimenko
Cerenkov veto, neutron bg.
MPI Munich: K. Kroeninger, X. Liu
Pulse shape, radioactive bg.
Moscow: A. Denisov, S. Belogurov
SHIELD improving & cross check MaGe (Geant4)
Your requests, suggestions & contributions are all welcome!
Gerda Collab. , Jun 27-29, 2005
Group Members
L. Pandola (Coordinator), C. Tomei (LNGS)
M. Bauer, M. Knapp (Tuebingen)
D. Franco, M. De Marco (MPI Heidelberg)
K. Kroeninger, X. Liu (MPI Munich)
A. Klimenko (Dubna)
A. Denisov, S. Belogurov (Moscow)