Monte Carlo Studies on

1
Monte Carlo Studies on Possible Calibration
Sources
Kevin Kröninger, MPI für Physik GERDA
Collaboration Meeting, DUBNA, 06/27 06/29/2005
2
Introduction

• External sources in the GERDA setup are needed
  in order
• calibrate the detectors
• Monte Carlo study done with different sources to
  test
• Efficiencies
• Allowed activities (no additional background
  source)
• Homogenity
• Accuracy of calibration

Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
3
Geometry I

• Phase II setup with 3 x 7 crystals and 3 x 6
  fold segmentation
• (378 segments in total)
• Propose 3 sources at marked
• positions and flexible in z
• For MC study only one source
• is simulated

Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
4
Geometry II

• Sources consist of small plastic sphere within a
  steel shield
• Placed inside lead cylinder with 60 opening

Lead cylinder
Source
Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
5
Sources

• List of source used in the simulation
• 22Na T1/2 950.8 d ß Lines 511 keV, 1.3 MeV
• 26Al T1/2 0.71 My EC, ß Lines 511 keV, 1.8
  MeV
• 57Co T1/2 271 d EC Lines 122 keV, 136 keV
• 60Co T1/2 5.3 y ß- Lines 1.2 MeV, 1.3 MeV
• 88Y T1/2 106.65 d ß Lines 511 keV, 0.9 MeV,
• 1.8 MeV

Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
6
Efficiencies

• Total efficiency event efficiency x peak
  efficiency
• Event efficiency is the fraction of events that
  deposits energy
• in at least one segment
• Peak efficiency is calculated for each peak and
  corresponds
• to the fraction of events within a 10 keV
  window around the
• peak (averaged over all segments)

Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
7
Activities

• Demanding an error of 3 1000 events are needed
  in the
• peak region.
• The minimum activity is
• Allowing a background index of 10-3
  cnts/kg/keV/y the
• maximum activity is

A N / (T3600e)
A activity in Bq N number of events T
run duration in h e efficiency
A 0.001 / (3.15107r/10)
A activity in Bq r suppression factor
Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
8
Control Plots

• Position of hits

Source
Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
9
Example Co-60
Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
10
Segment Study

• Calibration should be done homogenious,
  therefore test
• different regions (central, left / right
  neighboring segments)
• Repeat study with 120 opening angle of lead
  cylinder

60 opening angle All Central Neighboring
Avg. peak efficiency Min. peak efficiency Avg. mean value (fit) 0.95 0.04 1173.2 0.2 keV 2.20 0.26 1.70 1173.0 0.1 keV 1.90 0.12 1.70 1173.0 0.1 keV
120 opening angle All Central Neighboring
Avg. peak efficiency Min. peak efficiency Avg. mean value (fit) 0.92 0.03 1172.3 0.4 keV 2.10 0.29 1.50 1173.0 0.1 keV 2.00 0.14 0.91 1173.0 0.1 keV
Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
11
Efficiencies and Activities
Isotope T1/2 Energy MeV Efficiency Amin Bq Amax kBq
22Na 950.8 d 0.511 1.275 0.13 0.05 213.7 555.6 - -
26Al 0.7 My 0.511 1.809 0.30 0.86 92.6 308.6 - -
57Co 271.8 d 0.122 / 0.136 0.05 555.6 -
60Co 5.3 y 1.173 1.333 0.13 0.09 213.7 308.6 31.7 31.7
88Y 106.7 d 0.511 0.898 1.836 0.38 0.18 0.10 73.1 154.3 277.8 31.7 31.7 31.7
Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005
12
Conclusion

• Propose 3 calibration sources with one run of 1
  hour per
• crystal level
• Simulated 5 different isotopes and calculated
  limits on the
• activities
• 60Co, 22Na and 88Y are good candidates for
  calibration sources
• Note GSTR-05-005 is avaiable at MPI-K website

Kevin Kröninger, MPI München GERDA
Collaboration Meeting DUBNA, 06/27 06/29/2005