Summary TG-10
MC & Background
Xiang Liu
for TG-10
Last Collab. Meeting
Joint MC force from Gerda & Majorana.
mjgeometry
Generator, physics
processes, material,
management, etc.
gerdageometry
mjio
gerdaio
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.
Gerda Collab. , Jun 27-29, 2005
Last Collaboration meeting
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
Gerda Collab. , Jun 27-29, 2005
outline
MaGe Ready!
An internal note describing MaGe is ready.
First official version soon, MaGe ready for users.
 MaGe ready to answer questions from other TGs!
Version releasing procedure being established.
Gerda Collab. , Jun 27-29, 2005
1) Further MaGe development
2) Gerda Background & Calibration
Top scintillator veto & water cerenkov veto of cosmic muon
 C. Tomei (LNGS)
Water Cerenkov veto & optimization of PMT
 M. Knapp (Tuebingen), A. Klimenko (Dubna)
muon
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)
radioactive
Ra contamination in water  L. Pandola (LNGS)
Calibration source for Gerda  K. Kroeninger
Gerda Collab. , Jun 27-29, 2005
calibration
2) Gerda Background
Analysis of bkgd contributions
from support structure (Phase-I)
MaGe Geant4 MC: probabilities per decay to deposit energy at Q in
1 keV energy bin
Co-60: 3.1 ·10-5
Bi-214: 1.3 ·10-5
Tl-208: 7.5 ·10-5
Co-60: 1.4 ·10-4
Bi-214: 5.1 ·10-5
Tl-208: 1.4 ·10-4
Co-60: 1.6 ·10-5
Bi-214: 1.2 ·10-5
Tl-208: 5.8 ·10-5
Using our limits for
Cu, PTFE and Si
Rate in roi:
<1.5·10-3 / (keV kg year)
Radioactive bg. (Phase-II)
Source
K. Kroeninger, L. Pandola
Activity
Suppr. Factor
Bkg. 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
15 /kg/year
4.7 ·10-5
0.07
< 26 μBq/kg
1.2 ·10-4
<1
T1/2 = 1.74·1021 y
< 10-6
< 0.45
60Co
(cyrstal)
226Ra
2νββ
(cable)
800 M. Radon in water tank generated, not a issue.
Gerda Collab. , Jun 27-29, 2005
2) Gerda Background – radioactive bg.
Gerda Calibration Source
K. Kroeninger
Source inside container
>1k events in photon peak
in each segment
60Co, 22Na
and 88Y, good candidates
Gerda Collab. , Jun 27-29, 2005
3) Gerda Calibration
Summary 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.
Gerda Collab. , Jun 27-29, 2005
2) Gerda Background & Calibration
3) R&D: H-M crystals & LArGe
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
old
new
ANG1
ANG3
ANG2
C.Tomei
Gerda Collab. , Jun 27-29, 2005
1m
ANG4
new
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:
Gerda Collab. , Jun 27-29, 2005
60Co
and
133Ba
(also
226Ra)
3) R&D
Co60 comparison
General agreement with
measurement.
More to be understood.
Ratio of gamma lines in data  locate bg source positions,
 verified by MC (O. Chkvorets in TG1)
Gerda Collab. , Jun 27-29, 2005
3) R&D
Simulating LArGe
L. Pandola
Simple setup:
tank
Goal: complete simulation
of the scintillation photons
LAr scintillation: large yield (40,000
ph/MeV) but in the UV (128 nm)
PMT
Surface reflection.
Scattering & absorption.
reflector
and WLS
crystal
Gerda Collab. , Jun 27-29, 2005
Crystal shadowing effects.
Properties of WLS.
All depend on wave-lengths!
3) R&D
Optical physics
Geant4 (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
Refraction index of LAr
Properties of all
interfaces (reflectivity,
absorbance)
Absorption length of LAr
• Rayleigh scattering
Rayleigh length of LAr
• wavelenght shifting
Emission spectrum of VM2000
(measured here) and QE
The optical properties of materials and of surfaces (e.g.
refraction index, absorption length) must be implemented 
often unknown (or poorly known) in UV
Gerda Collab. , Jun 27-29, 2005
3) R&D
Output from the simulation
Ar
peak
VM2000
emission
Cerenkov
spectrum
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
Gerda Collab. , Jun 27-29, 2005
3) R&D
LArGe set-up at Gran Sasso
The geometry for the LArGe
set-up at Gran Sasso has
been implemented in MaGe
It includes the shielding
layers, the cryo-liquid and
the Ge crystals
Number of crystals columns and
plans tunable by macro
( interfaced with the general
Gerda geometry tools)
Available in MaGe and
ready for physics studies
MaGe progress:
physics validation
D. Franco
• 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)
MaGe progress:
physics validation
Ra-226 calibration of conventional crystal
Summary on LArGe Simulation
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
Gerda Collab. , Jun 27-29, 2005
3) R&D
4) MaGe verification with SHIELD
SHIELD-HIT(INR RAS,KI,2001)
(Energies at 1 TeV/A are available)
SHIELDHI(INR RAS,1997)
(Interactions of nucleons, Pi, K, anti nucleons,
muons, all (A,Z) nuclei. All isotope and
chemical compounds, complex geometry)
SHIELD(INR RAS,1989)
(Kernel had been totally overwritten.
Growth of functionality)
SHIELD(JINR,1972)
(Nucleons-Pi mesons cascades evolution
up to energy 20 – 30 GeV )
A. Denisov
SHIELD is transparent
Geometry
Low energy neutrons
transportation
Inelastic interactions
Improved CG module
(Combinatorial geometry)
LOENT
(ABBN 28 constants)
MSDM generator
(Multy Stage Dynamical Model.
Exclusive approach. )
MaGe
Energy transfer spectrum from muon to hadron shower
Comparing with Bugaev - Bezrukov
formula
MaGe
SHIELD
Simulation of simple geometry for hadron transportation
Comparing results and analyzing discrepancies
Proposed comparison
5) Pulse shape simulation & analysis
Co60
Kevin Kroeninger
Gerda Collab. , Jun 27-29, 2005
5) Pulse Shape
Pulse shape simulation
How to simulate PS:
Kevin Kroeninger
 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.
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape
Drifting field
• Example: true coaxial n-type detector
Electrons
Holes
Electrons
Local energy
deposition
Gerda Collab. , Jun 27-29, 2005
Holes
5) Pulse shape
Weighting field
• Example: true coaxial detector with 6 φ- and 3 z-segments
z = 2.6 cm
z = 5.1 cm
z = 7.7 cm
IMPORTANT: Particles do not move
due to weighting field
z
y
Gerda Collab. , Jun 27-29, 2005
(Slices in z showing x-y plane)
5) Pulse shape
Pulse Shape simulated
• Full simulation of true coaxial 6-fold segmented detector
electrode
electrode
electrode
Rising time
R
core
Left-right
asymmetry
Charge

electrode
electrode
electrode
Time
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape
Rising time comparison
Risetime [ns]
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape
Pulse Shape analysis “Mexico hat”
• Examples of mexican hat filter for different widths
Distinguish
power to
some extent
Gerda Collab. , Jun 27-29, 2005
5) Pulse shape
Summary on Pulse Shapes “R&D”
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.
Gerda Collab. , Jun 27-29, 2005
All under developing!
5) Pulse shape
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
summary
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
Outlook
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)
Gerda Collab. , Jun 27-29, 2005