1. GSEM project SPENVIS/GEANT4 Workshop, Leuven, Belgium, 3 - 7 October 2005 Daniel Haas, DPNC Genève Outline Description of GSEM HEP Range Telescope Radiation in Space GEANT4 Simulation Outlook & Conclusions

2. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 2 The GSEM project… General Space Environment Monitor: Multi-Purpose Detector to monitor critical environmental data, like: Radiation (High Energy Particle Sensor) Vibration Debris Plasma/Discharge

3. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 3 …The GSEM project… ESA/ESTEC contract 10619/04 Collaborators: Contraves Space, Zürich (SREM) Vibrometer, Fribourg DPNC, Université de Genève Prof. Martin Pohl, Prof. Divic Rapin, Dr. Daniel Haas, Denis Rosset Phase A finished Phase B ongoing

4. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 4 …The GSEM project Key Issues: Very light: Central Unit and HEP sensor ~ 1 kg Low Power: Central Unit and HEP sensor ~ 1 Watt Modular: Easy integration of other sensor systems

5. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 5 The HEP Sensor System… …what was existing Jan 2005: ESA Workshop on Ionizing Particle Measurements in Space: Future Technology Priorities: High fidelity energetic particle telescopes (EPT…) Sub-kg general particle spectral monitors (GSEM) incl. miniaturized dose rate monitors Problems of existing Monitors: Poor separation of electrons, protons and ions Measurement of deposited energy only  Difficulties in data interpretations

6. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 6 The HEP Sensor System… …what do we need HEP sensor system of GSEM should provide: e/p separation of 1 in 10 -3 Measure incoming particle energy with good fidelity and multiple bins Data needs to be corrected for dead time, channel and particle cross-feed  Simplified data interpretation

7. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 7 The HEP Sensor System… …Revised Design Requirements by ESA Distinguish electron/proton/ion Measure incoming particle energy  Measure E and dE/dx Energy ranges: Electrons: 120 keV - 7 MeV Protons: 3 MeV - 300 MeV Ions:1 - 70 MeV/cm 2 /mg Viewing angle at least  20 o Sampling rate: 500 kEvents/s with dead time correction

8. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 8 The HEP Sensor System… …Design Approach Range Telescope with: Measured quantities: Range dE/dx in all layers Stack of silicon PIN diodes and absorber layers Size determined by rate about 2 cm diameter Full digital readout Active veto outside Passive shield around Veto Shielding Veto

9. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 9 The HEP Sensor System… …Geometry 6 layers of sensors: 1 st layer 2 sensors of 50  m and 300  m with coincidence Other layers 300  m Increasing absorber-thickness: 10  m (pinhole), 200  m (ring) 0.8 mm, 1.6 mm, 3.2 mm, 6.4 mm, 12.8 mm Protons will straggle to stop Electrons often have large angle scatters

10. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 10 The HEP Sensor System… …Geometry 10 electrons going through the detector Multiple scattering Photons produced Detector Sideview e-e- 

11. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 11 Radiation in Space… …expected maximum fluxes PROTONS ELECTRONS

12. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 12 Radiation in Space… …expected LET rates for 1 cm 2 sr, 1mm Al Helium: 5 Hz - 15/day Iron: 0.07 Hz - 2/month Iron shoulder 210 5 MeV/g/cm 2 0.014 Hz - 4/year Higher rates need much bigger surfaces p He Fe pHe Covered range

13. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 13 GEANT4 Simulation… …Geometry Full geometry implemented 6 mm Al-shield around active veto for low E particles Height of detector adjustable 2 cm

14. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 14 GEANT4 Simulation… …Setup 2 versions of simulation: ‘Old’ Simplified geometry,  20 o input, 200 kEvents, flat spectrum, ROOT-histograms Full geometry, full angle, 1 MEvents, ROOT-trees (available since mid september) Most plots still with ‘old’ simulation Detailed analysis with ‘new’ simulation currently ongoing (angular acc., veto- counters, power-law spectrum)

15. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 15 GEANT4 Simulation… …Particle separation Total E shown Protons very clean Protons Electrons

16. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 16 GEANT4 Simulation… …Proton binning < 80 MeV 5 bins by range in 1 st 5 layers (3-80 MeV) Excellent separation for range bins Basically no cross-feed between energies

17. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 17 GEANT4 Simulation… …Proton binning > 80 MeV High E bins by total dE/dx 4 bins from 80 to 300 MeV Good separation, easy unfolding of the small cross- feed Last bin above 300 MeV as veto

18. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 18 GEANT4 Simulation… …Electron binning 6 electron bins: 5 bins by range in 1 st 5 layers, as for protons Reasonable separation in E, unfolding needed Last bin as veto for E > 14 MeV

19. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 19 GEANT4 Simulation… …Electron/Proton separation Good separation between electrons and protons/ions Misidentification p  e: < 610 -5 at highest energy Misidentification e  p: 10 -3 (low E) 10 -2 (high E) Color = Energy bins High E Low E Electrons

20. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 20 GEANT4 Simulation… …New Plots (ongoing) Expected Angular Acceptance  20 o Crosscheck with simplified geometry show same behaviour dE/dx unchanged In sensor 1 No veto Full angle Preliminary

21. SPENVIS & GEANT4 Workshop, Leuven, October 2005, Page 21 Outlook & Conclusions Range telescope shows convincing performance from simulation Good e/p separation Spectra with reasonable binning Easy interpretation of proton spectra Simple unfolding for electrons needed Phase A finished, Phase B close to completion Fine tuning of simulation Building of prototype detector will start 2006 Sensor samples already in our hands, will be tested soon on probe station