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Calibration Source Studies for GERDA Detector Using Monte Carlo Simulations

This document outlines the Monte Carlo studies conducted to evaluate potential calibration sources for the GERDA detector setup during the collaboration meeting in Dubna (June 27-29, 2005). It covers various external sources needed for calibration, the efficiency of simulations, and proposes candidates like 60Co, 22Na, and 88Y as viable calibration sources. The study emphasizes achieving accurate and homogeneous calibration across the detector's segments and discusses event and peak efficiencies in detail.

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Calibration Source Studies for GERDA Detector Using Monte Carlo Simulations

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  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 β+ Lines: 511 keV, 1.3 MeV • 26Al T1/2 = 0.71 My EC, β+ Lines: 511 keV, 1.8 MeV • 57Co T1/2 = 271 d EC Lines: 122 keV, 136 keV • 60Co T1/2 = 5.3 y β- Lines: 1.2 MeV, 1.3 MeV • 88Y T1/2 = 106.65 d β+ 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 efficiencyis 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 / (T·3600·ε) A : activity in Bq N : number of events T : run duration in h ε : efficiency A = 0.001 / (3.15·107·r/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 Kevin Kröninger, MPI München GERDA Collaboration Meeting DUBNA, 06/27 – 06/29/2005

  11. Efficiencies and Activities 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

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