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

2. Introduction Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 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

3. Geometry I Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 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

4. Geometry II Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 Sources consist of small plastic sphere within a steel shield Placed inside lead cylinder with 60° opening Source Lead cylinder

5. Sources Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 List of source used in the simulation: 22 NaT 1/2 = 950.8 dβ + Lines: 511 keV, 1.3 MeV 26 AlT 1/2 = 0.71 MyEC, β + Lines: 511 keV, 1.8 MeV 57 CoT 1/2 = 271 dEC Lines: 122 keV, 136 keV 60 CoT 1/2 = 5.3 yβ - Lines: 1.2 MeV, 1.3 MeV 88 YT 1/2 = 106.65 dβ + Lines: 511 keV, 0.9 MeV, 1.8 MeV

6. Efficiencies Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 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)

7. Activities Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 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 / (T·3600·ε) A : activity in Bq N : number of events T : run duration in h ε : efficiency A = 0.001 / (3.15·10 7 ·r/10) A : activity in Bq r : suppression factor

8. Control Plots Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 Position of hits Source

9. Example: Co-60 Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005

10. Segment Study Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 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 angleAllCentralNeighboring 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 angleAllCentralNeighboring 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

11. Efficiencies and Activities Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 IsotopeT 1/2 Energy [MeV]Efficiency [%]A min [Bq]A max [kBq] 22 Na950.8 d0.511 1.275 0.13 0.05 213.7 555.6 ---- 26 Al0.7 My0.511 1.809 0.30 0.86 92.6 308.6 ---- 57 Co271.8 d0.122 / 0.1360.05555.6- 60 Co5.3 y1.173 1.333 0.13 0.09 213.7 308.6 31.7 88 Y106.7 d0.511 0.898 1.836 0.38 0.18 0.10 73.1 154.3 277.8 31.7

12. Conclusion Kevin Kröninger, MPI München GERDA Collaboration MeetingDUBNA, 06/27 – 06/29/2005 Propose 3 calibration sources with one run of 1 hour per crystal level Simulated 5 different isotopes and calculated limits on the activities 60 Co, 22 Na and 88 Y are good candidates for calibration sources Note GSTR-05-005 is avaiable at MPI-K website